Velocity compensation control for electric steering systems

• US 20040162655A1
• Filed: 06/07/2002
• Published: 08/19/2004
• Est. Priority Date: 06/08/2001
• Status: Active Grant

• 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: Patankar, Ravindra P.
• Granted Patent: US 7,188,701 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/0472 for damping vibrations

Abstract

Disclosed herein is a method as well as a system for controlling an electric power steering system. The method includes: receiving a torque signal from a torque sensor responsive to a torque applied to a steering wheel; obtaining a motor velocity signal, the motor velocity signal indicative of a speed of an electric motor which applies torque to a steerable wheel; and generating a command for said electric motor with a controller coupled to the torque sensor, and the electric motor. The command includes torque control and motor velocity compensation, responsive to at least one of the torque signal, and a motor velocity signal. Also disclosed herein is a storage medium encoded with a computer program code for controlling an electric power steering system, the storage medium includes instructions for causing controller to implement the disclosed method. Further disclosed is a computer data signal for controlling an electric power steering system, the data signal comprising code configured to cause a controller to implement the disclosed method. Additionally, a method for optimizing controlling torque in an electric power steering system is disclosed. The method including: receiving a torque signal responsive to a torque applied to a steering wheel; obtaining a motor velocity; generating a command with a controller for the electric motor, where the command includes a torque control and motor velocity compensation, responsive to the torque signal, and the motor velocity. The performance of the torque control is responsive to a torque compensator, a high pass low pass structure, and motor velocity compensation.

Claims

1. An electric power steering control system incorporating motor velocity compensation comprising:

an electric motor disposed in a vehicle to apply torque to a steerable wheel;

a torque sensor disposed in said vehicle for detecting a steering wheel torque and generating a torque signal indicative thereof;

a controller coupled to said torque sensor, and said electric motor;

wherein said controller generates a command to said electric motor for torque control, which includes said motor velocity compensation and said command responsive to at least one of said torque signal, and a motor velocity.

2. The system of claim 1 further including a vehicle speed sensor, said vehicle speed sensor generating a vehicle speed signal and electrically connected to said controller wherein said command is also responsive to said vehicle speed signal.

3. The system of claim 1 wherein said motor velocity is generated by a motor velocity sensor electrically connected to said controller and transmitting a motor velocity signal thereto.

4. The system of claim 1 wherein said motor velocity is derived from a position sensor disposed in said vehicle configured to detect a position indicative of a position of said steerable wheel and generating a position signal.

5. The system of claim 1 wherein said command includes a voltage command responsive to a combined command and said motor velocity signal.

6. The system of claim 5 wherein said combined command results from a summation of a torque command and a compensated motor velocity, said compensated motor velocity the resultant of said motor velocity compensation comprising a frequency based filter acting on said motor velocity signal.

7. The system of claim 1 wherein said motor velocity compensation is configured to maintain stability of said torque control of said electric power steering system.

8. The system of claim 7 wherein said motor velocity compensation is configured to enhance performance of said torque control of said electric power steering system.

9. The system of claim 8 wherein said enhance performance of said torque control of said electric power steering system comprises at least one of:

an increase of velocity disturbance rejection;

an increase of torque disturbance rejection;

maintenance of steering wheel input impedance as substantially flat for low frequencies and increasing for higher frequencies thereafter.

10. The system of claim 8 wherein said motor velocity compensation is configured to characterize on-center feel of said torque control of said electric power steering system.

11. The system of claim 1 wherein said motor velocity compensation is configured to enhance performance of said torque control of said electric power steering system.

12. The system of claim 11 wherein said enhance performance of said torque control of said electric power steering system comprises at least one of:

an increase of velocity disturbance rejection;

an increase of torque disturbance rejection;

maintenance of steering wheel input impedance as substantially flat for low frequencies and increasing for higher frequencies thereafter.

13. The system of claim 12 wherein said motor velocity compensation is configured to characterize on-center feel of said torque control of said electric power steering system.

14. The system of claim 6 wherein said frequency based filter comprises at least one pole.

15. The system of claim 6 wherein said frequency based filter comprises at least one zero.

16. The system of claim 6 wherein said frequency based filter comprises at least one pole and at least one zero.

17. The system of claim 6 wherein said frequency based filter comprises a pole placed at about 12 Hertz and a zero placed at about zero Hertz.

18. The system of claim 6 wherein said motor velocity compensation further includes a schedulable gain.

19. The system of claim 6 wherein said torque command is a resultant of a high pass low pass structure, said high pass low pass structure responsive to a compensated torque signal, said compensated torque signal the resultant of a torque compensator.

20. The system of claim 19 wherein said torque compensator comprises a frequency based notch filter configured to maintain stability of a torque control of said electric power steering system.

21. The system of claim 19 wherein said high pass low pass structure comprises a high frequency path including a high pass gain and a low frequency path including a low pass gain.

22. The system of claim 21 wherein said high frequency path is configured to control torque disturbance rejection of said electric power steering system.

23. The system of claim 21 wherein said low frequency path is configured to control steady state torque response of said electric power steering system.

