Research On Driving Modeling And Fuzzy PID Control Of Traveling Wave Ultrasonic Motors

Traveling wave ultrasonic motors(TWUSM)are of the characteristics of high torque at low speed,no electromagnetic interference,high accuracy and fast response,and have attracted wide attention.But the difficulty of high performance control in non-linearity and parameters time-varying affects its application in aerospace.Based on the analysis of the mechanism of ultrasonic motor operation,this paper sets up of driving circuit model by traveling wave ultrasonic motor,and designs the system of fuzzy PID control based on ultrasonic motor speed/position in phase difference,in order to improve the performance of ultrasonic motor.The main contents include:(1)The running mechanisms of TWUSM are analyzed,which include the generation of surface wave and the form of elliptical stator surface particle vibration.The mechanisms show there exist three kinds of speed regulation methods for TWUSM,such as frequency,phase difference and amplitude.Then the characteristics of these methods are analyzed.Based on the system equations of free vibrations for piezoelectric vibrator,the two-phase equivalent circuit model of the ultrasonic motor is built using equivalent circuit method.These will provide theoretical support for the establishment of driving circuit model and the choice of driving modes.(2)The two-phase driving circuit model of ultrasonic motor is proposed and driving characteristics of ultrasonic motor based on model are analyzed.The series matching method and the LLCC matching method are applied to the established model of ultrasonic motor driving circuit,the design method of ultrasonic motor matching inductance based on empirical formula and simulation analysis is proposed.A simulation model of single-phase and two-phase driving circuit for ultrasonic motor is established.The simulation results show that the LLCC matching method can effectively solve the problem of voltage amplitude inconsistency and achieve better matching.Based on the simulation model,the driving characteristics of ultrasonic motor are analyzed.The hardware design scheme of ultrasonic motor driving circuit based on TMS320F2812 DSP is proposed.The experiment results show that output waveform of driving circuit is good,the signal is stable,and the interference of the clutter is few.(3)Since it is difficult to establish accurate mathematical model of ultrasonic motor,single control strategy can not meet the high performance requirements.The design scheme of fuzzy self-tuning PID control system of ultrasonic motor is proposed.The speed/position fuzzy self-tuning PID control model of ultrasonic motor based on the voltage phase difference is constructed.A method of changing the phase difference of two-phase voltage signal of ultrasonic motor is proposed.The fuzzy self-tuning PID control simulation model of ultrasonic motor is established.The simulation results show that compared with the conventional PID controller,the adjustment time of the fuzzy self-tuning PID control is shorter by 0.002 s,the overshoot is reduced by 23%,and the anti-interference ability is better than the traditional PID controller;fuzzy self-tuning PID position control step response is fast,the transient is smooth,and the target value can be well tracked.