Abstract: The analytical model was proposed to analyse the steady-state characteristics of the traveling-wave type ultrasonic motor (TWUSM) based on the energy equivalent method. Firstly, the simplified equivalent composite beam model of the piezoelectric stator was presented with the energy equivalent principle. By involving the rotary inertia and the shearing deformation of the piezoelectric stator, the equation describing the frequency and the amplitude of transverse vibration of the stator were obtained according to the Timoshinko beam theory. Then the force transfer model and the efficiency of the contact surface between the stator and the rotor were derived with the elastic contact theory. And the mechanical performance expression and the output power of the TWUSM were defined by regarding the friction loss of the contact surface and the output power of the rotor as one of parts of the equivalent damp loss of the stator vibration. Finally, all factors, such as the physical demension, the material parameters, the preload, the driving frequency and the friction layer characteristics, influence the vibration characteristics and the mechanical characteristics were analyzed, and the accuracy of the analytical model was verified by comparison with the experimental results.

Key words: Analytical model, Energy equivalent, Mechanical characteristics, Traveling-wave type ultrsonic motor, Vibration performances