Vehicle compass compensation

• US 8,001,696 B2
• Filed: 08/03/2009
• Issued: 08/23/2011
• 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: DeVette, Gregory H., Hoekstra, Eric J., Veiseh, Merdad, Schofield, Kenneth, Blank, Rodney K., Schierbeek, Kenneth L.
• Primary Examiner(s): GUADALUPE, YARITZA
• Application Number:
  US12/534,549
• Publication Number:
  US 20090292496A1
• Time in Patent Office: 750 Days
• Field of Search: 333/56, 333/55.R, 333/57, 333/58, 333/59, 335/02
• US Class Current: 33/356
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A calibration method for calibrating a compass system suitable for use in a vehicle includes sampling data points of a magnetic field with a magneto-responsive sensor and processing output signals of the sensor via compass circuitry. The compass circuitry includes an analog-to-digital converter for converting analog signals of the sensor to digital signals and a digital-to-analog converter for converting digital signals to analog signals that are supplied to the sensor for adjusting the sensor. The output signals of the sensor are adjusted to be within an operable range of an analog-to-digital converter via an initial calibration mode. After completion of the initial calibration mode, output signals of the sensor are processed to determine when the output signals are outside a range of the analog-to-digital converter. An output of a digital-to-analog converter is adjusted to reposition the output signals of the sensor to be within the range of the analog-to-digital converter.

Claims

1. A calibration method for calibrating a compass system suitable for use in a vehicle, said calibration method comprising:

sampling data points of a magnetic field with a magneto-responsive sensor;

processing output signals of said magneto-responsive sensor via compass circuitry, wherein said compass circuitry comprises (a) an analog-to-digital converter for converting analog signals of said magneto-responsive sensor to digital signals and (b) a digital-to-analog converter for converting digital signals to analog signals that are supplied to said magneto-responsive sensor for adjusting said magneto-responsive sensor;

adjusting said output signals of said magneto-responsive sensor to be within an operable range of said analog-to-digital converter via an initial calibration mode;

after completion of said initial calibration mode, processing output signals of said magneto-responsive sensor to determine when said output signals are outside a range of said analog-to-digital converter; and

adjusting an output of said digital-to-analog converter to reposition said output signals of said magneto-responsive sensor to be within said range of said analog-to-digital converter.

2. The calibration method of claim 1, further comprising displaying directional heading information responsive to said compass circuitry.

3. The calibration method of claim 1, wherein sampling data points comprises sampling data points of a magnetic field with a magneto-responsive sensor that comprises at least a two-axis sensor for sensing at least two components of a magnetic field, and wherein said magneto-responsive sensor comprises 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 equipped with said magneto-responsive sensor.

4. The calibration method of claim 3, wherein said initial calibration mode comprises:

determining coordinates for the sampled data points relative to an origin of a coordinate system associated with the vehicle and identifying coordinates of a peak of the Earth magnetic field from the coordinates of the sampled data points;

assuming an assumed value of the Earth magnetic field magnitude based on the surface of the Earth where said sampling of the data points is occurring;

estimating an origin of an Earth magnetic field from the assumed value of the Earth magnetic field magnitude and the coordinates of the peak of the Earth magnetic field; and

adjusting said magneto-responsive sensor by applying magnetic biasing to said magneto-responsive sensor based on said estimating in order to offset the estimated origin of the Earth magnetic field to the coordinate system associated with the vehicle.

5. The calibration method of claim 1, wherein sampling data points comprises sensing the Earth magnetic field and a deviating magnetic field via said magneto-responsive sensor, and wherein said method comprises adjusting said magneto-responsive sensor to substantially nullify the deviating magnetic field.

6. The calibration method of claim 1, wherein said adjusting output signals of said magneto-responsive sensor to be within an operable range of an analog-to-digital converter utilizes an assumed value of the Earth magnetic field.

7. The calibration method of claim 1, wherein adjusting an output of said digital-to-analog converter comprises adjusting an output of said digital-to-analog converter to substantially center said output signals of said magneto-responsive sensor within said range of said analog-to-digital converter.

