MMQ-G User Manual - Systron Donner Inertial Division

MMQ-G User Manual - Systron Donner Inertial Division
MMQ VG-200-400
MMQAHRS-200-400
User’s Guide
™
RELEASED DOCUMENT
DATE: 01/22/2010
Sales and Customer Service
Systron Donner Inertial
Custom Sensors & Technologies
2700 Systron Drive
Concord, CA 94518
Tel: 925-979-4500
Fax: 925-349-1366
Web: www.systron.com
E-mail: [email protected]
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Information to the user - The user of this device is
cautioned that changes or modifications not expressly
approved by SDI could void the user’s warranty.
Proprietary Notice - Information provided by Systron
Donner Inertial is believed to be accurate and reliable.
However, no responsibility is assumed by Systron
Donner Inertial for its use, nor any infringements of
patents or other rights of third parties which may
result from its use. No license is granted by
implication or otherwise under any patent rights of
Systron Donner Inertial. Systron Donner Inertial
reserves the right to change circuitry or software at
any time without notice. This document is subject to
change without notice.
No part of this document may be reproduced, stored
in a retrieval system, or transmitted, in any form or by
any means, mechanical, electronic, photocopying,
recording, or otherwise, without prior written
permission of Systron Donner Inertial.
Printed in the United States of America. ©2006 The Systron Donner Inertial Company. All
rights reserved.
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TABLE OF CONTENTS
Chapter 1- Introduction.........................................................................................................................................5
Overview ...................................................................................................................................................5
About This Book.......................................................................................................................................6
Chapter 2- Attitude Determination Concepts .....................................................................................................7
What is Attitude Determination? ............................................................................................................7
Quartz IMU General Theory...................................................................................................................10
Attitude Determination General Theory ...............................................................................................13
Chapter 3- System Overview..............................................................................................................................15
System Configuration ............................................................................................................................15
System Technical Description ..............................................................................................................16
Chapter 4 - Operation..........................................................................................................................................25
Operating Modes ....................................................................................................................................25
IMU Operation.........................................................................................................................................26
Chapter 5- Hardware Integration .......................................................................................................................28
Overview .................................................................................................................................................28
Electrical Interface .................................................................................................................................28
Connector Types ....................................................................................................................................34
Cable Considerations ............................................................................................................................35
Chapter 6- Magnetometer Interface...................................................................................................................37
Overview .................................................................................................................................................37
Magnetic Measurement..........................................................................................................................38
Hardiron/Softiron Calibration................................................................................................................39
Magnetometer Data Interface................................................................................................................42
Chapter 7- Software Integration.........................................................................................................................43
MMQ VG and MMQ AHRS to Host Vehicle Data Interface/Definitions ..............................................43
Serial Interface Functionality ................................................................................................................43
Chapter 8- End Product Applications ...............................................................................................................49
Overview .................................................................................................................................................49
Product Application Examples .............................................................................................................49
Appendix A- Frequently Asked Questions .......................................................................................................51
Appendix B- Getting Started ..............................................................................................................................54
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TABLE OF FIGURES
Figure 1 MMQ IMU Functional Block Diagram ................................................................................................. 10
Figure 2 Simplified Block Diagram Quartz Rate Sensor ................................................................................. 11
Figure 3 MMQ VG and MMQ AHRS Form Factor.............................................................................................. 16
Figure 4 MMQ VG and MMQ AHRS Dimensions .............................................................................................. 21
Figure 5 MMQ VG and MMQ AHRS Axis Definition ......................................................................................... 22
Figure 6 MMQ (J1) Electrical Interface .............................................................................................................. 30
Figure 7 Host Vehicle RS-232 Output Circuit ................................................................................................... 32
Figure 8 Host Vehicle RS232 Input Circuit ....................................................................................................... 33
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Chapter 1- Introduction
MMQVG MMQAHRS
Overview
Systron Donner Inertial (SDI) has developed a family of
vertical gyro and attitude and heading reference products
(VG and AHRS) that use the latest solid-state inertial
sensor technology.
The MMQ VG offers a unique combination of the Systron
Donner Inertial solid-state Inertial Measurement Unit (IMU)
and advanced software that calculates a Vertical Gyro (VG)
solution from the gyro and accelerometer sensors. The
MMQ VG's MEMS quartz rate sensors and MEMS
accelerometers make up an IMU system that is used to
calculate a highly accurate Roll and Pitch angle solution in
varying dynamic applications.
The MMQ AHRS expands on the MMQ VG model by
combining the Systron Donner Inertial solid-state Inertial
Measurement Unit (IMU) and advanced software that
calculates an Attitude and Heading Reference (AHRS)
solution from the gyro and accelerometer sensors, and an
external 3-axis magnetometer. The MMQ AHRS's MEMS
quartz rate sensors and MEMS accelerometers make up an
IMU system that is used to calculate a highly accurate Roll,
Pitch and Heading angle solution in varying dynamic
applications. As in the MMQ VG, Roll and Pitch are
stabilized by the accelerometers, and Heading is stabilized
by an external 3-Axis magnetometer.
The user can configure the MMQ VG and MMQ AHRS to
output data at various sample rates with extremely low
output rate jitter, and the data output format is simple to
understand containing the 6 sensor outputs, the angle
outputs, a Built-In-Test (BIT) word output and a multiparameter revolving word output that provides system
information including version string. The MMQ AHRS
combines tremendous performance and versatility with an
extremely compact size, low power consumption and low
weight.
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These solutions offer an affordable suite of compact and
lightweight systems that are ideally suited for
Heading and Attitude Applications, Targets and drones, EO/IR
Stabilization, Unmanned Aerial Vehicles, Remotely Operated
Vehicles (Underwater), General Aviation (Experimental), Land
Navigation, Robotics, and Electronic Flight Instrumentation
System (EFIS) Integration
Additional technical data, physical characteristics, operation,
and system integration information for the MMQ VG and
MMQ AHRS products are presented in subsequent chapters
of this guide.
About This Book
This guide provides basic attitude determination concepts,
configuration, operation, and characteristics of the system,
and defines the mechanical, electrical, and data interfaces of
MMQ VG and MMQ AHRS to the Host Vehicle (HV).
This guide will discuss and illustrate some possible system
applications for commercial and military markets, and will
help the end-user determine how to use the MMQ VG and
MMQ AHRS features.
The glossary contains abbreviations of terms commonly used
by SDI and in the navigational and inertial fields, as well as
some terms common to commercial electronics and software
fields.
Note pages have been included to allow the designer to jot
down notes for quick easy reference that might otherwise be
misplaced.
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Chapter 2- Attitude Determination
Concepts
What is Attitude Determination?
Attitude Determination is the art and science of estimating a
vehicle’s attitude angles roll, pitch and heading. When
navigating for long periods of time, a slight error in direction
will create a sizable distance off course. This shows that the
efficiency of a vehicle depends ultimately on the attitude
determination accuracy.
The science of attitude determination can be reduced to five
basic questions, and the algorithm must be capable of
obtaining quick and accurate answers to them.
•
What is the vehicle’s heading?
•
What is the vehicle’s attitude (roll and
pitch)?
•
What is the vehicle’s acceleration?
•
What is the vehicle’s rate of rotation?
Answer these questions and you have the solution to and
attitude determination system. With proper equipment, these
questions can be answered with reasonable accuracy.
The primary task of attitude determination is the estimation of
a vehicles present orientation. Inertial attitude propagation is
the method of accurately and continuously extrapolating a
vehicle's attitude and heading, by processing changes in its
motion as sensed by inertial instruments.
A Vertical Gyro (VG) and an Attitude and Heading
Reference System (AHRS) measure changes in the vehicles
body rates through the use of accelerometers, gyroscopes and
an internal or external tri-axial magnetometer. This
information is fed to a computer that is used to keep track of
attitude and to control any attitude drift using the
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acceleration gravity vector and earth’s magnetic field vector
to continuously stabilize an indication of attitude and
heading. Today these same instruments typically provide
rate and state data to other avionics subsystems such as
weapon computers, flight controls, or radar sensors.
VG and AHRS systems make their measurements with
respect to inertial space. Inertial space is a reference frame,
consisting of a set of axes that do not rotate, and has no
acceleration from its origin relative to the average position of
the fixed stars. Any set of rigid axes moving with constant
velocity, and without rotation relative to inertial space, also
constitutes an inertial reference frame.
