Position control of linear ultrasonic motor

Abstract

This thesis focuses on the position control of linear ultrasonic motor. The deazonepresent in the motor characteristics is compensated using a feedforwardcontrol signal. Linear PI controller has good performance for set-point positiontracking. However, its performance deteriorates for tracking time varyingtrajectories and under load variations. A robust sliding mode position controller(SMC) is proposed to overcome the problems of PI controller. It hasgood position tracking performance for set-point positioning, time varying trajectoriesand under load variations. However, conventional SMC su ers fromthe problem of chattering. A scheme with two low pass filters are introducedto the conventional SMC to facilitate the acquisition of equivalent control anddwindle chattering. For periodic time varying position tracking, the performanceof SMC is improved by supplementing it with a plug-in iterative learningcontroller. Such a hybrid control scheme ensures good tracking performanceonly for strictly repetitive tasks. Alternatively, for non-repetitive positioningapplications direct learning scheme is proposed and implemented. The iterativeand direct learning controllers are used in coordination to achieve good trackingperformance for repetitive and non-repetitive positioning applications. E cacyof the proposed control schemes are substantiated by extensive experimentalvalidations.