Dual gain algorithm for four wheel steering system

• US 6,640,172 B2
• Filed: 09/28/2001
• Issued: 10/28/2003
• Est. Priority Date: 08/01/2001
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust), Steering Solutions IP Holding Corporation (Nexteer Automotive Group Ltd.)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Wendling, Scott M., Klein, Steven Donald, Sebastian, Reeny
• Primary Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US09/966,722
• Publication Number:
  US 20030028301A1
• Time in Patent Office: 760 Days
• Field of Search: 701/41, 701/42, 701/43, 180/408, 180/410, 180/411, 180/412, 180/413, 180/422, 180/445
• US Class Current: 701/41
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A vehicle steering system coupled to a steerable wheel, comprising a steering rack linked to said steerable wheel, an electric motor having an output shaft engaged with the steering rack for controlling the steerable wheel. The system also includes a position sensor configured to measure an actual steerable wheel angle of the steering rack and thereby the steerable wheel, a return spring, where the return spring is biased so as to provide a returning force to the steering rack. Finally, the system includes a controller that provides a command to the electric motor resulting in a torque, the command is responsive to the actual steerable wheel angle, a desired steerable wheel angle, and a command direction.

Claims

1. A method for controlling an angle of a steerable wheel in a vehicle with electric power assisted steering with an electric motor and a return spring, comprising:

determining a desired steerable wheel angle;

obtaining an actual steerable wheel angle of said vehicle; and

determining a direction for said electric motor;

generating command, responsive to said desired steerable wheel angle, said actual steerable wheel angle, and said direction;

said command resulting in a torque generated by said electric motor operably connected to said steerable wheel for controlling said actual steerable wheel angle.

2. The method of claim 1 wherein said desired steerable wheel angle is responsive to a hand wheel angle and a vehicle speed.

3. The method of claim 2 wherein said desired steerable wheel angle is responsive to a ratio of said hand wheel angle scheduled as a function of said vehicle speed.

4. The method of claim 3 wherein said command is responsive to a servo error corresponding to a difference between said desired steerable wheel angle and said actual steerable wheel angle.

5. The method of claim 4 wherein said command is lower when said direction is with said return spring than when said direction against said return spring.

6. The method of claim 5 wherein said direction is against said return spring if:

said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle;

or

said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle; and

wherein said direction is with said return spring if;

said actual steerable wheel angle is greater than zero degrees and said desired steerable wheel angle is less than said actual steerable wheel angle;

or

said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

7. The method of claim 1 wherein said desired steerable wheel angle is a rear wheel angle, said desired steerable wheel angle responsive to a vehicle speed dependent ratio of a front wheel angle.

8. The method of claim 1 wherein said command is responsive to a servo error corresponding to a difference between said desired steerable wheel angle and said actual steerable wheel angle.

9. The method of claim 1, wherein said command is responsive to a look up process comprising a table with entries corresponding to said direction.

10. The method of claim 1, wherein said command is lower when said direction is with said return spring than when said direction is against said return spring.

11. The method of claim 1 wherein said direction is against said return spring, if said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle.

12. The method of claim 1 wherein said direction is with said return spring, if said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle.

13. The method of claim 1 wherein said direction is against said return spring if said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle.

14. The method of claim 1 wherein said direction is with said return spring, if said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

15. The method of claim 1 wherein said direction is against said return spring if:

said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle;

or

said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle; and

wherein said direction is with said return spring if;

said actual steerable wheel angle is greater than zero degrees and said desired steerable wheel angle is less than said actual steerable wheel angle;

or

said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

16. A vehicle steering system coupled to a steerable wheel, comprising:

a steering rack linked to said steerable wheel;

an electric motor having an output shaft engaged with said steering rack for controlling said steerable wheel;

a position sensor configured to measure an actual steerable wheel angle of said steering rack and thereby said steerable wheel, transmitting said actual steerable wheel angle to a controller;

a return spring, said return spring biased so as to provide a returning force to said steering rack; and

said controller providing a command to said electric motor resulting in a torque generated by said electric motor, said command responsive to said actual steerable wheel angle, a desired steerable wheel angle, and a direction of travel of said steerable wheel.

