Nonlinear Adaptive Control of Ultrasonic Motors Considering Dead-Zone

When applying a load torque to an ultrasonic motor, a dead-zone occurs in the control input. A nonlinear adaptive control, which considers dead-zones, is consequently proposed for the motor. To implement the proposed control strategy, a microcomputer and an embedded system are employed. The state quantities, such as acceleration, speed, and position, are required to apply digital implementation. However, a rotary encoder, which is used to get feedback, causes quantization errors in the speed information. To overcome these problems, a variable structure system observer with the possibility of decreasing quantization error is also presented. In other words, a small, low-cost, and fast responsive microcomputer-based nonlinear adaptive controller is designed and assembled. Effectiveness and reliability of the proposed method is experimentally verified.