Formula CarMaker - IPG Automotive GmbH

Formula CarMaker - IPG Automotive GmbH
Taking you to the next level
IPG Documentation
Formula CarMaker®
Tutorial 1.0
2
The information in this document is furnished for informational use only, may be revised
from time to time, and should not be construed as a commitment by IPG Automotive GmbH.
IPG Automotive GmbH assumes no responsibility or liability for any errors or inaccuracies
that may appear in this document.
This document contains proprietary and copyrighted information and may not be copied,
reproduced, translated, or reduced to any electronic medium without prior consent, in writing, from IPG Automotive GmbH.
© 1999 - 2016 by IPG Automotive GmbH – www.ipg.de
All rights reserved.
FailSafeTester, IPGCar, IPGControl, IPGDriver, IPGEngine, IPGGraph, IPGKinematics,
IPGLock, IPGMotorcycle, IPGMovie, IPGRoad, IPGRoaddata, IPGTire, IPGTrailer,
IPGTruck, RealtimeMaker, Xpack4 are trademarks of IPG Automotive GmbH.
CarMaker, TruckMaker, MotorcycleMaker, MESA VERDE are
registered trademarks of IPG Automotive GmbH.
All other product names are trademarks of their respective companies.
Formula CarMaker Tutorial
Version 2.3
Contents
3
Table of Contents
1
Installation
1.1
2
8
Installation and Licensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
CarMaker and IPGKinematics
9
2.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2
Brief description of the programs . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3
Getting started with IPG CarMaker. . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3.1 CarMaker TestRun. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3.2 IPGMovie. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3.3 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.3.4 IPGControl. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.4
Getting started with IPGKinematics . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.4.5 Simulation Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.4.6 Geometrical Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.7 IPGGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.4.8 Exporting results to CarMaker. . . . . . . . . . . . . . . . . . . . . . . . . 31
Formula CarMaker Tutorial
Version 2.3
Contents
3
Parametrization - Vehicle
4
32
3.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.2
Axis system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.3
Defining the axle characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.3.1 "General" tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.3.2 Springing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.3.3 Bushings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3.4 Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.3.5 Geometry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.4
Preparing a vehicle dataset in CarMaker . . . . . . . . . . . . . . . . . . . . . 48
3.4.1 Vehicle Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.2 Bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.4.3 Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.4.4 Suspensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.4.5 Steering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.4.6 Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.4.7 Brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.4.8 Powertrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.4.9 Aerodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
3.4.10Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.4.11Vehicle Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.4.12Misc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.5
Creating a tire dataset using IPGTire . . . . . . . . . . . . . . . . . . . . . . . . 71
3.5.1 Pacejka Magic Formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.5.2 IPGTire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.5.3 TameTire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.5.4 Tire Data Set Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
4
Parametrization - Electric Race Car
82
4.1
Formula Student Electric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.2
Electric Powertrain Model in CarMaker. . . . . . . . . . . . . . . . . . . . . . . 83
4.2.1 Drive Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
4.2.2 Driveline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.2.3 Control Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.2.4 Power Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Formula CarMaker Tutorial
Version 2.3
Contents
4.3
5
The "OpenXWD" Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
4.3.1 Powertrain based on "OpenXWD" model . . . . . . . . . . . . . . . . 91
4.3.2 General remarks to the Simulink models. . . . . . . . . . . . . . . . . 91
4.3.3 OpenXWD Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.3.4 Parameter File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
4.4
Adaption of the example models . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
4.4.1 User Defined Powertrain Control Models . . . . . . . . . . . . . . . . 96
4.4.2 Manipulating the OpenXWD example model. . . . . . . . . . . . . . 99
4.4.3 Driver Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5
Model Validation
102
5.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.2
Plausibility checks of axle models . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.2.1 Variation of camber and inclination vs. wheel travel . . . . . . . 103
5.2.2 Track change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.2.3 Toe change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.2.4 Steering angle/Steering ratio. . . . . . . . . . . . . . . . . . . . . . . . . 106
5.2.5 Turning track diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
5.2.6 Anti-dive and anti-squat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
5.3
Plausibility checks of the vehicle dataset . . . . . . . . . . . . . . . . . . . . 108
5.3.1 Center of gravity and moments of inertia. . . . . . . . . . . . . . . . 108
5.3.2 Comparability of IPGKinematics and CarMaker . . . . . . . . . . 108
5.3.3 Assignation of the spring length l0 at front and rear axle . . . 108
6
Simulation
6.1
111
Initial start-up of the model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.1.1 First simulation and common error messages. . . . . . . . . . . . 111
6.1.2 Driver adaption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
6.2
TestManager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
6.2.1 Variations and Variable kinds . . . . . . . . . . . . . . . . . . . . . . . . 114
6.2.2 Criteria and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
6.2.3 Example Test Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Formula CarMaker Tutorial
Version 2.3
Contents
7
Postprocessing
6
129
7.1
Compare results in IPGControl. . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
7.2
Export simulation results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
7.3
Print diagrams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
7.4
Postprocessing with Matlab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
8
Helpful suggestions
134
A
Bibliography
136
B
Data files
137
B.1Example of a TYDEX code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Formula CarMaker Tutorial
Version 2.3
7
Abstract
How to start? A question many Formula Student Teams must have asked themselves
before facing a new season - or even the before their first.
With the IPG Automotive GmbH as new team sponsor you receive two license files for
IPGKinematics and Formula CarMaker for free. The installation process runs without any
difficulties in most cases. But having made the first glances on the new programs many
don’t know how to get started. Questions emerge like "How does the whole thing work?",
"What program am I supposed to start with?" or "What are the benefits of using IPGKinematics and CarMaker in the development process of my Formula Student racing car?".
Fortunately the company IPG Automotive GmbH offers to all registered teams along with
their software further technical support like a User’s Guide, Manuals, Formula CarMaker
workshops, video tutorials, an interactive member area on the IPG website http://
www.ipg.de/ and the last but not the least email-support to answer any kind of questions
concerning CarMaker and IPGKinematics.
This document should also play another auxiliary role. It will show you step by step how to
integrate both tools IPGKinematics and CarMaker most efficiently into the designing and
optimization process of your Formula Student racing car to assure an outstanding performance in any competition your car participates in. But always remember, this document is
only an addition to the handbooks. The CarMaker User’s Guide and Reference Manual
available in the Help menu of the CarMaker main window should always be used besides
this document.
The general approach is explained based on several thesis and internship projects students
from different Formula SAE teams made at IPG.
Our current Formula CarMaker racing car model ("FS_RaceCar_5.1") is mainly based on a
Formula Student Combustion racing car from season 2011. The example car as well as the
showcase test runs are supposed to provide a basis for your simulation model. This document will guide you how to adapt the existing model to best reproduce your car so that you
can start simulating as soon as possible. Furthermore, it is dwelled on certain testing procedures and their analysis to validate the model and finally optimize your Formula Student
racing car.
Formula CarMaker Tutorial
Version 2.3
Installation
8
Installation and Licensing
Chapter 1
Installation
1.1
Installation and Licensing
To be able to install CarMaker on your PC you have to dispose of administrating rights.
After successfully requesting a Formula CarMaker license, you‘ll be send a ftp-link. Download the containing files. Extract the "CD-CarMakerOffice+IPGKinematics.zip"-file and execute the "ipg-install.exe".
You should choose "C:\IPG" as installation library. It is not compulsory but suggested as
otherwise some changes must be done in the data sets of IPGKinematics. Further information can be found on the IPG website as well as on the information paper which was downloaded together with the installation files. If this information is not sufficient please feel free
to contact the Formula CarMaker team under [email protected]
The license file
Although both tools, IPGKinematics and CarMaker, have been installed successfully, they
can’t be started as the license file is missing. There is only one license for both programs
and as a registered Formula Student team you get it for free. Each license is created directly
on some specific PC information and thus is bound to this very PC. To order a license file
for your computer please follow the instructions on the information paper received along
with the installation files.
Each file is valid until the end of the current season (October 31st). After expiry each team
can register once again to get a new license file.
The Cockpit Package
The ftp link you received also contains an installation package of our tool "Cockpit Package
standard". It is an interface to connect CarMaker with a game console such as a Logitech
or Thrustmaster steering wheel. Please find further information about this tool in the Cockpit
Package Reference Manual which is part of the zip package. To request a license for the
interface please contact the Formula CarMaker team.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
9
Introduction
Chapter 2
CarMaker and IPGKinematics
2.1
Introduction
Chapter 2 will give you a short overview of the general handling of the programs. At first
there is a description of Formula CarMaker’s structure and functionality. Following to that a
Formula CarMaker project is defined. After that an example shows how to build up and
interpret a Formula CarMaker TestRun. In this manner it will be made easier for the user to
get used to the program so that he/she won’t get problems in the handling of the program
while generating an own model later on.
This section is followed by another example that gives you an introduction to IPGKinematics.
Finally, the interaction of both tools is demonstrated by importing kinematic and compliance
characteristics which were generated using IPGKinematics to CarMaker.
Please bear in mind that you always have access to the "User’s Guide" and the "Reference
Manual" which contain plenty of information about the two programs. This document is only
supposed to be a supplement to these guidebooks. The reader will be reminded incessantly
through references and cross-references to use these manuals. Many of the emerging
questions and mistakes can be avoided and solved by the help of these documents.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
10
Brief description of the programs
2.2
Brief description of the programs
CarMaker
CarMaker is a tool to simulate the vehicle dynamics of fourwheeled cars. It’s one of IPG’s
products and it was designed for the simulation of passenger cars. By means of mathematical models a Virtual Vehicle Environment (VVE) is created. The VVE simulates vehicle,
driver and road including wind, obstacles, traffic signs etc. These make up all the parts
needed to evaluate a controller or to test the dynamics of a vehicle or a vehicle subsystem.
The slightly modified tool CarMaker/HIL offers with an identic functionality, database and
appliance the possibility to test real ECUs in a virtual vehicle environment (= hardware in
the loop).
CarMaker also has some other helpful IPG tools such as:
- IPGMovie to visualize the virtual vehicle environment
- IPGControl as analysis tool
- IPGDriver which complies a virtual, adaptive driver
- IPGInstruments to provide important information about the state of the car.
Controlling and parameterization is done via a GUI (= Graphic User Interface). The first step
using the GUI would be to edit all the parameter fields to define your model. Then you can
perform a simulation (i.e. perform loop calculations) so as to predict the behavior of the car
and check the results.
Please refer the "User’s Guide" and the "Reference Manual" in order to prevent problems
and questions.
IPGKinematics
Basically, IPGKinematics is a calculator that describes the movement of the wheels in
space (it describes its kinematics tables). It calculates the corresponding forces necessary
to trigger the movement and thus determines the complete kinematics, steering kinematics
and compliance of all types of suspensions. Its can be seen as a virtual axle kinematics test
bench.
For data processing and analysis there is a tool to generate diagrams and plot various
curves. Another option allows to edit the gained data so that it can be exported to several
vehicle simulation tools such as IPG CarMaker.
Controlling and parameterization is also performed via a graphic user interface.
Using IPGKinematics, at first you have to define all the parameters for the simulation control. Secondly enter all the values needed to parametrize your axle ("Input Data"). In a third
step perform a simulation to calculate the wheel positions and forces. Finally you can analyze and export the results.
In order to guard against problems and questions, please note that the manuals contain a
lot of information about the tool.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
11
Getting started with IPG CarMaker
2.3
Getting started with IPG CarMaker
Starting CarMaker using Windows
After installing CarMaker on your computer and having ordered the license file, the tool can
be started for the first time.
CarMaker always works within a project. In this project all the folders used by CarMaker are
stored according to a certain hierarchy which is the same for every project. Hence, CarMaker always knows where to find common files such as tire data, vehicle description and so
on. The data itself, of course, differs from project to project.
Thus, you have to choose a project folder after opening CarMaker, because you have to tell
the software in which project folder you would like to work in. Choose "File > Project Folder
> Select". For this tutorial you should use the FS_Generic project folder which you can
download along with the software installation packages.
Of course, you can also create new project directories with your own data, provided that the
structure of the directory remains the same. Therefore choose "File > Project Folder > Create/Update Folder". In the pop-up, window you can enter the path where the new folder
should be created. This new project folder contains the hierarchy needed by CarMaker to
find common files.
Figure 2.1: Selecting a Project Folder
Exercise
Open CarMaker and choose the FS_Generic_2017 folder which you have downloaded from
the closed member area of Formula CarMaker on our homepage.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
12
Getting started with IPG CarMaker
2.3.1
CarMaker TestRun
What is a CarMaker TestRun?
A CarMaker TestRun is a stored simulation configuration. Definitions of vehicle, tire, driver,
road and maneuver represent the input quantities which are all pre-saved as a test run definition. Once all of these five components are defined, a TestRun can be saved, edited and
reloaded later on.
Going ahead, two almost identical TestRuns will be generated, simulated, analyzed and
compared with each other. All parameters except the driver settings will remain the same.
Concerning the drivers a normal and an aggressive driver will be used. These Two
TestRuns will be called "FS_Competition_SkidPad_NormalDriver" and
"FS_Competition_SkidPad_AggressiveDriver".
For further information about TestRuns see the User’s Guide.
CarMaker Main Window
Once CarMaker is started the Main Window opens (see the illustration below). It’s the central platform where you can define and edit all input quantities. Going ahead, we are going
to call this window "GUI" which stands for Graphical User Interface.
Figure 2.2: The CarMaker main GUI
Vehicle Model
Instead of writing all parameters for all CarMaker subwindows we will load a pre-defined
model. In this chapter the "FS_RaceCar_5.1" vehicle data set will be used. This dataset
represents a common Formula Student racing car from season 2011.
Once you’ve loaded the file you see a pre-defined vehicle the "FS_RaceCar_5.1". To use a
different vehicle click on the "Select"-button and choose a new out of the given ones. In section 3.4 it is shown how to create your own vehicle model.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
13
Getting started with IPG CarMaker
Exercise
To load the pre-defined vehicle model mentioned above select "Car > Select >
Examples_FS" in the main GUI. Browse through the files and choose "FS_RaceCar_5.1".
Then, save your first TestRun as "FS_Competition_SkidPad_TUTO" by selecting "File >
Save as" in the main GUI.
Tire model
In this TestRun we will use a pre-defined tire dataset, in section 3.5 will explain how to create your own tire dataset using IPGTire.
In this example the tire "FS_195_50R13" will be chosen for the front tires and
"FS_205_50_R13" at the rear.
Exercise
Select the tire "FS_195_50R13" among the available models ("Tires > Select > Examples")
and hit the "OK"-button. By using the "Select"-button the chosen tire is set for all four wheels
together. To select different tires for front and rear wheels, click directly on the name of the
tire in the main GUI and make your choice (in this case "FS_205_50_R13" at the rear). By
rolling the mouse over the four tires shown in the tire selection area of the GUI an information box will appear describing, which tire (front right, front left, rear right, rear left) will be
modified.
Figure 2.3: Element-wise tire selection in the main GUI.
Road model
To open the road parameterization window: in the main GUI select "Parameters > Road".
Here, single road segments like straights, curves or clothoids can be inserted.
An example of how to build a circuit will be given by means of the Formula Student Skid Pad
event. This competition consists of two circular paths with a diameter to the central line of
18.25 m and a track width of 3 m. Each car starts in the middle of both the circles into the
right-hander. While passing the right handed circle twice, the second lap is timed. After the
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
14
Getting started with IPG CarMaker
second run, there is a change in direction and the driver turns into the left handed circle.
While passing it twice, again only the second lap is counted. After finishing the second run
the car leaves the course through the middle of both circles.
This competition aims at examining the maximum lateral acceleration your Formula Student
car can cope with. Knowing the average lap time t of both measured runs and the circuit’s
radius r the average lateral acceleration can be calculated:
2
2
2
F
v
4⋅π ⋅r
s
a y = ---- = ----- = ----------- = -------------------2
2
m
r
t ⋅r
t
(EQ 1)
Exercise
To create a Skid Pad model in CarMaker you have to insert six segments. The first is a 15
m long straight which stands for the entry. Afterwards add a right turn with a radius of 9.125
m. As this circle is passed twice in a row, you could choose 720 deg for "Angle". As we want
to install a light barrier, please choose 360 deg for a single segment and insert two right
turns. The same settings are edited for the following left turn. At the end there is a 25 m long
straight which represents the exit. As the track is completely flat, no slope or camber is
required. In the next Step, go to the IPGMovie Interface Tab and reduce the Natural Slope
Width to 0. Finally, you just have to enter the start coordinates, track width and margin width
as shown in the figure below to complete your Skid Pad test track.
Hint:
Check the road definition with the Bird’s Eye View and the 3D Preview. For the selection,
keep the mouse pressed on the button "Preview" in the top right corner of the dialog.
In the Road dialog under the tab "IPGMovie Interface" you can set the parameter "Natural
Slope > Width" to zero when you want a clear road surface at the overlapping parts.
Figure 2.4: The Skid Pad general segments and the Bird’s Eye View.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
15
Getting started with IPG CarMaker
Apart from single road segments additional features like obstacles, pylons, traffic signs,
wind markers or speed traps can be inserted. To show how to use these features, we will
try to generate a chronometry for the SkidPad event with regard to the FSAE rules. The first
full circle on the right is to establish the run. The second one will be timed. The same procedure applies to the left turns.
To integrate Bumpers/Markers along the road you can allocate them to the segment. Therefore you have to choose the segment you like to have the feature to be added in and select
"New Bumper/Marker". The changing GUI offers different kinds of features using the dropdown menu.
Also, you can allocate the features to every point on the whole road by adding it to the first
segment and defining a start offset. This can be necessary e.g. when you like to take time
measurements with equidistant spaces (independent from the length of the individual road
segments).
More information about these features are in the User’s Guide, section "Parameterization:
TestRun > IPGRoad > Adding Road Markers/Bumps".
Exercise
Create trigger points for the following segments:
Table 2.1: Trigger point values
Segment
Feature
No.
Kind
Start
Kind
Start
Mode
Id
2
360 deg Right
72.3
Trigger point
0.0
1
0
3
360 deg Left
129.7
Trigger point
0.0
3
1
4
360 deg Left
187.0
Trigger point
0.0
1
2
5
Straight
244.3
Trigger point
0.0
3
3
Figure 2.5: Adding Trigger points to the road by using Road Markers.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
16
Getting started with IPG CarMaker
Maneuver
You can open the maneuver window in the main GUI by clicking on "Parameters > Maneuver".
Figure 2.6: The CarMaker Maneuver window.
You can define several successive maneuvers along the track. You specify the duration of
a maneuver in the box called "Specification of Maneuver". There are two usual ways to
define the duration: time or length. If both the parameters are specified the simulation stops
when the first constraint is fulfilled. If only one field is initialized the second one will be disregarded.
The third way to stop a simulation is via a user defined end condition. Therefore you have
to rightclick in the field "End Condition". Now you have access to all data directory variables
of CarMaker. Once you select one, you can tie it with a logical operator to create a condition.
If this condition becomes true, the maneuver step is finished.
At the field "Global Settings / Preparation" the start values for the maneuver can be defined.
To know more about the maneuver definition, please read the User’s Guide, section
"Parameterization: TestRun > Maneuver".
At the bottom the "Minimaneuver Command Language" enables to specify several maneuver commands such as maneuver jumps, creation of new quantities and variables, calculations etc. To learn more about it, read the User’s Guide, appendix "Realtime Expressions".
The maneuver parameterization is divided in two parts: "Longitudinal Dynamics" and "Lateral Dynamics", which respectively controls the (throttle, brake, clutch) pedals and the
steering wheel.
Exercise
In this TestRun we will use a duration of 100 sec., so that the Skid Pad circuit can be completed in any case. For both lateral and longitudinal dynamics the IPGDriver, which will be
configurated in the next step, is used.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
17
Getting started with IPG CarMaker
Driver model
Open the IPG Driver window in the main GUI by clicking: "Parameters > Driver".
You have two different driver configurations to choose from. The first option is the "User
parameterized Driver" which can be customized by a lot of parameters. In the tab "Standard
Parameters" under "General" the "Cruising Speed" is the speed that the driver will try to
reach. Here you can also find a g-g diagram in "Accelerations", where you can specify the
maximal allowed (purely longitudinal and lateral, or combined) accelerations. If you don’t
know which values to enter, right click anywhere in the driver parameterization window and
select the desired characteristic from "defensive", "normal" or "aggressive". This type of
driver simulates the behavior of a real driver, who can steer, accelerate, brake, slow down,
shift gears, cut corners, adapt its driving according to the track etc..
Figure 2.7: Driver mode selection in CarMaker.
The second type of driver to choose is the "Racing Driver". He drives the car up to its physical limits and thus attains maximum power and speed. However, it is essential that the driver knows the car’s limits. In reality this process takes a lot of time and testing kilometers.
Basically, in the virtual environment it is the same. The driver determines the limits through
specific driving maneuvers. This procedure is called "Driver Adaption" in CarMaker and can
be started via "Simulation > Driver Adaption > Basic Knowledge".
The Racing Driver however, should only be used on race circuits. It is optimized to find the
fastest laptime on a closed race track. So it is the right choice for the autocross and endurance events. For the other competitions Acceleration and SkidPad, the User Parameterized
Driver is the better choice. This driver can be tuned for the special task, which means it can
be focused on pure longitudinal dynamics (for the Acceleration event) or lateral dynamics
(SkidPad). The focus is set by defining a very high max. long./lat. acceleration. It can be
even an unrealistically high value such as 50 m/s2 to find the limits of the car. Check the
driver settings in our FS_Example TestRuns to find the proper driver selection for each
event.
Note: with a right-click in the Driver dialog, you have access to predefined driver characteristics, such as an normal or aggressive driver. To show the difference between the driver
characteristics, two TestRuns will be performed which only differ in the choice of the selected type of driver.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
18
Getting started with IPG CarMaker
Exercise
Complete your first TestRun by selecting the "User parameterized Driver". Right click anywhere in the "Standard Parameters" tab and choose "normal" in the appearing menu. In
section "Declutching / Gear Shifting" increase the minimal engine speed to 2.800 rpm and
the maximum to 15.000 rpm. Then save the TestRun as
"FS_Competition_SkidPad_NormalDriver".
In the second try, right click and select the "aggressive" driver. Change, the shifting limits
again to the same engine speeds as explained above. Change the "Corner Cutting Coefficient" to 0.5, so that the driver remains on the SkidPad track. After finishing, save this
TestRun as "FS_Competition_SkidPad_AggressiveDriver" so that we can compare both
results later on.
Starting a simulation
After finishing the definition of the TestRun we can start to simulate and analyze the results.
During a CarMaker simulation some hundred variables are calculated which are also available at the analysis. But if you save the results of your simulation, all values are not stored
due to constraint of memory capacity. Only the most important respectively the selected
ones are saved, but you can change the pre-defined settings and decide on your own which
quantities are important and which are not. The stored values can be checked and changed
under "Application > Output Quantities".
Exercise
To be able to compare the lateral acceleration and the velocity of the car obtained by the
two different drivers, please ensure that the lateral acceleration "Car.ay" and the velocity
"Car.v" are activated in the "Storage of Results" dialog.
Figure 2.8: CarMaker Output Quantities.
Please also have a look at the expression "Vhcl.sRoad" for further analysis.
To face the results of the light barrier (trigger point) activate the following quantities:
•
DM.TriggerPoint.Id
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
19
Getting started with IPG CarMaker
•
DM.TriggerPoint.Time
In this dialog you can also save or load your settings for the Output Quantities, not necessarily by the usage of one file. Keep in mind that these settings will be applied to the whole
project folder.
Before starting the simulation you can check some more settings:
Speed of simulation
The first one is the speed of simulation (see the simulation selection area in the main GUI).
Figure 2.9: Setting the speed of simulation in the main GUI.
In general, you can choose the speed of simulation which you want since it is a purely computational simulation (i.e. the computer performs the calculations at any speed since there
is no real component in the simulation loop). You can also change this speed during the simulation. Note that this speed depends on the power of processor and graphic card of your
system (if IPGMovie is running, it may dramatically slow down calculations). The box also
displays the time from the start and the distance covered.
Storage of results
Figure 2.10: Storage of Results in the main GUI.
With regard to the "Storage of Results" parameter, you should always choose "collect only".
Indeed, with this option results are only saved in a buffer, a temporary memory (and you
have the option to save them to a file at the end if you need the results later again). If you
use another option the results will be directly saved in a file and concerning the numerous
simulations you will perform, the size of the folder containing the results files will become
enormous!
