Abstract
The ultrasonic motor is a new type motor which is driven by ultrasonic vibration force of piezoelectric elements unlike other electromagnetic motors, and has many excellent performance and features. The ultrasonic motor, however, has speed ripple which arises from inherent natures caused by its driving principle and structure. Since this speed ripple is larger than that of other small motors, it is a significant problem in view of precise speed control.We paid our attention to the periodicity of speed ripple and reduced the speed ripple of ultrasonic motor by using repetitive controller with the fixed learning factor. However, it is difficult to reduce the speed ripple quickly and to carry out the precise speed control when the kearning factor is fixed. In this paper, we present a speed ripple reduction method to achieve the precise speed control by adjusting the learning factor using fuzzy reasoning. it is able to reduce the speed ripple to one tenth comparing with that without speed control.
