YASKAWA MP2000 Series Technical Note

TECHNICAL NOTE
MOTION APPLICATION ENGINEERING GROUP
Subject: MP2000 Best Practices Guideline
Product: MP2000 Controllers
Status:
Rev 1.1
Summary: This document is a guide for use to implement Best Practices for programming design
and architecture for an MP2000 controller system. The main topics discussed in this document are
an overview of the design process, followed by three detailed topics of memory allocation, drawing
use, and developing code for motion control.
Format of Information:
The information provided in the topics discussed here are intentionally concise. The appendixes
for the related topics provide information and examples for the user to reference if more detail is
preferred. This document discusses the MP2000 Best Practices in the sequence of normal
application development. The main sections are:
Machine Information Gathering
Selecting a Programming Method
Program Architecture
Memory Allocation
Symbol and Commenting Naming Conventions
Code Development
While it is possible to control up to 256 axes, this document is based on
up to 64 axes being utilized. For applications using more than 64 axes
contact Yaskawa for technical support.
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DOCUMENT REFERENCES: ........................................................................................................3
MP MACHINE CONTROLLER PROGRAMMING BEST PRACTICES OVERVIEW....................4
WHY USE A YASKAWA MACHINE CONTROLLER? ..................................................................................... 4
WHAT’S IN MP PROGRAMMING BEST PRACTICES GUIDELINE?................................................................. 4
BENEFITS OF USING MP BEST PRACTICES: ............................................................................................... 5
GETTING STARTED – USING THE MP BEST PRACTICES GUIDELINE ..................................7
MACHINE INFORMATION GATHERING......................................................................................8
SELECTING PROGRAMMING METHOD .....................................................................................9
OVERVIEW OF MOTION FROM MP CONTROLLER CODE TO AMPLIFIER .................................................... 12
REGISTER INTERFACE .............................................................................................................................. 14
PROGRAM ARCHITECTURE .....................................................................................................15
DRAWINGS DEFINITION ........................................................................................................................... 15
DRAWING FAMILY EXECUTION ............................................................................................................... 15
DRAWING FAMILY HIERARCHY AND PROGRAM FLOW .............................................................................. 17
BEST PRACTICE DRAWING USAGE............................................................................................................ 18
MP2000 BEST PRACTICE DRAWING ARCHITECTURE .............................................................................. 19
Drawing Architecture for A, H, and L................................................................................................ 20
MEMORY ALLOCATION.............................................................................................................22
WHAT IS MEMORY MAPPING?................................................................................................................. 22
WHY IS IT IMPORTANT? ........................................................................................................................... 22
MEMORY MAPPING WITH FUNCTION BLOCKS ........................................................................................... 22
D REGISTERS FOR WORKING MEMORY ..................................................................................................... 23
AUTOMATIC ADDRESS ALLOCATION ....................................................................................................... 24
Advantages......................................................................................................................................... 24
Disadvantages .................................................................................................................................... 25
SYMBOL NAMING & COMMENTING CONVENTIONS .................................................................................. 26
Purpose of naming convention ........................................................................................................... 26
Recommendations............................................................................................................................... 26
DEVELOPING CODE...................................................................................................................27
LADDER TECHNIQUES ............................................................................................................................. 27
Low Scan Interlocks ........................................................................................................................... 27
Purpose of Interlocking HMI.............................................................................................................. 33
Machine Interlocks ............................................................................................................................. 34
Gearing............................................................................................................................................... 37
Waterfall Technique ........................................................................................................................... 40
Modulus Technique ............................................................................................................................ 42
Delta Scan .......................................................................................................................................... 44
Handling Rollover .............................................................................................................................. 45
Sequencing Techniques ...................................................................................................................... 46
RULES FOR MOTION PROGRAMMING ...................................................................................................... 48
Initiating Motion Program ................................................................................................................. 49
Interlocking During Execution ........................................................................................................... 51
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DOCUMENT REFERENCES:
Following is a list of documents used or referenced to in MP Best Practices
eng.MCD.05.055
MP2000 Best Practices Guideline (.pdf)
eng.MCD.05.096
MP2000 Best Practices Information Gathering (.pdf)
eng.MCD.05.097
MP2000 Best Practices Global Memory Registration Map (.xls)
eng.MCD.05.098 MP2000 Best Practices Motion Language Sample Code (.mal)
eng.MCD.05.099 MP2000 Best Practices SVB Ladder Template Code (.mal) (in development)
eng.MCD.05.031 Basic Design (.ppt)
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MP MACHINE CONTROLLER PROGRAMMING BEST PRACTICES
OVERVIEW
Why Use a Yaskawa Machine Controller?
General automation machine controllers are beneficial in that they offer a unique flexibility for
programming the operation of functions and sequences within a machine. Whether the
application warrants high performance point-to-point indexing, discrete motion operations,
continuous motion operations, or complex scan based motion profiling with on-the-fly phase
shifting – all benefit from tightly coupled motion and machine sequence logic control. As factory
floor production requirements increase, machine cells must also increase their own production
capability, and precise control of complex motion becomes vitally important to insure production
rates are met and continue high quality product yield.
Many independent PLCs and Motion Controllers reach a limitation when programmers strive to
achieve these new and improved line production performance benchmarks, and unfortunately
result in a bottleneck when trying to increase the performance of a system. This bottleneck can
often be caused by control systems latencies in data handshaking or lack of synchronization, not
only from cell controller to cell controller, but also within a single controllers functional module
interfacing. A good machine control platform tightly couples high performance motion control
capabilities with machine sequence logic, and provides the foundation and scalability necessary
to achieve performance in a changing environment.
True machine control tightly integrates the following: high and low performance features, priority
setting and adjustment, determinism and predictability, synchronization of tasks / processors /
networks, high execution rates, scalability without sacrificing performance, integration of
peripheral components, and a focus on precise motion control. The result is smooth motion, less
machine jerk, less mechanical vibration, less heating, smaller and more efficient motor sizes,
higher machine reliability and longer life cycles – all with the advantage of built in future
expansion.
To take advantage of the power of total machine synchronization and extend this capability
across a wide range of performance requirements - from low performance, low cost machines to
high performance, higher priced machines, a scalable machine control platform is offered by
Yaskawa: the MP Series Machine Controller. To harness the power of flexibility and performance
while maintaining an overall ease of use, Yaskawa also introduces the MP Machine Controller
MP Programming Best Practices Guideline.