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
20
Getting started with IPG CarMaker
Model Check
The last step before starting a simulation is to check the equilibrium state of the car using
the "Model Parameter Check" (Model Check). This utility is quite helpful to see, if the changes made have the desired effect on your car. Thereto open "Simulation > Model Check".
Select a field of interest and then click "Generate Diagrams".
Figure 2.11: Results of simulated parallel compression kinematics in the Model Check.
Once all options are set you can supervise the simulation with three tools: IPGInstruments,
IPGMovie and IPGControl; you can open these tools via the "File" menu of the main GUI.
A revised version of IPGInstruments in terms of FSAE named "Instruments_FS" is available
in the selection, too.
You start a simulation by clicking "Start" in the main GUI.
2.3.2
IPGMovie
Either during a simulation or afterwards, you can change the view direction of the camera
(activate IPGMovie window). Left-click and keep the pressure on the button, then move
slowly the pointer to the left or to the right. Then do the same upwards and downwards to
change the view direction. Middle-click and keep the pressure on the button, then move
slowly the pointer upwards and downwards to zoom on the car.
In IPGMovie all the changes to the road are visible: the differences in friction coefficient (different colors), road signs and, of course, the route itself. If your graphic card is powerful
enough you can export the movie as an .avi, .mpg or .wmv file (in IPGMovie window select
"File > Export Video/Images"). However, you need to install a video codec such as DivX or
XVid first.
Further, using the "Overlay" option in IPGMovie under "View > Overlay Left / Right" you can
add additional displays to the IPGMovie window. In the top left/right corner you can get a
route view, a speedometer, a gg-diagram, the driver’s steering wheel movments and much
more.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
21
Getting started with IPG CarMaker
Another interesting feature of IPGMovie is the possibility to compare two cars on the same
movie. Once your primary simulation is finished you have to select in the IPGMovie window:
"Scene > Reference Vehicle > Copy current motion data". Then activate "Primary & Reference Vehicle" in the "Scene" menu. After making some changes the simulation can be started again and now you will see two cars in the window: the former and the current simulation.
Figure 2.12: IPGMovie with Reference Vehicle and Overlays.
Exercise
Open the first TestRun "FS_RaceCar_SkidPad_NormalDriver". Set the speed of simulation
to "realtime" and "collect only" the results. Open Instruments, IPGMovie and IPGControl
from the "File" menu of the CarMaker main GUI. Once the simulation is complete save the
results via hitting "Save" in the "Storage of Results" box of the CarMaker main GUI.
In IPGMovie select "Scene > Reference Vehicle > Copy current Motion Data" and then
"Scene > Primary & Reference Vehicle".
Now open the second TestRun "FS_RaceCar_SkidPad_AggressiveDriver" which was prepared before and start another simulation with the same "Storage of Results" settings as
above. When the simulation is running you will see two cars in the IPG_Movie window: the
actual running the aggressive driver and the former TestRun with the normal driver. Don’t
forget to save the results.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
22
Getting started with IPG CarMaker
2.3.3
Instruments
Another feature to observe the simulation is the "Instruments" window. You can choose
between the ordinary one and a special Formula Student version. Both can be opened in
the main GUI vie "File > Instruments".
In both the cases the "Instruments" window contains a speed indicator, a tachometer, four
histograms indicating the actual steering angle, clutch, brake and gas pedal position and
another graph showing the gear being actually engaged. After opening the Instruments FS
version, at the left end of the window, sector times and lap times are recorded once you use
the Racing Driver and a closed circuit.
Figure 2.13: The "Instruments FS" window.
Having finished both simulations and saved the results, we can now start to analyze both
the TestRuns.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
23
Getting started with IPG CarMaker
2.3.4
IPGControl
IPGControl is the CarMaker analysis tool. Various simulation result files can be loaded consecutively to plot and compare signals. Multiple diagrams can be generated and shown in
one window - one below the other.
Figure 2.14: IPGControl windows
Exercise
Open "File > IPGControl". In the "IPGControl Window" you already find the TestRun you just
have performed. To compare both driver types you must load the results of the former
TestRun ("File > Load File > SimOutput > NameOfYourPC > Date > NameOfYourTestRunTime.erg"). Make sure that now both result files "Normal Driver" and "Aggressive Driver" are
shown in the "Data Sets" area.
Activate the "Normal Driver" TestRun results by clicking on it in the "Data Sets" section. In
the "Quantities" area below choose "Car.ay" for the lateral acceleration and "Car.v" for the
car velocity by left-clicking on the abbreviations. The selected quantities turn yellow. As reference variable, choose the distance by right-clicking on "Vhcl.sRoad". It turns red to indicate its references variable status.
To create a second diagram in the same window, click on "Display > Add Diagram". Repeat
the procedure to create a plot of the aggressive driver’s lateral acceleration and velocity.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
24
Getting started with IPG CarMaker
Figure 2.15: Comparison between User parameterized Driver and Racing Driver.
A difference between acceleration and velocity of both drivers is obvious. You can see that
a "better driver" achieves better results than a poorer one under the same circumstances.
Another important thing to know about IPGControl is how to export diagrams. For the static
events in the course of the Formula Student competition, it can be quite useful to show the
judges printed diagram sheets or to integrate some plots in your presentations. For that you
needn’t make a snapshot of the screen to save a diagram in an extra file! There is a more
convenient and storage saving way to create the file directly out of the source. All you have
to do is push the right mouse button anywhere in the diagram box. In the appearing menu,
select the option "Print". Now, another window opens. Here you can choose the name of a
installed printer.
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
25
Getting started with IPG CarMaker
Exercise
Try to generate a comparison of section times driven by Racing Driver and the User parameterized Driver. The steps are the same as mentioned above. For the quantities choose
DM.TriggerPoint.Id and DM.TriggerPoint.Time.
Figure 2.16: Comparison of section time
To fit the results, right click with your mouse anywhere in the Data Control window and
choose "Total Fit". You can read the values after you switched on "Pause" and selected the
variable.
If you like to export the simulated data, just right click anywhere in the data window and
choose "Export To File". In the rising window you have the possibility to choose the file format and to name the file.
An explanation of all abbreviations is given in the Reference Manual, section "User Accessible Quantities".
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
26
Getting started with IPGKinematics
2.4
Getting started with IPGKinematics
Open IPGKinematics
As IPGKinematics is a stand alone application, it can be opened using the Windows start
menu. Alternatively, it can be started from the "File" menu of the CarMaker main GUI.
It is advisable to create a new directory before starting a new project. It should contain the
following folders: <NameOfYourProject>\Kinematics and
<NameOfYourProject>\Kinematics\Sequences.
Exercise
Create a new directory called "TUTO_KIN" in your Windows Explorer. In this directory create a folder named "Kinematics" and in this folder create another named "Sequences".
Then, open IPGKinematics as described above.
Configuration of a double wishbone axle
Before starting with a new model you have to select the type of axle you want to model. As
Formula Student cars usually use a double wishbone axle this type will be chosen. The
parameterization of the axle is done in the submenu "Vehicle Data". Here all general specifications for kinematics, buffers, masses and geometrics are made.
This example aims at giving a short insight in the several submenus and the analysis tool.
The single parameters will be discussed more intensively in section 3.3.
Figure 2.17: Simulation models in IPGKinematics
Exercise
To open a new model, select in the main GUI: "File > New Model > Double Wishbone Front/Rear-Axle". Save the model in the created folder "TUTO_KIN > Kinematics" of the last exercise named "TUTO_KIN".
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
27
Getting started with IPGKinematics
2.4.5
Simulation Control
Open the "Simulation Control" window in the menu "Edit" in the main GUI or by clicking on
the dedicated button.
Figure 2.18: The Simulation Control window.
General
In the General tab you should select "Forces On" in the "Kinematics" area. "Forces Off"
means that there are neither inertial nor spring forces, so it’s pure kinematics without any
effort.
In "Storage of Tables" the control parameters for selecting the control print output for the
calculated value tables are set. "Off" means there’s no output of tables to file. Selecting "On"
all tables are put out to file and with "Log" all tables are put out to file and on screen.
The result files required for the graphical output are stored when selecting "On" in the "Storage of Results" section. To export the results to CarMaker you must choose one of the "CarMaker Interface" options. Whereas "CarMaker Interface (1)" provides linear compliance,
"CarMaker Interface (2)" uses a non-linear compliance model. However, this second option
increases the simulation duration. But at the same time the results don’t improve much, as
Formula Student cars usually don’t use any buffers. So, you should prefer the option "CarMaker Interface (1)". However, this option should only be chosen once your axle model
works sufficiently. Otherwise, at each test simulation the whole compliance for the use in
CarMaker is calculated additionally which increases the simulation duration needlessly.
Exercise
Choose the following settings:
"Forces On" in the "Kinematics" selection area,
"Log" for "Storage of Tables" and
"CarMaker Interface (1)" for "Storage of Results".
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
28
Getting started with IPGKinematics
Kinematics
Next is the "Kinematics" tab. This tab defines the protocol according to which the movements of the wheels are calculated.
"Parallel Kinematics On" means that both wheels of an axle will move in the same direction
on compression. "Reciprocal Kinematics" stands accordingly for wheels which travel in
opposite directions. To get to know the meaning of the different choices, please have a look
at the Reference Manual, Chapter 2.2.
"Steering Kinematics" is only necessary for the front axle if you don’t use a steered rear. It
simulates a rack-and-pinion steering which steers the front wheels correspondingly.
Choose "On (2)" as "On (1)" does not consider the interaction of the steering and the reciprocal wheels travel. "Steering Forces" is used in certain situations such as a tire hitting a
pavement.
The maximal values for "Compression" and "Distance Steering Rack" should be kept small
to not increase the simulation duration needlessly. That means, they should lie only insignificantly over the values possible in your car.
Figure 2.19: The Simulation Control Kinematics tab.
Compliance and MixedForce
The last two tabs are used to apply external forces to the wheels in longitudinal and lateral
direction. In case you are interested in the stresses of the single suspension components
for FEM analysis, these options can be activated. For pure kinematics, external forces are
deactivated which is why we leave this option turned off. Further information can be found
in the IPGKinematics Reference Manual.
Exercise
Put "Parallel Kinematics - On" and choose for "Steering Kinematics" as well as "Reciprocal
Kinematics" the mode "On (2)". Set the compression values to +/- 30 mm with "Stepsize" =
5. Leave the default values for the "Distance Steering Rack". In the "Compliance" and
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
29
Getting started with IPGKinematics
"MixedForce" tabs turn everything "Off". Then save the model in the "TUTO_KIN/Kinematics" folder created earlier. Beware that you choose "Input Data (.kin)" in the filter selection
area.
2.4.6
Geometrical Control
Before starting the simulation you should check your inputs. For geometrical data there is
the "Geometrical Control" which gives an overview of all the positions of the points entered.
You find it in the menu "Analyse > Geometrical Control" or use the corresponding icon.
Figure 2.20: The Geometrical Control Window.
Exercise
We will define the geometrical settings in the following chapter. Nonetheless as a trial you
can check the pre-defined geometry. Follow the path described above.
When everything is ready push the "Start" button.
According to the "Simulation Control" parameters you can see several arrays of calculations
being performed. The calculation process can take quite a while, depending on your input
data. Once the simulation is finished (the "Start" button turns green) you should save the
results straight away. Hit "File > Save" and overwrite the existing file to save your model with
the output data of the simulation. The saving generates numerous files depending on the
"Simulation Control" parameters.
Exercise
Perform a simulation and save the results as "TUTO_KIN".
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
30
Getting started with IPGKinematics
2.4.7
IPGGraph
The graphical analysis is based on the created .erg files and the tool IPGGraph. It lets you
plot any kind of diagram containing the calculated values. Open IPGGraph by clicking in the
main GUI "Analyse > Graphical Analysis" or by hitting the corresponding icon.
Figure 2.21: Graphical analysis in IPGKinematics.
In the "Control" tab you can load the results you want to analyse in the field "Choose
Results". It will be usually NameOfYourResults_parallel.erg for the parallel compression
part.
Now let us see what a "Sequence" is. It is a predefined diagram layout that will load pre-set
diagram parameters for different result files.
In the "Legend" and "Text" tabs you can adapt the appearance and number of the created
plots and add headings or comments. In the "Diagrams" tab you can define which parameters you’d like to plot. In the upper field you can choose a reference variable and in the lower
field one or more corresponding signals. The option "X On/Off" lets you leave out a particular diagram. Hitting the "X-Y =>Y-X" button the X and Y axis are inverted.
Exercise
Open IPGGraph. Check that the "Path to Results" and "Path to Sequences" lead to your
project files created earlier (TUTO_KIN/Kinematics and TUTO_KIN/Kinematics/Sequences). If not, edit the correct path in the "Settings" tab.
In the "Control" tab load the file "TUTO_KIN_parallel.erg". Do not define any sequences
right now. Parameterize the options in "Layout" and "Text" as you wish. In the "Diagram" tab
choose quantities for X and Y axis as you wish (e.g. WheelTravel.Left to ToeAngle.Left).
Formula CarMaker Tutorial
Version 2.3
CarMaker and IPGKinematics
31
Getting started with IPGKinematics
Once all settings are done you are ready to plot your diagram. For this, click "File -> Print"
or the corresponding button.
If there are several pages use the arrows on your keyboard to view them.
Once the diagrams are displayed you can print them either with a printer or to a file (.ps or
.pdf format): click on "File -> Print".
To save the layout of your diagrams generate a sequence hitting the "Save" button on the
"Control" tab in the "Choose Sequence" area and give it a suitable name. When you perform
another simulation you can carry over the diagram layout settings by selecting this
sequence.
2.4.8
Exporting results to CarMaker
As explained before, to export results to CarMaker you have to choose a special option: In
"Simulation Control > Global > Storage of Results" select in the pulldown menu the option
"CarMaker Interface (1)". With this option among of the numerous data files generated by
the simulation, one is called NameOfResults_front.skc (for a front axle) or
NameOfResults_rear.skc (for a rear axle). To export the IPGKinematics results to CarMaker
you have to copy this file and paste it to the "Data\Chassis" folder of your CarMaker project
directory, for instance: "FS_Generic_2017\Data\Chassis".
We will see how to use this file in the next chapter.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
32
Introduction
Chapter 3
Parametrization - Vehicle
3.1
Introduction
To improve the dynamics and performance of a car many time- and cost-consuming test
runs are necessary. Vehicle simulation enables the user to do a bulk of these test runs in a
virtual vehicle environment on his / her PC which saves a lot of time and money. However,
such an economization is only attainable if the results of the simulation and those of the real
car fit together as well as possible. For this reason it is essential to achieve a very high
degree of affinity between the virtual model of the vehicle and the vehicle itself. According
to this claim the parametrization of the vehicle has to be implemented carefully. After finishing a first concept it has to be validated by means of test runs and measurements which is
a complex and iterative process.
The following chapter shows an approach how to parametrize a model most efficiently.
Moreover the parameters will be explained in detail and a few examples will be given how
to determine these values.
As the beginning of the development of every vehicle is the suspension, the models for front
and rear axle will be build up first.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
33
Axis system
3.2
Axis system
In the beginning of the development process of every car there is a choice of the axis system. In IPGKinematics two different options are available:
•
Axis system in accordance to DIN 70000:
The X-axis is defined in the forward direction of travel with the Y-axis to the left and the
Z-axis up.
Figure 3.1: Axis system in accordance to DIN 70000. [KIN07]
•
Axis system frequently used in the automobile industry:
The X-axis is orientated opposite to the direction of travel, towards the back, with the Yaxis to the right and the Z-axis up.
Figure 3.2: Axis system used in the automobile industry. [KIN07]
In IPGKinematics both axis systems are available. But this applies only for the data input
as for all calculations the data is translated into the axis system according to DIN 70000.
The output of the results refers to the DIN 70000 axis system, too. To avoid interpreting the
results in the wrong axis system it is recommendable to work right from the start with DIN
70000. Another advantage is that you can use this axis system in CarMaker later on. CarMaker is based exclusively on this axle system.
It is left to the user where he wants the origin to be placed. The only crucial thing about it is
that all of the input data must refer to the same origin. However, you shouldn’t choose the
center of gravity as origin. The exact location of the center of gravity is mostly unknown and
thus the results are falsified. It also makes sense to use the same origin for both tools,
IPGKinematics and CarMaker, so delays needn’t be considered later on. Furthermore, it is
important to place the origin in the Y - center of the vehicle as the geometrics input is only
done for the left half of the axle and the right side is mirrored automatically by the program.
Due to the reasons mentioned above the following convention applies to both IPGKinematics and CarMaker in the course of this document:
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
34
Axis system
Axis system: DIN 70000
Origin in X direction: 500 mm behind the rear axle
Origin in Y direction: in the center of the vehicle
Origin in Z direction: on the road surface
Figure 3.3: Axis system used in the following. [KIN07]
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
35
Defining the axle characteristics
3.3
Defining the axle characteristics
Input data
Open the input data panel in the menu "Edit > Vehicle Data". In the various tabs appearing
you have to set the general terms of the car, define your spring rates, bushings and the
masses of several components and their positions.
Figure 3.4: The Input Data General tab.
3.3.1
"General" tab
Axle
At first you have to declare if you consider a front axle or a rear axle. This request is mainly
focused on clarifying if the contemplated axle is steered or not. Moreover this request
serves to determine the position of the pitching pole. Note: If you choose “Rear Axle” no
steering kinematics will be calculated even if this was set in the simulation control.
Brake Force Ratio
In this field the braking force ratio of the considered axis is defined. 0% means for example
that the axle you’re modeling receives no brake power. This information is required for calculations of the braking torque compensation angle and anti-dive.
Driving Torque Ratio
Here the driving torque ratio of the axle is defined. 0% means that the axle is not powered
and 100% means that it is the only powered axle. It is necessary to enable anti-squat and
starting torque compensation angle calculations.
Model configuration (1)
In the case of a Formula Student racing car you should tick "Chassis Subframe off" since
there is only a chassis without any subframe supporting the engine or lower suspension
components.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
36
Defining the axle characteristics
Tires
This point is to define the vertical stiffness of the tire in [N/mm]. As the tire is modeled as a
linear spring, a tire spring coefficient must be entered.
This spring coefficient is a function of:
- the tire pressure
- the tire design
- the tire tread
- the tire’s height to width ratio
- the driving speed
- the rolling characteristics of the tire.
The spring coefficient can be determined by a simple static test. All you need is a spring
balance and two plain plates. The tire is clamped between the two plates and put on the
spring balance. Then you apply a defined force FR. Through measuring the tire deflection
∆s the spring coefficient can be determined as follows:
F
c 1 = -----R∆s
(EQ 2)
∆s
∆s
Figure 3.5: Measuring the tire deflection. [Rei82]
If you are a member of the Tire Test Consortium you are in charge of detailed spring rate
data of your tires. For this information see the FromCalspan.zip archive from your RoundX
tire testing directory in the official TTC forum. The archive contains a spreadsheet titled
SummaryTables.xls. There you will find measured data of cornering stiffness as well as the
vertical stiffness as a function of inclination angle, tire pressure and vertical load.
If you don’t have reasonable values available there is another possibility to get an approximation. For this you need the tire’s diameter D, static radius rstat, load in accordance with
the actual tire pressure FR and a correction factor kB for the tire design, tread and velocity.
If these values are available, a good approximation for the spring coefficient can be found
according to:
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
37
Defining the axle characteristics
FR
c 1 = k B ⋅ ---------------------------D ⁄ 2 – r stat
(EQ 3)
Vehicle
In this area the height of the vehicle’s center of gravity and its wheelbase must be entered.
The wheelbase is needed to calculate the turning track diameter and the turning circle. The
height of the center of gravity is crucial to compute the lever of the roll axis. The section
3.4.1 explains how to determine the center of gravity on your car.
Design position
Here the constructive wheel toe angle and wheel camber angle have to be defined. The
design position is the position of the car with only the axle load on it. This accords to a wheel
travel of 0 mm. Thus, it must be kept in mind if the weight of the driver was included in the
design position or not. If not, attention must be paid to various settings such as location of
the center of gravity, camber and toe angle etc. All of them have to be measured or calculated without the driver’s weight.
Model configuration (2)
It offers the possibility to support the rack-and-pinion steering elastically. Concerning Formula Student racing cars this isn’t commonly used.
Exercise
Choose a rear axle configuration.
Set the "Tire Rate" to 200 N/mm,
the "Height Vehicle Center of Gravity" to 300 mm,
the "Wheelbase" to 1600 mm,
the "Wheel Toe Angle" to 0 min,
the "Wheel Camber Angle" to -3 deg,
the "Chassis Subframe" to off,
the "Driving Torque Ratio" to 100% and the "Brake Force Ratio" to 30%.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
38
Defining the axle characteristics
3.3.2
Springing
Figure 3.6: The Springing tab.
Spring Fixing
It defines which part the spring is fastened at. It is assumed that the "Spring Fixing" is the
one on the suspension side. The option "None" is chosen in case of a Pull-/Pushrod.
Stabilizer Fixing
In IPGKinematics you have the possibility to mount the stabilizer fixing to the Lower Wishbone, Wheel Carrier or the Pull-/Pushrod. If you have Anti-Roll-Bars which are attached to
the rocker, you use the option "Pull-/Pushrod". By using that option, IPGKinematics will consider a T-Stabilizer, otherwise an U-Stabilizer is used.
To properly parameterize your stabilizer in IPGKinematics you can use the option "Pull-/
Pushrod" and if you do not have a T-Stabilizer in your car, calculate the stiffness of the TStabilizer that matches the configuration of your car.
The second possibility is to convert whatever stabilizer you have into an U-bar. You should
use wheel carrier as stabilizer fixing due to the motion ratio from wheel travel to connection
point travel of 1. This method should work well if in reality you are using a constant motion
ratio, too.
There is a variety of possibilities to design a stabilizer template, in the following there will be
given an examplary suggestion:
1. Choose your wheel center as connection point for the stabilizer link to the wheel.
2. The connection point of stabilizer link and U-bar should be placed 100mm vertically to
the former point.
3. The lever arm of U-bar should be located 200mm horizontally in x to stabilizer mounting
point on the chassis.
This stabilizer parametrization will work properly in IPGKinematics as long as you use an
adapted stiffness, too, so that the whole substituted component has the same properties
like the real one.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
39
Defining the axle characteristics
Parameter Stabilizer
To parameterize the stabilizer template you need to calculate the total stiffness cs of the real
stabilizer. In case of an U-bar this dependents on the linearized torsional stiffness of the bar
cBa and the linearized bending stiffness cBl of the lever arms also called blades. This linear
total stiffness is transferred into the rolling stiffness of the front-/rear axle cRo,s. Recalculating with the motion ratio and track of the axle, you get the torsional stiffness of the stabilizer
template cs,θ, which is to be entered in IPGKinematics.
Fs
Fs
hBl
bBl
lBl
a
dBa,o
Fs
α
lBa
Figure 3.7: Geometrical notations for the calculation of the substituted stabilizer stiffness
In order to calculate the linearized torsional stiffness of the bar cBa you need to calculate
the torsional rigidity of the cross section Ip,Ba, with dBa,o as outer diameter and dBa,i as inner
diameter.
4
4
π ⋅ ( d Ba ,o – d Ba ,i )
I p, Ba = --------------------------------------32
(EQ 4)
With the stabilizer bar’s shear modulus G, the torsional rigidity of the cross section Ip,Ba, the
length of the lever arm a (with forces acting at a), and the length of the bar lBa, you get cBa.
G ⋅ I p, Ba
c Ba = ------------------2
a ⋅ l Ba
(EQ 5)
In order to calculate the blades’ stiffness in bending you need to calculate the cross sections’ rigidity in bending. Many teams use tunable blades which means, the cross section
on which the forces are acting on, changes. To take that into account you have to calculate
the rigidity of the blade in 0deg and in 90deg position. Through (EQ 8) you get the combined
cross sections rigidity for any bending angle αBl.
