Design And Optimize Of A Double-vibrator Rotary Type Traveling Wave Ultrasonic Motor

Rotary type traveling wave ultrasonic motor(RTWUSM)is one of the most representative ultrasonic motors in the market,which has experienced mature development and been widely used in different walks of life.Its shape and output method are similar to the traditional electromagnetic motors,and there are many performance advantages in its uses,such as compact structure,excellent control,high torque at low speed,high energy density,power failure self-locking,no electromagnetic interference,etc.These performance advantages are sufficient to attract the attention of researchers.In traditional RTWUSM,only one stator and one rotor are designed in one motor.Using the inverse piezoelectric effect of the piezoceramics adhered to the stator surface to excite the high-frequency vibration of the stator,and the rotor is rotated by the stator under the effect of preload and friction.However,in the face of ever-increasing application requirements,the insufficient performance of rotary type traveling wave ultrasonic motors has been tested increasingly.The emergence of multiple stator and rotor combined motors based on increased power sources provides a good idea for improving motor performance.However,multiple stator and rotor combined motors have serious problems in many aspects,such as complicated structure,difficult assembly and debugging,and difficulty in ensuring the consistency of multiple power performance,which constrain its development.Therefore,it is an important problem that needs to be solved to find a smart,convenient and easily adjustable method to increase the motor performance.This paper draws on the numerous research results in improving the performance of ultrasonic motors.Based on the design and optimization of a double-vibrator rotary type traveling wave ultrasonic motor,the research on the new motor structure design,model analysis,and parameter optimization techniques is carried out.The content of this article includes the following aspects:The related theory of traditional RTWUSM is studied.The key factors of the motor performance are analyzed through the vibration characteristics of the vibrator and the contact state analysis,which provides the direction for the motor performance optimization.The vibration model of stator,common frictional contact models,especially the Hertzian contact model are introduced in detail,which provide analysis method for establishing motor model.The design concept of double vibrator RTWUSM is introduced,the mechanism is described,the overall structure scheme and the design method of two vibrators meeting the design requirements are analyzed.The theory of particle motion synthesis and Hertzian contact model are used to establish the motor mathematical model.Based on the analysis of the mechanism and the mathematical model,the determining factors of the motor performance are analyzed,which point out the performance optimization direction of the motor.A method for optimizing the stator structure based on combinational algorithm is studied.The sensitivity analysis,the finite element method and the adaptive genetic algorithm are adopted for the parameters optimization.The stator vibration characteristic such as amplitude,modal frequency and speed coefficient are selected for optimized object.The uses of the sensitivity analysis and the finite element method have solved the problem of multi-parameter and nonlinear optimization,and the use of combination fitness for related targets has solved the multi-objective optimization problem.A method for optimizing the rotor structure based on multi-objective algorithm is studied.Under the condition of fixed stator structure and vibration performance,the optimal rotor structure parameters are found to optimize the performance of the motor.The BP neural network was used to fit the model network of rotor parameters and motor output performance.Then the multi-objective optimization algorithm NSGA-II was used to find the optimized objectives based on the fitting network.The end,the Pareto optimal solution provides optimal structure parameters of the motor.Set up the driven platform and made the prototype,the simulation results in the structural design,theoretical modeling,performance analysis and parameter optimization are all validated by comprehensive experiments.The motor performances in the dual-drive working mode and the single-drive working mode are compared.The motor maximum speed driven by double vibrators is 1.59 times as it obtained single driven by the stator,the maximum torque is 1.28 times as single driven by the stator,and the maximum power is 1.62 times as single driven by the stator.Therefore,double-vibrator motor has better performance than single drive motor.When two waves are traveling in the same direction,the motor performance can reach more than 90% of the sum of performance in single driven by stator and single driven by rotor.When two waves are traveling in the different direction,there is also a significant differential effect.