Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1994-02-28
1996-04-16
Dougherty, Thomas M.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
H02N 200
Patent
active
055085792
ABSTRACT:
An ultrasonic motor driving device comprises: a detecting unit for detecting a phase difference between a high-frequency drive voltage waveform applied to a drive electrode of an ultrasonic motor and a voltage waveform outputted by a monitor electrode generating frequency voltage in accordance with the vibrations of an elastic member of the ultrasonic motor; a setting unit for setting a reference phase difference in accordance with a drive frequency within a normally used range including a frequency which provides the greatest drive force for the ultrasonic motor; a control unit which performs control such that the phase difference becomes equal to the reference phase difference; a frequency signal generating unit which generates a signal having a frequency in accordance with an output of the control unit and which applies the signal to the ultrasonic motor; and a lower and/or upper limit frequency control unit for controlling the frequency signal generating unit so that when the drive frequency is lower and/or higher than the normally used range, the drive frequency will be maintained higher and/or lower than a frequency which provides a phase difference equal to the reference phase difference, respectively.
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Dougherty Thomas M.
Nikon Corporation
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