Research On The Dynamic Characteristics Of Standing Wave Linear Ultrasonic Motor

Due to its unique characteristics including compact structure,high-precise positioning under low speed and the ability to output rectilinear motion directly,the standing wave linear ultrasonic motor(SWLUM)has many important applications in many diverse fields such as precision positioning,industrial manufacturing and aerospace and so on.However,the SWLUM has many complex dynamic characteristics because of the specific stator material(piezoelectric ceramic)as well as the friction-drive operation mode.With the development and application requirements of the ultrasonic motor,people demand for higher operation stability and reliability of the motor,which requires us to carry out more thorough and comprehensive research on its dynamic characteristics.For these reasons,this paper focuses on the fundmental and complex dynamical characteristics in SWLUM,and both the theoretical and experimental work are carried out.The main contributions of the dissertation are summarized as follows:(1)The research status on the dynamics of the ultrasonic motor both home and abroad are reviewed and summarized,and the necessity of the futher studies for the dynamic characteristics of SWLUM is clarified.(2)A SWLUM with in-plane longitudinal and bending mode is fabricated for experimental studies,and the relevant performance tests are performed for the prototype,and the results indicate that the prototype has good mechanical characteristic and stable operation ability.(3)The intermittent contact characteristic between the stator and mover of the SWLUM is verified via an electric contact method.(4)The whole-machine dynamic model of the prototype is developed by using Hamilton pricinple and Rayleigh-Ritz assumed mode method.The resulting model can be used to analyze many fundmental dynamical characteristics including the reasonant frequencies of the stator,the electromechanical coupling coefficient,the drive mechanism,the influence of the input parameters and the contact state between the staor and mover on the output performance of the motor.It is shown that the developed model can be used to understand the drive mechanism of the SWLUM and evaluate the output performance of the motor.(5)Based on a well-known SWLUM,a novel friction contact model is proposed,which is applied to investigate the stick-slip-separation dynamics in SWLUM.Simulation results show that stick-slip motion can occur with greater preload and lower excitation voltage,and the reducing friction induced by unltrasonic oscillation at the interface acts to suppress the occurrence of stick-slip motion at the contact interface.Furthrtmore,it is also found that slip-separation motion is favorable for the speed output of the motor,while the stick motion at the interface is unfavorable for the speed output and even causes the nonlinear deadzone behavior.(6)A vibro-impact physical model simulating the impacts between the stator and mover is proposed,which is used to study the contact dynamics between the stator and mover of the SWLUM with hard friction pairs.Based on the classical coefficient of restitution method,the corresponding mathematical model is established to numerically simulate the vibro-impact dynamics between the stator and the mover taking into account the oscillation of the stator barycenter.Furthermore,the proposed model can be applied to detect and simulate nonlinear sticking motion that can occur when the stataor impacts the mover via a Lagrange multiplier.(7)Considering the nonlinear vibration characteristics of the stator under higher voltage excitation,a whole-machine dynamic model based on nonlinear piezoelectric constitutive relations is developed to analyze thermal-mechanical-electric coupling dynamics of the prototype.The simulation and experimental results show that the developed model can be used to predict the dynamic change of the stator temperature for long-term operations of the motor,evaluate the influence of the thermal-mechanical-electric coupling effect on the output performance of the motor,and capture some nonlinear characteristics including resonance frequency drift and speed saturation when the motor is subjected to higher voltage excitation.