Vehicle compass compensation

• US 6,922,902 B2
• Filed: 01/28/2003
• Issued: 08/02/2005
• Est. Priority Date: 04/08/1999
• Status: Expired due to Fees

• Current Assignee: Donnelly Corporation (Magna International Incorporated)
• Original Assignee: Donnelly Corporation (Magna International Incorporated)
• Inventors: Schofield, Kenneth, Blank, Rodney K., Schierbeek, Kenneth L., DeVette, Gregory H., Hoekstra, Eric J., Veiseh, Merdad
• Primary Examiner(s): Gutierrez, Diego
• Assistant Examiner(s): REIS, TRAVIS M
• Application Number:
  US10/352,691
• Publication Number:
  US 20030115764A1
• Time in Patent Office: 917 Days
• Field of Search: 333/55.R, 333/57, 333/33, 333/56, 702/92, 702/295, 702/115, 329/202, 329/225, 329/244, 329/260, 324/202, 324/225, 324/244, 324/260
• US Class Current: 33/356
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A compass compensation system is provided for automatically and continuously calibrating an electronic compass for a vehicle, without requiring an initial manual calibration or preset of the vehicle magnetic signature. The system initially adjusts a two axis sensor of the compass in response to a sampling of at least one initial data point. The system further calibrates the compass by sampling data points that are substantially opposite to one another on a plot of a magnetic field and averaging an ordinate of the data points to determine a respective zero value for the Earth magnetic field. The system also identifies a change in magnetic signature and adjusts the sensor assembly.

Claims

1. A vehicular electronic compass system comprising:

a magneto-responsive sensor assembly for sensing a magnetic field, said magneto-responsive sensor comprising at least a two-axis sensor for sensing two components of a magnetic field, said two-axis sensor comprising a first axis sensing element and a second axis sensing element, one of said first axis sensing element and said second axis sensing element being generally aligned with a direction of travel of a vehicle when the vehicular electronic compass system is operated in the vehicle;

an electronic circuit responsive to said two-axis sensor for distinguishing the Earth magnetic field from a deviating field of the vehicle in order to determine a directional heading of the vehicle;

said electronic circuit including a microprocessor and an analog-to-digital converter;

said distinguishing the Earth magnetic field from a deviating field of the vehicle incluiding an initial calibration mode that brings the output signal of at least one of said first axis and second axis sensing elements to be within the operable range of said analog-to-digital converter and wherein said electronic circuit detects a first peak value of the Earth magnetic field by said microprocessor of data sensed by one of said first axis and second axis sensing elements, wherein said electronic circuit detects a second peak value of the Earth magnetic field by processing by said microprocessor of data sensed by said one of said first axis and second axis sensing elements, wherein said electronic circuit calculates a zero reference value using said detected first and second peak values, wherein said electronic circuit detects a third peak value of the Earth magnetic field by processing by said microprocessor of data sensed by the other one of said first axis and second axis sensing elements, and wherein said electronic circuit algorithmically calculates a fourth peak value of the Earth magnetic field using said detected first, second and third peak values without a need for the vehicle to turn through a 360 degree circle; and

an electronic display coupled with said electronic circuit, said electronic display displaying the directional heading of the vehicle at least during said initial calibration mode.

2. The vehicular electronic compass system in claim 1, wherein said magneto-responsive sensor comprises one of a magneto-inductive sensor, a magneto-resistive sensor, a magneto-capacitive sensor and a flux gate sensor.

3. The vehicular electronic compass system in claim 1, wherein said magneto-responsive sensor comprises a magneto-resistive sensor.

4. The vehicular electronic compass system of claim 1, wherein said first axis and second axis sensing elements are oriented in a predetermined angular relationship with each other and in a predetermined orientation with respect to the vehicle.

5. The vehicular electronic compass system of claim 1, wherein said magneto-responsive sensor senses Earth magnetic field and a deviating magnetic field and said electronic circuit adjusts said sensor to substantially nullify the deviating magnetic field.

6. The vehicular electronic compass system in claim 1, wherein said bringing of the output signals of at least one of said first axis and second axis sensing elements to be within the operable range of said analog-to-digital convertor utilizes an assumed value of the Earth magnetic field.