24. A method of controlling an electric power steering system, the method comprising:

receiving a torque signal responsive to a torque applied to a steering wheel;

obtaining a motor velocity signal, said motor velocity signal indicative of a speed of an electric motor; and

generating a command for said electric motor, said command including torque control and motor velocity compensation, responsive to at least one of said torque signal, and a motor velocity signal.

25. The method of claim 24 wherein said torque signal is generated by a torque sensor electrically connected to said controller.

26. The method of claim 24 further including receiving a vehicle speed signal generated by a vehicle speed sensor electrically connected to said controller, and wherein said command also responsive to said vehicle speed signal.

27. The method of claim 24 wherein said motor velocity signal is generated by a motor velocity sensor electrically connected to said controller and transmitting a motor velocity signal thereto.

28. The method of claim 24 wherein said motor velocity signal is derived from a position sensor disposed in said vehicle configured to detect a steering position indicative of a position of said steerable wheel and generating a position signal.

29. The method of claim 24 wherein said command includes a voltage command responsive to a combined command and said motor velocity signal.

30. The method of claim 29 wherein said combined command is a result of a summation of a torque command and a compensated motor velocity, said compensated motor velocity the resultant of said motor velocity compensation comprising a frequency based filter acting on said motor velocity signal.

31. The method of claim 24 wherein said motor velocity compensation is configured to maintain stability of said torque control of said electric power steering system.

32. The method of claim 31 wherein said motor velocity compensation is configured to enhance performance of said torque control of said electric power steering system.

33. The method of claim 32 wherein said enhance performance of said torque control of said electric power steering system comprises at least one of:

an increase of velocity disturbance rejection;

an increase of torque disturbance rejection;

maintenance of steering wheel input impedance as substantially flat for low frequencies and increasing for higher frequencies thereafter.

34. The method of claim 32 wherein said motor velocity compensation is configured to characterize on-center feel of said torque control of said electric power steering system.

35. The method of claim 24 wherein said motor velocity compensation is configured to enhance performance of said torque control of said electric power steering system.

36. The method of claim 35 wherein said enhance performance of said torque control of said electric power steering system comprises at least one of:

an increase of velocity disturbance rejection;

an increase of torque disturbance rejection;

maintenance of steering wheel input impedance as substantially flat for low frequencies and increasing for higher frequencies thereafter.

37. The method of claim 36 wherein said motor velocity compensation is configured to characterize on-center feel of said torque control of said electric power steering system.

38. The method of claim 30 wherein said frequency based filter comprises at least one pole.

39. The method of claim 30 wherein said frequency based filter comprises at least one zero.

40. The method of claim 30 wherein said frequency based filter comprises at least one pole and at least one zero.

41. The method of claim 30 wherein said frequency based filter comprises a pole placed at 12 Hertz and a zero placed at zero Hertz.

42. The method of claim 30 wherein said motor velocity compensation further includes a schedulable gain.

43. The method of claim 30 wherein said torque command is a resultant of a high pass low pass structure, said high pass low pass structure responsive to a compensated torque signal, said compensated torque signal the resultant of a torque compensator.

44. The method of claim 43 wherein said torque compensator comprises a frequency based notch filter configured to maintain stability of a torque control of said electric power steering system.

45. The method of claim 43 wherein said high pass low pass structure comprises a high frequency path including a high pass gain and a low frequency path including a low pass gain.

46. The method of claim 45 wherein said high frequency path is configured to control torque disturbance rejection of said electric power steering system.

47. The method of claim 45 wherein said low frequency path is configured to control steady state torque response of said electric power steering system.

48. A method for optimizing controlling torque in an electric power steering system, the method comprising:

receiving a torque signal responsive to a torque applied to a steering wheel;

obtaining a motor velocity signal;

generating a command with a controller for said electric motor, said command including torque control and motor velocity compensation, responsive to at least one of said torque signal and said motor velocity signal; and

wherein performance of said torque control is responsive to at least one of a torque compensator, a high pass low pass structure, and said motor velocity compensation.

49. The method of claim 48 wherein said controlling includes adjusting performance of said torque control of said electric power steering system by selecting a schedulable gain for said motor velocity compensation at least sufficient to achieve stability of said electric power steering system, while said torque compensator and said high pass low pass structure are disabled.

50. The method of claim 48 wherein said controlling includes adjusting performance of said torque control of said electric power steering system by evaluating on-center feel characteristics of said performance and reducing a schedulable gain for said motor velocity compensation when said commands are low to achieve acceptable on-center feel characteristics.

51. The method of claim 48 wherein said controlling includes adjusting performance of said torque control of said electric power steering system by increasing a high pass gain for said high pass low pass structure including an appropriate cut-off frequency for a low pass filter to achieve stability of said torque control of said electric power steering system.

52. The method of claim 48 wherein said controlling includes adjusting performance of said torque control of said electric power steering system by incorporating said torque compensator at a depth sufficient to achieve stability.

