Magnetic compass

• US 7,278,219 B2
• Filed: 06/02/2006
• Issued: 10/09/2007
• Est. Priority Date: 10/19/2005
• Status: Expired due to Fees

• Current Assignee: Aichi Micro Intelligent Corporation
• Original Assignee: Aichi Micro Intelligent Corporation
• Inventors: Kako, Eiji, Honkura, Yoshinobu, Aoyama, Hitoshi, Tsuchida, Katsuhiko
• Primary Examiner(s): GUADALUPE, YARITZA
• Application Number:
  US11/421,900
• Publication Number:
  US 20070084070A1
• Time in Patent Office: 494 Days
• Field of Search: 333/55.R, 333/56, 333/55.D
• 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 magnetic compass includes: a three-axis magnetic sensor for detecting geomagnetic vector as geomagnetic components in directions of three orthogonal axes x, y, and z; a data-plane calculating unit for calculating a data plane on which output data of the three-axis magnetic sensor are present in a sensor coordinate system of the three axes x, y, and z; a unit vector calculating unit for calculating unit vectors of a horizontal coordinate system of three orthogonal axes X, Y, and Z whose Z-axis runs vertically and X-Y plane defines a horizontal plane relative to the earth; a horizontal coordinate system conversion unit for converting geomagnetic components in the sensor coordinate system detected by the three-axis magnetic sensor into geomagnetic components in the horizontal coordinate system; an azimuth calculating unit for calculating azimuth based on the converted geomagnetic components in the horizontal coordinate system; and a display unit for displaying the calculated azimuth.

Claims

1. A magnetic compass comprising:

a three-axis magnetic sensor for detecting geomagnetic vector as geomagnetic components of three orthogonal axes x, y, and z;

data-plane calculating means for calculating a data plane on which output data of the three-axis magnetic sensor are present in a sensor coordinate system of the three axes x, y, and z by using geomagnetic vector data respectively detected by the three-axis magnetic sensor when the three-axis magnetic sensor changes its orientation to at least three different arbitrary directions within a horizontal plane;

unit vector calculating means for calculating unit vectors of a horizontal coordinate system of three orthogonal axes X, Y, and Z whose Z-axis defines a vertical direction and whose X-Y plane defines a horizontal plane relative to the earth;

horizontal coordinate system conversion means for converting the geomagnetic components in the sensor coordinate system detected by the three-axis magnetic sensor into geomagnetic components in the horizontal coordinate system;

azimuth calculating means for calculating an azimuth on the basis of the converted geomagnetic components in the horizontal coordinate system; and

display means for displaying the calculated azimuth.

2. The magnetic compass according to claim 1, wherein the unit vector calculating means includes:

Z-axis unit vector calculating means for calculating the unit vector along the horizontal coordinate system'"'"'s Z-axis expressed in the sensor coordinate system;

Y-axis unit vector calculating means for calculating the unit vector along the horizontal coordinate system'"'"'s Y-axis expressed in the sensor coordinate system on the basis of the calculated Z-axis unit vector; and

X-axis unit vector calculating means for calculating the unit vector along the horizontal coordinate system'"'"'s X-axis expressed in the sensor coordinate system on the basis of the calculated Y-axis unit vector and the calculated Z-axis unit vector.

3. The magnetic compass according to claim 1, wherein the three-axis magnetic sensor is arranged in a rear-view interior mirror of a vehicle.

4. The magnetic compass according to claim 1, wherein the three-axis magnetic sensor includes a magneto-impedance sensor element.