| 摘要 |
PURPOSE:To stabilize operation by controlling driving frequency so that the phase difference of the driving voltage of a vibrator and inflow currents is brought to first set phase difference. CONSTITUTION:A driver circuit for an ultrasonic motor has a voltage controlled oscillator 7 oscillating in accordance with control voltage from an adder 8, a 90 deg. phase shifter 9 and power amplifiers 10-11, and respectively applies outputs from the power amplifiers to a piezoelectric body 2, thus driving a vibrator. A control circuit for the voltage and currents of the piezoelectric body 2 is composed of voltage and current detectors 12-13, a phase difference detector 14, phase comparators 15-16, a controller 17 and a switch 18. Consequently, output voltage from the adder 8 is input to a control terminal C1 for the voltage controlled oscillator 7, and driving frequency is converted so as to reduce the difference of a set value P1 and phase difference on drive. When the phase difference of driving voltage and inflow currents exceeds a second set value P2, the amplitude value of driving voltage or driving pulse width is increased, and progressive waves having an amplitude value sufficient for driving the moving body is excited in the piezoelectric body 2. |
