Steer-by-wire system

• US 6,370,460 B1
• Filed: 12/28/2000
• Issued: 04/09/2002
• Est. Priority Date: 09/17/1999
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Byers, Michael D., Kaufmann, Timothy Wesley
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): MANCHO, RONNIE M
• Application Number:
  US09/751,021
• Publication Number:
  US 20020035424A1
• Time in Patent Office: 467 Days
• Field of Search: 701/41, 701/42, 701/43, 701/44, 701/33, 340/466, 340/465, 340/576, 332/03, 332/031.8, 180/402, 180/403, 180/444, 180/445, 180/446-449
• US Class Current: 701/41
• CPC Class Codes: B62D 5/001 Mechanical components or aspects of steer-by-wire systems, not otherwise provided for in this maingroup
• 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 having a steering wheel unit responsive to a steering wheel torque command and a road wheel unit responsive to a road wheel unit command is disclosed. A master control unit may be employed to perform processing as necessary. A method for steering a vehicle including receiving a tie-rod force signal, a road wheel position signal, a vehicle speed signal, a steering wheel position signal, and a feedback torque signal. Combining these signals to generate the steering wheel torque command signal and road wheel command signal to provide the operator with tactile feedback, while road wheel command signals are sent to road wheel units to provide steering direction. An Ackerman correction unit may also used to correct the left and right road wheel positions to track about a common center.

Claims

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

a road wheel unit responsive to a road wheel command signal for steering a vehicle;

a steering wheel unit responsive to a steering wheel torque command signal;

a vehicle speed sensor for producing a vehicle speed signal;

a master control unit electrically configured and connected to said vehicle speed sensor, said steering wheel unit, and said road wheel unit;

wherein said road wheel unit includes a road wheel position sensor and a tie-rod sensor to produce and transmit a tie-rod force signal;

wherein said steering wheel unit includes a steering wheel position sensor to produce and transmit a steering wheel position signal and a torque sensor to produce and transmit a feedback torque sensor signal;

said master control unit includes a position control unit that calculates said road wheel command signal in response to said vehicle speed signal, said feedback torque sensor signal and said steering wheel position signal;

said master control unit generates a composite tie-rod force signal; and

said master control unit includes a torque control unit that calculates and produces said steering wheel torque command signal in response to said composite tie-rod force signal, said feedback torque sensor signal, said steering wheel position signal and said vehicle speed signal.

2. The steer-by-wire control system of claim 1 wherein said torque control unit includes an active damping process wherein a desired damping command is generated responsive to said feedback torque sensor signal, said steering wheel position signal, and said vehicle speed signal, which is compared with said composite tie-rod force signal to generate a damping torque command signal.

3. The steer-by-wire control system of claim 2 wherein said desired damping command is responsive to a time rate of change of said steering wheel position signal and modified by the feedback torque sensor signal and vehicle speed signal.

4. The steer-by-wire control system of claim 2 wherein said torque control unit implements a compensation process employing frequency based filters to configure spectral content of said damping torque command signal thereby generating a compensated torque command signal.

5. The steer-by-wire control system of claim 4 wherein said compensation process includes frequency based filters configured to modify the spectral content of sensed road feedback to an operator.

6. The steer-by-wire control system of claim 4 wherein said compensation process includes frequency based filters configured to maintain stability of said steer-by-wire control system.

7. The steer-by-wire control system of claim 6 wherein said compensation process includes frequency based filters configured to modify the spectral content of sensed road feedback to an operator.

8. The steer-by-wire control system of claim 4 wherein said torque control unit further implements a feel process which generates said steering wheel torque command signal in response to combining an assist torque command and a return torque command.

9. The steer-by-wire control system of claim 8 wherein said combining is a summation.

10. The steer-by-wire control system of claim 8 wherein said torque control unit further implements a feel process comprising an assist sub-process responsive to said compensated torque command signal and said vehicle speed signal, which generates said assist torque command and a return sub-process responsive to said steering wheel position signal and said vehicle speed signal, which generates said return torque command.

11. The steer-by-wire control system of claim 10 wherein said assist sub-process indexes said compensated torque command signal to at least one assist look-up table and blends an output thereof to generate a blended value of said assist torque command.

12. The steer-by-wire control system of claim 11 wherein said outputs of said at least one assist look-up table are blended in a ratio dependent upon said vehicle speed signal.

13. The steer-by-wire control system of claim 10 wherein said return sub-process indexes said steering wheel position signal to at least one return look-up table and blends an output thereof to generate said return torque command.

14. The steer-by-wire control system of claim 13 wherein said outputs of said at least one return look-up table are blended in a ratio dependent upon said vehicle speed signal.

15. The steer-by-wire control system of claim 1 wherein said position control unit calculates and produces a variable steering ratio signal in response to said steering wheel position signal, said feedback torque sensor signal, and said vehicle speed signal.

