Investigation On Dynamic Behaviors Of Ultrasonic Motor

The ultrasonic motor is a new type of driving device,which is characterized as simple and compact structure,high power-to-weight ratio and high torque at low speed.However,it is essentially a symmetric system subjected to inner excitation,which inevitably induces the natural frequency splitting and traveling wave distortion.The thesis is focused on the free,forced,and parametric vibrations of a typical ring ulstrasonic motor.The main contents and results are as follows:1.The natural frequency splitting and vibration shape distortion are identified,based on which an effective method for the elimination of the frequency splitting is proposed.The simulation results are well consistent with the theoretical analysis.2.The forced vibration of the ultrasonic stator is studied.The excitation condition for the traveling wave is obtained.The relationships between basic parameters and vibration behaviors are clarified.The analytical results are validated by the simulation results.3.A model with parametric excitation is developed,based on which the elliptical locus of a point on the stator surface is obtained,and the effect of the parametric excitation and nonlinear factors on the traveling wave and elliptical locus is addressed.The study lays a foundation for the design of the high-qualiy ultrasonic motors.While the thesis is focused on the ultrasonic motor,the method used can apply to other symmetric systems with fluctuating excitation.The study provides a general treatment with the dynamic design of these systems.