Heading
Heading is commonly known as compass direction, or the
direction that the vehicle points. True heading is defined as
the angle in the local horizontal plane measured clockwise
(about a downward vertical) between North and a vertical
plane, containing the ship’s, aircraft’s, or other vehicle’s
longitudinal axis (with an aircraft, this axis is known as the
thrust axis).
Attitude
Attitude is defined as the angular position of a ship, aircraft,
or other vehicle, determined by the relationship between its
axes and a reference datum, such as the horizon or a
particular star. Attitude parameters are defined in terms of
three “Euler” angles: true heading, pitch, and roll. See the
previous paragraph for true heading.
Pitch is the angle measured in the vertical plane between a
vehicle’s longitudinal axis and the horizontal axis (nose up in
an aircraft would be positive).
Roll is the angle measured about the vehicle’s longitudinal
axis that will rotate the vehicle from a horizontal orientation
(such as an aircraft’s wings being normally horizontal, to the
actual flight orientation).
An example of roll is a climbing right hand turn from a level
northerly flight path direction, generating a positive heading,
pitch, and roll angle. A drift angle can be generated by
crosswinds, causing the aircraft to point in the direction of
the wind, rather than along the ground-referenced velocity
direction.
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Acceleration
Since the velocity of a body has both magnitude and
direction, a change in velocity occurs whenever:
•
The body's rate of motion changes while
its direction remains the same.
•
The body's direction of motion changes
while its rate of motion remains the same.
•
The body's rate and direction of motion
change simultaneously.
Whenever the velocity of a body changes in any manner, the
body is said to be accelerating.
Gravity
In addition to the forces caused by the motions of the vehicle
and the Earth, the system is subject to the mass attraction, or
gravitational force of the Earth, which is the most significant
force acting on inertial instruments.
Gravity’s interaction with the Earth's rotational forces is
responsible for the very shape of the Earth itself. The shape
of the Earth is fundamental to terrestrial navigation, since the
designation of a system’s position is only as precise as the
relationship between the describing coordinates and the
Earth's shape. Gravitational attraction is a property of matter
(inertial mass) that is possessed by all material bodies.
Earth Magnetic Field
The earth’s magnetic field provides a constant vector from
north (magnetic north) can be derived. Created by the
relative motions of the earth’s inner core, the earth’s
magnetic field is not actually static and does drift or move
over the course of time. However the amount of motion is
negligible compared to the determination of a vehicle’s
instantaneous forward heading.
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Quartz IMU General Theory
The IMU (Figure 1) is designed around six single-axis
sensors, three Quartz Rate Sensors (QRS) and three
Accelerometers.
The QRS output is an analog sinusoid, which is converted to
a digital signal by the electronics portion. The IMU also
monitors health, and provides sensor compensation.
QRS
QRS
DRIVE,
DEMOD
AND
INTERFACE
CIRCUITRY
QRS
ANALOG
ACCEL
ACCEL
TO
DIGITAL
DIGITAL
CONVERSION
SIGNAL
PROCESSOR
INTERFACE
CIRCUITRY
TEMPERATURES
AND
VOLTAGES
ACCEL
POWER
SECONDARY
VOLTAGES
CONVERSION
POWER
IN
Figure 1 MMQ IMU Functional Block Diagram
The IMU portion of the MMQ VG and MMQ AHRS
contains the electronics that process the raw sensor signals
for compensation. It provides gyro rate information and
acceleration information that is used by the VG and AHRS
algorithms to determine vehicle attitude.
Accelerometer Principles
The basic principle of the open loop Accelerometer is to
measure the deflection of a mass on the end of a flexible
beam. The displacement of this mass is then used to measure
the specific force applied to the sensor.
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An acceleration sensor can be designed using a proof mass,
so that the force transmitted from the case of the
accelerometer through the beam to the proof mass is
proportional to acceleration.
The deflection resulting from this force will vary according
to the acceleration, and may be measured by the change in
capacitance between the proof mass and fixed, parallel plates
placed either side of the mass.
QRS Principles
The MMQ IMU uses a dual tuning fork design shown in
Figure 2. The drive fork is set into oscillation at its natural
frequency. When the device is rotated about the vertical
axis, the Coriolis force causes the tines to oscillate at the
drive frequency, which is orthogonal to the plane of the fork
Figure 2 Simplified Block Diagram Quartz Rate Sensor
The Coriolis motion is transmitted to the pickoff tines,
causing them to oscillate orthogonal to the plane of the fork.
The amplitude of the pickoff motion is proportional to the
velocity of the drive tines and the angular rate.
The pickoff motion is detected by electrodes attached to the
pickoff tines. This pickoff signal is demodulated with respect
to the reference drive signal, to give a DC output
proportional to the input rate.
To maintain scale factor stability, an automatic gain control
loop around the drive tines ensures a constant oscillation
amplitude over temperature.
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QRS Technological Advances
Micromachining
has opened up the
potential of using
crystalline
structures as the
complete sensor
element.
The technological approach of micromachining has opened
up the potential for using crystalline structures as the
complete sensor element. This approach is used in
manufacturing the MMQ VG and MMQ AHRS by using
quartz for the fork material, and by using deposited
electrodes on both the drive and pickoff sides.
The mount that supports the quartz element provides
isolation to maximize Coriolis coupling torque into the
pickoff tines. Drive and pickup voltages are also routed via
the mount.
The drive and signal processing electronics are contained
within an Application Specific Integrated Circuit (ASIC)
chip, providing a direct current (DC) input/output capability
for ease of interfacing.
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Attitude Determination General Theory
Attitude determination is divided into two separate entities,
an attitude state propagation, and an attitude state stabilizer.
In the first entity rate sensor measured angular rate
information is integrated in time to propagate the attitude
state in a component referred to as attitude processor. If the
initial attitude of the vehicle was known exactly and if the
rate sensors provided perfect readings then the attitude
processor would suffice. However the initial attitude is
unknown and rate sensors typically provide corrupted data
due to bias drift and turn-on instability.
In the second entity, a VG and AHRS attitude stabilizing
component provides on-the-fly corrective signals to the
attitude processor trajectory (referred to as a corrective rate
signal). The accelerometers provide a roll and pitch angle
attitude reference using gravity for the VG solution, and the
magnetometers provide a magnetic north heading reference
using the earth’s magnetic field for the AHRS solution.
The primary functions of the MMQ VG are:
1. Sense inertial motions, specifically, linear acceleration and
rotational rate
2. Sense internal thermal states (instrument temperatures) and
voltages
3. Convert sensed analog inputs to digital values (both inertial
and thermal inputs)
4. Digitally filter inertial inputs
5. Compensate filtered inertial inputs for thermal fluctuations
and voltage levels
6. Initialize a system cosine rotation matrix for roll and pitch
angles using the accelerometers as level indicators
7. Convert the cosine rotation matrix into a system quaternion
8. Use the compensated rotational rates to propagate a system
quaternion
9. Use the accelerometers gravity reference to generate restoring
rates that stabilizes the system quaternion for the roll and
pitch channel
10. Extract roll and pitch angles from the stabilized quaternion
11. Prepare and deliver roll and pitch data on the serial output
channel
The primary functions of the MMQ AHRS are:
1. Provide the calculations performed in the VG component
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2. Provide and interface for continual Magnetometer vector
input (via an input message)
3. Initialize a system cosine rotation matrix for roll, pitch and
heading angles using the accelerometers as a level indicator
and the magnetometers as a heading indicator
4. Use the system roll and pitch angles to level the
magnetometer vector
5. Calculate a leveled magnetic heading
6. Provide a method of calibration for the magnetometers to
compensate for hardiron and softiron effects
7. Use the magnetic heading reference to generate a restoring
rate that stabilizes the quaternion for the yaw channel
8. Extract the system roll, pitch and heading angles from the
stabilized quaternion
9. Prepare and deliver heading data on the serial output channel
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Chapter 3- System Overview
System Configuration
The MMQ VG and MMQ AHRS have been designed to
provide a low-cost solution for applications that require a
vertical gyro or attitude and heading reference system. As
introduced earlier in this guide, the MMQ VG and AHRS are
composed of two basic elements: the IMU portion (based on
the original MMQ50 IMU) and advanced attitude
determination software.
The IMU portion provides gyro rate and acceleration
information about three axes at a 400 Hz rate. The IMU uses
micro-machined quartz rate sensors and silicon
accelerometers to achieve low cost, weight, and volume.
