Research On Miniature Hollow Inertial Ultrasonic Motor For Mobile Phone Zoom System

With the development of precision electronics,biomedicine,and other fields,the traditional motor has been unable to meet the needs of lightweight,miniaturization,and ultrasonic motor due to fast response speed,compact structure,power failure self-locking,strong anti-interference ability,and other advantages in various kinds of motors,especially ultrasonic motor in the field of mobile phone lens application.However,it is still very difficult for mobile phone cameras to achieve high multiple optical zooms due to the lack of a suitable micro ultrasonic motor to drive the lens.Therefore,this paper designs a hollow inertia ultrasonic motor for a mobile phone zoom system to determine the motor’s working mechanism completes the friction analysis between stationary components,constructs the dynamic model of the motor,and simulates and analyzes the external factors affecting the output performance of the motor.Optimize the motor stator structure,complete prototype assembly,and experimental bench construction,and test the basic performance of the motor.Design a composite control system and verify the feasibility of the motor for mobile phone zoom function through control experiments.The specific research content is as follows:(1)According to the development status of micro ultrasonic motor and mobile phone zoom lens,analyze the basic conditions that micro ultrasonic motor needs to meet to realize mobile phone optical zoom technology.By comparing the performance of different piezoelectric components,the piezoelectric bimorph was selected as the motor’s stator,and the bimorph vibration equation was established.According to the application requirements of the ultrasonic motor,the mechanical characteristics of different flexible hinges are compared,and the straight circular flexible hinges are selected for the motor stator.The stator structure of the hollow inertia ultrasonic motor and the adjustable pre-pressure slider actuator was designed,and the friction analysis of the contact interface between the stator and actuator of the motor was completed.(2)The dynamic model of the whole motor is constructed by establishing the analytical model of the motor stator dynamics and combining it with the friction model of the contact surface between stationary actuators.The influence model of the external conditions of the motor on the motor performance is obtained by simulation analysis.The influence degree of different piezoelectric bimorph and straight circular flexible hinge structure size parameters on the motor performance was analyzed by orthogonal test and normalization.The optimal stator structure was selected and the optimized motor operating frequency was obtained by simulation.According to the theoretical derivation,the sawtooth wave excitation signal with the platform is selected to improve the motor running speed.(3)The basic parameters of piezoelectric ceramics are tested experimentally to ensure the accuracy of theoretical calculation and simulation.Assemble motor prototype,design and build motor performance test platform,mainly to test the influence of external factors on the motor prototype,including the resonant frequency of the prototype under the corresponding working mode,the output speed of the prototype under different excitation voltage,frequency and pre-pressure,the maximum output force of the prototype under resonant frequency,start-stop characteristics and stability.At the same time,the experimental results are compared with the simulation results to further verify the accuracy of the simulation.(4)According to the hysteresis characteristics and speed output characteristics of hollow inertia ultrasonic motor,the motor compound control system is designed,including the feedforward control based on the Duhem hysteresis inverse model and the feedback control based on BP neural network improved PID.Through simulation and comparison,the position error of the composite control is reduced by 25.83% compared with that of the feedforward control,which fully demonstrates the effectiveness of the composite control system in motor position control.The experimental results show that the proposed miniature hollow inertial ultrasonic motor can control the position of the lens in front of the image sensor,which proves the feasibility of its application in the automatic zoom function.