What’s in MP Programming Best Practices Guideline?
This document is a guideline to lead the controls engineer down a successful path that will not
only increase programming productivity for any given machine, but also an entire line of
complementary machines which can be offered for different user requirements. It outlines and
encourages the use of best practices by some of the top motion and machine control engineers
of the MP product line, including its predecessors. This document helps the programmer to
realize the benefits of following best practices:
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Benefits of Using MP Best Practices:
Benefits can be realized at all levels of machine development from design to
implementation to field support. In summary, all benefits work towards lowering the total
cost of ownership in the machine’s product lifecycle.
- Design Level Benefits
o
Programming Method Selection: A flexible machine control allows several ways
to program motion control. This guideline helps the programmer select the best
programming method for a given application type.
o
Standardized Model: This guideline helps the programmer develop a robust
framework and controls architecture, and secures a solid platform for code
development. In addition, within the guideline are several examples of
standardized programming methodologies that leverage template examples.
o
Step-By-Step Basic Design: There’s a higher probability of getting it right the first
time if a step-by-step approach is followed, reducing the possibility of missing
important steps along the way. This guideline provides a step-by-step flowchart
of machine development features.
o
Risk Reduction: A higher percentage of completing development projects on
time, and on budget will result through the use of MP Programming Best
Practices.
- Implementation Level
o
Pre-Defined Code & Scalability: This guideline provides pre-defined code and
canned functionality recommendations, which in turn reduce development and
debugging time. More efficient code development can be realized, which affords
more time to be spent on process related issues.
o
Optimized Performance & Robustness: Code efficiency is dependant upon good
implementation of well thought out architecture. If the code is written right,
performance of the control system can be optimized resulting in lower scan
times, increased motion performance, and increased performance of device
interfacing. This guideline encourages optimized performance in implementation
resulting in robust code that works.
o
Organization: This guideline makes programming easier because features are
compartmentalized for streamlined implementation. An organization layout is
provided for memory mapping, variable/tag usage, alarm interlocking, program
flow, axis control management, I/O usage, etc.
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- Support Level
o
Comprehensive Training: Using Best Practices supplements Yaskawa’s product
training, allowing the skills learned to become better utilized.
o
Transferable Skills: Using best practices across multiple machine designs,
reduces risk by taking advantage of architecture knowledge acquired on previous
designs.
o
Common Look and Feel: Using commonly defined, standardized methods will
make the system easier to support when the machine is in production. Tech
support engineers can leverage the same best practices. Maintenance and
troubleshooting become easier on a global basis. MP Best Practices is not
meant to replace open standards, but rather to compliment standards such as
OMAC PLC OPEN “function blocks for motion control”.
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GETTING STARTED – USING THE MP BEST PRACTICES GUIDELINE
This Best Practices Guideline is designed to help the controls engineer better utilize the strengths
of Yaskawa technology, allowing them to leverage the unique flexibility of functionality that the
MP2000 platform offers, and best align the implementation with the specifics of the application
requirements. Understanding the control systems benefits and constraints early in the design
process results in a higher probability of successful machine design when merging the controls
programming with the application process, lowering risk and overall rework.
This guideline will serve as a machine controller design and development methodology,
presenting program architecture and memory mapping recommendations, programming
recommendations, as well as actual code examples and pre-defined templates to get jump
started. It also provides experienced controls engineers with a benchmark to compare against,
allowing them to make more informed decisions between known practical solutions, and new,
unique ideas of a better method.
First time users will find this MP Best Practices guideline as a useful tool and guide them through
a recommended step-by-step procedure for controls development on for an automated machine
with tightly integrated motion control. More experienced users will find this MP Best Practices
guideline as a useful reference tool for specific techniques and code modules that can be readily
used. This guideline is formatted to provide the specific techniques, with a Step-by-Step
framework.
The following diagram illustrates the recommended step-by-step procedure when developing a
performance machine control system.
Step 1:
Machine
Information
Gathering
Step 2:
Programming
Style
Selection
Step 3:
Control
System
Performance
Review
Step 5:
Memory
Allocation
Step 6:
Symbol and
Commenting
Standardizing
Step 7:
Code
Development
Step 4:
Program
Architecture
Design
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MACHINE INFORMATION GATHERING
In order to implement a structured, reliable and efficient machine control system, requirements of
the machine should be gathered thoroughly in a formal manner to insure details of the system
design or functionality are not overlooked. The sequences of steps for machine information
gathering are shown in the diagram below. Note the sequence of the diagram is in logical
development of the application. Brief descriptions of the information gathering steps and
references to examples of the steps are located in eng.MCD.05.096, MP2000 Best Practices
Information Gathering. Basic Design template example is also referenced in eng.MCD.05.031
Basic Design Template.
Basic Design Steps
START
Machine Block
Diagram
Product Data
1. Max/Min machine speed
2. product sizes
3. product attributes
4. machine speed vs. product size
Machine Timing Diagram
Motion Kernel control block diagram
I/O List
Each Pt. Description/Function/
Dependancies
User Interface
Data setting/selection/input
security levels
Axis List
prod. oper. control mode
Fault Diagnostics & Recovery
1. Warning indication
2. Fault indication
Network Interfacing specifications
1. Physical Layers
2. Protocol Layers
Data Storage & Data reporting
requirements
Machine State Diagram
Variable/Tag/Symbol/Constant
requirements
Identify MachineSequences
Flowchart sequences of Homing,
Production, Fault Recovery, etc.
Create Basic Design Document
END
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After the requirements and functionality of the machine are documented, the controls
programmer is then able to evaluate the optimum methods of implementing machine and motion
control. The machine block diagram, sequences, timing diagram, and motion kernel control block
diagram will be key in evaluating the programming method to use in the application.
SELECTING PROGRAMMING METHOD
Use the table below to assist in deciding the proper motion control programming implementation
based on the type of machine being controlled and the motion required.
Machine Complexities versus Programming Methods
MACHINE COMPLEXITIES
Motion
P
r
o
g
r
a
m
M Function
Blocks
e
t
Motion
h
Programs
o
d
Ladder
All co-ordinated
scan based profile
generation
Interpolation
O
O ##
X
X
O
O
**
O
O
O
O
Point to Point
O
*
KEY
O
Applicable Method
X
Not Viable
It is possible to mix motion programming methods in a controller, but it is recommended
to run a axis by only one method.
