4.26. Vehicle Dynamic State Estimator - VehDynStEstimr

• Overview

• Functions

• Ports

• Parameters

• Calibration

Id	VehDynStEstimr
Version	0.3.1.0
Title	Vehicle Dynamic State Estimator
System	Drivetrain
Document Type	Application Software Component Specification Preview

4.26.1. Overview

The Vehicle Dynamic State Estimator component estimates key vehicle dynamic states such as vehicle speed, acceleration, yaw rate, and tire slip angles. It uses sensor inputs such as wheel speeds, motor speeds, and inertial measurements to generate the state estimates. The component contains signal processing, sensor fusion algorithms, and Kalman filters to generate robust estimates of the vehicle states.

4.26.2. Functions

	Title	Description
1	Wheel Speed Processing	Processes the raw wheel speed sensor inputs, applies calibrations and filtering
2	Motor Speed Processing	Processes the raw motor speed sensor inputs, applies calibrations and filtering
3	Inertial Sensor Processing	Processes the raw inertial sensor inputs (accelerations, yaw rate), applies calibrations and filtering
4	Longitudinal Speed Estimation	Estimates the longitudinal vehicle speed using wheel speeds, motor speeds and inertial sensor inputs
5	Lateral Velocity Estimation	Estimates the lateral velocity of the vehicle using a Kalman filter that fuses inertial sensor inputs with a vehicle model
6	Tire Slip Angle Estimation	Estimates the tire slip angles using the estimated velocities and a tire model
7	Sensor Validity Monitoring	Monitors the validity and plausibility of the input sensor signals

