CONTROL METHOD FOR TRAVELING WAVE TYPE ULTRASONIC MOTOR

摘要

PURPOSE:To drive a motor stably with constant efficiency by detecting the shifting direction of resonance frequency based on the driving current level of the motor then shifting the driving frequency. CONSTITUTION:Controller for a ultrasonic motor 1 comprises a voltage control type oscillator 6, a ring counter 8, a switching circuit 9 and a transformer 10. Furthermore, a resistor 2 for detecting the driving current level of the motor 1 and an operational amplifier 4 which produces a voltage for controlling the resonance frequency of the oscillator 6 are provided. When the frequency of high frequency voltage to be applied onto a piezoelectric element is shifted based on the detected shifting direction of resonance frequency, driving current level can be maintained constant.