Inertial Navigation System INS-B, INS-P, INS

Inertial Navigation System INS-B, INS-P, INS
INS
Interface Control Document
Inertial Navigation System
INS-B, INS-P, INS-D
Interface Control Document
Revision 2.5
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
Interface Control Document
CHANGE STATUS LOG
DOCUMENT: Inertial LabsTM INS Interface Control Document
AFFECTED
REVISION
DATE
REMARKS
PARAGRAPHS
1.0
Jul. 14, 2015
All
Released version.
1.1
Jul. 17, 2015
6.2
Minor changes.
1.2
Sep.03, 2015
6, 6.8
1. Implemented auto start option with choice
of desirable variant of output data format after
device power on. Since INS firmware version
1.0.2.0.
6.2
2. Corrected mistake in tables: ms_pos is
replaced by ms_gps
6.2.5
3. Updated description of the «INS NMEA
Output» data format (timestamp is added).
6.3.2
4. Renamed command DataOnRequest to
SetOnRequestMode to exclude misunderstanding of this command action.
1.3
Nov.02, 2015
5
1. Added diagrams Fig.5.4, Fig.5.5 of electric
connection of INS with two and three COM
ports.
5
2. Changed connector pinout to include two
more COM ports, Table 5.1.
6.2.6
3. Added new ”INS Sensors NMEA Output”
data format.
6.3.1
4. Updated “Table 6.18. INS maximum data
rate at different output data formats”.
6.10
5. Added section “6.10. Post processing of
the INS data”.
6.4
6. Added sections “6.4.1. GNSS receiver
parameters” and “6.4.2. Control of GNSS
receiver model”.
1.4
Dec. 01, 2015
5
Added color of wires in cable with mating
connector in Table 5.1.
1.5
Feb.02, 2016
6.2.1, 6.2.2,
1. Corrected values of maximum data rate for
6.2.4, 6.2.6
different data formats.
6.4.1
2. Added description of new
GNSS_com2_bps parameter.
5
3. Added description of PPS in section “5.2.
PPS description”.
1.6
Feb.18, 2016
For INS with firmware version since 2.1.2.0:
6.2.1
1. Corrected INS message payload at the
“INS OPVT” data format in the Table 6.4.
6.2.2
2. Implemented new “INS QPVT” output data
format.
6
3. Byte #3 in the INS output data is used for
identification of command which the INS
answers on (see Table 6.2).
1.7
Apr.21, 2016
1
1. Added section “1.3. True and magnetic
heading”.
5
2. Added description of 19 pin connector of
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
Interface Control Document
5
6.2.3
6.3.1
6.3.2
6
APPENDIX D
1.8
Jul.29, 2016
5.3
5.4
6.2.1, 6.2.2,
6.2.3, 6.2.5
6.2.1
6.4.1
6.10.1
6.11
6
2.0
Aug.09, 2016
1.1
1.4, 1.5
4.3
5
5
6.2, 6.3,
APPENDIX C
TM
the INS with RS-422 interface.
3. Added section “5.2. Connection of the
Inertial LabsTM INS with RS-422 interface to
the host computer for tests”.
4. Added magnetic declination field to “INS
Full Output Data” format instead of reserved
field (see Table 6.10) – since firmware
version 2.2.0.2.
5. Changed byte structure of the block of
initial alignment data – added Table 6.20.
6. INS_SensorsData command is not
supported in the “On Request” operating
mode since INS firmware version 2.1.1.0.
7. Added sections “6.11. Change of the main
COM port baud rate” and “6.12. Limitation of
the INS maximum output data rate”.
8. Added APPENDIX D. Forms of the Inertial
LabsTM INS orientation presentation.
For INS with firmware version since 2.2.1.0:
1. Changed section “5.3. PPS description”.
2. Added section “5.4. GPIO description”.
3. Changed GNSS information in output data
formats INS OPVT; INS QPVT; INS Full
Output Data; INS Minimal Data. See notes in
these sections.
4. Changed GNSS information in Table 6.5,
Table 6.6.
5. Added new parameters to section “6.4.1.
GNSS receiver parameters” including PPS
control and input marks control.
6. Added section “6.10.1. Raw GNSS receiver
data”.
7. Added section “6.11. Synchronization of
the INS data with LiDAR and other devices”.
8. COM3 has two functions: to receive data
for GNSS differential corrections or to output
$GPRMC messages
1. Presented new line of Inertial Labs INS:
INS-B, INS-P, INS-D.
2. Added sections “1.4. Ground track angle vs
heading” and “1.5. Using GNSS heading in
INS-D”.
3. Added section “4.3 Installation of two
GNSS antennas for INS-D operation”.
4. Shown connectors position on back side of
INS-B, INS-P, INS-D units (Fig.5.1, Fig.5.2).
5. Added electrical specifications for INS-B,
INS-P, INS-D units (Table 5.3).
6. Added two output data formats – OPVT2A,
OPVT2Ahr and appropriate commands
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
Interface Control Document
6.5
2.1
Sep.05, 2016
6.2
6.9
2.2
Sep.16, 2016
2.3
Oct.02, 2016
6.2, 6.3,
APPENDIX C
6.2
6.3.6
2.4
Dec.06, 2016
6.2.12
6.2.13
6.4.1
6.7.5,
APPENDIX A,
APPENDIX C
6.9
2.5
Jan.06, 2017
6.7.12,
APPENDIX A,
APPENDIX C
6.9
TM
INS_OPVT2Adata, INS_OPVT2Ahrdata.
7. Heave calculation is supported in INS-D
but not in INS-B and INS-P units.
1. Added ±450°/s gyro range for KG values
(see notes to Tables 6.4, 6.7, 6.8).
2. Added indication of GNSS receiver failure
in the Unit Status Word (since INS firmware
version 2.5.0.2).
Added output data format – OPVT2AW, and
appropriate command
1. Corrected KA scale factor for ±8g
accelerometer range and scale factor for
supply voltage (see Tables 6.4, 6.7, 6.8, 6.9,
6.10 and notes to them).
2. Added type of pressure sensor in INS
devices information Table 6.25.
1. Added GNSS receiver NMEA data set.
2. Changed GPRMC format description.
3. Added new parameters COM2_data,
NMEA_set.
4. Added description of VG3D calibration,
and appropriate command StartVG3DClb.
5. Changed description of the bits #7, 15 of
USW
1. Added description of on-the- fly VG3D
calibration, and appropriate commands
StartVG3Dclb_flight, StopVG3Dclb_flight.
2. Bits #7, 15 of USW are used for indication
of stages of on-the- fly VG3D calibration.
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
Interface Control Document
TABLE OF CONTENTS
1. Introduction ..................................................................................................................... 7
1.1. Description of the System ........................................................................................ 7
1.2. Principles of the Inertial LabsTM INS Operation ...................................................... 10
1.3. True and magnetic heading.................................................................................... 12
1.4. Ground track angle vs heading .............................................................................. 13
1.5. Using GNSS heading in INS-D............................................................................... 13
2. Scope and applicability.................................................................................................. 14
3. Specifications ................................................................................................................ 14
4. Mechanical interface ..................................................................................................... 14
4.1. Mechanically mounting the Inertial LabsTM INS ...................................................... 15
4.2. Installation of single GNSS antenna....................................................................... 16
4.3. Installation of two GNSS antennas for INS-D operation ......................................... 17
4.4. Where to install the Inertial LabsTM INS and its antenna for tests........................... 18
4.5. Where to install the Inertial LabsTM INS on the object ............................................ 19
5. Electrical Interface ......................................................................................................... 21
5.1. Connection of the Inertial LabsTM INS with RS-232 interface to the host computer
for tests ......................................................................................................................... 24
5.2. Connection of the Inertial LabsTM INS with RS-422 interface to the host computer
for tests ......................................................................................................................... 30
5.3. PPS description...................................................................................................... 33
5.4. GPIO description .................................................................................................... 34
6. Software interface ......................................................................................................... 35
6.1. Operational modes of the Inertial LabsTM INS ........................................................ 37
6.2. Output Data Formats of the Inertial LabsTM INS in the Operating Modes ............... 37
6.2.1. The “INS OPVT” (Orientation, Position, Velocity, Time) data format ............... 38
6.2.2. The “INS QPVT” (Quaternion of orientation, Position, Velocity, Time) data
format ........................................................................................................................ 41
6.2.3. The “INS OPVT2A” (Orientation, Position, Velocity, Time, Dual-antenna
receiver data) format ................................................................................................. 44
6.2.4. The “INS OPVT2AW” (Orientation, Position, Velocity, Time, Dual-antenna
receiver data, GPS Week) format ............................................................................. 46
6.2.5. The “INS OPVT2Ahr” (Orientation, Position, Velocity, Time, Dual-antenna
receiver data, with high resolution) format ................................................................ 49
6.2.6. The “INS Full Output Data” format .................................................................. 51
6.2.7. The “INS Sensors Data” format....................................................................... 53
6.2.8. The “INS Minimal Data” format ....................................................................... 57
6.2.9. The “INS NMEA Output” data format .............................................................. 58
6.2.10. The “INS Sensors NMEA Output” data format .............................................. 59
6.2.11. The “TSS1 Output” data format..................................................................... 60
6.2.12. The GNSS receiver NMEA data format (through COM2 port)....................... 61
6.2.13. The GNSS receiver GPRMC data format (through COM3 port).................... 65
6.3. Control of the Inertial LabsTM INS ........................................................................... 66
6.3.1. INS_OPVTdata, INS_QPVTdata, INS_OPVT2Adata, INS_OPVT2AWdata,
INS_OPVT2Ahrdata, INS_FullData, INS_SensorsData, INS_minData, INS_NMEA,
INS_Sensors_NMEA, INS_TSS1 commands ........................................................... 66
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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6.3.2. SetOnRequestMode command – getting INS data on request (on demand) .. 69
6.3.3. Stop command ................................................................................................ 70
6.3.4. LoadINSpar command .................................................................................... 70
6.3.5. ReadINSpar command.................................................................................... 72
6.3.6. GetDevInfo command ..................................................................................... 73
6.3.7. GetBIT command ............................................................................................ 74
6.4. Control of the GNSS receiver ................................................................................. 75
6.4.1. GNSS receiver parameters ............................................................................. 75
6.4.2. Control of GNSS receiver model ..................................................................... 80
6.5. Altitude and Heave calculation ............................................................................... 81
6.5.1. Adjustment of the algorithm of heave calculation in INS-D ............................. 82
6.5.2. Heave calculation for chosen point of the carrier object .................................. 83
6.6. Acceleration compensation at object swaying ........................................................ 83
6.7. Calibration of the Inertial LabsTM INS on hard and soft iron ................................... 84
6.7.1. Start3DClb command for INS 3D calibration ................................................... 84
6.7.2. Stop lbRun command .................................................................................... 87
6.7.3. AcceptClb command ....................................................................................... 87
6.7.4. ExitClb command ............................................................................................ 87
6.7.5. StartVG3DClb command for INS VG3D calibration ........................................ 88
6.7.6. Start2D2TClb command for INS 2D-2T calibration ......................................... 89
6.7.7. StartClbRun command .................................................................................... 92
6.7.8. FinishClb command for INS 2D-2T calibration ................................................ 93
6.7.9. Start2DClb command for INS 2D calibration ................................................... 93
6.7.10. ClearClb command ....................................................................................... 94
6.7.11. GetClbRes command .................................................................................... 95
6.7.12. StartVG3Dclb_flight and StopVG3Dclb_flight commands for start and finish
INS on-the-fly VG3D calibration ................................................................................ 96
6.8. INS automatic start................................................................................................. 98
6.9. The Unit Status Word definition............................................................................ 100
6.10. Post-processing of the INS and GNSS data....................................................... 101
6.10.1. Raw GNSS receiver data ............................................................................ 101
6.11. Synchronization of INS data with LiDAR and other devices ............................... 103
6.11.1. Synchronization pulses issued by INS ........................................................ 103
6.11.2. Trigging of INS by external devices ............................................................ 103
6.11.3. Synchronization of INS data with LiDAR ..................................................... 103
6.12. Change of the main COM port baud rate ........................................................... 104
6.13. Limitation of the INS maximum output data rate ................................................ 104
APPENDIX A. The Inertial LabsTM INS Calibration.......................................................... 106
APPENDIX B. Variants of the Inertial LabsTM INS mounting relative to the object axes .. 108
APPENDIX C. Full list of the Inertial LabsTM INS commands .......................................... 110
APPENDIX D. Forms of the Inertial LabsTM INS orientation presentation ....................... 111
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
Interface Control Document
1. INTRODUCTION
1.1. Description of the System
The Inertial LabsTM Inertial Navigation System, INS is high-performance
GPS-aided strapdown system that calculates absolute orientation (heading,
pitch and roll) and position (latitude, longitude, altitude) for any device on
which it is mounted. Orientation and position are determined with high
accuracy for both motionless and dynamic applications.
The Inertial LabsTM INS utilizes 3-axes each of precision accelerometers,
magnetometers and gyroscopes to provide accurate heading, pitch and roll of
the device under measure. Integration of gyroscopes’ output provides high
frequency, real-time measurement of the device rotation about all three
rotational axes. Accelerometers and Fluxgate magnetometer measure
absolute Pitch, Roll and magnetic Azimuth at INS initial alignment as well as
providing ongoing corrections to gyroscopes during operation.
The Inertial LabsTM INS has an onboard high-grade Global Navigation
Satellite System (GNSS) receiver which provide high accurate position using
the next GNSS systems:
GPS L1, L2, L2C;
GLONASS L1, L2;
Galileo E1;
BeiDou B1;
Compass3;
SBAS;
QZSS.
Inertial LabsTM provides three models of INS products:
INS-B (Basic model) – uses MEMS grade magnetometers, high grade
IMU and high grade single antenna GNSS receiver;
INS-P (Professional model) – uses high-grade Fluxgate magnetometers, high grade IMU and high grade single antenna GNSS receiver;
INS-D (Dual antenna model) – uses high grade IMU, dual-antenna
GNSS receiver and measures static and dynamic Heading,
independent on magnetic field disturbance.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
Interface Control Document
For INS operations it is necessary to connect one (for INS-B, INS-P) or two
(for INS-D) active antennas to the TNC connector(s) on the back side of the
Inertial LabsTM INS (see Fig.1.1, Fig.1.2).
Fig.1.1. Inertial LabsTM INS-B and INS-P
Fig.1.2. Inertial LabsTM INS-D
Fig.1.3 shows the INS own coordinate system Oxoyozo. This coordinate
system is body-fixed and defined as the calibrated sensors coordinate
system. Non-orthogonality between axes of the body-fixed coordinate system
Oxoyozo is an order of 0.01°.
Measured angles are the standard Euler angles of rotation from the Earthlevel frame (East-North-Up) to the body frame, heading first, then pitch, and
then roll.
Orientation angles, measured by the Inertial LabsTM INS, are not limited and
are within common ranges:
Heading 0…360 ;
Pitch
±90 ;
Roll
±180 .
Also the Inertial LabsTM INS provides orientation calculation in quaternion
form. See “APPENDIX D. Forms of the Inertial LabsTM INS orientation
presentation”.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
8
INS
Interface Control Document
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
Interface Control Document
1.2. Principles of the Inertial LabsTM INS Operation
Fig.2.1 shows the operational diagram of the Inertial LabsTM INS. The INS
uses gyros to measure absolute angular rate of the carrier object,
accelerometers to measure the specific force (apparent acceleration of the
object), magnetometers to measure components of the Earth magnetic field.
Antenna
rxo
Gy0
rzo
Gx0
axo
Ay0
A z0
INS velocity
INS orientation
INS errors
estimation
ayo
azo
INS errors correction
Ax0
My0
mxo
myo
mzo
Mz0
INS
algorithm
Earth magnetic
field
components
Kalman filter
based algorithm
Mx0
INS velocity
INS orientation
Gz0
INS position
ryo
INS position
Magnetometers Accelerometers Gyros
Initial pos. and vel.
GNSS pos.
Initial orientation
GNSS vel.
GNSS
receiver
Initial
alignment
algorithm
Fig.2.1. Operational Diagram of the Inertial LabsTM INS
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
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Orientation angles (heading, pitch and roll) are obtained by using special
integration of gyros outputs with correction from GNSS position and velocity
data.. INS-D also utilises gyros correction by heading calculated as direction
between two GNSS antennas.
Position (latitude, longitude and altitude) are calculated using special
integration of accelerometers and known orientation. To avoid accumulation
of the INS error they are estimated and compensated using Global
Navigation Satellite System (GNSS) data provided by onboard receiver and
pressure sensor data.
Also accelerometers are used to determine initial attitude of the INS, and.
magnetometers are used to determine initial heading. In INS-D unit initial
heading is calculated as direction between two antennas if GNSS data are
available and RTK solution for heading is made by on-board GNSS receiver.
The base of the INS algorithm is robust Kalman filter which is used for
estimation of the INS errors in orientation, position, velocity calculation and
also gyros and accelerometers biases. For this purpose the Kalman filter
uses aiding information from GNSS about position and velocity, and also
barometric altitude calculated fro, pressure sensor data.
As result of integration of all above data, the INS provides accurate
calculation of stabilized heading, pitch and roll angles, latitude, longitude and
altitude, east, north and vertical velocity. The Kalman filter automatically
adjusts for changing of dynamic conditions.
Note the initial position and velocity are provided by the GNSS receiver if it
has solution. If GNSS data are not available then the initial position are taken
from the INS nonvolatile memory. There the initial position can be changed
using the LoadINSpar command (see Table 6.22, bytes #8-19) or using the
INS Demo Program (that is more easy)
After the Inertial LabsTM INS power on an initialisation of the o-nboard GNSS
receiver starts that takes about 25 seconds. Then the INS is ready to receive
commands from the host computer and to start required operation.
After start the Inertial LabsTM INS it requires about 30 seconds for initial
alignment process. At this initial orientation angles are determined as initial
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
11
INS
Interface Control Document
conditions for integration of gyros outputs. Also gyros bias is estimated using
Kalman filter for next compensation. Therefore don’t move the INS during
initial alignment process. If this requirement is not met then large errors may
be occurred in orientation angles calculation.
Features of INS algorithm and possibilities of their adjustment are described
in the INS Demo User’s Manual, Rev.2.0 and higher, section “4.3.1.
“Settings” tab of «Correction options…» window”.
1.3. True and magnetic heading
As the Inertial LabsTM INS uses magnetic sensors for heading reference, then
it directly determines just magnetic heading. Then INS calculates true North
heading using the current magnetic declination. Declination, also called
magnetic variation, is the difference between true and magnetic North,
relative to a point on the Earth. Declination angle vary throughout the world,
and changes slowly over time. Magnetic declination angle can be entered
directly to the Inertial LabsTM INS memory using special command (see Table
6.22, bytes #4-7) or the Inertial LabsTM INS Demo Program. Also, the
magnetic declination can be calculated by INS itself based on calculated
latitude, longitude, altitude and date.
Both INS unit onboard and INS Demo Program calculate the magnetic
declination using the World Magnetic Model WMM2015 produced by the U.S.
National Geophysical Data Center and the British Geological Survey,
http://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml
The World Magnetic Model is the standard model of the US Department of
Defense, the UK Ministry of Defense, the North Atlantic Treaty Organization
(NATO), and the World Hydrographic Office (WHO) navigation and
attitude/heading referencing systems.
Since INS firmware version 2.2.0.2 the INS unit can calculate the magnetic
declination continuously onboard if “Auto” checkbox is checked in the “IMU”
tab of the «Devices Options» window in the INS Demo Program. INS outputs
current magnetic declination in “INS Full Output Data” format (see Table
6.10).
Note using magnetometers for INS heading correction requires necessity of
magnetometers calibration after INS unit installed on carrier object to
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
12
INS
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compensate hard and soft iron effects of the carrier object on the INS
heading determination accuracy (see section “6.7. Calibration of the Inertial
LabsTM INS on hard and soft iron” for details).
1.4. Ground track angle vs heading
Ground track angle or the course over ground azimuth is determined using
the position delta between two position computed. Track angle shows
direction of vehicle motion in horizon plane.
For some carrier objects it is possible to use GNSS track angle instead of
magnetic heading for INS correction. In such case magnetometers can be
switched off, and INS does not require any calibration of magnetometers.
Ground track angle can be used as heading for ground vehicles where the
direction of travel is coincident with the forward axis of the vehicle and the roll
of the vehicle is close to zero. But replacement of heading by the ground
track angle may not be suitable for some marine or airborne applications,
where the direction of travel may be different from the forward axis of the
vehicle because of factors like a crab angle.
Also the ground track angle has no sense when the vehicle is stationary. But
integration of INS with GNSS data allows to use GNSS track angle instead of
magnetic heading for INS correction even at vehicle stops. Only initial vehicle
movement is required to perform calculation of initial heading in INS.
1.5. Using GNSS heading in INS-D
More accurate INS heading correction than use of magnetometers or GNSS
track angle can be provided in INS-D with two antennas installed along
forward axis of carrier object. In INS-D magnetometers also can be switched
off, and INS does not require any calibration of magnetometers in such case.
In contrast to using GNSS track angle, heading calculated on base of two
antennas position does not require vehicle movement strictly in direction of
the forward axis of the vehicle, moreover, vehicle can be stationary.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
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INS
Interface Control Document
2. SCOPE AND APPLICABILITY
This Interface Control Document (ICD) provides details on mechanically
mounting, the electrical connections, powering and software interface
between the Inertial LabsTM INS and host computer. This document is
intended for all parties requiring such information, including engineers and
researchers responsible for implementing the interface.
