Study On Dynamic Characteristics Of Linear Type Ultrasonic Motor In Thermal Environment

Ultrasonic motor is a new type of driver based on the working principle of inverse piezoelectric effect.It amplifies the high-frequency micro vibration generated by piezoelectric ceramics under electric field into visible macro motion by means of contact friction and bonding.It has many advantages that traditional electromagnetic motor does not have,and is often suitable for extreme working environment,so it will inevitably suffer from various mechanical shocks,high-temperature loads and electromagnetic coupling interference,then it will affect the stability of the structure.In this paper,the dynamic model of linear ultrasonic motor in thermoelectric environment is established,and the parametric design of various structures is studied.The specific contents are as follows:(1)The mechanical-electrical-thermal coupling dynamics modeling of the linear ultrasonic motor stator.First of all,the main stator of the ultrasonic motor can be regarded as a sandwich piezoelectric laminated beam structure composed of two layers of piezoelectric ceramic sheets and a metal core layer.In order to obtain general rules,the straight beam type and curved beam type stators are analyzed uniformly and make them interchangeable.Next,a parametric boundary condition technique is implemented by arranging springs corresponding to each generalized displacement degree of freedom at both ends of the structure.Based on the first-order shear and higher-order shear beam theories,the coupled constitutive relation of the piezoelectric laminated stator in the thermoelectric environment is deduced.Finally,its thermo-mechanicalelectric coupling control differential equation is obtained by applying Hamilton’s principle.(2)MRRM analysis and numerical discussion of linear piezoelectric stator.Firstly,the time-domain governing differential equations derived above are transformed into the frequency domain through Laplace transformation.According to the solution principle of MRRM and the generalized Hooke’s law,the structural phase relationship and scattering relationship of the piezoelectric stator are obtained.Then these matrix equations are integrated and transformed and solved.,obtained the analytical solutions of its natural frequency and transient displacement,and compared these calculation results with literature data and finite element software to verify the correctness of the coupled dynamics model and the effectiveness of MRRM.Finally,from the perspective of structural safety and stability design,a series of parametric studies of free vibration and transient response are carried out on the spring’s arbitrary boundary conditions,material properties,geometric properties,and thermoelectric environment.(3)Dynamic analysis of combined stator of ultrasonic motor based on MRRM.First,through modal simulation,four kinds of combined piezoelectric stator structures to be analyzed are established.Then,at the coupling point of each segment structure,the generalized displacement and generalized force of each substructure are transformed by coordinate transformation and virtual node spring connection technology.To the overall coordinate system,the dynamic modeling method from onedimensional structures to various two-dimensional combined structures can be expanded,and then MRRM is used to solve and verify its correctness.Finally,considering the working principle of ultrasonic motors,the combined A parametric study of the steady-state response of piezoelectric stators and general external load forms is carried out.(4)Dynamic characteristics of piezoelectric stator under complex excitation.In order to be closer to the various complex excitations in practical engineering,the external load wave source vector in the piezoelectric stator MRRM formula is first rederived and separated,and then the dynamic responses under the two complex actions of moving load and distributed load are analyzed.The analysis is carried out,and the stability design of the stator under different environmental temperature rises,different motion states and different excitation directions is further discussed.