7. The vehicular electronic compass system in claim 6, wherein assumed value of the Earth magnetic field is about 200 mg.

8. The vehicular electronic compass system in claim 1, wherein said directional heading of the vehicle displayed by said electronic display is within a range of accuracy relative to the true Earth magnetic field acceptable to an operator of the vehicle.

9. The vehicular electronic compass system in claim 1, wherein said system switches to another calibration mode after said initial calibration mode is completed.

10. The vehicular electronic compass system in claim 9, wherein said another calibration mode accounts for relatively minor changes of the vehicle magnetic signature.

11. The vehicular electronic compass system in claim 10, wherein said another calibration mode encompasses at least two stages.

12. The vehicular electronic compass system in claim 11, wherein at least one of said at least two stages comprises data gathering over multiple ignition cycles of the vehicle.

13. The vehicular electronic compass system in claim 9, wherein said another calibration mode brings the directional heading of the vehicle displayed by said electronic display within a tighter range of accuracy relative to the true Earth magnetic field than what is achieved during said initial calibration mode.

14. The vehicular electronic compass system in claim 1, wherein said electronic display comprises part of a vehicular mirror assembly.

15. The vehicular electronic compass system of claim 1, wherein said electronic circuit includes an extended range calibration function, said extended range calibration function identifying a change in magnetic signature sensed by said magneto-responsive sensor and adjusting said magneto-responsive sensor in response to a change in magnetic signature.

16. The vehicular electronic compass system in claim 15, wherein said calibration function identifies a change in magnetic signature from said magneto-responsive sensor reaching a limit of operation of said electronic circuit.

17. The vehicular electronic compass system in claim 16, wherein said electronic circuit calculates a zero reference value or the Earth magnetic field after adjusting said sensor.

18. The vehicular electronic compass system in claim 15, wherein said calibration function identifies a change in magnetic signature from an abnormal relation between collected data points and said zero reference value of the Earth magnetic field.

19. The vehicular electronic compass system in claim 18, wherein said abnormal relation comprises said zero reference value of the Earth magnetic field fulling outside of opposite peak values of the Earth magnetic field.

20. The vehicular electronic compass system in claim 19, wherein said electronic circuit calculates a zero reference value of the Earth magnetic field after adjusting said sensor.

21. The vehicular electronic compass system in claim 15, wherein said electronic circuit occasionally calculates a zero reference value of the Earth magnetic field and wherein said calibration function identifies a change in magnetic signature from a change in said zero reference value of the Earth magnetic field which exceeds a predetermined amount.

22. The vehicular electronic compass system in claim 21, wherein said predetermined amount comprises a predetermined portion of an operating range of said electronic circuit.

23. The vehicular electronic compass system in claim 21, wherein said electronic circuit calculates a new zero reference value of the Earth magnetic field after adjusting said sensor.

24. The vehicular electronic compass system in claim 15, wherein said electronic circuit includes a digital-to-analog converter converting digital values to analog signals supplied to said magneto-responsive sensor for adjusting said magneto-responsive sensor.

25. The vehicular electronic compass system in claim 24, wherein said analog-to-digital converter converts outputs of said magneto-responsive sensor to digital signals, said analog-to-digital converter having a range of operation defining a limit of operation of said electronic circuit.

26. The vehicular electronic compass system in claim 15, wherein magneto-responsive sensor comprises one of a magneto-inductive sensor, a magneto-resistive sensor, a magneto-capacitive sensor, and a flux gaze sensor.

27. The vehicular electronic compass system in claim 15, wherein said magneto-responsive sensor comprises a magneto-resistive sensor.

28. The vehicular electronic compass system of claim 15, wherein said first axis and second axis sensing elements are oriented in a predetermined angular relationship with each other and in a predetermined orientation with respect to the vehicle.

