| 摘要 |
PURPOSE:To provide an ultrasonic motor having an always stable operation and a high efficiency by accurately detecting a voltage of a fundamental frequency of effective drive for rotation of a moving body and controlling a moving speed of the body and a driving frequency of a vibrator. CONSTITUTION:An output signal of a voltage controlled oscillator 7 is split, two signals having a phase difference of 90 degrees are input to power amplifiers 9, 10, and applied to driving electrodes A, B. An output voltage waveform of a sensor electrode E is passed through a band-pass filter 12 to remove unnecessary high frequency components which do not contribute to movement of a moving body, and then converted to a DC signal by a rectifier 13. A set voltage Vs corresponding to the speed of the body to be an object is input to one input terminal of an error amplifier 14. The amplifier 14 outputs an error between a voltage corresponding to the speed of the body and a set voltage Vd. A frequency controller 15 so controls a driving frequency of a vibration according to the error signal that a DC output of the rectifier becomes equal to the voltage Vd. |
