Study On Stable Rotation Characteristics Of MEMS Traveling Wave Ultrasonic Motor

The MEMS(Micro-Electro-Mechanical Systems)traveling wave ultrasonic motor is characterized by its small size,simple structure,low-speed high-torque,high positioning accuracy,power-off self-locking,and easy implementation of mass production.The current rotating issues faced by MEMS traveling wave ultrasonic motors include large fluctuations in no-load speed and the inability to continuously and stably output torque.This thesis aims to address these issues by analyzing the stable rotation characteristics of the motor,which is of significant importance for understanding its rotational state and improving its output performance.MEMS(Micro-Electro-Mechanical Systems)traveling wave ultrasonic motor is a novel micro ultrasonic motor that utilizes MEMS technology to simplify the structure and reduce the volume of the conventional ultrasonic motor to achieve butch production.This type of motor realizes low speed with high torque,high positioning accuracy,and power failure self-locking.The main issues faced by the current MEMS traveling wave type ultrasonic motor are large fluctuations in no-load speed and inability to output stall torque continuously and stably,both of which are closely related to the motor’s stable rotation characteristics.This thesis analyzed the generation and transmission process of the driving force based on the ultrasonic motor’s driving principle.It characterized that the stability of the traveling wave on the stator surface as well as the effectiveness of contact force transmission,are the factors that affect the stable rotation of the motor.Firstly,the influences of standing wave amplitudes and phase differences are investigated to improve the effectiveness of synthesizing a traveling wave.Additionally,an axial micro-contact model suitable for MEMS traveling wave ultrasonic motor is established to study the contact issue.Finally,the optimal preload was measured to achieve stable rotation.The research content of this thesis is as follows:1.Analysis of factors that affect the steady rotation of the motor.The process of motor operation involves synthesizing a traveling wave on the elastic stator and transmitting force through the contact surface between the stator and rotor.The traveling wave is easily affected by the stator structure during the synthesis process,causing unstable wave amplitude and unbalanced contact force on the rotor during the contact process,which affects the transmission of contact force and ultimately affects the stable rotation characteristics of the motor.2.Analysis of factors that affect the amplitude of a traveling wave.The principle of traveling wave synthesis suggests that the inconsistent amplitudes and phase differences in the two standing waves that make up the traveling wave are responsible for its instability.By studying the motion trajectories of the surface particles under different scenarios,it has been found that an unstable amplitude of the traveling wave will lead to fluctuations in the no-load speed,as well as hinder the ability to output stall torque continuously and stably.3.Research on a micro-contact model of MEMS traveling wave ultrasonic motors.As the contact model currently used for conventional traveling wave ultrasonic motors is not appropriate for MEMS traveling wave ultrasonic motors,a new contact model has been proposed for a rigid rotor and a compliant stator.This model focused on analyzing the contact area’s boundary as well as the contact deformation.Based on this model,the no-load speed and stall torque of the motor were derived.To validate the effectiveness of the model,modal experiments were conducted to capture contact surface deformation.4.Manufacturing of the stator and experimental verification of motor rotational output characteristics.The manufacturing process of the stator was introduced,and the manufactured stator was displayed.Given the importance of the preload structure for the stable rotation of the stator,the preload structure and the preload calibration process were illustrated in detail.The motor’s rotational speed and the stall torque were tested after measuring the surface friction coefficient.The validation of the model was verified by comparing the model results and the experimental results.At last,the impact of damping on the amplitude of a traveling wave was revealed.