29. A vehicular electronic compass system comprising:

a magneto-responsive sensor for sensing a magnetic field, said magneto-responsive sensor comprising at least a two-axis sensor for sensing two components of a magnetic field, said two-axis sensor comprising a first axis sensing element and a second axis sensing element, one of said first axis sensing element and said second axis sensing element being generally aligned with a direction of travel of a vehicle when the vehicular electronic compass system is operated in the vehicle;

an electronic circuit responsive to said two-axis sensor for distinguishing the Earth magnetic field from a deviating field of the vehicle in order to determine a directional heading of the vehicle;

said electronic circuit including a microprocessor;

said distinguishing the Earth magnetic field from a deviating field of the vehicle including an initial calibration mode that comprises said electronic circuit detecting a first peak value of the Earth magnetic field by processing by said microprocessor of data sensed by one of said first axis and second axis sensing elements, said electronic circuit detecting a second peak value of the Earth magnetic field by processing by said microprocessor of data sensed by said one of said first axis and second axis sensing elements, said electronic circuit calculating a zero reference value using said detected first and second peak values, said electronic circuit detecting a third peak value of the Earth magnetic field by processing by said microprocessor of data sensed by the other one of said first axis and second axis sensing elements, and said electronic circuit algorithmically calculating a fourth peak value of the Earth magnetic field using said detected first, second and third peak values without a need for the vehicle to turn through a 360 degree circle;

an electronic display coupled with said electronic circuit for displaying the directional heading of the vehicle; and

wherein said directional heading of the vehicle displayed by said electronic display is within a range of accuracy relative to the true Earth magnetic field acceptable to an operator of the vehicle.

30. The vehicular electronic compass system in claim 29, wherein said electronic circuit includes an analog-to-digital converter and wherein said electronic circuit brings the output signals of at least one of said first axis and second axis sensing elements to be within the operable range of said analog-to-digital converter.

31. The vehicular electronic compass system in claim 30, wherein said bringing of the output signals of at least one of said first axis and second axis sensing elements to be within the operable range of said analog-to-digital converter utilizes an assumed value of the Earth magnetic field.

32. The vehicular electronic compass system in claim 31, wherein said assumed value of the Earth magnetic field is about 200 mg.

33. The vehicular electronic compass system of claim 30, wherein said electronic circuit includes an extended range calibration function, said extended range calibration function identifying a change in magnetic signature sensed by said magneto-responsive sensor and adjusting said magneto-responsive sensor in response to a change in magnetic signature.

34. The vehicular electronic compass system in claim 33, wherein said calibration function identifies a change in magnetic signature from said magneto-responsive sensor reaching a limit of operation of said electronic circuit.

35. The vehicular electronic compass system in claim 34, wherein said electronic circuit calculates a zero reference value of the Earth magnetic field after adjusting said sensor.

36. The vehicular electronic compass system in claim 33, wherein said calibration function identifies a change in magnetic signature from an abnormal relation between collected data points and said zero reference value of the Earth magnetic field.

37. The vehicular electronic compass system in claim 36, wherein said abnormal relation comprises said zero reference value of the Earth magnetic field falling outside of opposite peak values of the Earth magnetic field.

38. The vehicular electronic compass system in claim 37, wherein said electronic circuit calculates a zero reference value of the Earth magnetic field after adjusting and sensor.

39. The vehicular electronic compass system in claim 33, wherein said electronic circuit occasionally calculates a zero reference value of the Earth magnetic field and wherein said calibration function identifies a change in magnetic signature from a change in said zero reference value of the Earth magnetic field which exceeds a predetermined amount.

40. The vehicular electronic compass system in claim 39, wherein said predetermined amount comprises a predetermined portion of an operating range of said electronic circuit.

41. The vehicular electronic compass system in claim 40, wherein said electronic circuit calculates a new zero reference value of the Earth magnetic field after adjusting said sensor.

42. The vehicular electronic compass system in claim 33 wherein said electronic circuit includes a digital-to-analog converter converting digital values to analog signals supplied to said magneto-responsive sensor for adjusting said magneto-responsive sensor.

43. The vehicular electronic compass system in claim 42, wherein said analog-to-digital converter converts outputs of said magneto-responsive sensor to digital signals, said analog-to-digital converter having a range of operation defining a limit of operation of said electronic circuit.

44. The vehicular electronic compass system in claim 33, wherein said magneto-responsive sensor comprises one of a magneto-inductive sensor, a magneto-resistive sensor, a magneto-capacitive sensor, and a flux gate sensor.

45. The vehicular electronic compass system in claim 33, wherein said magneto-responsive sensor comprises a magneto-resistive sensor.

