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US 5,475,288 AGranted
Drive circuit for an ultrasonic motor having noise cancellation metals and method for using same
AssigneeAsmo Co., Ltd.
InventorHiroyuki Furukoshi
Life of this patent
Estimating the term…
Abstract
A drive circuit for driving an ultrasonic motor which maintains frequencies of drive signals for the ultrasonic motor within a drive frequency band. Generation of audible sound is thereby prevented. Further, it is possible to drive an ultrasonic motor in which irregularity of a waveform of a detection signal does not occur in an audible sound generating band.
Claims15
A drive circuit for an ultrasonic motor comprising:
- a drive signal outputting device for outputting ultrasonic motor drive signals of predetermined frequencies;
- a detector for detecting vibration of a stator of said ultrasonic motor and for outputting a continuous waveform whose amplitude value corresponds to said vibration;
- a comparator for comparing said continuous waveform and a predetermined level set in advance, and for determining portions of said continuous waveform which exceed said predetermined level and portions of said continuous waveform which do not exceed said predetermined level;
- and
- a frequency controller for bringing frequencies of said drive signals into a drive frequency band by raising said frequencies of said drive signals only in a period in which said continuous waveform exceeds said predetermined level at portions of said continuous waveform which exceed said predetermined level, and by lowering said frequencies of said drive signals only in a period in which said continuous waveform does not exceed said predetermined level at portions of said contiuous waveform wich do not exceed said predetermined level.
2 more elements
A method of driving and controlling an ultrasonic motor comprising the steps of:
- outputting ultrasonic motor drive signals of predetermined frequencies;
- detecting vibration of a stator of said ultrasonic motor and outputting a continuous waveform whose amplitude value corresponds to said vibration;
- comparing said continuous waveform and a predetermined level set in advance, and determining portions of said continuous waveform which exceed said predetermined level and portions of said continous waveform which do not exceed said predetermined level;
- and
- bringing frequencies of said drive signals into a drive frequency band by raising said frequencies of said drive signals only in a period in which said continous waveform exceeds said predetermined level at the portions of said continuous waveform which exceed said predetermined level, and by lowering said frequencies of said drive signals only in a period in which said continuous waveform does not exceed said predetermined level at portions of said continuous waveform which do not exceed said predetermined level.
2 more elements
Dependencies are inferred from the claim text.