3. SPECIFICATIONS
See separate document, Inertial Labs INS Datasheet.
4. MECHANICAL INTERFACE
Fig.4.1 sows the outline drawings of the Inertial LabsTM INS. All dimensions
are in millimetres.
Fig.4.1. The Inertial LabsTM INS outline drawing
(all dimensions are in millimetres)
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
14
INS
Interface Control Document
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
15
INS
Interface Control Document
memory. See Appendix B. Variants of the Inertial LabsTM INS mounting
relative to carrier object axes.
To obtain accurate attitude and heading, please remember that mounting is
very important and mounting error can cause attitude and heading errors.
When Inertial LabsTM INS mounting please align it on two base surfaces A, B
relative your system axes.
The Inertial LabsTM INS is mounting on your system by using 4 holes
mm (see Fig.4.2, positions 1).
4.2
Requirements to the mounting surface of the carrier object: flatness tolerance
is 0.03 mm; undulation is Ra=1.25.
4.2. Installation of single GNSS antenna
Usually the INS unit and GNSS antenna are installed in different places of the
carrier object. Moreover, placement of the antenna close to the INS unit is
undesirable because of the antenna impact on the INS magnetometers.
While the best place for the INS unit is center of gravity of the carrier object,
the GNSS antenna must of course be placed with a clear view of the sky with
a sufficient ground plane.
After the INS unit and GNSS antenna installation on the carrier object it is
necessary to measure the antenna position relative to the INS unit, in the
object axes – on the right, forward and up. Then it is necessary to store these
coordinates to the INS nonvolatile memory using the LoadINSPar command
(see Table 6.22, bytes #29-34) or using the INS Demo Program (that is more
easy).
Fig.4.3 shows positive right, forward and up directions of the antenna position
relative to the INS unit.
Important notes:
1. If after the INS mounting its axes (see Fig.1.3) are parallel to the carrier object axes,
then the antenna coordinates should be measured in the directions of X, Y and Z axes.
2. On the other hand, the INS unit can be mounted on the object in any known position (up
to upside-down, upright etc., see Appendix B. Variants of the Inertial Labstm INS mounting
relative to the object axes). In that case please set the GNSS antenna coordinates
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
16
INS
Interface Control Document
measures just in the object axes (on the right, forward and up directions), but not in the
INS axes.
Fig.4.3. Determination of the GNSS antenna position relative to the INS unit
(positive directions)
4.3. Installation of two GNSS antennas for INS-D operation
The Inertial LabsTM INS-D uses heading calculated by dual-antenna GNSS
receiver for the INS correction. Two antennas must be installed in parallel to
the longitudinal axis of the carrier object to allow GNSS receiver to measure
object heading accurately. At this the rover antenna is installed ahead the
master antenna, so direction from the master to the rover antenna is forward
for the carrier object, see Fig.4.4.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
17
INS
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Fig.4.4. Installation of the master and rover GNSS antennas on carrier object
At this requirements for the master antenna installation are the same as
described in section “4.2. Installation of single GNSS antenna”. Position of
the master antenna relative to the center of the INS unit must be measured
and stored to the INS nonvolatile memory.
4.4. Where to install the Inertial LabsTM INS and its antenna for tests
The Inertial LabsTM INS has magnetometers with wide dynamic range and its
sophisticated calibration algorithms allow it to operate in many environments.
For optimal performance however, you should mount the Inertial LabsTM INS
with the following considerations in mind.
Locate the Inertial LabsTM INS away from local sources of magnetic
fields
The place for testing must not have ferromagnetic (magneto-susceptible)
materials and the lab room itself must have the level of intrinsic magnetic and
electro-magnetic fields suitable for the magnetic heading system testing:
- inside and near the lab room there must be no powerful source of
magnetic, electrical and electro-magnetic fields. The magnetic field
intensity must not be different from the Earth magnetic field intensity at
the test site more than 0.01%;
- small ferromagnetic objects must be as far as 3 meters from the test
table. Large size ferromagnetic objects such as cars and trucks must be
as far as 15 m from the table;
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
18
INS
Interface Control Document
- it is necessary to conduct a regular check-up of the magnetic field
uniformity inside the lab room.
It is highly recommended to degauss the INS before heading test to remove
permanent magnetization of some components in the INS (if you accidentally
expose the unit to a large magnetic field). You can use a hand-held
degausser (tape eraser) to demagnetize the INS. Most audio and video
degaussing units can be used. Follow the instructions for your demagnetizer.
If heading accuracy is not checked and only pitch and roll accuracy are
tested then there are no requirements to magnetic fields and ferromagnetic
materials near place of the Inertial LabsTM INS mounting,
The Inertial LabsTM INS should be mounted in a physically stable
location
Choose a location that is isolated from excessive shock, oscillation, and
vibration. Special rotary table must be used for the Inertial LabsTM INS
accuracy testing, that mounted on a special testing basement which is free
from the laboratory oscillations and vibrations.
Tests on vibrations and shocks are fulfilled separately from the main
accuracy tests.
Install the Inertial LabsTM INS and GNSS antenna on the same base
For test of the INS position and linear velocity calculation, it is necessary to
connect the active GNSS antenna(s) to the INS. Both INS unit and the
antenna(s) should be installed immovable each to other. Position of the
antenna(s) relative to the INS unit should be measured and stored to the INS
nonvolatile memory (see sections “4.2. Installation of single GNSS antenna”
and “4.3. Installation of two GNSS antennas for INS-D operation”, for details).
4.5. Where to install the Inertial LabsTM INS on the object
It is necessary to follow the recommendations listed in the section 4.3
whenever it is possible, when installing the Inertial LabsTM INS on an carrier
object.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
19
INS
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Inertial LabsTM INS should be installed on an object as far as
possible from large ferromagnetic masses of the object and powerful
sources of magnetic, electrical and electro-magnetic fields
Inertial LabsTM INS software allows compensation of hard and soft iron effects
of the carrier object on the heading measurement accuracy. For this purpose,
field calibration of the INS magnetometers is provided. This calibration does
not require any additional equipment, but it requires turns of the carrier
object, on which the INS is mounted.
Note that the above field calibration is correct until the residual magnetic field
of the object surrounding the INS is changed. If this field is changed due to
displacement of ferromagnetic masses of the object or magnetic field
sources, the INS should be re-calibrated.
Field calibration procedure of the Inertial LabsTM INS can be performed by
two means:
by INS itself using special commands described in the section 6.7;
using the Inertial LabsTM INS Demo Program.
The INS Demo Program provides more variants of the field calibration and is
more convenient for use, but it requires connection of the INS to PC.
Calibration of the INS itself is performed without its disconnection from the
host system on the carrier object.
More detailed description of the field calibration procedure is given in the
section “6.7. Calibration of the Inertial LabsTM INS on hard and soft iron”.
It is preferable to locate the Inertial LabsTM INS as close to the
center of gravity of the object as possible
With such location, effects of linear accelerations during oscillations on the
INS accelerometers are reduced, and therefore, orientation angle
determination errors are also reduced.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
20
INS
Interface Control Document
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
21
INS
Interface Control Document
For INS with RS-232 interface: the Binder Series 423, 425 or 723
female 12 pin connector (or cordset), part # 09 0130 70 12, # 99 5130
40 12, or # 79 6130 20 12.
For INS with RS-422 interface: the Binder Series 423 or 723 female 19
pin connector (or cordset), part # 99 5662 00 19, # 99 5662 75 19 or #
09 0462 70 19, # 99 0462 75 19.
Fig.5.3 shows connector pinout of the Inertial LabsTM INS with RS-232
interface. Table 5.1 contains pin diagram of this connector and appropriate
color of wires in cable with mating Binder Series 425 Female plug, part # 79
6130 20 12.
Table 5.1. Pin diagram of the Inertial
LabsTM INS RS-232 connector
Pin
A
B
C
D
E
F
G
H
J
K
L
M
Wire color
White
Brown
Green
Yellow
Grey
Pink
Blue
Red
Black
Violet
Grey/pink
Red/blue
Signal
RS232 – RX2
RS232 – TX2
RS232 – RX3
RS232 – TX3
Power
Ground
RS232 – RX1
RS232 – TX1
PPS
GPIO
Do not connect
Do not connect
Fig.5.3. The Inertial LabsTM INS RS-232
connector pinout
(mating side of the connector)
Note: Do not connect anything to pins #L or #M that are connected to INS PCB for
firmware updates.
Fig.5.4 shows connector pinout of the Inertial LabsTM INS with RS-422
interface. Table 5.2 contains pin diagram of this connector and appropriate
color of wires in Alpha Wire cable part number 5478C with 16 conductors.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
22
INS
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Table 5.2. Pin diagram of the Inertial LabsTM
INS RS-422 connector
Pin Pairs
color
G
Yellow
+ Black
R
F
Orange
+ Black
E
P
D
Red
+ Black
O
C
B
N
I
K
T
Fig.5.4. The Inertial LabsTM INS RS422 connector pinout
(mating side of the connector)
L
U
A
M
Blue+
Black,
Brown+
Black
Green+
Black,
White+
Black
Red
+White
Wire
color
Yellow
Black
Orange
Black
Signal
RS422-A
Red
Black
Blue
RS422-B
RS422-X
RS422-Z
Reserve1
POWER
GND
RS232-RX2
Brown
2xBlack
RS232-TX2
GND2
Green
White
2xBlack
RS232-RX3
RS232-TX3
GND3
Red
White
PPS
GPIO
Do not connect
Do not connect
H
Reserve2
S
Reserve3
Note: Do not connect anything to pins #A and #M that are connected to INS PCB for
firmware updates.
Since the serial number F1560007 the Inertial LabsTM INS has three COMports with RS-232 interface on default:
COM1 is the main. It is used for commands and data transfer between
the Inertial LabsTM INS and the host computer.
COM2 is used for output of the raw GNSS receiver data (see section
6.10. Post processing of the INS data) or NMEA data set.
COM3 has two functions:
o to receive data for differential corrections of GNSS (DGPS mode);
o or to output $GPRMC messages (since INS firmware version
2.2.0.3)
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
23
INS
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Table 5.3. Electrical specifications
Parameter
Input Supply
INS-B Current
INS-P Current
INS-D Current
Conditions
VDD = +12V
VDD = +12V
VDD = +12V
Min
+9
200
225
325
Typical
+12V
220
245
345
Max
+36V
250
275
355
Units
Volts DC
mA
mA
mA
At the Inertial LabsTM INS operations, it should be connected to the host
system that provides command interface described in the section 6 and the
INS powering.
5.1. Connection of the Inertial LabsTM INS with RS-232 interface to the
host computer for tests
For tests the Inertial LabsTM INS with RS-232 interface can be connected to
PC by cables as Fig.5.5 -- Fig.5.7 show. For usual operations the COM1 port
of INS should be connected to PC using cable 1 (see Fig.5.5). To use the raw
GNSS data and NMEA messages the cable 2 or cable 3 should be used (see
Fig.5.6). To provide the INS operation with DGPS mode the Cable 3 should
be used (see Fig.5.7).
As default, the Inertial Labs provides cable 1 for the INS evaluation.
For the Inertial LabsTM INS powering the AC/DC adapter can be used which
receives the power from the 100…240V 50…60Hz AC power source. This
AC/DC adapter is provided by the Inertial Labs and is included in the delivery
set.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
24
INS
Interface Control Document
GNSS antenna
X4
InertialLabs
INS
Cable1
X1
X3
9
12
Host Computer
X2
AC-DC POWER
SUPPLY
2
+12V
Fig.5.5. The diagram of electric connection of the Inertial LabsTM INS to host
computer (PC) for tests
GNSS antenna
X4
9
X5
“COM2”
InertialLabs
X1
INS
Cable2
X3
9
12
“COM1”
Host Computer
X2
AC-DC POWER
SUPPLY
2
+12V
Fig.5.6. The diagram of electric connection of the Inertial LabsTM INS to PC with
output of the raw GNSS data or NMEA data set
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
25
INS
Interface Control Document
X5
9
Radio Modem
“COM3”
GNSS antenna
X4
9
X6
“COM2”
InertialLabs
X1
INS
Cable3
X3
9
12
“COM1”
Host Computer
X2
AC-DC POWER
SUPPLY
+12V
2
Fig.5.7. The diagram of electric connection of the Inertial LabsTM INS with DGPS
mode to PC for tests
The delivery set for the INS with RS-232 interface electrical connection to PC
is provided by the Inertial Labs and includes:
interface cable 1 for the Inertial LabsTM INS COM1 port connection
to the
-port of PC or another device, with branch wires for the
Inertial LabsTM INS DC powering;
COM-to-USB converter for connection of the INS to PC through the
USB port;
AC/DC adapter.
Also Inertial Labs INS Demo software is included in the delivery set for quick
evaluation of the Inertial LabsTM INS.
Fig.5.8 – Fig.5.10 show the diagram of the interface cables 1, 2, 3 for the
Inertial LabsTM INS connections to the
-ports of host computer and to the
DC power source.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
26
INS
Interface Control Document
X1
Cable1
12
X3
9
X2
2
Fig.5.8. The diagram of the interface cable 1 for the Inertial LabsTM INS connection
to the
-port of the host computer and to the AC/DC adapter
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
27
INS
Interface Control Document
X4
9
X1
X3
Cable2
9
12
X2
2
X4(COM2)
X1-Cable Connector
Binder 423 / Binder 723
1
DCD
2
Rx
3
Tx
4
DTR
5
SG
6
DSR
7
RTS
8
CTR
9
RI
RS232-RX2
A
RS232-TX2
B
RS232-RX3
C
RS232-TX3
D
Power
E
Ground
F
1
DCD
RS232-RX1
G
2
Rx
RS232-TX1
H
3
Tx
PPS
J
4
DTR
GPIO
K
5
SG
Do not connect
L
6
DSR
Do not connect
M
7
RTS
8
CTR
9
RI
X2(Power)
GND
Vdd
X3(COM1)
X3,X4-Female Connector DB -9F
in the backshell
Fig.5.9. The diagram of the interface cable 2 for the Inertial LabsTM INS connections
to two
-ports of the host computer and to the AC/DC adapter
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
28
INS
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Fig.5.10. The diagram of the interface cable 3 for the Inertial LabsTM INS connections
to two
-ports of the host computer, to radio modem and to the AC/DC adapter
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
29
INS
Interface Control Document
5.2. Connection of the Inertial LabsTM INS with RS-422 interface to the
host computer for tests
Usual PC has no possibility of devices connection through RS-422 interface
directly. Therefore for the Inertial LabsTM INS with RS-422 interface
connection to PC it is necessary to use some converter, for example Serialto-USB MOXA 1130 converter, which is supplied with INS unit by the Inertial
Labs. In other parts above diagrams Fig.5.5 -- Fig.5.7 are still valid.
Fig.5.11, Fig.5.12 show the diagram of the interface cables 1, 3 for the
Inertial LabsTM INS with RS-422 interface connections to the
-ports of
host computer and to the DC power source.
The delivery set for the INS with RS-422 interface electrical connection to PC
is provided by the Inertial Labs and includes:
interface cable 1 for the Inertial LabsTM INS COM1 port connection
to the
-port MOXA converter, with branch wires for the Inertial
TM
Labs INS DC powering;
USB-to-Serial MOXA converter for connection of the INS to PC
through the USB port;
AC/DC adapter.
Also Inertial Labs INS Demo software is included in the delivery set for quick
evaluation of the Inertial LabsTM INS.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
30
INS
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X1
Cable1
12
X3
9
X2
2
RS422-A
G
1
T-
RS422-B
R
2
T+
RS422-Y
F
3
R+
RS422-Z
E
4
R-
GND1
P
5
GND
Power
D
6
Ground
O
7
GND2
N
GND3
T
Load
A
Load-gnd
M
twisted pair
twisted pair
8
9
Connector DB-9F
in the backshell
Micro button
Female cable connector
Binder Series 723
Part # 09 0462 70 19
For loading programm
X2(Power)
GND
Vdd
Connector DC Power recept 5.5X2.1mm
Fig.5.11. The diagram of the interface cable 1 for the Inertial LabsTM INS RS-422
connection to the host computer and to the AC/DC adapter
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
31
!!! Only for Uport1130
X3(RS422)-Female
X1-Cable Connector
INS
Interface Control Document
X5
9
“COM3”
X4
9
“COM2”
X1
X3
9
19
“RS-422”
X2
2
X3(RS422)-Female
X1-Cable Connector
RS422-A
G
1
twisted pair
twisted pair
T-
RS422-B
R
2
T+
RS422-Y
F
3
R+
RS422-Z
E
4
R-
GND1
P
5
GND
Power
D
6
Ground
O
7
twisted pair
twisted pair
8
X4(COM2)
RS232-RX2
C
1
RS232-TX2
B
2
Rx
GND2
N
3
Tx
PPS
L
X5(COM3)
DTR
5
SG
Vdd
DSR
GND
6
I
1
DCD
7
RTS
RS232-TX3
K
2
Rx
8
CTR
GND3
T
3
Tx
9
RI
4
DTR
5
SG
U
6
DSR
reserve 1
H
7
RTS
reserve 2
S
8
CTR
9
RI
Do not connect
A
Do not connect
M
Connector DB -9F
in the backshell
4
RS232-RX3
GPIO
9
DCD
X2(Power)
Connector DC Power
recept 5.5X2.1mm
Female Connector DB -9F
in the backshell
Female Connector DB -9F
in the backshell
Female cable connector
Binder Series 723
Part # 09 0462 70 19
Fig.5.12. The diagram of the interface cable 3 for the Inertial LabsTM INS RS-422
connections to two
-ports of the host computer, to radio modem and to the
AC/DC adapter
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
32
INS
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5.3. PPS description
The Inertial LabsTM INS outputs the pulse per second (PPS) signal generated
by GNSS receiver. Appropriate pin of the INS main connector provides the
PPS signal (see Table 5.1 and Table 5.2).
The leading edge of the PPS pulse is always the trigger / reference:
Negative – generates a normally high, active low pulse with the falling
edge as the reference;
Positive – generates a normally low, active high pulse with the rising
edge as the reference.
PPS pulse is shown on the Fig.5.13.
Fig.5.13. PPS pulse
Since the INS firmware version 2.2.0.3 the pulse polarity, period and pulse
width are user-adjustable and can be set using the Inertial LabsTM INS Demo
Program since version 2.0.22.84 from 04/22/2016 (see INS Demo User’s
Manual, Rev.1.8, section “13.1.Control of PPS output signal”). By default
GNSS receiver generates a normally high, active low (negative polarity) pulse
with the falling edge as the reference. Default PPS period is 1 second, pulse
width is 1000 microseconds.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
33
INS
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Note: Cable set provided with the Inertial Labs INS is designed for INS connection to PC
and therefore it does not transfer PPS signal. To receive PPS signal it is necessary to
make another cable with PPS wire. Please contact Inertial Labs to purchase cable with
PPS signal transferring.
5.4. GPIO description
The Inertial LabsTM INS provides general-purpose input/output (GPIO) pin in
the main connector (see pin diagram of the Inertial LabsTM INS connector in
Table 5.1 and Table 5.2).
Since the INS firmware version 2.2.0.3 the GPIO can be used for mark inputs
to trigger specific GNSS raw receiver data. TTL mark pulse configuration is
the same as Fig.5.13 shows. Adjustment of the mark input signal processing
is provided by the Inertial LabsTM INS Demo Program since version 2.0.22.84
from 04/22/2016 (see INS Demo User’s Manual, Rev.1.8, section
“13.2.Processing of mark input signal”): processing of the mark input signal
can be enabled or disabled, polarity can be changed and a time offset and
guard against extraneous pulses can be added.
To allow mark inputs the MARK_switch should be set to 1 (see section 6.4.1).
When a pulse is detected at GPIO mark input then the GNSS receiver
generates asynchronous MARK2POS and MARK2TIME logs which are
added to the raw GNSS data.
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
34
INS
Interface Control Document
6. SOFTWARE INTERFACE
After the Inertial LabsTM INS power on an initialisation of the onboard GNSS
receiver starts that takes about 25 seconds. During this initialization the INS’
LED indicator (see Fig.5.1) lights yellow. After the initialization completed the
INS’ indicator lights red, and the INS works in the mode of commands
waiting.
If the auto start option is enabled the INS starts operation automatically after
power on (see section 6.8 for more details). The INS indicator lights green.
The commands are transmitted through the COM1 serial port according to
the protocol RS232 with baud rate 115200 bps (default settings).
Table 6.1.
-port parameters
-port parameters
Baud rate
115200
Data bits
8
Parity
none
Stop bits
1
Notes
1. Other baud rate than 115200 bps can be set for INS with firmware version since 2.2.0.0.
See section “6.12. Change of the main COM port baud rate” for details.
2. The Inertial LabsTM INS with RS-422, RS-485, CAN 2.0 interfaces are also available.
All commands and messages to / from the Inertial LabsTM INS have the byte
structure shown in the Table 6.2. Exception is done for the INS output in the
NMEA and TSS1 text format (see section 6.2).
