| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain accurate information related to an obstacle in an ultrasonic sensor by discriminating abnormality of the own device. <P>SOLUTION: A wave-transmitting drive circuit drives an oscillator at a frequency f<SB POS="POST">1</SB>which is different from a resonance frequency of the oscillator (S11). As a result thereof, when a wave-receiving signal is inputted from a received wave amplifier circuit within a detection gate time (YES at S12) and only if the frequency of the wave-receiving signal is equal to the resonance frequency f<SB POS="POST">0</SB>(YES at S13), an ultrasonic sensor is determined to be abnormal (S14). In this case, if the wave-receiving signal having the resonance frequency f<SB POS="POST">0</SB>is inputted within the detection gate time when the oscillator is driven at the frequency f<SB POS="POST">1</SB>, the wave-receiving signal can be regarded as a reverberation signal. Further, the fact that the reverberation signal is inputted within the detection gate time indicates that abnormality has occurred in the ultrasonic sensor caused by a vibrating portion generated and parasitic on the oscillator. Accordingly, by performing processing such as S11-S14, it can be accurately determined whether the ultrasonic sensor is abnormal or not. <P>COPYRIGHT: (C)2013,JPO&INPIT |