## Axis count dependent
* Consider method with caution
** Any interpolation instructions generates scan based profile
After evaluating programming methods in relation to machine complexity, the user should
evaluate the individual programming methods based on overall system constraints such as
quantity of axes, programmer expertise, and overall system performance criteria. These
parameters are summarized in the table, Programming Language Grid For High Level Topics on
the following page.
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Programming Language Grid For High Level Topics
Ladder Based Motion
Text Based Motion
Programs
Function Block
Motion
High Level Topics
Required Programmer
Expertise Level
most flexible
easy
easy
Performance
highest
medium
high
Maximum axes
Only Limited by Hardware
(16 / group)
16
Scan time
most efficient
Motion programs
synchronize with H
Ladder
Troubleshooting
Register based
Register based
A function block
handles this
Memory allocation
Register based
Register based
reserved data area
required
additional scan time
over head
Note: This table is a broad overview perspective.
Finally, consider the specific motion control functionality required. Individual, built in function
detail is evaluated for the three programming methods listed in the table, “Programming
Language Grid For Built In Functions” on the following page.
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Programming Language Grid For Built In Functions
Ladder Based Motion
Text Based Motion
Programs
Function Block
Motion
Built in Function
Detail
Jogging
possible
possible*
possible
Absolute or Relative
Indexing
possible
possible
possible
Change final position
on the fly
possible
not possible
possible
Linear interpolation
not possible
possible
possible
Circular/Helical
interpolation
possible
possible
not possible
Homing
possible
possible
possible
Basic Camming
possible
not possible
possible
Advanced Camming
(including
master/slave shift or
offset on the fly)
possible
not possible
possible
Basic Gearing
possible
not possible
possible
Advanced Gearing
with slave shift
possible
not possible
possible
Customized scanbased profiling
possible
not possible
possible
Change Acc/Dec on
the fly
possible
not possible
possible
Change Velocity on
the fly
possible
possible**
possible
Position Latching
possible
not possible
possible
Latch Target
possible
possible
possible
Hold/Resume Motion possible
possible*
possible
Servo Enable
possible
possible*
possible
Fault recovery
possible
not possible
possible
E-Stop Recovery
possible
possible*
* ladder coding req.
** with ladder code
possible
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To further understand and evaluate motion programming methods, consider the table below.
This diagram illustrates how logic in the controller is translated to motion via the SVB
components of a MP Controller system.
Overview of Motion from MP Controller Code to Amplifier
-The Program Layer can be broken down into High and Low scan priorities. Code efficiency
determines the ultimate scan rate. The interface between the Program Layer and Network Layer
is the SVB IF module. As the application program grows, performance of the segregated network
layer module is not affected. This is a key point for performance!
-The Network Layer can be broken down into scalable scan rates and scalable data packet size.
Scan rates are determined by the quantity of axes and quantity of network interface cards.
Above eight axes, the system operates at a 2msec update rate, even for hundreds of axes. Data
sent down to the network card is further interpolated at the servo update rate. The interface
between Network Layer and Node layer is MechatrolinkII IF.
-The Node Layer can be broken down into Servopack, I/O, and Inverter/ VFD nodes. For servo
motion control, the speed of the position loop update and local interpolation between commands
promote high performance, and ability to control any of the following: Rotary, Direct Drive, and
Linear Motors. The load, coupling, and transmission mechanics further determine overall
performance.
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All Layers in a System
Example:
CPU X Scan
= 4 msec (MP2300)
Network Y Scan = 1 msec (8 axes of servo)
Final performance note for all layers in a system:
The data being transferred to the network devices is based on the ‘motion and I/O registers.” All
registers are updated at the end of the Program Layer scan at the same time, and the interface
between each layer synchronizes to bring about system determinism. Hence, the performance is
predictable. Network delay can be fed forward at a certain resolution to reduce steady state error
of high-speed applications. This is key point for maximum performance!
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At the programming level, the user interfaces to the motion system via Monitoring Parameters for
feedback and Setup Parameters for commanding motion. Each axis has registers associated
with it. The user application manipulates these registers either directly in Ladder Based Motion
or indirectly using Motion Programming or Function Blocks.
Register Interface
The application program interfaces to the motion network via register interface. These registers
are updated each high scan of the processor.
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PROGRAM ARCHITECTURE
After evaluating programming methods based on the system requirements, the user is ready to
design the program architecture. The program architecture is designed by locating logic in the
most appropriate drawings in either the high or low scan, based on the application requirements.
Before specifying specific drawings based on function, it is key to understand drawings, their
execution, and hierarchy in the MP Controller.
Drawings Definition
Application programs for MP2000 controllers are created using modular sections of
ladder logic code called “drawings.” There are four families of drawings: A, I, H and L,
organized in a generational hierarchy and denoted in the following chart.
Parent
Child
Grand
child
Family A
A
Axx
Axx.xx
Family I
I
Ixx
Ixx.xx
Family H
H
Hxx
Hxx.xx
Family L
L
Lxx
Lxx.xx
Valid drawing names must adhere to the above format with xx = 01-99. The maximum
combined number of Child/Grandchild drawings differs for each ladder family as follows:
A = 62
I = 62
H = 198
L = 498
Drawing Family Execution
Each drawing family executes at a unique point in the overall program scan, offering the user the
opportunity to optimize system performance. The following charts demonstrate the priority given
to each drawing type and also show an example of actual program execution. The MP controllers
allow the user to set the High and Low Speed Scan intervals.
Drawing
Family
A (Power-up)
I (Priority 1)
H (Priority 2)
L (Priority 3)
Function
Executed only once upon power up.
Executed once at the rising edge of an interrupt input
signal, 1st input on a bank of LIO or CPU I/O input 1
Executed once every High speed scan interval
Executed once every Low speed scan interval.
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Drawing Execution Chart
The above drawing execution chart graphically illustrates the Drawing Family and Function table
from the previous page.
•
At power up, the A drawing executes AND completes before other drawings execute.
The A drawings execute once only at power up.
•
The high scan drawings always complete within the high speed scan set time as
illustrated above.
