VIM Interface Document - · PDF fileVehicle Inertia Monitor (VIM) : Interface Document. SAE J1939 Parameter Group Numbers (PGNs) PGN . Offset1: Descrip . Byte: Data : Comments . RO

Vehicle Inertia Monitor (VIM) : Interface Document

Vehicle Inertia Monitor (VIM) Interface Document

- Confidential -

Yashu Systems : Confidential Page 1 of 16 15-Nov-2014 :: v5


Vehicle Inertia Monitor:

VIM Features:

• DSP Microcontroller Hosts Advanced Data Processing Algorithms and Applications

• CAN Bus Interface to Acquire and Transmit Vehicle Data used in Parameter Calculations

• Thick Walled ABS Plastic Enclosure with Brass Insert Compression Limiters : 1.9” L x 2.3” W x 0.56” H

• -40C to +85C Wide Temperature Range Operation for Harsh Environments : Epoxy Potted : Waterproof

• Low Power Sleep Mode with Tri-Color Status LED

VIM Capabilities:

• Integrated 3D MEMS Accelerometer and Gyroscope support Moving Vehicle Pitch and Roll Attitude Estimates

o Data Fusion via Advanced Kalman Filter with Vehicle Longitudinal and Lateral Acceleration Compensation

o Unique Gyro Precession Compensation Estimate supports Vehicle Maneuvers on Inclined Surfaces

• Incorporates Proprietary Vehicle Kinematic Model using available CAN Parametrics, MEMS Sensor Data and Vehicle Frame Dimensioning

o Supports Arbitrary Mounting Location and Rotation when affixed to Vehicle Frame

o Integrated Calibration Functions simplify Formulation of Mounting Rotation Matrix and Correction Factor for Drive Wheel Speeds Difference

• Integrated CAN Communications Stack supports Periodic Transmissions of Single and Multi-Frame Messages

o Simultaneous 11 and 29 Bit Arbitration ID Addressing

o Support for Arbitrary or Preferred Addressing

• 3-Axis 2KHz Vibration Monitoring of SubBand Frequency G-Force Levels for use in Basic Terrain Identification

• Real-Time Frequency Spectrum Updates across CAN

• Power Spectral Density versus Wave Number Processing for Advanced Longitudinal Terrain-ID Profiling (Future)



Accelerometer, Gyroscope and Vehicle Pitch / Roll Reference - Recommended Orientation 2:

Vehicle Inertia Monitor (VIM) Vehicle Frame Mounting Reference:

VIM POSITION

VIM YAW

VIM PITCH

VIM ROLL


Vehicle Inertia Monitor (VIM) : Interface Document SAE J1939 Parameter Group Numbers (PGNs)

PGN Offset1 Descrip RO Byte: Data Comments

0x0000 -BAM-

Status 0 -5sec Xmit-

• 0: Unit Type 0x00: - Reserved - 0x01: Wireless Sensor Module (WSM) 0x02: DSP Sensor Module (DSM) 0x03: USB Can Fob (UCF) 0x04: Vehicle Inertia Monitor (VIM) 0x05: DSP Inertia Monitor (DIM) 0x06: Remote Sensor Monitor (RSM) 0x07: USB Can Interface (UCI) 0x08: Miniature Data Logger (MDL) 0x09: Reserved

• 1: Unit Status 0:Bad Firmware 1:Ready • 2-9: Unit Ver Unit Version : PCBMajor, PCBMinor, (8-bit binary): BOM, BLoadVer, 4 spare • 10-25: Firm Version Firmware Version (ASCII) • 26-41: Description User defined description of unit (ASCII)

• 42-45: Serial Number 1st Byte : W:WSM D:DSM I:DIM R:RSM (ASCII) : V:VIM U:UCF C:UCI M:MDL

2nd-4th Byte: SN (24-bit binary value) 0x0001 Status 1 • 0: Unit Temperature 1 degC/quanta : +55.0 degC Bias

