SPEED CONTROL OF ULTRASONIC MOTORS USING NEURAL-NETWORK

Ultrasonic motor (USM) is a newly developed motor, and it has excellen t performance and many useful features, therefore, it has been expecte d to be of practical use. However, the driving principle of USM is dif ferent from that of other electromagnetic-type motors, and the mathema tical model is complex to apply to motor control. Furthermore, the spe ed characteristics of the motor have heavy nonlinearity and vary with driving conditions. Hence, the precise speed control of USM is general ly difficult, This paper proposes a new speed-control scheme for USM u sing a neural network. The proposed controller can approximate the non linear input-output mappings of the motor using a neural network and c an compensate the characteristic variations by on-line learning using the error backpropagation algorithm. Then, the trained network finally makes an inverse model of the motor. The usefulness and validity of t he proposed control scheme are examined in experiments.