•
In the remaining time of the high speed scan, the low scan drawings execute in time
slices until they complete execution within the low speed scan set time.
•
At the completion of the low scan drawings, background system tasks are executed.
•
If an interrupt condition occurs, the I drawing executes immediately, then normal
scanning resumes.
•
Setting Parameters and Monitor Parameters are updated each high speed scan while
low scan I/O updates occur every low speed scan set time.
The update of I/O and parameters as well as understanding drawing execution is critical to
code development so that the proper interlocks exist to obtain expected logical results.
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Drawing family hierarchy and program flow
The parent drawings begin execution automatically upon their appropriate internally
generated timing signal. Child and Grandchild drawings are programmatically called
using the SEE instruction. Calls to a descendent drawing must be contained with the
generational hierarchy, so only a linear descendent can be called. The figure below
shows the execution flow of a drawing family. “X” represents a drawing family, which can
be replaced with A, I, H or L.
Using a conditional “SEE” instruction is not recommended. This could result in problems such as
leaving an output in an undesirable state or interfere with one-shot actions.
After reviewing the drawing types, execution and hierarchy, the user is now ready to examine the
use of drawings for the machine control application.
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Best Practice drawing usage
A-Drawings
This drawing family is best used for initial system setup since it is executed only
once upon power up. WARNING: A-Drawings do not re-run after a CPU
RUN/START from a CPU stop state.
Clear Memory Registers
MP controllers retain the state of M registers with a battery. All memory
register states are retained through power loss. Safety reasons dictate
that machine states such as Auto/Manual and Run/Stop should be
initialized to a desired value to avoid dangerous situations should a
power outage occur.
Initialization Function Blocks
RDAINIT1 and RDAINIT2 functions blocks are placed in this drawing
family to setup Function Block programming environment.
It is recommended to set the registers to zero in the H-drawing using s system bit
that comes on only for the first scan. Best practice is to set constant values into
registers using a Low Speed L drawing (L40 in particular).
I-Drawings
This drawing family is only used for time critical operations. Thanks to recent
improvements in CPU processing speed, the High Speed Scan Interval is usually
fast enough to handle most applications. You can generally avoid using this
family.
H-Drawings
The recommended main drawings are:
- H10: Common machine high-speed processes.
- H20: Machine axes control.
- H30: Machine high-speed auxiliary devices.
Additional drawings:
- H15: Axes trajectory calculation for master-slave processes.
- H25: Motion programs control.
This drawing family is best used for the time critical processing of the application.
All code directly pertaining to motion control should be placed here.
Examples include:
Direct motion register control
Motion critical Function Blocks
Text-based Motion Programs calls.
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Master encoder position handling for GEAR and CAM Interpolated
motion scan-based trajectory calculation
High speed I/O processing (example: PLS)
L-drawings
The recommended main drawings are:
- L10: Common machine low speed processes.
- L20: Machine axes sequencing and interlocks.
- L30: Machine low speed auxiliary devices.
- L40: Machine constants setting.
Additional drawings:
- L01: HMI communication.
- L25: Motion programs control.
This drawing family is used for Non-time critical processing of the application.
Most general machine control and logic sequencing should be placed here.
Examples include:
HMI data handling
Machine operation mode (Auto/Manual)
Axis operation sequencing (Cycle 1 / Cycle 2)
Pneumatic valve operation
Conveyor operation (relatively constant speed)
Constant value setting
Auxiliary equipment control
Low speed I/O processing
MP2000 Best Practice Drawing Architecture
A key advantage of Best Practices drawing architecture is organization. Programming and debug
is simplified by compartmentalizing functionality. Code efficiency is improved by well-designed
architecture allowing for lower scan times and increased performance. Modularized code
enables scalability and re-use of code segments. Most of the code is contained in the grandchild
drawings.
General Architecture Outline
•
•
•
•
•
•
Servo axis high scan drawing executes only the motion code, equivalent low scan axis
drawing specifies mode.
H11-H19 can be used for high speed functions or calculations with H15 normally being
reserved for trajectory calculations.
Make an “Always Off” bit in the first rung of the A, H and L parent drawings. This is
useful if an “Always Off” parameter input to a function is required
Pushbutton and HMI logic sequencing should be in low scan.
H25 can optionally be organized by Motion Program number as opposed to Group
number.
The maximum number of axes to follow the suggested architecture layout is 64.
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Drawing Architecture for A, H, and L
Initialization Drawings (A)
A
A01
Parent for initialization drawings, Memory Clear,
Memory Clear and other settings
A20
A20.01
A20.02
Axis Initialization if using Function Blocks
Main initialization drawing Axis 1- RDAINIT if using FB
Main initialization drawing Axis 2- RDAINIT if using FB
High Speed Scan Drawings (H)
H
High Scan Parent, calls child drawings
H10
Machine common high-speed processes (cam master, PLS
master)
H10.01
Machine common high-speed process 1 (ex. cam master)
H10.02
Machine common high-speed process 2 (ex. PLS master)
H15
H15.01
H15.02
Reference output calculations (Axis trajectory)
Axis #1 Cam target position
Axis #2 Gear target position
H20
Individual axis motion controls for MCC or FB methods – call
grandchild drawings for individual axis
H20.01
Axis 1 High Speed motion control commands or function
blocks
H20.02
Axis 2 High Speed motion control commands or function
blocks
H25
H25.01
H25.02
H30
H30.01
H30.02
Group motion controls for Motion Program Language
method – call grandchild drawings for each motion program
Motion program control for Motion Group#1 (or optionally
MPM001)
Motion program control for Motion Group#2 (or optionally
MPM002)
High-speed Auxiliary machine devices (ex. PLS outputs,
diverter gates)
High speed Aux. device 1 (Glue Head #1)
High speed Aux. device 2 (Diverter Gate #1)
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Low Speed Scan Drawings (L)
L
Low Scan Parent, calls child drawings
L01
HMI interface – put communication code here if necessary
L01.01
HMI to MP Controller Conversions
L01.02
MP Controller to HMI Conversions
L10
L10.01
L10.02
L10.03
L20
L20.01
L20.02
L25
L25.01
L25.02
L30
L30.01
L30.02
L40
L40.01
L40.02
Machine common ladder sequencing (machine control
states)
Machine Common Ladder sequence (Control Mode [Auto vs
Manual], All Axes Normal, All Stopped, All Axes Enabled,
Home, etc)
Sequence A Motion Logic
Sequence B Motion Logic
Individual axis sequencing for MCC or FB methods (servo
axis, drive roll)
Axis 1 individual sequencing (Axis Normal, Servo On, Jog+,
Jog-, Low Speed motion control, etc.)
