Application Research Of Rotary Ultrasonic Motor With Variable Aperture

Variable aperture is a device used to control the amount of incoming light,by adjusting the size of the light through aperture,to provide the camera mechanism with the right amount of light flux to optimize the imaging quality,in aviation,medicine,video and other fields have a wide range of applications.The traditional variable aperture is usually driven by electromagnetic motor.Due to electromagnetic interference,small driving force,large size and other shortcomings of the electromagnetic motor,resulting in the drive variable aperture easily caused by the opening and closing jams,or even can not be successfully driven.The ultrasonic motor with low speed and high torque,compact structure,no electromagnetic interference,and high positioning accuracy fits the demand of driving variable aperture.In this thesis,a rotary ultrasonic motor for variable aperture is proposed.The rotor of this motor is directly connected to the blade,and the aperture diameter of the aperture is changed by driving the opening and closing of the blade through the rotor rotation to realize the adjustment of the light intake.Based on the piezoelectric theory,the piezoelectric oscillator finite element model of the rotary ultrasonic motor is established and the stator structure is optimized;the rotary ultrasonic motor prototype is fabricated and the output performance of the motor is tested;the variable aperture prototype is fabricated and then its opening and closing function is verified through experiments.The main research contents of this thesis are as follows:(1)The working principle of rotating ultrasonic motor is analyzed to determine the motion trajectory of stator tooth surface masses based on the condition of traveling wave formation;then the conditions of rotor motion generation are determined by analyzing the stator-rotor contact model.(2)The structure of the rotating ultrasonic motor for variable aperture is proposed,which uses a column on the inner wall of the housing to fix the stator and a waveform spring to provide pre-pressure.Firstly,the finite element model of the piezoelectric oscillator is built by the finite element analysis software,and its modal analysis is carried out to determine its operating modal frequency;then the influence of the key stator dimensions on the modal frequency is analyzed to determine the optimal stator dimensions;then a harmonic response analysis is performed to determine the circumferential displacement and axial displacement amplitudes of the tooth surface plasmas,and finally a transient analysis is performed to determine the trajectory of the tooth surface plasmas to verify the The piezoelectric oscillator design is validated.(3)The piezoelectric oscillator is fabricated and the test platform is built.Determine the resonant frequency by measuring the impedance/capacitance and vibration characteristics tests;measure the amplitude of the stator tooth surface mass at the resonant frequency and compare it with the simulation results to verify the reliability of the simulation results.(4)The rotary ultrasonic motor and the prototype equipped with variable aperture were developed respectively,and performance tests and functional tests were completed.The rotating ultrasonic motor prototype was produced,and the output characteristics such as no-load speed and blocking torque were measured;the prototype with variable aperture was produced,and the opening and closing times of the blades were measured after the functional tests such as opening and closing of the aperture were completed.The structure meets the needs of practical application scenarios and can solve the problems of limited driving force and large size of the current variable aperture,which has important practical value.