Vehicle compass compensation

• US 7,568,290 B2
• Filed: 02/15/2008
• Issued: 08/04/2009
• 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): GUADALUPE, YARITZA
• Application Number:
  US12/032,308
• Publication Number:
  US 20080140332A1
• Time in Patent Office: 536 Days
• Field of Search: 333/55.R, 333/56, 333/57, 335/02, 33358-359, 333/33, 324/244, 324/202, 324/225, 324/247, 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 having automatic calibration, said vehicular electronic compass system comprising:

a magneto-responsive sensor, wherein said magneto-responsive sensor comprises at least first and second magneto-responsive sensing elements;

a control, said control receiving input indicative of a magnetic field sensed by said magneto-responsive sensor;

said control distinguishing the Earth magnetic field from a deviating magnetic field of the vehicle in order to determine a directional heading of the vehicle;

said control operable in at least a first calibration mode and a second calibration mode;

said first calibration mode providing an ideal offsetting of the deviating magnetic field of the vehicle, said first calibration mode encompassing at least one of (a) a physical adjustment of the output of said magneto-responsive sensor and (b) an algorithmic adjustment;

wherein said first calibration mode at least partially calibrates said vehicular electronic compass system to within a first tolerance of the true Earth magnetic field;

an electronic display responsive to said control and displaying a first calibrated directional heading of the vehicle to the driver of the vehicle when said electronic compass system is in said first calibration mode, wherein said electronic display displays said first calibrated directional heading without requiring the vehicle to be driven in a complete 360 degree circle;

said vehicular electronic compass system automatically progressing to said second calibration mode;

said second calibration mode providing further calibration of said vehicular electronic compass system to within a second tolerance of the true Earth magnetic field, wherein said second tolerance of said second calibration mode is closer to the true Earth magnetic field than said first tolerance of said first calibration mode, said further calibration being principally achieved algorithmically; and

wherein said electronic display displays a second calibrated directional heading of the vehicle when said electronic compass system is in said second calibration mode, and wherein said second calibration mode generally maintains the calibration within said second tolerance.

2. The vehicular electronic compass system of claim 1, wherein said magneto-responsive sensor comprises at least 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 of claim 1, wherein said magneto-responsive sensor comprises a magneto-inductive sensor.

4. The vehicular electronic compass system of claim 1, wherein said first and second magneto-responsive 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 4, wherein said first magneto-responsive sensing element is generally aligned with a direction of travel of the vehicle when the vehicular electronic compass system is operated in the vehicle.

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

7. The vehicular electronic compass system of claim 1, wherein said initial offsetting of the deviating magnetic field of the vehicle utilizes an assumed value of the Earth magnetic field.

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

9. The vehicular electronic compass system of claim 1, wherein said second calibration mode accounts for relatively mirror changes of the deviating magnetic field of the vehicle.

10. The vehicular electronic compass system of claim 1, wherein said second calibration mode comprises data gathering over multiple ignition cycles of the vehicle.

11. The vehicular electronic compass system of claim 1, wherein said control is operable in a third calibration mode, and wherein said third calibration mode comprises multiple confirmations of changes in detected magnetic anomalies.

12. The vehicular electronic compass system of claim 11, wherein said control, when operating in said third calibration mode, identifies a change in the deviating magnetic field of the vehicle from said magneto-responsive sensor reaching a limit of operation of said control.

13. The vehicular electronic compass system of claim 12, wherein said control calculates a zero reference value of the Earth magnetic field after adjusting said magneto-responsive sensor, and wherein said control identifies a change in the deviating magnetic field of the vehicle from an abnormal relation between collected data points and said zero reference value of the Earth magnetic field, and 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.

14. The vehicular electronic compass system of claim 11, wherein said control occasionally calculates a zero reference value of the Earth magnetic field and wherein said control, when operating in said third calibration mode, identifies a change in the deviating magnetic field of the vehicle from a change in said zero reference value of the Earth magnetic field which exceeds a predetermined amount.

