TYRE STATE ESTIMATION. Antoine Schmeitz, Arjan Teerhuis, Laura van de Molengraft-Luijten

Transcription

1 Antoine Schmeitz, Arjan Teerhuis, Laura van de Molengraft-Luijten

2 CONTENTS Introduction Experimental setup Basic shape model Tyre state estimator Results Concluding remarks Next steps

3 INTRODUCTION Intelligent tyre systems under development for more than a decade Basic principle: Measuring tyre deformation and relate it to tyre states: forces, slip angle, camber angle,... Sensors: strain, acceleration, distance, Most promising solution: accelerometer at the tyre inner liner Feature extraction algorithms to estimate tyre states Robustness issues (noise, outliers)

4 INTRODUCTION Objective of this study: development of a Tyre State Estimator (TSE), which is more robust for: noisy signals combined inputs occurring on real vehicles while driving and: can be easily fused with other on vehicle sensors in a Vehicle State Estimator (VSE) Idea / approach: Model based estimator using the Extended Kalman Filter (EKF) Focus first on vertical load estimation

5 EXPERIMENTAL SETUP Measurements Radial acceleration Symbol Description Wheel speed Sensor position angle Sensor radius Forward velocity Radial acceleration 0

6 EXPERIMENTAL SETUP Tyre Test Trailer: force & moment measuring hub i-tire: accelerometer

7 EXPERIMENTAL SETUP Measurement program Calibration measurements steady-state conditions constant velocity and vertical load Validation measurements changing vertical load at constant velocity changing velocity at constant vertical load changing both velocity and vertical load

8 EXPERIMENTAL SETUP measurement results low/high velocity low/high load grey dots: results 10 revolutions red line: averaged results piezoelectric accelerometer: outside deformed area signal is zero

9 BASIC SHAPE MODEL Empirical model to describe the shape of the acceleration signal 1" 1 2 "1 2 tanh ( ) *+,-. 1

10 BASIC SHAPE MODEL Basic shape function: 1" 1 2 "1 2 tanh ( coefficients C 1 to C 6 are identified from measurements ) *+,-. 1 Relations for parameters: / 0 ( " "1 0 ( "1 5 Thus: 7,,9

11 TYRE STATE ESTIMATOR (TSE) Model :,,0 is nonlinear Measurements are noisy F z is unknown parameter, measured / calculated Model highly nonlinear in Extended Kalman Filter (EKF), but removed from the estimation process Simulink implementation (4000 Hz), PS (peak synchronization) VLO Vertical Load Observer 0

12 TSE: PS Assumption: symmetry about,, ENABLE_TSE each time-step: Integrate input : / "< = For peak-detection: " " Initialization: / 0, 0 ENABLE_TSE=0 contact patch centre?? NO / Condition: YES F F =AB 0 =AB peak location: =AB =AB C BDE? NO / =AB 0, 0 ENABLE_TSE=0 YES ENABLE_TSE=1

13 TYRE STATE ESTIMATOR PEAK SYNCHRONISATION

14 TSE: VERTICAL LOAD OBSERVER Extended Kalman Filter (EKF) 0 = M M N,,0 M O, IJK prediction (model) 0 IJK " ) BL= (P Q < NQP Q < "O 1 0 M )RS 0 M TU)V "() W)R PNX(QOP correction (EKF) 0 = BL=

15 RESULTS: EXAMPLE 1 Conditions: Constant vertical load of 5 kn Constant forward velocity of 60 km/h Initial F z estimate deliberately set to 10 kn

16 RESULTS: EXAMPLE 1

17 RESULTS: EXAMPLE 2 5y5y

18 CONCLUDING REMARKS Empirical basic shape model presented that describes radial acceleration Tyre State Estimator developed to estimate the tyre vertical load: Peak Synchronisation Vertical Load Observer (EKF) Accurate vertical load estimation in cases of constant and changing vertical load and forward velocity Fast estimator convergence capabilities for cases when: initial vertical load or sensor position unknown moving away from situations in which signal to noise ratio is poor, i.e. at low velocities and low vertical loads

19 NEXT STEPS Current vertical load TSE Assessment of accuracy and robustness for more operating conditions (e.g. braking, side slip, combined slip) Prove real-time capability In-vehicle demonstrator TSE development: Extending towards more tyre states: side slip angle, camber angle, lateral force, longitudinal force, etc. Looking for / realising applications of the i-tire technology

20 THANK YOU FOR YOUR ATTENTION