46. The vehicular electronic compass system of claim 33, wherein said first axis and second axis sensing elements are oriented in a predetermined angular relationship with each other and in a predetermined orientation with respect to the vehicle.

47. The vehicle electronic compass system in claim 29, wherein said system switches to another calibration mode after said initial calibration mode is completed.

48. The vehicular electronic compass system in claim 47, wherein said another calibration mode accounts for relatively minor changes of the vehicle magnetic signature.

49. The vehicular electronic compass system in claim 48, wherein said another calibration mode encompasses at least two stages.

50. The vehicular electronic compass system in claim 49, wherein at least one of said at least two stages comprises data gathering over multiple ignition cycles of the vehicle.

51. The vehicular electronic compass system in claim 47, wherein said another calibration mode brings the directional heading of the vehicle displayed by said electronic display within a tighter range of accuracy relative to the true Earth magnetic field than what is achieved during said initial calibration mode.

52. The vehicular electronic compass system in claim 29, wherein said magneto-responsive sensor comprises one of a magneto-inductive sensor, a magneto-resistive sensor, a magneto-capacitive sensor and a flux gate sensor.

53. The vehicular electronic compass system in claim 29, wherein said magneto-responsive sensor comprises a magneto-resistive sensor.

54. The vehicular electronic compass system of claim 29, wherein said first axis and second axis sensing elements are oriented in a predetermined angular relationship with each other and in a predetermined orientation with respect to the vehicle.

55. The vehicular electronic compass system of claim 29, wherein said magneto-responsive sensor senses the Earth magnetic field and a deviating magnetic field and said electronic circuit adjusts said magneto-responsive sensor to substantially nullify the deviating magnetic field.

56. The vehicular electronic compass system in claim 29, wherein said electronic display comprises part of a vehicular mirror assembly.

57. The vehicular electronic compass system of claim 29, wherein said electronic display displays said directional heading of the vehicle at least during said initial calibration mode.

58. A vehicular electronic compass system comprising:

a magneto-responsive sensor for sensing a magnetic field, said magneto-responsive sensor comprising at least a two-axis sensor for sensing two components at a magnetic field, said two-axis sensor comprising a first axis sensing element and a second axis sensing element, one of said first axis sensing element and said second axis sensing element being generally aligned with a direction of travel of a vehicle when the vehicular electronic compass system is operated in the vehicle;

an electronic circuit responsive to said two-axis sensor for distinguishing the Earth magnetic field from a deviating field of the vehicle in order to determine a directional heading of the vehicle;

said electronic circuit including a microprocessor;

said distinguishing the Earth magnetic field from a deviating field of the vehicle including an initial calibration mode that comprises said electronic circuit detecting a first peak value of the Earth magnetic field by processing by said microprocessor of data sensed by one of said first axis and second axis sensing elements, said electronic circuit detecting a second peak value of the Earth magnetic field by processing by said microprocessor of data sensed by said one of said first axis and second axis sensing elements, said electronic circuit calculating a zero reference value using said detected first and second peak values;

said system switching to another calibration mode after said initial calibration mode is completed;

an electronic display coupled with said electronic circuit for displaying the directional heading of the vehicle;

said directional heading of the vehicle displayed by said electronic display being within a range of accuracy relative to the true Earth magnetic field acceptable to an operator of the vehicle; and

wherein said electronic display displays said directional heading of the vehicle at least during said initial calibration mode.

59. The vehicular electronic compass system in claim 58, wherein said electronic circuit includes an analog-to-digital converter and wherein said electronic circuit brings the output signals of at least one of said first axis and second axis sensing elements to be within the operable range of said analog-to-digital converter.

60. The vehicular electronic compass system in claim 59, wherein said bringing of the output signals of at least one of said first axis and second axis sensing elements to be within the operable range of said analog-to-digital converter utilizes an assumed value of the Earth magnetic field.

61. The vehicular electronic compass system in claim 60, wherein said assumed value of the Earth magnetic field is about 200 mg.

62. The vehicular electronic compass system of claim 59, wherein said electronic circuit includes an extended range calibration function, said extended range calibration function identifying a change in magnetic signature sensed by said magneto-responsive sensor and adjusting said magneto-responsive sensor in response in a change in magnetic signature.