3
l Bl ,0°
b Bl ⋅ h Bl
= -----------------12
(EQ 6)
3
b Bl ⋅ h Bl
l Bl ,90° = -----------------12
α Bl ⋅ l Bl ,0° α Bl ⋅ l Bl ,90°
l Bl = l Bl ,0° – ----------------------- + -------------------------90°
90°
(EQ 7)
(EQ 8)
In order to calculate the bending stiffness of the blade you need the E modulus of the blade
material and the springing length of the blade lBl.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
40
Defining the axle characteristics
3 ⋅ E ⋅ I Bl
c Bl = --------------------3
2 ⋅ l Bl
(EQ 9)
By adding up the linearized torsional stiffness of the bar and the stiffness of the blade you
get the total stiffness of the real stabilizer cs for a force acting at the end of one blade.
c Ba ⋅ c Bl
c s = ------------------c Ba + c Bl
(EQ 10)
To transfer this overall stiffness of the real stabilizer into the overall stiffness of the template
U-bar the roll stiffness of the axle, the stabilizer is associated with, has to be calculated. s/
sf is the motion ratio of wheel travel s and stabilizer blade-end travel sf. b is the track width
of the axle.
cs
π
2
c Ro ,s = -----------------2- ⋅ b ⋅ ----------180°
(s ⁄ s f )
(EQ 11)
Through (EQ 12) it is possible to calculate the linearized stiffness of the template U-bar
cs,x. This value is needed in the parametrization of the stabilizer in CarMaker. Right now it
is only needed to calculate the torsional stiffness in (EQ 13) with a’ =200 mm as the blade
length of the template U-bar.
The value of cs,θ has to be entered as the torsional spring rate in IPGKinematics among
"Parameters Stabilizer Bar".
c Ro ,s 180°
c s ,x = -----------2- ⋅ ----------π
2⋅b
(EQ 12)
π
2
c s ,Θ = c s ,x ⋅ a′ ⋅ ----------180°
(EQ 13)
Spring/Parameters Spring
There are two possibilities to parametrize the spring: linear and non-linear characteristics.
For a linear progression the only needed value is the spring rate. It can be determined by a
simple tension test. With this test, the spring rate results from the quotient of applied force
∆F and deflection ∆s:
m1 ⋅ g
∆F
c = ------- = -------------∆s
∆s
(EQ 14)
A non-linear spring rate should only be selected if the spring rate used is truly non-linear!
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
41
Defining the axle characteristics
Parameter Pull-/Pushrod
By this parameter (also called spring rate) the elastic deflection of the Pull-/Pushrod is taken
into account. Therefore the Pull-/Pushrod is seen as a virtual spring. Accordingly the unit is
N/mm like in the section "Parametrization Spring". By knowing the material and the geometrics of the Pull-/Pushrod you can assume that the stresses lie within the elastic region and
thus apply Hooke’s law. Requested is the force triggering a deflection of 1mm of the Pull-/
Pushrod:
σ
σ
E⋅ε
E ⋅ ∆l
E ⋅ 1mm
F = ---- = ------------ = ------------ = -------------------------- = -------------------------2
2
2
2
A
π⋅r
π⋅r
( π ⋅ r ) ⋅ l0
( π ⋅ r ) ⋅ l0
(EQ 15)
For a radius of r = 20 mm, a length of l = 430 mm and an E modulus of E = 70 GPa (Aluminum 7075) a force of F = 55 kN is required. Hence, this Pull-/Pushrod would have a spring
rate of 55 kN/mm.
However, in a Formula Student racing car such high forces will never be applied on a Pull/Pushrod. Thus, you can assume that a Pull-/Pushrod won’t be deformed elastically in a
Formula Student car. To achieve this with IPGKinematics you needn’t put such high values
for the spring rate. At the same time this would increase the simulation duration needlessly.
Using an exact spring characteristic as explained in case of the axle spring, better results
won’t be achieved. Moreover there is the danger to spoil the Pull-/Pushrod during the tension test through a ductile deflection.
Parameter 3rd Spring Stabi Torsion Bar
With this option you can add a 3rd spring to your axle, which is actuated due to parallel
bump of the left and right wheel.
Exercise
Set the fixings as follows:
"Spring Fixing": None
"Stabilizer Bar Fixing": Pull-/Pushrod
"Pull-/Pushrod Fixing": Lower wishbone.
"3rd Spring Stabi Torsion Bar": None
Set the "Spring Rate" to 23.9 N/mm, the "Torsional Spring Rate" to 40 Nm/deg and the
"Parameters Pull-/Pushrod" to 5000 N/mm.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
42
Defining the axle characteristics
3.3.3
Bushings
Figure 3.8: The Bushings tab.
As in Formula Student cars travelling comfort is not of high priority and elastically bushings
would soften the suspension, so they are not used.
To simulate the inexistent bushings in IPGKinematics they are defined as extremely rigid
(E = 5000 N/mm2 = 5 GPa). This stiffens the bushings in each spatial direction. On that reason the bushings can always be orientated parallel to the stationary axis system. That
means, you do not have to enter any value for "Angle at bushing axle".
Further information find in IPGKinematics Reference Manual.
Exercise
Don’t change anything right now, as the geometrics should be defined first. Just have a look
to the "main path" and check if it corresponds with the directory for these files on your computer (e.g. C:\IPG\kinematics\version\template).
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
43
Defining the axle characteristics
3.3.4
Mass
Figure 3.9: The Mass tab
The mass referred to "Load" is only used if you want to add a specific load that does not
belong to the car. It is usually set to 0 as you do not simulate any loaded trunk compartments in racing cars!
In the following the mass of each part of the suspension and the axle load must be defined.
Beware that the axle weight is not the total weight of the axle but the axle weight reduced
by the single masses listed below.
The chassis subframe mass can be set at any value except 0 (we have chosen the option
"Chassis Subframe Off" in the "General" tab so the mass is not considered in the calculation). However, setting the mass to zero will generate a failure.
Exercise
Set the following values for the masses:
Formula CarMaker Tutorial
Load
0 kg
Axle Weight
140 kg
Chassis Subframe
10 kg
Lower Wishbone
0.5 kg
Wheel Carrier
0.45 kg
Wheel
10.5 kg
Upper Wishbone
0.4 kg
Steering Rod
0.25 kg
Steering Rack
0.2 kg
Stabilizer Bar
0.4 kg
Stabilizer Link
0.08 kg
Rocker Arm
0.08 kg
Version 2.3
Parametrization - Vehicle
44
Defining the axle characteristics
The GUI does not discern between front axle and rear axle. Please leave the default values
for parts which do not occur. In case of entering "0" it could be possible to get arithmetic
errors.
3.3.5
Geometry
Figure 3.10: The Geometry tab.
Axis System
As explained in chapter 3.2 the axis system in accordance to DIN 70000 is used.
Coordinates
The coordinates being defined in this section are the most important of all. The calculations
of the kinematics and steering kinematics are based on these values. For that reason the
entry of these points should be done carefully to generate a model being as accurate as
possible.
In the table you only define those points for the left half of the axle. IPGKinematics automatically mirrors the values for the other half so as to model the complete axle.
In the following only some of the crucial points are explained. You will find a detailed
description of all entries in the IPGKinematics Reference Manual, chapter 4.3.
•
"Force Application Tire Forces": Usually the same values as "Center of Tire Contact".
•
"Body - Chassis Subframe Front/Rear": As mentioned before Formula Student cars
usually don’t use subframes. To give feasible values to the program enter the mounting
points of the lower wishbones on the chassis.
•
"Subframe - Bushing Front/Rear Lower Wishbone": As the subframe is deactivated it
corresponds with the body mounting points of the lower wishbones.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
45
Defining the axle characteristics
•
"Spring/Damper body": Although these points are not used in case of a Pull-/Pushrod
actuated suspension feasible values are needed as IPGKinematics will generate an
error if you leave them out. Thus, a good value to choose is the same as
"Wheel Carrier - Lower Wishbone" + 500 mm in height.
•
"Spring/Damper Wheel suspension": Although these points are not used in case of a
Pull-/Pushrod actuated suspension feasible values are needed as IPGKinematics will
generate an error if you leave them out. Thus, a good value to choose is the same as
"Wheel Carrier - Lower Wishbone".
•
"Axle Drive Shaft - Differential/Wheel": Even if you simulate a non-driven shaft, plausible values are necessary. A good value to choose is the same as "Wheel Center" and
the middle of the axle.
•
"Rotation Axis - Rocker Arm": It can be any point on the rotation axis of the rocker arm
to define this axis.
•
No matter which kind of Stabilizer is used, the coordinates for the U-Stabilizer need feasible values. Therefore follow these guidelines for the U-Stabilizer coordinates:
-
"Stabilizer Link - Wheel Carrier": equal to point "Wheel Center"
-
"Stabilizer Bar - Stabilizer Link": add 100 mm in height to the former point
-
"Stabilizer Bar - Chassis Subframe": add 200 mm in x direction to the former point.
Figure 3.11: Overview of the kinematics points.
To illustrate the meaning of the points of the double wishbone model with a U-Stabilizer
explained above, compare figure 3.11 with Table 3.1. The numbers stand for the following
points:
Table 3.1: Listing of the geometry points in figure 3.11.
Number
Item
1.1/1.2
Chassis Subframe - Bushing Front/Rear Lower Wishbone
2
Pull/Pushrod - Wheel Suspension
3
Wheel Carrier - Lower Wishbone
4
Center of Tire Contact
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
46
Defining the axle characteristics
Table 3.1: Listing of the geometry points in figure 3.11.
Number
Item
5
Wheel Center
6
Wheel Carrier - Steering Rod
7
Wheel Carrier - Upper Wishbone
8.1/8.2
Body - Bushing Front/Rear Upper Wishbone
9
Wheel Carrier - Stabilizer Link (Stabilizer Link - Stabilizer Bar)
10
Chassis Subframe - Stabilizer Bar
11
Pull-/Pushrod - Rocker Arm
12
Body - Rocker Arm
13
Spring Element - Rocker Arm
14
Spring Element - Body
15
Rotation Axis Rocker Arm
The points shown in figure 3.12 describe the T-Stabilizer. In case of using a U-Stabilizer,
these coodinates should keep the default values.
In case of using a T-Stabilizer by choosing push/pull rod as the Stabilizer Bar Fixing, the
stabilizer points shown in figure 3.11 above will remain unused during the simulation. Nevertheless, the coordinates for the U-Stabilizer need feasible values and should be parameterized as explained above.
Stabilizer torsion bar
Rocker arm right
16
19
20
Rocker arm left
17
18
Figure 3.12: Geometry of Stabilizer via push/pull rod (top view)
The names of the points above are listed in Table 3.2
Table 3.2: Listing of geometry points in figure 3.12
Number
Item
16
Joint Stabi Torsion Bar - Body
17
Rod Stabi Torsion Bar - Rocker Arm
18
Rod Stabi Torsion Bar - Torsion Bar
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
47
Defining the axle characteristics
Table 3.2: Listing of geometry points in figure 3.12
Number
Item
19
3. Spring Stabi Torsion Bar - Body
20
3. Spring Stabi Torsion Bar - Torsion Bar
•
"3. Spring Stabi Torsion Bar - Torsion Bar": This point defines the connection point of
the third spring, the stabilizer and the rotation axis of the torsion bar. Therefore it needs
to be placed correctly, even if there is no third spring used.
•
"Marker Damper Rocker Arm":It does not affect the simulation results and is not needed in formula student cars. The only requirement to this point is, that the y-coordinate
must not be zero since this leads to an error during the simulation.
•
"Car Body (Turning Circle Diameter)": It defines the place needed by the car when it
turns. It describes the difference between turning track diameter and turning circle
diameter. So, it is the point next to the outer skin of the car body, input values are the xand y-coordinates and the radius to the outer skin. In Formula Student cars this value is
of minor priority as the minimum turning track diameter is more important. Hence, you
can leave any values.
radius
Y
X
Figure 3.13: Turning circle and turning track diameter. [HE07]
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
48
Preparing a vehicle dataset in CarMaker
3.4
Preparing a vehicle dataset in CarMaker
There are two ways to prepare a completely new vehicle dataset.
The first one is to adapt a pre-existing problem-free running dataset step by step. The main
advantage of this method is, that the entered data can be checked easily. Knowing that the
former test run worked without any problems, a driver adaption or a new simulation run tells
you if there are any mistakes in the changes made. This can save plenty of time in debugging but at the same time the data input process is more time-consuming as the test runs
have to be performed incessantly.
The second opportunity is to use an empty dataset. This method saves a lot of time during
the parametrization process. However, the time gained can be easily lost during a complex
debugging process as the user doesn’t know where exactly the mistake is located. A few
common error messages are described in section 6.1.1.
In case of preparing a vehicle dataset of a Formula Student racing car it is recommendable
to choose the first option as a CarMaker model of a For mula Student car
("FS_RaceCar_5.1") which already exists. It was designed on that purpose so that a Formula Student Team has guided values and needn’t start from stratch. Thus, you have an
operating vehicle model with values of proper range. All you need to do is to adjust the predefined values to fit your car.
Vehicle Data Set
Select the "FS_RaceCar_5.1" in the Main GUI.
To open the "Vehicle Data Set" window click: "Parameters > Car".
Note: Except if specified, all units are set in the International System of Units (SI). Accordingly, lengths are in meter and angles in radian (pay attention, not degree!).
3.4.1
Vehicle Body
Figure 3.14: Vehicle Data Set - Vehicle Body
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
49
Preparing a vehicle dataset in CarMaker
In this tab you can choose your body to be flexible if you select "Vehicle Body > Flexible".
This option allows to regard bending and torsion effects of the main body. Otherwise the car
is considered as infinitely stiff. By activating the option "Flexible", the hidden input boxes
turn active. In the upper part you can separate your body into two bodies called A and B A for the front and B for the rear part. Both parts are defined by their own mass, center of
mass and inertias.
Below coefficients of torsional body stiffness in x- and y-direction can be defined. When
choosing the mode "1D Look-Up Table" instead of "Characteristic value" a non-linear characteristic can be edited.
Please keep in mind, that only very exact (measured) values for a flexible body make sense,
otherwise the use of the rigid body is recommended.
Center of Gravity
The calculation of the vehicle center of gravity is very complex and challenging. Even with
the help of CAD and CAE tools, it is only possible when every single body is defined in the
model with all its physical properties.
A much easier possibility is to measure the total center of gravity. Therefore, the car must
be brought to an absolutely horizontal position. To measure the axle load, one axle at a time
is put on the scales. Setting up the balance of moments at the front axle the position of the
center of gravity can be determined as follows:
m V, r
l f = ------------ ⋅ l
m V, t
m V, f
l r = ------------- ⋅ l
m V, t
(EQ 16)
(EQ 17)
With l = wheelbase, lf = distance between the center of gravity and the front axle, lr = distance between the center of gravity and the rear axle, mV,f = axle load at the front, mV,r =
axle load at the rear and mV,t = total weight.
Figure 3.15: Locating of the vehicle center of gravity. [RB00]
To determine the height of the center of gravity a second measuring setup is required. In
this, one axle is jacked up by the height h. It is necessary to jack the vehicle as high as possible to avoid measuring faults. Moreover, the following issues should be taken into account:
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
50
Preparing a vehicle dataset in CarMaker
•
Rolling of the car should be prevented using wedges. Brakes should be released and
the engine should idle. If this is not the case, bracing can occur which are likely to affect
the exactitude of measurement.
•
The wheels should be placed in the middle of the scales to prevent inexact measures
due to different force initiation points.
•
The vehicle should be roadworthy which means refuelled including the driver with his
equipment.
•
The axle springs should be blocked to prevent deflection. Otherwise this could lead to
measuring faults.
•
To prevent tire deflection a high pressure should be attained.
The car’s angle of slope is defined as follows:
h
sin α = --l
(EQ 18)
To determine the height hV of the center of gravity ∆lr (see figure 3.16) is required because
of
h V = h' V + r dyn
(EQ 19)
∆l r
h' V = -----------tan α
(EQ 20)
∆lr can be calculated setting up the balance of moments for the front axle. Then, the height
hV can be estimated with the following equation:
l
∆m
2
2
h V = ------------ ⋅ -------- ⋅ l – h + r dyn
m V, t h
(EQ 21)
The meaning of the single parameters is shown in the figure below:
Figure 3.16: Determining the height of the center of gravity. [RB00]
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
51
Preparing a vehicle dataset in CarMaker
With this procedure, however, only the center of gravity of the complete vehicle can be measured. The many centers of gravity of single components being required by CarMaker must
be determined in a different manner. To locate the driver’s center of gravity the measurements explained above are carried out with and without the driver. Afterwards the center of
gravity can be calculated setting up the balance of moments.
The same procedure enables the location of the engine’s center of gravity. The determination of the other masses required can be achieved by weighing the single parts. Beware,
the half-sprung parts such as wishbones, tie rods and driving torques are added one half
each to the body and to the wheel carrier.
Moments of Inertia
One attempt to estimate the moments of inertia is to replace each assembly by a simple
geometric body and then calculate the moments of inertia with the known formulas. These
approximations deliver acceptable results, though.
More exact values can only be gained with complicated and cost-intensive experiments.
Here, the moments of inertia are determined by the oscillation period of the considered part
on a torsion pendulum in relation to the oscillation period of a reference body. For this reference body a simple geometry is chosen so that its moments of inertia can be easily calculated for comparison. An even better possibility offers a test bench especially designed
to determine the inertial tensor of fourwheeled vehicles.
3.4.2
Bodies
Figure 3.17: Vehicle Data Set - Bodies
Each simulation model is based on the masses of the single bodies and their moments of
inertia. Concerning vehicles these masses are the suspension (unsprung masses) and the
body (body masses). In CarMaker these two groups are divided into further sections. The
unsprung masses are classified into spinning (e.g. wheel, rim, wheel-hub) and non-spinning masses (e.g. wheel carrier, half the wishbone or brake caliper). So, do not forget to add
the weight of the disk brake to the wheel masses. Furthermore, note that the unsprung
masses which have a link with the body should only be considered by half of their weight
as the rest isn’t unsprung.
The driver can additionally be defined with the "Trim Load" entries.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
52
Preparing a vehicle dataset in CarMaker
Positions
CarMaker calculates the car’s movements in an axis system referred to as "Fr1". The origin
should be placed at the rearmost end of the car (see section 3.2 in this document or the
CarMaker Reference Manual). However, you may have the values of the "Masses" positions
in an axis system whose origin is forward the rear axle. If so, in the box "Origin Fr1" you can
define a translation between Fr1 and your design axis system and you will be able to write
the positions directly with the values you initially have.
3.4.3
Engine
Figure 3.18: Vehicle Data Set - Engine
There are three possibilities to get the engine’s mass into the vehicle data set. The easiest
way is to add the mass to the "Vehicle Body" masses, especially when you do not have any
detailed information about it. When you know the position of the engine’s center of gravity
and maybe the moments of inertia, you should define a "Trim Load" under the "Bodies" tab.
Lastly, you can activate the option "Elastically mounted Engine" under the "Engine" tab and
enter all the needed parameters. This helps you to fine-tune your race car model. More
information about the elastical mounting can be found in the Reference Manual at section
"Engine".
Exercise
Increase the vehicle body weight to 220 kg and its center of gravity to 0.5 m above the
ground (RigidBody, Vehicle Body A). Then subtract 0.2 kg from the spinning disc brakes
which are included in the wheels. Keep the moments of inertia values same.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
53
Preparing a vehicle dataset in CarMaker
3.4.4
Suspensions
Figure 3.19: Vehicle Data Set - Suspensions
Spring
The spring rate of the axle spring has already been defined in IPGKinematics. The same
values should be entered here. The parameter l0 is the actual free length of the spring in its
unmounted state. You can let this value be calculated automatically by CarMaker which
does some iterations during the determination of the car’s static equilibrium position in the
preparation phase ahead of every simulation. If the car’s position on the road does not
match with your real car, this value serves as an adjustment parameter.
Exercise
Increase the front stiffness up to 45 000 N/m and the rear stiffness up to 52 300 N/m. Leave
the length l0 unticked.
Damper
The final damper settings are mostly determined directly on the vehicle through empiric test
runs. On that reason not even the average damper force for the final damper setup is
known. Accordingly a significant damper characteristic can only be determined via test runs
on the real vehicle or using special test benches. If both opportunities are available you
should always choose the test bench, as measurements on the real vehicle can be distorted
by friction on the suspensions. Moreover, test benches enable a wide range of speed (up
to n = 200 min-1) and travel (5 - 150 mm) to be tested. They also deliver directly the required
characteristic "damper force via speed".
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
54
Preparing a vehicle dataset in CarMaker
Exercise
Set the damper values to:
Damper Front - Push:
Damper Rear - Push:
velocity [m/s]
force [N]
velocity [m/s]
force [N]
0.0
0.0
0.0
0.0
0.125
525.80
0.125
566.25
0.25
788.70
0.25
849.37
Damper Front - Pull:
Damper Rear - Pull:
velocity [m/s]
force [N]
velocity [m/s]
force [N]
0.0
0.0
0.0
0.0
0.125
1183.06
0.125
1274.06
0.25
1774.58
0.25
1911.09
Buffer
The springs used in Formula Student cars are so stiff that only little spring travels are possible. However, construction-conditioned much bigger travels are feasible. For that reason
and to prevent resiliences making the car softer, buffers are commonly not used in those
cars.
To implement that in CarMaker, two steps are required. On one hand, a large stiffness is
attached which reduces the elasticity considerably. On the other hand, the positions of the
buffers are set very high (respectively low) so that they aren’t activated in general.
The length tz0 defines the limit above which the wheels are prevented to deflect. For a clear
illustration see also Reference Manual, chapter "Suspension Force Elements".
Stabilizer
The stabilizer parameters have already been explained in section 3.3.2. In CarMaker the
same stiffness must be used. Beware: CarMaker uses a linear spring rate [N/m] as opposed
to IPGKinematics which uses a torsional spring rate [N/deg]. The following will show you
how to convert the spring rate.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
55
Preparing a vehicle dataset in CarMaker
Figure 3.20: Converting the stabilizer bar spring rate.
The translation is based on the balance of moments around the pivotal point and on the balance of forces in z-direction:
b
b
F 1 ⋅ --- + F 2 ⋅ --- + M A = 0
2
2
F1 = F2
(EQ 22)
(EQ 23)
Solving and inserting into each other provides:
M
F 1 = --------Ab
(EQ 24)
Further the rolling moment MA is known:
M A = cϕ ⋅ ϕ
(EQ 25)
With MA being inserted:
F1 ⋅ b = cϕ ⋅ ϕ
(EQ 26)
In consideration of:
F = cx ⋅ x
(EQ 27)
and
2x
tan ϕ = ------ ≅ ϕ
b
(EQ 28)
you finally get the stabilizer bar spring rate:
2
c x = c ϕ ⋅ ----2b
Formula CarMaker Tutorial
(EQ 29)
Version 2.3
Parametrization - Vehicle
56
Preparing a vehicle dataset in CarMaker
Kinematics, Compliance and External Forces
All these fundamental parameters were calculated using IPGKinematics. To import the data
in CarMaker load both of the skc-files for front and rear axle. See also the last exercise in
section 2.4.8.
Exercise
Load the generated skc-files if you have generated a IPGKinematics dataset for the front
axle as well as for the rear axle. For further information please refer to section 2.4.8.
3.4.5
Steering
Figure 3.21: Vehicle Data Set - Steering
Static and Dynamic Steer Ratio
To simulate a steered axle CarMaker only needs the ratio between steering wheel angle (in
radians) and steering rack travel (in meters). The ratio does not have to be static: non-linear
maps are available under the "Mode" selection menu.
Note: The ratio between steering rack travel and wheel angle is a part of the kinematic data
generated in IPGKinematics and will be transferred to CarMaker using the skc files.
Pfeffer with Power Steering
You can also use the Pfeffer Power Steering model which is a very detailed steering model
including friction loss effects, elasticities and power steering. This model consists of a
Mechanical Module which includes all mechanical components (transferring torque from
the steering wheel to the tie rods). Also a Power Assistance Module e.g. hydraulic (HPS),
electrical (EPSc and EPSapa) can be parameterized.
In the User’s Guide, section "Parameterization: Vehicle Model > Steering System > Pfeffer
Power Steering" you find more information about the different models.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
57
Preparing a vehicle dataset in CarMaker
3.4.6
Tires
Figure 3.22: Vehicle Data Set - Tires
Here the tires for the race car can be selected. The tire attributes belong to the vehicle
parameters and will be loaded automatically by selecting a car. Additionally you have the
opportunity to overrule these tire files by selecting another one in the CarMaker main GUI.
Learn more about how to import own tire data in the next chapter.
3.4.7
Brake
Figure 3.23: Vehicle Data Set - Brake Control
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
58
Preparing a vehicle dataset in CarMaker
The Hydraulic Brake Control model "HydBasic" gives the possibility to use regenerative
wheel brake torque in a electrical or hybrid powertrain. The regenerative brake torque can
either be applied by a parallel or a serial strategy as show in figure 3.24.