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System Technical Description
The MMQ VG and MMQ AHRS systems, shown in Figure
3, combines the SDI MMQ50’s high-rate, inertial gyro rate
and accelerometer outputs, and advanced attitude processing
software to compute a complete attitude and heading
solution.
Figure 3 MMQ VG and MMQ AHRS Form Factor
In normal operation attitude and heading are computed based
on integrated inertial data. This inertial solution is corrected
using a feedback rate control algorithm, which uses the
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accelerometers and external magnetometer data to stabilize
the roll, pitch and heading outputs.
The MMQ VG and AHRS initialize the roll, pitch and
heading angles based on the first set of available sensor data.
Although a static initialization is preferable, the system can
be initialized in both stationary and dynamic environments.
For a dynamic environment, there could be a large initial
attitude angle error if the initialization occurs during an
acceleration maneuver. As the dynamics subside and a
straight and level condition is achieved, then angles will
automatically stabilize to the proper solution.
System Operation
Operation of the MMQ VG and MMQ AHRS systems
requires conditioned power, and an RS-232 bi-directional
serial port to interface with MMQ VG and MMQ AHRS
data.
The bi-directional serial port is used to output the standard
message containing gyro rates, accelerations, Euler angles,
status information and a revolving parameter word. Input
control commands are received on this port.
In a stationary or dynamic environment, the MMQ VG and
MMQ AHRS power up and perform a power-on Built In
Test (BIT). The MMQ then waits for stable sensor
performance. Once the sensors have stabilized, then the VG
and AHRS algorithms initialize. The attitude vector (roll,
pitch and yaw) is initialed using the accelerometer and input
magnetometer data.
Then the MMQ system starts the attitude processor and
attitude stabilizer portions of the algorithm. The normal
output message then begins to output at the user desired rate.
The default rate is 100 Hz, but the user can command 50Hz,
100 Hz, 200 Hz and 400 Hz output rate.
Product Performance
MMQ VG Specifications
The MMQ VG performance specifications are detailed in the
Table 3-1 below.
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Table 3-1. MMQ VG Specifications
PHYSICAL CHARACTERISTICS
Part Number
Size (Vol.)
Weight
Power
I/O
MMQ VG-200-400
9.0 in3 (1.88”W x 1.88”D x 2.55”H) (48 mm x 48 mm x 65 mm)
<0.50 lbs (<0.227 kg)
+ and – 12 Vdc at < 5 watts total
RS-232 – 400 Hz Output Rate with < 100 microsecond jitter
ATTITUDE PERFORMANCE
Static Accuracy (Roll/Pitch)
< 0.5 Deg
Dynamic Accuracy (Roll/Pitch)
1.5 Deg RMS – Tested to TSO-C4c bank and pitch performance standards
RATE CHANNELS
Range
Bias Turn-on to turn-on Stability (fixed
temp)
Bias In-run Stability (at any
temperature)
White Noise (angle random walk)
Scale Factor error
Alignment
Bandwidth
200°/ sec
≤100°/hr, 1 σ
50-200°/hr, 1 σ
0.3 °/rt-hr (0.005 °sec/rt-Hz)
≤5000 ppm (0.5%)
≤5 mrad
50 Hz, nominal
ACCELERATION CHANNELS
Range
Bias Turn-on to turn-on Stability (fixed
temp)
Bias In-run Stability (at any
temperature)
White noise (velocity random walk)
Scale Factor Error
Alignment
Bandwidth
+/- 10g
≤2.5 mg, 1σ
≤3 mg, 1 σ
0.5 mg/rt-Hz
≤5000 ppm (0.5%)
≤5 mrad
50 Hz, nominal
ENVIRONMENTAL
Temperature Range
Vibration, random
Shock, operating
Altitude
-54°C to +70°C (operating)
6.0g rms, 20Hz –2kHz, flat Meets DO-160D Curves C, C1
30g, powered Meets DO-160D operational shock and crash safety
35,000 ft. Meets DO-160D Category C
MMQ AHRS Specifications
The MMQ AHRS performance specifications are detailed in
the Table 3-2 below.
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Table 3-2. MMQ AHRS Specifications
PHYSICAL CHARACTERISTICS
Part Number
Size (Vol.)
Weight
Power
I/O
MMQ AHRS-200-400
9.0 in3 (1.88”W x 1.88”D x 2.55”H) (48 mm x 48 mm x 65 mm)
<0.50 lbs (<0.227 kg)
+ and – 12 Vdc at < 5 watts total
RS-232 – 400 Hz Output Rate with < 100 microsecond jitter
ATTITUDE AND HEADING PERFORMANCE
Static Accuracy (Roll, Pitch, Heading)
< 0.5 Deg
Dynamic Accuracy (Roll/Pitch)
Dynamic Accuracy (Heading)
1.5 Deg RMS – Tested to TSO-C4c roll and pitch performance standards
3.0 Deg RMS – Tested to TSO-C6d heading performance standards
RATE CHANNELS
Range
Bias Turn-on to turn-on Stability (fixed
temp)
Bias In-run Stability (at any
temperature)
White Noise (angle random walk)
Scale Factor error
Alignment
Bandwidth
200°/ sec
≤100°/hr, 1 σ
50-200°/hr, 1 σ
0.3 °/rt-hr (0.005 °sec/rt-Hz)
≤5000 ppm (0.5%)
≤5 mrad
50 Hz, nominal
ACCELERATION CHANNELS
Range
Bias Turn-on to turn-on Stability (fixed
temp)
Bias In-run Stability (at any
temperature)
White noise (velocity random walk)
Scale Factor Error
Alignment
Bandwidth
+/- 10g
≤2.5 mg, 1σ
≤3 mg, 1 σ
0.5 mg/rt-Hz
≤5000 ppm (0.5%)
≤5 mrad
50 Hz, nominal
ENVIRONMENTAL
Temperature Range
Vibration, random
Shock, operating
Altitude
-54°C to +70°C (operating)
6.0g rms, 20Hz –2kHz, flat Meets DO-160D Curves C, C1
30g, powered Meets DO-160D operational shock and crash safety
35,000 ft. Meets DO-160D Category C
System Power Requirements
The following is a brief overview of MMQ VG and MMQ
AHRS power requirements, including input voltage, current
and over voltage protection.
Input Voltage
The prime power input voltage to the MMQ is +/-12V Vdc
as measured at the input. The nominal range is 11V to
13Vdc.
Current
The typical start-up current drawn by the unit is up to
400mA on the positive supply and 280mA on the negative
supply during the first 500msec. The typical steady-state
current drawn by MMQ-G is +280mA at +12v and –80mA at
–12V.
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Input Voltage Transient Protection
MMQ contains a transient absorption zener diode that
clamps both the positive and negative input voltages at 17V.
Signal Interface Environment
MMQ provides one full-duplex, asynchronous RS-232 serial
data port for communicating with the Host Vehicle.
Physical Dimensions
This section describes the MMQ envelope dimensions,
installation requirements, mass properties, coordinate
systems, and polarities.
Envelope Dimensions
The MMQ envelope dimensions are shown in Figure 4:
Width = 2.48”, Depth = 1.87”, Height = 2.78”, Volume =
12.9 cu in.
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Figure 4 MMQ VG and MMQ AHRS Dimensions
Installation Requirements
The MMQ must be mounted to the host vehicle using four #6
socket cap screws, tightened to a torque between 8-12 in-lbs.
IMPORTANT!
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The MMQ must be securely mounted to a good
thermally conducting (metal) surface during
operation to prevent thermal damage. (Nominal
Power dissipation is approximately 4.3W, and the
mounting base temperature must be kept below
85°C.)
Mass Properties
The weight of the MMQ is <0.23 kilograms (<0.50 pounds).
Boresight / Axis Alignment
Mechanical system axes are a right-hand orthogonal set
labeled x, y, and z, as shown in Figure 5.
Figure 5 MMQ VG and MMQ AHRS Axis Definition
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Environmental Specifications
The MMQ environmental specifications are provided in
Table 3-3. These conditions are without safety and/or
intensification factors. Under these conditions the MMQ will
perform within the limitations defined herein.