16. The steer-by-wire control system of claim 15 wherein said variable steering ratio signal is calculated using said steering wheel position signal and said vehicle speed signal as inputs to a steering ratio look-up table.

17. The steer-by-wire control system of claim 16 wherein said position control unit further comprises a road wheel command unit that calculates a theta correction and generates a theta corrected road wheel command signal from said variable steering ratio signal, said feedback torque sensor signal, and said steering wheel position signal.

18. The steer-by-wire control system of claim 15 wherein said position control unit calculates and produces a road wheel command signal in response to said steering wheel position signal, said feedback torque sensor signal, and said variable steering ratio signal.

19. The steer-by-wire control system of claim 15 wherein said position control unit further includes an Ackerman correction unit for producing a left road wheel signal and a right road wheel signal in response to said road wheel command signal.

20. The steer-by-wire control system of claim 19 wherein said road wheel unit includes a linear correction unit for calculating and producing a position command signal in response to a road wheel command signal.

41. The steer-by-wire control system of claim 1 wherein said steering wheel unit comprises a closed loop control system responsive to said steering wheel torque command signal and said feedback torque sensor signal.

42. The steer-by-wire control system of claim 1 wherein said steering wheel unit exhibits a bandwidth sufficient to facilitate said torque control unit maintaining stability of said steer-by-wire system.

43. The steer-by-wire control system of claim 1 wherein said steering wheel unit comprises a steering wheel control unit and a steering wheel plant dynamics unit.

44. The steer-by-wire control system of claim 43 wherein:

said steering wheel control unit is respnsive to said steeringsaid steering wheel torque command signal and said feedback torque sensor signal and generates a torque command signal;

said steering wheel plant dynamics unit is responsive to said torque command signal and provides a reaction torque in response thereto to an operator.

wherein said steering wheel plant dynamics unit comprises a motor configured to position a steering wheel thereby generating said reaction torque.

45. The steer-by-wire control system of claim 44 wherein said steering wheel control unit includes a frequency based compensator configured to characterize spectral content of said torque command signal to maintain stability of said steering wheel unit.

46. The steer-by-wire control system of claim 45 wherein said steering wheel control unit includes a frequency based compensator configured to characterize spectral content of said torque command signal to increase bandwidth of said steering wheel unit.

47. The steer-by-wire control system of claim 44 wherein said steering wheel control unit includes a frequency based compensator configured to characterize spectral content of said torque command signal to increase the bandwidth of said steering wheel unit.

48. The steer-by-wire control system of claim 47 wherein said steering wheel unit exhibits a bandwidth of at least one Hertz.

49. The steer-by-wire control system of claim 48 wherein said steering wheel unit exhibits a bandwidth of about ten Hertz.

50. The steer-by-wire control system of claim 44 wherein said steering wheel control unit includes a frequency based compensator configured to characterize spectral content of said torque command signal such that is said steering wheel unit exhibits a bandwidth sufficient to facilitate generation of a steering wheel torque command signal by said torque control unit to maintain stability of said steer-by-wire system.

51. The steer-by-wire control system of claim 1 wherein said road wheel unit comprises a road wheel control unit and a road wheel plant dynamics unit.

52. The steer-by-wire control system of claim 1 wherein said road wheel unit exhibits a bandwidth sufficient to facilitate said position control unit maintaining stability of said steer-by-wire system.

53. The steer-by-wire control system of claim 1 wherein said road wheel unit comprises a closed loop control system responsive to said road wheel command signal and a road wheel position signal from said road wheel position sensor.

54. The steer-by-wire control system of claim 53 wherein said road wheel unit comprises a road wheel control unit and a road wheel plant dynamics unit.

55. The steer-by-wire control system of claim 54 wherein:

said road wheel control unit is responsive to said road wheel command signal and a road wheel position signal and generates a position command signal;

said road wheel plant dynamics unit is responsive to said position command signal and provides a road wheel position in response thereto

wherein said road wheel plant dynamics unit comprises a motor configured to position a road wheel.

56. The steer-by-wire control system of claim 55 wherein said road wheel control unit includes a frequency based compensator configured to characterize spectral content of said position command signal to maintain stability of said road wheel unit.

57. The steer-by-wire control system of claim 56 wherein said road wheel control unit includes a frequency based compensator configured to characterize spectral content of said position command signal to increase bandwidth of said road wheel unit.

58. The steer-by-wire control system of claim 55 wherein said road wheel control unit includes a frequency based compensator configured to characterize spectral content of said position command signal to increase the bandwidth of said road wheel unit.

59. The steer-by-wire control system of claim 58 wherein said road wheel unit exhibits a bandwidth of at least one Hertz.