4.26.3. Ports

	Id	Direction	Data Type	Dimensions	Unit	Description	Keywords
1	Ts	Incoming	single	[1]	s		Ts
2	MotAgrV	Incoming	int16	[4]	rpm	Expected signal: pre-processed Motor speed from inver (FL,FR,RL,RR) If signal is NA: mandatory.	Motor Angular Velocity
3	MotAgrVVld	Incoming	boolean	[4]		Expected signal: Motor speed from inverter signals validity (FL,FR,RL,RR) If signal is NA: mandatory. True	Motor Angular Velocity Valid
4	VehYawRate	Incoming	single	[1]	deg/s	Expected signal: pre-processed vehicle yaw rate If signal is NA: mandatory.	Vehicle Yaw Rate
5	VehYawRateVld	Incoming	boolean	[1]		Expected signal: pre-processed vehicle yaw rate signal validity If signal is NA: mandatory. True	Vehicle Yaw Rate Valid
6	VehLgtA	Incoming	single	[1]	m/s/s	Expected signal: pre-processed vehicle longitudinal acceleration If signal is NA: mandatory.	Vehicle Longitudinal Acceleration
7	VehLgtAVld	Incoming	boolean	[1]		Expected signal: pre-processed vehicles longitudinal acceleration signal validity If signal is NA: mandatory.	Vehicle Longitudinal Acceleration Valid
8	VehLatA	Incoming	single	[1]	m/s/s	Expected signal: pre-processed vehicles lateral acceleration If signal is NA: mandatory.	Vehicle Lateral Acceleration
9	VehLatAVld	Incoming	boolean	[1]		Expected signal: pre-processed vehicles lateral acceleration signal validity If signal is NA: mandatory. True	Vehicle Lateral Acceleration Valid
10	VehLgtSpd	Incoming	single	[1]	km/h	Expected signal: pre-processed vehicles longitudinal speed If signal is NA: mandatory	Vehicle Longitudinal Speed
11	VehLgtSpdVld	Incoming	boolean	[1]		Expected signal: pre-processed vehicles longitudinal speed signal validity If signal is NA: mandatory	Vehicle Longitudinal Speed Valid
12	RoadWhlAg	Incoming	single	[1]	deg	Expected signal: pre-processed road wheel angle from steering system If signal is NA: mandatory	Road Wheel Angle
13	RoadWhlAgVld	Incoming	boolean	[1]		Expected signal: pre-processed road wheel angle from steering system signal validity If signal is NA: mandatory. True	Road Wheel Angle Valid
14	WhlTracTqFb	Incoming	single	[4]	N*m	Expected signal: pre-processed wheel torque,i.e. feedback from inverter (FL,FR,RL,RR) If signal is NA: mandatory	Wheel Traction Torque Feedback
15	WhlTracTqFbVld	Incoming	boolean	[4]		Expected signal: pre-processed wheel torque signals validity, i.e. feedback from inverter (FL,FR,RL,RR) If signal is NA: mandatory. Ex True	Wheel Traction Torque Feedback Valid
16	WhlBrkTqFbIn	Incoming	single	[4]	N*m	Expected signal: pre-processing wheels braking torque feedback, i.e. inverter AND braking (FL,FR,RL,RR) If signal is NA: mandatory	Wheel Brake Torque Feedback In
17	WhlBrkTqFbVld	Incoming	boolean	[4]		Expected signal: pre-processing wheels braking torque feedback validity signals, i.e. inverter AND braking (FL,FR,RL,RR) If signal is NA: mandatory. Ex true	Wheel Brake Torque Feedback Valid
18	WhlAgrV	Incoming	single	[4]	rpm	Expected signal: pre-processing wheels speed signals, e.g. from braking system (FL,FR,RL,RR) If signal is NA: mandatory	Wheel Angular Velocity
19	WhlAgrVVld	Incoming	boolean	[4]		Expected signal: pre-processing wheels speed signals validity (FL,FR,RL,RR) If signal is NA: mandatory. Ex True	Wheel Angular Velocity Valid
20	VdseMotAgrV	Outgoing	single	[4]	rad/s		Vdse Motor Angular Velocity
21	VdseVehYawRate	Outgoing	single	[1]	deg/s		Vdse Vehicle Yaw Rate
22	VdseVehSlipAg	Outgoing	single	[1]	deg		Vdse Vehicle Slip Angle
23	VdseTyrSlipAgFrnt	Outgoing	single	[1]	deg		Vdse Tyre Slip Angle Front
24	VdseTyrSlipAgRe	Outgoing	single	[1]	deg		Vdse Tyre Slip Angle Rear
25	VdseVehLgtSpd	Outgoing	single	[1]	m/s		Vdse Vehicle Longitudinal Speed
26	VdseVehLgtA	Outgoing	single	[1]	m/s/s		Vdse Vehicle Longitudinal Acceleration
27	VdseVehLatA	Outgoing	single	[1]	m/s/s		Vdse Vehicle Lateral Acceleration
28	VdseWhlAgrV	Outgoing	single	[4]	rad/s		Vdse Wheel Angular Velocity
29	VdseWhlLgtSlip	Outgoing	single	[4]	1		Vdse Wheel Longitudinal Slip
30	VdseWhlVertF	Outgoing	single	[4]	N		Vdse Wheel Vertical Force
31	VdseRoadWhlAg	Outgoing	single	[1]	deg		Vdse Road Wheel Angle
32	VdseVehStStsTvc	Outgoing	boolean	[1]			Vdse Vehicle State Status Tvc
33	VdseVehStStsTcs	Outgoing	boolean	[1]			Vdse Vehicle State Status Tcs
34	VdseOut1	Outgoing	Bus: CAN_VdseOut1_t	[-1]	inherit		Vdse Output1
35	VdseOut1_send	Outgoing	boolean	[1]	inherit
36	VdseOut2	Outgoing	Bus: CAN_VdseOut2_t	[-1]	inherit		Vdse Output2
37	VdseOut2_send	Outgoing	boolean	[1]	inherit
38	VdseOut3	Outgoing	Bus: CAN_VdseOut3_t	[-1]	inherit		Vdse Output3
39	VdseOut3_send	Outgoing	boolean	[1]	inherit

