Vehicle compass system with continuous automatic calibration

• US 7,458,166 B2
• Filed: 01/29/2008
• Issued: 12/02/2008
• Est. Priority Date: 05/27/1999
• Status: Expired due to Fees

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Olson, Thomas R., Slater, David J., Parks, Jeffrey N.
• Primary Examiner(s): BENNETT, GEORGE B
• Application Number:
  US12/022,039
• Publication Number:
  US 20080120054A1
• Time in Patent Office: 308 Days
• Field of Search: 333/55.R, 333/56, 333/57, 333/59, 333/61, 701/213, 701/214, 702/85, 702/92, 702/93, 702/94, 702/95
• US Class Current: 33/356
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

The compass system of the present invention utilizes an improved calibration route in which a processing circuit of the compass recalibrates the compass each time three data points are obtained from a magnetic field sensor that meet predetermined criteria. One such criterion is that the three data points define corners of a triangle that is substantially non-obtuse. When three data points have been obtained that define a triangle meeting this criterion, the processing circuit calculates a center point for a circle upon which all three data points lie by solving the equation x²+y²+Ax+By+C=0 for A, B, and C, using the coordinate values (x,y) for the three data points and defining the center point as (−A/2, −B/2).

Claims

1. A compass system configured to operate with a magnetic field sensor configured to provide magnetic field data in response to Earth'"'"'s magnetic field and a global position system configured to receive position data from a positioning satellite, the compass system comprising:

a processor coupled to the magnetic field sensor and to the global position data, the processor configured to receive the magnetic field data and data from the global positioning system, to process the data to compensate the data, and to provide a heading output based on the compensated data; and

a memory coupled to the processor, the memory configured to store compass compensation data.

2. The compass system of claim 1, further comprising an interface circuit configured to couple the magnetic field sensor to the processor.

3. The compass system of claim 2, wherein the interface circuit is configured to process electrical signals provided from the magnetic field sensor.

4. The compass system of claim 3, wherein

the magnetic field sensor comprises a first sensor sensitive to Earth'"'"'s magnetic field and a second sensor sensitive to Earth'"'"'s magnetic field, and

the interface circuit is configured to process electrical signals provided from the first sensor and the second sensor.

5. The compass system of claim 4, wherein an element of the first sensor that is sensitive to magnetic fields is arranged transverse to an element of the second sensor that is sensitive to magnetic fields.

6. The compass system of claim 1, further comprising a speed sensor coupled to the processor, the processor configured to process the compass data to compensate the compass data based on data from the speed sensor.

7. The compass system of claim 1, wherein the processor is a microprocessor and the memory is integrated with the microprocessor.

8. The compass system of claim 1, wherein the processor is configured to process the compass data to compensate the compass data by at least calculating smoothed data points, and calculating compensation data based on the smoothed data points.

9. The compass system of claim 8, wherein calculating smoothed data points, and calculating compensation data based on the smoothed data points at least includes receiving raw data based on signals from the magnetic field sensor, forming a first smoothed data point based on the raw data, forming a second smoothed data point based on the raw data, forming a third smoothed data point based on the raw data, and calculating compensation data based on the first, second, and third smoothed data points.

10. The compass system of claim 8, wherein the processor is configured to process the compass data to compensate the compass data by further determining whether the smoothed data points meet a criteria before using the smoothed data points to calculate the compensation data.

11. The compass system of claim 8, wherein the processor is configured to process the compass data to compensate the compass data by further using old compensation data stored in the memory.

12. A compass system, comprising:

a heading indicator configured to provide a heading output;

a magnetic field sensor configured to provide data in response to Earth'"'"'s magnetic field;

a global position system configured to receive position data from a positioning satellite;

a microprocessor coupled to the magnetic field sensor and the global positioning system, the microprocessor configured to receive data from the magnetic field sensor and the global positioning system, to process the data, and to provide a heading output to be displayed by the heading indicator.

13. The compass system of claim 12, further comprising an interface circuit configured to couple the magnetic field sensor to the microprocessor.

14. The compass system of claim 13, wherein the microprocessor is configured to send signals to the interface circuit to control the interface circuit.

15. The compass system of claim 14, wherein the microprocessor is configured to control a resolution of the interface circuit.

16. The compass system of claim 12, further comprising a speed sensor coupled to the microprocessor, the microprocessor configured to process the data to compensate the data based on data from the speed sensor.

17. The compass system of claim 12, wherein the microprocessor is configured to process data from the magnetic field sensor to compensate the data from the magnetic field sensor by at least calculating smoothed data points, and calculating compensation data based on the smoothed data points.

18. The compass system of claim 17, wherein

the compass system further comprises a memory configured to store compass data;

and

the microprocessor is configured to process the compass data to compensate the compass data by further using old compensation data stored in the memory.

19. A compass system mounted in a vehicle a display configured to provide a heading output data, comprising:

a magnetic field sensor configured to provide data in response to Earth'"'"'s magnetic field;

a global position system configured to receive position data from a positioning satellite;

a vehicle speed sensor configured to receive data indicative of a speed traveled by the vehicle;

a memory configured to store compass data; and

a processor coupled to the magnetic field sensor, the global positioning system, and the memory, the processor configured to receive data from the magnetic field sensor and the global positioning system and to process the data, the processor further configured to compensate the data from the magnetic field sensor based on compensation data from the memory, the processor still further configured to at least one of calculate compensation data and control a heading to be output based on data from the vehicle speed sensor.

20. The compass system mounted in a vehicle of claim 19, wherein the microprocessor is configured to control a heading displayed on the display based on data from the vehicle speed sensor.