Precise position control of the ultrasonic motor using the speed compensation type NN controller

We propose the speed compensation type Neural Network (NN) controller for position control of Ultrasonic Motor (USM). The USM has dead-zone which rotor doesn't rotate or rotates very low speed when control input is small. It is because the USM uses frictional drive as driving principle. The fixed gain type PID controller cannot carry out precise position control by influence of dead-zone. This proposed control method uses the NN controller such that relation between control error and rotation speed become linear. To realize this relationship, we introduce the weighting factor so that control error correspons to rotation speed. If the wieghting factor is chosen appropriate value, this controller realizes very small overshoot and precise position control. The effectiveness of proposed design method is confirmed by experiments using the existent USM.