Axis 2 individual sequencing (Axis Normal, Servo On, Jog+,
Jog-, Low Speed motion control, etc.)
Motion Program sequencing and interlocking for MPL
method (combined groups of axes)
Group #1 motion sequencing and interlock (Low speed
Ladder sequence to control the group or Motion Program)
Group #2 motion sequencing and interlock (Low speed
Ladder sequence to control the group or Motion Program)
Low speed auxiliary machine devices (on/off devices, fan,
pump, air cylinder)
Aux. device 1 (pump#1)
Aux. device 2 (fan #1)
Machine Constants
Axis 1 Constants
Axis 2 Constants
Now the systems functional specifications are documented, motion-programming methods are
selected in addition to the program architecture. With the control application outlined, it is now
viable to accurately allocate memory for coding the application as discussed in the next section.
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MEMORY ALLOCATION
What is Memory Mapping?
Memory mapping is the recommended layout of MP2000 memory. Memory mapping defines the
layout for both global and local registers and is intended to keep the data as organized as
possible. A useful tool is available to define memory, refer to document eng.MCD.05.097 (Best
Practices Global Memory Registration Map).
Why is it important?
Memory mapping is important because it provides a consistent layout that increases program
flexibility, and reduces development and troubleshooting time
Memory mapping increases program flexibility for many reasons. Grouping information together
can be beneficial for many reasons, such as:
1) Ease and speed of transfer (HMI)
2) Cam tables
3) Recipe tables
Troubleshooting time is reduced when a consistent memory map is followed; errors are easily
diagnosed since the range of registers to be monitored is localized. Troubleshooting time is also
reduced because as the user programs additional applications using a consistent memory map,
the user gains familiarity with the layout and is able to navigate the MP2000 memory faster.
Lastly, having an organized and easy-to-navigate memory map also helps to reduce
development time. Using a consistent memory map eliminates the setup time required to layout
the memory, as well as providing a proven and robust memory layout to eliminate confusion and
reduce programming errors.
Memory mapping with function blocks
When using functions blocks, the function block RDA (reserved data area) is MW30000MW65535, meaning that these registers are reserved for function blocks and cannot serve the
user in any other capacity. The allowable range for user addresses when using function blocks is
MW00000-MW29999.
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D registers for working memory
Global memory should be reserved only for data that is used by multiple drawings (or additional
components such as an HMI). Data only used by one drawing should be kept in the D registers
of the specific drawing to minimize global memory usage.
The MP controller has seven types of memory. Proper allocation of this memory will greatly
simplify programming, debugging, maintenance, and transferability of a given project. Memory
can be allocated automatically or manually. A brief explanation of memory types and their usage
will assist the user in determining the proper allocation method to use. Below are the types of
memory available; followed by the abbreviation used in parenthesis, physical size, and a brief
description of their usage.
1) Global memory registers
a. Data (M) 64k
“M” registers are shared by all drawings. Used as interfaces between drawings.
Register number nnnnn is expressed as a decimal number.
b. System (S) 8k
“S” registers provided by the system. Register number nnnnn is expressed as a
decimal number. When the system is started, SW00000 to SW00049 are cleared
to 0
c.
Inputs (I) (Physical/Motion) 64k
“I” registers used for input data. Register number hhhh is expressed as a
hexadecimal number.
d. Outputs (O) (Physical/Motion) 64k
“O” registers used for output data. Register number hhhh is expressed as a
hexadecimal number.
e. Constants (C) 16k
“C” registers can be read only in the program. Register number nnnnn is
expressed as a decimal number.
2) Local (Drawing Specific)
a. General purpose (D) up to 16k
D registers are unique to each drawing and can be used only in the
corresponding drawing. The user of the MPE720 specifies the actual range used.
Register number nnnnn is expressed as a decimal number.
b. Constants (#) up to 16k
“#” registers can be read only in the corresponding drawing. The user of the
MPE720 specifies the actual range used. Register number nnnnn is expressed
as a decimal number.
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Automatic Address Allocation
What is it?
Automatic Address Allocation is a feature in MotionWorks that automatically assigns a register
location to a user-defined symbol based upon the kind, data type, and tag information entered by
the user.
“Symbol” – variable name assigned to a specific register
“Tag” – a user-defined label that can be used to group variables or
registers
How does it work?
MotionWorks maintains a register map of the symbol and data type assigned to each register. As
new symbols are entered into the register list and assigned tags, MotionWorks places the new
symbol in the lowest available address for that tag range. Users enter tag names and define the
register range and scope (global or local to a specific drawing) for each tag name in the
automatic address allocation section of Symbol Manager.
Register automatically
assigned
User-defined
information
Selected
Tag
Fig 2. Using Automatic Address Allocation
Advantages
Using Automatic Address Allocation allows the user to program in terms of symbol names rather
than by register addresses. By focusing on symbol naming conventions, users can properly
define their symbols in a way that allows them to most effectively organize their variables. Using
an organized and well thought-out group of symbol names helps to greatly minimize errant data
entering.
Using the Automatic Address Allocation also eliminates the chance of accidentally writing over
previously used registers. By assigning symbols to registers, the Automatic Address Allocation
register map recognizes how each register is being used, preventing symbols being assigned to
register locations that are already in use.
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Disadvantages
Automatic Address Allocation will not always start registers to be reserved for long and float data
types on even numbered addresses (as recommended by the MP best practices). A solution is
available to this problem as blocks of memory can be assigned within the auto-allocation function
to certain data types. A block of addresses (as shown below), starting at MW0200, is to be
reserved only for long data types. Since each long requires two registers, each long will start on
an even number address.
i.e.
MW0000 thru MW0009 – bit data types
MW0010 thru MW0199 – word data types
MW0200 thru MW0299 – long data types
MW0300 thru MW0400 – float data types
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Symbol naming & commenting conventions
Purpose of naming convention
The purpose of using the symbol naming convention is to increase overall ease-of-use.
