| 摘要 |
PROBLEM TO BE SOLVED: To prevent an erroneous recognition that as if an obstruction exists in a short distance, caused by interference between a plurality of ultrasonic sensors for detecting a circumference. SOLUTION: A plurality of ultrasonic sensors for transmission and ultrasonic sensors for reception are arranged on the outer periphery of a traveling car main body. When a sensor for transmission is elected, a sensor for reception is selected which corresponds to the selected sensor for transmission. The selected sensor for reception is made possible to receive an ultrasonic wave, after a time t1 has passed which is necessary for it that the ultrasonic wave travels between the selected sensor for transmission and the selected sensor for reception. COPYRIGHT: (C)2004,JPO
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