-2sec Xmit- • 1: Supply Voltage3 0.25 V/quanta • 2-7: Spare

0x0002 Config 0 0: Unit Mode MSBit --Bit Mapped-- LSBit -Solicited- - - - - MODE3 MODE2 MODE1 MODE0

Mode of Operation MODE: 0:Idle 1:Raw Sensor 2:Vibration 3:Attitude 4:Pitch/Roll 5:Wheel Slip

1: Attitude Data Avg Count At 100ms sampling rate for: CAN Speed : MEMS Accel : MEMS Gyro

2: MEMS Data Delay 50ms/quanta : MEMS data delayed by this to sync to delay of CAN speed data

• 3-7: Spare


Vehicle Inertia Monitor (VIM) : Interface Document SAE J1939 Parameter Group Numbers (PGNs) (cont)


0x0003 Config 1 0: Calibration Control Byte MSBit --Bit Mapped-- LSBit -Solicited- - DECPSI INCPSI CLRR CALCR RSTCAL CALYAW RSTYAW Reset Yaw Angle RSTYAW: 0:Idle 1:Reset >> Future3 Calibrate Yaw Angle CALYAW: 0:Idle 1:Calibrate >> Feature Reset Yaw Calibration RSTCAL: 0:Idle 1:Reset Calculate Rotation Matrix CALCR: 0:Idle 1:Calculate Clear Rotation Matrix CLRR: 0:Idle 1:Clear Incr Yaw Mount Angle (ψVIM) INCPSI: 0:Idle 1:Increment Decr Yaw Mount Angle (ψVIM) DECPSI: 0:Idle 1:Decrement • 1-7: Spare

0x0004 CAN Config 0: Basic Config MSBit --Bit Mapped-- LSBit -2sec Xmit- - - - - - - - ARBADDR

Arbitrary Address Capable ARBADDR: 0:Static Address Only 1:Arbitrary Address Capable

1: Preferred Address 2: Claim Start Address 3: Claim End Address

Used if ARBADDR == 1

4,5: PGN Base Address Default: 0xFF50 6,7: Confirmation Word3




0x0005 Vibration 0: Grms Vibe Config 0 MSBit --Bit Mapped-- LSBit Mode Config - ENBZ ENBY ENBX GRNG1 GRNG0 TR1 TR0 -Solicited- CAN Transmit Rate TR: 0:Fastest 1:250ms 2:1sec 3:3sec G-Range GRNG: 0:+/-2G 1:+/-4G 2:+/-8G 3:+/-16G Channel Enables ENBX,ENBY,ENBZ: 0:Disable 1:Enable 1: Grms Vibe Config 1 MSBit --Bit Mapped-- LSBit - CPLZ CPLY CPLX ORDTRK - IFC1 IFC0 InterFrame Computation IFC: 0:None 1:Peak 2:Mean 3:RMS Order Tracking3 ORDTRK: 0:Disable 1:Enable (Future) Channel Coupling CPLX,CPLY,CPLZ: 0:DC 1:AC 2: Spare 3: Spectrum Option MSBit --Bit Mapped-- LSBit ENB - IFC1 IFC0 CHAN1 CHAN0 TR1 TR0 CAN Transmit Rate TR: 0:Fastest 1:1sec 2:2sec 3:Compliant4 Channel Select CHAN: 0:CHX 1:CHY 2:CHZ InterFrame Computation3 IFC: 0:None 1:Peak 2:Mean Enable Spectrum Option ENB: 0:Disable 1:Enable 4: FFT Config 0 MSBit --Bit Mapped-- LSBit - WIN2 WIN1 WIN0 BW3 BW2 BW1 BW0

Vibration Bandwidth BW: 0:60Hz 1:140Hz 2:300Hz 3:600Hz 4:1200Hz 5:2000Hz

Scaling Window WIN: 0:None 1:Hamming 2:Hanning 3:Blackman 4:Bartlett 5-7: Spare




0x0006 Vehicle • 0: Vehicle Pitch - MEMS Accel Only Attitude • 1: Vehicle Pitch - Kalman Filtered