Table 3-3. MMQ Environmental Specifications
Test Condition
Test Method
MIL-STD-810 F, Section 500.0
Altitude
Specification
A
T
Extended to 60,000 ft
Operating
X
Storage
X
Temperature Range
X
-40 to +71°C
Operational
MIL-STD-810 F, Section 501.3
Storage (nonoperational)
MIL-STD-810 F, Section 502.3
Temperature Shock
MIL-STD-810 F, Section 503.3
Humidity
MIL-STD-810 F, Section 507.3
Acceleration, Operating
MIL-STD-810 F, Section 513.4
4 G (performance), 20 G (endurance)
X
Vibration, Performance
MIL-STD-810 F, Section 514.5,
Procedure I.
6 G rms, flat spectrum, 20 Hz–2 kHz
X
Vibration, Transportation
MIL-STD-810 F Method 514.5,
Section 2.2.1 (Category 4)
0.2, 0.74, 1.04 grms, 3 hr/axis, flat spectrum, 20 Hz-2
kHz
X
Shock, Endurance
MIL-STD-810 F, Section 516.4
30 G, 11ms
X
Shock, Operating
MIL-STD-810 F, Section 516.4
20 G, 11ms
X
X
-40 C to + 71 C, 0.42 C/s
X
X
Dynamics
X
Velocity
500 m/s
Acceleration, Perf.
4G
Acceleration, Oper.
20 G
Angular Rate Range
200 deg/sec
X
200 deg/sec
X
Angular Rate,
Calibrated
A = Verified through analysis
X
X
X
T = Verified through test
Temperature
The MMQ will meet its performance requirements during
and after exposure to temperatures from -40 degrees C to +
71 degrees C. Heat is dissipated by conduction through the
base mounting plate.
Vibration, Performance
The MMQ will meet its performance requirements during
and after exposure to a 6 GRMS random vibration levels, flat
profile 20-2,000Hz, in each of the three orthogonal axes.
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Shock
The MMQ will meet its performance requirements after
exposure to a 30 g, 11 millisecond, half-sine shock applied in
each direction of the three orthogonal axes. MMQ will
operate with full accuracy during and after exposure to
shocks less than or equal to 20 g, 11 ms, half-sine pulse.
Electro-Magnetic Interference and Compatibility (EMI/EMC)
The MMQ is intended to be embedded in a system that
provides EMI/RFI protection. Contact your local SDI
applications engineer for details.
MMQ Reliability
The Mean Time Between Failures (MTBF) of MMQ is no
less than the values shown in Table 3-4. These values were
established using MIL-HDBK-217F analysis methods and
supplemented by commercial parts data.
Table 3-4. Mean Time Between Failures
MIL-HDBK-217 Environment
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MTBF, hours
Ground, Benign @ 35 C
44,736
Airborne, Uninhabited Fighter @ 35 C
15,485
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Chapter 4 - Operation
Operating Modes
The processing state of the MMQ-G at any particular time is
defined by a mode. MMQ-G utilizes the following operating
modes:
•
Test
•
Normal
After startup, the MMQ-G sequences automatically through
Test mode to Normal mode. In Normal mode, attitude
estimation is performed based on INS data.
The processing performed by MMQ VG and MMQ AHRS
during the two modes is described below.
Test Mode
Test mode is in effect while Built-In Test (BIT) is being
performed as a part of normal startup sequence. The BIT
function is entered immediately after power-on or after
software reset. BIT tests the functional areas of MMQ.
Normal Mode
Normal mode is in effect after completion of BIT. In
Normal mode the MMQ VG performs the following primary
functions:
1. Sense inertial motions, specifically, linear acceleration and
rotational rate
2. Sense internal thermal states (instrument temperatures) and
voltages
3. Convert sensed analog inputs to digital values (both inertial
and thermal inputs)
4. Digitally filter inertial inputs
5. Compensate filtered inertial inputs for thermal fluctuations
and voltage levels
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6. Initialize a system cosine rotation matrix for roll and pitch
angles using the accelerometers as level indicators
7. Convert the cosine rotation matrix into a system quaternion
8. Use the compensated rotational rates to propagate a system
quaternion
9. Use the accelerometers gravity reference to generate restoring
rates that stabilizes the system quaternion for the roll and
pitch channel
10. Extract roll and pitch angles from the stabilized quaternion
11. Prepare and deliver roll and pitch data on the serial output
channel
In Normal mode the MMQ AHRS performs the following
primary functions:
1. Provide the calculations performed in the VG component
2. Provide and interface for continual Magnetometer vector
input (via an input message)
3. Initialize a system cosine rotation matrix for roll, pitch and
heading angles using the accelerometers as a level indicator
and the magnetometers as a heading indicator
4. Use the system roll and pitch angles to level the
magnetometer vector
5. Calculate a leveled magnetic heading
6. Provide a method of calibration for the magnetometers to
compensate for hardiron and softiron effects
7. Use the magnetic heading reference to generate a restoring
rate that stabilizes the quaternion for the yaw channel
8. Extract the system roll, pitch and heading angles from the
stabilized quaternion
9. Prepare and deliver heading data on the serial output channel
IMU Operation
The IMU is designed to provide internally compensated,
body referenced, orthogonal, simultaneous measurements of
delta velocity information in three axes and delta attitude
information in three axes at up to a 400-Hz rate.
The IMU consists of three block mounted, mutually
orthogonalized Quartz Rate Sensors (QRS) in a shock-mount
configuration, and three mutually orthogonalized
Accelerometers, and associated electronics.
The electronics portion contains the interface electronics to
the inertial instruments and provides the signal processing
and computational capability required to convert the inertial
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instrument outputs to formatted inertial data. A summary of
error sources used to characterize MMQ VG and MMQ
AHRS is shown in Table 4-1.
Table 4-1. MMQ VG and MMQ AHRS IMU Error Budget
Units
Meas.
MMQ
0.25
Gyro Channel
Bias
deg/sec
1σ
Bias - In run stability (not including turn-on)
deg/h
1σ
200
SF stability (all causes)
ppm
1σ
5000
Angle Random Walk
deg/root-h
nom.
0.3
Rate Noise (noise floor, @ 15 minute)
deg/hr rms
max.
4-15
µrad rms
max.
20
∆θ Noise
Bias G Sensitivity
deg/h/g
1σ
50
deg/sec/g-rms
1σ
0.01
micro-rad/s
nom.
4.7x10-2
Angular change quantization (LSB) (1)
micro-rad
nom.
4.7x10-4
IA alignment to case stability
milli-rad
1σ
5
Data Latency
milli-sec
nom.
16
Gyro drifts due to vibration rectification
Angular rate quantization (LSB) (1)
Bandwidth, Gain (3 dB)
Hz
nom.
42
Bandwidth, Phase (-90°)
Hz
nom.
18
Bias
milli-g
1σ
17.5
Bias - In run stability, (not including turn-on)
micro-g
1σ
7.5
SF stability (all causes)
ppm
1σ
5000
Velocity random walk
milli-g/root-Hz
1σ
0.5
Acceleration Noise
milli-g rms
Max
0.5
Velocity Noise
ft/sec rms
Max.
5x10-3
Accelerometer vibration rectification
mg/grms2
Max.
1.5
Acceleration quantization (LSB) (1)
milli-g
Nom.
9.7x10-3
Velocity change quantization (LSB) (1)
mm/s
Nom.
0.95x10-3
Accelerometer Channel
IA alignment to case stability
milli-rad
1σ
5
Data Latency
milli-sec
Nom.
16
Bandwidth, Gain (3 dB)
Hz
Nom.
41
Bandwidth, Phase (-90°)
Hz
Nom.
17
Angular Rate - Dynamic Range
deg/s
Nom.
200
Angular Rate - Calibrated Range
Operating Range
deg/s
nom.
200
Acceleration - Dynamic Range
g
nom.
10 (saturates ~25g)
Acceleration - Performance Range
g
nom.
4
(1) With default data scaling/dynamic range as measured in serial output.
Note: for purposes of this user’s guide, a standard g is defined as 9.80665 m/sec2.
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Chapter 5- Hardware Integration
Overview
The MMQ VG and MMQ AHRS systems are designed to be
integrated into a navigation or flight control system by a
systems integrator. The system can be implemented in many
end-product solutions, including missiles, aircraft, guided
munitions, and other military and commercial applications;
however, it is not limited to these markets.
This chapter describes the various hardware-related features
of the MMQ VG and MMQ AHRS that should be considered
for efficient and effective system integration.
