Design Of Linear Ultrasonic Motors Using In-plane Modes And Research Of The Driving Method

For the demand of rapidly developments of micro-lithography,precision machining,biotechnology and other areas,a higher performance index should be satisfied for the positioning platform.The traditional positioning platform is constructed of rotating motor,ball screw and oil film sliding mechanism.The stroke movement and the micro-nano-accuracy of the positioning platform are restricted by the following factors: short stroke,lags in response,the existence of screw space and many other shortcomings.The use of the ultrasonic motor could improve the accuracy of positioning and inhibit the positioning noise,assuring long stroke and high-precision positioning performance index.In this paper,the positioning platform of linear ultrasonic motor drive and air bearing slider guiding is designed to reach positioning accuracy and low positioning noise.To conclude,main results of this paper are as follows:First of all,completed the ultrasonic motor structure design and simulation.The structure and dimensions of ultrasonic motor are designed basing on the principle of in-plane longitudinal bending mode.Using ANSYS finite element analysis software to obtain the modal and the motion curve of elliptical trajectory which verify the rationality of the structure.Optimizing the motor size parameters to ensure the frequency consistency of longitudinal bending mode.Secondly,the motor equivalent circuit model is established.Series matching method was chosen to improve the efficiency of the motor and filter out the highorder harmonic signal,smooth signal waveform.In order to solve the problem of resonant frequency drift during the operation of ultrasonic motor,this paper adopt ed the frequency automatic tracking method with phase difference as the feedback to avoid the phenomenon of detuning during the operational progress of motor.Finally,tested the driver and the experimental platform.The electrical parameters of the motor are measured by the impedance analyzer.The actual resonant frequency of the measured motor is different from the simulation result by 0.19% which verified the accuracy of the scheme and simulation results.Design and build ultrasonic motor driver,the driver can output frequency between 20KHz~100KHz,the peak-to-peak voltage is continuously adjusted between 0~200V,and it can complete the frequency automatic tracking.The maximum linear velocity of the air bearing slider is 160mm/s,which indicates that the motor has good driving ability.The positioning and stepping experiments were carried out and the minimum step distance of the platform is 50 nm,the positioning accuracy of the motor can reach 100 nm,the positioning noise is 50 nm.