Mechanical modeling of longitudinal oscillation ultrasonic motors and temperature effect analysis

A mechanical model of a longitudinal oscillation ultrasonic motor and a method of analyzing its frequency-temperature characteristics are presented. The sticking and slipping between the stator and the rotor in the intermittent contact region are analyzed theoretically. An analytical expression for the motor's driving force that undergoes continuous changes is given. The behaviors of the ultrasonic motor (USM), including the revolving speed of the rotor, the output kinetic energy from the rotor to the other object, the input kinetic energy from the beam tip, and the efficiency of the energy transformation, are discussed. The effects of the initial compressive force, driving frequency, load, and the moment of inertia of the motor on the behavior of the motor are examined. In the study of the temperature effect, the course of the vibration of the piezoelectric element inside the USM is expounded, the main factors affecting the frequency-temperature characteristics are analyzed, and the analytical expression for the change of the resonance frequency with respect to the temperature is given. Numerical simulations show that the results obtained in this paper agree with reported experimental results.