Vehicle compass compensation

• US 20050262714A1
• Filed: 07/08/2005
• Published: 12/01/2005
• Est. Priority Date: 04/08/1999
• Status: Active Grant

• Current Assignee: Eric J. Hoekstra, Gregory H. Devette, Kenneth L. Schierbeek, Kenneth Schofield, Merdad Veiseh, Rodney K. Blank
• Original Assignee: Eric J. Hoekstra, Gregory H. Devette, Kenneth L. Schierbeek, Kenneth Schofield, Merdad Veiseh, Rodney K. Blank
• Inventors: Schofield, Kenneth, Blank, Rodney K., Schierbeek, Kenneth L., DeVette, Gregory H., Hoekstra, Eric J., Veiseh, Merdad
• Granted Patent: US 7,331,115 B2
• Time in Patent Office: Days
• 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

1-48. -48. (canceled)

49. A calibration method for calibrating a compass for use on a vehicle, said method comprising:

sampling at least one data point of a magnetic field with a magnetic sensor;

determining coordinates for said at least one data point relative to an origin of a coordinate system associated with the vehicle;

estimating an origin of an Earth magnetic field from an estimated value of the Earth magnetic field magnitude and at least one data point; and

adjusting the sensor to offset the estimated origin to the coordinate system associated with the vehicles.

50. The calibration method of claim 49 further comprising:

sampling pair of data points that are substantially oppositely positioned relative to one axis of said coordinate system;

averaging the substantially opposite values of said pair of data points to determine deviation from a zero value of the coordinate system; and

adjusting an output of the system as a function of said deviation.

51. The calibration method of claim 50 further comprising validating said deviation by comparing said deviation with another value determined by a different technique.

52. The calibration method of claim 51 including sampling additional data points if said deviation is not valid.

53. A calibration method for calibrating a compass system for use on a vehicle, said method comprising:

sampling at least one pair of data points that are substantially oppositely positioned relative to an axis of a coordinate system;

averaging the substantially opposite values of said pair of data points to determine deviation from a zero value of the coordinate system; and

adjusting an output of the compass system as a function of said deviation.

54. The calibration method of claim 53 further comprising validating said deviation by comparing said deviation with another value determined by a different technique.

55. The calibration method of claim 54 including sampling additional data points if said deviation is not valid.

56. A calibration method for calibrating a compass for use on a vehicle, comprising:

collecting data points with a sensor assembly, determining from the collected data points an offset value of the Earth magnetic field, and adjusting a directional heading output of said sensor assembly to account for said offset; and

identifying a change in magnetic signature from at least one of said sensor assembly and said offset value and adjusting said sensor assembly in response to a change in magnetic signature.

57. The calibration method of claim 56 wherein a change in magnetic signature is identified from said sensor reaching a limit of operation of said electronic circuit.

58. The calibration method of claim 56 wherein a change in magnetic signature is identified from an abnormal relation between collected data points and said offset.

59. The calibration method of claim 56 wherein a change in magnetic signature is identified from an abnormal relation between collected data points and said offset.

60. The calibration method of claim 59 wherein said abnormal relation comprises said offset falling outside of opposite peak values of data points.