| 摘要 |
An ultrasonic motor driver includes a voltage-current phase difference detector for detecting a phase difference between an applied voltage and a current of a torsional vibration piezoelectric element and a phase shifter for adjusting phases of voltages applied to the longitudinal and torsional vibration piezoelectric elements so that the phase difference is minimum. Even if changes in application environment, e.g., an external force or temperature, occur, a rotational speed can be kept stable to drive an ultrasonic motor.
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