Study Of Travelling-wave Rotary Ultrasonic Motor Electric-Mechanical-Kinetic Mixed Model

Ultrasonic motor(USM)is a new type of micro motors.Compared with the traditional electromagnetic motors,USM has many advantages,such as compactness in size,high torque with low speed,anti-electromagnetic interference,etc.And USM is widely used in industrial application.In this paper,a representative USM,Travelling-wave Rotary Ultrasonic Motor(TRUM)is studied,including analyzing operating mechanism,modelling,and driving system,etc.The main contents are summarized as follows:Firstly,the operating mechanism of TRUM is analyzed based on its structure and working principle.According to the electromechanical transduction relationship,operating mechanism is divided into two energy conversions which are “electric energy-vibration mechanical energy” and “vibration mechanical energy-kinetic energy”.And these conversions make the theoretical foundation for TRUM modeling.Secondly,a mixed modeling method is proposed.The electrical equivalent circuit model of stator is built based on the first energy conversion.And the contact model between stator and rotor is set up according to the second energy conversion.These two models are combined into a mixed model by current through piezoelectric ceramic and interface modal force.The electrical characteristics,interface contact properties and mechanical characteristics of the mixed model are simulated.Finally,in order to verify the correctness of the proposed model,the driving controller based on full-bridge is built with DSP and CPLD,which act as the control core.The controller consisting of H-bridge driving circuit,high frequency power pulse transformer and match circuit is further discussed.The method of counting and comparison in half cycle is innovatively presented,which can realize frequency modulation(FM),amplitude modulation(AM),phase modulation(PM)control of phaseshift PWM.The accuracy of the proposed model is verified by experiments.