Drive circuit for an ultrasonic motor

Details Drive circuit for an ultrasonic motor Drive circuit for an ultrasonic motor

1993-10-13

1995-07-04

Budd, Mark O.

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

310323, H01L 4108

Patent

active

054303435

ABSTRACT:
An ultrasonic motor includes a piezoelectric element provided with drive electrodes and also with detector electrodes, an elastic body, and a rotor assembly. A drive circuit for this ultrasonic motor includes a high frequency signal generator, a phase shifter, amplifiers which supply high frequency AC voltage to the drive electrodes, and a CPU. The CPU measures the voltages from a pair of electrodes and calculates the difference of their mean square values, and similarly measures the voltages from the other pair of electrodes and calculates the difference of their mean square values. In this way, the CPU detects the presence of any standing wave component in the vibrations which are being excited in the elastic body by the piezoelectric element. The CPU varies the amplification ratios provided by the amplifiers according to the result of this standing wave detection process, and thereby alters the amplitudes of the voltages supplied to the drive electrodes. By repeatedly performing this calculation and adjustment process, the CPU can reduce the standing wave component effectively to zero, thus increasing the drive efficiency of the ultrasonic motor.

REFERENCES:
patent: 4658172 (1987-04-01), Izukawa
patent: 4692649 (1987-09-01), Izukawa et al.
patent: 4954742 (1990-09-01), Izukawa
patent: 5001404 (1991-03-01), Kataoka
patent: 5134333 (1992-07-01), Atsuta
patent: 5198714 (1993-03-01), Salomon et al.

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