| 摘要 |
A system for automatically controlling the position of a tractor-trailer rearview mirror to maintain unobstructed vision in the mirror during turns employs a pair of ultrasonic transducers mounted on the external rear wall of the tractor on opposite sides of the centerline thereof so as to project ultrasonic sound beams onto the forward wall of the trailer. A control circuit determines the difference in the two path lengths, indicating the degree of turning of the vehicle, to generate control signals to a mirror rotating motor. A third transducer may be mounted for rotation with the mirror and directs an ultrasonic beam along the zone immediately beside the trailer for detecting persons or objects within the zone and actuating an alarm in the event of such detection.
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