Geomagnetic sensor for informing users whether detected azimuth angle is acceptable, and a method thereof

• US 7,168,176 B2
• Filed: 02/28/2005
• Issued: 01/30/2007
• Est. Priority Date: 02/26/2004
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Choi, Sang-on, Lee, Woo-jong
• Primary Examiner(s): SMITH, RICHARD A
• Application Number:
  US11/067,208
• Publication Number:
  US 20050188556A1
• Time in Patent Office: 701 Days
• Field of Search: 333/55.R, 333/56, 333/57, 333/61, 333/62, 701/93, 701/224, 702/92, 702/93, 73/17.6, 324/225, 324/247, 324/253, 324/254, 324/255, 324/260
• US Class Current: 33/356
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A geomagnetic sensor which informs a user that information with respect to a distorted azimuth angle may be detected. The geomagnetic sensor includes a geomagnetism detection module including an X axis fluxgate and a Y axis fluxgate orthogonal to each other and detecting a predetermined amount of electrical signals corresponding to a geomagnetism of each of the fluxgates; a signal processing unit for converting the electrical signal output from the geomagnetism detection module to predetermined X axis and Y axis output values and outputting them; a display unit for displaying a predetermined warning message on a screen; and a control unit for determining whether the output values of the X and Y axes are distorted, and controlling the display unit to display the predetermined warning message upon determination that the output values are distorted. Accordingly, the possibility of a distorted azimuth angle may be detected and informed to a user.

Claims

1. A geomagnetic sensor, comprising:

a geomagnetism detection module including an X axis fluxgate comprising a first magnetic core and a Y axis fluxgate comprising a second magnetic core and detecting a geomagnetism of the X axis fluxgate when the X axis fluxgate is driven by a first signal and a geomagnetism of the Y axis fluxgate when the Y axis is driven by a second signal;

a signal processing unit for converting signal outputs from the geomagnetism detection module to X axis and Y axis output values; and

a control unit for determining whether the output values of the X and Y axes are distorted, and providing a warning message upon determination that at least one of the output values is distorted.

2. The geomagnetic sensor as recited in claim 1, wherein the control unit normalizes the output values of the X and Y axes to values in a predetermined tolerable range, and determines that at least one of the output values of the X and Y axes is distorted when each of the normalized output values which is squared and together is out of the predetermined tolerable range.

3. The geomagnetic sensor as recited in claim 2, wherein the control unit normalizes the output values of the X and Y axes using the following formulae:

$\mathrm{nX}=\frac{\left(X-X_{\mathrm{bias}}\right)}{X_{\mathrm{scale}}},X_{\mathrm{bias}}=\frac{\left(X_{\max }+X_{\min }\right)}{2},X_{\mathrm{scale}}=\frac{\left(X_{\max }-X_{\min }\right)}{2}$ $\mathrm{nY}=\frac{\left(Y-Y_{\mathrm{bias}}\right)}{Y_{\mathrm{scale}}},Y_{\mathrm{bias}}=\frac{\left(Y_{\max }+Y_{\min }\right)}{2},Y_{\mathrm{scale}}=\frac{\left(Y_{\max }-Y_{\min }\right)}{2}$

wherein X and Y indicate the output values of the X and Y axes, respectively, nX and nY indicate the normalization values of the X and Y axes, respectively, Xmax and Xmin indicate maximum and minimum values of the X axis, respectively, and Ymax and Ymin indicate maximum and minimum values of the Y axis, respectively.

4. The geomagnetic sensor as recited in claim 3, wherein the control unit applies the normalized output values of the X and Y axes to the following formula to calculate an azimuth angle ψ

;

ψ

= tan^{31 1}(Y/X)

wherein X and Y are normalized output values of the X and Y axes, respectively, and ψ

is an azimuth angle.

5. The geomagnetic sensor as recited in claim 1, further comprising:

a memory for storing information about a maximum output value and a minimum output value of each of the X and Y axis fluxgates.

6. The geomagnetic sensor as recited in claim 1, wherein the X axis and Y axis fluxgates are orthogonal to each other.

7. The geomagnetic sensor as recited in claim 1, further comprising a display unit;

wherein said control unit is operable to control said display unit to display a predetermined warning message upon determination that at least one of the output values is distorted.

8. The geomagnetic sensor as recited in claim 1, wherein the first signal is inverted with respect to the second signal.

9. The geomagnetic sensor as recited in claim 1, wherein the first signal has an opposite phase with respect to the second signal.

10. A method for measuring an azimuth angle of a geomagnetic sensor having an X axis fluxgate and a Y axis fluxgate, comprising:

(a) detecting X axis output values corresponding to a geomagnetism from the X axis fluxgate when the X axis fluxgate is driven by a first signal;

(b) determining Y axis output values corresponding to a geomagnetism from the X axis fluxgate when the Y axis fluxgate is driven by a second signal;

(c) determining whether the output values of the X and Y axes is distorted; and

(d) providing a warning message upon a determination that at least one of the output values of the X and Y axes is distorted.

11. The method as recited in claim 10, further comprising:

normalizing the output values of the X and Y axes to values in a predetermined range by means of the formulae below;

$\mathrm{nX}=\frac{\left(X-X_{\mathrm{bias}}\right)}{X_{\mathrm{scale}}},X_{\mathrm{bias}}=\frac{\left(X_{\max }+X_{\min }\right)}{2},X_{\mathrm{scale}}=\frac{\left(X_{\max }-X_{\min }\right)}{2}$ $\mathrm{nY}=\frac{\left(Y-Y_{\mathrm{bias}}\right)}{Y_{\mathrm{scale}}},Y_{\mathrm{bias}}=\frac{\left(Y_{\max }+Y_{\min }\right)}{2},Y_{\mathrm{scale}}=\frac{\left(Y_{\max }-Y_{\min }\right)}{2}$

wherein X and Y indicate the output values of the X and Y axes, respectively, nX and nY indicate the normalization values of the X and Y axes, respectively, Xmax and Xmin indicate maximum and minimum values of the X axis, respectively, and Ymax and Ymin indicate maximum and minimum values of the Y axis, respectively.

12. The method as recited in claim 11, wherein the determining (c) includes:

squaring each of the normalized output values of the X and Y axes and then adding them together to detect a resultant value;

determining whether the resultant value is within a predetermined tolerable range; and

determining that at least one of the output values of the X and Y axes is distorted when the resultant value is out of the predetermined tolerable range.

13. The method as recited in claim 12, further comprising:

applying the normalized output values of the X and Y axes to the following formula to calculate an azimuth angle ψ

;

ψ

= tan<sup>−

1</sup>(Y/X)

wherein X and Y are normalized output values of the X and Y axes, respectively, and ψ

is an azimuth angle.

14. The method as recited in claim 10, wherein the X axis fluxgate is orthogonal to the Y axis fluxgate.

15. The method as recited in claim 10, wherein the warning signal is displayed upon the determination that at least one of the output values of the X and Y axes is distorted.

16. The method as recited in claim 10, wherein the first signal is inverted with respect to the second signal.

17. The method as recited in claim 10, wherein the first signal has an opposite phase with respect to the second signal.