Wheel
brake
torque
Parallel strategy
target total
wheel brake
torque
target regen.
wheel brake
torque
actual maximum regen.
wheel brake torque
Pedal
Wheel
brake
torque
actual maximum regen.
wheel brake torque
Serial strategy
target total
wheel brake
torque
target regen.
wheel brake
torque
margin
Pedal
Figure 3.24: Brake torque repartition strategy
The actual hydraulic brake system is parameterized in the tab "System" shown in figure
3.25.
Figure 3.25: Vehicle Data Set - Brake System
It takes several steps to transform the brake pedal force applied by the driver into a brake
torque at the wheels:
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
59
Preparing a vehicle dataset in CarMaker
•
Applying the pedal force by the driver.
•
Enforcing the pedal force through the pedal transmission.
•
Transforming this force into a pressure at the main brake cylinder.
•
Dividing the pressure into two brake cycles.
•
Transforming the pressure into a brake torque.
These five steps are implemented in CarMaker by the definition of the maximum pedal force
and two transmissions. The meaning of the two transmissions "Pedal Force to pMC" and
"Pressure to Brake Torque" will be explained in detail in the following.
Table 3.3: Required parameters for the calculation of the brake system
Explanation
Variable Name
Pedal to Pedal Force
FP
Transmission Braking Pedal
ibp
Diameter Main Brake Cylinder
dmbc
Diameter Brake Piston Front
dbp,f
Diameter Brake Piston Rear
dbp,r
Adhesion Coefficient of the Brake Pads
µb
Effective Radius Braking Disk Front
rbd,f
Effective Radius Braking Disk Rear
rbd,r
Brake Portion Front
bf
Brake Portion Rear
br
Figure 3.26: Schematic layout of the brake system parameters.
The first transmission "Pedal force to pMC" is made up by the quotient of the pressure at the
main brake cylinder pMC and the pedal force FP. Therefore the pressure pMC must be determined first:
F
mbc
p MC = --------------------2
d mbc
π ⋅ -------------4
(EQ 30)
The force Fmbc at the main brake cylinder results from the pedal force reinforced by the pedal transmission:
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
60
Preparing a vehicle dataset in CarMaker
F mbc = F P ⋅ i bp
(EQ 31)
Thus follows:
i bp
p MC
----------- = ---------------------2FP
d mbc
π ⋅ -------------4
(EQ 32)
In general the ratio "Pressure to Brake Torque" is different at front and rear axle. This results
from an unequal brake balance and the used brake types which are mostly different at front
and rear axle. Thus, this ratio must be calculated for each axle separately.
The pressure at the front brake piston is:
p f = b f ⋅ p MC
(EQ 33)
The contact pressure at the front brake disc constitutes to:
2
F ap, bd,
f
d bp, f
= p VA ⋅ π ⋅ --------------4
(EQ 34)
With the brake force at the front disks
F bd,
f
= F ap, bd, f ⋅ µ b
(EQ 35)
the brake torque at the front wheels can be estimated to:
T f = 2 ⋅ r bd, f ⋅ F bd,
(EQ 36)
f
Using equation 33-36 the ratio "Pressure to Brake Torque Front" can be determined:
2
d bp, f
Tf
----------- = 2 ⋅ r bd, f ⋅ µ b ⋅ π ⋅ --------------- ⋅ b f
4
p MC
(EQ 37)
The ratio "Pressure to Brake Torque Rear" is calculated in the same way:
2
d bp, r
Tr
----------- = 2 ⋅ r bd, r ⋅ µ b ⋅ π ⋅ -------------- ⋅ b r
4
p MC
(EQ 38)
The formulas explained guide you through the parametrization of the linear brake model
"Pressure Distribution". However, if you have detailed information about your brake system,
you can activate the more precise brake model "Hyd_ESP_FS_RaceCar_4.0" by selecting
the mode "External File". This model regards characteristics of the single volumes, pipes
and the hydraulic fluid. Moreover, it covers the brake booster as well as the suction and pilot
values as an interface for ABS and ESP controllers.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
61
Preparing a vehicle dataset in CarMaker
For more information about this very detailed model please refer to the Reference Manual
or open the template "HydESP_FS_RaceCar_4.0". Each line starting with a hash is a comment!
Exercise
Increase the braking ratio up to 75% without changing the available input braking force:
Set the "Pressure to Brake Torque" front to 12 at each wheel and the "Pressure to Brake
Torque" rear to 4 at each wheel.
3.4.8
Powertrain
Overview
CarMaker gives you the possibility to choose between several powertrain models such as
pure combustion, hybrid and electric vehicles. You can start the parameterization of any
powertrain Model by choosing predefined powertrain setting a right click in the powertrain
window.
Depending on the selected powertrain model, one to four drive sources (numeration: 0-3)
appear in the powertrain window. The drive source characteristics as well as the gearboxes
and clutches can be parameterized in the corresponding drive source tab.
The connection between the drive sources and the wheels is defined by the driveline model.
The required control units, such as a Engine Control Unit, Transmission Control Unit, Battery Control Unit and a Motor Control Unit for hybrid or electrical vehicles can be parameterized in the corresponding tab.
Finally, the power supply is presented as a LV and, if necessary, a HV battery model.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
62
Preparing a vehicle dataset in CarMaker
Combustion Vehicle
The first thing to do in order to parameterize a combustion powertrain is selection the generic powertrain model with a right click in the powertrain window. "Generic" is a common combustion engine model including clutch, gearbox and differential (e.g. the FS_RaceCar_5.1).
All quantities and parameters from the engine right up to the wheels can be set by the GUI
and will be calculated conventionally by CarMaker.
Figure 3.27: Vehicle Data Set - Combustion Engine
Drive Source
Engine Model
The engine used in your Formula Student car can be defined by several ways. One possibility is to use the Engine Model "Characteristic Value" what assumes a linear distribution
between gas pedal and engine torque. You can also choose the option "Look-Up Table".
Engine Mapping
With the option "Look-Up Table" you have the opportunity to define a full load power curve
(1D Look-Up Table) by inserting single points. This option is a lot more precise, but you have
to do measurements on an engine test bench.
Another exponent defines the transition from the full load to the part load power curve.
Along with the full load characteristic some other engine parameters like the drag torque
characteristic, the range of speeds and the idle speed are required. Note that the entered
full load power curve must start and end at zero.
A further possibility is to define a 2D Look-Up Table with the dependence between the gas
pedal, the engine speed and the output torque.
Fuel Consumption
This feature enables a prediction of the fuel consumption. Activate the tick box and you have
the possibility to enter values of specific fuel consumption. Therefore, you have to do measurements which reflect these points.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
63
Preparing a vehicle dataset in CarMaker
Figure 3.28: Powertrain - Fuel Consumption
The values for the Fuel Tank, Turbocharger and Intake Manifold can be left by their
default values. For further informations, please take a look at the Reference Manuel.
Starter Motor
It is possible to define the power and torque of the starter motor as well as the power supply
source. For Formula Student Cars, the pre-defined values can be used.
Clutch
The pre-defined values can normally be used for a Formula Student car. Choose the mode
"Friction".
Figure 3.29: Powertrain - Clutch
Gearbox
Here, the transmission ratio of each gear has to be specified. Furthermore, there is an
opportunity to define the time for synchronization. Although Formula Student cars usually
don’t have any reverse gear, it is necessary to define one as otherwise the program generates an error message.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
64
Preparing a vehicle dataset in CarMaker
Figure 3.30: Powertrain - Gearbox
Driveline
General
The Driveline Model determines the connection between the Drive Source and the wheels.
For most Formula Student combustion cars, the Rear Drive model should be suitable.
Real Axle
For a Formula Student car choose the model "Torque Sensing" and the mounting mode
"Left to Right".
To parameterize the differential the three values "Driven", "Dragged", and "Transmission"
should be adjusted. In case you use a motorcycle powertrain, you have a primary ratio
between the engine and the gear box. You should consider this primary ratio together with
the final ratio. Thus multiply the final transmission ratio by the primary transmission ratio for
the "Transmission" value in the "Differential Rear" tab.
The torque bias (TB) is used when a wheel is spinning (e.g. on ice) while the other one has
more grip. In this situation some differentials are able to limit the torque transmitted to the
spinning wheel (Tlow) so as to favor the wheel that has more grip (it receives Thigh). TB is
the factor between Tlow and Thigh. For instance: if TB = 2, the differential will limit the torque
to the spinning wheel to 33.3% and give 66.6% to the other wheel (twice as much as at the
spinning wheel).
Figure 3.31: Powertrain - Differential Rear
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
65
Preparing a vehicle dataset in CarMaker
Control Unit
The powertrain model contains four Control Units:
•
ECU (Engine Control Unit) - Combustion Engine
•
TCU (Transmission Control Unit) - gearboxes and clutches
•
MCU (Motor Control Unit) - electric motors including the integrated starten motor
•
BCU (Battery Control Unit) - power supply including the batteries
The PT Control is a global control unit whose main task is to provide target values for the
controler algorithms of the other control units.
Figure 3.32: Powertrain - Control Units
PT Control
For a FS combustion car, the control model Generic is most suitable. This control model
allows driving with the combustion engine only, without any use of the starter motor or other
electric motors during driving.
The operation state machine can be left as generic as well.
ECU
The Basic ECU Model contains a PI controller for the idle speed control and the load controler. The predefined values can be used for most FS cars. For more information on the P/
I values, please take a look in the Reference Manual.
TCU
There are four different TCU Models in CarMaker. For a automatic gearbox, the logic for
gearshifting and the shifting limits need to be parameterized.
In case of a manual gearbox that is shifted by the driver, select not specified as TCU Model.
MCU
The Basic MCU Model consists of a PI controller for the load control of all electric motors.
For a pure combustion car, this is only the starter motor. The predefined settings should be
suitable for most applications. For more informations on the controller, please take a look in
the Reference Manual.
BCU
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
66
Preparing a vehicle dataset in CarMaker
The BCU calculates characteristic battery values such as the soc. If the battery is not of
interest, the BCU model can be declared as not specified.
Power Supply
The Power Supply consists of the electric circuits, the battery models and the auxiliary consumers. There are four different power supply configurations available. A LV circuit can be
expanded with up to two HV circuits. The batteries are modeled as a chen model with two
RC-circuits and a single resistance that are connected in series.
If the power supply is not of interest, it can also be declared as not specified.
Exercise
Keep the rear driven transmission configuration (Generic > Rear drive).
Increase the engine maximal torque up to 65 Nm and smooth the curve.
Reduce the final transmission ratio to 3.5 (in "Differential Rear > Transmission") and
increase the driven Torque Bias to 3 (in "Differential Rear > Torque Bias Ratio Driven").
3.4.9
Aerodynamics
As aerodynamics become ever more important in the Formula SAE competition, you can
use the detailed aerodynamics model in CarMaker to simulate its effects. In dependence
on the air flow angle tau, the coefficients for the resistance forces and torques in all three
directions of space have to be specified. For this, a wind tunnel test or at least a very comprehensive CFL model is required.
Please find further information about the measurement procedure of the required coefficients in the Reference Manual.
The "Reference Point" determines the point of attack for the combined wind forces. The
"Reference Area" usually describes the front area of your car and the "Reference Length"
corresponds to the wheel base of your car.
Figure 3.33: Vehicle Data Set - Aerodynamics
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
67
Preparing a vehicle dataset in CarMaker
3.4.10
Sensors
In the Sensor tab you have the opportunity to create different kinds of sensors. The Side
Slip Angle Sensor is bound to the center of gravity normally. If you like to place it anywhere
else just change the parameters of the sensor’s position. A Body Sensor is an inertial sensor that can be placed anywhere on the vehicle to measure the movements, velocity, rotational velocity, acceleration and rotational acceleration. All corresponding output quantities
will be attached to IPGControl automatically. To get to know more about sensors please
read the Reference Manual.
Figure 3.34: Vehicle Data Set - Sensors
3.4.11
Vehicle Control
The next tab "Vehicle Control" is only relevant to integrate controller systems, mainly for
driver assistance systems.
The integration of controller models relevant for Formula Student cars is demonstrated by
several CarMaker for Simulink Examples such as "FSE_TorqueVectoring.mdl",
"HydBrakeCU_ESP.mdl". Please find further information in chapter 4.4.
3.4.12
Misc.
In this tab you can choose the pictures displayed in the main GUI and IPGMovie.
Vehicle Graphics
To display your own car in the CarMaker GUI there are two possibilities: writing a tcl/tk file
or importing a texture.
Using a texture you can import any picture you like in the png or jpeg format. However, you
need a picture of your car in top view as well as in side view.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
68
Preparing a vehicle dataset in CarMaker
In the following it will be described how you can create a png picture of your car using IPGMovie. You need to make two screenshots: one of the top view and one of the side view.
The screenshots should be oriented as the picture below shows:
Figure 3.35: Side View
Figure 3.36: Bird’s Eye View
Pay attention to the following:
•
select Camera > Bird’s Eye View / Right Side in IPGMovie
•
set the field of view to 10 (Camera > Camera Settings)
•
maximize your IPGMovie window
•
place the camera in the middle of the screen
•
zoom out with fixed camera position (View > Fix Camera View Direction)
•
take a screenshot
After that the screenshots have to be reworked for the display in CarMaker. For that, load
the taken screenshots into a graphic tool. Select a rectangle close to the outer shape of the
car and paste it to a new file. Place the car with its back at the left margin of the window (in
case of a side view additionally align it vertically to the bottom). Then, the picture needs to
be scaled to the length of the car (1m=100pixel) and saved as a png image.
With your graphic tool you need to delete everything around the car to create a transparent
background.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
69
Preparing a vehicle dataset in CarMaker
Figure 3.37: Side View with transparent background
Now select all and paste it to another file of the size of 560x226 pixel (72 dpi). Again move
the picture to the left side of the window (in case of a side view additionally align the it vertically to the bottom). Now the picture is ready to export. For this, save the side view as "filename.png" to the "Data/Pic" directory of your project folder. The top view should be saved
to the same folder as "filename.top.png.
Finally, to display your car in the CarMaker main GUI and in the vehicle data set window go
to Parameters > Car > Misc and select your picture (side view) in the field "Vehicle Graphics".
Figure 3.38: Vehicle Graphics using the png-format
MOVIE object
To display your own car in IPGMovie you need to export the car you have drawn in your CAD
or modeling software in the object format (.obj Wavefront format).
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
70
Preparing a vehicle dataset in CarMaker
This object format requires another material file (.mtl, see hereunder). Once they are generated both of these files have to be stored in the "Movie" folder of your project (e.g.
"Car_Generic/Movie").
However, as you generate the files, you should pay attention to the following advises:
•
Generate the file exclusively with triangles and polygons as CarMaker doesn’t accept
free-forms.
•
Do not choose a too high number of polygons/triangles: about 30 000, never more than
50 000.
•
This is not compulsory, but it enhances the rendering of the object: generate a normal
for all points ("vn" coordinates).
•
Pay attention to include also your materials, otherwise your car will appear grey colored. Therefore, a second file (.mtl file) must be generated which is called at the beginning of the .obj file (see listing here under).
•
Positions of points described in the .obj file don’t have any units. Thus, once your file is
generated you may have to translate, scale or rotate your car with the factors that you
can find in the first lines as the following shows:
### BEGIN IPG-MOVIE-INFO
# NumPlate CarMaker 0.40 0.00 0.12 0 0
0.55 0.13
# Translate 1.42 0.025 0.0
# Scale
0.32 0.46 0.455
# Rotate
90 1 0 0
### END IPG-MOVIE-INFO
mtllib FS_RaceCar.mtl
Please find further information on the various options for obj files in the User’s Guide.
Vehicle Outer Skin
If an obj. file as described above is not available, there is another possibility to display your
car in IPGMovie: an Abraxas model. This model is basically a simple, rectangular box which
refers to the maximal dimensions of your car. To determine these maximal dimensions two
points are required which face each other diagonally. It’s these very points which have to be
entered here.
Figure 3.39: Outer dimensions of the FS_RaceCar shown in the Abraxas mode.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
71
Creating a tire dataset using IPGTire
3.5
Creating a tire dataset using IPGTire
The tire is one of the most important components of a vehicle. All forces and torques are
transferred from the road to the car through the tire. Hence, the tires provide the basis for
all lateral and longitudinal dynamics of a vehicle. Thus, the tire model used in a simulation
must be a detailed one. Therefore, CarMaker offers different opportunities:
3.5.1
•
Pacejka Magic Formula
•
IPGTire
•
TameTire
•
Tire Data Set Generator
Pacejka Magic Formula
The Pacejka Model is based on a complex mathematical formula. Its parameters, called
"Magic Parameters", do not have any physical meaning. They are calculated with suitable
programs using test readings. If you’d like to have more information about the Magic Formula, see the CarMaker Reference Manual.
y ( x ) = D ⋅ sin [ C ⋅ atan { Bx – E ( Bx – atan ( Bx ) ) } ]
Figure 3.40: The Magic Formula.
In the following there will be given some advice on how to generate a Magic Parameters
dataset based on measured raw data from a flat belt tire testrig. The used test data is from
the database of FSAE TTC - Tire Test Consortium.
"The Formula SAE Tire Test Consortium (FSAE TTC) is a volunteer-managed organization
of Formula SAE teams who pool their financial resources to obtain high quality tire force
and moment data. The FSAE TTC’s role is to gather funds from participating FSAE teams,
organize and conduct tire force and moment tests and distribute the data to all participating
teams." [http://www.millikenresearch.com/fsaettc.html]
To be able to generate a set of parameters from the tire data you need to fit the Pacejka tire
model to the tires’ measured raw data. The fitting process of the Magic Formula curves is
an iterative process. It is either feasible to program a script in e.g. Matlab to generate the
parameter set or to use commercial software. In the FSAE many teams use the software
OptimumTire from OptimumG.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
72
Creating a tire dataset using IPGTire
"OptimumTire is a convenient and intuitive software package that allows users to perform
advanced tire data analysis, visualization, and model fitting. The model fitting procedure is
very fast and efficient partially due to the data processing tools incorporated into the software." [www.optimumg.com]
The software is available as free trial version at optimumg.com. The preprocessing and fitting process to generate the Magic Formula parameter set of a tire is described in a tutorial
also available at OptimumG’s website.
In addition to the tutorial a few hints regarding the preprocessing and optimization:
•
Take care of the coordinate system you use while importing the raw data into OptimumTire. The coordinate system the data was measured is in SAE coordinate system.
•
The raw data including warming phase and beginning and end of SA sweeps looks like
this :
Figure 3.41: Raw tire data in OptimumG
•
You should remove the warming phase and spring stiffness measurements as well as
the first and last 3˚ of SA sweeps.
The cropped data looks way smoother and periodical. The fitting process works way
better based on this kind of data.
Figure 3.42: Cropped tire data in OptimumG
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
73
Creating a tire dataset using IPGTire
Import Model into CarMaker
Before you export your data you should choose ISO as coordinate system for your fitted
Pacejka MF5.2 model. The question pops up whether you want to "convert" or "interpret as
new coordinate system". Choose convert!
In OptimumTire there are several ways of exporting the generated data. Use the export to
.TIR function.
•
Copy the generated tire data and paste it in an ASCII File. Rename the file something
like DD.MM.JJJJ_TireType_TyreSize.tir and put it into /Data/Tire/Examples/Pacejka in
your CarMaker project directory.
•
Use the CarMaker Tire Data Set Editor to convert the .tir file to a CarMaker Infofile. For
this, go to "Parameters > Vehicle > Tires" in the CarMaker main GUI. Keep the folder
button pressed and select "Edit" from the dropdown menu. The Tire Data Set Editor
opens.
Figure 3.43: The Tire Data Set Edito in CarMaker
•
In the File menu of the new window, select "New > Magic Formula 5.2".
Figure 3.44: Generating a new Pacejka tire data set
•
In the first tab "General Parameters" go to the section "Visualization" and adapt the tire
size according to your data set. This information is used by IPGMovie for visualization
only, it does not affact the physical tire characteristics itself.
•
In the next tab "Model Paramaters" import the generated .tir file and with it all the Magic
Parameters to define the Pacejka model. Select "Import Adams Property File" and
choose your tire data from the Examples/Pacejka folder.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
74
Creating a tire dataset using IPGTire
Figure 3.45: Import of an Adams property file
•
Make sure that the following parameters are set correctly:
-
section "MODEL"
PROPERTY_FILE_FORMAT= MF_05
USE_Mode= 14
-
section "ALIGNING"
Align.SSZ2= -2.2371e-09
Align.SSZ3=3.6029e-08
Align.SSZ4=3.9826e-08
Align.QTZ1=0.3
Align.MBELT=7.5
-
# ADAMS property file format
# Tire use switch
#
#
#
#
#
variation of distance s/R0 with Fy/FzNom
variation of distance s/R0 with camber
variation of distance s/R0 with camber and load
Gyroscopic torque constant
belt mass of wheel
section "LONGITUDINAL"
PTX1= 1
# Relaxation length SigKappa/Fz at FzNom
PTX2= 0.2
# Variation of SigKappa/Fz with load
PTX3= -0.15 # Variation of SigKappa/Fz with exponent of load
Attention: The decimal separator in all CarMaker and IPGKinematics applications is dot
(.) instead of comma (,). If there is any error message related to inconsistent metrics
most of the time it is due to wrong decimal separator.
•
3.5.2
Save your tire data set via "File > Save As" in the Tire Data set Editor.
IPGTire
The IPGTire model is also based on measurements. Although, the results aren’t taken to
implement any mathematical formulas but the discrete values can be directly used. The
missing values are estimated via interpolation. The basis for the tire data provides the
TYDEX format. The required files for CarMaker are generated out of a TYDEX file using the
program "tireutil.exe" which is also a tool of the IPG Automotive GmbH. Thus, all you have
to do to create a tire dataset is to prepare a TYDEX file and transform it.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
75
Creating a tire dataset using IPGTire
What is a TYDEX file?
TYDEX is an abbreviation for "Tyre Data Exchange". A TYDEX file is a special format widely
used in the automotive industry to export tire measurement data. It is a ASCII-file with the
extension .tdx that can be opened and read by anyone interested at any time. The TYDEX
format aims at making it easier for participating companies and institutes to exchange tire
data.It is usually generated directly by the tire testbed measurement software and should
not be written by hand.
You can find an example TYDEX file in the FS_Generic_2017 project folder under Data/
Tire/Examples/TUTO_TYDEX_TEST.tdx
Content of a TYDEX file
Axis system
The TYDEX format considers three different axis systems in which the values are measured:
•
TYDEX-C axis system:
Its origin lies in the center of the wheel. The X axis is in the central plane of the wheel
and is parallel to the ground, the Y axis is identical with the spin axis of the wheel (thus
it may not be parallel to the ground in case of non-zero camber angle) and the Z axis
points upwards and is perpendicular to the X-Y plane. So, this axis system moves with
slip and camber.
•
TYDEX-H axis system:
The origin lies also at the center of the wheel. The X axis is in the central plane of the
wheel and is parallel to the ground, the Y axis is perpendicular to the X axis and is
together with the X axis in a plane parallel to the ground and the Z axis points upwards
and is perpendicular to the track surface. So, it moves with slip, but keeps perpendicular to the road in case of camber.
•
TYDEX-W axis system:
This axis system is similar to the H axis system, but its origin lies at the center of the
footprint on the track surface. All axes are oriented like in the H system. So, it moves
with slip, but keeps perpendicular to the road in case of camber.
TYDEX structure
Each TYDEX file is separated in single paragraphs. These paragraphs serve to structure
the tire data. In total there are 14 paragraphs, but not each one is needed. However, the
more information is available the better the resulting tire model is. Each single paragraph is
introduced by one of the following key words:
**HEADER
**COMMENTS
**CONSTANTS
**MEASURCHANNELS
**MEASURDATA
**MODELDEFINITION
**MODELPARAMETERS
**MODELCOEFFICIENTS
**MODELCHANNELS
**MODELOUTPUTS
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
76
Creating a tire dataset using IPGTire
**MODELEND
**END
Detailed information about the single paragraphs can be found on the website mentioned
above. The two most important blocks are "**MEASURCHANNELS" and "**MEASURDATA". The first one defines the variables, values are available for. In the second
block these values are listed. While editing you must be aware of the order: Every line of
the "**MEASURCHANNELS" paragraph belongs to the corresponding column in the
"**MEASURDATA" block. The first row of the "**MEASURCHANNELS" paragraph deals for
instance with the lateral force Fy, the first column in the "**MEASURDATA" block has to
contain the measure data of the lateral force. All acting forces (tangential force Fx, lateral
force Fy, tire load Fz) and torques (pitching moment Mx, driving/braking torque My, selfaligning moment Mz) on the tire can be entered. Moreover there are several parameters
like slip and inclination angle. You can find a complete list of all possible parameters on
this website:
http://www.fast.kit.edu/download/DownloadsFahrzeugtechnik/
TY100531_TYDEX_V1_3.pdf
Data with camber angle
The lateral force applied on the footprint has three components (the same applies for the
self aligning torque):
•
one resulting from the slip angle (Fslip),
•
another (constant) caused by the camber angle (Fcamb),
•
and a third due to the distortion of the contact surface area (Fdis).