Establishing a symbol convention that is easily understood and works well with the MotionWorks
Symbol Manager makes sorting and a viewing of symbols easy-to-do and maintains the
robustness of the program.
e.g.
Symbol
Axis###X_Velocity
Comment
[counts/sec]
X would be replaced by the first letter of the register type for that symbol:
B – bit type
W – word type
L – long type
F – float type
A – address pointer type
Recommendations
Symbol names should be written so their function is clearly understood and easy to sort in
MotionWorks. Below are some examples:
Symbol
Axis001L_Position
Comment
[counts/sec]
HMI_IndexCount
[number of indexes]
Machine_BeltLength
[inches]
Supervisory_Estop
[normally closed]
Tag naming convention for ease of searching and programming.
• Use real world names for easy to follow programs.
• By putting units in comments, this displays in ladder elements, again for ease of
understanding program.
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DEVELOPING CODE
With the memory allocated and symbol naming conventions completed, code is ready to be
developed as decided by the user’s evaluation of the programming methods.
The application is ready to be translated to executable code using Ladder, Motion Programs or
Function Blocks. When translating the application to executable code, there are many key
techniques used in developing a reliable, efficient application program. Key techniques for the
three programming methods are examined in this section.
Ladder Techniques
When programming in ladder, the user must consider the scan based I/O and Parameter update.
This is a key difference to understand for programmers familiar with structured text based
languages where the application directly controls the flow of instruction execution. In addition,
high and low speed scan drawings require special consideration when developing logic to assure
intended results.
Low Scan Interlocks
The MP Controllers have two user settable scan rates: high and low. As discussed in the
program architecture section, this allows the application to be optimized. Low speed drawings
typically contain non-speed critical machine sequences, such as I/O interfacing sequences and
HMI interface logic.
Axis Specific Low Scan Interlocks
Enabling an axis is typically performed in a low scan drawing as described in the drawing
architecture section. The goal here in Axis Interlocking is to check status of critical axis and
system alarms, and to create an ‘axis normal’ signal. The axis normal signal will be used to allow
the ‘servo enable’ signal to turn on, and remain on. If an error occurs during any mode of
operation (such as manual mode or automatic production mode) then the servo on signal will turn
off, and the axis will stop motion.
In DWG L20.01, the first rung of code checks the entire status register IL8004 loads its status into
the Axis001_NoAlarms catch all bit for axis #1. Even though the IL8004 register catches all
alarms, it is helpful to summarize all the alarms with one bit to aid in visually troubleshooting if an
alarm occurs (see user manual for bit breakout). IL8004 catches alarms such as
IL8004 (Alarm Status for Axis #1)
- Servo Driver Errors
- POT/NOT (positive and negative over travels)
- Positioning Timeout, Excessive Error, excessive speed
- Servopack Parameter setting error, comm. error, encoder disconnect, etc
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DWG L20.01
Its important to verify the axis status by confirming that the controller is ready, IB80000 (Axis 1)
and the ServoPack is ready, IB80003 (Axis 1). MB00101D (Axis 1.) Breakout the main power on
bit. IB802C4 (Axis 1). In the above code, “Axis Normal” is one of the conditions required to
enable the servo. An alarm, loss of ServoPack power, or communication error will disable the
axis. Also note that the user input is in series with a rising edge one shot to prevent rapid
toggling of the enable signal.
A normally open contact for breaking the latch of the servo on reference MB001001 (Axis 1) is
common practice for machine control from using hardwired normally closed stop push buttons.
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Jogging the axis individually, which is typically a manual machine mode function, is also
interlocked in the low scan drawings. Typical logic includes an interlock to jog in each direction.
The interlocks typically check the axis status for normal, that the axis is enabled, the machine is
in manual mode and the over travel for the selected direction. Then if the jog interlocks are OK,
the user input is allowed to reference the axis to jog in the corresponding direction. Bits set in the
low scan drawing to reference the axis to jog then are used as contacts in the corresponding high
scan drawing to set the motion command code, feed speed reference and direction.
DWG L20.01
It is recommended to verify the axis is not already executing another command by monitoring the
servo command type response IW8008 (Axis 1) at the bottom of drawing L20.01 for interlocking
the axis commands as above for the axis jog references.
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Homing an individual axis is another typical low scan interlock as shown below. First, monitor the
axis to complete it’s home or zero point return, with the next rung used to actually initiate the
homing logic by setting the motion command code to “zero point return.” The third rung is the
“home completed” latch. Conditions that break the latch would be the axis is on and in automatic
mode. These conditions depend on machine operation and change to suit the application.
DWG L20.01
Interlocking for an individual axis to be commanded for automatic production is also typically
placed in the low scan drawing. Set the command bit for the axis to operate in production mode
in a common machine sequence drawing such as L10. Interlock the production reference with
individual axis conditions such as “axis normal” before actually commanding the “production” bit
to run.
DWG L20.01
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Non-Axis Specific Low Scan Interlocks
Other low scan interlocks include common machine sequences and control in the L10 drawings.
Typical low scan interlocks include machine mode and mode switching logic such as auto /
manual and homing.
L10 and its subsequent grandchild drawings (L10.xx) include common machine sequences,
where the status of dependant axes are summarized in for interlocking purposes. Logic in the
individual axis specific L20 drawings will be used to interlock in L10.
All “axes normal” summary for preventing any common action if an associated axis is abnormal.
DWG L10.01
All axes “Servo On” summary for preventing any common action if an associated axis is off.
DWG L10.01
All axes are idle prevents issuing a command that would expect axis response, such as cycle
start.
DWG L10.01
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Auto / Manual Mode Selection
DWG L10.01
System Homing Interlock and Control
DWG L10.01
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Auto Production Mode Interlock and starting
DWG L10.01
HMI interlock (limiting, setting, resetting, handshaking, interlocking)
Definition of information to be transferred initially (varies per application)
Purpose of Interlocking HMI
All command bits from an HMI to the controller should be programmed as latched momentary
signals. This provides added safety for any type of E-stop or power-off conditions that may
occur.
In the example below, the HMI_START is a command signal from the HMI that is read only on a
rising edge. The SYS_OK must be closed indicating that the system is operating properly before
motion can start. When the HMI_START bit has a rising edge, the MOTION_START coil is
activated and latched on until the SYS_OK bit goes low.