4.26.4. Parameters

	Id	Data Type	Dimensions	Range	Unit	Description	Keywords
1	VdseWhlDrvTqFbOfs	single	[1,4]	Min: , Max:	N*m	Per wheel offset for traction torque preprocessing	Vdse Wheel Drive Torque Feedback Offset
2	VdseWhlDrvTqFbGain	single	[1,4]	Min: , Max:		Per wheel gain for traction torque preprocessing	Vdse Wheel Drive Torque Feedback Gain
3	VdseWhlBrkTqFbOfs	single	[1,4]	Min: , Max:	N*m	Per wheel offset for braking torque preprocessing	Vdse Wheel Brake Torque Feedback Offset
4	VdseWhlBrkTqFbGain	single	[1,4]	Min: , Max:		Per wheel gain for braking torque preprocessing	Vdse Wheel Brake Torque Feedback Gain
5	VdseALgtOfs	single	[1,1]	Min: -10000, Max: 10000	m/s/s	Pre-processing longitudinal acceleration offset	Vdse Acceleration Longitudinal Offset
6	VdseALgtGain	single	[1,1]	Min: -10000, Max: 10000		Pre-processing lateral acceleration gain	Vdse Acceleration Longitudinal Gain
7	VdseALatOfs	single	[1,1]	Min: -10000, Max: 10000	m/s/s	Pre-processing lateral acceleration offset	Vdse Acceleration Lateral Offset
8	VdseALatGain	single	[1,1]	Min: -10000, Max: 10000		Pre-processing longitudinal acceleration gain	Vdse Acceleration Lateral Gain
9	VdseAInSwap	boolean	[1,1]	Min: , Max:		Swap incoming lgt and lat acceleration signals	Vdse Acceleration In Swap
10	VdseWhlAgDmdGain	single	[1,1]	Min: -10000, Max: 10000		Pre-processing wheel angle demand gain	Vdse Wheel Angle Demand Gain
11	VdseWhlAgDmdOfs	single	[1,1]	Min: -10000, Max: 10000	deg	Pre-processing wheel angle demand offset	Vdse Wheel Angle Demand Offset
12	VdseCkfNlnrMeasmLutBrkPnt	single	[1,16]	Min: , Max:		CKF R matrix adaptation law - lut breakpoints	Vdse Ckf Nonlinear Measurement Lut Brake Point
13	VdseCkfNlnrMeasmLutVal	single	[1,16]	Min: , Max:		CKF R matrix adaptation law - lut data	Vdse Ckf Nonlinear Measurement Lut Value
14	VdseCkfRmtrxTyrLgtF	single	[1,1]	Min: 0, Max: 500000		Longtidunal kalman filter R matrix: Wheel speed	Vdse Ckf Rmtrx Tyre Longitudinal Force
15	VdseRoadWhlAgOfsErrChkEna	boolean	[1,1]	Min: , Max:		TRUE to enable error if road wheel angle offset is above threshold	Vdse Road Wheel Angle Offset Error Check Enable
16	VdseRoadWhlOfsLim	single	[1,1]	Min: 0.001, Max: 0.1	rad	Maximum steering offset value produced by curvature kalman filter	Vdse Road Wheel Offset Limit
17	VdseTurnOnRoadWhlAgOfsEstimr	boolean	[1,1]	Min: , Max:		True to turn on Kalman filter for road wheel angle offset estimation. It doesn’t automatically add offset to road wheel angle signal. Use VehStUseRoadWhlAgOfsEstimr for that	Vdse Turn On Road Wheel Angle Offset Estimator
18	VdseUseRoadWhlAgOfsEstimr	boolean	[1,1]	Min: , Max:		True to use road wheel angle offset estimator	Vdse Use Road Wheel Angle Offset Estimator
19	VdseUseVLgtEstimr	boolean	[1,1]	Min: , Max:		TRUE to activate longitudinal speed estimation based on WSS + IMU. FALSE to use external VLgt source	Vdse Use Velocity Longitudinal Estimator
20	VdseCkfQmtrxSt	single	[5,5]	Min: 0, Max: 500000		StEst kalman filter Q matrix, diagonal, VLgt, VLgt, YawRate, Cornering Stiffness Frnt, Cornerin Stiffness Re. Lower values mean more confidence in dynamic model and vehicle parameters.	Vdse Ckf Qmtrx State
21	VdseCkfRmtrxSt	single	[3,3]	Min: 0, Max: 500000		StEst kalman filter R matrix, ALgt, ALat, YawRate. Lower values mean more confidence for this measurement quality	Vdse Ckf Rmtrx State
22	VdseCkfQmtrxTyrLgtF	single	[2,2]	Min: 0, Max: 500000		Longtidunal kalman filter Q matrix, Wheel speed, Longitudinal Tyre Force	Vdse Ckf Qmtrx Tyre Longitudinal Force
