| 摘要 |
PROBLEM TO BE SOLVED: To prevent calibration of a geomagnetic sensor from being influenced by vibration or a surrounding external magnetic field for enabling correct azimuth detection by the geomagnetic sensor. SOLUTION: After a center value and a gain or a circular output trace of a geomagnetic sensor when an automobile is rotated once in a predetermined direction are obtained as temporary calibration values, the automobile is rotated at a constant speed (S5), an azimuth is calculated using the temporary calibration values from an X-coil output and a Y-coil output of the geomagnetic sensor (S6), and the automobile is stopped when it has been rotated once. Output data of X- and Y-coils sampled with one rotation is used to approximate respective X and Y outputs with a trigonometric function by the least square method, and the center value and the gain of the output trace are obtained as precise calibration values (S8). Thus in contrast to conventional calibration wherein the center value of the output trace is obtained from a limited number of data, azimuth detection accuracy by the geomagnetic sensor can be improved with more precise calibration while minimizing influence of vibration or an external magnetic field. |
