| 摘要 |
PURPOSE:To accurately correct offset while providing a small margin by setting the extinction of the output of a car speed sensor and the lowering of the output of a revolving speed sensor as the judging standard of stoppage. CONSTITUTION:In the case of the threshold value of a gyroscope 43 or less, the presence of a wheel speed sensor 41 is judged. When there is no output pulse of the sensor 41, the possibility of stoppage is judged to be present to wait the elapse of a margin Ta of a definite time. After the elapse of the margin Ta, the output data theta of the gyroscope 43 is stored in the FIFO memory built in a locator 1 and an overflow value is accumulated in a buffer memory 20 as a value S and the number C of times of data acquisition is added. Herein, the cumulated value S shows the azimuth error during stoppage and, at the point of time when the obtaining number of times reaches a predetermined value, offset is renewed on the basis of an S/C value. By this method, offset can be corrected while providing a small calculated margin of an offset value by accurately judging the stoppage of the vehicle. |
