LAUSR

The operation of ultrasonic motor is characterized by obvious nonlinearity. Appropriate motor control strategy is an important prerequisite for promoting the wider application of ultrasonic motors. PID controller is widely used in motor motion control products. Due to the nonlinearity of the ultrasonic motor, the PID control parameter values that can achieve good performance are very different at different speeds. In this paper, aiming at the application requirements of ultrasonic motor speed control, a fuzzy controller with simple structure is proposed to realize nonlinear variable-parameter PID control by using nonlinear input–output mapping ability of fuzzy logic. The proposed fuzzy controller has only one input variable with three linguistic values. In order to match the nonlinear operating characteristics of the ultrasonic motor and improve the control precision, the fuzzy rule is designed as the Takagi–Sugeno form. Takagi–Sugeno defuzzification method is adopted. The calculation formula of control quantity given by the fuzzy controller is similar to that of the PI controller, but the control parameters are nonlinearly changed. Compared with the traditional fuzzy controller, the structure of the proposed controller is simple and the amount of online computations is greatly reduced. Experimental results under various operating conditions show that the proposed controller has good control effect and it has robustness to disturbances such as drive voltage amplitude and load torque variation.