Figure 3.46: Components of the lateral force. [TIR07]
But in case of an automobile tire, the last component can be neglected - as opposed to a
motorcycle tire. Then the component due to the camber angle can be easily found by a state
equilibrium calculation. This calculation is done by CarMaker on its own.
Nor does CarMaker need two curves with the same term. For instance: if you have two measures with Fy vs. slip angle with the same vertical load but different camber angle values, it
is gratuitous to store both of them in the TYDEX file as only one camber angle measurement is needed by CarMaker.
Offset coefficients
You can specify offset and scaling factors to be applied to the values. These factors are
specified for all values in the "**MEASURCHANNELS" block.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
77
Creating a tire dataset using IPGTire
Syntax of a TYDEX file
In order to enter your data correctly, you have to follow a few advises. All characters placed
after the symbol "!" are comments that are ignored.
Measurchannel
The syntax of the Measurchannel is the following:
**MEASURCHANNELS
PARAMETER_KEY1
comment1
PARAMETER_KEY2
comment2
PARAMETER_KEY3
comment3
unit1
unit2
unit3
correction factors value1
correction factors value2
correction factors value3
and so on...
Between each part of the line you should leave a certain number of blank spaces; pay attention to not use Tab-spaces:
•
the first character of the parameter key starts at the first character of the line
•
the first character of the comment is the 11th character of the line
•
the first character of the units is the 42nd character of the line
•
the first character of the first factor is the 52nd character of the line
•
the first character of the second factor is the 62nd character of the line
•
the first character of the third factor is the 72nd character of the line
The parameter key must be written according to the list available on the mentioned website.
The parameter key also defines which axis system is used for the values: for example,
"FZH" defines a vertical load in the TYDEX-H axis system and "FZY" defines the same vertical load in the TYDEX-C axis system.
Measurdata
In this block, the values on each line describe a particular point of the curve. A new line
defines a new point. Each value must be separated from the other by at least one blank
space.
For instance, hereunder 3 points are defined. In each line the first value is the vertical force,
the second the slip angle, the third the camber angle, the fourth the lateral resulting force
and the fifth the self-aligning torque. In the hereunder example the "**MEASURCHANNELS" block is displayed again for reminding:
**MEASURCHANNELS
FZH
Vertical force
SLIPANGL Slip angle
INCLANGL Inclination angle
FYH
Lateral force
MZH
Aligning moment
**MEASURDATA
1211.00
-0.50
0.00
211.21
3021.70
-0.50
0.00
460.01
4828.00
-0.50
0.00
641.08
N
deg
deg
N
Nm
1
0
0
1
0
0
1
0
0
1
1
0
0
0
0
-2.27
-8.08
-15.50
If, for example, you don’t have the values of the self-aligning torque, you will write:
**MEASURCHANNELS
FZH
Vertical force
SLIPANGL Slip angle
Formula CarMaker Tutorial
N
deg
1
1
0
0
0
0
Version 2.3
Parametrization - Vehicle
78
Creating a tire dataset using IPGTire
INCLANGL Inclination angle
FYH
Lateral force
**MEASURDATA
1211.00
-0.50
0.00
211.21
3021.70
-0.50
0.00
460.01
4828.00
-0.50
0.00
641.08
deg
N
1
1
0
0
0
0
Furthermore, it is possible to define several couples of "**MEASURCHANNELS" and
"**MEASURDATA" blocks in the same file. Thus it is a good idea to define each curve in a
special pair of blocks.
However, the hereabove examples are only excerpted from a file. Copying and pasting the
examples as they are in a file will generate an error message because there is only one value in the entire column for the inclination angle. In case you only have one value for a certain parameter you must leave it out.
Coverting a TYDEX file for CarMaker
Although a TYDEX file contains all data required by CarMaker, it can’t be simply embedded
in CarMaker. The data must be transformed first. Therefore, the IPG Automotive GmbH
offers a tool called "tireutil.exe". Executing that tool two files are generated, both needed to
model a tire in CarMaker.
To execute this tool it must be located in the same folders as your TYDEX file. You can find
it in the installation folder "IPG", usually under: C:\IPG\hil\win32-versionNumber\bin. Copy
it in your current project directory in the folder FS_Generic_2017\Data\Tire where you saved
the TUTO_TYDEX_TEST.tdx.
•
Now, hit "Windows Start button > Execute". To open the command line window type
"cmd".
•
To use "tireutil.exe" you have to browse to your project folder, let’s say
C:\CM_Projects\FS_Generic_2017\Data\Tire.
In the command line window type "C:" and hit "enter". To open the respective folder
type the following line and hit "enter":
•
"C:\>cd CM_Projects\FS_Generic_2017\Data\Tire".
Figure 3.47: Windows command line
Once you are located in the right directory you have to call the "tireutil.exe" command. You
have to clarify the input file (your TYDEX file, e.g. "TUTO_TYDEX_TEST.tdx") and the output files (a file without extension and a file with the .tir extension). The name of the output
files can be different from the input file, and must be written here without extension:
C:\CM_Projects\FS_Generic_2017\Data\Tire > tireutil -if TUTO_TYDEX_TEST.tdx -of
TUTO_TYDEX_TEST -ofbin Mapping/TUTO_TYDEX_TEST.bin
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
79
Creating a tire dataset using IPGTire
•
The files generation starts (according to the tydex file weight, it can last several seconds). Once the generation is finished the command line displays:
C:\CM_Projects\FS_Generic_2017\Data\Tire>_
Figure 3.48: Initializing Tire
•
Now open your Windows Explorer and browse to the folder TIRE: you can now see in
addition to the TUTO_TYDEX_TEST.tdx a new file respectively named
TUTO_TYDEX_TEST (control file). The generated file TUTO_TYDEX_TEST.bin (data
file) directly was attached to the Mapping folder. You can close the command line window.
Figure 3.49: File directory
Exercise
Do the changes described before with your own files.
Now you have created your own tire file successfully! Open CarMaker and test the new tire:
in the "Tires" selection area you will find your new tire under the name "TUTO_TYDEX_
TEST". Select it and perform a simulation.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
80
Creating a tire dataset using IPGTire
3.5.3
TameTire
Tame Tire is a physical tire model developed by the Michelin R&D Team. The model aims
at an accurate description of the transient mechanical and thermal behaviour of the tire. It
is a part of the standard CarMaker license but it requires an additional license as well.
For detailed information about the TameTire model please refer to the TameTire documentation and the section Tire Model "Tame Tire" in the Reference Manual.
3.5.4
Tire Data Set Generator
The Tire Data Set Generator is a tool to create generic tire data sets for a specific vehicle
class and tire dimensions. The algorithm is based on the Magic Formula approach and on
the tire characteristics defined by the European Standard Tire and Rim Technical Organization (Abbreviated as ETRTO).
Based on the user inputs and the ETRTO references, the constructive parameters are
determined analytically. Measurement curves defining the tire force and torque characteristics are generated with the help of Pacejka’s Magic formula. This results are saved as
measurement curves in the TYDEX format. (See section 3.5.2 for more information about
TYDEX). Once the TYDEX file has been created, the Tire Data Set Generator calls the
tireutil application to convert the TYDEX file into an infofile and a binary file that can be used
by the CarMaker.
The Tire Data Set Generator is available in the File menu of the Tire Data Set Editor. Figure
3.44 describes the path for accessing the Tire Data Set Generator.
Figure 3.50: Opening the Tire Data Set Generator
Formula CarMaker Tutorial
Version 2.3
Parametrization - Vehicle
81
Creating a tire dataset using IPGTire
This additional Tyre Model generator will help the Formula Student teams achieve a near
about real Tire model for achieving realtime results in their simulations. This is achievable
because the Tire parameters are generated by refering the user input data and the reference ETRTO tire model. The user input data includes the Tire stiffness, Kinematic and
Nominal Tire radius, Lateral and Longitudinal Tire forces etc.
For further information please refer Tire Model "Tire Data Set Generator" in the User’s
Guide.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
82
Formula Student Electric
Chapter 4
Parametrization - Electric Race Car
4.1
Formula Student Electric
In the current CarMaker versoin, there are basically two different possibilities to create an
electric drivetrain.
Firstly, you can parameterize your electric powertrain directly in the CarMaker GUI. Again
you have the choice to create your own powertrain or to modify one of the example vehicles
(Rear Wheel Drive (RWD) or All Wheel Drive (AWD)) from the "FS_Generic_2017" project
folder. The electric powertrain model in CarMaker gives the possibility to simulate one to
four electric motors. Beside the motor and driveline characteristics, the operation strategy
and the power supply are defined directly in CarMaker. In order to test your own controllers,
it is possible to substitute or expand the predefined control units with Matlab/Simulink models.
Secondly, you can use the CarMaker interface to Matlab/Simulink. You can create your own
electric drivetrain model in Matlab/Simulink and deactivate the IPG powertrain model in the
vehicle data set as shown in our example "FS_Generic_XWD_5.1". The basic idea of the
FSE_RaceCar is that the generic powertrain is substituted with a modified electric powertrain modeled in Simulink. You are free to design a model with one, two or even more electric motors.
Furthermore, the Simulink environment is a very convenient way to develop driver assistance systems like a simple traction control or an advanced Torque Vectoring model. Of
course, this can be combnined with the first approach of parameterizing the electric powertrain in the CarMaker vehicle data set, too.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
83
Electric Powertrain Model in CarMaker
4.2
Electric Powertrain Model in CarMaker
The powertrain model in CarMaker gives the possibility to create an electric powertrain with
one to four electric motors. The best way to start the parameterization of your electric powertrain in the CarMaker GUI is to adapt the FS_RaceCar_5.1_electric*" example models as
they come with all elements required for a Formula Student Electric race car.
The project folder FS_Generic_2017 contains two example vehicles with an electric powertrain model in CarMaker. The data set "FS_RaceCar_5.1_electricRWD" is rear wheel driven and vehicle called "FS_RaceCar_5.1_electricAWD" comes with an all wheel drive. The
selected settings for the electric powertrain are described in the following.
If you want to create an own electric powertrain from scratch, we highly recommend to carefully read the Powertrain section in the CarMaker Reference Manual (accessible via CarMaker main GUI > Help > Reference Manual). In this case, you should start with selecting
a pre-defined template with right-click in the powertrain dialog. For a pure electric powertrain, select "Electrical" and the number of electric motors. The number of Drive Sources
corresponds to the number of electric motors and the parameterization of the Control Units
is adapted to an electric powertrain.
Figure 4.1: Selecting a template powertrain configuration with right-click
4.2.1
Drive Sources
Each electric motor is parameterized as one so called "Drive Source". Besides the characteristics of the motor, each Drive Source contains a gearbox and a clutch model. The gearbox and the clutch are modeled the same way as for a combustion engine described in
chapter 3.4.8. If the powertrain does not include a gearbox and a clutch for each motor, but
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
84
Electric Powertrain Model in CarMaker
has only one fixed transmission as it is common in Formula Student cars, it is possible to
define only one forward gear in the gearbox (without reverse gear!).
The specification of only one forward gear has a special treatment in CarMaker: The clutch
is disabled internally and CarMaker considers a rigid connection between the motor shaft
and the gearbox.
The electric motor requires some general information like inertia or the voltage level, which
describes to the circuit used for the motor (high voltage or low voltage).
Figure 4.2: Powertrain - Electric Motor Mapping via look-up table
There are two ways to define the torque mapping. The maximum torque curve can be either
parameterized by characteristic values or as a look-up table as shown in figure 4.2. The
meaning of this characteristic values is shown in figure 4.3.
Figure 4.3: Powertrain - Electric Motor Mapping via characteristic values
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
85
Electric Powertrain Model in CarMaker
In order to prevent an unstable situation when switching from motor mode to generator
mode, the generator torque curve should start at the point 0 rpm/0 Nm.
Both, the motor and generator characteristics should be specified with absolute values.
CarMaker internally handles the sign.
Finally, each motor’s efficiency can be defined as a single value or a look-up table in the
"Efficiency" tab.
4.2.2
Driveline
There are several Driveline models available in CarMaker. For an electric powertrain with
more then one drive source, the Driveline model "Universal drive" should be selected.
Figure 4.4: Powertrain - Universal drive
As shown in figure 4.4, the "Universal drive" model provides several options to apply the
drive source torque at:
•
Torque Input: Wheels
The Drive Source is directly connected to the wheels, the driving torque is supported by
the wheel carrier. This is the recommended mode for Formula Student Electric cars.
•
Torque Input: Driveshafts
The Drive Source is connected to the wheel by a shaft, the riving torque is supported
by the vehicle body.
•
Torque Input: Differential
The Drive Source is connected to the axle’s differential.
Furthermore, the different Drive Sources (electric motors) can be assigned to a wheel.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
86
Electric Powertrain Model in CarMaker
4.2.3
Control Units
Control Units are responsible to manage the Drive Sources and the Power Supply. There is
only one control unit for all components of the same kind:
•
Engine Control Unit (ECU) --> combustion engine
•
Motor Control Unit (MCU) --> electric motors
•
Transmission Control Unit (TCU) --> gearboxes and clutches
•
Battery Control Unit (BCU) --> batteries of power supply
The Control Units have two main tasks: The evaluation of the current state of the component and the regulation of the electro mechanic components in order to reach the target values (e.g. target torque for motor) provided by PTControl.
The PT Control unit is the superordinated powertrain control strategy.
The control model "Electrical" comes with a typical control strategy for an electric powertrain. This operation strategy is described in the following. If further functions are required,
it is also possible to replace the control strategy by a model extension via Matlab/Simulink,
an FMU or C-code. An example for such a control strategy created in Matlab/Simulink with
torque vectoring and traction control is shown in section 4.4.1.
Figure 4.5: Control Units in the Powertrain dialog
PT Control
The PT Control is the main control model of the powertrain. It manages the vehicle operation machine, the battery, the interpretation of the gas pedal and the regeneration.
In case of an electric vehicle, you should always use the control model "Electrical". It automatically deactivates the PT Control features, which are not needed for an electric drivetrain.
The battery management in tab "General" controls the batteries state of charge by assigning torques to the electric motors and by managing the energy transfer between the electric
circuits. It can be deactivated if not needed and is an optional feature. The "Operation State
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
87
Electric Powertrain Model in CarMaker
Machine" handles the vehicle operation state based on pedal and key position/start-stopbutton activation. IPGDriver is adapted to the "Generic" Operation State Machine and thus
this setting should be left untouched. For detailed information on the controller parameters,
take a look at the Reference Manual at chapter "PTControl".
The interpretation of the gas pedal position is defined in the "Gas" tab. It can either be linear
relation defined by characteristic values or nonlinear with a look-up table.
The "Regeneration" tab provides the two most common operation strategy models for electric vehicles: Regenerative braking and regenerative drag. For both strategy modes, the limits for entering or leaving the strategy mode must be defined. The meaning of this limits are
shown in figure 4.6 and figure 4.7. The regenerative brake mode itself is defined in the brake
model (see chapter 3.4.7).
Figure 4.6: Powertrain - Conditions on target torque
Figure 4.7: Powertrain - Conditions on SOC and vehicle speed
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
88
Electric Powertrain Model in CarMaker
Transmission Control Unit (TCU)
The TCU functionality is similar to the explanation for the combustion engine in chapter
3.4.8. If there is only one static gear defined in the gearbox, the TCU can be deactivated by
selecting "-not specified-".
Motor Control Unit (MCU)
The MCU model "Basic" sets each motor’s load and determines its maximum motor and
generator torque at the actual rotation speed. For more information on the P/I values of the
torque and speed controller, please take a look at the Reference Manual at chapter "Control
Units > Engine Control Unit (ECU)".
Battery Control Unit (BCU)
The BCU calculates the state of charge (SOC) and state of health (SOH) of the batteries.
It tries to keep the batteries state of charge at the target value by applying additional generator torques to electric motors if engine is on or by controlling the energy transfer between
low voltage and high voltage 1 electric circuit. The energy can be transferred between a
maximum of three circuits: A low voltage circuit and up to two high voltage circuits.
This control unit is optional. Choose "BCU Model: Low Voltage + High Voltage 1" for your
race car.
4.2.4
Power Supply
The main task of the power supply model is the accounting of the electrical power flow to
and between the electric circuits. It contains the auxiliary consumers and optionally converters between the low voltage (LV) and high voltage (HV) circuits and the battery models.
Since most Formula Student cars do not use a converter, it can be deactivated by entering
0 kW as the maximum power.
Figure 4.8: Settings of the Power Supply module
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
89
Electric Powertrain Model in CarMaker
Battery Model
The Battery model is based on an electric battery model combined with a characteristic
curve to introduce the influence of state of charge (SOC) on the idle voltage. The HV and
LV batteries are modeled with a Chen model. It consists of two RC-circuits and a single
resistance that are connected in series as shown in figure 4.9.
Figure 4.9: Powertrain - Chen Model
The dependency of an ideal voltage source on the batterie’s SOC can be parameterized via
a look-up table. The battery’s SOC is not allowed to drop below the minimum state of charge
or to exceed the maximum state of charge
You can find more information on the battery model in the Reference Model in chapter "Power Supply > Battery".
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
90
The "OpenXWD" Model
4.3
The "OpenXWD" Model
To get started with CarMaker and Simulink you should read the chapter 9 in our Quick Start
Guide (to be found in the CarMaker main GUI under Help) beforehand. Do not forget to
choose "src_cm4sl" from the project folder "FS_Generic_2017" as your "Current Directory"
in Matlab. There you find some files which are related to the FSE race car example:
•
FSE_OpenXWD_StandAlone.mdl
The whole generic CarMaker powertrain model is replaced. Instead the powertrain kind
’OpenXWD Stand Alone’ is activated. The driving torque is generated by the Simulink
model which includes two electric motors and a traction control.
•
FSE_Parameters.m
The m-file initializes all the needed parameters and characteristics for all Simulink models.
•
FSE_Define_MotorCharacteristic.xls
This is an Excel sheet (version 2003 or newer) to generate motor characteristics.
•
FSE_M85.txt
This text file includes a motor characteristic with a maximum torque of 85 Nm.
•
FSE_M100.txt
It is a motor with a maximum torque of 100 Nm.
To run the Simulink model, the OpenXWD powertrain model need to be chosen in the vehicle data set. The example vehicle "FS_RaceCar_XWD_5.1" already includes the necessary settings.
To start CarMaker for Simulink please make sure that the Matlab script "cmenv.m" was run
successfully. It adds several paths to the current Matlab session, which give access to the
extended Matlab functions and Simulink blocksets provided by CarMaker. In case you did
not install CarMaker in the default installation folder C:\IPG, the execution of the cmenv.m
script will result in an error. Please adapt the CarMaker installation path in the cmenv.m
script. In line 6 the path to your IPG installation folder needs to be specified.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
91
The "OpenXWD" Model
4.3.1
Powertrain based on "OpenXWD" model
With the powertrain model "OpenXWD" and the option "With Engine" or "With Motor" it is
nearly the same like "Generic", but the connection from the gearbox output to the wheels is
cut and has to be modeled by the user (e.g. in Simulink). The option "Stand Alone" deactivates every component of the CarMaker powertrain. All required quantities and parameters
(from generating torque right up transmitting it to the wheels) need to be calculated by an
external program (e.g. Simulink).
Figure 4.10: Powertrain OpenXWD
More detailed information about the powertrain models can be found in the Reference Manual, section "Powertrain".
4.3.2
General remarks to the Simulink models
Generally you can manipulate or overwrite signal in CarMaker from Simulink. With using the
pre-defined CarMaker interface blockset (available in the "CarMaker4SL" library) you have
easy access to manipulate/overwrite quantities. Thereto use the "Read CM Dict" block to
read the current value and the "Write CM Dict" block to overwrite the variable you like. But
remember, when you overwrite a quantity calculated in CarMaker (also called UAQ) you
influence the variable in the whole CarMaker and Matlab/Simulink workspace. To get an
overview about the quantities look at the Reference Manual, chapter "User Accessible
Quantities".
In addition, you can also create your own variables. Thereto use the "Define CM Dict" block.
For integrating your self-defined quantities in a Simulink model, please use the "Read/Write
CM Dict" blocks again. More information can be found in the Programmer’s Guide, section
"CarMaker for Simulink > The CarMaker Interface Blockset".
Figure 4.11: Simulink Dictionary
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
92
The "OpenXWD" Model
4.3.3
OpenXWD Example
The "FS_Generic_2017" project folder includes a Simulink model for the Formula Student
Electric competition (FSE_OpenXWD_StandAlone). It uses the OpenXWD interface and
has two electric motors at the rear axle combined with a traction control.
.
Figure 4.12: Simulink Model
With the OpenXWD interface you are very flexible in designing your own powertrain model,
because every pre-defined component (e.g. clutch, gearbox, differential...) is deactivated.
The basic concept of this model is actually pretty simple: CarMaker expects a drive torque
at the wheels. It is up to the user’s model extension, how this torque is generated. The wheel
integration is done on CarMaker side and it returns the current wheel speed.
To activate the OpenXWD driveline model, select the "Powertrain Model: OpenXWD" in the
vehicle data set editor (see figure 4.10) or select our example vehicle data set
"Examples_FS/FS_RaceCar_XWD_5.1". Without any model extension, the vehicle will not
drive in this configuration.
The interface variables required to transmit a drive torque from your model extension to
CarMaker are called "PT.W<position>.Trq_Drive". For this, the Simulink model extension is
used.
Additional Parameters in the Vehicle data set
Please note, that the Open_XWD prowertrain model only replaces the electrical and
mechanical components of the drivetrain. It still uses the preimplemented powertrain controller models (see section 3.4.8).
To make an Open_XWD model run, you first need to select a suitable PTControl unit. For
an electric FS race car we recommend the PTControl unit "Electrical". This unit needs some
information about the powertrain model. This parameters can be provided in the vehicle
data set under "Misc > Additional Parameters". In our example we want to avoid any interference by PTControl unit which is why we reduced the information provided to the PTC.
T h e m i n i m u m s e t o f r e q u i r e d p a r a m e t e r s i s d e f i n e d i n t h e ex a m p l e
"FS_RaceCar_XWD_5.1":
Table 4.1: Additional Paramaters for PTControl with Open XWD model
Parameter
Value
Description
PowerTrain.PTKind
BEV
Definition of the powertrain kind (electric)
PowerTrain.nGearBoxM
1
Number of gearboxes used
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
93
The "OpenXWD" Model
Table 4.1: Additional Paramaters for PTControl with Open XWD model
Parameter
Value
Description
PowerTrain.nMotor
1
Number of electric motors used
PowerTrain.GearBoxM.ClKind
Closed
No gearbox used
PowerTrain.GearBoxM.GBKind
NoGearBox
Only fix transmission (no shifting by
IPGDriver)
PowerTrain.GearBoxM.iBackwardGears
1
Transmission ration of reverse gear
PowerTrain.GearBoxM.iForwardGears
01
Transmission ration of forward gears
PowerTrain.Motor.Gen.TrqMap
00
00
Torque map of electric motor (set to zero
as defined in the Simulink model separately)
Open_XWD Powertrain model
Drive Torques
Rear left/right
Rotational speed
rear wheels
Transmission
factor
Mean value
rotational speed
Operation State:
Drive
Figure 4.13: Simulink Powertrain of FSE_OpenXWD_Standalone model
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
94
The "OpenXWD" Model
Gas Pedal
The function of this subsystem is both to initialize the signal "Vhcl.Ignition" (enables to
switch off the ignition during simulation) and to read out gas pedal position for the motor
characteristic.
Figure 4.14: Simulink Gas Pedal
E-Gas / E-Motor
Firstly, this block includes with the "E-Motor Mapping" the heart of the electric powertrain.
There you can load your own motor characteristics (more details in section 4.4.2) into the
system. The PT1 transfer functions should give the system a plausible step response. Here
you can also change the fixed transmission factor but do not forget to adapt these factors
in every block.
Figure 4.15: Simulink E-Gas / E-Motor model
Secondly, the calculation of the rotational speed (blocks: Rotation RL/RR) from each of the
motor shafts is done. The calculation includes a transmission factor and a unit change from
revolutions per second in rpm.
