Rotary speed control of ultrasonic motor with nonlinear estimator

In this paper, a nonlinear estimator is developed to estimate the effect of friction on the performance of an ultrasonic motor (USM). Based on the friction model of USM, a friction estimator based compensator is developed for eliminating the effect of friction existing in between the surfaces of stator and rotor of the USM. Then, a proportional plus integral (PI) control strategy with friction estimator is proposed to control rotary speed of USM. Finally, the experimental results are presented for strategy evaluation.