Research On Adaptive Position Control Of Ultrasonic Motor

As a new type of mechatronics product, ultrasonic motor has many advantages such as high torque, low speed, no electromagnetic interference and high standstill torque, etc. It meets many needs of modern automation equipment and has been widely concerned by people. Based on the research of speed control, appropriate adaptive control strategies are taken in this paper in order to overcome the disadvantages that caused by the inherent characteristics of ultrasonic motor such as starting difficulty, speed fluctuation and time-varying parameters to realize tracking control of the motor position.The model is usually the basis for the research of control strategies, and then the frequency-position model of ultrasonic is acquired by existing speed model. In this paper, the driving frequency is taken as the control variable to maintain better operational efficiency.Based on the above model, the pole assignment position controller is designed and the speed-limit method without speed closed-loop is given, and then the single close-loop position control system is realized. Both the simulation and experimental results show that the control strategy is effective, the controller structure is simplified, and the complexity is reduced at the same time.Further more, in order to meet the requirements of higher control performance and enhance the system’s robustness, four kinds of double closed-loop control strategies are designed: pole assignment speed controller and PID position controller, PID speed controller and pole assignment position controller, pole assignment speed controller and pole assignment position controller, PID position controller and model reference adaptive speed controller. Simulation results show that all the four control strategies can realize effective position servo control, the response time is significantly reduced and the anti-jamming ability is enhanced. Compared with the single closed-loop position control system, the position and speed dual closed-loop control system has better location accuracy.