Performance evaluation of a bimodal standing-wave ultrasonic motor considering nonlinear electroelasticity: Modeling and experimental validation

Abstract

This paper proposes a nonlinear whole-machine dynamic model for a typical bimodal standing wave ultrasonic motor considering nonlinear electroelasticity of piezoelectric vibrator under high excitation voltage. To capture the inherent nonlinearities of the piezoelectric element, nonlinear constitutive relations of piezoelectric element are adopted to derive the nonlinear electromechanical coupling model of the stator. The contact mechanism between the stator and the mover including stick-slip-separation dynamics and asperity contact mechanics is modeled based on a physical-based equivalent spring model and a modified Coulomb friction model. The measured nonlinear relationships between the excitation voltage and the amplitude response of the stator near resonant frequency are used along with analytical approximations for the nonlinear vibration responses by harmonic balance method to identify the critical nonlinear parameters. Finally, experiments are conducted to validate the proposed model, and the results show that the simulations agree well with the experimental results. In particular, nonlinear speed saturation phenomenon and the resonant frequency drift of the motor can be predicted and analyzed by the developed model when the motor is driven at a higher voltage, which are useful for the performance evaluation and working range choice of such motors under high-power input conditions.