23	VdseCkfStfnFrnt	single	[1,1]	Min: 0, Max: 1000000000		Approximate cornering stiffness of the front tyre	Vdse Ckf Stiffness Front
24	VdseCkfStfnRe	single	[1,1]	Min: 0, Max: 1000000000		Approximate cornering stiffness of the rear tyre	Vdse Ckf Stiffness Rear
25	VdseYawRateOfs	single	[1,1]	Min: -500, Max: 500	deg/s	Vehicle state yaw rate offset	Vdse Yaw Rate Offset
26	VdseCurvCompALatSteerThd	single	[1,1]	Min: 0, Max: 15	1/R	Threshold to compare curvature values from different sources: for RWA and Wheel based	Vdse Curvature Comparison Acceleration Lateral Steering Threshold
27	VdseCurvCompChkALat	boolean	[1,1]	Min: , Max:		True to turn on comparisons with ALat for curvature plausability check	Vdse Curvature Comparison Check Acceleration Lateral
28	VdseCurvCompEna	boolean	[1,1]	Min: , Max:		Enable curvature signal comparison	Vdse Curvature Comparison Enable
29	VdseCurvCompThdYawSteer	single	[1,1]	Min: 0, Max: 15	1/R	Threshold to compare curvature values from different sources: for RWA and YawRate	Vdse Curvature Comparison Threshold Yaw Steering
30	VdseCurvCompTiToChk	single	[1,1]	Min: 0, Max: 100	s	Time to raise bad quality flag for curvature comparison issues	Vdse Curvature Comparison Time To Check
31	VdseCurvCompTiToChkOut	single	[1,1]	Min: 0, Max: 100	s	Time to release bad quality flag for curvature comparison issues once signals are ok	Vdse Curvature Comparison Time To Check Output
32	VdseCurvCompVLgtThd	single	[1,1]	Min: 0, Max: 50	m/s	Minimum velocity to start curvature comparison with RWA	Vdse Curvature Comparison Velocity Longitudinal Threshold
33	VdseCurvCompYawALatThd	single	[1,1]	Min: 0, Max: 15	1/R	Threshold to compare curvature values from different sources: for YawRate nad Wheel Based	Vdse Curvature Comparison Yaw Acceleration Lateral Threshold
34	VdseSndCanOut1	boolean	[1,1]	Min: , Max:		True to send diagnostic message 1 for Vdse	Vdse Send Can Output1
35	VdseSndCanOut2	boolean	[1,1]	Min: , Max:		True to send diagnostic message 2 for Vdse	Vdse Send Can Output2
36	VdseSndCanOut3	boolean	[1,1]	Min: , Max:		True to send diagnostic message 3 for Vdsev	Vdse Send Can Output3
37	VdseYawRateSrc	uint8	[1,2]	Min: 1, Max: 100		Vehicle state yaw rate source	Vdse Yaw Rate Source
38	VdseYawRateGain	single	[1,1]	Min: -10000, Max: 10000		Pre-processing yaw rate gain	Vdse Yaw Rate Gain
39	VdseWhlSlipChkTiDly	single	[1,1]	Min: , Max:	s	Delay for reset of wheel slip check	Vdse Wheel Slip Check Time Delay
40	VdseWhlSpdErrChkAcv	boolean	[1,4]	Min: , Max:		Use validity flag to switch between measurements and CKF based estimation of wheel speeds	Vdse Wheel Speed Error Check Active
41	VdseWhlSpdSrcErrTi	single	[1,1]	Min: 0, Max: 100	s	Wheel speed error ignore time	Vdse Wheel Speed Source Error Time
42	VdseWhlSlipChkSpdThd	single	[1,1]	Min: , Max:	m/s	Wheel speed threshold to enable slip check	Vdse Wheel Slip Check Speed Threshold
43	VdseWhlSlipChkOnThd	single	[1,1]	Min: , Max:		Slip value to enable slip checking	Vdse Wheel Slip Check On Threshold
44	VdseWhlSlipChkOffThd	single	[1,1]	Min: , Max:		Slip value to disable slip checking	Vdse Wheel Slip Check Off Threshold
45	VdseWhlSlipChkChgThd	single	[1,1]	Min: , Max:		Maximum change in wheel slip to activate wheel slip check	Vdse Wheel Slip Check Change Threshold
46	VdseWhlSlipChk	boolean	[1,1]	Min: , Max:		True to enable additional checks of wheel slip calculation in case of big derivative	Vdse Wheel Slip Check
47	VdseWhlLgtSlipSrc	uint8	[1,2]	Min: 1, Max: 100		Vehicle state wheel slip source	Vdse Wheel Longitudinal Slip Source
48	VdseWhlAgrVSrc	uint8	[1,2]	Min: 1, Max: 100		Vehicle state wheel speed source	Vdse Wheel Angular Velocity Source
