| 摘要 |
PROBLEM TO BE SOLVED: To provide an obstruction detecting device capable of correcting changes in the sound velocity of ultrasonic waves due to changes in ambient temperature and highly accurately detecting the location of an obstruction. SOLUTION: The obstruction detecting device is provided with an ultrasonic sensor Sa with both an ultrasonic transmitting means 1 (first ultrasonic sensor) and an ultrasonic receiving means 3 (third ultrasonic sensor) for receiving the reflected waves of ultrasonic waves, and an ultrasonic sensor Sb with an ultrasonic receiving means 2 (second ultrasonic sensor) arranged at a sensor-to-sensor distance (d) from the ultrasonic sensor Sa. In the ultrasonic sensor Sb, a direct wave reception time td and a reflected wave reception time tb are detected to compute the sound velocity value (c) of ultrasonic waves from the sensor-to- sensor distance (d) and the direct wave reception time td, to compute the distance to the obstruction P from the obtained sound velocity value (c) and the reflected wave reception time tb, and to compute the direction of the obstruction P from the time difference between the reflected wave reception times ta and tb of the ultrasonic sensors Sa and Sb, the comparison result of delay velocities, and the direct wave reception time td.
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