Table 6.2. Byte structure for all commands and messages to / from the INS
Byte
0
1
2
3
4, 5
6 .. (n-1) n, (n+1)
number
Check
Header
Header Message INS data Message
Payload
Parameter
sum
0
1
type
identifier
length
Length
1 byte
1 byte
1 byte
1 byte
1 word
Variable 1 word
0xAA
0x55
Equal to n
In INS
Note
messages
In the Table 6.2 and in all other tables there is denoted:
TM
Inertial Labs, Inc Address: 39959 Catoctin Ridge Street, Paeonian Springs, VA 20129 U.S.A.
Tel: +1 (703) 880-4222, Fax: +1 (703) 935-8377 Website: www.inertiallabs.com
35
INS
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word = unsigned 2 byte integer;
sword = signed 2 byte integer.
Message type is equal to:
0 – for commands;
1 – for transferred data.
All the INS outputs are data, therefore they have Message type = 1.
INS data identifier is used in INS output data only. This byte is equal to code
of the command from the host system which requested this INS message.
See all commands code in “APPENDIX C. Full list of the Inertial LabsTM INS
commands”.
Note byte #3 in the block of the initial alignment data is equal to set output
data rate (see Table 6.20). In all other messages and commands byte #3 in
the Table 6.2 is zero.
Note: in INS with firmware version before 2.1.2.0 this byte #3 is zero in all
messages.
The Message length is the number of bytes in the message without header.
The Check sum is the arithmetical sum of bytes 2…(n–1) (all bytes without
header). In the check sum the low byte is transmitted first (see Table 6.3).
Table 6.3. Format of the check sum transmitting
byte0
low byte
byte1
high byte
Important note
The low byte is transmitted by first in all data denoted as word, sword, float.
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6.1. Operational modes of the Inertial LabsTM INS
The Inertial LabsTM INS can operate in the four modes:
1. Idle mode. All sensors and electronics are powered. The INS
microprocessor waits any command from the host computer to start operate
in one of the next modes. In the idle mode the indicator of INS lights red.
2. Continuous operating mode. In this mode the INS operates in the endless
loop, providing the continuous output of calculated position, orientation and
other data according to chosen output data format (see section 6.2). Data
rate is set by user from 1 Hz to 200 Hz. In the Continuous operating mode
indicator of the INS lights green.
3. “On Request” operating mode. It is close to the Continuous operating
mode, but the INS sends only one data block after each Request command
issued from host computer. In this mode indicator of the INS lights green.
4. Calibration operating mode. In this mode the embedded calibration
procedure is performed for compensation of hard and soft iron effects of the
carrier object. See section 6.7 for more details.
6.2. Output Data Formats of the Inertial LabsTM INS in the Operating
Modes
The next output data formats are available in the “Continuous” and “On
Request” operating modes:
INS OPVT;
INS QPVT;
INS OPVT2A;
INS OPVT2AW;
INS OPVT2Ahr;
INS Full Output Data;
INS Sensors Data;
INS Minimal Data;
INS NMEA Output;
INS Sensors NMEA Output;
TSS1 Output.
TM
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Note output data formats INS OPVT2A, INS OPVT2AW, INS OPVT2Ahr are
created for INS-D to output orientation data calculated by dual antenna
GNSS receiver. But all listed above data formats can be used for any INS
model – INS-B, INS-P, INS-D, absent data will be replaced by zeros.
6.2.1. The “INS OPVT” (Orientation, Position, Velocity, Time) data format
This is default data format. It provides the INS output in the form of:
3 orientation angles (heading, pitch and roll);
calibrated outputs of the 9 sensors (gyros, accelerometers,
magnetometers) that give information about current angular rate, linear
acceleration of the INS and components of outer magnetic field;
AHRS (IMU) service data;
position – latitude, longitude, altitude above mean sea level (or heave);
east, north and vertical velocity;
GNSS position and velocity data;
GPS reference time;
GPS service data;
calibrated data from the pressure sensor – pressure and barometric
altitude.
More correctly gyros, accelerometers, magnetometers output are integrated
angular rate, linear acceleration (specific force), magnetic field increments. In
the INS output these increments are divided by time step of data output so
they may be interpreted as average angular rates, linear acceleration and
magnetic field for cycle of data output. On the other hand, incremental sensor
data are good for the INS using as IMU (inertial measurement unit) – they are
delta Theta and Delta Velocity divided by time step of data output.
Structure of the INS data blocks at the “INS OPVT” data format corresponds
to the Table 6.2 with payload shown in the Table 6.4.
Note: before INS firmware version 2.2.1.0 other GNSS information (TS_gps, GNSS_info)
were shown in bytes #80, 81. This information can be returned if uncheck “Extended info”
checkbox in INS Demo Program in “GNSS receiver” tab of “Devices options” menu item.
Maximum data rate for the INS output at the “INS OPVT” data format is
limited to 100 Hz at standard COM-port baud rate 115200 bps. See Table
6.55 for maximum data rate at other baud rates.
TM
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Table 6.4. The INS message payload at the “INS OPVT” data format
Byte
0 – 1 2 – 3 4 – 5 6 – 11 12 – 17 18 – 23 24 – 25 26 – 27 28 – 29
number
GyroX, AccX, MagX,
Parameter Heading Pitch Roll GyroY, AccY, MagY, USW Vinp Temper
GyroZ AccZ MagZ
3
3
3
2 byte 2 byte 2 byte
2 byte 2 byte 2 byte
Length
2 byte 2 byte 2 byte
word sword sword
word word sword
sword sword sword
MagneAngular
Supply
AcceleTemper
tic
Orientation angles,
rates,
voltage,
rations
ature,
Note
fields,
deg*100
deg/s
VDC*
ºC*10
g*KA
nT/10
*KG
100
Table 6.4 (continued)
Byte
number
Parameter
Length
Note
30 – 33
34 – 37
Latitude Longitude
4 byte
integer
4 byte
integer
deg
deg *1.0e7
*1.0e7
38 – 41
42 – 45
Altitude or
Heave
4 byte
integer
East
speed
4 byte
integer
m*100
m/s*100
46 – 49
50 – 53
4 byte
integer
Vertical
speed
4 byte
integer
m/s*100
m/s*100
North speed
Table 6.4 (continued)
Byte
number
54 – 57
58 – 61
62 – 65
66 – 69 70 – 71
72 – 75
Parameter
Latitude
GNSS
Longitude
GNSS
Altitude
GNSS
Horizont
al speed
Track
over
ground
Vertical
speed
Length
4 byte
integer
4 byte
integer
4 byte
integer
4 byte
integer
2 byte
word
4 byte
integer
Note
deg *1.0e7 deg *1.0e7
m*100
m/s*100 deg*100 m/s*100
Table 6.4 (continued)
Byte
number
76-79
80
81
Note
83-84
85-86 87-90
GNSS_ GNSS_
#solnSVs V_latency P_bar
info1
info2
2 byte
4 byte 1 byte 1 byte
1 byte
2 byte
word
ms
s*1000 Pa/2
Parameter ms_gps
Length
82
TM
H_bar
91
New
GPS
4 byte
1 byte
integer
m*100
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Notes:
1. Values of KG, KA are scale factors depending on gyro and accelerometer range:
Gyro range, deg/sec 250 or 300 450 or 500 1000 2000
KG
100
50
20
10
Accelerometer range, g
2
6
8
KA 10000
5000 4000
2. Angular rates, linear accelerations and magnetic fields are in the carrier object axes (X
is lateral axis, Y is longitudinal axis, Z is vertical axis). The INS orientation relative to the
carrier object axes is set by alignment angles (see Appendix B. Variants of the Inertial
LabsTM INS mounting relative to the object axes).
3. USW is unit status word (see section 6.9 for details).
4. Vinp is input voltage of the INS.
5. Temper is averaged temperature in 3 gyros.
6. ms_gps are milliseconds from the beginning of the GPS reference week;
7. GNSS_info1, GNSS_info2 contain information about GNSS data (see Table 6.5,
Table 6.6);
8. #SolnSVs is number of satellites used in navigation solution;
9. V_latency is latency in the velocity time tag in milliseconds;
10. Choice of altitude or heave and appropriate rate for output is supported in INS-D units
and depends on switch h_output (see section 6.5 for details).
11. P_bar, H_bar – pressure and barometric height.
12. New_GPS is indicator of new update of GPS data;
13. The low byte is transmitted by first.
Table 6.5. GNSS_info1 – information about GNSS data
Bit
Value and Description
0 – 3 Position type:
0 – Single point position;
1 – DGPS (pseudorange differential solution);
2 – Solution calculated using corrections from SBAS;
3 – PPP solution;
4 – RTK (other) solution;
5 – RTK (narrow-int) solution;
6 – Other.
4 – 7 Pseudorange iono correction:
0 – unknown or default Klobuchar model;
1 – Klobuchar Broadcast;
2 – SBAS Broadcast;
3 – Multi-frequency Computed;
4 – DGPS (pseudorange differential correction);
5 – NovAtel Blended Iono Value.
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Table 6.6. GNSS_info2 – information about GNSS data
Bit
Value and Description
0 – 1 Solution status:
0 – GNSS solution is computed;
1 – insufficient observations;
2 – not yet converged from cold start;
3 – other reason of absent solution.
2 – 3 GPS reference time status:
0 – time validity is unknown;
1 – time is coarse set and is being steered;
2 – position is lost and the range bias cannot be calculated;
3 – time is fine set and is being steered.
4
1 – GPS GNSS signal is used
5
1 – GLONASS GNSS signal is used
6
1 – Galileo GNSS signal is used
7
1 – BeidDou GNSS signal is used
6.2.2. The “INS QPVT” (Quaternion of orientation, Position, Velocity,
Time) data format
This data format is near the same as the “INS OPVT” format but provides the
quaternion of orientation instead of orientation angles. See “APPENDIX D.
Forms of the Inertial LabsTM INS orientation presentation” for correct
relationship between orientation angles and quaternion.
The “INS QPVT” format provides output in the form of:
Quaternion of orientation;
calibrated outputs of the 9 sensors (gyros, accelerometers,
magnetometers) that give information about current angular rate, linear
acceleration of the INS and components of outer magnetic field;
AHRS (IMU) service data;
position – latitude, longitude, altitude above mean sea level (or heave);
east, north and vertical velocity;
GNSS position and velocity data;
GPS reference time;
GPS service data;
calibrated data from the pressure sensor – pressure and barometric
altitude.
More correctly gyros, accelerometers, magnetometers output are integrated
angular rate, linear acceleration (specific force), magnetic field increments. In
TM
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the INS output these increments are divided by time step of data output so
they may be interpreted as average angular rates, linear acceleration and
magnetic field for cycle of data output. On the other hand, incremental sensor
data are good for the INS using as IMU (inertial measurement unit) – they are
delta Theta and Delta Velocity divided by time step of data output.
Structure of the INS data blocks at the “INS QPVT” data format corresponds
to the Table 6.2 with payload shown in the Table 6.7.
Note: before INS firmware version 2.2.1.0 other GNSS information (TS_gps, GNSS_info)
were shown in bytes #82, 83. This information can be returned if uncheck “Extended info”
checkbox in INS Demo Program in “GNSS receiver” tab of “Devices options” menu item.
Maximum data rate for the INS output at the “INS QPVT” data format is
limited to 100 Hz at standard COM-port baud rate 115200 bps. See Table
6.55 for maximum data rate at other baud rates.
Table 6.7. The INS message payload at the “INS QPVT” data format
Byte
number
0-7
Parameter
Lk0, Lk1,
Lk2, Lk3
Length
4
2 byte
sword
Note
8 – 13
14 – 19
20 – 25 26 – 27 28 – 29
GyroX,
GyroY,
GyroZ
3
2 byte
sword
AccX,
AccY,
AccZ
3
2 byte
sword
MagX,
MagY,
MagZ
3
2 byte
sword
Accelerations
g*KA
Magnetic fields,
nT/10
Quaternion
Angular
of orientation rates, deg/s
*10000
*KG
30-31
USW
Vinp
Temper
2 byte
word
2 byte
word
2 byte
sword
Supply
Temper
voltage,
ature,
VDC*
ºC*10
100
Table 6.7 (continued)
Byte
number
Parameter
Length
Note
32 – 35
36 – 39
Latitude Longitude
4 byte
integer
deg
*1.0e7
4 byte
integer
deg
*1.0e7
TM
40 – 43
44 – 47
48 – 51
52 – 55
Altitude or
Heave
4 byte
integer
East
speed
4 byte
integer
North
speed
4 byte
integer
Vertical
speed
4 byte
integer
m*100
m/s*100
m/s*100
m/s*100
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Table 6.7 (continued)
Byte
number
56 – 59
60 – 63
64 – 67
68 – 71 72 – 73 74 – 77
Parameter
Latitude
GNSS
Longitude
GNSS
Altitude
GNSS
Horizont
al speed
Length
4 byte
integer
4 byte
integer
4 byte
integer
4 byte
integer
Note
deg *1.0e7 deg *1.0e7
m*100
Track
Vertical
over
speed
ground
2 byte
word
4 byte
integer
m/s*100 deg*100 m/s*100
Table 6.7 (continued)
Byte
number
78-81
82
Parameter ms_gps
Length
4 byte
Note
ms
83
GNSS_ GNSS
info1
info2
1 byte
84
85-86
87-88 89-92
#SolnSVs V_latency P_bar H_bar
1 byte
1 byte
2 byte
s*1000
93
New
GPS
2 byte 4 byte
1 byte
word integer
Pa/2
m*100
Notes:
1. The “INS QPVT” data format is implemented in INS with firmware since version 2.1.2.0.
2. Values of KG, KA are scale factors depending on gyro and accelerometer range:
Gyro range, deg/sec 250 or 300 450 or 500 1000 2000
KG
100
50
20
10
Accelerometer range, g
KA
2
10000
6
5000
8
4000
3. Angular rates, linear accelerations and magnetic fields are in the carrier object axes (X
is lateral axis, Y is longitudinal axis, Z is vertical axis). The INS orientation relative to the
carrier object axes is set by alignment angles (see Appendix B. Variants of the Inertial
LabsTM INS mounting relative to the object axes).
4. USW is unit status word (see section 6.9 for details).
5. Vinp is input voltage of the INS.
6. Temper is averaged temperature in 3 gyros.
7. ms_gps are milliseconds from the beginning of the GPS reference week;
8. GNSS_info1, GNSS_info2 contain information about GNSS data (see Table 6.5,
Table 6.6);
9. #SolnSVs is number of satellites used in navigation solution;
10. V_latency is latency in the velocity time tag in milliseconds;
11. Choice of altitude or heave and appropriate rate for output is supported in INS-D units
and depends on switch h_output (see section 6.5 for details).
12. P_bar, H_bar – pressure and barometric height.
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13. New_GPS is indicator of new update of GPS data;
14. The low byte is transmitted by first.
6.2.3. The “INS OPVT2A” (Orientation, Position, Velocity, Time, Dualantenna receiver data) format
The “INS OPVT2A” data format is implemented in INS with firmware since
version 2.2.1.7. This data format is based on the “INS OPVT” format but
provides additional data calculated by dual antenna GNSS receiver:
3 orientation angles (heading, pitch and roll) calculated by INS;
calibrated outputs of the 9 sensors (gyros, accelerometers,
magnetometers) that give information about current angular rate, linear
acceleration of the INS and components of outer magnetic field;
AHRS (IMU) service data;
position – latitude, longitude, altitude above mean sea level (or heave);
east, north and vertical velocity;
GNSS position and velocity data;
GPS reference time;
GPS orientation data;
GPS service data;
calibrated data from the pressure sensor – pressure and barometric
altitude.
Structure of the INS data blocks at the “INS OPVT2A” data format
corresponds to the Table 6.2 with payload shown in the Table 6.8.
Maximum data rate for the INS output at the “INS OPVT2A” data format is
limited to 90 Hz at standard COM-port baud rate 115200 bps. See Table 6.55
for maximum data rate at other baud rates.
TM
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Table 6.8. The INS message payload at the “INS OPVT2A” data format
Byte
0 – 1 2 – 3 4 – 5 6 – 11 12 – 17 18 – 23 24 – 25 26 – 27 28 – 29
number
GyroX, AccX, MagX,
Parameter Heading Pitch Roll GyroY, AccY, MagY, USW Vinp Temper
GyroZ AccZ MagZ
3
3
3
2 byte 2 byte 2 byte
2 byte 2 byte 2 byte
Length
2 byte 2 byte 2 byte
word sword sword
word word sword
sword sword sword
MagneAngular
Supply
AcceleTemper
tic
Orientation angles,
rates,
voltage,
rations
ature,
Note
fields,
deg*100
deg/s
VDC*
ºC*10
g*KA
nT/10
*KG
100
Table 6.8 (continued)
Byte
number
Parameter
Length
Note
30 – 33
34 – 37
Latitude Longitude
4 byte
integer
4 byte
integer
deg
deg *1.0e7
*1.0e7
38 – 41
42 – 45
Altitude or
Heave
4 byte
integer
East
speed
4 byte
integer
m*100
m/s*100
46 – 49
50 – 53
4 byte
integer
Vertical
speed
4 byte
integer
m/s*100
m/s*100
North speed
Table 6.8 (continued)
Byte
number
54 – 57
58 – 61
62 – 65
66 – 69 70 – 71
72 – 75
Parameter
Latitude
GNSS
Longitude
GNSS
Altitude
GNSS
Horizont
al speed
Track
over
ground
Vertical
speed
Length
4 byte
integer
4 byte
integer
4 byte
integer
4 byte
integer
2 byte
word
4 byte
integer
Note
Byte
number
deg *1.0e7 deg *1.0e7
m*100
m/s*100 deg*100 m/s*100
Table 6.8 (continued)
76-79
80
81
82
83-84
85
86-87
88-89
Angles
GNSS_ GNSS_
Heading Pitch
#solnSVs V_latency position
info1
info2
GNSS GNSS
type
2 byte 2 byte
4 byte 1 byte 1 byte
1 byte
2 byte
1 byte
word sword
Orientation
ms
s*1000
angles, deg*100
Parameter ms_gps
Length
Note
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Table 6.8 (continued)
Byte
number
90-91
92-93
Heading STD Pitch STD
GNSS
GNSS
2 byte
2 byte
Length
word
word
Note
STD, deg*100
Parameter
94-95 96-99
100
P_bar H_bar
New
GPS
2 byte 4 byte
1 byte
word integer
Pa/2 m*100
Notes:
1. Values of KG, KA are scale factors depending on gyro and accelerometer range:
Gyro range, deg/sec 250 or 300 450 or 500 1000 2000
KG
100
50
20
10
Accelerometer range, g
2
6
8
KA 10000
5000 4000
2. Angular rates, linear accelerations and magnetic fields are in the carrier object axes (X
is lateral axis, Y is longitudinal axis, Z is vertical axis). The INS orientation relative to the
carrier object axes is set by alignment angles (see Appendix B. Variants of the Inertial
LabsTM INS mounting relative to the object axes).
3. USW is unit status word (see section 6.9 for details).
4. Vinp is input voltage of the INS.
5. Temper is averaged temperature in 3 gyros.
6. ms_gps are milliseconds from the beginning of the GPS reference week;
7. GNSS_info1, GNSS_info2 contain information about GNSS data (see Table 6.5,
Table 6.6);
8. #SolnSVs is number of satellites used in navigation solution;
9. V_latency is latency in the velocity time tag in milliseconds;
10. Angles position type is GNSS position type at orientation calculation (see Table 6.14);
11. Choice of altitude or heave and appropriate rate for output is supported in INS-D units
and depends on switch h_output (see section 6.5 for details).
12. P_bar, H_bar – pressure and barometric height.
13. New_GPS is indicator of new update of GPS data;
14. The low byte is transmitted by first.
6.2.4. The “INS OPVT2AW” (Orientation, Position, Velocity, Time, Dualantenna receiver data, GPS Week) format
The “INS OPVT2AW” data format is implemented in INS with firmware since
version 2.5.0.5. This data format is based on the “INS OPVT2A” format but
also provides the GPS Week number.
Structure of the INS data blocks at the “INS OPVT2AW” data format
corresponds to the Table 6.2 with payload shown in the Table 6.9.
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Maximum data rate for the INS output at the “INS OPVT2AW” data format is
limited to 90 Hz at standard COM-port baud rate 115200 bps. See Table 6.55
for maximum data rate at other baud rates.