It is recommended to limit values from HMI so that errors are prevented (i.e. putting to small/large
of value into a register)
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Machine Interlocks
Machine interlocks are critical to allow the controller code to operate within the mechanical
limitations of the machine and assure safe, reliable, high performance operation. Machine
interlocks include conditions for sequencing operations where components may interfere with
each other, peripheral components interlocking such as labelers or heater controls, upstream and
downstream systems interlocks as well as safety system interlocks.
Axis Enable Interlocks
To prevent alarms or warnings, the machine safety circuit and amplifier power should be verified
before attempting to enable an axis. This is done in the individual axis low scan drawings with
the axis normal condition to enable an axis. By verifying the controller an amplifier is ready the
power will be on the amplifier and the communications will be synchronized, therefore the
controller will be able to enable the axis successfully.
DWG L20.01
Automatic Mode Interlocks
Before a machine can enable, the state all the axes must be normal and enabled, the safety
circuit must be intact and no faults can exist.
DWG L10.01
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Before the machine starts cycling in automatic production mode there must exist no faults on the
system and the machine must be in the ready to start state.
DWG L10.01
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A system homing sequence may have to account for physical interference and require other
components in a certain state for the sequence to advance. It is critical to include interlocks in
any machine sequencing to prevent damage. In this example, air pressure is required as well as
sensor to detect components are clear.
DWG L10.02 1
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Gearing
Creating a gear application mainly consists of scaling the incoming master pulses with a B/A ratio
and sending the result to the slave’s commanded position register. In the MP its possible to
perform these calculations in ladder on a scan by scan basis. In this mode, the calculation is
performed every scan, by taking the differential pulses of the master encoder (called Scan
Difference), applying the formula below, and generating a scaled slave position output. The
power of the MP platform allows adjustments to be made at each step of the calculation at the
rate of the program scan, thereby allowing the user to change the ratio on the fly. The resulting
scaled segments are accumulated in a register that is fed to the slave commanded position.
When scaling the master position segments, often the result is not an integer number; to avoid
loosing synchronization, the remainder must be stored and added on the next scan.
Therefore, the calculation done each scan should be:
Scaled Slave Position Segment = Scan Difference * B + Modulus of the Last Scan
A
The Process in steps:
1. Calculate the master position difference from the last scan and store the current
position.
Notice the use of SUBX and ADDX for proper calculation through the rollover point of a
32 bit register. These instructions perform “two’s complement math,” which results in the
correct answer even as one value crosses the rollover point. No math errors are
generated.
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2. Multiply the result by B and add the remainder from the last scan.
3. Divide the result of step 2 by A and save the modulus of the division so it can be
added in the next scan.
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4. Accumulate the calculated slave position in an accumulator register.
5. Map the accumulated result into the slave position command register.
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Waterfall Technique
Because it is possible to write directly to the motion registers in a Yaskawa MP controller, it is
good programming practice to write values to the register in only one place to simplify monitoring
or debugging. This practice is accomplished using local registers as accumulators to interact
with logic and to finally store a value to the actual motion register in one place. This method is
referred to as the waterfall technique. Another benefit to this method is the ability to load a
default value if no conditions explicitly call for another value.
This coding technique is accomplished in three sections:
1. A default, initialization, or last scan value is stored to the accumulator register.
2. A conditional value is loaded to the accumulator based on interlocks with other logic
values. This action overwrites the default value.
3. The final store occurs when the accumulator is copied to the actual motion register.
In the following example, the motion command code is set for axis 1. The default value is first
stored to zero, or NOP as a safety so that no action will be taken if a fault happens in logic below.
Note that DW00026 register is used as an accumulator in the code below, this will be described
in more detail later.
If jogging, homing or production is required, the corresponding motion command code is loaded
to the accumulator word DW00026 in the conditional section.
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Finally. the value of the accumulator word is unconditionally stored to the Motion Command
register for axis 1.
The Waterfall technique illustrates the suggested use of local registers, in particular the
accumulators. Best Practices recommends the use of the following specific local registers when
implementing the waterfall technique:
Accumulator Register Address Recommendation:
DW00026
16 bit integer accumulator
DW00027
16 bit logic (hexadecimal) accumulator
DL00028
32 bit long accumulator
DF00030
32 bit floating point accumulator
(ex. motion command code)
(ex. parameter number write)
(ex. position reference)
(ex. floating point references)
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Modulus Technique
When an axis repeats an operation indefinitely in one direction, it may be important to modulate it
to create a repeating saw tooth value for a machine cycle or cam profile. A start location and
condition may need to be determined also. Typically, most applications start at zero in the cam
table, but it can vary as it is application dependant.
In the following example of a modulus technique, the start location is the beginning of the cam
table and the condition is the ending of the machine cycle.
1. Calculate the master position difference from the last scan
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2. Increment the virtual master by the scan differential amount
3. Test the virtual master to see if the cycle modulus has been exceeded. If so, reset the
value of the virtual master to be within the machine cycle. When the modulus is
exceeded, set the virtual master to the accumulated scan counts that have exceeded the
machine cycle range.
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Delta Scan
The delta scan technique is a convenient method to calculate the change in position or value at
the scan rate. This is useful in creating a modulus function or saw tooth position change for a
virtual master that repeats cyclically. By using this method a saw tooth waveform is generated to
represent the change of position versus time. This technique is also useful in calculating speed
compensation that may be used to account for time delay due to network updates and the scan
of the drawings. The delta scan method is the same as for the modulus and gearing techniques,
repeated below for clarity.
1. Calculate the master position difference from the last scan
2. Increment the virtual master by the scan differential amount
The results can be multiplied by a given number of Mechatrolink network cycles for speed
compensation. This is possible because Mechatrolink network updates are deterministic.
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Handling Rollover
Use the math functions ADDX or SUBX to prevent miscalculations due to long registers, ML or
DL rollover. With 32 bit registers, the maximum and minimum decimal values are
+2,147,488,647 and –2,147,488,648, which correspond to 7FFF FFFF and 8000 0000 in Hex
respectively. For example, if IL8016 has rolled over from the positive or the negative side, the
IL8016 and ML00100 math would be as follows:
Positive Rollover:
–2,147,488,000 – (+2,147,488,000) = +1296
Negative Rollover:
(+2,147,488,000 – (–2,147,488,000) = -1296
Using ADDX and SUBX always guarantees that the result of the math operation is a valid
answer, and no error will be generated.