60. The steer-by-wire control system of claim 59 wherein said road wheel unit exhibits a bandwidth of about ten Hertz.

61. The steer-by-wire control system of claim 55 wherein said road wheel control unit includes a frequency based compensator configured to characterize spectral content of said position command signal such that said road wheel unit exhibits a bandwidth sufficient to facilitate generation of a road wheel command signal by said position control unit to maintain stability of said steer-by-wire system.

21. A method for steering a vehicle comprising:

receiving a tie-rod force signal and a road wheel position signal;

receiving a vehicle speed signal;

receiving a steering wheel position signal and a feedback torque sensor signal;

combining at least two of;

said tie-rod force signal, said road wheel position signal, said vehicle speed signal, said steering wheel position signal and said feedback torque sensor signal;

generating a steering wheel torque command signal based on said combining;

generating a road wheel command signal based on said combining;

generating a composite tie-rod force signal from said tie-rod force signal;

wherein said steering wheel torque command signal is responsive to said composite tie-rod force signal, said feedback torque sensor signal, said steering wheel position signal and said vehicle speed signal; and

wherein said road wheel command signal is responsive to said vehicle speed signal, said feedback torque sensor signal and said steering wheel position signal.

22. The method for steering a vehicle of claim 21 further comprising:

generating a desired damping command responsive to said feedback torque sensor signal, said steering wheel position signal and said vehicle speed signal;

combining said desired damping command and said composite tie-rod force signal producing a damping torque command signal.

23. The method for steering a vehicle of claim 22 wherein said desired damping command is responsive to a time rate of change of said steering wheel position signal.

24. The method for steering a vehicle of claim 22 further comprising:

compensating said damping torque command signal to configure spectral content of said damping torque command signal thereby generating a compensated torque command signal.

25. The method for steering a vehicle of claim 24 wherein said compensating includes frequency based filters configured to tailor sensed road feedback to an operator.

26. The method for steering a vehicle of claim 24 wherein said compensating includes frequency based filtering configured to maintain stability.

27. The method for steering a vehicle of claim 26 wherein said compensating includes frequency based filters configured to modify the spectral content of sensed road feedback to an operator.

28. The method for steering a vehicle of claim 21 further comprising:

generating said steering wheel torque command signal responsive to a combination of an assist torque command and a return torque command.

29. The method for steering a vehicle of claim 28 wherein

said assist torque command is responsive to said compensated torque command signal and said vehicle speed signal;

and

said return torque command is responsive to said steering wheel position signal and said vehicle speed signal.

30. The method for steering a vehicle of claim 29 wherein said compensated torque command signal is an index to at least one assist look-up table and blends an output thereof to generate a blended value of an assist torque command.

31. The method for steering a vehicle of claim 30 wherein said output of said at least one assist look-up table is blended in a ratio dependent upon said vehicle speed signal.

32. The method for steering a vehicle of claim 29 wherein said steering wheel position signal is an index of at least one return look-up table and blends an output thereof to generate a return torque command signal.

33. The method for steering a vehicle of claim 32 wherein said output of said at least one return look-up table is blended in a ratio dependent upon said vehicle speed signal.

34. The method for steering a vehicle of claim 21 further comprising calculating and producing a variable steering ratio signal in response to said steering wheel position signal and said vehicle speed signal.

35. The method for steering a vehicle of claim 34 wherein said generating said road wheel command signal is in response to said steering wheel position signal, said feedback torque sensor signal, and said variable steering ratio signal.

36. The method for steering a vehicle of claim 35 further comprising:

calculating an Ackerman correction factor; and

modifying said road wheel command signal with said Ackerman correction factor to cause each wheel of said vehicle to track about a common center.

37. The method of steering a vehicle of claim 36 further comprising calculating and producing a position command signal.

38. The method of steering a vehicle of claim 37 further comprising calculating and producing a left and right road wheel command signal associated with said vehicle'"'"'s left and right road wheel respectively.

62. The method for steering a vehicle of claim 21 further including generating a torque command signal in a steering wheel unit such that said steering wheel unit exhibits a bandwidth sufficient to facilitate a torque control unit generating said steering wheel torque command signal to facilitate maintaining stability of said steering.

63. The method for steering a vehicle of claim 21 wherein said steering wheel torque command signal and said feedback torque sensor signal are applied to steering wheel unit comprising a closed loop control system responsive thereto.

64. The method for steering a vehicle of claim 63 wherein said steering wheel unit comprises a steering wheel control unit and a steering wheel plant dynamics unit.

65. The method for steering a vehicle of claim 64 wherein:

said torque command signal is generated in a steering wheel control unit responsive to said steering wheel torque command signal and said feedback torque sensor signal and

said steering wheel plant dynamics unit is responsive to said torque command signal and provides a reaction torque in response thereto to an operator.

wherein said steering wheel plant dynamics unit comprises a motor configured to position a steering wheel thereby generating said reaction torque.

