Modeling, analysis and suppression of current harmonics of Langevin-type ultrasonic motors under high voltage.

For achieving high speed and large thrust, Langevin-type ultrasonic motors (LTUM) are generally operated under high voltage. However, high voltage causes the current harmonics of piezoelectric material nonlinear phenomena, which will decrease the efficiency, the output force, and the accuracy of LTUMs. In this study, the nonlinearity of current harmonics of LTUM are described and analyzed by a novel nonlinear equivalent circuit model using Lagrange equations. Thereafter, based on a nonlinear tuning method, a specific driver circuit is suggested to suppress the current harmonics. Experimental results validate that the time response of the current is consistent with that of the model and furtherly demonstrate that the total harmonic current distortion decreases by 68% utilizing the proposed nonlinear tuning method under 500 Vpp. • A nonlinear dynamic model and simple identification method of a Langevin-type ultrasonic motor are proposed to describe the current harmonics. • A nonlinear tuning method and drive circuit are developed to suppress current harmonics under high voltage. • Experiment results demonstrate that the time response of the current was consistent with that of the model. [ABSTRACT FROM AUTHOR]