QUICK AND PRECISE POSITION CONTROL OF AN ULTRASONIC MOTOR WITH DUAL-MODE CONTROL

An ultrasonic motor (USM) is a new type motor that has an excellent pe rformance and many useful features that electromagnetic motors do not have. It is therefore expected to be of practical use for small motor applications. Phase difference control of applied voltages seems to be most suited for position control of this motor. However, it is diffic ult to carry out the quick and precise position control when driving f requency is constant. In this paper, to achieve the quick and precise position control, both driving frequency and the phase difference of t he applied voltages are controlled. The effectiveness of the proposed control scheme is demonstrated by experiments.