Revolving speed control of ultrasonic motor based on feedback of piezoelectric sensor

At present, the feedback control of Ultrasonic Motor (USM) is mainly based on the direct feedback of USM’s revolving speed. With this method, the photoelectric encoding is essential. When we need to control the USM at low speed, the demand of the precision of the photo-electricity encoding is high, resulting in significant increase the cost of the control system. Hence this paper proposes the feedback based on the piezoelectric sensor to control the USM.