Electronic compass and method of calibration

• US 20050223575A1
• Filed: 04/07/2005
• Published: 10/13/2005
• Est. Priority Date: 04/07/2004
• Status: Active Grant

• Current Assignee: Continental Automotive Systems, Inc. (Continental AG)
• Original Assignee: Siemens VDO Automotive Corporation (Siemens AG)
• Inventors: Bernard, Francois-Xavier, Fillatreau, Philippe
• Granted Patent: US 7,260,896 B2
• Time in Patent Office: Days
• US Class Current: 33/356
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

An electronic compass assembly includes a first collection portion and a second collection portion that each collect magnetic field data. The magnetic field data collected by the second collection portion partially overlaps the magnetic field data collected by the first collection portion. A processor module determines a calibration output based upon the magnetic field data from the first collection portion if a first predetermined condition exists and determines the calibration output based upon magnetic field data from the second collection portion if a second predetermined condition exists. An example method for controlling the electronic compass includes calibrating the electronic compass based upon one of a first magnetic field data set or a second, partially overlapping magnetic field data set. In another example, the processor module counts the number of magnetic field data points collected by one of the first magnetic field data set, the second magnetic field data set, or both, and determines a calibration output if the number exceeds a threshold. The processor module then uses acceptance criteria to determine whether to accept or reject the calibration output.

Claims

1. A method of controlling an electronic compass comprising:

calibrating an electronic compass based upon at least one of a first magnetic field data set or a second, partially overlapping magnetic field data set.

2. The method as recited in claim 1, including providing duplicate magnetic field data and different magnetic field data in each of the first magnetic field data set and the second magnetic field data set.

3. The method as recited in claim 1, including calibrating the electronic compass based upon the second, partially overlapping magnetic field data set if a predetermined time limit is exceeded.

4. The method as recited in claim 1, including statistically fitting at least one of the first magnetic field data set and the second magnetic field data set to produce a calibration output.

5. The method as recited in claim 4, including counting a number of magnetic field data points collected by at least one of the first magnetic field data or the second magnetic field data, and statistically fitting if the number exceeds a threshold number.

6. The method as recited in claim 4, including determining whether to accept or reject the calibration output based upon acceptance criteria.

7. The method as recited in claim 6, including determining the acceptance criteria based upon at least one of a magnetic field sensor parameter and a normalized statistical fitting error of the calibration output.

8. A method of calibrating an electronic compass comprising:

collecting magnetic field data from a first magnetic field data set; and

collecting partially overlapping magnetic field data from a second magnetic field data set.

9. A method as recited in claim 8, including collecting duplicate magnetic field data and different magnetic field data in each of the first magnetic field data set and the second magnetic field data set.

10. The method as recited in claim 8, including statistically fitting at least one of the first magnetic field data set or the second magnetic field data set to produce a calibration output.

11. The method as recited in claim 10, including determining a compass heading based upon the calibration output.

12. The method as recited in claim 10, including determining the calibration output based upon the first magnetic field data set if a first predetermined condition exists and determining the calibration based upon the second magnetic field data set if a second predetermined condition exists.

13. A method as recited in claim 12, including determining whether at least one of the first predetermined condition and the second predetermined condition exists based upon a predetermined time limit.

14. The method as recited in claim 13, including purging at least one of the first magnetic field data set or the second magnetic field data set based upon the predetermined time limit.

15. A compass assembly comprising:

a first collection portion and a second collection portion that each collect magnetic field data, and the magnetic field data collected by the second collection portion partially overlaps the magnetic field data collected by the first collection portion; and

a processor module that determines a calibration output based upon the magnetic field data from the first collection portion if a first predetermined condition exists and determines the calibration output based upon magnetic field data from the second collection portion if a second predetermined condition exists.

16. The assembly as recited in claim 15, wherein at least a portion of the data collected by the second collection portion is a duplicate of a portion of the data collected by the first collection portion.

17. The assembly as recited in claim 15, wherein the first predetermined condition includes being within a predetermined time limit.

18. The assembly as recited in claim 15, wherein the second predetermined condition includes exceeding a predetermined time limit.

19. The assembly as recited in claim 15, including a magnetic field sensing module that senses the magnetic field and produces output signals that correspond to the magnetic field data.

20. The assembly as recited in claim 15, including a compass display portion in communication with the processor module for displaying a vehicle direction based upon the calibration output.