Method, apparatus, and medium for calibrating compass sensor in consideration of magnetic environment and method, apparatus, and medium for measuring azimuth using the compass sensor calibration method, apparatus, and medium

• US 20080071492A1
• Filed: 08/23/2007
• Published: 03/20/2008
• Est. Priority Date: 09/20/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Hyoung-ki, Bang, Seok-won, Skvortsov, Vladimir
• Granted Patent: US 7,613,581 B2
• Time in Patent Office: Days
• US Class Current: 702/92
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A method of calibrating a compass sensor in consideration of a magnetic environment is provided. The method includes (a) acquiring magnetic force data by rotating a compass sensor 360 degrees, the compass sensor including a biaxial magnetometer, (b) fitting the acquired magnetic force data to an ellipse function, (c) transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin, and (d) calculating a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, the distortion factor indicating the degree to which a magnetic field is distorted.

Claims

1. A method of calibrating a compass sensor in consideration of a magnetic environment, the method comprising:

(a) acquiring magnetic force data by rotating the compass sensor 360 degrees, the compass sensor comprising a biaxial magnetometer;

(b) fitting the acquired magnetic force data to an ellipse function;

(c) transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin; and

(d) calculating a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, the distortion factor indicating the degree to which a magnetic field is distorted.

2. The method of claim 1, further comprising calculating quality of calibration by comparing the acquired magnetic force data and the ellipse function.

3. The method of claim 1, wherein the distortion factor is determined by one of a data soft iron error, an ellipse soft iron error, and a phase shift of the acquired magnetic force data in the x-axis and the y-axis, the data soft iron error corresponding to an inclination of a major axis of the acquired magnetic force data to a horizontal axis, and the ellipse soft iron error corresponding to an inclination of a major axis of an ellipse function to which the acquired magnetic force data is fit to the horizontal axis.

4. The method of claim 3, wherein the phase shift is an angle of a sine function value corresponding to a ratio of the sum of absolute values of two y-intercepts of predetermined data and a range of y value variations of the acquired magnetic force data, the predetermined data being obtained by moving the center of the acquired magnetic force data to the origin.

5. The method of claim 1, wherein the distortion factor is determined by a combination of a data soft iron error, an ellipse soft iron error, and a phase shift of the acquired magnetic force data in the x-axis and the y-axis, the data soft iron error corresponding to an inclination of a major axis of the acquired magnetic force data to a horizontal axis, and the ellipse soft iron error corresponding to an inclination of a major axis of the ellipse function to the horizontal axis.

6. The method of claim 2, wherein the quality of calibration is determined by one of a uniformity coefficient, an area ratio coefficient, and a fitting coefficient, the uniformity coefficient indicating whether magnetic force data has been evenly acquired from each direction with an angle of 0-360 degrees, the area ratio coefficient corresponding to a ratio of the area of the acquired magnetic force data and the area of an ellipse to which the acquired magnetic force data is fit, and the fitting coefficient corresponding to a ratio of the variance of the acquired magnetic force data and the variance of the ellipse.

7. The method of claim 2, wherein the quality of calibration is determined by a combination of a uniformity coefficient, an area ratio coefficient, and a fitting coefficient, the uniformity coefficient indicating whether magnetic force data has been evenly acquired from each direction with an angle of 0-360 degrees, the area ratio coefficient corresponding to a ratio of the area of the acquired magnetic force data and the area of an ellipse to which the acquired magnetic force data is fit, and the fitting coefficient corresponding to a ratio of the variance of the acquired magnetic force data and the variance of the ellipse.

8. The method of claim 1, wherein (a) comprises filtering the acquired magnetic force data by removing acquired magnetic force data that exceeds a predefined threshold.

9. A method of measuring the azimuth of a compass sensor in consideration of a magnetic environment, the method comprising:

(a) acquiring magnetic force data by rotating a compass sensor 360 degrees, the compass sensor comprising a biaxial magnetometer;

(b) fitting the acquired magnetic force data to an ellipse function;

(c) transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

(d) calculating a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, the distortion factor indicating the degree to which a magnetic field is distorted; and

(e) calculating the azimuth of the compass sensor based on calibrated data of the compass sensor if the distortion factor is within a predefined threshold range.