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TECHNICAL NOTE
MOTION APPLICATION ENGINEERING GROUP
Sequencing Techniques
Machinery is required to repeat processes accurately and consistently with robust control, without
intervention other than user clearing mechanical jams and user interface to prompt their actions.
When developing sequences using a machine controller, it is important to program for consistent
execution of tasks, with built in recovery functionality to handle sequence exceptions.
State Machine programming vs Step Sequencing
Step Sequencing is defined as motion or logic sequences programmed in steps using individual
bits of words to initiate and monitor the steps of the sequence. Another common practice is state
programming where states are defined by actions that take place. Transition conditions
determine the sequence, and the state is determined by an integer that is updated when a new
state is entered. Both methods are useful, below is a more detailed description of Step
Sequencing.
Step Sequencing Technique:
Most controller programmers use two different types of sequencing by bits.
1) Retained Step Sequencing: each step of the sequence is set true, and remains true
until the end of the sequence, or the sequence is aborted when all of the bits are
reset.
2) Toggle Step Sequencing: In each step of the sequence, a bit is set. Then there is a
corresponding bit representing that the step is completed, which toggles or resets the
initial step bit. When the sequence completes, then all the “step completed” bits are
reset. Some favor this method because steps that are completed should have no
interaction with active steps.
Regardless of the method selected, its recommended to use self-latching bits with the unlatching
bits between the branch and coil, not in the branch, as shown below.
DWG L10.01
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The Toggle Step Sequence technique uses a step complete bit (DB000011) to reset the
sequence bit that first initiated the step (DB000010). Note in the second rung the entire
sequence complete resets the done bit DB00001F.
DWG L10.02
The completion of the last sequence step should latch a sequence complete bit. Then the step
complete bits are reset by the “sequence reset” bit, or if the system changes auto mode the
sequence is aborted.
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TECHNICAL NOTE
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Rules For Motion Programming
The MP2000 series of motion controllers offer a powerful, yet flexible text-based motion
programming language that lends itself well to many applications, especially those that involve
linear interpolation or complex motion sequences. As always, the user is free to program as
desired, but experience has shown that following a few simple guidelines, as illustrated in this
section, will help the programmer produce a motion program and related ladder code that is
robust, easy to troubleshoot, and easy to modify.
These guidelines are explained in detail and illustrated with examples in the pages that follow.
•
Starting a Motion Program
•
Active Interlocks During Motion Program Execution
•
Stopping a Motion Program
•
Bit Handshaking between Motion Program and Ladder Code
•
Using WHILE loops in Motion Programs
•
Using PFORK, JOINTO, and PJOINT in Motion Programs
•
Using Subroutines in Motion Programs
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TECHNICAL NOTE
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Best Practice Rules For Using Motion Programs:
Initiating Motion Program
Before starting a motion program, ladder code should include interlocks that ensure the
following conditions are true:
•
All group axis servos must be ON (MB300010 in H25)
•
All group axes must be in “NOP” (no operation) mode (MB300013 in
H25)
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•
No motion program is running, halted or in alarm for the specified
group. (MB300018).
In H25:
It is this element (MB300011) that interlocks the
starting of any motion program
In H25.01:
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TECHNICAL NOTE
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Interlocking During Execution
During the execution of the motion program:
• Interlocks should exist in the ladder code to keep it from changing global registers that
the motion program writes to. These registers include “M”, “O”, and any group axis
output registers. (Use the ladder’s “waterfall technique” – hold the register value.
Example OW8008 and OW8088 in drawings H20.01 and H20.02 respectively.)
When a Motion Program is
executing, and a motion program
instruction has changed this motion
register (OW8008), the value is
simply written to it where the MSEE
instruction exist in the ladder code.
This store simply places that value in
a local register (DW00026) used as
an accumulator.
When a Motion Program is
executing, the contacts on these two
(6 & 7) rungs are false. Therefore the
ladder code leaves the OW8008
register unchanged.
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The value in the accumulator, is loaded
in the motion register (OW8008.)
•
Reading any global registers (M, I, O, S, C) are of no issue or concern.
Stopping a program that is executing:
•
Expect to issue an alarm clear after halting (stopping) a motion program
that was running. Expect an Alarm if the motion program running
continuously was stopped. This means the program was either
stopped, paused, or in single block mode when interrupted.
•
Include ladder logic to flag the operator (or upper controller or other MP
code) that the motion program was halted or alarmed.
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Rules for bit handshaking or setting any global bit with Motion programs:
Understand that the instruction to turn a bit ON or OFF in a motion program is equivalent
to a SET COIL and RESET COIL respectively in the ladder code.
•
Ladder logic must exist to RESET any bit that was SET in the Motion
Program, in case that program is stopped or begins to execute again.
(MB300014 and MB300015 in MPM004, and H25.01)
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Rules for using a WHILE – WEND Loop in Motion programs.
•
Example: An incremental move that repeats until the loop condition is
satisfied.
•
Code that takes more than one scan to execute may cause a watchdog
alarm. Avoid this alarm by including the EOX instruction in the loop.
Rules for using parallel processing “PFORK –JOINTO - PJOINT”.
•
Inside the parallel process only motion and global (M, O, I, S, C)
register handshaking (MByyyyyb = 1 , IOW MByyyyyb = =1, MWzzzzz
== 1234) instructions should be used. (Example: Home an axis with
absolute encoder [using MOV] and an axis with an incremental encoder
at the same time.)
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Rules using motion program subroutines:
•
Like any programming environment’s subroutine, motion program
subroutines should be used to recall a repeatable process. (Example:
writing to Servopack Parameters.)
Before the subroutine is called
the “main code” prepares the
operation. The parameter
number and value to write.
The subroutine is called.
The subroutine does the parameter write.
Register Ranges to use and Why:
When using motion programs the programmer should not use Function blocks.
Therefore, the function block’s Reserved Data Area (RDA) is available for Bit Handshaking and
data sharing between Motion Programs and ladder code.
MP900: MW00100~MW03999
MP2000: MW30000~MW65535
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