8. The calibration method of 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.

9. The calibration method of claim 1, wherein said magneto-responsive sensor comprises a magneto-resistive sensor.

10. A calibration method for calibrating a compass system suitable for use in a vehicle, said calibration method comprising:

sampling data points of a magnetic field with a magneto-responsive sensor, wherein said magneto-responsive sensor comprises a first axis sensing element and a second axis sensing element, and wherein one of said first axis sensing element and said second axis sensing element is generally aligned with a direction of travel of a vehicle equipped with said magneto-responsive sensor, and wherein sampling data points comprises sensing the Earth magnetic field and a deviating magnetic field via said magneto-responsive sensor, and wherein said method comprises adjusting said magneto-responsive sensor to substantially nullify the deviating magnetic field;

processing output signals of said magneto-responsive sensor via compass circuitry, wherein said compass circuitry comprises (a) an analog-to-digital converter for converting analog signals of said magneto-responsive sensor to digital signals and (b) a digital-to-analog converter for converting digital signals to analog signals that are supplied to said magneto-responsive sensor for adjusting said magneto-responsive sensor;

adjusting said output signals of said magneto-responsive sensor to be within an operable range of said analog-to-digital converter via an initial calibration mode utilizing an assumed value of the Earth magnetic field;

after completion of said initial calibration mode, processing output signals of said magneto-responsive sensor to determine when said output signals are outside a range of said analog-to-digital converter; and

adjusting an output of said digital-to-analog converter to reposition said output signals of said magneto-responsive sensor to be within said range of said analog-to-digital converter.

11. The calibration method of claim 10, further comprising displaying directional heading information responsive to said compass circuitry.

12. The calibration method of claim 10, wherein said initial calibration mode comprises:

determining coordinates for the sampled data points relative to an origin of a coordinate system associated with the vehicle and identifying coordinates of a peak of the Earth magnetic field from the coordinates of the sampled data points;

assuming an assumed value of the Earth magnetic field magnitude based on the surface of the Earth where said sampling of the data points is occurring;

estimating an origin of an Earth magnetic field from the assumed value of the Earth magnetic field magnitude and the coordinates of the peak of the Earth magnetic field; and

adjusting said magneto-responsive sensor by applying magnetic biasing to said magneto-responsive sensor based on said estimating in order to offset the estimated origin of the Earth magnetic field to the coordinate system associated with the vehicle.

13. The calibration method of claim 10, wherein adjusting an output of said digital-to-analog converter comprises adjusting an output of said digital-to-analog converter to substantially center said output signals of said magneto-responsive sensor within said range of said analog-to-digital converter.

14. The calibration method of claim 10, wherein said magneto-responsive sensor comprises a magneto-resistive sensor.

15. A calibration method for calibrating a compass system suitable for use in a vehicle, said calibration method comprising:

sampling data points of a magnetic field with a magneto-responsive sensor, 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;

processing output signals of said magneto-responsive sensor via compass circuitry, wherein said compass circuitry comprises (a) an analog-to-digital converter for converting analog signals of said magneto-responsive sensor to digital signals and (b) a digital-to-analog converter for converting digital signals to analog signals that are supplied to said magneto-responsive sensor for adjusting said magneto-responsive sensor;

adjusting said output signals of said magneto-responsive sensor to be within an operable range of said analog-to-digital converter via an initial calibration mode;

after completion of said initial calibration mode, processing output signals of said magneto-responsive sensor to determine when said output signals are outside a range of said analog-to-digital converter;

adjusting an output of said digital-to-analog converter to reposition said output signals of said magneto-responsive sensor to be within said range of said analog-to-digital converter; and

displaying directional heading information responsive to said compass circuitry.

16. The calibration method of claim 15, wherein sampling data points comprises sampling data points of a magnetic field with a magneto-responsive sensor that comprises at least a two-axis sensor for sensing at least two components of a magnetic field, and wherein said magneto-responsive sensor comprises 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 equipped with said magneto-responsive sensor.

17. The calibration method of claim 16, wherein said initial calibration mode comprises:

determining coordinates for the sampled data points relative to an origin of a coordinate system associated with the vehicle and identifying coordinates of a peak of the Earth magnetic field from the coordinates of the sampled data points;

assuming an assumed value of the Earth magnetic field magnitude based on the surface of the Earth where said sampling of the data points is occurring;

estimating an origin of an Earth magnetic field from the assumed value of the Earth magnetic field magnitude and the coordinates of the peak of the Earth magnetic field; and

adjusting said magneto-responsive sensor by applying magnetic biasing to said magneto-responsive sensor based on said estimating in order to offset the estimated origin of the Earth magnetic field to the coordinate system associated with the vehicle.

18. The calibration method of claim 15, wherein sampling data points comprises sensing the Earth magnetic field and a deviating magnetic field via said magneto-responsive sensor, and wherein said method comprises adjusting said magneto-responsive sensor to substantially nullify the deviating magnetic field.

19. The calibration method of claim 18, wherein said adjusting output signals of said magneto-responsive sensor to be within an operable range of an analog-to-digital converter utilizes an assumed value of the Earth magnetic field.

20. The calibration method of claim 15, wherein adjusting an output of said digital-to-analog converter comprises adjusting an output of said digital-to-analog converter to substantially center said output signals of said magneto-responsive sensor within said range of said analog-to-digital converter.