| 摘要 |
PURPOSE:To execute navigation with high accuracy by operating a prescribed expression by using an output voltage of an earth magnetism sensor, discriminating it to be an azimuth error caused by magnetization of a car body, when said voltage exceeds a prescribed value, issuing an alarm, calculating a new offset by magnetization, and calculating an exact vehicle azimuth. CONSTITUTION:A magnetic field by magnetization of a vehicle is added vectorially to output voltages Vx, Vy of earth magnetism sensors placed orthogonal to each other on the vehicle. When the vehicle rotates by 360 deg., Vx and Vy draw a circular locus, and in the Vx and Vy coordinate system, the center of a circle exists at offsets vxn, vyn and a radius KB of the circle is proportional to the magnitude of the horizontal component of the earth magnetism B. Even if a vehicle azimuth is varied, if magnetization M is constant, the radius KB is constant. When the magnetization is varied, the offset moves, and a circle C also moves. In this state, from the circular locus after one rotation of the vehicle, the offsets vxn, vyn are calculated and (Vx-vxn)<2>+(Vy-vyn)<2> is calculated at a prescribed timing. When it exceeds the square of the radius of the circle C, an alarm is issued, and after they have been updated to new offsets vxn+1, vyn+1, an exact azimuth theta is calculated. According to this constitution, navigation can be executed with high accuracy.
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