49	VdseSlipAgSrc	uint8	[1,1]	Min: 1, Max: 100		Vehicle state slip angle source	Vdse Slip Angle Source
50	VdseMotSpdSrc	uint8	[1,1]	Min: 1, Max: 100		Vehicle state motor speed source	Vdse Motor Speed Source
51	VdseLgtSpdSrc	uint8	[1,2]	Min: 1, Max: 100		Vehicle state longitudinal speed source	Vdse Longitudinal Speed Source
52	VdseLgtASrc	uint8	[1,1]	Min: 1, Max: 100		Vehicle state longitudinal acceleration source	Vdse Longitudinal Acceleration Source
53	VdseLatASrc	uint8	[1,1]	Min: 1, Max: 100		Vehicle state lateral acceleration source	Vdse Lateral Acceleration Source
54	VdseCkfStAdpvBound	single	[2,5]	Min: -500000, Max: 500000		Internal boundaries for CKF points propagation	Vdse Ckf State Adaptive Bound
55	VdseCkfStIniVal	single	[1,5]	Min: 0, Max: 5000000		Initial conditions for main CKF	Vdse Ckf State Initial Value
56	VdseCurvEstimrFilgCoeff	single	[1,1]	Min: 0, Max: 1		Smoothness parameter for curvature estimator (unitless)	Vdse Curvature Estimator Filtering Coefficient
57	VdseCurvEstimrIniCov	single	[2,2]	Min: -1, Max: 1		Initial model covariance matrix for curvature estimator (unitless)	Vdse Curvature Estimator Initial Covariance
58	VdseCurvEstimrInpCov	single	[2,2]	Min: -1, Max: 1		Disturbance covariance matrix for curvature estimator (unitless)	Vdse Curvature Estimator Input Covariance
59	VdseCurvEstimrNoiseCov	single	[2,2]	Min: -1, Max: 1		Covariance of observation noise for curvature estimator (unitless)	Vdse Curvature Estimator Noise Covariance
60	VdseCurvEstimrTolrThd	single	[1,1]	Min: 0.0001, Max: 0.5	1/m	Threshold of admissible difference between road wheel angle based curvature and estimated curvature	Vdse Curvature Estimator Tolerance Threshold
61	VdseCurvEstimrVThd	single	[1,1]	Min: 0.001, Max: 50	m/s	Velocity threshold for curvature estimator	Vdse Curvature Estimator Velocity Threshold
62	VdseRoadWhlAgDmdVldyOvrd	boolean	[1,1]	Min: , Max:		Road wheel angle validity flag override	Vdse Road Wheel Angle Demand Validity Override
63	VdseTyrSlipAgFrntSrc	uint8	[1,2]	Min: 1, Max: 100		Vehicle state front tyre slip angle source	Vdse Tyre Slip Angle Front Source
64	VdseVertFLoSatn	single	[1,1]	Min: , Max:	N	Low limit for vertical forces estimation	Vdse Vertical Force Low Saturation
65	VdseMotSpdGain	single	[1,4]	Min: , Max:		Pre-processing motor speed gain, FrntLe, FrntRi, ReLe, ReRi	Vdse Motor Speed Gain
66	VdseWhlSpdGain	single	[1,4]	Min: -10000, Max: 10000		Pre-processing FR wheel speed gain FrntLe, FrntRi, ReLe, ReRi	Vdse Wheel Speed Gain
67	VdseWhlSpdOfs	single	[1,4]	Min: -10000, Max: 10000	km/h	Pre-processing front wheel speed offset FrntLe, FrntRi, ReLe, ReRi	Vdse Wheel Speed Offset
68	VdseRoadWhlAgOfsErrThdMin	single	[1,1]	Min: , Max:	rad	Min threshold to use to raise an error if estimated road wheel angle offset is too high	Vdse Road Wheel Angle Offset Error Threshold Minimum
69	VdseRoadWhlAgOfsVLgtMin	single	[1,1]	Min: , Max:	m/s	Minimum longitudinal velocity tuning parameter for calculating a threshold to raise RWA offset error flag using formula Thd = ALat*WheelBase/V^2	Vdse Road Wheel Angle Offset Velocity Longitudinal Minimum
70	VdseRoadWhlAgOfsErrThdMax	single	[1,1]	Min: , Max:	rad	Max threshold to use to raise an error if estimated road wheel angle offset is too high	Vdse Road Wheel Angle Offset Error Threshold Maximum
71	VdseRoadWhlAgOfsALat	single	[1,1]	Min: 2, Max: 12	m/s/s	Lateral acceleration tuning parameter for calculating a threshold to raise RWA offset error flag using formula Thd = ALat*WheelBase/V^2	Vdse Road Wheel Angle Offset Acceleration Lateral

