| 摘要 |
PURPOSE:To prevent an ultrasonic motor from deteriorating or being damaged due to overload. CONSTITUTION:The output signal level of a piezoelectric sensor 2c provided at the stator of an ultrasonic motor is detected by a level detector 16, the detection level L is compared with a reference value Lr, and the comparison result is outputted to a drive regulation part 19. When a drive signal is supplied to the ultrasonic motor 1 and then if the ultrasonic motor 1 is overloaded and a movable element 3 is forced to a stop, an advance wave generated at the stator is suppressed and the level L becomes smaller than the reference value L4. A drive regulation part 19 detects the increase in the level and turns off a switch 13 and stops the supply of a drive signal, thus preventing the ultrasonic motor 1 from deteriorating and being damaged due to overload. |
