Macro-Micro Modeling and Performance Analysis of Traveling Wave Ultrasonic Motors

The rotation of the annular ultrasonic motor directly relies on the micron-amplitude & high-frequency vibrations of the stator to contact the friction layer bonded to the rotor, and the roughness of both the stator and the friction layer is at the micron level. A novel contact model of the ultrasonic motor considering the multi-scale rough surface is proposed. First, the microscopic morphology of the rough surface is measured using the profilometer, and the continuous deformation expression related to the contact load of the asperity is introduced. The surface equivalent stiffness coefficient is calculated using probabilistic statistical theory. Then, the original morphology is decomposed using the wavelet transform to obtain the mesoscopic waviness data, which is then fitted to adjust the normal vibration function of the stator. Subsequently, the output characteristics of the ultrasonic motor are calculated using the Coulomb friction theory. The experimental data collected agree with the simulation results, which verifies the accuracy of the proposed multi-scale contact model.