Research On Dynamics Modeling And Application Of V-shaped Linear Ultrasonic Motor

The V-shaped linear ultrasonic motor is a representative of ultrasonic motors.With the characteristics of large output power,high speed and large stroke,the V-shaped linear ultrasonic motor has shown the potential applications in the precision engineering,aerospace,bio-engineering,and other fields.The motor utilizes coupling symmetrical and asymmetrical modes of a V-shaped piezoelectric transducer to generate an elliptical motion at the driving foot for driving a mover with the friction.With the development of the V-shaped linear ultrasonic motor,it is necessary to establish a dynamic model for the performance prediction and control.However,current researches on the dynamics model of ultrasonic motors mainly focus on traveling-wave rotary ultrasonic motors and longitudinal-bending coupling mode linear ultrasonic motors,and lack of dynamic modeling and analysis on the V-shaped linear ultrasonic motor.Therefore,the establishment of the dynamic model of the V-shaped linear ultrasonic motor has important theoretical significance and application value to carry out the analysis of operational mechanism,performance simulation,control,drive,and structural design.The main contributions of the dissertation are summarized as follows:1.The relationship between the vibration of the beam and the formation mechanism of an elliptical motion at the driving foot is analyzed.It is pointed out that the elliptical motion at the driving foot is formed by the mutually orthogonal symmetrical and asymmetric modes.The configuration of piezoelectric ceramics on the V-shaped stator is discussed.The structural features,operating principles,and mechanical characteristics of the sandwich and bonded type V-shaped linear ultrasonic motor are described,respectively.2.An analytical model of the V-shaped stator is presented.Based on the longitudinal vibration and bending vibration equations of the beam,the motion equation of the whole V-shaped stator is derived through compatibility conditions and boundary conditions.Using the Hamilton principle,the electromechanically coupled Lagrange equation is obtained.Based on the analytical model,the natural vibration characteristics are obtained;the relationship between the structural parameters and the natural frequencies of the symmetric and asymmetric modes are studied;the relationship between the displacement of the driving foot and the phase difference of the two-phase signals is analyzed;the relationships between the electromechanical coupling coefficients of the symmetric and asymmetric modes and the variable cross-section size as well as the included angle are investigated.The results of the experiments show that the analytical model can indicate the vibration characteristics and the electromechanical coupling characteristics of the stator.3.A dynamic model of the V-shaped linear ultrasonic motor is established,including the analytical model of the V-shaped stator,the friction model,and the dynamic model of the mover.By using the dynamic model,the mechanism of the frictional drive is revealed;the dynamic characteristics of the stator and the mover are analyzed;the mechanical characteristics,the electrical characteristics,and the transient characteristics of the motor are studied.The results of the analytical model are in good agreement with the results of the experiment.The control model is established based on the dynamic model.The controller was designed using the backstepping method,and the control experiments are carried out;the results indicate that the positioning error is less than 0.8μm.The experimental results show that the dynamic model can be used not only for the performance prediction and dynamic characteristics analysis,but also for the control.4.Considering the nonlinear phenomenon of the sandwich type V-shaped linear ultrasonic motor under a high voltage and high pre-stress,an equivalent circuit model of the motor with a nonlinear capacitance is proposed.The nonlinear dynamic characteristics of the circuit are analyzed and verified by experiments.Based on the results of model analysis,a nonlinear suppression method is proposed and a new type of the driving circuit is designed.Using the new driving circuit,the total harmonic current distortion rate decreases by 68%,and the high harmonics have been effectively suppressed.5.The automatic focusing system,rotary motion platform,and high-speed mechanical switch driven by the V-shaped linear ultrasonic motor are developed.According to the specific application requirements,the control strategy based on the motor model is proposed,and devices mentioned above are effectively controlled.