Finite element solution for intermittent-contact problem with piezoelectric actuation in ring type USM

In this paper, a 3-D finite element (FE) framework with fully coupling among the piezoelectric coupled stator, rotor and contact interface to simulate the steady-state and transient behavior of ultrasonic motor (USM) is proposed, which produces fairly accurate results at moderate computational cost. The difficulties of FE analysis for a general intermittent compact problem with piezoelectric actuation are highlighted. The equivalent piezoelectric force (EPF) solution procedure is proposed where the converse piezoelectric effect is simulated using thermal analogy. This allows the stator, rotor and contact interface to be solved as a dynamically coupled system providing the transient intermittent-contact responses. However, if only the steady-state response of the USM is of interest, then it will be more efficient to use the proposed steady-state contact (SC) procedure. Both procedures have been performed using ABAQUS®ABAQUS® version 6.4. For given applied torque, axial force, and piezoelectric drive voltages as inputs, the general measures of USM performance are obtained and compared with published theoretical, numerical and experimental results. The results provide confidence to the proposed approaches in modeling and analysis of USM at moderate computation cost and can serve as an efficient design tool for optimizing prototypes.