| 摘要 |
PURPOSE:To allow driving of an ultrasonic motor under desired driving state by substantially equaling the input current value to a piezoelectric to a target current value and driving the ultrasonic motor in desired oscillation mode. CONSTITUTION:Upon receiving signals (a), (b) having phase difference of pi/2 from an oscillator 3, sine wave generators 4a, 4b deliver sine wave signals (c), (d) to the input terminals of amplifiers 50a, 50b. The amplifier 50a delivers an AC signal (h) corresponding to the amplification factor signal (e) to an electrode 2a whereas the amplifier 50b delivers an AC signal (i) corresponding to an amplification factor signal (t) to an electrode 2b. A current value comparing circuit 9a compares the amplification factor signal (e) with a current reference value (g), i.e., the value of AC signal (h) flowing into the electrode 2a, and increases or decreases the amplification factor signal (e). A current value comparing circuit 9b functions similarly. Consequently, the value of current flowing into the electrode 2a, 2b is controlled to be equal to the current reference value (q) and the ultrasonic motor is driven under a desired driving state. |
