1. Active Steering Project Andrew Odhams Richard Roebuck David Cebon 2 nd April 2009

2. ContentsContents 1.Control concept 2.Low speed testing 3.High speed testing 4.Conclusions

3. ACTIVE STEERING –Define Lead point and follow point –Calculate articulation angle of a perfect tracking trailer –Steer in relation to difference between real and ideal articulation angle –Set individual wheel angles to equalise tyre forces Lead Point Follow Point Controller Low speed High speed Conclusions

4. PATH FOLLOWING TESTS UK Roundabout Test 5.3m 8.9m 11.25m 12.5m Controller Low speed High speed Conclusions

5. LOW SPEED ROUNDABOUT Unsteered: Controller Low speed High speed Conclusions

6. LOW SPEED ROUNDABOUT Command Steer: Controller Low speed High speed Conclusions

7. LOW SPEED ROUNDABOUT Offtracking of 5 th Wheel: Locked Command CVDC Controller Low speed High speed Conclusions

8. LOW SPEED ROUNDABOUT Offtracking of Trailer Rear: Locked Command CVDC Controller Low speed High speed Conclusions

9. LOW SPEED ROUNDABOUT Tail Swing: Locked Command Path Following Tail swings into blind spot Controller Low speed High speed Conclusions

10. Unsteered: LATERAL TYRE FORCES Controller Low speed High speed Conclusions

11. LATERAL TYRE FORCES Unsteered: FIXED TRAILER: 36.6 kN Controller Low speed High speed Conclusions

12. LATERAL TYRE FORCES Path following Strategy: CT-AT TRAILER: 6.1 kN Controller Low speed High speed Conclusions

13. Rollover Prevention Rationale –Reduce the risk of rollover by controlling the path of the trailer Optimal linear control strategy –Minimise lateral acceleration –Maintain acceptable path error Virtual Driver Model –Original path following controller is nonlinear –‘Virtual driver model’ performs same function using linear control Controller Low speed High speed Conclusions

14. Virtual Driver Model of Trailer Steering Tractor Semi-trailer Current position of 5 th wheel Y O X Snapshot of tractor semi-trailer and path of 5 th wheel at time instant k uT Controller Low speed High speed Conclusions

15. Optimal Control Strategy Discrete-time equations for vehicle and path of 5th wheel The control objectives where and The cost function Path errorLateral Accel’nSteering effort Controller Low speed High speed Conclusions

16. Results continued Manoeuvre: Lane change Vehicle speed: 88km/h Fixed value of Q1/R=0.05 Controller Low speed High speed Conclusions

17. Selection of weighting value Q2/R=0.005 Manoeuvre: Lane change Vehicle speed: 88km/h Fixed value of Q1/R=0.05 25% reduction Conventional Controller Low speed High speed Conclusions

18. Path errors in lane change Controller Low speed High speed Conclusions

19. After lane change V=88km/h LockedPath Following Control Controller Low speed High speed Conclusions

20. PERFORMANCE MEASURES Performance Measure Locked Comm. Steer PFCRSC High speed Transient Off- tracking [m] 0.35-0.150.31 Rearward Amplification 1.181.050.86 Controller Low speed High speed Conclusions Low speed Steady State Off- tracking [m] 4.31.61.2 Tail Swing (Entrance) [m] 0.170.610.0 Peak Tyre Force [kN] 36.65.36.1 Exit Settling Distance [m] 23.58.80.6

21. Conclusions Improved low-speed manoeuvrability –Improved productivity (LCV) –Improved safety Reduced tyre scrub –Reduced tyre wear –Reduced vehicle wear Improved high-speed stability –25% LTR reduction with no increase of PE –Important for LCV