Electrical Interface
Signal Types
The characteristics defined in this section are for the MMQ
connector inputs Jl. The two types of digital signals are
defined in Table 5-1. The Jl connector contains these two
types of digital signals and power inputs (see Figure 6).
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Table 5-1. Signal Type Definitions
LVTTL:
High-level input voltage (logic 1): 2.0< VIH < 3.3 volts
Low-level input voltage (logic 0): 0< VIL < 0.8 volt
High-level output voltage (logic 1): 2.4< VOH < 3.3 volts
Low-level output voltage (logic 0): 0< VOL < 0.5 volt
Maximum input current: ±10 µAmp
Maximum rise and fall times: 50 nsec
Note: The LVTTL devices used in the MMQ-G are TTL level tolerant, and can
accept 5V inputs without damage
RS232:
High-level input voltage: 2.4 <VIH < 30.0 volts
Low-level input voltage: -30.0 < VOL < 0.8 volts
Input resistance: 3 kOhms < RIN < 7 kOhms
High-level output voltage (RL=3 kOhm): 5.0 < VOH < 15. 0 volts
Low-level output voltage (RL=3 kOhm): -15.0 < VOL < -5. 0 volts
Transition slew rate: 6.0 < TSR < 30 V/µsec
Maximum data rate: 115.2 kbits/sec
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Figure 6 MMQ (J1) Electrical Interface
“NC” denotes “no connection”. No connection is to be made to these
pins, even to an unterminated wire in a cable bundle. They are for factory
test and programming use only.
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Power Interface
Input Voltage
The input voltage to MMQ is nominally +/-12V, and should
be within +11Vdc to +13Vdc, and –11Vdc to –13Vdc, as
measured at the input, referenced to power return/ground
(“GND”).
Current
The typical steady-state current drawn by MMQ is 280mA
on the positive supply, and –80mA from the negative supply,
when used with +/-12V supplies. The typical startup current
consists of a series of surges during the first 500 msec of up
to +/-400 mA on the positive supply and 280mA on the
negative supply.
Power Supply Considerations
The primary function of any regulated power supply is to
hold the voltage in its output circuit while maintaining the
current delivery over temperature. It is quite evident that
power, current, and ripple under full load are important.
The system integrator needs to account for noise contributors
when placing a power supply in a system. Even though the
power supply required for a MMQ system is dependent on
the application, care should be taken to specify the electrical
and mechanical characteristics of the power supply.
In a system design using a switching power supply, EMI is a
natural by-product of the on-off switching. The interference
can be conducted to the load, resulting in higher output
ripple and noise. It also can be conducted back into the AC
line in the case of AC-to-DC switchers, and can be radiated
into the atmosphere and surrounding equipment. Shielding
and filter networks may be needed to reduce the ripple and
noise.
Ground
The power ground and chassis ground signals, GND, and
CHGND, are tied together inside MMQ. It is generally
recommended that they be also be tied together close to the
MMQ.
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Digital Interface
Host Vehicle (HV) Serial Interface
The HV interface is a full-duplex asynchronous RS-232
serial data communication port. This port is the interface for
command and control of the MMQ by the HV. Message
format, communications, and control protocol are defined in
Chapter 7- Software Integration.
The interface consists of the following signals with the signal
types and interface descriptions defined earlier in Table 5-1.
Both of these signals are referenced to GND.
•
RS232OUT: Data transmitted by MMQ to the
external equipment. The interface circuit for this
signal is shown in Figure 7.
Figure 7 Host Vehicle RS-232 Output Circuit
•
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RS232IN: Data received by the MMQ from
external equipment. The interface circuit for this
signal is shown in Figure 8.
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Figure 8 Host Vehicle RS232 Input Circuit
Data is transmitted and received within a UART-compatible
frame. The default frame format is:
•
One start bit.
•
8 data bits (least significant bit first).
•
One parity bit (odd parity).
•
One stop bit.
•
Data rate of 115200 baud.
The interface supports reconfiguration of data rates and
frame formats as follows:
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•
Data rates for transmit and receive are
factory set to 115200 baud.
•
The parity bit is odd parity.
•
Start and stop periods are fixed at one bit.
•
Data is fixed at 8 bits.
•
Port idle is nominally a logical low (-5
Vdc).
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Connector Types
The connector that is used to interface MMQ to the Host
Vehicle is defined in Table 5-3. Examples of mating
connectors are included in the table.
Table 5-3. MMQ-G Connector Types
Connector
Designation
J1 - I/O
Interface
Type
Example Mating Type
Samtec “EHF”
series, 34 pin, dual
row
Samtec EHF series ribbon cable connector,
Samtec P/N FFSD-17-01-N
Input/Output (I/O) Interface (J1) Connector
The I/O interface is through a 34-pin receptacle of the
Samtec EHF series.
Representatives/distributors carrying Samtec connectors may
be found at www.samtec.com.
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Cable Considerations
The choice of cable is application-dependent. There are
many cables manufactured that will meet the performance
requirements for specific applications that mate with a
variety of connectors.
The primary consideration in choosing a cable is the net
attenuation at the desired frequency. The secondary
consideration is the shielding of the cable. Other
considerations such as flexibility, jacketing, size, and cost
need to be factored into the selection process.
Cable Attenuation
The attenuation a cable exhibits at the desired frequency is
important to the system design. The materials of a cable
directly relate to the attenuation characteristics it exhibits.
The center conductor of a good quality cable is typically
copper or aluminum with a copper coating. Copper is a good
electrical conductor with relatively low DC resistance per
meter. This is important in the event a preamplifier needs to
be powered via the center conductor for extra system gain.
Cable Dielectric
The dielectric material is the key to the characteristic
impedance of a cable. RF applications generally use a cable
with a polyethylene dielectric material. Polyethylene has a
low dielectric constant that provides low capacitance and
low electrical loss. This material is also lightweight and
water-resistant. The outer conductor plays a role in the
characteristic impedance of the cable, as well as its shielding
effectiveness.
Cable Shielding
There are numerous outer conductor (shield) designs. The
outer conductor can be made of braided mesh, a solid foil, or
a solid shell. Braided shields of copper or aluminum are
ideal for minimizing low frequency interference and
exhibiting a low DC resistance. This type of shield provides
good structural integrity and flexibility. As a rule, higher
braid coverage yields a more effective shield.
Foil shields are made of aluminum and are laminated to a
polypropylene film to provide mechanical strength to the
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foil. The DC resistance of a foil shield is not as low as a
braided shield, but the foil shield provides 100 percent
coverage of the center conductor. This shield is more cost
effective, but has less structural integrity than a braided
shield. Solid shields afford the best performance, but are
inflexible and expensive.
Shields can be arranged in many different combinations.
Combination shields consist of more than one layer of
shielding. Typical combinations can include a braid or a
braid with foil. A braid-type shield significantly lowers the
DC resistance of the overall shield, while a braid-foil type
shield provides the low DC resistance and structural strength
of the braid plus 100 percent shielding of the foil.
The outside jacketing of a cable does not provide any
EMI/RFI shielding to a cable. The jacket provides resistance
to weather deterioration, mechanical abuse, and heat.
For most MMQ applications where the cable runs are
relatively short, a cable can be selected with any of the
characteristics previously described. If an application
requires extensive lengths of cable (> 30 ft) other types of
cable commonly larger in diameter with solid copper outer
conductors should be considered. These types of cables
exhibit very low attenuation and excellent shielding, but tend
to be larger, costing more per linear meter.
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Chapter 6- Magnetometer
Interface
Overview
The MMQ AHRS requires integration with an external
magnetometer. Body-axis three dimensional magnetic
vector data is input into the MMQ AHRS via a proprietary
Systron Donner Inertial message format. In both instances
the data is sent into the MMQ AHRS via the RS-232 UART
interface. Since the messages are coming in through the
MMQ AHRS RS-232 interface, the receiving BAUD rate
will be the same as for any input message, and is set when
the choice is made to configure the BAUD rate on the MMQ
AHRS RS-232 port (Please see Chapter 7- Software
Integration). The body-axis magnetic data is transformed
inside the MMQ AHRS into heading reference data, which is
then used by the AHRS algorithm to stabilize heading. Note
that the MMQ AHRS system heading is referenced magnetic
north.