Table 6.9. The INS message payload at the “INS OPVT2AW” data format
Byte
0 – 1 2 – 3 4 – 5 6 – 11 12 – 17 18 – 23 24 – 25 26 – 27 28 – 29
number
GyroX, AccX, MagX,
Parameter Heading Pitch Roll GyroY, AccY, MagY, USW Vinp Temper
GyroZ AccZ MagZ
3
3
3
2 byte 2 byte 2 byte
2 byte 2 byte 2 byte
Length
2 byte 2 byte 2 byte
word sword sword
word word sword
sword sword sword
Angular
MagneSupply
AcceleTemper
tic
rates,
voltage,
Orientation angles,
rations
ature,
Note
fields,
deg/s
deg*100
VDC*
ºC*10
g*KA
nT/10
*KG
100
Table 6.9 (continued)
Byte
number
Parameter
Length
Note
30 – 33
34 – 37
Latitude Longitude
4 byte
integer
4 byte
integer
deg
deg *1.0e7
*1.0e7
38 – 41
42 – 45
Altitude or
Heave
4 byte
integer
East
speed
4 byte
integer
m*100
m/s*100
46 – 49
50 – 53
4 byte
integer
Vertical
speed
4 byte
integer
m/s*100
m/s*100
North speed
Table 6.9 (continued)
Byte
number
54 – 57
58 – 61
62 – 65
66 – 69 70 – 71
72 – 75
Parameter
Latitude
GNSS
Longitude
GNSS
Altitude
GNSS
Horizont
al speed
Track
over
ground
Vertical
speed
Length
4 byte
integer
4 byte
integer
4 byte
integer
4 byte
integer
2 byte
word
4 byte
integer
Note
deg *1.0e7 deg *1.0e7
TM
m*100
m/s*100 deg*100 m/s*100
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Table 6.9 (continued)
Byte
number
76-79
80-81
82
83
84
GNSS_ GNSS_
#solnSVs
Parameter ms_gps GPS week
info1
info2
Length
4 byte
Note
ms
2 byte
word
1 byte
1 byte
1 byte
85-86
87
V_latency
Angles
position
type
2 byte
1 byte
s*1000
Table 6.9 (continued)
Byte
number
88-89
90-91
92-93
94-95
96-97
98-101
102
Heading Pitch Heading STD Pitch STD
New
P_bar H_bar
GNSS
GNSS
GPS
GNSS
GNSS
2 byte
2 byte
2 byte
2 byte
2 byte 4 byte
Length
1 byte
word
sword
word
word
word
integer
Orientation angles,
Note
STD, deg*100
Pa/2
m*100
deg*100
Notes:
1. Values of KG, KA are scale factors depending on gyro and accelerometer range:
Gyro range, deg/sec 250 or 300 450 or 500 1000 2000
KG
100
50
20
10
Parameter
Accelerometer range, g
2
6
8
KA 10000
5000 4000
2. Angular rates, linear accelerations and magnetic fields are in the carrier object axes (X
is lateral axis, Y is longitudinal axis, Z is vertical axis). The INS orientation relative to the
carrier object axes is set by alignment angles (see Appendix B. Variants of the Inertial
LabsTM INS mounting relative to the object axes).
3. USW is unit status word (see section 6.9 for details).
4. Vinp is input voltage of the INS.
5. Temper is averaged temperature in 3 gyros.
6. ms_gps are milliseconds from the beginning of the GPS reference week;
7. GNSS_info1, GNSS_info2 contain information about GNSS data (see Table 6.5,
Table 6.6);
8. #SolnSVs is number of satellites used in navigation solution;
9. V_latency is latency in the velocity time tag in milliseconds;
10. Angles position type is GNSS position type at orientation calculation (see Table 6.14);
11. Choice of altitude or heave and appropriate rate for output is supported in INS-D units
and depends on switch h_output (see section 6.5 for details).
12. P_bar, H_bar – pressure and barometric height.
13. New_GPS is indicator of new update of GPS data;
14. The low byte is transmitted by first.
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6.2.5. The “INS OPVT2Ahr” (Orientation, Position, Velocity, Time, Dualantenna receiver data, with high resolution) format
The “INS OPVT2Ahr” data format is implemented in INS with firmware since
version 2.3.0.5. This data format provides the same data as the “INS
OPVT2A” format, but sensors and position data are presented with higher
resolution:
3 orientation angles (heading, pitch and roll) calculated by INS;
calibrated outputs of 3 gyros and 3 accelerometers with high resolution;
calibrated outputs of 3 magnetometers;
AHRS (IMU) service data;
position – latitude, longitude, altitude above mean sea level (or heave),
with high resolution;
east, north and vertical velocity;
GNSS position (with high resolution) and velocity data;
GPS reference time;
GPS orientation data;
GPS service data;
calibrated data from the pressure sensor – pressure and barometric
altitude.
Structure of the INS data blocks at the “INS OPVT2Ahr” data format
corresponds to the Table 6.2 with payload shown in the Table 6.10.
Maximum data rate for the INS output at the “INS OPVT2Ahr” data format is
limited to 70 Hz at standard COM-port baud rate 115200 bps. See Table 6.55
for maximum data rate at other baud rates.
Table 6.10. The INS message payload at the “INS OPVT2Ahr” data format
Byte
0 – 1 2 – 3 4 – 5 6 – 17 18 – 29 30 – 35 37 – 37 38 – 39 40 – 41
number
GyroX, AccX, MagX,
Parameter Heading Pitch Roll GyroY, AccY, MagY, USW Vinp Temper
GyroZ AccZ MagZ
3
3
3
2 byte 2 byte 2 byte
2 byte 2 byte 2 byte
Length
4 byte 4 byte 2 byte
word word sword
word sword sword
integer integer sword
Angular
MagneSupply
Temper
Acceletic
Orientation angles,
rates,
voltage,
ature,
Note
rations,
fields,
deg*100
deg/s
VDC*
ºC*10
g*1.0e6
nT/10
*1.0e5
100
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Table 6.10 (continued)
Byte
number
42 – 49
50 – 57
Parameter
Latitude
Longitude
Length
Note
58 – 61
8 byte
8 byte
integer
integer
deg*1.0e9 deg*1.0e9
62 – 65
Altitude or
Heave
4 byte
integer
m*1000
66 – 69
East
North speed
speed
4 byte
4 byte
integer
integer
m/s*100
m/s*100
70 – 73
Vertical
speed
4 byte
integer
m/s*100
Table 6.10 (continued)
Byte
number
74 – 81
82 – 89
90 – 93
94 – 97 98 – 99 100 – 103
Parameter
Latitude
GNSS
Longitude
GNSS
Altitude
GNSS
Horizont
al speed
Track
over
ground
Vertical
speed
Length
8 byte
integer
8 byte
integer
4 byte
integer
4 byte
integer
2 byte
word
4 byte
integer
Note
deg*1.0e9
deg*1.0e9
m*1000
m/s*100 deg*100 m/s*100
Table 6.10 (continued)
Byte
104-107
number
108
109
110
111-112
113
114-115 116-117
Angles
GNSS_ GNSS_
Heading Pitch
Parameter ms_gps
#solnSVs V_latency position
info1
info2
GNSS GNSS
type
2 byte
2 byte
Length 4 byte 1 byte 1 byte
1 byte
2 byte
1 byte
word
sword
Orientation
Note
ms
s*1000
angles, deg*100
Table 6.10 (continued)
Byte
number
118-119
120-121
Heading STD Pitch STD
GNSS
GNSS
2 byte
2 byte
Length
word
word
Note
STD, deg*100
Parameter
TM
122-123
124-127
128
P_bar
H_bar
New
GPS
2 byte
word
Pa/2
4 byte
integer
m*100
1 byte
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Notes:
1. Angular rates, linear accelerations and magnetic fields are in the carrier object axes (X
is lateral axis, Y is longitudinal axis, Z is vertical axis). The INS orientation relative to the
carrier object axes is set by alignment angles (see Appendix B. Variants of the Inertial
LabsTM INS mounting relative to the object axes).
2. USW is unit status word (see section 6.9 for details).
3. Vinp is input voltage of the INS.
4. Temper is averaged temperature in 3 gyros.
5. ms_gps are milliseconds from the beginning of the GPS reference week;
6. GNSS_info1, GNSS_info2 contain information about GNSS data (see Table 6.5,
Table 6.6);
7. #SolnSVs is number of satellites used in navigation solution;
8. V_latency is latency in the velocity time tag in milliseconds;
9. Angles position type is GNSS position type at orientation calculation (see Table 6.14);
10. Choice of altitude or heave and appropriate rate for output is supported in INS-D units
and depends on switch h_output (see section 6.5 for details).
11. P_bar, H_bar – pressure and barometric height.
12. New_GPS is indicator of new update of GPS data;
13. The low byte is transmitted by first.
6.2.6. The “INS Full Output Data” format
This data format is near the same as the “INS OPVT” format but all sensors
data are in original ADC codes (raw data). Usually the “INS Full Output Data”
format is used by the INS developers for full control of calculations in the INS
microprocessor. Also this format can be used by user at any troubles to get
full data from the INS for next sending them to developers.
Structure of the INS data blocks at the “INS Full Output Data” format
corresponds to the Table 6.2 with payload shown in the Table 6.11.
Note: before INS firmware version 2.2.1.0 other GNSS information (TS_gps, GNSS_info)
were shown in bytes #84, 85. This information can be returned if uncheck “Extended info”
checkbox in INS Demo Program in “GNSS receiver” tab of “Devices options” menu item.
Maximum data rate for the INS output at the “INS Full Output Data” format is
limited to 100 Hz at standard COM-port baud rate 115200 bps. See Table
6.55 for maximum data rate at other baud rates.
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Table 6.11. The message payload at the “INS Full Output Data” format
Byte
number
0–1
2–3
Parameter Heading
Length
Note
2 byte
word
4–5
6 – 23
24 – 25 26 – 27 28 – 29 30 – 31 32 – 33
Pitch
Roll
Ugyro,
Uacc,
Umag
Reserved
2 byte
sword
2 byte
sword
Orientation angles,
deg*100
Mdec
USW
Vdd
2 byte 2 byte 2 byte 2 byte 2 byte
9 2 byte
word
word
sword
sword sword
sword
Combi- Temper
Raw sensor
ned ature in
data (gyros,
deg*100
voltage each
accelerometers,
sensor
magnetometers)
Table 6.11 (continued)
Byte
34 – 37
number
38 – 41
42 – 45
46 – 49
Altitude
East
or
Parameter Latitude Longitude
speed
Heave
4 byte
4 byte
4 byte
4 byte
Length
integer integer integer integer
deg
deg
Note
m*100 m/s*100
*1.0e7
*1.0e7
50 – 53
54 – 57
North
speed
Vertical
speed
4 byte
integer
4 byte
integer
m/s*100
m/s*100
Table 6.11 (continued)
Byte
58 – 61 62 – 65 66 – 69
number
Latitude Longitude Altitude
Parameter
GNSS
GNSS
GNSS
4 byte
4 byte
4 byte
Length
integer integer
integer
deg
deg
Note
m*100
*1.0e7
*1.0e7
70 – 73
74 – 75
Horizontal Track over
speed
ground
4 byte
2 byte
integer
word
m/s*100
76 – 79
Vertical
speed
4 byte
integer
deg*100 m/s*100
Table 6.11 (continued)
Byte
80 – 83
number
Parameter ms_gps
Length
Note
84
85
86
87-88
GNSS GNSS
#SolnSVs V_latency
_info1 _info2
4 byte
1 byte 1 byte
integer
ms
TM
Utermo
1 byte
2 byte
89-90 91-92
UP
UT
93
New
GPS
2 byte 2 byte
1 byte
word word
s*1000
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Notes
1. Mdec is magnetic declination (see section 1.3 for details), since INS firmware version
2.2.0.2.
2. USW is unit status word (see section 6.9 for details).
3. The following data are recorded in the field «Vdd» sequentially:
– the INS input voltage, Vinp, VDC*100;
– stabilized voltage supplied to the INS sensors, Vdd, VDC*1000;
4. In the «Utermo» field ADC codes are recorded sequentially from 7 temperature
sensors inside gyros, accelerometers and magnetometers.
5. ms_gps are milliseconds from the beginning of the GPS reference week;
6. TS_gps is time status which indicates the quality of the GPS reference time (see
Table 6.5);
7. GNSS_info contains information about GNSS data (see Table 6.6);
8. #SolnSVs is number of satellites used in navigation solution;
9. V_latency is latency in the velocity time tag in milliseconds;
10. Choice of altitude or heave and appropriate rate for output is supported in INS-D units
and depends on switch h_output (see section 6.5 for details).
11. UP and UT are raw data from the pressure sensor – pressure and temperature.
12. New_GPS is indicator of new update of GPS data;
13. The low byte is transmitted by first.
6.2.7. The “INS Sensors Data” format
This data format contains data from the devices inside INS:
AHRS (IMU) data:
3 orientation angles (heading, pitch and roll);
raw data from the 9 sensors (gyros, accelerometers, magnetometers) in
original ADC codes;
AHRS service data;
GNSS receiver data:
position – latitude, longitude, height above mean sea level;
standard deviations of latitude, longitude and height;
horizontal and vertical speed;
direction of motion (track over ground);
GPS reference time;
GPS service data;
Pressure sensor data:
temperature and pressure raw data in ADC codes.
Structure of the INS data blocks at the “INS Sensors Data” format
corresponds to the Table 6.2 with payload shown in the Table 6.12.
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Maximum data rate for the INS output at the “INS Sensors Data” format is
limited to 100 Hz at standard COM-port baud rate 115200 bps. See Table
6.55 for maximum data rate at other baud rates.
Table 6.12. The message payload at the “INS Sensors Data” format
Byte
number
0–1
2–3
4–5
6 – 23
24 – 25 26 – 27 28 – 29 30 – 31 32 – 33
Ugyro,
Reser- ReserUSW
Uacc,
ved
ved
Umag
2 byte 2 byte 2 byte
2 byte
2 byte 2 byte
9 2 byte
word
sword sword
sword sword word
sword
Raw sensor
data (gyros,
Orientation angles,
accelerometers,
deg*100
magnetometers)
Heading Pitch
Roll
Parameter
(AHRS) (AHRS) (AHRS)
Length
Note
Vdd
Utermo
2 byte 2 byte
word
sword
Combi- Temper
ature in
ned
voltage each
sensor
Table 6.12 (continued)
Byte
34 – 37 38 – 41
number
Latitude Longitude
Parameter
GNSS
GNSS
4 byte
4 byte
Length
integer integer
deg
deg
Note
*1.0e7 *1.0e7
42 – 45
46-47
48 – 49
50 – 51
52-55
56-57
Altitude Latitude Longitude Altitude Horizont Track over
GNSS
STD
STD
STD
al speed ground
4 byte 2 byte
2 byte
2 byte
4 byte
2 byte
integer word
word
word
integer
word
m*100 m*1000
m*1000
58-61
Vertical
speed
4 byte
integer
m*1000 m/s*100 deg*100 m/s*100
Table 6.12 (continued)
Byte
62 – 65
66
67
68
number
Parameter ms_gps TS_gps sol_stat pos_type
Length 4 byte 1 byte 1 byte 1 byte
Note
ms
69
70
71
72
#SVs #SolnSVs #SolnL1SVs #SolnMultiSVs
1 byte
1 byte
1 byte
1 byte
Table 6.12 (continued)
Byte
number
Parameter
Length
73
74
75
76-77
ext_sol_ Galileo and GPS and
V_latency
stat
BeiDou GLONASS
1 byte
1 byte
Note
1 byte
2 byte
78-79 80-81
UP
UT
82
83
New
Reserv
GPS
2 byte 2 byte
1 byte 1 byte
word word
s*1000
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Notes
1. USW is unit status word (see section 6.9 for details).
2. The following data are recorded in the field «Vdd» sequentially:
– the INS input voltage, Vinp, VDC*100;
– stabilized voltage supplied to the INS sensors, Vdd, VDC*1000;
3. In the «Utermo» field ADC codes are recorded sequentially from 7 temperature
sensors inside gyros, accelerometers and magnetometers.
4. ms_gps are milliseconds from the beginning of the GPS reference week;
5. TS_gps is time status which indicates the quality of the GPS reference time (see
Table 6.5);
6. sol_stat is GNSS solution status (see Table 6.13);
7. pos_type is GNSS position type (see Table 6.14);
8. #SVs is number of satellites tracked;
9. #SolnSVs is number of satellites used in navigation solution;
10. #SolnL1SVs is number of satellites with L1/E1/B1 signals used in solution;
11. #SolnMultiSVs is number of satellites with multi-frequency signals used in solution;
12. ext_sol_stat is GNSS extended solution status (see Table 6.15);
13. GPS and GLONASS is GPS and GLONASS signal-used mask (see Table 6.16);
14. Galileo and BeiDou is Galileo and BeiDou signal-used mask (see Table 6.17);
15. V_latency is latency in the velocity time tag in milliseconds;
16. Choice of altitude or heave and appropriate rate for output is supported in INS-D units
and depends on switch h_output (see section 6.5 for details).
17. UP and UT are raw data from the pressure sensor – pressure and temperature.
18. New_GPS is indicator of new update of GPS data;
19. The low byte is transmitted by first.
Table 6.13. sol_stat – GNSS solution status
Value
Description
0
Solution computed
1
Insufficient observations
2
No convergence
3
Singularity at parameters matrix
4
Covariance trace exceeds maximum (trace > 1000 m)
5
Test distance exceeded (maximum of 3 rejections if distance >10 km)
6
Not yet converged from cold start
7
Height or velocity limits exceeded (in accordance with export licensing
restrictions)
8
Variance exceeds limits
9
Residuals are too large
13
Large residuals make position unreliable
18
When a FIX POSITION command is entered, the receiver computes its own
position and determines if the fixed position is valid
19
The fixed position, entered using the FIX POSITION command, is not valid
20
Position type is unauthorized - HP or XP on a receiver not authorized
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Table 6.14. pos_type – GNSS position or velocity type
Value
Description
0
No solution
8
Velocity computed using instantaneous Doppler
16
Single point position
17
Pseudorange differential solution
18
Solution calculated using corrections from an WAAS
19
Propagated by a Kalman filter without new observations
20
OmniSTAR VBS position (1)
32
Floating L1 ambiguity solution
33
Floating ionospheric-free ambiguity solution
34
Floating narrow-lane ambiguity solution
48
Integer L1 ambiguity solution
50
Integer narrow-lane ambiguity solution
64
OmniSTAR HP position (1)
65
OmniSTAR XP or G2 position (1)
68
Converging PPP TerraStar-C solution (2)
69
Converged PPP TerraStar-C solution (2)
77
Converging PPP TerraStar-L solution (2)
78
Converged PPP TerraStar-L solution (2)
Notes
(1)
A subscription for OmniSTAR or use of a DGPS service is required. It is not realized in
the Inertial LabsTM INS firmware yet.
(2)
PPP solution requires access to a suitable correction stream, delivered either through LBand or the internet. For L-Band delivered TerraStar or Veripos service, appropriate
receiver software model is required, along with a subscription to the desired service. It
is not realized in the Inertial LabsTM INS firmware yet.
Bit
0
Mask
0x01
1-3
0x0E
4
5
0x10
0x20
6-7
0xC0
Table 6.15. ext_sol_stat – GNSS extended solution status
Description
If an RTK solution: NovAtel CORRECT solution has been verified
If a PDP solution: solution is GLIDE
Otherwise: Reserved
Pseudorange Iono Correction
0 = Unknown or default Klobuchar model
1 = Klobuchar Broadcast
2 = SBAS Broadcast
3 = Multi-frequency Computed
4 = PSRDiff Correction
5 = NovAtel Blended Iono Value
Reserved
0 = No antenna warning
1 = Antenna information is missing
Reserved
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Table 6.16. GPS and GLONASS signal-used mask
Bit
Mask
Description
0
0x01
GPS L1 used in solution
1
0x02
GPS L2 used in solution
2
0x04
GPS L5 used in solution
3
0x08
Reserved
4
0x10
GLONASS L1 used in solution
5
0x20
GLONASS L2 used in solution
6-7 0x40-0x80 Reserved
Table 6.17. Galileo and BeiDou signal-used mask
Bit
Mask
Description
0
0x01
Galileo E1 used in solution
1-3 0x02-0x08 Reserved
4
0x10
BeiDou B1 used in solution
5
0x20
BeiDou B2 used in solution
6-7 0x40-0x80 Reserved
6.2.8. The “INS Minimal Data” format
This data format specifies the minimum of the INS data that can be
transferred with larger data rate as 150 Hz.
3 orientation angles (heading, pitch and roll);
AHRS (IMU) service data;
position – latitude, longitude, altitude above mean sea level (or heave);
east, north and vertical velocity;
GPS reference time;
GPS service data.
Structure of the INS data blocks at the “INS Minimal Data” format
corresponds to the Table 6.2 with payload shown in the Table 6.18.
Note: before INS firmware version 2.2.1.0 other GNSS information were shown in byte
#40 – TS_gps. This information can be returned if uncheck “Extended info” checkbox in
INS Demo Program in “GNSS receiver” tab of “Devices options” menu item.
Maximum data rate for the INS output at the “INS Minimal Data” format is 200
Hz at standard COM-port baud rate 115200 bps. See Table 6.55 for
maximum data rate at other baud rates.
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Table 6.18. The message payload at the “INS Minimal Data” format
Byte
number
0–1
2–3 4–5 6–7
8–9
10 – 11 12 – 15
16 – 19
20 – 23
Altitude
or
Parameter Heading Pitch Roll USW Vinp Temper Latitude Longitude
Heave
4 byte
4 byte
2 byte 2 byte 2 byte 2 byte 2 byte 2 byte 4 byte
Length
word sword sword word word sword integer integer integer
Supply
voltage, Temper
Orientation angles,
deg
deg
m*100
Note
deg*100
VDC* ature, *1.0e7
*1.0e7
ºC*10
100
Table 6.18 (continued)
Byte
24 – 27 28 – 31 32 – 35 36-39
40
41
number
East
North Vertical
GNSS
Parameter
#SolnSVs
ms_gps
speed speed speed
_info1
4 byte 4 byte 4 byte 4 byte
Length
1 byte 1 byte
integer integer integer integer
Note m/s*100 m/s*100 m/s*100
Notes:
1. USW is unit status word (see section 6.9 for details).
2. Vinp is input voltage of the INS.
3. Temper is averaged temperature in 3 gyros.
4. ms_gps are milliseconds from the beginning of the GPS reference week;
5. GNSS_info1 contains information about GNSS data (see Table 6.5);
6. #SolnSVs is number of satellites used in navigation solution.
