| 摘要 |
PURPOSE:To prevent malfunction due to an acoustic noise positively, by dividing a detection area into several parts to detect reflected ultrasonic signals from an obstacle. CONSTITUTION:A wavelength determined by a frequency generation circuit 4 for transmission is transmitted to a transmitting/receiving vibrator 2 at a cycle determined by an oscillation cycle generation circuit 5 and an ultrasonic wave is oscillated into the air from the vibrator 2. The ultrasonic wave reflected from an obstacle 3 is received by the vibrator 2 again and a very weak current generated is shaped with a filter 7 and amplified with an amplifier 8 to be applied to a detection area decision circuit 9 as receiving signal. On the other hand, a reference gate generation circuit 10 generates a reference signal to be transmitted to a time gate generation circuit 11, which generates a time gate signal based on the reference signal to be sent to the circuit 9. The circuit 9 judges a signal received from the amplifier 8 to recognize a detection area M at which the obstacle is present. A signal is sent from the circuit 9, for example, to a wheel driving motor and an unmanned truck is decelerated or stopped on the basis of the judgement by the circuit 9.
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