Magnetic transient detection and calibration technique for an auto- calibrating compass

摘要

A magnetic transient detection technique which alerts a microcomputer of an auto-calibrating compass when electrical transients which produce magnetic transients have occurred. The technique employs an electronic compass control circuit having a sampling rate high enough to isolate electrical transients from transients produced by normal motion of the vehicle. Accelerations in data values defined as the difference between two changes in the coordinates for the center of the earth's magnetic field circle, are calculated and compared to predetermined threshold accelerations. Previous acceleration values and their associated vehicle magnetic field vectors can be stored in the microcomputer. After a magnetic transient is detected, its associated vehicle magnetic field vector is subtracted from the resultant magnetic field to yield vehicle heading. Once detected, magnetic transients are also used to initiate auto-calibration.