10. A method of measuring the azimuth of a compass sensor in consideration of a magnetic environment, the method comprising:

(a) acquiring magnetic force data by rotating a compass sensor 360 degrees, the compass sensor comprising a biaxial magnetometer;

(b) fitting the acquired magnetic force data to an ellipse function;

(c) transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

(d) calculating quality of calibration by comparing the acquired magnetic force data and the ellipse function; and

(e) calculating the azimuth of the compass sensor based on calibrated data of the compass sensor if the quality of calibration is within a predefined threshold range.

11. A method of measuring the azimuth of a compass sensor in consideration of a magnetic environment, the method comprising:

(a) acquiring magnetic force data by rotating a compass sensor 360 degrees, the compass sensor comprising a biaxial magnetometer;

(b) fitting the acquired magnetic force data to an ellipse function;

(c) transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

(d) calculating a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, and calculating quality of calibration by comparing the acquired magnetic force data and the ellipse function, the distortion factor indicating the degree to which a magnetic field is distorted; and

(e) calculating the azimuth of the compass sensor based on calibrated data of the compass sensor if the distortion factor and the quality of calibration are both within respective corresponding predefined threshold ranges.

12. An apparatus for calibrating a compass sensor in consideration of a magnetic environment, the apparatus comprising:

a data acquiring module which acquires magnetic force data by rotating a compass sensor 360 degrees, the compass sensor comprising a biaxial magnetometer;

an ellipse fitting module which fits the acquired magnetic force data to an ellipse function;

a compass calibration module which transforms the acquired magnetic force data and the ellipse function into a circle which is centered on an origin; and

a distortion factor calculation module which calculates a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, the distortion factor indicating the degree to which a magnetic field is distorted.

13. The apparatus of claim 12, further comprising a calibration quality calculation module which calculates quality of calibration by comparing the acquired magnetic force data and the ellipse function.

14. The apparatus of claim 12, wherein the distortion factor is determined by one of a data soft iron error, an ellipse soft iron error, and a phase shift of the acquired magnetic force data in the x-axis and the y-axis, the data soft iron error corresponding to an inclination of a major axis of the acquired magnetic force data to a horizontal axis, and the ellipse soft iron error corresponding to an inclination of a major axis of an ellipse function to which the acquired magnetic force data is fit to the horizontal axis.

15. The apparatus of claim 14, wherein the phase shift is an angle of a sine function value corresponding to a ratio of the sum of absolute values of two y-intercepts of predetermined data and a range of y value variations of the acquired magnetic force data, the predetermined data being obtained by moving the center of the acquired magnetic force data to the origin.

16. The apparatus of claim 12, wherein the distortion factor is determined by a combination of a data soft iron error, an ellipse soft iron error, and a phase shift of the acquired magnetic force data in the x-axis and the y-axis, the data soft iron error corresponding to an inclination of a major axis of the acquired magnetic force data to a horizontal axis, and the ellipse soft iron error corresponding to an inclination of a major axis of the ellipse function to the horizontal axis.

17. The apparatus of claim 13, wherein the quality of calibration is determined by one of a uniformity coefficient, an area ratio coefficient, and a fitting coefficient, the uniformity coefficient indicating whether magnetic force data has been evenly acquired from each direction with an angle of 0-360 degrees, the area ratio coefficient corresponding to a ratio of the area of the acquired magnetic force data and the area of an ellipse function to which the acquired magnetic force data is fit, and the fitting coefficient corresponding to a ratio of the variance of the acquired magnetic force data and the variance of the ellipse.

18. The apparatus of claim 13, wherein the quality of calibration is determined by a combination of a uniformity coefficient, an area ratio coefficient, and a fitting coefficient, the uniformity coefficient indicating whether magnetic force data has been evenly acquired from each direction with an angle of 0-360 degrees, the area ratio coefficient corresponding to a ratio of the area of the acquired magnetic force data and the area of an ellipse function to which the acquired magnetic force data is fit, and the fitting coefficient corresponding to a ratio of the variance of the acquired magnetic force data and the variance of the ellipse.