Figure 4.16: Calculation of engine speed
Lastly, you will find the "Electronic Gas Pedal" block. This subsystem determines whether
the gas pedal value from the driver or a control system (e.g. traction control) will be used.
It can serve as an interface for your own control system by simply exchanging the model.
The model includes a very simple traction control for each of the driven wheels.
When the variable "TC_On" equals one in the parameter file (FSE_Parameters.m) the traction control is activated, it can be deactivated by entering zero.
The traction control (short: TC) monitors the current slip in longitudinal direction and the gas
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
95
The "OpenXWD" Model
pedal values. When the slip increases too fast the TC sets the electronic gas pedal into a
waiting position (mode 1). When in the following time the slip oversteps a threshold,
mode 2 will be activated and the gas pedal will automatically be decreased (linear). In mode
0 the TC simply decides whether an increasing gas pedal value comes from the driver or
from a linear curve to accelerate the car.
Figure 4.17: Simulink Electronic Gas Pedal model
4.3.4
Parameter File
The parameter file "FSE_Parameters.m" should be loaded into the Matlab workspace once
before you start a simulation. On the one hand the file initializes the necessary motor characteristics and on the other hand the parameters for the traction control (OpenXWD model)
are defined. It also contains the parameters for the Recuperation- and Torque Vectoring
model.
Table 4.2: Parameters in FSE_Parameters.m
Parameter
Unit
Description
i_Diff
[-]
factor for a mechanical transmission
TC_On
[-]
turn traction control on or off by setting
this parameter to 1 or 0
TC_Dericative
[-]
treshold traction control mode 1
TC_Relay_On
[-]
maximum allowed longslip
TC_Relay_Off
[-]
minimum allowed longslip
TC_Incr_Gas
[-]
increasing electronic gas pedal (mode 0]
TC_Decr_Gas
[-]
decreasing electronic gas pedal (mode 2)
TV_On
[-]
turn torque vectoring on of off by setting
this parameter to 1 or 0
TV_Override
[-]
increase the torque applied to outer
wheels in corners
eta_Gen
[-]
efficiency of the electric motor in generator mode.
Gen_Loss
[-]
braking torque loss due to time needed to
build up strator load
Brake_Pedal_Travel
[-]
defines how much of the brake pedal
travel is allowed for pure recuperational
braking
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
96
Adaption of the example models
Table 4.2: Parameters in FSE_Parameters.m
Parameter
Unit
Description
Brake_Mech_Rec_Ratio
[-]
defines how much of the braking torque is
recuperational after reaching
"Brake_Pedal_Travel"
SOC_Init
[%]
initial state of charge
C_Batt
[kWh]
battery’s capacity
U0_Batt
[V]
No-load voltage of battery
R0_Batt
[Ohm]
resistance of battery
C1_Batt
[F]
capacity
R1_Batt
[Ohm]
resistance
C2_Batt
[F]
capacity
R2_Batt
[Ohm]
resistance
Every change in the file requires a re-load of the complete parameter file to the workspace.
4.4
Adaption of the example models
4.4.1
User Defined Powertrain Control Models
In case you are using the pre-implemented electric powertrain model in CarMaker as
explained in section 4.2, the control strategy for PT Control can be replaced by a user
defined control strategy. CarMaker offers different ways to implement user models such as
the C-code interface, FMUs or Matlab/Simulink. As the latter is the most popular interface
among most Formula Student teams, we will explain this approach in the following.
The FSE_TorqueVectoring.mdl in the FS_Generic_2016 project folder is an example for a
self-developed controller containing a traction control and a yaw control.
In contrast to the OpenXWD example presented in section 4.3, this model only replaces the
PTControl unit. Therefore, it is not necessary to model the entire powertrain such as the
motor or the battery model.
As shown in figure 4.18, the controller calculates a load for each motor, which is passed on
to the MCU.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
97
Adaption of the example models
Figure 4.18: PTControl - Simulink interface
There are four torque vectoring controller, one for teach wheel. In this example of a Torque
Vectoring model a higher torque is applied on the outer wheel in a corner. The yaw momentum is increased and the vehicle gets more agile. The traction control is equal to the model
explained in chapter 4.3.
In this model the maximum possible yaw rate is calculated by multiplying the friction coefficient with the gravity coefficient. This value is then divided by the current velocity of the car.
The difference between actual and maximum yaw rate is the potential for a torque increment on the outer wheel in a corner. The parameter is then added up to the motor gas input.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
98
Adaption of the example models
With the TV_Override parameter (in FSE_Parameters.m) you are able to artificially
increase the maximum yaw momentum in order to increase the parameter added up to the
motor gas. But this can lead to an unstable cornering behavior depending on the amount.
Figure 4.19: Torque Vectoring parameter calculation for the rear left wheel
In order to replace the PT Control model provided by CarMaker with a Matlab/Simulink
model, CarMaker for Simulink has to be started as explained above. Just select the example
vehicle "Examples_FS/FS_RaceCar_5.1_electric_TorqueVectoring". With any other vehice
data set, "CM4SL User Model" must be selected as the control model in the PTControl tab:
Figure 4.20: Activating a Simulink based PT Control strategy
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
99
Adaption of the example models
4.4.2
Manipulating the OpenXWD example model
This chapter explains how to implement your own motor characteristics in the OpenXWD
example model described in section 4.3.
The file "FSE_Define_MotorCharacteristic.xls" is an Excel sheet to define motor characteristics. Only the green highlighted fields should be adjusted.
Please do the following:
•
Enter the rotational speed range (in 1/min) in box 1
•
Enter the drag torque curve (in Nm) in box 2
•
Enter the full load curve (in Nm) in box 3
•
Check your entries with the torque-speed-diagram
•
Save the file as a text file (tap-stop-separated) and ignore the warnings, e.g.
FSE_M120.txt
To initialize the model with your motor characteristic please load the generated text file with
the command
load(’FSE_M120.txt’)
into the Matlab workspace (you also can extend the parameter file!). Do not forget to change
the matrix names in the 2D-Look-up-Table for the "E-Motor Mapping" (e.g. to FSE_M120).
1
2
3
Figure 4.21: Table Motor Characteristic
4.4.3
Driver Model
It is highly recommended to use the User Parameterized Driver when simulating with FS
cars. The simulations are reproducible and the driver can be adapted to needs of each disclipline.
However, if there is the need to simulate with the Race Driver there are several things which
have to be taken into account to successfully perform a Driver Adaption with a FSE Powertrain Model. The following steps have to be completed:
Step1
After opening one of the Simulink models out of MATLAB and opening the CarMaker GUI,
the TestRun can be created or loaded. You can now start a Basic Knowledge Driver Adaption. After completing the adaption and starting the simulation, you might encounter that the
vehicle drives very slowly along the defined course. In this case continue with Step 2.
Step 2
To fix this, open the ASCII-file of your TestRun out of the Windows Explorer with a text editor.
Driver.Learn.nEngine.Standard:
0 0
0 0
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
100
Adaption of the example models
0 0
0 0
0 0
Driver.Learn.vIdle = 1.000
Driver.Learn.vMax = 103.956
Driver.Learn.vG2nEng025 = 25.989
Listing 4.1: Excerpt of an ASCII-file of a TestRun
Almost at the end of the file there is a line called ’Driver.Learn.vIdle’ which defines the vehicle’s idle velocity. Set there a value greater than zero. Save the text file.
Step 3.1: Driving with the User parameterized Driver
There is also the possibility to select the User parameterized Driver instead of the Race
Driver, which is also recommended. Load the parameter set of an aggressive driver with
right-click anywhere in the window.
Figure 4.22: User parameterized Driver parameters
First it is recommended to adjust the parameters in the ’General’ area. Set ’dt. Change of
Pedals’ to a lower value and set ’Min. dt Accel/Decel’ to zero. In the Accelerations, g-g-Diagram area double the values. You can now start your TestRun. If the vehicle leaves the road
or rolls over, decrease the Acceleration parameters step by step.
Formula CarMaker Tutorial
Version 2.3
Parametrization - Electric Race Car
101
Adaption of the example models
Step 3.2: Driving with the Race Driver
If you select the Race Driver after completing a Basic Knowledge Driver Adaption and completing step 1, in some cases you will encounter that the vehicle eventually leaves the road
or rolls over. But there is a way to avoid this.
Figure 4.23: Race Driver Parameters
Decrease the acceleration factors ax decel and ay step by step and observe the results.
Optimize these factors so that the vehicle stays on track but still accomplishes an acceptable lap time.
Exercise
Please open Matlab, change your current directory to "src_cm4sl" and load the parameter
file "FSE_Parameters.m" into the Matlab workspace.
Then start the "FSE_OpenXWD_StandAlone_2Motors_TC.mdl" Simulink file and open the
CarMaker GUI by double clicking on the "Open GUI" icon. Now you can choose under the
menu "File > Open" the TestRun "FSE_Acceleration_XWD_TC". This TestRun is similar to
the Formula Student acceleration competition.
Perform a simulation and monitor the quantities: Car.LongSlipRL, DM.TriggerPoint.Time,
E_Gas_RL, VC.Gas and PT.WRL.Trq_Ext2W with IPGControl.
After the first TestRun please switch off the traction control. Thereto open the parameter file
and set the variable "TC_On" to zero. Re-load the file into the workspace, perform a second
TestRun and compare the results.
Formula CarMaker Tutorial
Version 2.3
Model Validation
102
Introduction
Chapter 5
Model Validation
5.1
Introduction
Any pre-existing or self-generated vehicle can’t serve as reference as long as it hasn’t been
validated. This is due to the many estimated assumptions and potential mistakes probably
made in the parameterization process.
Before starting with the real model validation a few plausibility checks should be performed
to eliminate fundamental input errors. In that context, the suspension models and kinematics results should be checked as well.
Once the plausibility checks are completed the validation process can be started. To which
extent it is practiced, mainly depends on the available time, equipment and budget. If the
just mentioned resources can’t be provided in a sufficient degree, the accuracy of measurements should have a higher priority than the quantity of measurements. Moreover, in that
case, even more attention should be paid to the plausibility checks.
Formula CarMaker Tutorial
Version 2.3
Model Validation
103
Plausibility checks of axle models
5.2
Plausibility checks of axle models
5.2.1
Variation of camber and inclination vs. wheel travel
Constructively, the variation of the camber of an axle can be easily determined via the function of wheel travel vs. angle of inclination change (∆σ). The existing resiliences are neglected though. Concerning a double wishbone axle, both control arms (lengths e and f) move
on circular paths around the junctures on the body (C and D). If the lower juncture between
wishbone and suspension is lifted or lowered by the distance s1, the actual inclination
change (respectively the actual angle of inclination change) can be determined. In case of
a double wishbone axle, the angle of inclination change is the same as the angle of camber
change and thus the camber angle can be estimated at the same test.
Figure 5.1: Determination of the angle of inclination and camber change. [RB00]
The process explained above needn’t be done with drawings but is a lot more precise using
CAD programs. Therefore, all kinematic points are inserted into a sketch. Then, the lengths
of the connecting lines and the two junctures of wishbone and chassis are fixed. Modifying
the point "Lower Wishbone - Suspension" the compression can be simulated.
Figure 5.2: CAD sketches of a suspension.
Formula CarMaker Tutorial
Version 2.3
Model Validation
104
Plausibility checks of axle models
Table 5.1: Camber and toe change.
wheel travel s1
camber
measured
camber
calculated
inclination
measured
inclination
calculated
relative
error
30 mm
-1.61 deg
-1.46 deg
16.26 deg
16.26 deg
0.00%
25 mm
-1.07 deg
-1.20 deg
15.99 deg
15.86 deg
0.82%
20 mm
-1.61 deg
-0.95 deg
15.71 deg
15.60 deg
0.71%
15 mm
-0.79 deg
-0.71 deg
15.44 deg
15.36 deg
0.52%
10 mm
-0.52 deg
-0.47 deg
15.17 deg
15.12 deg
0.33%
5 mm
-0.26 deg
-0.23 deg
14.91 deg
14.88 deg
0.20%
0 mm
0 deg
0 deg
14.65 deg
14.65 deg
0.00%
-5 mm
0.25 deg
0.23 deg
14.40 deg
14.43 deg
0.21%
-10 mm
0.51 deg
0.45 deg
14.14 deg
14.20 deg
0.42%
-15 mm
0.96 deg
0.67 deg
13.89 deg
13.98 deg
0.65%
-20 mm
1.01 deg
0.89 deg
13.64 deg
13.77 deg
0.95%
-25 mm
1.25 deg
1.10 deg
13.40 deg
13.55 deg
1.11%
-30 mm
1.50 deg
1.31 deg
13.15 deg
13.34 deg
1.44%
The relative error is always less than 2%. It results from the existing resiliences in the bearing which are not considered in the measurements as opposed to IPGKinematics.
5.2.2
Track change
The compression of the wheels causes a track change at almost every suspension, so do
the double wishbone axles. Thus, this track change should be checked as well. It can be
done using the sketch below. You just have to add the wheel contact point and fix the connecting line of the two junctures between wheel carrier and body.
Figure 5.3: Determination of the track change. [RB00]
Formula CarMaker Tutorial
Version 2.3
Model Validation
105
Plausibility checks of axle models
5.2.3
Toe change
A change in toe angle due to the compression of the wheels can be used to achieve certain
driving characteristics. In general, the toe change should be in the range of minutes and
never above, as this leads to an unforeseeable handling of the car.
If IPGKinematics releases a nearly constant toe change vs. wheel travel this result is very
likely correct and a check-up isn’t compulsory. But if it’s varying or even exceeds the minutes-range the, model should be checked in any case.
Figure 5.4: Toe change vs. wheel travel
If you have such a remarkable toe change as shown in the diagram above the idea suggests
itself that there is a mistake in the model parameterization. Of course, this is not unlikely
and you should check your model carefully. Pay attention in particular to the coordinates of
the wishbones, the axle journal and the tie rod. If you can’t find any mistake in your model,
you should ask the question, if the calculations may be incorrect. The result is absolutely
unsatisfactory, but constructively possible! To check this out, a measurement should be performed directly on the car.
To avoid the compression inducing forces, the car is jacked up and the wheels are disconnected from the spring/damper unit. Before doing so, the wheels should be put on a vertically adjustable platform thus the wishbone bearings needn’t carry the whole self-weight.
With the use of an angle plate it is now possible to measure the true toe angle.
As the tire deflects at the footprint it is wider in that area. For that reason the angle plate
should be attached to the rim and never to the tire. But therefore, the angle plate must feature distance plates to equate the distance between rim and tire. The following figure shows
such an angle plate.
Formula CarMaker Tutorial
Version 2.3
Model Validation
106
Plausibility checks of axle models
Figure 5.5: Angle plate used to measure the toe angle.
Via lifting and lowering the plate under the tire, the compression can be simulated and the
corresponding toe angle can be measured using the angle plate. During the measurements
it is important to fix the steering to prevent influences of steering angle.
After measuring the toe angle directly on the car the results can be compared with the calculations. If both values are the same your model is correct. However, it should be modified
urgently. This can be done by adjusting the steering system, respectively the position of the
tie rod. Further explanations on this can be found in the following paragraph.
5.2.4
Steering angle/Steering ratio
After checking the toe change, the steering system should be looked closely. To measure
the steering angle the same configuration as described above can be used. Another possibility is to put the roadworthy car on the ground and do the measurements right there. If the
driver was included in the former calculations of the design position, this second variant
should be chosen in any case to prevent errors.
Once the car is on the ground, firstly the steering gear ratio should be verified. Therefore,
the best way is to give a certain steering angle and measure the corresponding rack travel.
To verify the result, the test can be performed in the other direction once again.
After checking the steering ratio, the steering angle is next. For this purpose you can avail
yourself of the angle plate once more. It is attached to the rim again. Once you marked the
reference line, the steering angle (or the rack travel) can be increased step by step while
recording the corresponding steering angles at the right and left side.
Formula CarMaker Tutorial
Version 2.3
Model Validation
107
Plausibility checks of axle models
5.2.5
Turning track diameter
The turning track diameter is the circular arc being followed by the outer wheel contact point
at fixed steering angle. It is quite common to refer to the smallest possible arc as turning
track diameter. It is attained by applying the maximum steering angle. Hence, measuring
the turning track diameter means in general checking the steering angles. For this procedure, a driver isn’t required. It is sufficient to fix a certain steering wheel angle or a steering
rack travel and then pushing the car on that circular path. In this manner it is a lot easier to
maintain a given steering angle than it was in a driven car.
Table 5.2: Checking the turning track diameter.
5.2.6
steering rack
travel
turning track diameter
measured
turning track diameter
calculated
relative error
0 mm
infinite
infinite
0.00%
5 mm
69.00 m
68.12 m
1.29%
10 mm
34.50 m
34.06 m
1.29%
15 mm
23.00 m
22.71 m
1.28%
20 mm
17.20 m
17.05 m
0.88%
25 mm
13.80 m
13.65 m
1.10%
30 mm
11.60 m
11.39 m
1.84%
35 mm
10.00 m
9.78 m
2.25%
40 mm
8.80 m
8.58 m
2.56%
Anti-dive and anti-squat
While braking, the front axle compresses by the distance ∆sf and the rear axle by the distance ∆sr. The pitch angle ϕ [rad] can be calculated out of the two distances and the wheelbase l:
∆s f + ∆s r
ϕ = ----------------------l
(EQ 39)
The skewing of the rods due to compression can be reduced by a double wishbone axle. In
case the brake is located outside the wheel, the wishbones must be twisted to each other
to countervail the emerging forces. However if the brake is located centrally at the differential, the wishbones must be skewed in the same rotational direction.
If the wishbones are orientated parallel there is no anti-dive or anti-squat.
Formula CarMaker Tutorial
Version 2.3
Model Validation
108
Plausibility checks of the vehicle dataset
5.3
Plausibility checks of the vehicle dataset
5.3.1
Center of gravity and moments of inertia
In section 3.4.1 the determination of the vehicle’s center of gravity was treated in detail. If
the process of determination wasn’t performed as carefully as described in that chapter, the
results should be investigated once again. The generated tcl-chart can serve as a rough
approximation. Here, the entered points for the single centers of gravity should be placed
at proper positions. To check the dimensions of the moments of inertia, each part should
be replaced by a similar geometric body whose moment of inertia can be determined exactly. Therefore, simple bodies like rectangles, cylinders, hollow cylinders or balls are mostly
sufficient.
5.3.2
Comparability of IPGKinematics and CarMaker
A few parameters are required by both programs, IPGKinematics and CarMaker, including
amongst the other parameters like stabilizer bar front/rear, spring rates and spring characteristics front/rear, masses and axle loads. Each of these parameters should have the same
value in both programs. Most of the parameters are declared equally in both programs. The
only exception is the stabilizer bar. It is defined in different terms whose translation was
explained in section 3.4.4.
5.3.3
Assignation of the spring length l0 at front and rear axle
In section 3.4.4 the spring rates for front and rear axle were entered but the spring lengths
l0 have still been left out for the following reason. If you chose a linear kinematic model the
length l0 serves as adjustment parameter. Using non-linear models, the length l0 is the
actual free length of the spring. The determination of this parameter is done via the static
equilibrium configuration of the vehicle. To perform an equilibrium calculation you can use
the CarMaker "Model Check" (CarMaker main GUI: "Simulation > Model Check", see section "Model Check"). With this tool the user can create and analyze all car specific diagrams.
One amongst the others is the analysis of the static equilibrium configuration. To activate
this tool, deselect all options except "Vehicle Characteristics". With having activated both
options in this section the tool can be started hitting the "Generate Diagrams" button. After
completing the calculations a text file opens containing the results. At the beginning of this
file all important input parameters are listed. At the end of this file you can find the results
of the static equilibrium calculation. The following shows an excerpt of such a file which contains the results of the static equilibrium calculation.
Formula CarMaker Tutorial
Version 2.3
Model Validation
109
Plausibility checks of the vehicle dataset
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:
39:
40:
41:
42:
43:
44:
45:
46:
47:
48:
49:
50:
51:
52:
53:
54:
55:
56:
57:
58:
59:
60:
61:
62:
63:
64:
### Geometry (equilibrium or start-off configuration)
:
:
:
:
x
1.383 m
1.383 m
2.386 m
:
:
:
:
1.000
0.000
0.229
0.000
GenBdy1
:
:
:
1.314 m
1.314 m
2.315 m
-0.000 m
-0.000 m
-0.000 m
0.316 m FrD
0.316 m Fr1
0.293 m Fr0
ConBdy1
:
:
:
1.334 m
1.334 m
2.335 m
0.000 m
0.000 m
-0.000 m
0.328 m FrD
0.328 m Fr1
0.305 m Fr0
VhclPoI
Fr1
Fr1
Fr1
Fr1
Origin
Roll
Pitch
Yaw
y
0.000 m
0.000 m
-0.000 m
z
0.529 m FrD
0.529 m Fr1
0.506 m Fr0
m
0.000 m
deg Fr0.X
deg Fr0.Y
deg Fr0.Z
-0.018 m Fr0
:
FL
carrier WC tx : 2.2667206 m
ty : 0.6049116 m
tz : 0.2678416 m
FR
2.2667206 m
-0.6049116 m
0.2678416 m
RL
0.4999997 m
0.6310333 m
0.2616688 m
RR
0.4999997 m FrD
-0.6310333 m FrD
0.2616688 m FrD
carrier WC tx : 2.2667206 m
ty : 0.6049116 m
tz : 0.2678416 m
2.2667206 m
-0.6049116 m
0.2678416 m
0.4999997 m
0.6310333 m
0.2616688 m
0.4999997 m Fr1
-0.6310333 m Fr1
0.2616688 m Fr1
carrier WC tx : 3.2677741 m
ty : 0.6049116 m
tz : 0.2409331 m
3.2677741 m
-0.6049116 m
0.2409331 m
1.5010427 m
0.6310333 m
0.2418293 m
1.5010427 m Fr0
-0.6310333 m Fr0
0.2418293 m Fr0
-0.0000003 m
0.0000333 m
-0.0003271 m
-0.0000003 m Fr1
-0.0000333 m Fr1
-0.0003271 m Fr1
-0.0003483 -0.0003483 0.1426429 m
0.1003696 m
0.0003271 m
0.0000000 -
-0.0003483 -0.0003483 0.1426429 m
0.1003696 m
0.0003271 m
0.0000000 -
carrier Mnt tx: -0.0002794 m
ty : -0.0000884 m
tz : 0.0008458 m
0.0009741 -0.0000000 0.1751192 m
0.0989997 m
-0.0008458 m
0.0000000 -
-0.0002794 m
0.0000884 m
0.0008458 m
compression q0
coordinate q1
spring coord
damper coord
buffer coord
stabi coord
:
:
:
:
:
:
camber
: -0.0140927 deg
: -0.8455619 min
-0.0140928 deg
-0.8455700 min
0.0159658 deg
0.9579481 min
0.0159656 deg
0.9579378 min
toe
: -0.1664832 deg
: -9.9889940 min
-0.1664846 deg
-9.9890780 min
-0.0000944 deg
-0.0056652 min
-0.0000944 deg
-0.0056651 min
caster
: -0.0390493 deg
: -2.3429591 min
-0.0390497 deg
-2.3429791 min
0.0000424 deg
0.0025417 min
0.0000424 deg
0.0025417 min
wheel center Fx : -2.7001 N
Fy : 0.2095 N
Fz : 813.3719 N
wheel road
Fx : 0.0000 N
Fy : -0.0000 N
Fz : 813.3764 N
0.0009741 -0.0000000 0.1751192 m
0.0989997 m
-0.0008458 m
0.0000000 -
-2.7001 N
-0.2095 N
813.3721 N
-3.8067 N
-0.2650 N
951.2038 N
-3.8067 N Fr1
0.2651 N
951.2054 N
0.0000 N
0.0000 N
813.3767 N
0.0000 N
0.0000 N
951.2114 N
0.0000 N FrH
-0.0000 N
951.2131 N
-------------------------------------------------------------------------------
Formula CarMaker Tutorial
Version 2.3
Model Validation
110
Plausibility checks of the vehicle dataset
In the middle of the last paragraph of the "Model Check" result file, there is a point called
"carrier Mnt". Using a non-linear model the variable "tz" in the "carrier Mnt" section should
be approximately zero for all four wheels. To achieve this the front and rear spring lengths
must be modified. After each change of l0 a new "Model Check" can be performed until tz
is adequately small.
