Adjustable speed control of ultrasonic motors by adaptive control

The driving principle of the ultrasonic motor (USM) is different from those of the electro-magnetic type motors. Some mathematical models for the USM have been reported; however, these models are very complex to apply for speed control of the USM. Therefore, the speed controllers have been designed using PI controllers or fuzzy controllers and it is necessary to develop a simple and convenient mathematical model for the USM in order to achieve a high-performance speed control. In this paper, a mathematical model for the USM is proposed which is simple and useful for speed control. The speed controller is designed based on the model using adaptive control theory. Adaptive control is attractive for control of the USM because the speed characteristics of the USM vary with drive conditions. The application of this control scheme to speed control for the USM is attempted first. The effectiveness of proposed control is demonstrated by experimental