θVEH : 0.125 Deg/quanta : +16.0 Deg Bias

-1sec- and • 2: Vehicle Roll - MEMS Accel Only -100msec- • 3: Vehicle Roll - Kalman Filtered

φVEH : 0.125 Deg/quanta : +16.0 Deg Bias

-Xmit- • 4,5: Spare • 6,7: Relative Time Stamp 1 ms/quanta : modulo-2^16

0x0007 Channel-X 0,1: SubBand 0 Start Freq SubBand 2,3: SubBand 1 Start Freq 0.1 Hz/quanta Start Freqs 4,5: Subband 2 Start Freq -Solicited- • 6,7: Spare

0x0008 Channel-X 0,1: SubBand 0 Stop Freq SubBand 2,3: SubBand 1 Stop Freq 0.1 Hz/quanta Stop Freqs 4,5: Subband 2 Stop Freq -Solicited- • 6,7: Spare

0x0009 Channel-Y 0,1: SubBand 0 Start Freq SubBand 2,3: SubBand 1 Start Freq 0.1 Hz/quanta Start Freqs 4,5: Subband 2 Start Freq -Solicited- • 6,7: Spare

0x000A Channel-Y 0,1: SubBand 0 Stop Freq SubBand 2,3: SubBand 1 Stop Freq 0.1 Hz/quanta Stop Freqs 4,5: Subband 2 Stop Freq -Solicited- • 6,7: Spare

0x000B Channel-Z 0,1: SubBand 0 Start Freq SubBand 2,3: SubBand 1 Start Freq 0.1 Hz/quanta Start Freqs 4,5: Subband 2 Start Freq -Solicited- • 6,7: Spare

0x000C Channel-Z 0,1: SubBand 0 Stop Freq SubBand 2,3: SubBand 1 Stop Freq 0.1 Hz/quanta Stop Freqs 4,5: Subband 2 Stop Freq -Solicited- • 6,7: Spare




0x000D Channel-X • 0,1: SubBand 0 Grms Level Grms Levels • 2,3: SubBand 1 Grms Level 1/256 Grms/quanta -Prog Xmit- • 4,5: Subband 2 Grms Level • 6,7: Vehicle Speed 1/256 KPH/quanta

0x000E Channel-Y Grms Levels See above PGN-Offset 0x000D -Prog Xmit-

0x000F Channel-Z Grms Levels See above PGN-Offset 0x000D -Prog Xmit-

0x0010 3D G-Levels • 0,1: Channel-X Accel -100msec- • 2,3: Channel-Y Accel 1/1024 G/quanta : +32.0 G Bias -Xmit- • 4,5: Channel-Z Accel • 6,7: Relative Time Stamp 1 ms/quanta : modulo-2^16

0x0011 Vehicle • 0,1: Avg Vehicle Speed 1/256 KPH/quanta Pitch CAN Data Based Based on Attitude Data Avg Count (PGNoff 0x0002) -100msec- • 2,3: Vehicle Long Accel 1 mG/quanta : +32.768 G Bias -Xmit- CAN Data Based Derivative of previous Avg Vehicle Speed • 4,5: Channel-X Accel 1 mG/quanta : +32.768 G Bias Raw MEMS CH-X accelerometer data • 6,7: Avg Channel-X Accel 1 mG/quanta : +32.768 G Bias Average of previous Channel-X Accel Based on Attitude Data Avg Count (PGNoff 0x0002)

0x0012 3D GyroRates • 0,1: Channel-X GyroRate -100msec- • 2,3: Channel-Y GyroRate -Xmit- • 4,5: Channel-Z GyroRate

1/10 Deg/s/quanta : +3276.8 Deg/s Bias

• 6,7: Relative Time Stamp 1 ms/quanta : modulo-2^16 0x0013 Vehicle • 0,1: Yaw 1/10 Deg/quanta : +180.0 Deg Bias