17. The vehicle steering system of claim 16 wherein said desired steerable wheel angle is responsive to a hand wheel angle and a vehicle speed.

18. The vehicle steering system of claim 17 wherein said desired steerable wheel angle is responsive to a ratio of said hand wheel angle scheduled as a function of said vehicle speed.

19. The vehicle steering system of claim 18 wherein said command is responsive to a servo error corresponding to a difference between said desired steerable wheel angle and said actual steerable wheel angle.

20. The vehicle steering system of claim 19, wherein said command is lower when said direction is with said return spring than when said direction is against said return spring.

21. The vehicle steering system of claim 20 wherein said direction is against said return spring if:

said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle;

or

said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle; and

wherein said direction is with said return spring if;

said actual steerable wheel angle is greater than zero degrees and said desired steerable wheel angle is less than said actual steerable wheel angle;

or

said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

22. The vehicle steering system of claim 16 wherein said desired steerable wheel angle is a rear wheel angle, said desired steerable wheel angle responsive to a vehicle speed dependent ratio of a front wheel angle.

23. The vehicle steering system of claim 16 wherein said command is responsive to a servo error corresponding to a difference between said desired steerable wheel angle and said actual steerable wheel angle.

24. The vehicle steering system of claim 16, wherein said command is responsive to a look up process comprising a table with entries corresponding to said direction.

25. The vehicle steering system of claim 16, wherein said command is lower when said direction is with said return spring than when said direction is against said return spring.

26. The vehicle steering system of claim 16 wherein said direction is against said return spring, if said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle.

27. The vehicle steering system of claim 16 wherein said direction is with said return spring, if said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle.

28. The vehicle steering system of claim 16 wherein said direction is against said return spring if said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle.

29. The vehicle steering system of claim 16 wherein said direction is with said return spring, if said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

30. The vehicle steering system of claim 16 wherein said direction is against said return spring if:

said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle;

or

said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle; and

wherein said direction is with said return spring if;

said actual steerable wheel angle is greater than zero degrees and said desired steerable wheel angle is less than said actual steerable wheel angle;

or

said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

31. A storage medium encoded with a machine-readable computer program code for controlling an angle of a steerable wheel in a vehicle with electric power assisted steering with an electric motor and a return spring, said storage medium including instructions for causing controller to implement a method comprising:

determining a desired steerable wheel angle;

obtaining an actual steerable wheel angle of said vehicle; and

determining a direction for said electric motor;

generating command, responsive to said desired steerable wheel angle, said actual steerable wheel angle, and said direction;

said command resulting in a torque generated by said electric motor operably connected to said steerable wheel for controlling said actual steerable wheel angle.

32. The storage medium of claim 31 wherein said desired steerable wheel angle is responsive to a hand wheel angle and a vehicle speed.

33. The storage medium of claim 32 wherein said desired steerable wheel angle is responsive to a ratio of said hand wheel angle scheduled as a function of said vehicle speed.

34. The storage medium of claim 33 wherein said command is responsive to a servo error corresponding to a difference between said desired steerable wheel angle and said actual steerable wheel angle.

35. The storage medium of claim 34, wherein said command is lower when said direction is with said return spring than when said direction against said return spring.

36. The storage medium of claim 35 wherein said direction is against said return spring if:

said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle;

or

said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle; and

wherein said direction is with said return spring if;

said actual steerable wheel angle is greater than zero degrees and said desired steerable wheel angle is less than said actual steerable wheel angle;

or

said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

37. The storage medium of claim 31 wherein said desired steerable wheel angle is a rear wheel angle, said desired steerable wheel angle responsive to a vehicle speed dependent ratio of a front wheel angle.

