Driving circuit for ultrasonic motor servo drive with variable-structure adaptive model-following control

A novel driving circuit is proposed to provide two-phase balance voltage for the travelling-wave type ultrasonic motor (USM). Moreover, the variable-structure adaptive modelfollowing control is applied for the position control of the USM. First, the single-phase equivalent model of the USM is described. Next, the novel driving circuit, which is a two-phase chopper-inverter combination, is designed. Since the lumped dynamic model of the USM is difficult to obtain and the motor parameters are time varying, the variable-structure adaptive model-following control is applied to design the position controller of the USM to reduce the influence of parameter variations and external disturbances. The effectiveness of the proposed controller is demonstrated by experimental results.