66. The method for steering a vehicle of claim 64 wherein said torque command signal is applied to frequency-based compensation to characterize spectral content of said torque command signal to maintain stability of said steering wheel unit.

67. The method for steering a vehicle of claim 66 wherein said torque command signal is applied to frequency-based compensation to characterize spectral content of said torque command signal to increase bandwidth of said steering wheel unit.

68. The method for steering a vehicle of claim 64 wherein said torque command signal is applied to frequency based compensation to characterize spectral content of said torque command signal to increase the bandwidth of said steering wheel unit.

69. The method for steering a vehicle of claim 68 wherein said steering wheel unit exhibits a bandwidth of at least one Hertz.

70. The method for steering a vehicle of claim 69 wherein said steering wheel unit exhibits a bandwidth of about ten Hertz.

71. The method for steering a vehicle of claim 65 further including generating a torque command signal in a steering wheel unit such that said steering wheel unit exhibits a bandwidth sufficient to facilitate a torque control unit generating said steering wheel torque command signal to facilitate maintaining stability said steering.

72. The method for steering a vehicle of claim 21 further including generating a position command signal in a road wheel unit such that said road wheel exhibits a bandwidth sufficient to facilitate a torque control unit generating said road wheel command signal to facilitate maintaining stability of said steering.

73. The method for steering a vehicle of claim 21 wherein said road wheel command signal and a road wheel position signal from a road wheel position sensor are applied to a road wheel unit comprising a closed loop control system responsive thereto.

74. The method for steering a vehicle of claim 73 wherein said road wheel unit comprises a road wheel control unit and a road wheel plant dynamics unit.

75. The method for steering a vehicle of claim 74 wherein:

said position command signal is generated in a road wheel control unit responsive to said road wheel command signal and a road wheel position signal;

said road wheel plant dynamics unit is responsive to said position command signal and provides a road wheel position in response thereto.

wherein said road wheel plant dynamics unit comprises a motor configured to position a road wheel.

76. The method for steering a vehicle of claim 74 wherein said position command signal is applied to a frequency-based compensation to characterize spectral content of said position command signal to maintain stability of said road wheel unit.

77. The method for steering a vehicle of claim 76 wherein said position command signal is applied to frequency-based compensation to characterize spectral content of said position command signal to increase bandwidth of said road wheel unit.

78. The method for steering a vehicle of claim 75 wherein said position command signal is applied to frequency-based compensation to characterize spectral content of said position command signal to increase bandwidth of said road wheel unit.

79. The method for steering a vehicle of claim 78 wherein said road wheel unit exhibits a bandwidth of at least one Hertz.

80. The method for steering a vehicle of claim 79 wherein said road wheel unit exhibits a bandwidth of about ten Hertz.

81. The method for steering a vehicle of claim 75 further including generating a position command signal in a road wheel control unit such that said road wheel unit exhibits a bandwidth sufficient to facilitate a position control unit generating said road wheel command signal to facilitate maintaining stability of said steering.

39. The storage medium encoded with a machine-readable computer program code for steering a vehicle, said storage medium including instructions for causing a computer to implement a method comprising:

receiving a tie-rod force signal and a road wheel position signal;

receiving a vehicle speed signal;

receiving a steering wheel position signal and a feedback torque sensor signal;

combining at least two of;

said tie-rod force signal, said road wheel position signal, said vehicle speed signal, said steering wheel position signal and said feedback torque sensor signal;

generating a steering wheel torque command signal based on said combining;

generating a road wheel command signal based on said combining;

generating a composite tie-rod force signal from said tie-rod force signal;

wherein said steering wheel torque command signal is responsive to said composite tie-rod force signal, said feedback torque sensor signal, said steering wheel position signal and said vehicle speed signal; and

wherein said road wheel command signal is responsive to said vehicle speed signal, said feedback torque sensor signal and said steering wheel position signal.

40. The computer data signal for steering a vehicle, said computer data signal including instructions for causing a computer to implement a method comprising:

receiving a tie-rod force signal and a road wheel position signal;

receiving a vehicle speed signal;

receiving a steering wheel position signal and a feedback torque sensor signal;

combining at least two of;

said tie-rod force signal, said road wheel position signal, said vehicle speed signal, said steering wheel position signal and said feedback torque sensor signal;

generating a steering wheel torque command signal based on said combining;

generating a road wheel command signal based on said combining;

generating a composite tie-rod force signal from said tie-rod force signal;

wherein said steering wheel torque command signal is responsive to said composite tie-rod force signal, said feedback torque sensor signal, said steering wheel position signal and said vehicle speed signal; and

wherein said road wheel command signal is responsive to said vehicle speed signal, said feedback torque sensor signal and said steering wheel position signal.