38. The storage medium of claim 31 wherein said command is responsive to a servo error corresponding to a difference between said desired steerable wheel angle and said actual steerable wheel angle.

39. The storage medium of claim 31, wherein said command is responsive to a look up process comprising a table with entries corresponding to said direction.

40. The storage medium of claim 31, wherein said command is lower when said direction is with said return spring than when said direction is against said return spring.

41. The storage medium of claim 31 wherein said direction is against said return spring, if said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle.

42. The storage medium of claim 31 wherein said direction is with said return spring, if said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle.

43. The storage medium of claim 31 wherein said direction is against said return spring if said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle.

44. The storage medium of claim 31 wherein said direction is with said return spring, if said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

45. The storage medium of claim 31 wherein said direction is against said return spring if:

said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle;

or

said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle; and

wherein said direction is with said return spring if;

said actual steerable wheel angle is greater than zero degrees and said desired steerable wheel angle is less than said actual steerable wheel angle;

or

said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

46. A computer data signal embodied in a carrier wave for controlling an angle of a steerable wheel in a vehicle with electric power assisted steering with an electric motor and a return spring, said data signal comprising code configured to cause a controller to implement a method comprising:

determining a desired steerable wheel angle;

obtaining an actual steerable wheel angle of said vehicle; and

determining a direction for said electric motor;

generating command, responsive to said desired steerable wheel angle, said actual steerable wheel angle, and said direction;

said command resulting in a torque generated by said electric motor operably connected to said steerable wheel for controlling said actual steerable wheel angle.

47. The computer data signal of claim 46 wherein said desired steerable wheel angle is responsive to a hand wheel angle and a vehicle speed.

48. The computer data signal of claim 47 wherein said desired steerable wheel angle is responsive to a ratio of said hand wheel angle scheduled as a function of said vehicle speed.

49. The computer data signal of claim 48 wherein said command is responsive to a servo error corresponding to a difference between said desired steerable wheel angle and said actual steerable wheel angle.

50. The computer data signal of claim 49 wherein said command is lower when said direction is with said return spring than when said direction against said return spring.

51. The computer data signal of claim 50 wherein said direction is against said return spring if:

said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle;

or

said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle; and

wherein said direction is with said return spring if;

said actual steerable wheel angle is greater than zero degrees and said desired steerable wheel angle is less than said actual steerable wheel angle;

or

said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

52. The computer data signal of claim 46 wherein said desired steerable wheel angle is a rear wheel angle, said desired steerable wheel angle responsive to a vehicle speed dependent ratio of a front wheel angle.

53. The computer data signal of claim 46 wherein said command is responsive to a servo error corresponding to a difference between said desired steerable wheel angle and said actual steerable wheel angle.

54. The computer data signal of claim 46, wherein said command is responsive to a look up process comprising a table with entries corresponding to said direction.

55. The computer data signal of claim 46, wherein said command is lower when said direction is with said return spring than when said direction is against said return spring.

56. The computer data signal of claim 46 wherein said direction is against said return spring, if said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle.

57. The computer data signal of claim 46 wherein said direction is with said return spring, if said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle.

58. The computer data signal of claim 46 wherein said direction is against said return spring if said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle.

59. The computer data signal of claim 46 wherein said direction is with said return spring, if said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.

60. The computer data signal of claim 46 wherein said direction is against said return spring if:

said actual steerable wheel angle is greater than zero degrees and if said desired steerable wheel angle is greater than said actual steerable wheel angle;

or

said actual steerable wheel angle is less than zero degrees and if said desired steerable wheel angle is less than said actual steerable wheel angle; and

wherein said direction is with said return spring if;

said actual steerable wheel angle is greater than zero degrees and said desired steerable wheel angle is less than said actual steerable wheel angle;

or

said actual rear wheel angle is less than zero degrees and if said desired rear wheel angle is greater than said actual rear wheel angle.