Heading • 2,3: YawRate 1/10 Deg/s/quanta : +3276.8 Deg/s Bias -100msec- • 4,5: X Location -Xmit- • 6,7: Y Location

1/10 Meter/quanta : +3276.8 Meter Bias




0x0014 Vehicle IDs 0-15: ID0 -BAM- -3sec Xmit- 16-31: ID1

32-47: ID2 48-63: ID3

User defined general purpose 16-Byte IDs (ASCII)

0x0015 Vehicle • 0,1: Steer Angle 1/100 Deg/quanta Roll • 2,3: Vehicle Lateral Accel 1 mG/quanta : +32.768 G Bias -100msec- CAN Data Based Based on Commanded L/R Wheel Speeds -Xmit- • 4,5: Long G Compensation 1 mG/quanta : +32.768 G Bias Kinematic Model Based Based on Commanded CAN Motion Parameters • 6,7: Lateral G Compensation 1 mG/quanta : +32.768 G Bias Kinematic Model Based Based on Commanded CAN Motion Parameters

0x0016 Vehicle • 0,1: Avg Wheel Speed 1/256 KPH/quanta Speeds • 2,3: L/R Delta Wheel Speed 1/256 KPH/quanta : +128 KPH Bias -100msec- • 4,5: Left Rear Wheel Speed -Xmit- • 6,7: Right Rear Wheel Speed

1/256 KPH/quanta

... 0x001C VIM Mounting 0,1: Yaw Angle (ψVIM)

Rotation 2,3: Pitch Angle (θVIM) Matrix 4,5: Roll Angle (φVIM)

1/10 Deg/quanta : +180.0 Deg Bias

-1sec Xmit- • 6,7: Spare 0x001D VIM Mounting 0,1: WVIM (Lateral Offset)

Position 2,3: LVIM (Longitudinal Offset) -1sec Xmit- 4,5: WVEH (WheelTrack Width) 6,7: LVEH (WheelBase Length)

1/1000 Meter/quanta : 2’s comp

0x001E Vehicle 0,1: Gearbox Ratio 1/100 /quanta : 2’s comp Drive Config 2,3: Drive Wheel Diameter 1/1000 Meter/quanta : 2’s comp -1sec Xmit- 4,5: L/R Speed Ratio 1/1000 /quanta : 2’s comp 6,7: Caster Angle Cal Offset 1/10 Deg/quanta : 2’s comp




0x001F VIM Nonvolatile 0-15: Description User defined description of profile (ASCII) -BAM- Configuration 16-23: PGN-Offset 0x001D VIM Mounting Position

Profile 24-31: PGN-Offset 0x001C VIM Mounting Rotation Matrix -3sec Xmit- 32-39: PGN-Offset 0x001E VIM Drive Config 40-47: PGN-Offset 0x0002 VIM Config 0 48-55: PGN-Offset 0x0005 VIM Vibration Mode Config 56-63: PGN-Offset 0x0007 Vibration Mode : Channel-n SubBand Start Freqs 64-71: PGN-Offset 0x0008 Vibration Mode : Channel-n SubBand Stop Freqs

PGN Descrip RO Byte: Data Comments

0xEFxx Vibration • 0-479: FFT Spectrum Data 60Hz BW: 0.15625Hz per bin -P2P- Spectrum 140Hz BW: 0.3125Hz per bin

-Prog Xmit- 300Hz BW: 0.625Hz per bin 600Hz BW: 1.25Hz per bin 1200Hz BW: 2.5Hz per bin 2000Hz BW: 5.0Hz per bin +/-2G Range: 1/128 Grms/quanta +/-6G Range: 1/32 Grms/quanta

NOTES:

1: PGN Address = PGN Offset + PGN Base Address(see PGN-Offset 0x0004) 2: For best performance in attitude estimate modes, mount the VIM as close as possible to the center of the vehicle fixed axle from which wheel speeds are associated. Also, rotate the VIM as close as possible to the recommended orientation. 3: Future Feature - Not implemented as of date of this document 4: CAN multi-packet minimum transmission period complies to SAE J1939 specification