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Magnetic Measurement
Three axes magnetometer systems use a set of sensitive
magnetometers to measure the Earth's three-dimensional
magnetic field vector. This vector data can be used to
calculate magnetic heading. Because the earth’s field is very
weak, small amounts of moving magnetic material near the
magnetometer can have large effects on a magnetic heading
calculation. The magnetometer should be isolated from
magnetic material as much as possible. Magnetic material
will distort the magnetic field near the sensing elements,
which can then affect the accuracy of a heading calculation.
A magnet can be used to test materials that will be near the
magnetometer, such as iron, carbon steel, some stainless
steels, nickel and cobalt. Essentially any material that will
stick to a magnet should be avoided. The MMQ AHRS
contains magnetic disturbance compensation algorithms
designed to correct for the effect of these disturbance
magnetic fields as long as the disturbance is stationary.
Materials that will not affect the magnetometer
measurements include aluminum, brass, plastic, titanium,
wood, and some high-quality stainless steels. Again, if in
doubt, try to stick a magnet on the material. If the magnet
doesn't stick then the material will not affect the
magnetometer. Stationary magnetic objects will be
compensated for by the compensation algorithms. Moving
ferrous objects within 24 inches cannot be fully compensated
by the algorithm, so the magnetometer should not be located
within 24 inches of any large moving ferrous metal objects
such as landing gear components, electric motors, control
linkages, etc. Ferrous metal objects that may change
position during flight operations, such as landing gear, flap
actuators, and control linkages should not be within 24
inches of the magnetometer. The magnetometer should not
be located close to high current DC power cables or 400
cycle AC power cables and their associated magnetic fields.
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Hardiron/Softiron Calibration
Magnetometer magnetic heading reference data will need to
be calibrated for hard and soft iron compensation before use
in any final installation. The MMQ AHRS uses the
magnetometer heading magnetic vector data to compute
heading. Ideally, the magnetic sensors would be measuring
only earth's magnetic field to compute the heading angle. In
the real world, however, residual magnetism in your system
will add to the magnetic field measured by the
magnetometer.
Static magnetic disturbance behaves as a bias offset error in
the magnetometer measurement if it is not compensated.
This magnetic field bias offset is called hard iron magnetic
error. In addition, magnetic material can change the
direction of the magnetic field as a function of the input
magnetic field. This dependence of the local magnetic field
on input direction acts as a scale factor error on the
magnetometer data, and is referred to as soft iron.
The MMQ AHRS can measure any disturbance constant
magnetic field that is associated with the MMQ AHRS itself,
or the user system, and corrects for it during the calibration
procedure. The MMQ AHRS also makes a correction for
some soft iron effects. The process of measuring these nonideal effects and correcting for them is called hard iron and
soft iron calibration. Calibration corrects for magnetic fields
that are fixed with respect to the user system. It cannot
compensate for time varying fields, or fields created by parts
that move with respect to the magnetometer.
The MMQ AHRS accounts for the extra magnetic fields by
making a series of measurements from the magnetic heading
reference data. The MMQ AHRS uses these measurements
to model the hard iron and soft iron environment in the
installation.
The magnetometer calibration mode should only be
performed once the MMQ AHRS system is in Normal Mode.
The hard and soft iron calibration procedure control is
performed using the commands defined in Chapter 7Software Integration. The process is monitored using the
system status word in the output message, and the status of
the magnetometer calibration data present in non-volatile
memory is observed using the revolving word in the output
message.
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Send the appropriate “Magnetometer Calibration Control
Command” to turn on the calibration process. Once the
MMQ AHRS has received the calibration on command, the
system status word will display the proper “Magnetometer
Calibration” bit signifying that the MMQ AHRS is in
magnetometer calibration mode. The user system will then
need to be rotated through at least three complete circles. At
this point, the MMQ AHRS should have collected enough
data for a good magnetometer compensation calibration.
Send the appropriate control message to turn off the
calibration process. Once the MMQ AHRS has received the
calibration off command the status word will display the
proper bits signifying that the MMQ AHRS is no longer in
magnetometer calibration mode. The MMQ AHRS will now
store these as calibration constants in the EEPROM for use
upon subsequent power cycles. Note that the process of
storing this data in the EEPROM is the same as storing the
system information into the EEPROM, as described in
Chapter 7- Software Integration, and there will be an
interruption of data communications of approximately 2
seconds. The revolving byte word will now display the
proper bits signifying that the magnetometer calibration has
been stored properly.
Once the calibration process is complete, the MMQ AHRS
can be restarted through a power cycle to re-initialize the
system angles. Once the MMQ AHRS has entered Normal
mode and is receiving proper magnetometer heading
reference data, the magnetometer calibration can be then be
tested by comparing the system heading output of the MMQ
AHRS with a known reference (compass or compass
markers). Position the user system at each of the cardinal
headings (0 degrees (north), 90 degrees (east), 180 degrees
(south) and -90 degrees (west). At each cardinal position,
allow the MMQ AHRS at least 2 minutes to properly
stabilize, and then observe the system heading parameter. It
should be within +/- 2 degrees of the cardinal heading. If
there is still some residual magnetic disturbance (as observed
by a system heading error of more than +/- 2 degrees), then
the magnetometer calibration can be performed again. All
subsequent magnetometer calibrations build on the previous
calibration by using the previously magnetometer calibration
coefficients throughout the calibration process. It is this way
that a “fine tuning” of the magnetometer calibration can be
achieved. If the user desires to start over, or if a major
configuration change to the installation is performed, such as
moving the installation of the magnetometer or locating a
new large magnetic ferrous disturbance near to the
magnetometer, then the calibration coefficients can be erased
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from the MMQ AHRS by sending the proper erase
magnetometer calibration data command and restarting the
MMQ AHRS system.
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Magnetometer Data Interface
The MMQ AHRS supports direct communications with an
external magnetometer and will accept input magnetometer
data via a Systron Donner proprietary format message.
Please refer to Chapter 7- Software Integration for a
complete description of this input message. The MMQ
AHRS also outputs Magnetometer data in the revolving byte
word which contains information directly related to the input
magnetometer data. These outputs are designed to provide
the user enough direct information about the magnetometer
input data. Please refer to the description in Chapter 7Software Integration for a complete description of the
magnetometer data in the revolving byte.
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Chapter 7- Software Integration
MMQ VG and MMQ AHRS to Host Vehicle Data
Interface/Definitions
The MMQ VG and MMQ AHRS provide a bi-directional
RS-232 serial port to support serial interface between the
MMQ and the Host Vehicle (HV). This allows the user to
receive the output message describing the MMQ status and
attitude state, send input messages to the MMQ to initialize
it, and change its processing state.
The HV Input/Output (I/O) consists of various data input
messages and one main output message that are identified by
data message numbers. The detailed content and structure
(definitions) of these data blocks will be specified in this
chapter.
The data transmit rate and message output rate are currently
both factory set at 115200 baud and 100 Hz. Refer to the
control commands in this chapter for information on
selecting/reprogramming the MMQ baud rate and output
message rate.
Serial Interface Functionality
MMQ Normal Mode Serial Input Descriptions
Input messages are received in normal mode only. The input
messages are input through the same RS-232 UART that the
output data comes out over. The structure of all input
messages is:
MSG_ID word
0 to 4 words of data (each word is 2 bytes or 16 bits of data)
Checksum of the MSG_ID and all data words
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Reset Message
Flashes any changes to message rate or baud rate to Flash
Sector B and then resets the DSP software. The Message ID
= 0x5A51, and there is no data word.
Set Normal Mode Output Message Rate Message
The allowable normal mode output message rates are:
400 Hz (Data Word 0 Value=1)
200 Hz (Data Word 0 Value=2)
100 Hz (Data Word 0 Value=4)
50 Hz (Data Word 0 Value=8)
The message is made up of the Message ID = 0x5A52, one
Data Word 0 (16 Bits) = 1,2,4,8, and a checksum.
Set Input/Output Baud Rate Message
The allowable RS-232 Baud rate values are:
115.2 KBaud (Data Word 0 Value=1)
57.6 KBaud (Data Word 0 Value=2)
38.4 KBaud (Data Word 0 Value=4)
19.2 KBaud (Data Word 0 Value=8)
The message is made up of the Message ID = 0x5A53, one
Data Word 0 (16 Bits) = 1,2,4,8, and a checksum.