If the parameter was not adjusted, the whole static equilibrium configuration of the car is
wrong. It expresses whether the car is running under the track surface or well above it. It
can be easily visualized with IPGMovie. The following picture shows a vehicle without any
adjustment of the spring length and a car with a correct value for l0.
Figure 5.6: Vehicle in a wrong equilibrium state.
Figure 5.7: Vehicle with a correct spring length l0.
Formula CarMaker Tutorial
Version 2.3
Simulation
111
Initial start-up of the model
Chapter 6
Simulation
6.1
Initial start-up of the model
6.1.1
First simulation and common error messages
Once you finished the plausibility checks and the spring length configuration, the actual
model validation can be started. The primary step should consist of a first general simulation. The performed TestRun should be as simple as possible to emphasize the car itself.
For the first TestRun the following settings should be chosen:
•
Road: a long straight with a track width of 10 m,
•
Driver: standard driver set to "normal",
•
Maneuver: a maneuver duration of 100 s,
•
Tire: Formula Student tire "FS_195_50R13" (front) and "FS_205_50R13" (rear).
This test run’s target is to make the car drive straight along the road. If this is the case right
at first go, the remaining part of this chapter can be skipped. However, in the most cases
an error message will occur. In the following topics, the most common error messages and
their solutions are exemplified. Moreover, at the end of this chapter it will be dwelled on how
to perform an efficient fault isolation in case the error can’t be found straightforward.
"Suspension front left: Wheel and carrier must have the same position"
As explained in section 3.4.1 the center of gravity for the wheel must be the same as that
for the wheel carrier. If all four centers of gravity are different, a simulation can’t be executed.
If the centers of gravity of only three of the four wheels are different, the simulation starts
but delivers three error messages. This can be checked out in the session logbook ("Simulation > Session Log"). Here, all warnings and error messages of the current session are
stored. Once CarMaker is restarted, a new session opens.
After correcting the positions of centers of gravity of the wheels this error won’t occur again.
Formula CarMaker Tutorial
Version 2.3
Simulation
112
Initial start-up of the model
"Wrong number of elements or syntax error in
’PowerTrain.GearBox.iBackwardGears’..."
Again, this is a simple faulty insertion. As mentioned in section 3.4.8 "Powertrain: Gearbox"
a reverse gear must be defined, although Formula Student cars usually don’t have one.
"Can’t get parameters for body sensor ’Jack.fr’"
The actual problem is similar to the non-existing reverse gear. The program needs one point
for all four jack sensors. It is possible to place all four points in the origin.
"Suspension KnC front left: No kinematics selected, model number 0"
Here, the existing model is correct in the most cases. The only problem is that the selected
front axle kinematics is actually a rear axle kinematics. This mistake can easily happen
when selecting the skc-files and later on it is read over. If you choose the right skc-file this
problem will be solved.
"Suspension KnC ’MapNL’ rear left: damper length is not decreasing
monotonously (0.071741 (0,6) .. 0.0758616 (1,6))"
With this error in the session logbook a wrong value was entered in the kinematics spec.
The indicator "rear" (respectively "front") shows the user at once in which skc file he has to
search. As the damper length doesn’t increase constantly, the mistake must be at the coordinates of the damper. Along with this error, similar error messages often exist which tell
you, the spring length doesn’t increase constantly, either. Here, the problem lies in the definition of the spring/damper elements. In Formula Student cars Push-/Pullrods are mainly
used. On that reason the parameters "Damper - Body", "Damper - Lower Wishbone",
"Spring - Body" and "Spring - Wheel Suspension" might not have been considered or set to
"zero". In section 3.3.5 it was pointed out that these parameters must have sensible values,
nonetheless. If this wasn’t taken into account an error emerges.
Fault analysis and fault isolation
If you receive error messages different to those described above, a closer fault analysis
must be performed. If the error message tells you neither which parameter is affected nor
in which section the problem lies, a closer examination is required. For it, each and every
variable should be checked for a missing point or a wrong factor.
If you still don’t find any mistake, another method should be applied. CarMaker offers almost
everywhere the opportunity to import datasets from other TestRuns. In CarMaker all tabs tantamount to partial models - and even their subcases, like e.g. dampers in the suspensions tab, can be imported from other vehicle datasets (File > Import). Thus, there is the
possibility to import the data of your own car step by step into an existing, operating model
until the problem is found. However, this reference model should be similar to your car (e.g.
the Formula Student car "FS_RaceCar_5.1" introduced in this document) to avoid new
problems. In any case, different masses between the reference car and the newly generated skc-files must be evited.
Formula CarMaker Tutorial
Version 2.3
Simulation
113
Initial start-up of the model
Figure 6.1: Submenue to import vehicle data sets.
6.1.2
Driver adaption
As soon as a simulation exists, that doesn’t produce any errors or warnings, you can proceed to the next step: performing and analyzing initial TestRuns with your car. But before
doing so, a driver adaption should be implemented (Simulation > Driver Adaption). This is
not compulsory as the IPG driver learns its limits by and large, but in case of racing drivers
such as used in Formula Student cars an adaption is sensible.
During the driver adaption the user can observe if the car acts in a convenient way. If this is
not the case or if the adaption can’t even be finished, another parameter check up should
be performed. For this see the previous chapter.
Once the driver adaption is completed successfully you can start to simulate TestRuns.
.
Figure 6.2: Driver Adaption menu.
Formula CarMaker Tutorial
Version 2.3
Simulation
114
TestManager
6.2
TestManager
TestManger is the new update of Test Series. With this tool, you can automatically start several TestRuns one after another, and possibly simulate a TestRun in a loop with a variation
of an unlimited number of variables.
One possibility to do parameter variations is to define several TestRuns with different conditions, save them and perform one simulation after the other manually. The TestManager
makes this work a lot easier for you. Just select the TestRuns you have prepared by choosing Add > TestRun. Afterwards you have to select the TestRun from the library. The loaded
files are displayed in the TestManger window. Press the start button and you will see the
simulations will be performed automatically in a row. Furthermore, the TestManager provides the flexibility in selecting which TestRuns to simulate.
Don’t forget to choose the option "save all" in the Storage of Results box at each TestRun.
Otherwise the simulation will be performed, but the results will be only saved to a buffer and
thus will be overwritten at the next simulation!
6.2.1
Variations and Variable kinds
Instead of creating a new TestRun for a single variation of a quantity, you can also insert a
loop to the TestManger. This can be done with the help of inserting Variations for the Predefined quantities in the TestRuns. Just create the Variation by choosing Add > Variation in
the selected TestRun. This means, the same TestRun is been run for several times but each
time with different User defined Variations e.g. Longitudinal acceleration. In the end, once
you built an automated TestRun you can save and load it just like the normal TestRun.
Variations can be defined with the help of different variables e.g. NValue or KValue. NValue
abbr. Named Values (NV) are used to change the parameters in the CarMaker GUI e.g.
Coordinates of CoG. On the other hand KValue abbr. Key Values (KV) are used to change
the Infofile parameters which do not have an editable parameter in the CarMaker GUI e.g.
Gear Ratio.
Note: While defining the NValues in the CarMaker GUI, it is important the User gives a
default value to the parameter to avoid getting errors while simulating TestRuns without the
TestManager.
Exercise
In the following example we want to show how to prepare an automated TestRun using the
acceleration event and the Driver Weight as a variable. Please save your current work.
Open "FS_Acceleration". Change the Car to FS_RaceCar_TM. Set the Trim Load1 in Bodies Tab of Car to "$Driver_Wt=70" (notice that "=70" sets the variable to the default value
7 0 ) a n d s e l e c t " s ave a l l " fo r t h e s t o ra g e o f r e s u l t s. S ave t h e n ew f i l e a s
"FS_Acceleration_TUTO". Now start the TestManger (Simulation > TestManger). Add the
previous created TestRun "FS_Acceleration_TUTO"
Formula CarMaker Tutorial
Version 2.3
Simulation
115
TestManager
.
Figure 6.3: Set the variable
Figure 6.4: TestManger Main Window
Select "Add" ->"TestRun", then load your previous created TestRun in the field "TestRun
Description".
Add variations like shown in the picture, Type "NValue", named "Driver_Wt" with the values
"70", "85" and "100". As you will recognize the type and name will be transfered to next variations. You only have to insert the values.
Formula CarMaker Tutorial
Version 2.3
Simulation
116
TestManager
Figure 6.5: The declaration of variations
After having generated the TestSeries, you can start a simulation. If you want to save the
TestSeries’ layout, choose "File > Save As".
To compare the results open IPGControl, load the different files as mentioned in section
2.3.4. Feasible values could be "Car.Pitch" or "Car.ax".
Figure 6.6: Comparison of the saved results
Formula CarMaker Tutorial
Version 2.3
Simulation
117
TestManager
6.2.2
Criteria and Analysis
In addition to the execution of TestRun loops including parameter variations, the TestManager also provides an interface to quantify the simulations directly with the help of User
defined criterias. These are basically used to guage the Vehicle performance with respect
to set targets i.e. criterias. You can create it by choosing Add > Criterion in the selected
TestRun. figure 6.7 It is also possible to add multiple criterias for the same TestRun.
Criterias are defined by using syntax "[get Parameter]" followed by condition.
Example TestRun is considered good when the Car yaw angle is less than 6 Degrees
[get Car.Yaw] <= 6*pi/180
Note: The User Accessible Quantities always follow their default units but the TestManager
uses SI system. So it is important to convert the units into SI units whenever required. If you
are not sure about the default unit of a quantity, please have a look at the Reference Manual,
chapter User Accessible Quantities.
Note: The Parameter called in the Criteria expression always returns the value which it has
taken at the end of Simulation. Many Parameters are triggered to 0 at the end of the simulation and therefore cannot be called in the criteria function. In such cases new variable creation is advisable which can be used to take the value of such Parameters and will not
return back to 0. You can create this Variable in the Maneuver Tab of the TestRun using Minimaneuver Commands in the CarMaker GUI or by defining Characteristic (Add>Characteristic) figure 6.9 in the respective TestRun of the TestManager. Please note that the
commands in the Characteristics tab of the TestManager override the Real time expressions mentioned in the CarMaker GUI.
With the help of criterias, the TestManager evaluates if a test was successful or not and provides the User with a Visual signal which comprises of 6 different signals, each having their
own meaning. For eg. Green for successfully satisfying the said criteria or Red for signifying
that the criteria is not met. For more information please refer the UsersGuide, Chapter Test
Automation.
In addition to setting up the Criteria, the TestManager can define diagrams in a test series.
These diagrams are plotted after the simulation has come to an end and can then e.g. easily
be integrated into CarMaker’s report output for documentation purposes.There are three
different diagram modes which are supported:
•
Quantity(s) vs. Time
•
Quantity(s) vs. Quantity
•
Characteristic value vs. Variation
It is possible to plot one diagram for each variation or to summarize all variations in a single
diagram for a better overview. You can create Diagrams for the said TestRun by choosing
Add > Diagram figure 6.8. In this the User will have the flexibility to name respective axis
labels and parameters. To get the Diagram right, it is necessary to insert a User Accessible
Quantity with correct syntax.
The Test Manager also includes a report functionality which automatically generates a
report of the performed test series. This Report can be called up either when a test series
is completed or aborted by pressing the Report button in the lower right corner of the Test
Manager window. It provides detailed results of every single TestRun which are prepared
and clearly arranged fully automatically. The Report starts with an Overview of all the
TestRuns and their respective results. It also provides details of each and every TestRuns
which comprises of Diagrams, Variations, TestRun Maneuvers and Pass Fail results figure
6.10. The Report can be found Project Directory > SimOutput > Computer Name > Report
for more information see the User’s Guide Chapter "Test Automation".
Formula CarMaker Tutorial
Version 2.3
Simulation
118
TestManager
Exercise
In continuation with the previous exercise, we will now define the Criteria, Diagrams and
Characteristic in the same TestRun in the TestManager followed by Report generation. To
create a Criteria, select TestRun "FS_Acceleration_TUTO" in TestManager and Add > Criterion. Set the Criterias for Green, Yellow and Red as shown in figure given below.
Figure 6.7: Defining Criterias
To create a Diagram, Add > Diagram. Give diagram title as Longitudinal Acceleration Vs
Time. Tick the checkbox, ’Show all variations in single graph’. Provide Axis labels and User
Accessible quantity Car.ax for Y-Axis.
Figure 6.8: Creating Diagrams
Similarly define characteristics using Add > Characteristic. Add condition for 80% Gas after
4 sec. as shown in figure. After assigning Criterias, Diagrams and Characteristics, simulate
the TestRun from TestManager and generate the Report from TestManager GUI.
Formula CarMaker Tutorial
Version 2.3
Simulation
119
TestManager
Figure 6.9: Defining Characteristic
Figure 6.10: Sample Report page
Formula CarMaker Tutorial
Version 2.3
Simulation
120
TestManager
6.2.3
Example Test Series
To help Formula Student teams for testing of their Vehicle Models, IPG Team has created
a special TestSeries named "FS_RaceCar_Validation.ts". This TestSeries serves to support students understand their Car better using various static and dynamic TestRuns and
eventually optimize their Car by analysing the results of the TestRuns given in this TestSeries. The TestSeries is made up of various TestRuns which simulate the cars of Formula
Student teams by replicating the Race environment in best possible ways.
This TestSeries comprises of major 3 Groups having their own TestRuns. All these
TestRuns are explained below.
Equilibrium
1. Standstill
Objective:- To verify the static equilibrium of the vehicle with different loading conditions.
This TestRun is a goodway for students to start analysing their vehicle behaviour before
going into dynamic trails. For analyis students can opt for Toe Angle, Camber Angle and
Loading on each wheel of the car.
Table 6.1: Variables for Standstill Test
Type
Variable Name
Variable Description
Parameter Location
NV
Driver_Wt
Driver Weight
Parameters > Car > Bodies > Trim
Load 1 > Mass
NV
Fuel_Wt
Fuel Weight
Parameters > Car > Bodies > Trim
Load 2 > Mass
NV
Position_X
X Location of Fuel
Weight
Parameters > Car > Bodies > Trim
Load 2 > x
NV
Position_Y
Y Location of Fuel
Weight
Parameters > Car > Bodies > Trim
Load 2 > y
NV
Position_Z
Z Location of Fuel
Weight
Parameters > Car > Bodies > Trim
Load 2 > z
Table 6.2: Quantities to be evaluated in Standstill Test
Validation Output
User Accessible Quantities
Toe Angle
Car.ToeFL, Car.ToeRR
Camber Angle
Car.CamberFL, Car.CamberRR
Vertical Loads on all 4 Wheels
Car.FzFL, Car.FzRL, Car.FzFR, Car.FzRR
Formula CarMaker Tutorial
Version 2.3
Simulation
121
TestManager
Longitudinal Dynamics
1. Pull Test
Objective:- To check the straight line stability of the vehicle for no steering input. This
TestRun is important for Driver safety and Vehicle performance. Good result for this test
depends on CoG location, suspension and steering kinematics and overall symmetry. For
analyis students can opt for Lateral Deviation of car, Toe Angle and Camber Angle on each
wheel of the car.
Table 6.3: Variables for Pull Test
Type
Variable Name
Variable Description
Parameter Location
NV
Speed
IPG Driver Speed
Parameters > Maneuver > Longitudinal Dynamics > IPG Driver > Speed
NV
CoG_x
X Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > x
NV
CoG_y
Y Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > y
NV
CoG_z
Z Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > z
Table 6.4: Quantities to be evaluated in Pull Test
Validation Output
User Accessible Quantities
Lateral Deviation
Driver.Lat.dy
Toe Angle
Car.ToeFL, Car.ToeRR
Camber Angle
Car.CamberFL, Car.CamberRR
2. Acceleration
Objective:- This TestRun checks vehicle capability to reach 75m in the shortest possible
time when starting from standstill. To maximise the acceleration, students can change Gear
Shifting RPM and Gear ratios. For analyis students can opt for max. vehicle speed, max.
longitudinal acceleration, max. engine RPM and Pitch angle of the car.
Table 6.5: Variables for Acceleration Test
Type
Variable Name
Variable Description
Parameter Location
NV
Gas
Throttle Value (0-1)
Parameters > Maneuver > Maneuver
0 > Minimaneuver Commands
NV
Shiftup
Shifting RPM
Parameters > Driver > User Parameterized Driver > Standard Parameters
> Declutching / Gear Shifting > Engine
Speeds [RPM] > max
KV
PowerGear Ratio change for
Train.Gearall gears
Box.iForwardGe
ars
Formula CarMaker Tutorial
Path to File
/Data/Vehicle/Examples_FS/
FS_RaceCar_TM
Version 2.3
Simulation
122
TestManager
Table 6.6: Quantities to be evaluated in Acceleration Test
Validation Output
User Accessible Quantities
Vertical Loads on all 4 Wheels
Car.FzFL, Car.FzRL, Car.FzFR, Car.FzRR
Toe Angle
Car.ToeFL, Car.ToeRR
Camber Angle
Car.CamberFL, Car.CamberRR
Pitch Velocity
Car.PitchVel
Max Vehicle Speed
Car.v
Max Vehicle Acceleration
Car.ax
Max Engine RPM
PT.Engine.rotv
Max Engine Power
PT.Engine.PwrO
Pitch
Car.Pitch
Time
Time
3. Top Speed
Objective:- This TestRun checks vehicle capability to reach its Top Speed in the shortest
possible time when starting from standstill. To maximise the acceleration, students can
change Gear Shifting RPM and Gear ratios. For analyis students can opt for max. vehicle
speed, max. longitudinal acceleration, max. engine RPM and Pitch angle of the car.
Table 6.7: Variables for Top Speed Test
Type
Variable Name
Variable Description
Parameter Location
NV
Gas
Throttle Value (0-1)
Parameters > Maneuver > Maneuver
0 > Minimaneuver Commands
NV
Shiftup
Shifting RPM
Parameters > Driver > User Parameterized Driver > Standard Parameters
> Declutching / Gear Shifting > Engine
Speeds [RPM] > max
KV
PowerGear Ratio change for
Train.Gearall gears
Box.iForwardGe
ars
Path to File
/Data/Vehicle/Examples_FS/
FS_RaceCar_TM
Table 6.8: Quantities to be evaluated in Top Speed Test
Validation Output
User Accessible Quantities
Vertical Loads on all 4 Wheels
Car.FzFL, Car.FzRL, Car.FzFR, Car.FzRR
Toe Angle
Car.ToeFL, Car.ToeRR
Camber Angle
Car.CamberFL, Car.CamberRR
Pitch Velocity
Car.PitchVel
Max Vehicle Speed
Car.v
Max Vehicle Acceleration
Car.ax
Max Engine RPM
PT.Engine.rotv
Max Engine Power
PT.Engine.PwrO
Pitch
Car.Pitch
Time
Time
Formula CarMaker Tutorial
Version 2.3
Simulation
123
TestManager
4. Braking_FS
Objective:- This TestRun aims to check the capability of brake system to lock all four (4)
wheels and stop the vehicle in a straight line. Vehicle accelerates from standstill to 50m followed by full braking. Good result for this test depends on appropriate brake pedal ratio,
CoG location, suspension and steering kinematics. For analyis students can opt for braking
distance, car velocity and Yaw angle of the car.
Table 6.9: Variable for Braking_FS Test
Type
Variable Name
Variable Description
Parameter Location
NV
CoG_x
X Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > x
NV
CoG_y
Y Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > y
NV
CoG_z
Z Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > z
KV
Pedal.ratio
Brake Pedal Ratio
Path to File
/Data/Misc/
HydESP_FS_RaceCar_4.0
Table 6.10: Quantities to be evaluated in Braking_FS Test
Validation Output
User Accessible Quantities
Vertical Loads on all 4 Wheels
Car.FzFL, Car.FzRL, Car.FzFR, Car.FzRR
Toe Angle
Car.ToeFL, Car.ToeRR
Camber Angle
Car.CamberFL, Car.CamberRR
Pitch Velocity
Car.PitchVel
Max Vehicle Deceleration
Car.ax
Pitch
Car.Pitch
Pedal force
Brake.Hyd.Sys.PedFrc
Pressure at master cylinder
Brake.Hyd.Sys.pMC
Pressure at each wheel
Brake.Hyd.Sys.pWB_FL,
Brake.Hyd.Sys.pWB_FR,
Brake.Hyd.Sys.pWB_RL,
Brake.Hyd.Sys.pWB_RR
Yaw Angle
Car.Yaw
Max Vehicle Speed
Car.v
Braking Distance
To be calculated using Real Time Expressions
Braking Time
To be calculated using Real Time Expressions
Formula CarMaker Tutorial
Version 2.3
Simulation
124
TestManager
5. Braking
Objective:- This TestRun aims to check the capability of brake system to lock all four (4)
wheels and stop the vehicle in a straight line. Vehicle accelerates from standstill to 100
Kmph followed by full braking. Good result for this test depends on appropriate brake pedal
ratio, CoG location, suspension and steering kinematics. For analyis students can opt for
braking distance, car velocity and Yaw angle of the car.
Table 6.11: Variables for Braking Test
Type
Variable Name
Variable Description
Parameter Location
NV
CoG_x
X Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > x
NV
CoG_y
Y Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > y
NV
CoG_z
Z Location of CoG
Parameters > Car > Vehicle Body >
Rigid Vehicle Body > Vehicle Body > z
NV
Brake
Brake Value (0-1)
Parameters > Maneuver > Maneuver
1 > Longitudinal Dynamics > Manual
(Pedals Gears) > Brake > Value
Table 6.12: Quantities to be evaluated in Braking Test
Validation Output
User Accessible Quantities
Vertical Loads on all 4 Wheels
Car.FzFL, Car.FzRL, Car.FzFR, Car.FzRR
Toe Angle
Car.ToeFL, Car.ToeRR
Camber Angle
Car.CamberFL, Car.CamberRR
Pitch Velocity
Car.PitchVel
Max Vehicle Deceleration
Car.ax
Pitch
Car.Pitch
Pedal force
Brake.Hyd.Sys.PedFrc
Pressure at master cylinder
Brake.Hyd.Sys.pMC
Pressure at all 4 wheels
Brake.Hyd.Sys.pWB_FL,
Brake.Hyd.Sys.pWB_FR,
Brake.Hyd.Sys.pWB_RL,
Brake.Hyd.Sys.pWB_RR
Yaw Angle
Car.Yaw
Max Vehicle Speed
Car.v
Braking Distance
To be calculated using Real Time Expressions
Braking Time
To be calculated using Real Time Expressions
Lateral Dynamics
1. Zigzag
Objective:- This TestRun aims to check Vehicle’s response to Steering input by following
continuous Left-Right turns which are spaced at a distance of 15 and 18m at varying
speeds. In order to increase the cornering efficiency students can alter suspension and
steering parameters so as to optimise body roll. For analyis students can opt for Body roll,
Lateral acceleration and steering wheel angle of the car.
Formula CarMaker Tutorial
Version 2.3
Simulation
125
TestManager
Table 6.13: Variables for ZigZag Test
Type
Variable Name
Variable Description
Parameter Location
NV
CSpeed
Cruising Speed
Parameters > Driver > User Parameterized Driver > Standard Parameters
> General > Cruising Speed
Table 6.14: Quantities to be evaluated in ZigZag Test
Validation Output
User Accessible Quantities
Lateral Acceleration
Car.ay
Max Roll angle
Car.Roll
Roll angle gradient
Car.RollAcc
Steering wheel angle
DM.Steer.Ang
Understeer gradient
To be calculated using Real Time Expressions
Slip Angle (all wheels)
Car.SlipAngleFL, Car.SlipAngleFR, Car.SlipAngleRL, Car.SlipAngleRR,
Steering Turning Torque
DM.Steer.Trq
Fz (Vertical forces on all tyres)
Car.FzFL, Car.FzRL, Car.FzFR, Car.FzRR
Yaw
Car.Yaw
Yaw rate
Car.YawRate
Time
Time
2. Steer Step
Objective:- This TestRun aims to check Vehicle’s response to sudden Steering input at varying speeds and steering angles. In order to increase the cornering efficiency students can
alter suspension and steering parameters so as to optimise body roll. For analyis students
can opt for Yaw rate, Lateral acceleration and steering wheel angle of the car.
Table 6.15: Variables for Steer Step Test
Type
Variable Name
Variable Description
Parameter Location
NV
SteerAng
IPG Driver Steer Step
Angle
Parameters > Maneuver > Maneuver
1,2 > Lateral Dynamics > Steer Step >
Amplitude
NV
SpeedCtrl
Control Speed Long.