7. The low byte is transmitted by first.
6.2.9. The “INS NMEA Output” data format
At the “INS NMEA Output” the INS data are transmitted in the form of
sentences with printable ASCII characters like the NMEA 0183 format. Each
sentence starts with a "$" sign and ends with <CR><LF> (carriage return 0xD
and line feed 0xA symbols). All data fields are separated by commas. The
general form of the “INS NMEA Output” sentence is the next
$PAPR,LLmm.mmmm,n,YYYmm.mmmm,x,AAAA.aa,B,RRRR.rr,PPP.pp,
HHH.hh,ttttttttt,TTT.t,VV.v,SSSS*CC<CR><LF>
where PAPR is identifier and other fields are listed below:
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LLmm.mmmm is unsigned latitude, where LL are degrees, mm.mmmm are minutes;
n is N or S (North or South);
YYYmm.mmmm is unsigned longitude, where YYY are degrees, mm.mmmm are
minutes;
x is E or W (East or West);
AAAA.aa is altitude or heave in meters;
B denotes kind of height data that is defined by switch h_output (see section 6.5 for
details):
‘a’ – altitude;
‘h’ – heave.
RRRR.rr is roll in degrees;
PPP.pp is pitch in degrees;
HHH.hh is heading in degrees;
ttttttttt is timestamp (milliseconds from the beginning of the GPS reference week);
TTT.t is temperature inside INS (averaged value for 3 gyros);
VV.v is input voltage of the INS;
SSSS is unit status word, USW (see section 6.9 for details). It is hex written with
ASCII;
CC is check sum that consists of a "*" and two hex digits representing XOR of all
characters between, but not including "$" and "*".
Maximum data rate for the INS output at the “INS NMEA Output” data format
is limited to 100 Hz at standard COM-port baud rate 115200 bps. See Table
6.55 for maximum data rate at other baud rates.
6.2.10. The “INS Sensors NMEA Output” data format
The “INS Sensors NMEA output” data have structure close to the “INS
NMEA”, with addition of gyros and accelerometers data. So, at the “INS
Sensors NMEA output” the INS data are transmitted in the form of sentences
with printable ASCII characters like the NMEA 0183 format. Each sentence
starts with a "$" sign and ends with <CR><LF> (carriage return 0xD and line
feed 0xA symbols). All data fields are separated by commas. The general
form of the “INS Sensors NMEA output” sentence is the next
$PAPS,LLmm.mmmm,n,YYYmm.mmmm,x,AAAA.aa,B,RRRR.rr,PPP.pp,
HHH.hh,GGGG.xx,GGGG.yy,GGGG.zz,AA.xxxx,AA.yyyy,AA.zzzz,ttttttttt,
TTT.t,VV.v,SSSS*CC<CR><LF>
where PAPS is identifier and other fields are listed below:
LLmm.mmmm is unsigned latitude, where LL are degrees, mm.mmmm are minutes;
n is N or S (North or South);
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YYYmm.mmmm is unsigned longitude, where YYY are degrees, mm.mmmm are
minutes;
x is E or W (East or West);
AAAA.aa is altitude or heave in meters;
B denotes kind of height data that is defined by switch h_output (see section 6.5 for
details):
‘a’ – altitude;
‘h’ – heave.
RRRR.rr is roll in degrees;
PPP.pp is pitch in degrees;
HHH.hh is heading in degrees;
GGGG.xx is gyro X data in degrees/s;
GGGG.yy is gyro Y data in degrees/s;
GGGG.zz is gyro Z data in degrees/s;
AA.xxxx is accelerometer X data in g;
AA.yyyy is accelerometer Y data in g;
AA.zzzz is accelerometer Z data in g;
ttttttttt is timestamp (milliseconds from the beginning of the GPS reference week);
TTT.t is temperature inside INS in C (averaged value for 3 gyros);
VV.v is input voltage of the INS, in Volts;
SSSS is unit status word, USW (see Appendix C for details). It is hex written with
ASCII;
CC is check sum that consists of a "*" and two hex digits representing XOR of all
characters between, but not including "$" and "*".
Maximum data rate for the INS output at the “INS Sensors NMEA Output”
data format is limited to 80 Hz at standard COM-port baud rate 115200 bps.
See Table 6.55 for maximum data rate at other baud rates.
6.2.11. The “TSS1 Output” data format
At the “TSS1 Output” the INS provides accelerations, heave, pitch, and roll
message in the commonly used TSS1 message format. The TSS1 data string
consists of five data fields and contains 27 printable ASCII characters. The
acceleration fields contain ASCII-coded hexadecimal values. Motion
measurements include ASCII-coded decimal values. The general form of the
“TSS1” sentence is the next:
:XXAAAASMHHHHQMRRRRSMPPPP<CR><LF>
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Table 6.19.The INS message in TSS1 format
Message
Description
component
:
Start character
XX
Horizontal acceleration (hex value), in 3.83 cm/s², with a range of zero to
9.81 m/s²
AAAA
Vertical acceleration (hex value - 2’s complement), in 0.0625 cm/s², with a
range of –20.48 to +20.48 m/s²
S
Space character
M
Space if positive; minus if negative
HHHH
Heave, in centimeters, with a range of –99.99 to +99.99 meters
Q
Status flag
Value Description
F
INS Ready Mode with valid GPS input
H
AHRS Ready Mode without GPS input
M
Space if positive; minus if negative
RRRR
Roll, in units of 0.01 degrees (ex: 1000 = 10°), with a range of –99.99° to
+99.99°
S
Space character
M
Space if positive; minus if negative
PPPP
Pitch, in units of 0.01 degrees (ex: 1000 = 10°), with a range of –99.99° to
+99.99°
<CR>
Carriage return
<LF>
Line feed
Note: heave calculation is supported in INS-D units only, INS-B and INS-P units output
zero value for heave.
Maximum data rate for the INS output at the TSS1 data format is 200 Hz at
standard COM-port baud rate 115200 bps. See Table 6.55 for maximum data
rate at other baud rates.
6.2.12. The GNSS receiver NMEA data format (through COM2 port)
The Inertial LabsTM INS can use the second COM2 port for output the set of
GNSS receiver data in NMEA format. The INS starts output of these data
after power on and completing of the receiver initialization (when the INS
LED indicator switches from yellow to red).
NMEA data set is variable and can be changed by user using INS Demo
Program. NMEA data set can include next synchronous logs:
GPGGA,
GPGSA,
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GPRMC,
GPVTG,
GPZDA.
The data for synchronous logs are generated with set frequency (see section
6.4. Control of the GNSS receiver).
Data are transmitted in the form of sentences with printable ASCII characters
like the NMEA 0183 format. Each sentence starts with a "$" sign and ends
with <CR><LF> (carriage return 0xD and line feed 0xA symbols). All data
fields are separated by commas.
GPGGA log contains time, position and fix related data of the GNSS receiver.
The structure of the GPGGA log is next:
Table 6.20 The GPGAA log structure
Message
component
$GPGGA
utc
lat
lat dir
lon
lon dir
quality
# sats
hdop
alt
a-units
undulation
u-units
age
stn ID
*xx
[CR][LF]
Description
Log header
UTC time status of position (hours/minutes/seconds/
decimal seconds)
Latitude (DDmm.mm)
Latitude direction (N = North, S = South)
Longitude (DDDmm.mm)
Longitude direction (E = East, W = West)
GPS Quality Indicators (see Table 6.21)
Number of satellites in use. May be different to the
number in view
Horizontal dilution of precision
Antenna altitude above/below mean sea level
Units of antenna altitude (M = meters)
Undulation - the relationship between the geoid and the
WGS84 ellipsoid
Units of undulation (M = meters)
Age of correction data (in seconds)
Differential base station ID
Checksum
Sentence terminator
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Indicator
0
1
2
4
5
6
7
8
9
Table 6.21 GPS Quality Indicators
Description
Fix not available or invalid
Single point
Pseudorange differential
Unconverged OmniSTAR
HP/XP/G2/VBS converging PPP
RTK fixed ambiguity solution (RT2)
Operational
RTK floating ambiguity solution (RT20)
Converged OmniSTAR HP/XP/G2
Converged PPP
Dead reckoning mode
Manual input mode (fixed position)
Simulator mode
WAAS (SBAS)
GPGSA log contains GNSS receiver operating mode, satellites used for
navigation and DOP values. The structure of the GPVTG log is next:
Table 6.22 The GPGSA log structure
Message
component
$ GPGSA
mode MA
mode 123
prn
(fields 4-15)
pdop
hdop
vdop
*xx
[CR][LF]
Description
Log header
A = Automatic 2D/3D
M = Manual, forced to operate in 2D or 3D
Mode: 1 = Fix not available; 2 = 2D; 3 = 3D
PRN numbers of satellites used in solution (null for
unused fields), total of 12 fields
GPS = 1 to 32
SBAS = 33 to 64 (add 87 for PRN number)
GLO = 65 to 96
Position dilution of precision
Horizontal dilution of precision
Vertical dilution of precision
Checksum
Sentence terminator
GPRMC log contains time, position and fix related data of the GNSS receiver.
The structure of the GPRMC log is next:
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Table 6.23 The GPRMC log structure
Message
component
$ GPRMC
utc
pos status
lat
lat dir
lon
lon dir
speed Kn
track true
date
mag var
mode ind
*xx
[CR][LF]
Description
Log header
UTC time status of position (hours/minutes/seconds/
decimal seconds)
Position status:
A = data valid, V = data invalid
Latitude (DDmm.mm)
Latitude direction (N = North, S = South)
Longitude (DDDmm.mm)
Longitude direction (E = East, W = West)
Speed over ground, knots
Track made good, degrees True
Date: dd/mm/yy
Magnetic variation direction E/W
Positioning system mode indicator (see Table 6.25)
Checksum
Sentence terminator
GPVTG log contains the track made good and speed relative to the ground.
The structure of the GPVTG log is next:
Table 6.24 The GPVTG log structure
Message
component
$ GPVTG
track true
T
track mag
M
speed Kn
N
speed Km
K
mode ind
*xx
[CR][LF]
Description
Log header
Track made good, degrees True
True track indicator
Track made good, degrees Magnetic;
Track mag = Track true + (MAGVAR correction)
Magnetic track indicator
Speed over ground, knots
Nautical speed indicator (N = Knots)
Speed, kilometers/hour
Speed indicator (K = km/hr)
Positioning system mode indicator (see Table 6.25)
Checksum
Sentence terminator
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Table 6.25 NMEA Positioning System Mode Indicator
Mode
Indicator
A
Autonomous
D
Differential
E
Estimated (dead reckoning) mode
M
Manual input
N
Data not valid
GPZDA log outputs the UTC date and time. The structure of the GPZDA log
is next:
Table 6.26 The GPZDA log structure
Message
component
$ GPZDA
utc
day
month
year
null
7null
*xx
[CR][LF]
Description
Log header
UTC time status
Day, 01 to 31
Month, 01 to 12
Year
Local zone description—not available
Local zone minutes description—not available
Checksum
Sentence terminator
6.2.13. The GNSS receiver GPRMC data format (through COM3 port)
The Inertial LabsTM INS can use the third COM3 port for output the GNSS
receiver log GPRMC. To set GPRMC message for output through COM3 port
please use the INS Demo Program (see INS Demo User’s Manual section
“4.2.2 GNSS receiver tab of “Device options… ” window”).
The INS starts output of these data after power on and completing of the
receiver initialization (when the INS LED indicator switches from yellow to
red). The data for synchronous logs are generated with set frequency (see
section 6.4. Control of the GNSS receiver).
Data are transmitted in the form of sentences with printable ASCII characters
like the NMEA 0183 format. Each sentence starts with a "$" sign and ends
with <CR><LF> (carriage return 0xD and line feed 0xA symbols). All data
fields are separated by commas.
GPRMC log contains time, position and fix related data of the GNSS receiver.
See the structure of the GPRMC log in the Table 6.23.
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6.3. Control of the Inertial LabsTM INS
After power connection an initialisation of the onboard GNSS receiver starts
that takes about 15 seconds. During this initialization the INS’ LED indicator
(see Fig.5.1) lights yellow. After the initialization completed the LED indicator
switches to red, and the INS’ goes to the idle mode in which it is ready to
receive commands from the host computer.
When the INS switches from idle to any operation mode, the light indicator
changes its color from red to green.
The next commands are used to control the INS:
INS_OPVTdata;
INS_QPVTdata;
INS_OPVT2Adata;
INS_OPVT2Ahrdata;
INS_OPVT2AWhrdata;
INS_FullData;
INS_SensorsData;
INS_minData;
INS_NMEA;
INS_Sensors_NMEA;
INS_TSS1;
SetOnRequestMode;
Stop;
ReadINSpar;
LoadINSpar;
GetDevInfo;
GetBIT.
All these commands have the byte structure shown in the Table 6.2. Payload
for all commands has length 1 byte and contains code of the command. See
Appendix C for exact structure of these commands.
6.3.1. INS_OPVTdata,
INS_QPVTdata,
INS_OPVT2Adata,
INS_OPVT2AWdata,
INS_OPVT2Ahrdata,
INS_FullData,
INS_SensorsData, INS_minData, INS_NMEA, INS_Sensors_NMEA,
INS_TSS1 commands
Commands
INS_OPVTdata,
INS_QPVTdata,
INS_OPVT2Adata,
INS_OPVT2AWdata, INS_OPVT2Ahrdata, INS_FullData, INS_SensorsData,
INS_minData, INS_NMEA, INS_Sensors_NMEA, INS_TSS1 are used to start
the Inertial LabsTM INS in the “Continuous” operating mode with appropriate
variant of output data format as Table 6.27 shows.
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Table 6.27. INS control command and appropriate output data format
Command
INS_SensorsData
INS_FullData
INS_OPVTdata
INS_QPVTdata
INS_OPVT2Adata
INS_OPVT2AWdata
INS_OPVT2Ahrdata
INS_minData
INS_NMEA
INS_Sensors_NMEA
INS_TSS1
Code
0x50
0x51
0x52
0x56
0x57
0x59
0x58
0x53
0x54
0x55
0x35
Output data format
INS Sensors Data
INS Full Output Data
INS OPVT
INS QPVT
INS OPVT2A
INS OPVT2AW
INS OPVT2Ahr
INS Minimal Data
INS NMEA Output
INS and Sensors NMEA Output
TSS1 Output
All these commands have the byte structure shown in the Table 6.2. Payload
for all commands has length 1 byte and contains code of the command listed
in the Table 6.27.
In order to identify to the host system that INS received one of these
commands, the INS answers back immediately on this command prior to
completion of the initial alignment process. The INS calculates the check sum
of the message (without its header and check sum) and returns it for a
checking. Byte structure of this message is shown in the Table 6.2 where
payload is the calculated check sum (1 word). This check sum should be
equal to the check sum in the message that was sent to the INS.
After receiving of any from these commands the INS starts process of initial
alignment that takes usually 30 seconds. This process includes the INS gyros
bias estimation, therefore don’t move the INS during its initial alignment. If
this requirement is not met then large errors may be occurred in orientation
and position calculation.
Note: Default time 30 seconds of the initial alignment can be changed (see section 6.3.4.
LoadINSpar command) but only in agreement with developers of the Inertial LabsTM INS.
After completing of the initial alignment the INS gives out message with block
of the initial alignment data (see Table 6.28, Table 6.29) and goes to the
“Continuous” operating mode.
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Table 6.28. Byte structure of the block of initial alignment data
Byte
number
Parameter
Length
Note
0
1
2
3
Header
0
1 byte
Header
1
1 byte
Message
type
1 byte
0xAA
0x55
0x01
4, 5
6..55
56, 57
Check
Output data Message
Payload
sum
rate (Hz)
length
1 byte
1 word
50 bytes 1 word
hexadecimal
0x38
see
value
0x00
Table 6.21
Table 6.29. Structure of the payload of the block of initial alignment data
Byte
0-11
12-23
24-35
36-39
40-43
44-47
48-49
Parameter
Gyros bias
Average acceleration
Average magn. field
Initial Heading
Initial Roll
Initial Pitch
USW
(see section 6.9)
Format
float
float
float
float
float
float
word
Length
3*4
3*4
3*4
4
4
4
2
Note
3 numbers in ADC codes
3 numbers in ADC codes
3 numbers in ADC codes
degrees
degrees
degrees
0 – successful initial
alignment;
0 – unsuccessful
In the “Continuous” operating mode set by any of above commands
INS_OPVTdata, INS_QPVTdata, INS_OPVT2Adata, INS_OPVT2AWdata,
INS_OPVT2Ahrdata,, INS_FullData, INS_SensorsData, INS_minData,
INS_NMEA, INS_Sensors_NMEA, INS_TSS1, the program in the INS
microprocessor operates in the endless loop, providing the process of data
reading from ADC and calculation of position and orientation.
At
the
INS_OPVTdata,
INS_QPVTdata,
INS_OPVT2Adata,
INS_OPVT2AWdata,
INS_OPVT2Ahrdata,
INS_FullData,
INS_SensorsData, INS_minData commands output data blocks have binary
structure described in the Table 6.2 with payload depending on chosen
variant of output data format (see matching Table 6.27 and more detailed
Tables 6.4, 6.7, 6.8, 6.9, 6.10, 6.11, 6.12 and 6.18).
Note: For better identification of data format of the INS output blocks, since the INS
firmware version 2.1.2.0 the INS data identifier is present in the data block structure (see
Table 6.2, byte #3) which is equal to appropriate command code and corresponds to data
format according to the Table 6.27.
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At the INS_NMEA, INS_Sensors_NMEA, INS_TSS1 commands output data
blocks are transmitted in the form of sentences with printable ASCII
characters as sections 6.2.9 – 6.2.11 describe.
The update rate of data blocks is set by the user in range (1...200) Hz, but
maximum data rate depends on chosen output data format and COM port
baud rate (see Table 6.55).
6.3.2. SetOnRequestMode command – getting INS data on request (on
demand)
The command SetOnRequestMode is used to start the Inertial LabsTM INS
operation in the “On Request” (on demand) operating mode. This command
has the byte structure shown in the Table 6.2 where payload is one byte
equal to 0xC1.
In order to identify to the host system that INS received this command, the
INS answers back immediately on this command prior to completion of the
initial alignment process. The INS calculates the check sum of the message
(without its header and check sum) and returns it for a checking. Byte
structure of this message is shown in the Table 6.2 where payload is the
calculated check sum (1 word). This check sum should be equal to the check
sum in the message that was sent to the INS.
After receiving of the SetOnRequestMode command the INS starts process
of initial alignment that takes usually 30 seconds. This process includes the
INS gyros bias estimation, therefore don’t move the INS during its initial
alignment. If this requirement is not met then large errors may be occurred in
orientation angles calculation.
Note: Default time 30 seconds of the initial alignment can be changed (see section 6.3.4.
LoadINSpar command) but only in agreement with developers of the Inertial LabsTM INS.
After completing of the initial alignment the INS gives out message with block
of the initial data (payload is 50 bytes of the data – see the Table 6.28, Table
6.29) and goes to the “On Request” operating mode.
In the “On Request” operating mode the INS sends only one data block after
each request. To get this data block send one of above described commands
INS_OPVTdata, INS_QPVTdata, INS_OPVT2Adata, INS_OPVT2AWdata,
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INS_OPVT2Ahrdata,,
INS_FullData,
INS_minData,
INS_NMEA,
INS_Sensors_NMEA, INS_TSS1 (see section 6.3.1). Note INS_SensorsData
command is not supported in the “On Request” operating mode since the INS
firmware version 2.1.1.0.
If one of the INS_OPVTdata, INS_QPVTdata, INS_OPVT2Adata,
INS_OPVT2AWdata, INS_OPVT2Ahrdata, INS_FullData, INS_minData
commands is used for request then output data block has binary structure
described in the Table 6.2 with payload depending on chosen variant of
output data format (see matching Table 6.19 and more detailed Tables 6.4,
6.7, 6.8, 6.9, 6.10, 6.11, 6.12 and 6.18).
Note: For better identification of data format of the INS output blocks, since the INS
firmware 2.1.2.0 the INS data identifier is present in the data block structure (see Table
6.2, byte #3) which is equal to appropriate command code and corresponds to data format
according to the Table 6.20.
If one of the INS_NMEA, INS_Sensors_NMEA, INS_TSS1 commands is
used for request then output data block contains printable ASCII characters
as sections 6.2.9 – 6.2.11 describe.
Important note: for right use the INS_TSS1 command for request it is necessary to set
switch h_output=2 to allow heave calculation (see section “6.5. Altitude and Heave
calculation” for details). Otherwise INS answer on the INS_TSS1 command will contain all
zeros in TSS1 data block.
6.3.3. Stop command
At receiving the Stop command (code 0xFE in the “Payload” field) the INS
stops work in an operating mode and goes to the idle mode. At that the INS
LED indicator changes its color to red. The INS is ready to receive any
command from the host computer.
Important Note: Before using all other commands please send the Stop command to the
INS to switch device into the idle mode. Be sure that the INS’s light indicator is red before
sending of any other commands.
6.3.4. LoadINSpar command
The LoadINSpar command (code 0x40 in the “Payload” field) is used to load
the block of the INS parameters (which are available for changing by user)
into the INS nonvolatile memory. After sending the LoadINSpar command,
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the block of the INS parameters must be send to the INS in the message
shown in the Table 6.2 with payload shown in the Table 6.30. This message
should be sent without pause after sending the LoadINSpar command.
Table 6.30. Payload of the message following after the LoadINSpar command (block
of parameters for loading to the INS)
Byte
0-1
2-3
4-7
Parameter
Data rate
Initial alignment time
Magnetic declination,
Mdec
Format
word
word
longint
Length
2
2
4
8-11
12-15
16-19
20
21
22
23-24
25-26
27-28
29-30
31-32
33-34
35-36
37-38
39-40
41
Latitude
Longitude
Altitude
Date (Year from 2000)
Date (Month)
Date (Day)
Alignment angle A1
Alignment angle A2
Alignment angle A3
INS mount, right
INS mount, forward
INS mount, up
Antenna pos., right
Antenna pos., forward
Antenna pos., up
Altitude or Heave output,
h_output
Cutoff frequency
for Heave HP filter
Cutoff frequency
for Heave LP filter
longint
longint
longint
byte
byte
byte
sword
sword
sword
sword
sword
sword
sword
sword
sword
byte
4
4
4
1
1
1
2
2
2
2
2
2
2
2
2
1
byte
1
byte
1
Target position, right
Target position, forward
Target position, up
INS device name
Baro_enabled
Reserved
sword
sword
sword
char
byte
byte
2
2
2
8
1
1
42
43
44-45
46-47
48-49
50-57
58
59
Note
Hz
seconds
degrees*100,
if Mdec > 360 then INS
calculates it
degrees*1e7
degrees*1e7
meters*100
0 to 255
1 to 12
1 to 31
Angles of INS mounting on the
carrier object, degrees*100
(see Appendix B)
INS mounting lever relative to
the object center of gravity,
m*100 (see section 6.6)
GNSS antenna mounting
lever relative to the INS,
meters*100
1 = Altitude
2 = Heave (see section 6.5)
Hz*100
(see section 6.5.1)
Hz*10, must be not less than
cutoff frequency for Heave
HP filter, or zero
Target position relative to the
INS for Heave calculation,
lever, m*100
only read, change is ignored
0 = disabled; 1 = enabled
The INS calculates the check sum of received parameters and returns it for a
checking. Byte structure of this message is shown in the Table 6.2 where
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payload is the calculated check sum (2 bytes).
Notes:
1. The most easy and sure way to change above parameters is using the Inertial LabsTM
INS Demo Program.
2. Before using LoadINSpar command it is necessary to use ReadINSpar command (see
below) to read parameters from the INS at first. After that user can change some
parameters listed in the Table 6.30, and to send back all block of parameters to the Inertial
LabsTM INS.
3. Default time 30 seconds of the initial alignment can be changed but only in agreement
with developers of the Inertial LabsTM INS.
4. It is necessary to set current latitude, longitude and altitude for setting the initial position
in case of the GNSS data may be not available at the INS start.
5. It is necessary to set current latitude, longitude, altitude, year, month, day before
hard/soft iron calibration of the INS magnetometers (see section 6.7).
6. Baro_enabled switch enables or disables using of the pressure sensor data for the INS
altitude correction. On default it is enabled. See section 6.5 for details.
6.3.5. ReadINSpar command
The ReadINSpar command (code 0x41 in the “Payload” field, see the Table
6.2) is used to read block of the Inertial LabsTM INS parameters (60 bytes)
from the INS nonvolatile memory.
After receiving ReadINSpar command, the INS sends out the message with
structure according to Table 6.2 and payload shown in the Table 6.31.
Table 6.31. Payload of the INS answer on the ReadINSpar command
(block of parameters read from the INS)
Byte
0-1
2-3
4-7
8-11
12-15
16-19
20
21
22
23-24
25-26
27-28
Parameter
Data rate
Initial alignment time
Magnetic declination,
Mdec
Latitude
Longitude
Altitude
Date (Year from 2000)
Date (Month)
Date (Day)
Alignment angle A1
Alignment angle A2
Alignment angle A3
TM
Format
word
word
longint
Length
2
2
4
Note
Hz
seconds
degrees*100
longint
longint
longint
byte
byte
byte
sword
sword
sword
4
4
4
1
1
1
2
2
2
degrees*1e7
degrees*1e7
meters*100
0 to 255
1 to 12
1 to 31
Angles of INS mounting on the
carrier object, degrees*100
(see Appendix B)
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29-30
31-32
33-34
35-36
37-38
39-40
41
42
43
44-45
46-47
48-49
50-57
58
59
INS mount, right
INS mount, forward
INS mount, up
Antenna pos., right
Antenna pos., forward
Antenna pos., up
Altitude or Heave output,
h_output
Cutoff frequency
for Heave HP filter
Cutoff frequency
for Heave LP filter
sword
sword
sword
sword
sword
sword
byte
2
2
2
2
2
2
1
byte
1
byte
1
Target position, right
Target position, forward
Target position, up
INS device name
Baro_enabled
Reserved
sword
sword
sword
char
byte
byte
2
2
2
8
1
1
INS mounting lever relative to
the object center of gravity,
m*100 (see section 6.6)
GNSS antenna mounting
lever relative to the INS,
meters*100
1 = Altitude
2 = Heave (see section 6.5)
Hz*100
(see section 6.5.1)
Hz*10, must be not less than
cutoff frequency for Heave
HP filter, or zero
Target position relative to the
INS for Heave calculation,
lever, m*100
0 = disabled; 1 = enabled
See Notes to the section 6.3.4. LoadINSpar command.
6.3.6. GetDevInfo command
The GetDevInfo command (code 0x12 in the “Payload” field) is used to get
detailed information about devices installed in the INS:
1) INS processor;
2) IMU (AHRS);
3) GNSS receiver;
4) Pressure sensor.
As answer the INS sends out the message with structure according to the
Table 6.2 and payload shown in the Table 6.32.
Table 6.32. Payload of the INS answer on the GetDevInfo command
Byte
0-7
8-47
48
Parameter
ID_sn
ID_fw
Press_Sens
Format
char
char
byte
Length
8
40
1
49
50-57
IMU_type
IMU_sn
byte
char
1
8
TM
Note
Integrated device (INS) s/n
INS firmware version
Pressure sensor: 0 = absent,
1= Type1, 2= Type2
IMU type (1=AHRS)
IMU (AHRS) s/n
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58-97
98-113
114-129
130-145
146-161
162-163
164
165
IMU_fw
GNSS_model
GNSS_sn
GNSS_hw
GNSS_fw
GPS_week
GNSS_data_rate
Reserved
char
char
char
char
char
word
byte
byte
40
16
16
16
16
2
1
1
IMU (AHRS) firmware version
GNSS receiver model
GNSS receiver product s/n
GNSS receiver hardware version
GNSS receiver firmware version
GPS reference week number
GNSS receiver max data rate, Hz
Reserved
6.3.7. GetBIT command
The Inertial LabsTM INS has continuous built-in monitoring of its health. In
both “Continuous” and “On Request” operation modes the INS sends out the
Unit Status Word (USW) in each data block (see Table 6.4, 6.7, 6.8, 6.9,
6.10, 6.11, 6.12 and 6.18). The USW is described in the section 6.9.
The USW can be got in any time if the INS is in Idle or “On Request”
operation mode (after SetOnRequestMode command). For this the GetBIT
command (code 0x1A in the “Payload” field) is used. In answer the INS
sends out the message with data according to the Table 6.33.
Table 6.33. Payload of the INS answer on the GetBIT command
Byte number
0–1
2–3
Parameter
Utermo100
USW
Length
2 byte word
2 byte word
In the Table 6.33 Utermo100 is the INS temperature in 1/100 °C increments.
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6.4. Control of the GNSS receiver
6.4.1. GNSS receiver parameters
User can get information about the GNSS receiver model, serial number,
firmware version and data rate using GetDevInfo command (see section
6.3.6).
Setting of the GNSS receiver parameters is available for INS firmware
version since 2.0.1.2 and is performed by the Inertial LabsTM INS Demo
Program – see User’s Manual, section “10.2. Control of the GNSS receiver”
for details. There are the next parameters that can be changed:
COM2_data – allows to choose GNSS data set for output through COM
port 2 (see Table 6.34)
Table 6.34 COM2_data values
COM2_data value
0
1
2
Data set
No data
Raw GNSS
NMEA GGA, VTG, ZDA
NMEA_set – allows to set needed NMEA messages for output through
COM port 2 (see Table 6.35):
Table 6.35 NMEA_set value
Bit
0
Parameter
GPGGA
1
GPGSA
2
GPRMC
3
GPVTG
4
GPZDA
5
6
7
Reserved
Reserved
Reserved
TM
Description
0 – unset
1 – set
0 – unset
1 – set
0 – unset
1 – set
0 – unset
1 – set
0 – unset
1 – set
–
–
–
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By default INS outputs GPGGA, GPVTG and GPZDA messages if
COM2_data value is set to 2 (see Table 6.34).
GNSS_raw_data_frq – allows to output GNSS data with specified
frequency (see Table 6.36).
Table 6.36. GNSS_raw_data_frq values
GNSS_raw_data_frq value
0
1
2
3
4
5
6
Frequency, Hz
No raw data
1
2
4
5
10
20
GNSS_com2_bps – sets baud rate of COM2 which outputs GNSS
data (see Table 6.37).
Table 6.37. GNSS_com2_bps values
GNSS_com2_bps value
0
1
2
3
Baud rate, bps
115200
230400
460800
921600
GNSS_corr_type – specifies type of GNSS correction which should be
used. (see Table 6.38):
- No correction – no GNSS corrections will be used;
- AUTO – both SBAS and DGPS correction data will be used;
- SBAS – correction data from Satellite Based Augmentation
Systems (SBAS) will be used;
- DGPS – transmitted from a base station Differential GPS (DGPS)
correction data will be used.
Default value is “AUTO” (GNSS_corr_type=1).
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Table 6.38. GNSS_corr_type values
GNSS_corr_type value
Type of correction
0
1
2
3
No correction
AUTO
SBAS
DGPS
SBAScontrol – specifies type of SBAS correction (see Table 6.39).
Default value is “Auto SBAS” (SBAScontrol=1);
Table 6.39. SBAScontrol values
SBAScontrol value
0
1
2
3
4
5
6
7
Type of SBAS correction
No SBAS
AUTO
ANY
WAAS
EGNOS
MSAS
GAGAN
QZSS
GNSS_corr_format – specifies format of differential correction data
(see Table 6.40). Default value is “Auto” (GNSS_corr_format=0);
Table 6.40. GNSS_corr_format values
GNSS_corr_format value
0
1
2
Type of format
AUTO
RTCM
RTCMV3
GNSS_com3_bps – sets baud rate of COM3 which provides input of
the GNSS corrections (see Table 6.41).
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Table 6.41. GNSS_com3_bps values
GNSS_com3_bps value
0
1
2
3
4
5
Baud rate, bps
9600
14400
19200
38400
57600
115200
Note: COM3 port can be used for input of the GNSS corrections only if GPRMC
parameter is set to zero (see below).
GPRMC – allows to output $GPRMC log with the recommended
minimum navigation data provided by the GNSS receiver through
COM3 port with specified frequency (see Table 6.42). Default value is
“No” (GPRMC =0).
Table 6.42. GPRMC values
GPRMC value
0
1
2
3
4
5
6
Frequency, Hz
No GPRMC data
1
2
4
5
10
20
Note: If GPRMC parameter is set to nonzero value then COM3 port can’t be used for input
of the GNSS corrections.
PPS_switch – allows to output PPS signal (see Table 6.43). Default
value is “Enabled” (PPS_switch =0).
Table 6.43 PPS_switch values
PPS_switch value
0
1
TM
Enabled or disabled
Enabled
Disabled
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PPS_polarity – specifies polarity of the PPS pulse (see section “5.3.
PPS description”). Table 6.44 shows available values of the
PPS_polarity parameter. Default value is “Negative” (PPS_polarity =0).
Table 6.44. PPS_polarity values
PPS_polarity value
Polarity
0
1
Negative
Positive
PPS_period – sets period of the pulse in seconds (see Table 6.45).
Default value is “1.0” (PPS_period =6).
Table 6.45. PPS_period values
PPS_period value
Period, sec
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
1.0
0.05
0.1
0.2
0.25
0.5
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
16.0
17.0
18.0
19.0
20.0
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PPS_pulse_width – sets pulse width of the PPS signal in
microseconds. Default value is PPS_pulse_width =1000.
MARK_switch – allows to control the processing of the mark input
signal through GPIO pin of the main INS connector (see section “5.4.
GPIO description). Table 6.46 shows the MARK_switch values. Default
value is “Disabled” (MARK_switch =0);
Table 6.46. MARK_switch values
MARK_switch value
Mark signal processing
0
1
Disabled
Enabled
MARK_polarity – specifies polarity of the pulse at a mark input (see
Table 6.47). Default value is “Negative” (MARK_polarity =0);
Table 6.47. MARK_polarity values
MARK_polarity value
Polarity
0
1
Negative
Positive
MARK_timebias – sets an offset, in nanoseconds, to be applied to the
time the mark input pulse occurs. Default value is MARK_timebias =0;
MARK_timeguard – sets a time period, in milliseconds, during which
subsequent pulses after an initial pulse are ignored. Default value is
MARK_timeguard =4, minimum value is MARK_timeguard =2.
Important note: It is necessary to power off / on the INS after changing any of GNSS
receiver parameters to restart the GNSS receiver with new settings.
6.4.2. Control of GNSS receiver model
The Inertial LabsTM INS contains the NovAtel GNSS receiver inside. NovAtel
uses the term “models” to refer to and control different levels of functionality
in the GNSS receiver firmware. For example, user can purchase INS with the
base model of the GNSS receiver which has an L1 only capability. At a later
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time he can easy upgrade this receiver to a more feature intensive model,
like L1/L2 dual-frequency. All that is required to upgrade is an authorization
code for the higher model and the INS Demo Program to enter this code to
the receiver. Reloading of the INS or GNSS receiver firmware or returning the
INS for service to upgrade the model is not required.
See
http://www.novatel.com/assets/Documents/Papers/NovAtelModels.pdf
for information about available models for OEM615 NovAtel GNSS receiver.
User can perform next options by using INS Demo Program:
add new model to the GNSS receiver
choose one of saved models
remove model from the GNSS receiver
See section “10.2.2. Control of GNSS receiver model” in the INS Demo
Program User’s Manual.
6.5. Altitude and Heave calculation
At its operation the Inertial LabsTM INS calculates position using its sensors
data with correction from the onboard GNSS receiver. Also, for altitude
calculation the INS can use correction from the onboard pressure sensor.
In practice the GNSS altitude data are much less accurate than the horizontal
position (because of high vertical dilution of precision). Using a static
pressure sensor (barometer), as an aiding sensor for the altitude, increases
the vertical accuracy. Though the relation between altitude and pressure is
dependent on many factors, the most important is the “weather”.
The Inertial LabsTM INS allows two variants of the altitude correction that
depends on the Baro_enabled switch:
a) correction by altitude and vertical velocity provided by GNSS data
(Baro_enabled=0);
b) correction by barometric altitude calculated using pressure sensor data
and vertical velocity provided by GNSS data (Baro_enabled=1).
The default value is Baro_enabled=1. User can change this value using the
LoadINSpar command (see Table 6.30, byte #58) or using the INS Demo
Program (that is more easy).
Important note: To measure barometric altitude the pressure sensor in the INS must
have access to the ambient external pressure. Also the pressure sensor must not be
exposed to high speed air streams. So if the INS is installed inside a pressurized cabin or
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outside the high-speed object, please set Baro_enabled=0 to switch to the GNSS altitude
for INS correction.
Note in both variants of the INS altitude correction, the initial altitude is equal
to altitude provided by the GNSS receiver if it has solution. If GNSS data are
not available then the initial altitude is equal to its value stored in the INS
nonvolatile memory. There initial altitude can be changed using the
LoadINSpar command (see Table 6.30, bytes #16-19) or using the INS Demo
Program (that is more easy)
Also the INS-D can calculate heave for marine applications. Heave is a ship
motion along the vertical axis.
The h_output switch set what INS-D data are output:
1 – altitude;
2 – heave.
Value of the h_output switch can be stored using the LoadINSpar command
(see Table 6.30, byte #41) or using the INS Demo Program (that is more
easy).
Notes:
1. Inertial LabsTM INS-B and INS-P units do not calculate heave, so setting the h_output=2
switch will cause zero output.
2. Heave calculation also can use data from the pressure sensor (at Baro_enabled=1). In
that case the pressure sensor in the INS must have access to the ambient external
pressure, and the pressure sensor must not be exposed to high speed air streams.
6.5.1. Adjustment of the algorithm of heave calculation in INS-D
To calculate the heave as the INS-D vertical position with respect to its
equilibrium position, the vertical acceleration is doubly integrated. However,
because signals from accelerometers always contain a DC component as
well as spurious low frequency components, after integration the heave error
is accumulated and increases with time significantly. To avoid such error,
integrated signals are filtered by High-Pass (HP) filter. Also, to decrease
noise the Low-Pass (LP) filter can be applied.
One of the main adjustment parameters is cutoff frequency for heave HP
filter, fh_HP. It must be much less than the main frequency of a ship vertical
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motion. But very low value of the fh_HP allow accelerometers’ bias instability
to affect the heave accuracy. The default value is fh_HP = 0.02 Hz that
should be enough for intensive vertical motion of a ship.
Values of HP and LP cutoff frequencies for the heave filter can be set using
the LoadINSpar command (see Table 6.30, bytes #42 and 43) or using the
INS Demo Program (that is more easy).
Power_fft_min – the threshold of fast Fourier transform (FFT) spectrum
power at which the lead-lag filter parameters are recalculated. F_fft
paremeter sets the frequency of the FFT usage for lead-lag filter parameters
recalculation. The default values are Power_fft_min = 40 and F_fft = 0.04.
Values of Power_fft_min and F_fft for the heave filter can be set using the
INS Demo Program – see INS Demo Program User’s Manual, section
“10.3.1. Adjustment of the algorithm of heave calculation”.
Note. initialization of the adaptive algorithm of heave calculation takes
approximately 100 seconds. During this initialization heave is calculated
roughly.
6.5.2. Heave calculation for chosen point of the carrier object
Usually heave is calculated for place of the INS mounting on the carrier
object. But it is possible to set desirable point on the carrier object for heave
calculation. For this purpose please set coordinates of this point relative to
the INS-D position, in the object axes – on the right, forward and up. For this
please use the LoadINSpar command (see Table 6.30, bytes #44-49) or the
INS Demo Program (that is more easy).
6.6. Acceleration compensation at object swaying
It is possible to increase the INS orientation accuracy at the carrier object
swaying if to compensate linear acceleration at place of the INS mounting.
For this purpose please set coordinates of the INS mounting relative to the
center of the object swaying (usually this is object center of gravity).
These coordinates are set in meters in such sequence of the object
directions: right, forward, up. For this please use the LoadINSpar command
(see Table 6.30, bytes #29-34) or the INS Demo Program (that is more easy).
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6.7. Calibration of the Inertial LabsTM INS on hard and soft iron
The Inertial LabsTM INS software allows compensation of hard and soft iron
effects of the carrier object on the heading determination accuracy. For this
purpose, field calibration of the INS magnetometers is provided (see
Appendix A, The INS calibration). Inertial Labs utilizes several types of field
calibration depending on the carrier object type.
Note INS does not require calibration of its magnetometers on hard/soft
iron if “Use_mags” switch is disabled in the “Settings” tab of
«Correction options…» window of the INS Demo Program.
The next types of the calibration are realized in the Inertial LabsTM INS
firmware:
3D calibration;
2D-2T calibration;
2D calibration;
VG3D calibration (since firmware version 2.6.2.2);
on-the-fly VG3D calibration (since firmware version 2.6.2.2).
The next commands are used for the INS calibration:
Start lbRun;
Stop lbRun;
FinishClb;
AcceptClb;
Start3DClb;
StartVG3DClb;
Start2D2TClb;
Start2DClb;
ClearClb;
ExitClb;
GetClbRes;
StartVG3Dclb_flight;
StopVG3Dclb_flight.
All these commands have the byte structure shown in the Table 6.2. Payload
for all commands has length 1 byte and contains code of the command. See
Appendix C for examples of these commands.
6.7.1. Start3DClb command for INS 3D calibration
The 3D calibration is designed for carrier objects that can operate in full
heading, pitch and roll ranges. At this calibration the carrier object should be
rotated in all these ranges.
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To start the 3D calibration the host computer sends to the INS the Start3DClb
command (code 0x23 in the “Payload” field) followed by message with block
of parameters listed in the Table 6.48. This message have the byte structure
shown in the Table 6.2, and should be sent without pause after sending the
Start3DClb command.
Table 6.48. Payload of the message following after the Start3DClb, StartVG3DClb,
Start2D2TClb and Start2DClb commands (the block of parameters loaded to the INS)
Byte
0-3
4-5
6-9
10-13
14-17
18-21
Parameter
Format
byte
Reserved
Time of data accumu- word
lation in one run
float
Latitude
float
Longitude
float
Altitude
Date (Year, Month, Day) float
Length
4
2
Note
4
4
4
4
Degrees
Degrees
Meters
Year + (Month -1)/12 + Day/365
Seconds
The INS calculates the check sum of received parameters and returns it for a
checking. Byte structure of this message is shown in the Table 6.2 where
payload is the calculated check sum (1 word).
Then the INS starts process of initial alignment. This process includes the
INS gyros bias estimation, therefore don’t move the INS during its initial
alignment. Default time of the initial alignment is 30 seconds and can be
changed (see section 6.3.4. LoadINSpar command) but only in agreement
with developers of the Inertial LabsTM INS.
After completing of the initial alignment the INS gives out the block of the
initial alignment data (see the Table 6.28, Table 6.29) and starts data
accumulation during time specified in message sent after the Start3DClb
command (see the Table 6.48).
During the INS data accumulation the object should be rotated in full azimuth,
pitch and roll ranges. For example the object is rotated in the horizon plane
(the Z-axis is up) with periodical stops about each 90 degrees for tilting in
pitch and roll. After full 360 rotation the object with the INS is turned over
(the Z-axis is down) and the procedure described above should be repeated.
During this calibration the range of pitch and roll angles changing must be as
much as possible.
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Note: there is estimation of 3D calibration quality in terms of possible INS heading
accuracy. To allow this possibility it is necessary to include additional rotation of the INS
with the carrier object in the horizon plane on about 360 degrees or more with pitch and
roll near the level. Acceptable pitch and roll change can be set using INS Demo Software
by the “Pitch/Roll threshold” parameter in the “Device Options”.
After set accumulation time is reached or StopClbRun command is sent to
the INS (see section 6.7.2 for details) the INS finishes data accumulation and
calculates the calibration parameters.
After calculation of the calibration parameters that takes <0.5 seconds, the
INS gives out message with the calibration results (see the Table 6.49) and it
waits one of the next commands:
the AcceptClb command (see section 6.7.3) to accept and save the
calibration parameters (usually if the “Calibration success” byte in the INS
message is nonzero and corresponds to satisfactory INS heading
accuracy (see the Table 6.49 and Note below it));
or the ExitClb command (see section 6.7.4 to exit from calibration
procedure without accepting and saving its results (usually if the
“Calibration success” byte in the INS message is equal to 0 or
corresponds to not satisfactory INS heading accuracy (see the Table 6.49
and Note below it)).
The INS answers on these commands with checksum and goes to idle mode.
Table 6.49. Payload of the INS message after calibration completed
Byte
0
Parameter
Type of calibration
1
Number of used calibration
runs
Percent of used data
points
Calibration success
byte
1
byte
1
for 2D and 3D calibrations only
byte
1
Matrix for soft iron
correction
float
9*4
0 – calibration is not successful
>0 – calibration is successful
(see Note below)
Matrix Tm_c (3 3) by rows
2
3
4-39
TM
Format Length
byte
1
Note
1 for 2D calibration;
2 for 2D-2T calibration;
3 for 3D calibration;
5 for VG3D calibration
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39-51 Matrix for hard iron
correction
float
3*4
Matrix Hm_0 (3 1)
Note: there is estimation of the calibration quality as predicted INS heading accuracy. So
nonzero value of byte #3 “Calibration success” is predicted maximum (3 sigma) heading
error of the INS after calibration, in degrees*10. For example, byte #3 equal to 5
corresponds to the INS accuracy ±0.5 deg. If calibration is successful but INS cannot
estimate predicted accuracy it returns byte #3 equal to 255.
6.7.2. Stop lbRun command
After receiving the Stop lbRun command (code 0x20 in the “Payload” field)
the INS early stops data accumulation in the calibration run before set
accumulation time is reached.
Then the calibration procedure continues in the same way as after set
accumulation time was reached.
6.7.3. AcceptClb command
The AcceptClb command (code 0x2E in the “Payload” field) is applied to
accept the calibration parameters and to save them to the INS nonvolatile
memory. This command can be used in the end of the calibration procedure.
The INS answers on this command. The INS calculates the check sum of the
message (without its header and check sum) and returns it for a checking.
Byte structure of this message is shown in the Table 6.2 where payload is the
calculated check sum (1 word).
6.7.4. ExitClb command
The ExitClb command (code 0xFE in the “Payload” field) is used to exit from
the calibration without any calculations in the INS and without saving any
calibration parameters. The INS stops work in operating mode and goes into
the idle mode.
The INS answers on this command. The INS calculates the check sum of the
message (without its header and check sum) and returns it for a checking.
Byte structure of this message is shown in the Table 6.2 where payload is the
calculated check sum (1 word).
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6.7.5. StartVG3DClb command for INS VG3D calibration
Since firmware version 2.6.2.2 the INS provides VG3D calibration. The
VG3D calibration is designed for carrier objects that can operate in full
heading, pitch and roll ranges. VG3D calibration is similar to 3D calibration
but allows performing simpler rotation than is necessary for 3D calibration.
Note: VG3D calibration is at the testing stage. Please contact Inertial Labs about the
possibility of using the VG3D calibration.
To start the VG3D calibration the host computer sends to the INS the
StartVG3DClb command (code 0x25 in the “Payload” field) followed by
message with block of parameters listed in the Table 6.48. This message
have the byte structure shown in the Table 6.2, and should be sent without
pause after sending the StartVG3DClb command.
The INS calculates the check sum of received parameters and returns it for a
checking. Byte structure of this message is shown in the Table 6.2 where
payload is the calculated check sum (1 word).
Then the INS starts process of initial alignment. This process includes the
INS gyros bias estimation, therefore don’t move the INS during its initial
alignment. Default time of the initial alignment is 30 seconds and can be
changed (see section 6.3.4. LoadINSpar command) but only in agreement
with developers of the Inertial LabsTM INS.
After completing of the initial alignment the INS gives out the block of the
initial alignment data (see the Table 6.28, Table 6.29) and starts data
accumulation during time specified in message sent after the StartVG3DClb
command (see the Table 6.48).
During the INS data accumulation the object should be rotated in full azimuth
range and maximum possible pitch and roll ranges. Allowed object motion
should be agreed with Inertial Labs.
After set accumulation time is reached or StopClbRun command is sent to
the INS (see section 6.7.2 for details) the INS finishes data accumulation and
calculates the calibration parameters.
TM
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After calculation of the calibration parameters that takes <0.5 seconds, the
INS gives out message with the calibration results (see the Table 6.49) and it
waits one of the next commands:
the AcceptClb command (see section 6.7.3) to accept and save the
calibration parameters (usually if the “Calibration success” byte in the INS
message is nonzero and corresponds to satisfactory INS heading
accuracy (see the Table 6.49 and Note below it));
or the ExitClb command (see section 6.7.4) to exit from calibration
procedure without accepting and saving its results (usually if the
“Calibration success” byte in the INS message is equal to 0 or
corresponds to not satisfactory INS heading accuracy (see the Table 6.49
and Note below it)).
The INS answers on these commands with checksum and goes to idle mode.
6.7.6. Start2D2TClb command for INS 2D-2T calibration
The 2D-2T calibration is designed for objects that operate in full azimuth
range but with limited range of pitch and roll angles. This calibration
procedure involves a few full 360 rotations of the object in azimuth with
different pitch angles.
To start the 2D-2T calibration the host computer sends to the INS the
Start2D2TClb command (code 0x22 in the “Payload” field) followed by
message with block of parameters listed in the Table 6.48. This message
have the byte structure shown in the Table 6.2, and should be sent without
pause after sending the Start2D2TClb command.
The INS calculates the check sum of received parameters and returns it for a
checking. Byte structure of this message is shown in the Table 6.2 where
payload is the calculated check sum (1 word).
The 2D-2T calibration procedure involves a few runs with full 360 rotations
of the object with installed INS in heading with different pitch angles.
Set the object to the first pitch angle (usually the minimum pitch angle is set
first). Then send the StartClbRun command followed by message (see
section 6.7.6) to start the first run of the calibration.
TM
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After receiving the StartClbRun command with its message, the INS
calculates the check sum of received block of parameters and returns it for
checking. This check sum should be equal to the check sum in the
StartClbRun command message that was sent to the INS. Byte structure of
this message is shown in the Table 6.2 where payload is the calculated
check sum (1 word).
Then the INS starts process of initial alignment. This process includes the
INS gyros bias estimation, therefore don’t move the INS during its initial
alignment. Default time of the initial alignment is 30 seconds and can be
changed (see section 6.3.4. LoadINSPar command) but only in agreement
with developers of the Inertial LabsTM INS.
After completing of the initial alignment the INS gives out the block of the
initial alignment data (see the Table 6.28, Table 6.29) and starts data
accumulation during time specified in message sent after the Start2D2TClb
command (see the Table 6.48). Rotate object in azimuth with approximately
constant pitch and roll. This rotation must include one or more full 360 deg
turns. Please, correct the time required for such rotation in the «Time of data
accumulation» field of the message (Table 6.48) to provide necessary
rotation.
After set accumulation time is reached or StopClbRun command is sent to
the INS (see section 6.7.2 for details) the INS gives out message with result
of the calibration run (see the Table 6.50).
Table 6.50. Payload of the INS message after each calibration run of the 2D-2T
calibration
Byte
0
1
2
3
Parameter
Format
byte
Type of calibration
byte
Calibration run
byte
Percent of used data
points
byte
Calibration success
4-7
8-11
12-15
16-27
28-29
Reserved
Average pitch, deg
Average roll, deg
Reserved
USW
TM
float
float
float
float
word
Length
1
1
1
1
4
4
4
3*4
2
Note
2 for 2D-2T calibration
1, 2, …
0 – unsuccessful;
>0 – successful (see Note
below)
See section 6.9
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If the “Calibration success” byte is zero (calibration run is not successful) in
the INS answer Table 6.50 then this run will be excluded from calculations in
the 2D-2T calibration procedure. To complete this procedure, it is necessary
to perform at least two successful runs with essentially different pitch angles.
Note: there is estimation of the calibration quality as predicted INS heading accuracy. So
nonzero value of byte #3 “Calibration success” is predicted maximum (3 sigma) heading
error of the INS after calibration, in degrees*10. For example, byte #3 equal to 5
corresponds to the INS accuracy ±0.5 deg. If calibration is successful but INS cannot
estimate predicted accuracy it returns byte #3 equal to 255.
After each calibration run completed the INS sends message with payload
shown in the Table 6.50, and it waits one of the next three commands from
the host computer:
1. StartClbRun command followed by its message (see section 6.7.7) to
start new calibration run. Before send this command the object should
be turned to the next pitch angle. After sending this command the
above described procedure of the calibration run with object rotation in
heading should be performed.
2. FinishClb command (see section 6.7.8 for details) to finish the
calibration procedure and to calculate calibration parameters. After that
the INS gives out message with the calibration results (see the Table
6.48) and waits one of the two commands:
a. the AcceptClb command (see section 6.7.3) to accept and save the
calibration parameters (usually if the “Calibration success” byte in
the INS message is nonzero and corresponds to satisfactory INS
heading accuracy (see the Table 6.49 and Note below it));
b. or the ExitClb command (see section 6.7.4) to exit from calibration
procedure without accepting and saving its results (usually if the
“Calibration success” byte in the INS message is equal to 0 or
corresponds to not satisfactory INS heading accuracy (see the
Table 6.49 and Note below it)).
The INS answers on these commands with checksum and goes to idle
mode.
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3. ExitClb command (see section 6.7.4) In this case the calibration
finishes without any calculations in the INS and without saving any
calibration parameters. The INS answers on this command with
checksum and goes into the idle mode.
Notes:
1. Rotation of the object with the INS in heading must include one or more full 360 turns.
Please, correct the time required for saving data in the «Accumulation time» window to
attain necessary rotations.
2. During calibration run pitch and roll angles should be approximately constant.
3. If place of the INS mounting on the object is changed, or if the object is changed, then
the INS should be re-calibrated on the hard and soft iron of this object.
6.7.7. StartClbRun command
If calibration procedure includes more than one run (like 2D-2T calibration)
then the StartClbRun command (code 0x2B in the “Payload” field) is used to
start each run.
For unification with the StartClbRun command for some other calibration
types, this command must be followed by message with block of parameters
listed in the Table 6.51. But for the 2D-2T calibration the values of those 6
bytes don’t influence, so these 6 bytes may be any, for example zeros. Only
requirement is that this message should have the byte structure shown in the
Table 6.2, and should be sent without pause after sending the StartClbRun
command.
Table 6.51. Payload of the message following after the StartClbRun command
(block of parameters loaded to the INS)
Byte
0-3
4-5
Parameter
Reserved
Reserved
Format
float
word
Length
4
2
Note
After receiving the StartClbRun command the INS calculates the check sum
of received parameters and returns it for a checking. This check sum should
be equal to the check sum in the StartClbRun command message that was
sent to the INS. Byte structure of this message is shown in the Table 6.2
where payload is the calculated check sum (1 word).
TM
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6.7.8. FinishClb command for INS 2D-2T calibration
After receiving the FinishClb command (code 0x2C in the “Payload” field) the
INS finishes the calibration procedure with multiple runs (like 2D-2T) and
calculates the calibration parameters. After that the INS gives out message
with the calibration results (see the Table 6.49).
Then the INS waits one of the next commands:
the AcceptClb command (see section 6.7.3) to accept and save the
calibration parameters;
or the ExitClb command (see section 6.7.4) to exit from calibration
procedure without accepting and saving its results.
6.7.9. Start2DClb command for INS 2D calibration
The 2D calibration is designed for carrier objects that operate in full azimuth
range but with small pitch and roll angles (not more than a few degrees). This
calibration procedure involves full 360 rotation of the carrier object in
azimuth. During this rotation pitch and roll angles must be as close to zero as
possible.
To start the 2D calibration the host computer sends to the INS the Start2DClb
command (code 0x21 in the “Payload” field) followed by message with block
of parameters listed in the Table 6.48. This message have the byte structure
shown in the Table 6.2, and should be sent without pause after sending the
Start2DClb command. Note that first 4 bytes in the payload (Reference
azimuth) do not influence on the 2D calibration as it is noted in the Table
6.48.
The INS calculates the check sum of received parameters and returns it for a
checking. Byte structure of this message is shown in the Table 6.2 where
payload is the calculated check sum (1 word).
Then the INS starts process of initial alignment. This process includes the
INS gyros bias estimation, therefore don’t move the INS during its initial
alignment. Default time of the initial alignment is 30 seconds and can be
changed (see section 6.3.4. LoadINSPar command) but only in agreement
with developers of the Inertial LabsTM INS.
After completing of the initial alignment the INS gives out the block of the
initial alignment data (see the Table 6.28, Table 6.29) and starts data
TM
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accumulation during time specified in message sent after the Start2DClb
command (see the Table 6.48). Rotate carrier object in azimuth with pitch
and roll angles close to zero as possible. This rotation must include one or
more full 360 deg turns. Please, correct the time required for such rotation in
the «Time of data accumulation» field of the message (Table 6.48) to provide
necessary rotation.
After set accumulation time is reached or StopClbRun command is sent to
the INS (see section 6.7.2 for details) the INS finishes data accumulation and
calculates the calibration parameters.
After calculation of the calibration parameters that takes <0.5 seconds, the
INS gives out message with the calibration results (see the Table 6.49) and it
waits one of the next commands:
the AcceptClb command (see section 6.7.3) to accept and save the
calibration parameters (usually if the “Calibration success” byte in the INS
message is nonzero and corresponds to satisfactory INS heading
accuracy (see the Table 6.49 and Note below it));
or the ExitClb command (see section 6.7.4) to exit from calibration
procedure without accepting and saving its results (usually if the
“Calibration success” byte in the INS message is equal to 0 or
corresponds to not satisfactory INS heading accuracy (see the Table 6.49
and Note below it)).
The INS answers on these commands with checksum and goes to idle mode.
6.7.10. ClearClb command
The ClearClb command (code 0x2F in the “Payload” field) is used to clear
parameters of the hard and soft iron calibration from the INS nonvolatile
memory.
The INS answers on this command. The INS calculates the check sum of the
message (without its header and check sum) and returns it for a checking.
Byte structure of this message is shown in the Table 6.2 where payload is the
calculated check sum (1 word).
TM
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You should clear parameters of the soft and hard iron calibration if you
uninstall the INS from object to avoid incorrect azimuth determination with
standalone INS.
6.7.11. GetClbRes command
The GetClbRes command (code 0x2A in the “Payload” field) can be send
from the host computer to check the last calibration results of the INS. As
answer on this command the INS sends out the message with the data block
near the same as after completing calibration, see the Table 6.52.
Table 6.52. Payload of the INS answer on request GetClbRes about calibration
results
Byte
Parameter
Format Length Note
0
byte
1
Type of calibration
0 – INS is not calibrated;
performed
1 – 2D calibration;
2 – 2D-2T calibration;
3 – 3D calibration;
5 – VG3D calibration;
>0x80 – INS is calibrated by
loading calibration parameters from other software (e.g.
Demo software).
1
byte
1
Number of used
calibration runs
2
byte
1
Reserved
3
byte
1
Calibration success
0 – not successful calibration
>0 – successful calibration
(see Note below)
4-39
float
9*4
Matrix for soft iron
Matrix Tm_c (3 3) by rows
correction
39-51 Matrix for hard iron
float
3*4
Matrix Hm_0 (3 1)
correction
Note: There is estimation of the calibration quality as predicted INS heading accuracy. So
nonzero value of byte #3 “Calibration success” is predicted maximum (3 sigma) heading
error of the INS after calibration, in degrees*10. For example, byte #3 equal to 5
corresponds to the INS accuracy ±0.5 deg. If calibration is successful but INS cannot
estimate predicted accuracy it returns byte #3 equal to 255.
TM
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6.7.12. StartVG3Dclb_flight and StopVG3Dclb_flight commands for start
and finish INS on-the-fly VG3D calibration
Since firmware version 2.6.2.2 the INS provides on-the-fly VG3D
calibration. It allows to calibrate INS unit during INS ordinary operation
without interruption of INS navigation data calculation and output.
To start the on-the-fly VG3D calibration the host computer sends to the INS
the StartVG3Dclb_flight command (code 0x26 in the “Payload” field), i.e.
AA 55 00 00 07 00 26 2D 00
Note these are hexadecimal numbers but not ASCII text symbols.
After receiving of this command INS starts accumulation of magnetometers
data for VG3D calibration. At this the bit #7 is set to 1 in INS status word
USW for indication of data accumulation process (see Fig.6.1 and section
6.9).
The carrier object with INS unit should be rotated in full azimuth, pitch and roll
ranges. For example, airplane should perform at least two full 360
coordinated turns (on right and on left) with maximum roll angles.
After finishing of calibration rotation of the carrier object it is necessary to
send the StopVG3Dclb_flight command (code 0x27 in the “Payload” field) to
the INS unit, i.e.
AA 55 00 00 07 00 27 2E 00
Note these are hexadecimal numbers but not ASCII text symbols.
After receiving of this command INS stops data accumulation for VG3D
calibration and sets the USW bit #7 to 0 (see Fig.6.1).
Then INS starts calculations for VG3D calibration and sets USW bit #7 to 1
again. In the end of these calculations, if calibration is successful, INS
calculates calibration parameters for compensation of hard and soft iron, and
stores them to INS nonvolatile memory. Also INS sets the USW bit #15 to 1
to inform the host system that on-the-fly VG3D calibration is performed and
successful (see Fig.6.1).
Calculated calibration parameters are applied immediately to INS
magnetometers data for compensation of hard and soft iron of the carrier
object.
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USW:
Bit #7
1
time
0
Data accumulation
VG3D calculation
USW:
Bit #15
1
time
0
Successful VG3D calibration
Fig.6.1. The diagram of indication of on-the-fly VG3D calibration procedure
in the USW (Unit Status Word, see section 6.9)
Note during all steps of on-the-fly VG3D calibration the INS unit continues
calculation of navigation data and their output.
Because these calibration parameters are stored to INS nonvolatile memory
then they will be applied at all the next INS operations until new calibration is
performed or parameters are cleared using the ClearClb command (see
section 6.7.10).
On the other hand, if INS unit is uninstalled from the carrier object then it is
necessary to clear parameters of the soft and hard iron calibration using the
ClearClb command (see section 6.7.10).
Parameters of the on-the-fly VG3D calibration can be checked after INS stop
using the GetClbRes command (see section 6.7.11).
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6.8. INS automatic start
Since firmware version 1.0.2.0 the Inertial LabsTM INS auto start is
implemented that allows start of its operation and data output after power on
without any command from the host computer. There is possible to choose
desirable output data format for auto start (see section 6.2).
The auto start option can be enabled or disabled using the INS Demo
Program, in the “Options / Device options” menu. There is drop-down list
“Auto start” where auto start with desirable output data format can be chosen.
See INS Demo Program User’s Manual, section “10.5. INS automatic start”
for details.
If the auto start option is enabled then after the INS power on the next
operations take place:
Initialization of the onboard GNSS receiver that takes not more than 15
seconds. The INS LED indicator lights yellow.
Then the INS automatically starts operation from sending out the
message AA 55 01 00 08 00 00 00 09 00 (in hexadecimal format) that
indicates INS started without any external command. The INS LED
indicator changes color to green.