63. The vehicular electronic compass system in claim 62, wherein said calibration function identifies a change in magnetic signature from said magneto-responsive sensor reaching a limit of operation of said electronic circuit.

64. The vehicular electronic compass system in claim 63, wherein said electronic circuit calculates a zero reference value of the Earth magnetic field after adjusting said sensor.

65. The vehicular electronic compass system in claim 62, wherein said calibration function identifies a change in magnetic signature from an abnormal relation between collected data points and said zero reference value of the Earth magnetic field.

66. The vehicular electronic compass system in claim 65, wherein said abnormal relation comprises said zero reference value of the Earth magnetic field falling outside of opposite peak values of the Earth magnetic field.

67. The vehicular electronic compass system in claim 66, wherein said electronic circuit calculates a zero reference value of the Earth magnetic field after adjusting said sensor.

68. The vehicular electronic compass system in claim 62, wherein said electronic circuit occasionally calculates a zero reference value of the Earth magnetic field and wherein said calibration function identifies a change in magnetic signature from a change in said zero reference value of the Earth magnetic field which exceeds a predetermined amount.

69. The vehicular electronic compass system in claim 68, wherein said predetermined amount comprises a predetermined portion of an operating range of said electronic circuit.

70. The vehicular electronic compass system in claim 69, wherein said electronic circuit calculates a new zero reference value of the Earth magnetic field after adjusting said sensor.

71. The vehicular electronic compass system in claim 62, wherein said electronic circuit includes a digital-to-analog converter converting digital values to analog signals supplied to said magneto-responsive sensor for adjusting said magneto-responsive sensor.

72. The vehicular electronic compass system in claim 71, wherein said analog-to-digital converter converts outputs or said magneto-responsive sensor to digital signals, said analog-to-digital converter having a range of operation defining a limit of operation of said electronic circuit.

73. The vehicular electronic compass system in claim 62, wherein said magneto-responsive sensor comprises one of a magneto-inductive sensor, a magneto-resistive sensor, a magneto-capacitive sensor, and a flux gate sensor.

74. The vehicular electronic compass system in claim 62, wherein said magneto-responsive sensor comprises a magneto-resistive sensor.

75. The vehicular electronic compass system of claim 62, wherein said first axis and second axis sensing elements are oriented in a predetermined angular relationship with each other and in a predetermined orientation with respect to the vehicle.

76. The vehicular electronic compass system in claim 58, wherein said electronic circuit detects a third peak value of the Earth magnetic field by processing by said microprocessor of data sensed by the other one of said first axis and second axis sensing elements.

77. The vehicular electronic compass system of claim 76, wherein said electronic circuit algorithmically calculates a fourth peak value of the Earth magnetic field using said detected first, second and third peak values without a need for the vehicle to turn through a 360 degree circle.

78. The vehicular electronic compass system in claim 58, wherein said magneto-responsive sensor comprises one of a magneto-inductive sensor, a magneto-resistive sensor, a magneto-capacitive sensor and a flux gate sensor.

79. The vehicular electronic compass system in claim 58, wherein said magneto-responsive sensor comprises a magneto-resistive sensor.

80. The vehicular electronic compass system of claim 58, wherein said first axis and second axis sensing elements are oriented in a predetermined angular relationship with each other and in a predetermined orientation with respect to the vehicle.

81. The vehicular electronic compass system or claim 58, wherein said magneto-responsive sensor senses the Earth magnetic field and a deviating magnetic field and said electronic circuit adjusts said magneto-responsive sensor to substantially nullify the deviating magnetic field.

82. The vehicular electronic compass system in claim 58, wherein said another calibration mode accounts for relatively minor changes of the vehicle magnetic signature.

83. The vehicular electronic compass system in claim 82, wherein said another calibration mode encompasses at least two stages.

84. The vehicular electronic compass system claim 83, wherein at least one of said at least two stages comprises data gathering over multiple ignition cycles of the vehicle.

85. The vehicular electronic compass system in claim 58, wherein said another calibration mode brings the directional heading of the vehicle displayed by said electronic display within a tighter range of accuracy relative to the true Earth magnetic field than what is achieved during said initial calibration mode.

86. The vehicular electronic compass system in claim 58, wherein said electronic display comprises part of a vehicular mirror assembly.