Electromechanical modeling and high speed design of a tubular ultrasonic motor

Tubular ultrasonic motors are one of the simplest yet effective methods to realize rotational ultrasonic motors. In this paper, electromechanical modeling of a tubular ultrasonic motor is achieved using assumed-modes method, Euler-Bernoulli beam theory, and constitutive equations of piezoelectricity. Upon validating the analytical model using finite element method (FEM) and the experimental result, effect of the design variables on speed is investigated using sensitivity analysis. The result proves that the speed of the motor is almost independent of the tube length for a constant length ratio of the tube and piezo-plates. Excellent agreement between the experimental and analytical model is observed. In addition, a set of guidelines for high speed designing of the stator is proposed. The results of this paper greatly facilitate design of tubular ultrasonic motors with respect to achieving high speed motor.