Position Control of Ultrasonic Motor Based on Loop - Gain Adjustment by Adaptive Algorithm

In the ultrasonic motors (USM), there are various driving principles such as a standing wave type, a traveling wave type, etc. Among them, the traveling wave type USM is applied in different devices at various situations, because its shape is like DC (direct current) motors. The control performance is reduction because of the dynamic characteristics of USM, which are greatly fluctuate, depending on the influence of nonlinearity via the friction, frictional heat caused by the driving principle, the magnitude of the load and driving conditions. Up to now, various control methods are proposed, and a lot of researches are conducted to control precision positioning, but a simple method to realize the high positioning performance is not proposed yet. In this research, it is offered a two-degrees-of-freedom control method. It introduces a simple adaptive algorithm which holds the loop gain as a constant value, assuming the steady-state gain is decreased as the reduction of the rotational speed of USM. The characteristic of this method is that the control performance can be compensated with only one gain adjustment. Its effectiveness is verified by experiment which uses USM. キーワード：超音波モータ，