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 fo r the USM have been reported in recent years; however, these models ar e very complex to apply for speed control of the USM. Therefore, the s peed controllers have been designed using PI controllers or fuzzy cont rollers and it is necessary to develop a simple and convenient mathema tical model for the USM in order to achieve a high-performance speed c ontrol, In this paper, a mathematical model for the USM is proposed wh ich is simple and useful for speed control, The speed controller is de signed based on the model using adaptive control theory, Adaptive cont rol is attractive for control of the USM because the speed characteris tics of the USM vary with drive conditions. The application of this co ntrol scheme to speed control for the USM is attempted first, The effe ctiveness of proposed control is demonstrated by experiments.