Improvement of the energy conversion efficiency in traveling wave rotary ultrasonic motors by increasing the elastic modulus of the friction layer

This paper investigates the influence mechanism of the elastic modulus of the friction layer on the interface contact characteristics and energy conversion efficiency of traveling wave rotary ultrasonic motors (TRUMs), based on the established stator-rotor dynamic coupling model that considers the elasticity of the friction layer and rotor. A method to enhance energy conversion efficiency by increasing the elastic modulus of the friction layer is proposed. The calculation results indicate that as the elastic modulus of the friction layer increases, the motor’s output performance and energy conversion efficiency improve, while interfacial friction loss decreases. This reduction in interfacial friction loss is attributed to the diminished tangential hindrance friction sub-zone and the enhanced shear deformation capacity at the interface contact points, which results in decreased slippage. Comparative experiments of ultrasonic motors using polyimide-based (PI) and polytetrafluoroethylene (PTFE) as friction layer materials reveal that increasing the elastic modulus of the friction layer significantly enhances the energy conversion efficiency of TRUM. Specifically, the maximum energy conversion efficiency of the motor rises from 46.3% to 52.1%, and the torque range exhibiting high energy conversion efficiency is also expanded.