Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1989-09-21
1991-06-04
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
H01L 4108
Patent
active
050217003
ABSTRACT:
A driving apparatus for an ultrasonic motor which generates a driving force by using a piezoelectric member, wherein an oscillation frequency fd is varied so as to follow a driving frequency fm which is particular to a mechanical resonance frequency fro when the mechanical resonance frequency fro varies by influence of environment. For this purpose, current and voltage detectors are provided for respectively detecting the current corresponding to the mechanical vibration of the piezoelectric member and the voltage impressed on the piezoelectric member. The phase difference between the detected current and voltage is detected, and this phase difference is used to drive a variable frequency oscillator so as to maintain the phase difference constant. The output of the variable frequency oscillator is then used to drive the driving circuit for the piezoelectric member of the ultrasonic motor.
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Study of the 70th regular meeting of the power electronics; "Ultrasonic Motor"; published 1986; Matsushita Electric Industrial Co., Ltd., Electric Motor Division.
Harao Noriyuki
Takahashi Ken-ichiroh
Tanoue Hiromi
Budd Mark O.
Matsushita Electric - Industrial Co., Ltd.
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