Vehicle steering system control based on a model-matching strategy

• US 6,738,699 B2
• Filed: 08/26/2002
• Issued: 05/18/2004
• Est. Priority Date: 08/26/2002
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Ashrafi, Behrouz, Yao, Yixin
• Primary Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US10/228,224
• Publication Number:
  US 20040039507A1
• Time in Patent Office: 631 Days
• Field of Search: 701/41, 701/42, 180/446, 180/402, 180/403, 180/421, 180/422
• US Class Current: 701/41
• CPC Class Codes: B62D 5/006 power actuated
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications

Abstract

A steer-by-wire control system that includes a road wheel actuation control system controlling road wheel angles to track a road wheel reference angle and a steering wheel control system producing a steering wheel angle to the road wheel actuation control system, steering feel for the vehicle driver and active steering wheel return. The steering wheel control system further including a steering wheel model matching controller that receives an input signal from the steering wheel control system and an input signal from the road wheel control system and generates a control output signal based on a model-matching control law, wherein the control output signal controls a reaction torque of the steering wheel control system to produce the steering feel for the driver and control the return rate of a steering wheel or a joystick.

Claims

1. A steer-by-wire control system, comprising:

a road wheel actuation control system controlling road wheel angles of a road wheel to track a road wheel reference angle;

a steering wheel control system producing a steering wheel angle for the road wheel actuation control system, steering feel for a vehicle driver and active steering wheel return;

said steering wheel control system further comprising a steering wheel model matching controller that receives an input signal from said steering wheel control system and an input signal from said road wheel control system and generates a control output signal based on a model-matching control law, wherein said control output signal controls reaction torque of said steering wheel control system to produce the steering feel for said vehicle driver and a return rate of a steering wheel or a joystick.

2. The steer-by-wire control system of claim 1, wherein said model matching controller is a two degrees of freedom controller.

3. The steer-by-wire control system of claim 2, wherein said input signal from said steering wheel control system represents a steering wheel angle and said input signal from said road wheel control system represents a road wheel torque.

4. The steer-by-wire control system of claim 3, wherein said model matching controller comprises:

a first controller element receiving a controller output signal representative of a steering wheel reaction torque signal applied at said steering wheel or joystick and generating a first controller output;

a second controller element receiving said steering wheel angle input signal representative of a position of said steering wheel and generating a second controller output; and

said first control output and said second control output are summed to form a controller feedback output signal that is fed to a summing junction to operate with a reference torque signal from a road wheel control system to provide said controller output signal of said model matching controller.

5. The steer-by-wire control system of claim 2, wherein said model matching controller decouples a reaction torque of said steering wheel control system from a return rate of said steering wheel or said joystick.

6. The steer-by-wire control system of claim 1, wherein said road wheel actuation control system receives said road wheel reference angle from said steering wheel control system and controls a direction of a vehicle.

7. The steer-by-wire control system of claim 1, wherein said steering wheel control system further comprises:

a steering wheel sensor connected to said steering wheel;

said steering wheel sensor sensing a steering wheel angle signal from said steering wheel; and

a steering wheel actuator connected to said steering wheel.

8. The steer-by-wire control system of claim 7, wherein said steering wheel, said steering wheel sensor, and said steering wheel actuator are connected to one another by a shaft.

9. The steer-by-wire control system of claim 8, wherein said shaft rotates.

10. The steer-by-wire control system of claim 7, wherein said steering wheel control system further comprises a motor amplifier that receives said control signal from said model matching controller and generates a reaction torque signal, τ

_c.

11. The steer-by-wire control system of claim 10, wherein said steering wheel actuator receives an effective torque signal, τ

_m, that is the sum of an equivalent external input torque signal, τ

_d, and said reaction torque signal, τ

_c, that is τ

_m=τ

_d−

τ

_c.

12. The steer-by-wire control system of claim 11, wherein said equivalent external input torque signal is generated during manual actuation of said steering wheel and said external input torque signal is regarded as an equivalent disturbance input signal to said steering wheel control system.

13. The steer-by-wire control system of claim 12, wherein said steering wheel control system rejects said equivalent external input torque signal, τ

_d, to produce said reaction torque signal, τ

_c, which a vehicle driver can feel when holding or turning said steering wheel.

14. The steer-by-wire control system of claim 1, wherein said road wheel actuation control system, comprises:

a road wheel sensor operably connected to said road wheel;

said road wheel sensor sensing a road wheel angle;

a road wheel actuator connected to said road wheel; and

a road wheel controller.

15. The steer-by-wire control system of claim 14, wherein said road wheel actuation control system further comprises a motor amplifier receiving a control signal from said road wheel controller of said road wheel actuation control system.

16. The steer-by-wire control system of claim 15, wherein said road wheel control system comprises:

a steering ratio element receiving said steering wheel angle input signal and generating a road wheel angle reference signal;

said road wheel controller receiving an error signal that is formed by subtracting a road wheel angle feedback signal from said road wheel reference angle signal, and said road wheel controller of said road wheel actuation control system sending a signal to said road wheel motor amplifier that generates a road wheel actuator control signal; and

a road wheel torque estimator receiving said a control signal of the road wheel control system and generating a road wheel torque reference signal.

17. A method of designing a steering wheel model matching controller using a model-matching strategy, comprising:

providing a reference steering dynamic model that defines a relationship between a steering wheel torque and a steering wheel angle;

providing a steering wheel control system with a model-matching controller;

supplying a steering wheel torque as an input for said reference steering dynamic model and said steering wheel control system;

generating a steering wheel angle as an output of said reference steering dynamic model;

generating a second steering wheel angle an output of said steering wheel control system;

matching said steering wheel control system and said reference steering dynamic model using minimization criterions in said model-matching control design; and

determining said model matching controller by minimizing an error between said reference steering model and said steering wheel control system.

18. The method of claim 17, wherein a control law of said model matching strategy is described by:

19. The method of claim 17, wherein said steering wheel control system is described by

20. The method of claim 17, wherein said reference steering model provides a relationship between a steering wheel torque applied to a steering wheel and a steering wheel angle of said steering wheel.

21. The method of claim 20, wherein said steering reference model is described by:

22. The method of claim 17, wherein said model matching control strategy comprises applying a model-matching criterion between transfer function M(s) of said reference steering model and a function H(s) of said steering wheel control system such that the following criterion is satisfied

23. The method of claim 17, further comprising performing a gain scheduling model-matching control strategy using different steering models to obtain model matching controller with adjustable gains.

24. The method of claim 23, where said gain scheduling model-matching control strategy comprises changing gains with a speed of a vehicle to compensate for changes in dynamics of said vehicle.

25. The method of claim 23, further comprising producing a variable steering feel by generating a required variable reaction torque at a steering wheel using said gain scheduling model-matching control strategy.

26. The method of claim 17, further comprising decoupling a reaction torque of a steering wheel or joystick from a return rate of said steering wheel or joystick and other steering functions.

27. The method of claim 17, further comprising tuning two tuning parameters of said model-matching controller independently of one another to satisfy a desired steering feel and steering wheel return rate for a steering wheel.