Finite element model updating of a rod-type ultrasonic motor based on response surface method

The existing finite element model (FEM) of rod-type ultrasonic motor is usually simplified by means of continuous composite structure style and ignores the actual contact characteristics between the parts of ultrasonic motor, leading to a wide difference between the calculated values and experimental results. To solve the problem, a FEM updating method of rod-type ultrasonic motor is presented to obtain a high-accuracy FEM. By comparing with the experimental modal analysis results, this method takes into account the bolt pretension and the normal contact stiffness and friction coefficient of the contact surface of ultrasonic motor, and then the FEM is updated by the response surface method, which includes selecting the significant parameters of working mode of motor and building the response surface model to replace the FEM. And the result of updating shows that the average error of modal frequencies of updated model drops to 0.21% from 1.20%, and the accuracy of FEM is obviously improved, which indicates the FEM updating based on response surface method has an application value on the design for a rod-type ultrasonic motor, as well as the similar sandwich type piezoelectric.