Magnetometer Input Data Message
For proper MMQ-AHRS operation, 3-axis magnetometer
data from a remote magnetometer is required. The
magnetometer data is transferred into the format of the
Magnetometer Input Data Message, and is required at a
minimum of 1 Hz for proper operation. The nominal input
rate tested is 10Hz. The remote magnetometer and the
MMQ-AHRS must be mounted co-aligned in axes, and
together they define the system that allows the MMQ-AHRS
to work as a heading indicator. The message contains data
from the remote magnetometer measuring the earth’s
magnetic field and contains magnetometer data for the X
(MagX), Y (MagY) and Z (MagZ) axes of the system. The
magnetometer data is scaled such that 1 bit = 13 nanoTesla.
When converted then a magnetometer integer value of 32767
= +4.26 Gauss, and an integer value of -32768 = -4.26
Gauss. The message is made up of the following:
Message ID = 0x5A54
Data Word 0 (Signed 16 Bit Integer) = MagX (counts from
Magnetometer X)
Data Word 1 (Signed 16 Bit Integer) = MagY (counts from
Magnetometer Y)
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Data Word 2 (Signed 16 Bit Integer) = MagZ (counts from
Magnetometer Z)
Checksum
Start Magnetometer Calibration
This message starts the MMQ-AHRS internal magnetometer
hardiron/softiron compensation process. It is made up of a
Message ID = 0x5A56 and no data word.
Stop Magnetometer Calibration
This message stops the MMQ-AHRS internal magnetometer
hardiron/softiron compensation process. It is made up of a
Message ID = 0x5A57, no data word. Once this message is
received, the resultant hardiron and softiron calibration
parameters are flashed into the EEPROM for permanent
recall. Upon the next power up of the MMQ-AHRS, the
stored hardiron and softiron data will be applied to the
leveled magnetometer vector.
Erase Magnetometer Calibration
This message erases all stored MMQ-AHRS internal
magnetometer hardiron/softiron compensation data from
system memory and the Flash EEPROM. It is made up of a
Message ID = 0x5A58, no data word.
MMQ Normal Mode Serial Output Descriptions
Normal Mode Data Message
The MMQ Normal Mode Message has 14 words. The
message rate is user-selectable at 400, 200, 100, 50 Hz (See
Serial Inputs Description Chapter). MMQ-VG and MMQAHRS have the same normal mode output message
definition. For the MMQ-VG, Roll and Pitch are valid, but
Yaw angle output data is always 0.0. For the MMQ-AHRS,
all three Roll, Pitch and Yaw angle output data is valid.
The message contains a header word followed by the data
words, and a checksum at the end of the message. Serial
data is byte wise with one start and one stop bit per byte, no
parity. Serial data output messages are all even word length,
a word being considered to be 16 bits. Transmission is sent
Low-byte, High Byte with Least Significant bit first in each
case. The 16-bit checksum at the end of the message is the
sum of the previous 13 16-bit words in the message,
including the header.
The normal mode message is defined in Table 7-1.
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Index
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Bit
Position
Value
Bit
Position
Value
Table 7-1. MMQ Normal Mode Message
Name
Comments
Header
0x7FFF
CompAccelX
Compensated data , signed 16-bit word, 3200 counts per g
CompGyroX
Compensated data , signed 16-bit word, 100 counts per deg/sec
CompAccelY
Compensated data , signed 16-bit word, 3200 counts per g
CompGyroY
Compensated data , signed 16-bit word, 100 counts per deg/sec
CompAccelZ
Compensated data , signed 16-bit word, 3200 counts per g
CompGyroZ
Compensated data , signed 16-bit word, 100 counts per deg/sec
BIT
See below for details
Frame Counter
Counts message packets sequentially from 0 to 65535
Revolving Parameter
See below for details
Phi/Roll
Signed 16-bit word, 90 counts / degree, VG/AHRS model only
Theta/Pitch
Signed 16-bit word, 90 counts / degree, VG/AHRS model only
Psi/Yaw
Signed 16-bit word, 90 counts / degree, AHRS model only
Checksum
Sum of the previous 13 16-bit words in the message with header
Table 7-2. Normal Mode Data Message BIT Word Definition
0x8000
0x4000
0x2000 0x1000
0x800
0x400
0x200
Watchdog
timer fired
Code
checksum
failed
0x80
Note 1.
0x100
0x40
GyroZ
output
over
range
0x20
AccelZ
output
over
range
0x10
GyroY
output
over
range
0x8
AccelY
output
over
range
0x4
GyroX
output
over
range
0x2
AccelX
output
over
range
0x1
Voltage
Sensor ID
bit2
Voltage
Sensor
ID bit1
Voltage
Sensor
ID bit0
Temp
Sensor
ID bit3
Temp
Sensor
ID bit2
Temp
Sensor
ID bit1
Temp
Sensor
ID bit0
Note 1: Not used in VG mode. For AHRS mode, this bit
displays Magnetometer Timeout. This bit will display a “1”
when there is no magnetometer data for more that 1 second.
The Voltage Sensor ID and Temp Sensor ID fields are
defined in the following tables:
Table 7-3. Normal Mode Data Message BIT Word Definition
Value
Meaning
0
All pass
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1
5V failed
2
3.3V failed
3
4
5
6
1.9V failed
+12V failed
-12V failed
1.25V failed
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Table 7-3. Normal Mode Message BIT Word Temp Sensor ID
Value
Meaning
0
All pass
1
AccelX failed
2
GyroX failed
3
AccelY failed
4
GyroY failed
5
AccelZ failed
6
GyroZ failed
7
ADC temp failed
8
DSP temp failed
The revolving parameter is defined in Table 7-4 below. For
the data represented by the revolving parameter, all voltages
and temperatures are signed 16 bit integer values such that a
value of 1 represents 3.90625 mV or mDeg. The range of
the data then is -128.0 (0x8000) to +127.996 (0x7FFF), and
0x0000 = 0.0 volts or degree. Thus a value of 256 would
represent 1 volt or 1 degree C respectively. Also all
magnetometer data is signed 16 bit data and scaled such a
value of 10000 represents 1 gauss, and a value of 1
represents 0.0001 gauss.
Table 7-4. Normal Mode Message Revolving Parameter
Low 6 bits of Frame Counter Revolving Parameter Index
0
AccelX Temperature
1
GyroX Temperature
2
AccelY Temperature
3
GyroY Temperature
4
AccelZ Temperature
5
GyroZ Temperature
6
ADC Temperature
7
DSP Temperature
8
5.0 volt PS
9
3.3 volt PS
10
1.8 volt PS
11
+12 volt PS
12
-12 volt PS
13
1.25 volt PS
14
Message rate in Hz.
15
Baud rate in KHz
16
Magnetometer Calibration Data Present
17
Magnetometer Hard Iron XAXIS
18
Magnetometer Hard Iron YAXIS
19
Magnetometer Hard Iron ZAXIS
20
Magnetometer Soft Iron XAXIS
21
Magnetometer Soft Iron YAXIS
22
Magnetometer Soft Iron ZAXIS
23
Leveled Magnetometer XAXIS
24
Leveled Magnetometer YAXIS
25
Leveled Magnetometer ZAXIS
26
Uncompensated Raw Filtered Accelerometer X
27
Uncompensated Raw Filtered Gyro X
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28
29
30
31
32
33-64
Uncompensated Raw Filtered Accelerometer Y
Uncompensated Raw Filtered Gyro Y
Uncompensated Raw Filtered Accelerometer Z
Uncompensated Raw Filtered Gyro Z
Magnetometer Data Packets Received in Last 10 sec
Not Defined
Note that all magnetometer data (leveled magnetometer
output and Magnetometer calibration parameters) is output
only for the MMQ-AHRS model. The Leveled
Magnetometer data output only changes when there is a new
input Remote Magnetometer data input, otherwise it will
output the same most recent Magnetometer vector values.
The Leveled Magnetometer data is the input Remote
Magnetometer Data Vector rotated into the navigation frame
and compensated for hardiron and softiron data if present.
The Baud Rate parameter is defined in Table 7-5 below.
Table 7-5. Normal Mode Message Revolving Parameter Baud Rate Value Definition
Baud Rate Value
Meaning
115
115.2 KBaud
57
57.6 KBaud
28
28.8 Kbaud
14
14.4 KBaud
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Chapter 8- End Product
Applications
Overview
The MMQ VG and MMQ AHRS can be used for a variety of
applications. Use of the various system features and
interfaces varies widely from customer to customer. The
information presented here is designed to guide the first-time
user on what might be required for his/her specific
application. Regardless of the application, power must be
supplied to the MMQ unit. All users will need to
communicate with the system’s asynchronous RS-232 serial
interface. This interface provides attitude solution and
sensor data to the user, and accepts initialization and control
data from the user.