After that the initial alignment procedure starts when initial orientation
angles are calculated and gyros bias is estimated for its next
compensation. Therefore don’t move the INS during initial alignment
process. If this requirement is not met then large errors may be
occurred in orientation angles calculation.
Note: Default time of the initial alignment is 30 seconds. It can be changed (see
section 6.3.4) but only in agreement with developers of the Inertial LabsTM INS.
After completing of the initial alignment the INS gives out message with
block of the initial alignment data (see Table 6.27) and starts data
output according to the chosen data format. The INS LED indicator
lights green.
Note: To identify the INS output data format at auto start mode use the INS data
identifier in the data block structure (see Table 6.2, byte #3) which is equal to the
command code and corresponds to data format according to the Table 6.20. This is
implemented in the INS firmware since version 2.1.2.0.
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To stop the INS please send the Stop command (see section 6.3.3). After
receiving the Stop command the INS stops data calculation and goes to the
idle mode. The INS LED indicator changes its color to red. The INS is ready
to receive any command from the host computer.
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6.9. The Unit Status Word definition
The Unit Status Word (USW) provides the INS state information. The low
byte (bits 0-7) of USW indicates failure of the INS. If this byte is 0, the INS
operates correctly, if it is not 0, see the Table 6.53 for type of failure. The high
byte (bits 8-15) contains a warning or is informative for the user. Status of
each bit of the USW warning byte is specified in the Table 6.53.
Table 6.53. The Unit Status Word description
Low
(failure)
byte
High
(warning)
byte
Bit
0
Parameter
Initial Alignment
1
INS Parameters
2
Gyroscope Unit
3
Accelerometer Unit
4
Magnetometer Unit
5
Electronics
6
GNSS receiver
7
On-the-fly VG3D
calibration
8
9
Incorrect Power
Supply
10
11
Angular Rate
Exceeding Detect
12
13
14
15
Large Magnetic
Field Detect
Environmental
Temperature
On-the-fly VG3D
calibration
TM
Description
0 – Successful initial alignment
1 – Unsuccessful initial alignment due to INS
moving or large changing of outer magnetic field
0 – Parameters are correct
1 – Parameters are incorrect
0 – No failure
1 – Failure detected
0 – No failure
1 – Failure detected
0 – No failure
1 – Failure detected
0 – No failure
1 – Failure detected
0 – No failure
1 – Failure detected
1 – during data accumulation and calculation
0 -- otherwise
0 – Supply voltage is not less than minimum level
1 – Low supply voltage detected
0 – Supply voltage is not greater than max level
1 – High supply voltage detected
0 – X-angular rate is within the range
1 – X-angular rate is outrange
0 – Y-angular rate is within the range
1 – Y-angular rate is outrange
0 – Z-angular rate is within the range
1 – Z-angular rate is outrange
0 – Total magnetic field is within the normal range
1 – Total magnetic field limit is exceeded
0 – Temperature is within the operating range
1 – Temperature is out of the operating range
0 – No on-the-fly calibration
1 – Successfully calibrated during current run
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6.10. Post-processing of the INS and GNSS data
For applications requiring highly accurate postmission position, velocity and
orientation, the INS and GNSS data post-processing can be used. This
feature is provided by NovAtel software, see
http://www.novatel.com/products/software/ .
For such post-processing the raw GNSS and raw IMU data should be used.
The Inertial LabsTM INS uses the second COM port (COM2) for output the
raw GNSS receiver data (see section 6.10.1). Starting from the INS s/n
F1560005 presence of the COM2 is default option. For raw GPS data
recording from receiver an external program GNSS_Reader can be used.
The GNSS_Reader is supplied with the Inertial Labs INS Demo software.
File with raw IMU data can be created from files .bin, .prm created by INS
Demo Program. Use “Convert to IMU data” item in the “Convert” menu – see
the Inertial LabsTM INS Demo Program User’s Manual, section “12.2. Raw
IMU data generation”.
For more details about post-processing see Section “12. INS and GNSS data
post-processing” in the INS Demo Program User’s Manual.
6.10.1. Raw GNSS receiver data
The Inertial LabsTM INS uses the COM2 port for output the raw GNSS
receiver data. The INS starts output of these data after power on and
completing of the receiver initialization (when the INS LED indicator switches
from yellow to red).
Raw GNSS data consist of necessary logs for post-processing. There are
synchronous and asynchronous logs. The data for synchronous logs are
generated with set frequency. In order to output the most current data as
soon as they are available, asynchronous data are generated at irregular
intervals. List of generated logs is shown in the Table 6.54.
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Table 6.54. Logs of raw GNSS data
Log
Description
Asynchronous
CLOCKSTEERING
GLOCLOCK
ALMANAC
GPSEPHEM
RAWALM
RAWEPHEM
RAWGPSSUBFRAME
RAWCNAVFRAME
RAWGPSWORD
GLOALMANAC
GLOEPHEMERIS
GLORAWALM
GLORAWEPHEM
GLORAWFRAME
GLORAWSTRING
MARK2POS
MARK2TIME
Clock steering status
GLONASS clock information
Decoded GPS Almanac
Decoded GPS ephemerides
Raw Almanac data
Raw ephemeris
Raw subframe data
Raw CNAV frame data
Raw navigation word
Decoded GLONASS Almanac
Decoded GLONASS ephemeris
Raw GLONASS Almanac data
Raw GLONASS Ephemeris data
Raw GLONASS frame data
Raw GLONASS string
Position at time of mark input event (see note below)
Time of mark input event (see note below)
Synchronous
CLOCKMODEL
TIMESYNC
TIME
RANGE
RANGEGPSL1
TRACKSTAT
Current clock model status
Synchronize time between GNSS receivers
Time data
Satellite range information
L1 version of the RANGE log
Tracking status
Note: If input marks are enabled (MARK_switch = 1, see section 6.4.1) then asynchronous
MARK2POS and MARK2TIME logs are added to the raw GNSS data when a pulse is
detected at GPIO mark input (see section 5.4).
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6.11. Synchronization of INS data with LiDAR and other devices
Synchronization of the Inertial LabsTM INS measurements with data form
other devices is very important in many applications. The INS can trigger
other devices, or an external device can trigger the INS measurements.
6.11.1. Synchronization pulses issued by INS
To trigger external devices the Inertial LabsTM INS outputs accurate pulse per
second (PPS) signal generated by on-board GNSS receiver. The PPS signal
is provided by appropriate pin of the INS main connector (see Table 5.1 and
Table 5.2). See section “5.3. PPS description” for details.
Adjustment of the PPS signal (pulse polarity, period, width) can be done
using the Inertial LabsTM INS Demo Program – see User’s Manual, section
“13.1.1. Control of PPS output signal” for details.
6.11.2. Trigging of INS by external devices
The Inertial LabsTM INS output data can be get on request by two ways.
At the first, the INS can operate in the “On Request” (on demand) mode
when the INS sends one data block after each Request command issued
from the host computer. See section “6.3.2. SetOnRequestMode command –
getting INS data on request (on demand)” for details.
The second way of the INS data synchronization is using of General Purpose
Input Output (GPIO) line to trigger the INS output data by external devices.
GPIO line is connected to appropriate pin of the INS main connector (see
Table 5.1 and Table 5.2). Also, see section “5.4. GPIO description”. Currently
the GPIO is used to trigger GNSS raw data in INS.
6.11.3. Synchronization of INS data with LiDAR
For Inertial Labs INS operation with LiDAR it is necessary to make the next
connections:
use INS COM1 port for output of the main INS data;
use INS COM2 port for output of GNSS raw data or NMEA data set
generated by INS onboard GNSS receiver;
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connect INS COM3 port for output of $GPRMC messages issued by
INS onboard GNSS receiver to LiDAR;
connect pulse-per-second (PPS) signal generated by INS onboard
GNSS receiver to LiDAR;
optionally, for camera synchronization – connect General Purpose Input
Output (GPIO) line for input signal from camera to trigger specific
GNSS receiver data (MARK2POS and MARK2TIME logs)
All these data and signals are available on the main INS connector – see
section “5. Electrical interface”. For adjustment of INS data and signals use
INS Demo Program. See INS Demo Program User’s Manual, section “13.3.
INS operation with LiDAR” for details.
6.12. Change of the main COM port baud rate
COM1 is the main COM port. It is used for commands and data transfer
between the Inertial LabsTM INS and the host computer.
The default baud rate for the INS COM1 port is set to 115200 bps (maximum
for the standard COM-port). Since firmware version 2.2.0.0 the INS supports
different baud rates: 4800, 9600, 14400, 19200, 38400, 57600, 115200,
230400, 460800 bps.
Change of the INS COM1 port baud rate can be done using INS Demo
Program since version 2.0.19.78 from 03/18/2016. See INS Demo Program
User’s Manual, section “4.2.4. Change of the main COM port baud rate” for
details.
Note the same baud rate must be set for COM port of the host computer.
6.13. Limitation of the INS maximum output data rate
When setting of the output data rate for the INS unit using LoadAHRSIIPar
command (see section 6.3.4) or using the Inertial LabsTM INS Demo Program
it is essential to ensure the chosen baud rate of the main COM port is
capable of handling the data throughput with desirable data rate. The
maximum data rate (Hz) can be calculated using the baud rate and data
package length:
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max_data_rate
COM_baud_rate
,
bits_per_byte * package_length
(6.1)
where COM_baud_rate is COM port baud rate (bits/s); bits_per_byte = 11
bits per one transferred byte of data; package_length for binary data =
payload length plus 8 bytes of overhead. See Tables 6.4, 6.7, 6.8, 6.9, 6.10,
6.11 and 6.17 for payload length of binary output data formats. The
package_length of the text output data formats correspond to their structure
shown in sections 6.2.1 to 6.2.7.
Below Table 6.55 contains data package length for each output data format
and also maximum data rate calculated using formula (6.1), with some spare.
Note the maximum measurement rate of INS data is limited by 200 Hz.
Table 6.55. INS maximum measurement rate for different output data formats
Output data format
INS Sensors Data
INS Full Output Data
INS OPVT
INS QPVT
INS OPVT2A
INS OPVT2AW
INS OPVT2Ahr
INS Minimal Data
INS NMEA
INS Sensors NMEA
TSS1
COM-port baud rate, bps
Data
package
length,
bytes
9600
84+8
94+8
92+8
94+8
101+8
103+8
129+8
50
93
141
27
9
8
8
8
8
7
6
10
9
6
20
19200
38400 115200 230400
Maximum measurement rate, Hz
100
10
30
200
100
10
30
200
100
10
30
200
100
10
30
200
90
10
30
190
90
10
30
180
70
10
20
150
200
30
60
200
100
10
30
200
80
10
20
140
200
50
100
200
460800
200
200
200
200
200
200
200
200
200
200
200
Note INS unit controls correctness of the data rate setting. If user sets data
rate which exceeds limit shown in Table 6.55, then its value is corrected.
True data rate is given out in the byte #3 of INS message after completing of
the initial alignment procedure (see Table 6.28, Table 6.29).
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APPENDIX A.
The Inertial LabsTM INS Calibration
The Inertial LabsTM INS software allows to take into account influence of the
carrier object soft and hard iron on the heading determination. For this
purpose, field calibration of the INS magnetometers on hard and soft iron is
provided. This calibration does not require any additional equipment, but it
requires setting of the carrier object, where the INS is mounted, in specified
positions.
There are several types of the calibration implemented onboard the INS:
3D calibration;
2D-2T calibration;
2D calibration;
VG3D calibration;
on-the-fly VG3D calibration.
Other types of hard/soft iron calibration can be fulfilled with Inertial Labs INS
Demo software.
3D calibration is designed for carrier objects that can operate in full heading,
pitch and roll ranges. For this calibration the carrier object is rotated in the
horizon plane (the Z-axis is up) with periodical stops about each 90 degrees
for tilting in pitch and roll. After full 360 rotation the carrier object with the
INS is turned over (the Z-axis is down) and the procedure described above
should be repeated. During this calibration the range of pitch and roll angles
changing must be as much as possible.
VG3D calibration is similar to 3D calibration but allows performing simpler
rotation than it is necessary for 3D calibration.
2D-2T calibration is designed for carrier objects that operate in full heading
range but with limited range of pitch and roll angles. This calibration
procedure involves a few full 360 rotations of the carrier object with installed
INS in heading with different pitch angles. During each rotation, pitch and roll
angles should be as constant as possible.
2D calibration is designed for carrier objects that operate in full azimuth
range but with small pitch and roll angles (not more than a few degrees). This
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calibration procedure involves full 360 rotation of the carrier object with
installed INS in the horizon plane. During this rotation pitch and roll angles
must be as close to zero as possible.
On-the-fly VG3D calibration allows to calibrate INS unit during INS ordinary
operation without interruption of INS navigation data calculation and output.
If place of the INS mounting on the carrier object is changed, or if the carrier
object is changed, then the INS should be re-calibrated on the hard and soft
iron of the carrier object.
See section 6.7 for detailed description of embedded calibration procedures.
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APPENDIX B.
Variants of the Inertial Labs INS mounting relative to the object axes
TM
The Inertial LabsTM INS can be mounted on the object in any known position
(up to upside-down, upright etc.) relative to the object axes. Such mounting
doesn’t change right determination of the object orientation if angles of the
INS mounting are correctly stored in the INS nonvolatile memory.
To store angles of the INS mounting to its nonvolatile memory please use the
Inertial LabsTM INS Demo Program (item «Device option …» from the
«Options» menu) or send LoadINSPar command to the INS directly (see
structure of the message following after the LoadINSPar command in the
Table 6.22). In both cases these angles are denoted as “Alignment angles”.
Angles of the INS position (alignment angles) are set in next order (like
heading, pitch and roll setting):
first alignment angle sets position of the INS longitudinal axis Y relative
to longitudinal axes of the object measured in the horizontal plane of the
object. Clockwise rotation is positive;
second alignment angle is equal to angle of inclination of the INS
longitudinal axis Y relative to the horizontal plane of the object. Positive
direction is up;
third alignment angle is equal to inclination angle of the INS lateral axis
X measured around INS’ longitudinal axis. Positive rotation is X axis
moving down.
All angles are set in degrees. Some examples of the Inertial Labs INS
mounting relative the carrier object are shown on Fig.B.1.
To check correctness of the alignment angles please run the INS using the
Inertial Labs INS Demo program. Default values of the INS alignment angles
are all zero.
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APPENDIX C.
Full list of the Inertial LabsTM INS commands
All the INS commands have the byte structure shown in the Table 6.2.
Payload for all commands has length 1 byte and contains code of the
command. Below Table C.1 lists all commands with their exact structure in
hexadecimal numbers.
Table C.1. List of the INS commands with exact structure
Command name
Code
Exact structure (hex)
TM
Commands for Inertial Labs INS control
INS_SensorsData
0x50
AA 55 00 00 07 00 50 57 00
INS_FullData
0x51
AA 55 00 00 07 00 51 58 00
INS_OPVTdata
0x52
AA 55 00 00 07 00 52 59 00
INS_QPVTdata
0x56
AA 55 00 00 07 00 56 5D 00
INS_OPVT2Adata
0x57
AA 55 00 00 07 00 57 5E 00
INS_OPVT2AWdata 0x59
AA 55 00 00 07 00 59 60 00
INS_OPVT2Ahrdata 0x58
AA 55 00 00 07 00 58 5F 00
INS_minData
0x53
AA 55 00 00 07 00 53 5A 00
INS_NMEA
0x54
AA 55 00 00 07 00 54 5B 00
INS_Sensors_NMEA 0x55
AA 55 00 00 07 00 55 5C 00
INS_TSS1
0x35
AA 55 00 00 07 00 35 3C 00
SetOnRequestMode 0xC1
AA 55 00 00 07 00 C1 C8 00
Stop
0xFE
AA 55 00 00 07 00 FE 05 01
LoadINSpar
0x40
AA 55 00 00 07 00 40 47 00
ReadINSpar
0x41
AA 55 00 00 07 00 41 48 00
GetBIT
0x1A
AA 55 00 00 07 00 1A 21 00
TM
Commands for Inertial Labs INS calibration
Start2DClb
0x21
AA 55 00 00 07 00 21 28 00
Start2D2TClb
0x22
AA 55 00 00 07 00 22 29 00
Start3DClb
0x23
AA 55 00 00 07 00 23 2A 00
StartVG3DClb
0x25
AA 55 00 00 07 00 25 2C 00
StartVG3Dclb_flight
0x26
AA 55 00 00 07 00 26 2D 00
StopVG3Dclb_flight
0x27
AA 55 00 00 07 00 27 2E 00
StartClbRun
0x2B
AA 55 00 00 07 00 2B 32 00
Stop lbRun
0x20
AA 55 00 00 07 00 20 27 00
Finish lb
0x2C
AA 55 00 00 07 00 2C 33 00
AcceptClb
0x2E
AA 55 00 00 07 00 2E 35 00
ExitClb
0xFE
AA 55 00 00 07 00 FE 05 01
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ClearClb
GetClbRes
0x2F
0x2A
AA 55 00 00 07 00 2F 36 00
AA 55 00 00 07 00 2A 31 00
APPENDIX D.
Forms of the Inertial LabsTM INS orientation presentation
Define coordinate system Oxoyozo to be fixed to the carrier object where Oxo
axis is lateral and directed to the right, Oyo axis is longitudinal and directed
forward, Ozo axis is normal and directed vertical. At usual installation of the
INS on carrier object the INS appropriate axes should be parallel to the axes
as above Fig.1.3 shows. Also, it is possible to install the INS in any known
position relative to the object with known alignment angles (see APPENDIX B
for details).
The Inertial LabsTM INS calculates orientation of the coordinate system
Oxoyozo fixed to the carrier object with respect to Cartesian geographical
reference frame Oxyz where axes Ox and Oy are in the level and directed to
the East and North, and Oz axis is directed up. Such reference frame is also
known as ENU (East-North-Up) Earth-level frame.
Measured angles are the standard Euler angles of rotation from the Earthlevel frame to the object frame: heading K is first, then pitch , and then roll
-- see Fig.D.1.
Notes:
1. Positive direction of heading is clock-wise. So heading K is shown with minus sign on
Fig.D.1.
2. In different applications “heading” is also known as “azimuth” or “yaw”; “pitch” is also
known as “elevation” or “tilt”; “roll” is also known as “bank”.
Due to the definition of Euler angles there is a mathematical singularity when
the object longitudinal y0-axis is pointed up or down (i.e. pitch approaches
±90 ). This singularity is not present in the quaternion or directional cosine
matrix (rotation matrix) presentation.
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z
(Up)
z0
(Vertical)
K
O
y0
(Longitudinal)
-K
x
(East)
-K
y
(North)
x0
(Lateral)
Fig.D.1. Transformation of coordinate systems
Directional cosine matrix (DCM) is the rotation matrix C from the object body
reference frame Oxoyozo to the geographical reference frame Oxyz.
According to Fig.D.1, DCM can be represented through Euler angles as
cos K cos
=
sin K cos
sin K sin sin
cos K sin sin
cos sin
sin K cos
cos K cos
sin
cos K sin
sin K cos sin
sin K sin
cos K cos sin
cos cos
.
(D.1)
Or, Euler angles can be calculated from elements cij of directional cosine
matrix C:
c
c
arctan 31 .
(D.2)
K arctan 12 ;
arcsin c 32 ;
c33
c22
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Also the Inertial LabsTM INS provides orientation output in quaternion Q form
which is a hyper-complex number with four components
Q = (q0, q1, q2, q3 ),
(D.3)
where q0 is real part, q1, q2, q3 are vector part. In other words, q0 represents
the magnitude of the rotation, and the other three components represent the
axis about which that rotation takes place.
With only four components, quaternion representation of orientation is
computationally efficient. However, manipulation of quaternions is not
intuitive, so their use in place of directional cosine matrices may increase the
chances of mistakes being made.
Quaternion Q is converted to directional cosine matrix C using the next
expressions:
q02
C
q12
2 q1 q 2
q 22
q 0 q3
2 q1 q3
q32
2 q1 q 2
q02
q0 q2
q 22
q12
2 q 2 q3
q 0 q3
2 q1q3
q32
2 q 2 q3
q0 q1
q
2
0
q
2
3
q0 q2
q0 q1
2
1
q
q
.
(D.4)
2
2
The reverse conversation from directional cosine matrix C to quaternion Q is
following:
1
q0
1 c11 c 22 c33 ;
(D.5)
2
q1
c32 c23
; q2
4q0
c13 c31
;
4q0
q3
c21 c12
.
4 q0
Expressions (D.5) are wide used but they have singularity at q0 = 0.
Therefore the Inertial LabsTM INS uses other expressions that have no
singularity:
q0
q2
1
1 c11
2
c33 ; q1
c 22
1
1 c11 c22 c33 sign c13
2
TM
1
1 c11 c22 c33 sign c32 c23 ;
(D.6)
2
1
1 c11 c22 c33 sign c21 c12 .
c31 ; q3
2
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At necessity to calculate Euler angles from quaternion, calculate elements
c12, c22, c31, c32, c33, according to (D.6), and then use formulas (D.2):
K
arctan
2 q1q2 q0 q3
;
q02 q 22 q12 q32
arctan
arcsin( 2q2 q3
2q0 q1 ) ;
(D.7)
2 q1q3 q0 q2
,
q02 q32 q12 q22
where arctan is four-quadrant inverse tangent.
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