Electronic compass and method for tracking vehicle rotation

• US 7,225,551 B2
• Filed: 04/07/2005
• Issued: 06/05/2007
• Est. Priority Date: 04/07/2004
• Status: Expired due to Fees

• Current Assignee: Continental Automotive Systems, Inc. (Continental AG)
• Original Assignee: Siemens VDO Automotive Corporation (Siemens AG)
• Inventors: Bernard, Francois-Xavier, Fillatreau, Philippe
• Primary Examiner(s): SMITH, RICHARD A
• Application Number:
  US11/101,281
• Publication Number:
  US 20050223574A1
• Time in Patent Office: 789 Days
• Field of Search: 333/56, 333/57, 333/55.R, 73/17.6, 701/224, 702/92, 702/93
• US Class Current: 33/356
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

An example method for controlling an electronic compass includes determining compass tracking angles in a coordinate system for magnetic field data points that correspond to magnetic field sensor signals produced as a vehicle rotates relative to a surrounding magnetic field. The magnetic field data points produce an expected curve in the coordinate system. The rotation of the vehicle is tracked relative to the surrounding magnetic field based upon the compass tracking angles and whether the vehicle has rotated a desired amount is determined based at least partially upon the expected curve and the compass tracking angles.

Claims

1. A method of controlling an electronic compass assembly comprising:

determining compass tracking angles in a coordinate system for magnetic field data points that correspond to magnetic field sensor signals produced as a vehicle rotates relative to a surrounding magnetic field, the magnetic field data points producing an expected curve in the coordinate system;

tracking rotation of the vehicle relative to the surrounding magnetic field based upon the compass tracking angles; and

determining whether the vehicle has rotated a desired amount based at least partially upon the expected curve and the compass tracking angles.

2. The method as recited in claim 1, including determining the compass tracking angles such that rotation of the vehicle through the desired amount is recognized when the expected curve includes a desirable mathematical feature and not recognized when the expected curve does not include the desirable mathematical feature.

3. The method as recited in claim 1, including determining a calibration curve based upon the magnetic field data points if the expected curve includes a desirable mathematical feature and if the vehicle has rotated a desired amount based upon the compass tracking angles.

4. The method as recited in claim 3, including determining whether the mathematical feature is desirable based upon a predetermined factor included in the determination of the compass tracking angles.

5. The method as recited in claim 4, including calculating a plurality of displacement lines that each extend between two magnetic field data points, calculating a plurality of first reference lines that each correspond to one of the displacement lines, each first reference line having a predetermined angular relationship to the corresponding displacement line and intersecting one of the two magnetic field data points.

6. The method as recited in claim 5, including calculating a plurality of second reference lines that each correspond to one of the first reference lines, each second reference line intersecting the corresponding first reference line and having a predetermined direction in the coordinate system, calculating an angle between each first reference line and the corresponding second reference line to produce one compass tracking angle.

7. The method as recited in claim 6, including storing each compass tracking angle within one of a plurality of angular ranges that each correspond to an increment of the desired amount of vehicle rotation and determining the calibration curve when each of the plurality of angular ranges includes a stored compass tracking angle.

8. The method as recited in claim 6, including storing each compass tracking angle within one of a plurality of angular ranges that each correspond to an increment of the desired amount of vehicle rotation, and determining that the vehicle has rotated the desired amount when each of the plurality of angular ranges includes a stored compass tracking angle.

9. The method as recited in claim 6, including establishing a point of reference along each of the plurality of first reference lines that is a predetermined distance from one magnetic field data point such that the point of reference has a desired orientation with respect to the displacement line that corresponds to the first reference line that the point of reference is on.

10. A method of controlling an electronic compass assembly comprising:

establishing a first magnetic field data point and a second magnetic field data point in a coordinate system;

determining a compass tracking angle that corresponds to one of the first magnetic field data point or the second magnetic field data point based upon a relationship of the first magnetic field data point to the second magnetic field data point; and

selecting a location of a point of reference corresponding to the second magnetic field data point from a plurality of possible locations that are each a predetermined distance from the second magnetic field data point.

11. The method as recited in claim 10, including selecting the location of the point of reference based upon a line between the first magnetic field data point and the second magnetic field data point.

12. The method as recited in claim 11, including establishing an other point of reference that corresponds to the first magnetic field data point and that is the predetermined distance from the first magnetic field data point, and selecting the location of the point of reference from the plurality of locations based upon comparison of the distance between each of the plurality of locations and the other point of reference.

13. The method as recited in claim 10, including selecting the location of the point of reference based upon a vector between the first magnetic field data point and the second magnetic field data point.

14. The method as recited in claim 13, including establishing an other point of reference that corresponds to the first magnetic field data point and that is the predetermined distance from the first magnetic field data point, determining a second vector extending from the other point of reference to the first magnetic field data point, determining an orientation of the second vector relative to the vector between the first magnetic field data point and the second magnetic field data point, and establishing the point of reference based upon the orientation.

15. The method as recited in claim 14, including calculating the orientation of the second vector relative to the vector between the first magnetic field data point and the second magnetic field data point as being one of a clockwise orientation or a counterclockwise orientation, determining a third vector extending from the point of reference such that the orientation of the third vector relative to the vector between the first magnetic field data point and the second magnetic field data point is identical to the orientation of the second vector relative to the vector between the first magnetic field data point and the second magnetic field data point.

16. The method as recited in claim 15, including calculating a first determinant of the second vector relative to the vector between the first magnetic field data point and the second magnetic field data point and calculating a second determinant of the third vector relative to the vector between the first magnetic field data point and the second magnetic field data point, and comparing the first determinant to the second determinant to determine if the orientation of the third vector relative to the vector between the first magnetic field data point and the second magnetic field data point is identical to the orientation of the second vector relative to the vector between the first magnetic field data point and the second magnetic field data point.

17. An electronic compass assembly comprising:

a processor module for controlling an electronic compass assembly, the processor module being operable to determine whether a vehicle has rotated a desired amount of vehicle rotation based at least partially upon compass tracking angles collected through rotation of the vehicle, the processor module being configured to;

receive a first magnetic field data point and a second magnetic field data point for determining one of the compass tracking angles and calculate a displacement line that extends between them;

calculate a first reference line having a predetermined angular relationship to the displacement line and intersecting the second magnetic field data point;

establish a second reference line having a predetermined direction and intersecting the first reference line; and

calculate an angle between the first reference line and the second reference line, the angle being one of the compass tracking angles.

18. The assembly as recited in claim 17, wherein the predetermined angular relationship is 90°

.

19. The method as recited in claim 17, including storing the angle within one of a plurality of angular ranges that each correspond to an increment of the desired amount of vehicle rotation, and determining that the vehicle has rotated the desired amount of vehicle rotation when each of the plurality of angular ranges includes a stored angle.

20. The method as recited in claim 17, including establishing a point of reference along the first reference line such that the point of reference has a desired vectorial orientation with respect to a vector along the displacement line.