Vehicle Inertia Monitor (VIM) : Interface Document Transmitted PGNs based on VIM Mode (PGN-Offset 0x0002 : Unit Mode -> MODE) J1939 PGN Offset1

0x0000 0x0001 0x0004 0x0006 0x000D 0x000E 0x000F 0x0010 0x0011

CAN Vehicle Chan-X Chan-Y Chan-Z 3D Vehicle Mode Status0 Status1

Config Attitude Grms Lvls Grms Lvls Grms Lvls G-Levels Pitch

Idle

Raw Sensor

Vibration

Spectrum

NOTE: Single Channel Only

Attitude

Pitch/Roll

Wheel Slip

J1939 PGN Offset1

0x0012 0x0014 0x001B 0x001C 0x001D 0x001E 0x001F 0xEFxx (Absolute)

3D Vehicle Vehicle VIM Mounting VIM Mounting Vehicle NV Config Vibration Mode GyroRates IDs Heading Rotation Matrix Position Drive Config Profile Spectrum

Idle

Raw Sensor

Vibration

Spectrum

Sing Chan

Attitude

Pitch/Roll

Wheel Slip

NOTES:

RO = Read-Only = Post Rotation Matrix Data BAM = Multi-Packet Broadcast Announce Message P2P = Multi-Packet Peer-to-Peer Message All multi-byte data is little endian unless otherwise specified


Vehicle Inertia Monitor (VIM) : Interface Document VIM Theory of Operation : Recommended Automated Rotation Matrix Calibration Procedure

The following section describes VIM calibration parameters and typical recommended procedures.

If accurate physical measurement of the VIM rotation angles is not practical, the recommended empirical calibration technique for generating the Rotation Matrix with the VIM mounted to the vehicle frame is outlined below. This Rotation Matrix translates the MEMS accelerometer and gyroscope data from the body frame to the inertial frame.

1) Put vehicle on a flat surface normal to the earth gravity vector 2) Toggle “Clear Rotation Matrix” (CLRR) bit to clear the Rotation Matrix 3) Toggle “Calculate Rotation Matrix” (CALCR) bit to perform first pass for calculation of Rotation Matrix 4) On installations where typical ψVIM > +/-5deg,.. continue 5) Move vehicle to pointing straight up on an inclined ramp with no roll 6) Step either “Increment” or “Decrement Yaw Mount Angle (ψVIM)” until the roll angle estimate reaches 0

• This step empirically generates an estimate for ψVIM 7) Move vehicle back to flat surface 8) Toggle “Calculate Rotation Matrix” (CALCR) bit to perform second pass for calculation of Rotation Matrix 9) Possibly repeat steps 5) thru 8) for better accuracy of Rotation Matrix

VIM Theory of Operation : Recommended Automated Left/Right Wheel Speeds Calibration Procedure

The recommended VIM empirical calibration technique for the L/R Speed Ratio while mounted to the vehicle is outlined below. This L/R Speed Ratio adapts for the actual difference between commanded left/right wheel speeds.

1) Put vehicle on a flat surface normal to the earth gravity vector 2) Toggle “Reset Yaw Calibration” (RSTCAL) bit to clear the L/R Speed Ratio 3) Drive vehicle carefully in straight line path at speed > 0.5 KPH 4) Set “Calibrate Yaw Angle” (CALYAW) bit to perform running estimate for the L/R Speed Ratio parameter

• This step computes a moving average window of the last 2 seconds for the L/R Speed Ratio 5) Clear “Calibrate Yaw Angle” (CALYAW) bit to stop running estimate for the L/R Speed Ratio parameter 6) Stop vehicle


Vehicle Inertia Monitor (VIM) : Interface Document VIM Theory of Operation : Pitch/Roll Estimates

The following section describes the VIM operation for vehicle pitch and roll estimates. Typical test results are shown for a small electric vehicle.

