Study On Driving And Control Of Coaxial Parallel Traveling Wave Ultrasonic Motor

Ultrasonic motor is a type of direct drive micro motor,with low speed large torque,no electromagnetic interference,fast response and other advantages.However its output torque is small because it achieves the driving force through fraction of the surface contact between the stator and the rotor.The ultrasonic motor has limitations in large torque and high power applications.This paper presents a new type of coaxial parallel traveling wave ultrasonic motor and improves the output torque of the motor by means of multi-stator parallel connection.First,the parallel structure of the ultrasonic motor is designed and then a coaxial parallel traveling wave ultrasonic motor is assembled.Based on the analysis of surface contact between the stator and the rotor of a single ultrasonic motor,the contact surface model of the multi-stator parallel motor is established.The torque and speed characteristics of the coaxial parallel traveling wave ultrasonic motor are obtained by simulation experiment.The push-pull type of inverter circuit is selected as the drive circuit of this motor and the circuit topology and sequence in time are analyzed.By designing transformers?selecting drive power?switching devices and its drive chip,it is successful to build a drive platform for this coaxial parallel traveling wave ultrasonic motor.At last,this paper uses identification method to build the second order transfer function model of this ultrasonic motor.The PID control theory is applied to the speed control of the motor.Aiming at the shortcomings of PID control,an optimization method is proposed to arrange the transition process.Simulation and experiment show that arranging process of transition in the PID controller can reduce the system overshoot and improve the motor's starting characteristics.