53. The method of claim 48 wherein said controlling includes improving performance of said torque control of said electric power steering system by:

selecting a schedulable gain for said motor velocity compensation at least sufficient to stabilize said electric power steering system, while said torque compensator and high pass low pass structure are disabled;

evaluating on-center feel characteristics of said performance and reducing said schedulable gain when said commands are low to achieve acceptable on-center feel characteristics;

increasing a high pass gain for said high pass low pass structure including an appropriate cut-off frequency for a high pass filter and a low pass filter if said reducing causes instability to once again achieve stability of said torque control of said electric power steering system;

reincorporating said torque compensator at a depth sufficient to achieve stability if said increasing results in excessive high pass gain.

54. The method of claim 48 wherein said command includes a voltage command responsive to a combined command and said motor velocity signal.

55. The method of claim 54 wherein said combined command is a result of a summation of a torque command and a compensated motor velocity, said compensated motor velocity the resultant of said motor velocity compensation comprising a frequency based filter acting on said motor velocity signal.

56. The method of claim 55 wherein said motor velocity compensation is configured to maintain stability of said torque control of said electric power steering system.

57. The method of claim 56 wherein said motor velocity compensation is configured to enhance performance of said torque control of said electric power steering system.

58. The method of claim 57 wherein said enhance performance of said torque control of said electric power steering system comprises at least one of:

an increase of velocity disturbance rejection;

an increase of torque disturbance rejection;

maintenance of steering wheel input impedance as substantially flat for low frequencies and increasing for higher frequencies thereafter.

59. The method of claim 57 wherein said motor velocity compensation is configured to characterize on-center feel of said torque control of said electric power steering system.

60. The method of claim 48 wherein said motor velocity compensation is configured to enhance performance of said torque control of said electric power steering system.

61. The method of claim 60 wherein said enhance performance of said torque control of said electric power steering system comprises at least one of:

an increase of velocity disturbance rejection;

an increase of torque disturbance rejection;

maintenance of steering wheel input impedance as substantially flat for low frequencies and increasing for higher frequencies thereafter.

62. The method of claim 61 wherein said motor velocity compensation is configured to characterize on-center feel of said torque control of said electric power steering system.

63. The method of claim 48 wherein said motor velocity compensation is configured to ensure adequate on-center feel of said torque control of said electric power steering system.

64. The method of claim 57 wherein said frequency based filter comprises at least one pole.

65. The method of claim 57 wherein said frequency based filter comprises at least one zero.

66. The method of claim 57 wherein said frequency based filter comprises at least one pole and at least one zero.

67. The method of claim 57 wherein said frequency based filter comprises a pole placed at 12 Hertz and a zero placed at zero Hertz.

68. The method of claim 57 wherein said frequency based filter further includes a schedulable gain.

69. The method of claim 57 wherein said torque command is a resultant of a high pass low pass structure, said high pass low pass structure responsive to a compensated torque signal, said compensated torque signal the resultant of a torque compensator.

70. The method of claim 69 wherein said torque compensator comprises a frequency based notch filter configured to maintain stability of said torque control of said electric power steering system.

71. The method of claim 69 wherein said high pass low pass structure comprises a high frequency path including a high pass gain and a low frequency path including a low pass gain.

72. The method of claim 71 wherein said high frequency path is configured to control torque disturbance rejection of said electric power steering system.

73. The method of claim 71 wherein said low frequency path is configured to control steady state torque response of said electric power steering system.

74. A storage medium comprising:

said storage medium encoded with a machine readable computer program code;

said code including instructions for causing a computer to implement a method for controlling an electric power steering system, the method comprising;

receiving a torque signal responsive to a torque applied to a steering wheel;

obtaining a motor velocity signal, said motor velocity signal indicative of a speed of an electric motor; and

generating a command for said electric motor, said command including torque control and motor velocity compensation, responsive to at least one of said torque signal and a motor velocity signal.

75. A computer data signal comprising:

said computer data signal comprising code configured to cause a processor to implement a method for controlling an electric power steering system, the method comprising;

receiving a torque signal responsive to a torque applied to a steering wheel;

obtaining a motor velocity signal, said motor velocity signal indicative of a speed of an electric motor; and

generating a command for said electric motor, said command including torque control and motor velocity compensation, responsive to at least one of said torque signal and a motor velocity signal.

76. A electric power steering control system incorporating motor velocity compensation comprising:

an electric motor disposed in a vehicle to apply torque to a steerable wheel;

a torque sensor disposed in said vehicle for detecting a steering wheel torque and generating a torque signal indicative thereof;

a controller coupled to said torque sensor, and said electric motor; and

said controller including;

means for receiving a torque signal responsive to a torque applied to a steering wheel;

means for obtaining a motor velocity signal, said motor velocity signal indicative of a speed of an electric motor; and

means for generating a command for said electric motor, said command including torque control and motor velocity compensation, responsive to at least one of said torque signal, and a motor velocity signal.

77. A controller for controlling an electric power steering system, the controller comprising:

means for receiving a torque signal responsive to a torque applied to a steering wheel;

means for obtaining a motor velocity signal, said motor velocity signal indicative of a speed of an electric motor; and

means for generating a command for said electric motor, said command including torque control and motor velocity compensation, responsive to at least one of said torque signal and a motor velocity signal.