Prediction of Load-Carrying Capacity in the Radial Direction for Piezoelectric-Driven Ultrasonic Bearings

This paper presents a theoretical modeling method on radial levitation force for ultrasonic bearings actuated by piezoelectric transducers with the aim of predicting their load-carrying capacity. The finite difference method is adapted to calculate the model, which is represented by a high-order multidimensional partial differential equation. The static levitation force testing experiments validate that the established mechanical model can interpret the experimental data well. This model also reveals that the ultrasonic bearing's levitation mechanism under the comprehensive action of near-field acoustic levitation effect and hydrodynamic effect when the bearing operates at high speeds. Some key factors including bearing's dynamic parameters, working media, clearance sizes, and environmental conditions that influence the ultrasonic bearing's levitation effect are discussed. The analysis of these factors can guide the ultrasonic bearing's structural design and the selection of the ultrasonic bearing's working parameters.