15. A vehicular electronic compass system having automatic calibration, said vehicular electronic compass system comprising:

a magneto-responsive sensor, wherein said magneto-responsive sensor comprises at least first and second magneto-responsive sensing elements;

wherein said first and second magneto-responsive sensing elements are oriented in a predetermined angular relationship with each other and in a predetermined orientation with respect to the vehicle, and wherein said first magneto-responsive sensing element is generally aligned with a direction of travel of the vehicle when the vehicular electronic compass system is operated in the vehicle;

a control, said control receiving input indicative of a magnetic field sensed by said magneto-responsive sensor;

said control distinguishing the Earth magnetic field from a deviating magnetic field of the vehicle in order to determine a directional heading of the vehicle;

said control operable in at least a first calibration mode and a second calibration mode;

said first calibration mode providing an initial offsetting of the deviating magnetic field of the vehicle, said first calibration mode encompassing at least one of (a) a physical adjustment of the output of said magneto-responsive sensor and (b) an algorithmic adjustment;

wherein said first calibration mode at least partially calibrates said vehicular electronic compass system to within a first tolerance of the true Earth magnetic field;

an electronic display, said electronic display comprising part of a vehicular mirror assembly;

wherein said electronic display is responsive to said control and displays a first calibrated directional heading of the vehicle to the driver of the vehicle when said electronic compass system is in said first calibration mode, wherein said electronic display displays said first calibrated directional heading without requiring the vehicle to be driven in a complete 360 degree circle;

said vehicular electronic compass system automatically progressing to said second calibration mode;

said second calibration mode providing further calibration of said vehicular electronic compass system to within a second tolerance of the true Earth magnetic field, wherein said second tolerance of said second calibration mode is closer to the true Earth magnetic field than said first tolerance of said first calibration mode, said further calibration being principally achieved algorithmically; and

wherein said electronic display displays a second calibrated directional heading of the vehicle when said electronic compass system is in said second calibration mode, and wherein said second calibration mode generally maintains the calibration within said second tolerance.

16. The vehicular electronic compass system of claim 15, wherein said second calibration mode comprises data gathering over multiple ignition cycles of the vehicle.

17. The vehicular electronic compass system of claim 15, wherein said control is operable in a third calibration mode, and wherein said third calibration mode comprises multiple confirmations of changes in detected magnetic anomalies.

18. A vehicular electronic compass system having automatic calibration, said vehicular electronic compass system comprising:

a magneto-responsive sensor, wherein said magneto-responsive sensor comprises at least first and second magneto-responsive sensing elements;

a control, said control receiving input indicative of a magnetic field sensed by said magneto-responsive sensor;

said control distinguishing the Earth magnetic field from a deviating magnetic field of the vehicle in order to determine a directional heading of the vehicle;

said control operable in at least a first calibration mode and a second calibration mode;

said first calibration mode providing an initial offsetting of the deviating magnetic field of the vehicle, said first calibration mode encompassing at least one of (a) a physical adjustment of the output of said magneto-responsive sensor and (b) an algorithmic adjustment;

wherein said initial offsetting of the deviating magnetic field of the vehicle utilizes an assumed value of the Earth magnetic field, and wherein said first calibration mode at least partially calibrates said vehicular electronic compass system to within a first tolerance of the true Earth magnetic field;

an electronic display, said electronic display comprising part of a vehicular mirror assembly;

wherein said electronic display is responsive to said control and displays a first calibrated directional heading of the vehicle to the driver of the vehicle when said electronic compass system is in said first calibration mode, wherein said electronic display displays said first calibrated directional heading without requiring the vehicle to be driven in a complete 360 degree circle;

said vehicular electronic compass system automatically progressing to said second calibration mode;

said second calibration mode providing further calibration of said vehicular electronic compass system to within a second tolerance of the true Earth magnetic field, wherein said said first tolerance of said first calibration mode, said further calibration being principally achieved algorithmically; and

wherein said electronic display displays a second calibrated directional heading of the vehicle when said electronic compass system is in said second calibration mode, and wherein said second calibration mode generally maintains the calibration within said second tolerance.

19. The vehicular electronic compass system of claim 18, wherein said second calibration mode comprises data gathering over multiple ignition cycles of the vehicle.

20. The vehicular electronic compass system of claim 18, wherein said control is operable in a third calibration mode, and wherein said third calibration mode comprises multiple confirmations of changes in detected magnetic anomalies.