19. The apparatus of claim 12, wherein the data acquiring module comprises a data filter which filters the acquired magnetic force data by removing acquired magnetic force data that exceeds a predefined threshold.

20. An apparatus for measuring the azimuth of a compass sensor in consideration of a magnetic environment, the apparatus comprising:

a data acquiring module which acquires magnetic force data by rotating a compass sensor 360 degrees, the compass sensor comprising a biaxial magnetometer;

an ellipse fitting module which fits the acquired magnetic force data to an ellipse function;

a compass calibration module which transforms the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

a distortion factor calculation module which calculates a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, the distortion factor indicating the degree to which a magnetic field is distorted; and

an azimuth calculation module which calculates the azimuth of the compass sensor based on calibrated data of the compass sensor if the distortion factor is within a predefined threshold range.

21. An apparatus for measuring the azimuth of a compass sensor in consideration of a magnetic environment, the apparatus comprising:

a data acquiring module which acquires magnetic force data by rotating a compass sensor 360 degrees, the compass sensor comprising a biaxial magnetometer;

an ellipse fitting module which fits the acquired magnetic force data to an ellipse function;

a compass calibration module which transforms the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

a calibration quality calculation module which calculates quality of calibration by comparing the acquired magnetic force data and the ellipse function; and

an azimuth calculation module which calculates the azimuth of the compass sensor based on calibrated data of the compass sensor if the quality of calibration is within a predefined threshold range.

22. An apparatus for measuring the azimuth of a compass sensor in consideration of a magnetic environment, the apparatus comprising:

a data acquiring module which acquires magnetic force data by rotating a compass sensor 360 degrees, the compass sensor comprising a biaxial magnetometer;

an ellipse fitting module which fits the acquired magnetic force data to an ellipse function;

a compass calibration module which transforms the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

a distortion factor/calibration quality calculation module which calculates a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, and calculates quality of calibration by comparing the acquired magnetic force data and the ellipse function, the distortion factor indicating the degree to which a magnetic field is distorted; and

an azimuth calculation module which calculates the azimuth of the compass sensor based on calibrated data of the compass sensor if the distortion factor and the quality of calibration are both within respective corresponding predefined threshold ranges.

23. At least one computer readable medium storing computer readable instructions that control at least one processor to implement a method for calibrating a compass sensor in consideration of a magnetic environment, the method comprising:

fitting acquired magnetic force data acquired by the compass sensor to an ellipse function;

transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin; and

calculating a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, the distortion factor indicating a degree to which a magnetic field is distorted.

24. At least one computer readable medium storing computer readable instructions that control at least one processor to implement a method for measuring the azimuth of a compass sensor in consideration of a magnetic environment, the method comprising:

fitting acquired magnetic force data acquired by the compass sensor to an ellipse function;

transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

calculating a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, the distortion factor indicating the degree to which a magnetic field is distorted; and

calculating the azimuth of the compass sensor based on calibrated data of the compass sensor if the distortion factor is within a predefined threshold range.

25. At least one computer readable medium storing computer readable instructions that control at least one processor to implement a method of measuring the azimuth of a compass sensor in consideration of a magnetic environment, the method comprising:

fitting acquired magnetic force data acquired by the compass sensor to an ellipse function;

transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

calculating quality of calibration by comparing the acquired magnetic force data and the ellipse function; and

calculating the azimuth of the compass sensor based on calibrated data of the compass sensor if the quality of calibration is within a predefined threshold range.

26. At least one computer readable medium storing computer readable instructions that control at least one processor to implement a method of measuring the azimuth of a compass sensor in consideration of a magnetic environment, the method comprising:

fitting acquired magnetic force data acquired by the compass sensor to an ellipse function;

transforming the acquired magnetic force data and the ellipse function into a circle which is centered on an origin;

calculating a distortion factor based on an inclination of a major axis of the ellipse function or the acquired magnetic force data to a horizontal axis, and calculating quality of calibration by comparing the acquired magnetic force data and the ellipse function, the distortion factor indicating the degree to which a magnetic field is distorted; and

calculating the azimuth of the compass sensor based on calibrated data of the compass sensor if the distortion factor and the quality of calibration are both within respective corresponding predefined threshold ranges.