Dynamics
Parameters > Maneuver > Maneuver
1 > Longitudinal Dynamics > Speed
Control > Speed
Table 6.16: Quantities to be evaluated in Steer Step Test
Validation Output
User Accessible Quantities
Lateral Acceleration
Car.ay
Max Roll angle
Car.Roll
Roll angle gradient
Car.RollAcc
Steering wheel angle
DM.Steer.Ang
Understeer gradient
To be calculated using Real Time Expressions
Formula CarMaker Tutorial
Version 2.3
Simulation
126
TestManager
Table 6.16: Quantities to be evaluated in Steer Step Test
Validation Output
User Accessible Quantities
Slip Angle (all wheels)
Car.SlipAngleFL, Car.SlipAngleFR, Car.SlipAngleRL, Car.SlipAngleRR,
Steering Turning Torque
DM.Steer.Trq
Fz (Vertical forces on all tyres)
Car.FzFL, Car.FzRL, Car.FzFR, Car.FzRR
Yaw
Car.Yaw
Yaw rate
Car.YawRate
Time
Time
3. Steady State Circle
Objective:- This TestRun aims to check limiting lateral stability of Vehicle by rotating in
steady-state circle of 42m radius at varying speeds and suspension parameters. In order to
increase the cornering efficiency students can alter suspension and steering parameters so
as to optimise body roll. For analyis students can opt for Lateral deviation, Lateral acceleration and steering wheel angle of the car.
Table 6.17: Variables for Steady State Circle Test
Type
Variable Name
Variable Description
Parameter Location
NV
CSpeed
Cruising Speed
Parameters > Driver > User Parameterized Driver > Standard Parameters
> General > Cruising Speed
NV
StabAmp
Stabilizer Stiffness
Amplification
Parameters > Car > Suspension >
Stabilizer > Front, Rear > Amplification
Table 6.18: Quantities to be evaluated in Steady State Circle Test
Validation Output
User Accessible Quantities
Lateral Acceleration
Car.ay
Max Roll angle
Car.Roll
Roll angle gradient
Car.RollAcc
Steering wheel angle
DM.Steer.Ang
Understeer gradient
To be calculated using Real Time Expressions
Slip Angle for all 4 wheels
Car.SlipAngleFL, Car.SlipAngleFR, Car.SlipAngleRL, Car.SlipAngleRR,
Steering Turning Torque
DM.Steer.Trq
Fz (Vertical forces on all tyres)
Car.FzFL, Car.FzRL, Car.FzFR, Car.FzRR
Yaw
Car.Yaw
Yaw rate
Car.YawRate
Lateral Deviation
Driver.Lat.dy
Time
Time
Formula CarMaker Tutorial
Version 2.3
Simulation
127
TestManager
For majority of the TestRuns respective acceptance criterias were defined and their meanings are expressed in the below Table.
Table 6.19: List of Criterias and Meanings
TestRun Name
Criteria
Description
Pull Test
G - [get LatShift] < abs(0.35) Lateral Deviation of Car on either
side from centre line is less than
0.35m
Y - [get LatShift] >=
Lateral Deviation of Car on either
abs(0.35) && [get LatShift] < side from centre line is between
abs(0.7)
0.35m and 0.7m
R - [get LatShift] >= abs(0.7) Lateral Deviation of Car on either
side from centre line is more than
0.7m
Acceleration
Top Speed
Top Speed
G - [get DM.ManTime] < 5
Acceleration Maneuver Time is
less than 5sec
Y - [get DM.ManTime] >= 5
&& [get DM.ManTime] <= 6
Acceleration Maneuver Time is in
between 5sec and 6 sec
R - [get DM.ManTime] > 6
Acceleration Maneuver Time is
more than 6sec
G - [get Time] < 16
Time to reach Top Speed is less
than 16sec
Y - [get Time] >= 16 && [get
Time] <= 20
Time to reach Top Speed is in
between 16sec and 20 sec
R - [get Time] > 20
Time to reach Top Speed is more
than 20sec
G - [get TopSpeed] > 44
Top Speed is more than 44m/s
Y - [get TopSpeed] >=41 && Top Speed is in between 41m/s
[get TopSpeed] <=44
and 44m/s
Braking_FS & Braking
R - [get TopSpeed] < 41
Top Speed is less than 41m/s
G - [get Car.Yaw] < 0.087 ||
[get Car.Yaw] > -0.087
Car Yaw angle is less than 0.087
rad (5 deg) in both the direction
Y - [get Car.Yaw] >= 0.087
Car Yaw angle is between 0.087
&& [get Car.Yaw] <= 0.174 || rad (5 deg) and 0.174 rad (10 deg)
[get Car.Yaw] <= -0.087 && in both the direction
[get Car.Yaw] >= -0.174
ZigZag
Formula CarMaker Tutorial
R - [get Car.Yaw] > 0.174 ||
[get Car.Yaw] < -0.174
Car Yaw angle is more than 0.174
rad (10 deg) in both the direction
G - [get Rollmax] < 0.0104
&& [get Rollmin] > -0.0104
Car Roll Angle is less than 0.0104
rad (0.6 deg) on either side
Y - [get Rollmax] >= 0.0104
&& [get Rollmax] <= 0.0122
|| [get Rollmin] <= -0.0122
&& [get Rollmin] >= -0.0104
Car Roll Angle is between 0.0104
rad (0.6 deg) and 0.0122 rad (0.7
deg) on either side
R - [get Rollmax] > 0.0122
&& [get Rollmin] < -0.0122
Car Roll Angle is more than 0.0122
rad (0.7 deg) on either side
Version 2.3
Simulation
128
TestManager
Table 6.19: List of Criterias and Meanings
TestRun Name
Criteria
Description
Steady State Circle
G - [get LatDyMax] <=0.35
&& [get LatDyMin] >=-0.35
Lateral Deviation of Car on either
side from centre line is less than
0.35m
Y - [get LatDyMax] >0.35 && Lateral Deviation of Car on either
[get LatDyMax] <=0.7 || [get side from centre line is between
LatDyMin] <-0.35 && [get
0.35m and 0.7m
LatDyMin] >=-0.7
R - [get LatDyMax] >0.7 ||
[get LatDyMin] <-0.7
Lateral Deviation of Car on either
side from centre line is more than
0.7m
Exercise
After running these TestRuns in the TestManager with the FS_RaceCar_TM, now you can
import your own car and perform these TestRuns.
Select Global settings in the TestManager and Add > Vehicle. After going to the Configuration tab, select your own car from your Project Folder. After importing, save the TestSeries
as "MyTestSeries".
Figure 6.11: Importing of Student Car Model
Formula CarMaker Tutorial
Version 2.3
Postprocessing
129
Compare results in IPGControl
Chapter 7
Postprocessing
Introduction
Postprocessing of simulation results can be used for different reasons. For example, you
may like to compare the results in a diagram, build simulation tables containing several
quantities or create illustrative material for presentations. CarMaker offers the possibility to
get close to all of these occasions.
Precondition for postprocessing is to dispose of simulation results. Therefore you have to
simulate TestRuns defined by the:
7.1
•
parameterization of a vehicle including the tires
•
definition of a virtual road
•
selection of a driver
•
declaration of maneuvers
Compare results in IPGControl
To compare simulation results you have to perform several TestRun simulations and save
the results of each TestRun in the "Storage of Results" box. Pay attention to the "OutputQuantities" configuration (Application > Edit ’OutputQuantities’), otherwise quantities
you like to be saved will be missing in the result file. You can find the simulation result files
of CarMaker in the following file structure of your project folder:
SimOutput > NameOfYourPC > Date > NameOfYourTestRun-Time.erg
With IPGControl you can compare the results using different diagram windows. You can
choose between two different possibilities:
•
compare the last simulated TestRun with a new one
•
compare the last simulated TestRun with a saved simulation results
Formula CarMaker Tutorial
Version 2.3
Postprocessing
130
Compare results in IPGControl
To compare several TestRuns without saving the performed simulation results follow the listed steps:
•
disconnect the last performed simulation in the main window of IPGControl
•
change the settings of your vehicle
•
reconnect the simulation by the use of "File > Connect to Application"
•
select your application which will be listed in the data set box
•
add a diagram to the data window "Display > Add Diagram"
•
choose the quantities to be displayed or load a defined group of quantities
•
start the simulation
Figure 7.1: Disconnect application
Figure 7.2: Reconnect application
Figure 7.3: Compare the results
Formula CarMaker Tutorial
Version 2.3
Postprocessing
131
Compare results in IPGControl
Using the second way to compare the simulation results you have to save the simulated
results first. After that keep the order of the listed steps below:
•
disconnect the last performed simulation
•
choose "File > Load File" and load all simulation results you like to compare. These
results will be listed in the data set box
•
select the simulation result you like to enter to the next diagram
•
switch to the data window and add a new diagram
•
select the quantities to be displayed or load a defined group of quantities
Figure 7.4: Load saved simulation results
Figure 7.5: Compare the results
Formula CarMaker Tutorial
Version 2.3
Postprocessing
132
Export simulation results
7.2
Export simulation results
CarMaker also offers different file formats to export the simulation results. Having finished
a simulation TestRun you need to do the following:
•
Right click anywhere in the data window and choose "Export to File".
•
In the popup window select a file format, choose a file path and enter a feasible file
name.
•
Confirm with "Save".
Figure 7.6: Export simulation results
7.3
Print diagrams
In IPGControl you can print plotted diagrams with the use of the right mouse click features.
In the popping up window you can enter a diagram title and confirm with "Print". IPGControl
creates a preview of the diagram which can be sent to a local printer by "File > Print".
Figure 7.7: Print diagrams
Formula CarMaker Tutorial
Version 2.3
Postprocessing
133
Postprocessing with Matlab
7.4
Postprocessing with Matlab
To work with simulation results of CarMaker in Matlab a command is given to convert the
data of the .erg files to vectors used in Matlab:
variabel1=cmread(’.../SimOutput/<NameOfYourPC>/<Date>/<NameOfYourTestRun-Time.erg’)
Instead of typing the path to your result file you can simply hit "Enter" after "cmread". With
this, an explorer pops up which lets you easily select the result file of interest.
The following script shows the procedure how to use the .erg files in Matlab which should
be opened in the "src_cm4sl" folder of your project folder:
variabel1=cmread(’...\SimOutput\<NameOfYourPC>\<Date>\<NameOfYourTestRun-Time.erg’)
% Plot
figure
% subplot (2,1,1)
hold on;grid;
plot(variable.Time.data, variable1.Car_v.data, ’b’);
legend(’Vehicle Speed’);
ylabel(’Time’);
title(’Speed vs. Time’)
Figure 7.8: Plotting in Matlab
If the command "cmread" will not be found by Matlab please make sure that the script
"cmenv.m" from the src_cm4sl folder of your CarMaker project directory was run successfully before. If not, you might have to adapt the path to your CarMaker installation folder in
the cmenv.m script (see page 90).
Formula CarMaker Tutorial
Version 2.3
Helpful suggestions
134
Chapter 8
Helpful suggestions
Recommended literature
If you are developing a Formula Student racing car for the first time, you might need some
more detailed background information. You can find below a list of recommended literature
which we think is very valuable to know.
•
Gillespie, Thomas:
Fundamentals of Vehicle Dynamics, SAE International, 1992
•
Heißing, Bernd; Ersoy, Metin:
Fahrwerkhandbuch, Vierweg-Verlag, 2007
•
Matschinsky, Wolfgang:
Die Radaufhängungen der Straßenfahrzeuge, Springer Verlag, 1998
•
Mitschke, Manfred:
Dynamik der Kraftfahrzeuge, Band A-C, Springer Verlag, 1982
•
Milliken, William F.:
Race Car Vehicle Dynamics, SAE International, 1995
•
Reimpell, Jörnsen; Betzler, Jürgen:
Fahrwerktechnik: Grundlagen, Vogel-Verlag, 2000
The company IPG Automotive GmbH observes with enthusiasm, how committed the members of each Formula Student team deal with such a huge project. From this enthusiasm
the idea to support these projects arose. This is done by the supply of software licenses as
well as technical support. Every team can contribute to achieve a high efficiency in this. In
the following paragraph a few incitements to it are given.
Formula CarMaker Tutorial
Version 2.3
Helpful suggestions
135
Email contact
The email support is available for every team at no charge. Please address every question
to [email protected] Behind this email contact lies a contributor which forwards
the incoming mails to every member of the Formula CarMaker Support Team immediately.
In this way all mails are sent to the person in charge in each case. Moreover, in special cases such as an employee being on holiday or out of town all questions can be handled nonetheless.
Meanwhile the IPG Automotive GmbH supports over 100 teams worldwide. This means at
two registered members per team a total of over 200 students to service. A mental association with every 200 persons is impossible. Accordingly, this must be done with the help of
your email address. Many Formula Student teams do not dispose of an own email address
and all that’s left from your mail is your text with signature. Thus, the Formula CarMaker
Support Team is very grateful for every inquiry that includes the name of your team and university.
In addition to the email contact the Formula CarMaker support features various tutorials and
handbooks. It is recommendable to browse through these documents as they provide many
answers of fequently asked questions. Furthermore they are available round the clock and
might solve your problem earlier than a contact via email can do.
Further development of the programs
To enhance the development of CarMaker, IPGKinematics and other IPG products, the IPG
Automotive GmbH is looking forward to any information about errors and potential improvements. The Formula CarMaker Support Team truly appreciates any kind of suggestion and
incitement!
Remark to the used versions and datasets
This document refers to the following programs and versions: CarMaker 5.1.2, IPGKinematics 3.6.4 and Matlab R2011a. All used datasets such as the TestRun "FS_Competition_
SkidPad" ran without problems in these versions and can be downloaded from the member
area (FS_Generic_2017) on the IPG website.
Formula CarMaker Tutorial
Version 2.3
Bibliography
136
Appendix A
Bibliography
Literature
[CMR07]
IPG Automotive GmbH: CarMaker Reference Manual. IPG Automotive
GmbH, 2014
[CMU07]
IPG Automotive GmbH: CarMaker User’s Guide. IPG Automotive
GmbH, 2014
[HE07]
Heißing, E.; Estoy, M.: Fahrwerkhandbuch. Wiesbaden: Vierweg-Verlag, 2007
[KIN07]
IPG Automotive GmbH: IPGKinematics Handbuch. IPG Automotive
GmbH, 2014
[RB00]
Reimpell, J.; Betzler, J..: Fahrwerktechnik: Grundlagen. Würzburg:
Vogel-Verlag, 2000
[Rei82]
Reimpell, J.: Fahrwerktechnik 1. Würzburg: Vogel-Verlag, 1982
[Rei84]
Reimpell, J.: Fahrwerktechnik: Lenkung. Würzburg: Vogel-Verlag, 1984
[RH84]
Rompe, K.; Heißing, B.: Objektive Testfahrten für die Fahreigenschaften
von Kraftfahrzeugen. Köln: Verlag TÜV Rheinland GmbH, 1984
[SAE07]
Society of Automotive Engineers: Formula SAE Rules. Society of Automotive Engineers, 2007
[TIR07]
IPG Automotive GmbH: IPGTire Tutorial. IPG Automotive GmbH, 2007
Websites
[1]
Formula CarMaker Tutorial
http://www.formulastudent.de
Version 2.3
Data files
137
Appendix B
Data files
B.1 Example of a TYDEX code
!# $Id: TUTO_TYDEX_TEST.tdx,v 1.2 2005/06/30 14:02:50 cr Exp $
**HEADER
!---------!-----------------------------!---------!---------!
! Key ! Comment ! Unit ! value !
!---------!-----------------------------!---------!---------!
RELEASE Release of TYDEX-Format 1.3
SUPPLIER Data supplier DEMO
DATE Date 07/98
CLCKTIME Clocktime 12:05
**COMMENTS
! Demo with TIME measurement procedure
! New tyre used
**CONSTANTS
!---------!-----------------------------!---------!---------!
! Key ! Comment ! Unit ! value !
!---------!-----------------------------!---------!---------!
TESTRIG Test rig DEMO
LOCATION Location DEMO
MANUFACT Manufacturer of the tyre DEMO
IDENTITY Identity of the tyre DEMO
Formula CarMaker Tutorial
Version 2.3
Data files
138
NOMWIDTH Nominal section width of tyre mm 195
ASPRATIO Nominal aspect ratio % 65
RIMDIAME Nominal rim diameter inch 15
RIMWIDTH Rim width inch 6.5
RIMPROF Rim profile J
REFSIDEW Reference sidewall DOT
TYWHASSB Tyre-wheel assembly REFSWLEFT
TRDDEPB tread depth before mm 8
TRDDEPA tread depth after mm 5.4
TRCKSURF Surface of track SAFETYWALK
AMBITEMP Ambient temperature deg C 25
PATHRADC Path radius m INFINITY
INFLPRES Inflation pressure bar 2.5
TRCKCOND Track condition DRY
OVALLDIA Overall diameter mm 580
KROLRAD kinematic roll radius mm 280
**MODELPARAMETERS
!---------!-----------------------------!---------!---------!----!
! Key ! Comment ! Unit ! value !factor!
!---------!-----------------------------!---------!---------!----!
ITVS Vertikale Reifenfeder 350000.
ITVD Vertikaler Reifendaempfer 1000.
ITRLLO Relaxationslaenge laengs 0.05
ITRLLA Relaxationsl. quer 0.1
ITSSCLO StillStandskoeffizient long 0.01
ITSSCLA StillStandskoeffizient quer 0.01
ITRORETL roll resistance Trq/Load 0.01
**MEASURCHANNELS
!---------!-------------------------!---------!--------!-------!-! Key ! Comment ! Unit ! factor ! offset!offset
!---------!-------------------------!---------!--------!-------!-!
!physical value [Unit]= factor*(measured value + offset1) + offset2!
FZH Vertical force N 1 0 0
SLIPANGL Slip angle deg 1 0 0
INCLANGL Inclination angle deg 1 0 0
FYH Lateral force N 1 0 0
Formula CarMaker Tutorial
Version 2.3
Data files
139
MZH Aligning moment Nm 1 0 0
**MEASURDATA
1211.00 -0.50 0.00 211.21 -2.27
3021.70 -0.50 0.00 460.01 -8.08
4828.00 -0.50 0.00 641.08 -15.50
6635.91 -0.50 0.00 748.59 -23.11
8444.54 -0.50 0.00 782.56 -29.70
8451.64 -1.00 0.00 1650.01 -74.74
6640.98 -1.00 0.00 1549.56 -55.52
4835.30 -1.00 0.00 1296.28 -34.95
3023.70 -1.00 0.00 883.88 -16.36
1217.11 -1.00 0.00 359.97 -3.51
1210.54 0.01 0.00 15.75 0.29
3022.89 0.00 0.00 -31.05 2.83
4828.88 0.00 0.00 -80.67 7.00
6641.35 0.00 0.00 -106.23 11.94
8447.86 0.01 0.00 -130.66 18.29
8447.03 0.51 0.00 -1014.16 64.33
6643.04 0.50 0.00 -927.98 46.09
4837.24 0.50 0.00 -763.21 28.49
3021.81 0.50 0.00 -478.76 13.10
1211.60 0.50 0.00 -143.84 2.69
1213.37 1.00 0.00 -305.18 4.09
3024.83 1.00 0.00 -890.32 20.23
4830.25 1.00 0.00 -1383.04 45.36
6639.96 1.00 0.00 -1677.46 75.28
8446.77 1.00 -0.01 -1816.43 105.83
8439.81 0.00 -3.04 323.53 28.80
4827.96 0.00 -3.03 216.27 17.45
1209.10 0.00 -3.02 99.88 6.40
1213.58 0.00 -1.00 72.70 2.71
4829.41 0.00 -1.00 45.71 10.10
8438.02 0.01 -1.00 39.30 21.39
8454.52 0.00 1.01 -213.57 13.88
4838.03 0.00 1.01 -108.97 3.08
1213.67 0.00 1.01 32.59 -2.27
1216.10 0.00 3.03 -7.26 -5.38
Formula CarMaker Tutorial
Version 2.3
Data files
140
4843.10 0.00 3.02 -259.95 -4.09
8447.27 0.01 3.02 -467.54 6.22
6650.47 0.00 5.03 -561.46 -6.26
4839.59 -0.50 3.00 470.52 -28.39
3027.08 -0.50 3.00 355.43 -18.89
1210.09 -1.00 0.98 377.33 -6.01
1211.40 1.01 -1.04 -294.24 6.04
3013.27 0.51 -3.05 -314.68 23.15
4821.91 0.50 -3.04 -496.45 40.38
6632.49 0.00 -5.05 466.31 30.36
6204.67 -1.11 1.42 1596.27 -65.11
4671.47 1.11 -1.42 -1385.77 52.51
4676.80 -1.11 1.42 1345.09 -44.21
6192.29 1.11 -1.43 -1665.13 79.80
8480.00 -9.68 5.56 6653.04 -70.43
2398.14 9.69 -5.58 -2400.98 0.98
2387.44 -9.69 5.57 2326.81 -5.20
8475.57 9.70 -5.57 -6594.03 67.88
6950.80 -2.12 2.82 2646.00 -128.43
3882.44 2.12 -2.83 -1856.83 57.17
3895.17 -2.12 2.82 1863.24 -56.02
6938.60 2.12 -2.83 -2774.20 140.19
9285.47 -12.11 5.91 7232.49 -48.49
1640.53 12.12 -5.93 -1672.14 -0.80
1638.45 -12.12 5.92 1657.14 -0.70
9281.01 12.13 -5.92 -7192.70 49.90
7713.80 -5.05 4.22 5267.92 -193.88
3121.37 5.04 -4.23 -2620.77 38.67
3122.04 -5.04 4.22 2648.05 -41.97
7693.48 5.05 -4.23 -5236.87 186.65
4367.24 -2.32 0.61 2292.76 -57.70
1663.58 2.32 -0.62 -834.64 11.48
1662.51 -2.32 0.61 904.85 -11.56
4362.46 2.32 -0.62 -2380.05 61.50
6174.07 -9.34 1.39 5559.15 -26.00
773.02 9.35 -1.41 -915.13 0.99
798.32 -9.34 1.40 926.42 -2.22
Formula CarMaker Tutorial
Version 2.3
Data files
141
6179.77 9.35 -1.40 -5566.71 16.28
4819.49 -4.12 0.81 3842.98 -81.60
1213.00 4.12 -0.82 -1007.44 7.96
1212.24 -4.12 0.81 1009.89 -7.99
4821.89 4.13 -0.82 -3861.91 74.69
5271.42 -5.83 1.00 4830.02 -72.66
770.04 5.83 -1.01 -804.12 4.11
763.44 -5.83 1.00 767.93 -3.31
5278.38 5.84 -1.01 -4780.28 58.53
8458.68 -12.04 -0.01 6912.70 -18.90
1199.51 12.05 0.00 -1330.46 -1.45
1198.00 -12.05 0.00 1343.88 1.13
8459.97 12.06 0.00 -6950.92 10.93
6649.84 -5.83 -0.01 5764.30 -102.48
1808.09 5.83 0.00 -1829.74 8.55
1806.19 -5.83 0.00 1823.33 -9.80
6649.88 5.84 0.01 -5683.13 86.77
7257.76 -8.34 -0.01 6394.02 -51.62
1198.32 8.34 0.00 -1353.07 1.28
1198.65 -8.34 0.00 1366.09 -1.91
7259.76 8.35 0.01 -6374.97 42.24
1207.40 -12.06 -1.98 1370.53 3.10
7237.09 12.06 1.98 -6209.88 -1.17
5444.26 -1.71 1.61 2181.08 -78.76
3012.59 1.72 -1.63 -1390.39 34.41
3011.54 -1.71 1.61 1422.13 -33.04
5438.58 1.72 -1.63 -2243.23 85.30
7262.97 -9.76 3.97 6109.24 -40.52
1209.37 9.78 -3.99 -1327.95 2.74
1198.86 -9.77 3.98 1268.81 -1.82
7269.73 9.77 -3.98 -6200.20 42.36
6035.69 -3.62 2.41 4085.05 -136.36
2396.46 3.63 -2.43 -1914.02 29.52
2396.28 -3.62 2.42 1937.77 -29.37
6025.61 3.63 -2.43 -4096.58 130.20
6655.31 -6.74 3.20 5750.83 -91.56
1809.13 6.75 -3.22 -1887.68 10.09
Formula CarMaker Tutorial
Version 2.3
Data files
142
1801.47 -6.74 3.21 1851.49 -9.41
6646.61 6.75 -3.21 -5712.57 87.20
**END
Formula CarMaker Tutorial
Version 2.3
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement