Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1991-07-02
1993-05-25
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310323, 318116, H01L 4108
Patent
active
052143392
ABSTRACT:
A device and method are provided for driving an ultrasonic motor. The motor's initial start drive frequency is set higher than the resonant frequency of the motor and an initial target drive frequency is set lower than the resonant frequency. A drive signal is then applied to a piezoelectric element on the stator in order to rotate the rotor. The frequency of the drive signals is then swept from the start frequency to the target frequency. Abnormal vibrations of the rotor that occur during sweeping of the drive frequency are detected by a monitor electrode mounted on the stator. Upon the detection of an abnormal vibration, the target frequency is reset to equal the drive frequency at which the abnormal vibration was detected. The drive frequency is then reset to a reset start frequency that is higher than the reset target frequency. Thereafter, the drive frequency sweeping step is repeated. This provides a high output from the motor without generating noise.
REFERENCES:
patent: 3889166 (1975-06-01), Scurlock
patent: 4275363 (1981-06-01), Mishiro et al.
patent: 4727276 (1988-02-01), Izukawa et al.
patent: 4853579 (1989-08-01), Kawasaki et al.
patent: 4914337 (1990-04-01), Takagi
patent: 5061882 (1991-10-01), Takagi
Asmo Co. Ltd.
Budd Mark O.
Dougherty Thomas M.
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