4.26.5. Calibration

VehDynStEstimr performs estimation of the vehicle states based on a set of vehicle parameters and a number of input signals using a dual Kalman filter estimator with a tire model-less approach, which reduces the need for an extensive number of tire parameters. VehDynStEstimr also allows for the estimation of Road Wheel Angle offset and performs a Curvature Plausibility Check. The most important configuration parameters are covered here.

4.26.5.1. Step 1 - Connect input signals

All input signals are mandatory for the proper functionality of the component.

4.26.5.2. Step 2 - Configure input signal preprocessing

Use the parameters from the Preprocessing group to specify the offsets and gains of all input signals. For example, this can be helpful for changing the signs of input signals from different sources.

4.26.5.3. Step 3 - Configure vehicle parameters

The most important aspect of the estimation is setting up the vehicle parameters as accurately as possible to match the real vehicle. Check all parameters with the Vehprm prefix, with special focus on: VehprmVehCogDstFromAxleFrnt, VehprmVehCogDstFromAxleRe, VehprmTyrEfcRollgRdFrnt, VehprmTyrEfcRollgRdRe, VehprmVehM, VehprmVehYawMomJ, VehprmVehTrkWidthFrnt, VehprmVehTrkWidthRe. These parameters have the greatest impact on the quality of the estimation. Aerodynamic and suspension-related parameters usually have less impact on the quality of the estimation, so precise calibration of these is typically unnecessary.

4.26.5.4. Step 4 - Configure cornering stiffness parameters

The parameters VdseCkfStfnFrnt and VdseCkfStfnRe should be calibrated based on the typical cornering stiffness of the vehicle’s tires under normal conditions. The estimator uses these parameters to adjust internal states and improve the estimation when the vehicle exhibits high lateral acceleration, operating in the nonlinear region of the tire’s performance.

4.26.5.5. Step 5 - Configure road wheel angle offset estimator

Set VdseTurnOnRoadWhlAgOfsEstimr and VdseUseRoadWhlAgOfsEstimr to true to enable and use the Road Wheel Angle offset estimation. This will perform slight compensation of the Road Wheel Angle input signal if the sensor calibration is not perfect. Configure the maximum compensation limit using the VdseRoadWhlOfsLim parameter.

4.26.5.6. Step 6 - Curvature plausibility check

Set VdseCurvCompEna to true to enable the curvature plausibility check. This helps detect issues with input signals that may not be in sync regarding magnitude and sign convention. The curvature plausibility check must pass (or be enabled) for Outport #13: VdseVehStStsTvc to be valid.

4.26.5.7. Step 7 - Longitudinal velocity estimation

Set VdseUseVLgtEstimr to true to enable the internal algorithm for vehicle longitudinal speed estimation. However, use this option only if no robust external source of the signal is available, such as from the braking system sensor. The internal algorithm may not perform well under complex conditions.

4.26.5.8. Step 8 - Advanced tuning

Use the following set of parameters if advanced tuning is required: VdseCkfQmtrxSt, VdseCkfQmtrxTyrLgtF, VdseCkfRmtrxSt, VdseCkfRmtrxTyrLgtF.

Advanced tuning is recommended only if you are confident that all other calibrations have been completed correctly and you aim to gain extra performance in complex situations. Advanced tuning can be performed on the parameters of the dual Kalman filter schema for each stage. In general, lower values of the diagonal matrices correspond to more confidence in the quality of the vehicle parameters (for Q) and precision of the sensors (for R). The most important parameter here is the last element of the VdseCkfQmtrxSt matrix, which specifies how quickly the adaptation of cornering stiffness occurs when the vehicle experiences high accelerations.