| 摘要 |
PURPOSE:To simplify constitution, and to reduce cost by detecting the magnitude of load working to a moving body from the fluctuation of the applied voltage of an electrostrictive element. CONSTITUTION:An ultrasonic motor 10 is constituted by pushing an annular elastic body and a moving body by predetermined push force, and segment electrodes 14a-14d are formed to an electrostrictive element 13 for the motor. A drive circuit for the motor 10 is organized of an oscillator 1, a 90 deg. phase- shifting circuit 2 for an output from the oscillator 1 and amplifiers 3, 4, and supplies said each segment electrode 14b, 14d with power and drives said motor 10. A detector 5 detecting an output from the amplifier 4, an AND gate 6 and a timer 7 are set up as a load detector, and a low level signal is transmitted over the AND gate 6 for a fixed time after a motor starting command is output from a motor starting-command output device 8 by the timer 7. Accordingly, when load is increased, voltage amplitude applied to the electrostrictive element 13 varies, and the variation of voltage amplitude is detected and the increase of load is detected. |
