Patent ID: 6570294
Filing Date: 2003-05-27
Classification: H02N

Abstract:
An ultrasonic motor comprising: a control circuit to which a processed input signal is supplied for controlling at least one of a direction and speed of the motor in accordance with the processed input signal; a drive circuit for receiving a control signal output by the control circuit and outputting a drive signal in accordance therewith; a vibrating body having a piezoelectric element to which the drive signal output by the drive circuit is supplied so that vibration of the vibrating body is controlled in accordance with the control signal; a moving body driven in response to vibration of the vibrating body; a position detecting circuit for producing an output signal in accordance with a position of the moving body; and a signal processing circuit for receiving an input signal, processing the input signal by one of eliminating a frequency component thereof above a predetermined frequency level, eliminating fluctuations in level of the input signal below a predetermined value, and sampling the input signal to output a mean value thereof, and outputting the processed input signal to the control circuit so that minor fluctuations in the input signal are eliminated by the signal processing circuit and do not affect operation of the motor; wherein the control circuit includes means for comparing the processed input signal with the output signal of the position detecting circuit and producing the control signal in accordance with a difference therebetween.