Product Application Examples
The MMQ VG and MMQ AHRS can be implemented in
many end-product solutions. Some examples of MMQ VG
and MMQ AHRS use and applications are described below.
Use: Attitude Determination System
•
Applications: Manned or remote
controlled dynamic platforms.
•
Examples: Airplanes, Helicopters,
remote controlled Unmanned Aerial
Vehicles (UAVs), Mobile Land
Vehicles, and Mobile Marine
Vehicles.
Use: Guidance, Navigation, and Control
•
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Applications: Unmanned Vehicles.
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•
Examples: Autonomous UAVs,
Missiles, Targets, Drones, Guided
Munitions.
Use: Pointing
•
Applications: Camera and other
pointing applications.
•
Examples: Aerial Photomapping,
Radar Pointing/Steering, Land/Sea
Launched Weapon Platforms.
Since MMQ can be integrated into a wide range of endproduct solutions, each unique system requires different
inputs and outputs to satisfy the application. The system
integrator should help the development team determine how
to use MMQ features and software data sets within the
specific product or application.
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Appendix A- Frequently Asked
Questions
I apply power to the unit and the unit doesn’t run. What
can I do?
Inspect the power supply and cabling to the unit. Verify the
proper voltage level at the power supply and at the unit
connector pins.
•
The DC power supply that you are using
may not have an adequate current capacity
for the unit. Although the unit draws
+280mA/-80mA steady state current, turnon inrush current can be as high as +/400mA during the first half second. It’s a
good idea to use a power supply rated at
least 1 amp for each supply.
I can’t communicate with the unit via the RS-232 port.
Why?
Generally, if you are having trouble communicating with the
unit and are sure that your RS-232 communications
parameters are set correctly; try viewing the data using an
RS-232 monitor program. This will verify the
communications parameters, as well as the message data
content, handshaking, and timing. Remember that the data
on the RS-232 port is binary, not ASCII coded numbers. See
Chapter 7- Software Integration for data formats. Also,
verify the following:
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•
Check that the serial data connections are
complete in the cable that you are using.
(Can you see data on an oscilloscope or
via an RS-232 monitor program right at
the data pins on the unit connector?)
•
Verify that a null modem cable
configuration is being used (i.e., is your
system’s Transmit data line going to the
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unit’s receive data line and your system’s
Receive data line going to the unit’s
transmit data line).
•
Check that the proper baud rate, data bits,
stop bits, and parity are being used. You
should be using the proper baud rate, eight
data bits, one stop bit, and odd parity.
•
Verify that you have set up your UART
correctly. On a PC, the UART’s OUT 2
signal must be asserted for the UART to
function properly.
•
If your program is interrupt-driven, verify
that the interrupt handling routine
functions correctly using a dumb terminal
or simulated message input.
Why am I getting unintelligible data over the RS-232 port?
The RS-232 data is sending byte information in reverse order
from the unit. (At your PC, observe the message traffic, or at
your printer, if you are using one, get a sample printout.) If
you’re using a PC to receive data, you must be sure to place
the data in memory in the correct order for your program to
interpret the data.
•
Verify that poor cable connections are not
causing RS-232 signal degradation. If the
received data bytes have parity, break, or
framing errors, then you are either using
the wrong communications parameters, or
there is a problem with the cabling.
My program can’t detect the start of a new message
block, but there appears to be data being sent by the unit.
Why?
The message start identification word “7FFF” is sent LSB
first, so a program should check that an “FF” is received,
then that an “7F” is received to indicate the start of an
incoming message.
I can receive data from the unit, but I can’t send data to
the unit. What should I do?
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•
Verify that the unit transmit cable
connection is complete to your processor.
•
Verify that the message format for the
data that you are sending the unit is
proper. (Are the checksums for the header
and data portions of the message correct?)
If the handshake protocol indicates that
your message has been rejected, chances
are that your message format is in error.
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Appendix B- Getting Started
Setup
The following information will guide the system integrator
in effectively integrating the MMQ VG or MMQ AHRS
system with the HV. For commonly asked questions
regarding system integration, refer to Appendix AFrequently Asked Questions. For questions concerning your
specific application, please contact an SDI applications
engineer.
Support Equipment Required
Power Supply
MMQ requires a power input of +/-12V (nominal, 11v-13V
limit) as measured at the input. The typical steady-state
current drawn by MMQ is +280ma and –80mA at +/-12 Vdc.
Turn-on (inrush) current during the first half second can be
as high as +/-400mA on the positive supply and 280mA on
the negative supply, It’s a good idea to use a power supply
rated at least 1 amp for each supply.
Connectors/Cables
The J1 I/O connector and cable requirements are defined in
Chapter 5- Hardware Integration. If used in a hostile
electromagnetic environment, care should be given to
overbraid the interface cable to obtain the best overall EMI
protection.
Communication Via RS-232 Asynchronous Port
As part of getting started, a Windows compatible computer
equipped with a RS-232 COM port supporting up to
115.2kBd can be used as the Host Vehicle system. The host
vehicle I/O interface will enable the user to send
initialization and control data to the MMQ, as well as display
or record its output information. Refer to the Digital
Interface section in Chapter 5- Hardware Integration for
information on the data rates and frame format selection of
the serial data.
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Additional Support for Integration
PC-based integration software, SYSTRON DONNER
VIEWER is available with MMQ VG and MMQ AHRS.
This software will aid the user in communication through the
host vehicle port. The software serves only as a guide in
helping the user get started using MMQ and to observe the
contents of the normal mode data message. However, it is
the responsibility of the user to develop software to meet his
specific application.
Installation
It is recommended that MMQ be mounted using four #6
socket cap screws, tightened to a torque between 8-12 in-lbs.
The mounting hole pattern is shown in Figure 4.
Using MMQ
This section is intended as an operational overview of
the MMQ VG and MMQ AHRS. Examples are provided
using the SYSTRON DONNER VIEWER software, running
on a standard Windows compatible computer. The following
section will provide information necessary to help the user
set up their system to properly interface the MMQ.
MMQ-G Operational Overview
Once power is applied, the MMQ VG and MMQ AHRS will
go through power-on initialization, and will sequence up to
Normal mode. This entire process takes approximately 7
seconds to complete.
Before You Begin
Warning
Improper wiring of the user cable connecting to MMQ can cause irreversible damage
that is not covered under product warranty. Common mistakes include incorrectly
identifying pin assignments (e.g., mirror image wiring assignments), resulting in power being
applied to the wrong pins.
Before applying power, verify that it is being supplied to the correct
pins; see table below and Detail “A” (outside view of MMQ connector
J1).
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Signal
Pin
+12 Vdc
22
-12 Vdc
12
Antenna DC Power (optional)
31
+3v “keep alive” power (optional)
32
Power Return (Ground)
29
Chassis (internally connected to Ground)
30
1. The cable’s RF noise environment and shielding requirements
should be taken into consideration prior to fabrication.
2. Verify cable configuration of RS-232 port is correct. Your
system’s transmit data line should go to the MMQ receive line and
your system’s receive line should go to the MMQ transmit line. (i.e.
null modem connection)
For reference, Table A-1 provides the standard pin assignments for
the relevant RS-232 signals typically found on a compatible
computer with COM port. The MMQ requires only use of the
Transmit and Receive data signals (TD, RD) and Signal
Ground.
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Table A-1. RS-232 Pin Assignments
Computer Pin #
Computer Pin #
Description
(25-Pin)
(9-Pin)
Abbreviation
Transmit Data
2
3
TD
Receive Data
3
2
RD
Signal Ground
7
5
SG
Protective Ground
1
-
FG
3. Verify that the cable configuration of +/-12 Vdc main power and
+3 Vdc battery input (optional) are correct.
4. Insert the available SYSTRON DONNER VIEWER CD in the
CD drive, and install SYSTRON DONNER VIEWER on your
computer. The SYSTRON DONNER VIEWER software will
provide the ability to interface between MMQ and a Windows-based
PC simulating the user's host vehicle communication device. Refer
to Appendix C for the details of the installation.
5. Create a short cut on screen for easy access. Double click on the
SYSTRON DONNER VIEWER shortcut, the SYSTRON DONNER
VIEWER command and control window should appear on the
screen.
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