The VIM incorporates both a 3D MEMS accelerometer and 3D MEMS gyroscope. The data from both the accelerometer and gyroscope are fused together using a Kalman filter to generate dynamic pitch/roll estimates. The pitch estimate uses the longitudinal accelerometer and lateral gyroscope. The roll estimate uses the lateral accelerometer and longitudinal gyroscope.

A method is included to compensate for any gyroscope precessional motion. Before this compensation, a vehicle turning while going up/down hill would bleed it's pitch gyro into the roll estimate and a vehicle turning while off-camber would bleed it's roll gyro into the pitch estimate. The method uses a 2D plane based reference to perform the compensation.

The attitude estimate algorithms also incorporate a compensation scheme for vehicle frame accelerations using commanded motion parameters available on the CAN bus. If these compensations are not performed, any vehicle frame longitudinal/lateral accelerations directly affect the accelerometer output information and subsequent pitch/roll esimates. See the below example of the test vehicle driven in a Figure-8 pattern on a flat/level floor test area. The vehicle was driven at moderate speeds and turn-rates, however the estimated pitch/roll angles are blatantly inaccurate.

Attitude Estimates : Figure-8 Pattern : Kalman Filtered : Vehicle Frame Acceleration Compensation Disabled


Vehicle Inertia Monitor (VIM) : Interface Document VIM Theory of Operation : Pitch/Roll Estimates (cont)

With vehicle frame acceleration compensation enabled, the estimated attitude angles are greatly improved as depicted in the subsequent plot. It should be noted that the “flat/level” floor test area typically has small imperfections that equate to approx +/-1 degree typ. for the short wheelbase of the electric test vehicle. Therefore, the attitude estimates are not unreasonable for a dynamically moving vehicle frame.

Attitude Estimates : Figure-8 Pattern : Kalman Filtered : Vehicle Frame Acceleration Compensation Enabled


Vehicle Inertia Monitor (VIM) : Interface Document VIM Theory of Operation : Pitch/Roll Estimates (cont)

Typical Kalman filter processing results of the combined accelerometer and gyroscope data is shown in the below plot. The vehicle was originally facing up at the bottom of the test ramp. The vehicle was driven in Quantity-2 Figure-8 patterns on the ramp.

Notice that use of the accelerometer-only estimates (dashed lines) generate substantial noise even on the fairly smooth surface of the test ramp. The predictive Kalman filter provides a good level of filtering along with fairly quick responsiveness (solid lines) when referenced to the accelerometer-only data.

Attitude Estimates : Qty-2 Fig-8 Patterns : Kalman Filtered -vs- Accelerometer Only Vehicle Initially Facing Up at Bottom of 10-Degree Ramp

Vehicle Frame Acceleration Compensation Enabled

Use of standard digital IIR or FIR causal filters on the accelerometer-only data is possible and can also provide good levels of filtering, but at the cost of significantly longer attack/decay times and substantial group delays. The Kalman filter capitalizes on the additional fusion of the gyroscope pitch/roll rates to the accelerometer-only reference.




VIM Theory of Operation : Pitch/Roll Estimates (cont)

Similarily without vehicle frame acceleration compensation, attitude estimates on the 10-Degree ramp are significantly distorted. Notice how the combined lateral acceleration due to vehicle roll and gravity during turn-around at the top of the ramp attenuates the roll estimates at 8 seconds and 17.5 seconds. Additionally the roll estimates are amplified during the bottom of the ramp turn-around at 12.5 seconds and 22.5 seconds.

Attitude Estimates : Qty-2 Fig-8 Patterns : Kalman Filtered -vs- Accelerometer Only Vehicle Initially Facing Up at Bottom of 10-Degree Ramp

Vehicle Frame Acceleration Compensation Disabled

Documents

VIM Interface Document - · PDF fileVehicle Inertia Monitor (VIM) : Interface Document. SAE J1939 Parameter Group Numbers (PGNs) PGN . Offset1: Descrip . Byte: Data : Comments . RO