Velocity and Torque Control of Traveling-Wave-Type Ultrasonic Motors Using Sliding Mode Control.

Abstract

The traveling-wave-type ultrasonic motor (USM) provides unique utilities; compact size, light weight, and high torque at low speed, which evoke its applicability to an actuator of the light weight and compact size robot mechanisms. However, USM pertains a few of problems resulting from driving mechanisms with frictional forces; non-linearity and uncertain characteristics dependent on temperature, which makes it difficult to construct linear control systems. This paper presents a stable control of USM by using sliding mode control, which yields favorable features; controlability of non-linear system and robust stability against uncertainty of system model. A new model besed on the experiment data is exploited for designing torque/velocity servo control system. Though the model contains the uncertainty, the robust stability introduced by the sliding mode control makes the controller compensate the error between the model and the real system of USM. The experiment proves the effectiveness of the sliding mode servo controller.