Design principle and experiment of gradient friction material for ultrasonic motor

As the key contact material part in ultrasonic motor (USM) system, friction materials play a very important role in USM by their influence on its efficiency, speed, torque, etc. Due to the special driving principle, contact and output properties of USM are influenced strongly by wear of friction material. Therefore, studies on special and high performance of friction material for USM are essential. Researches showed that the stability of contact and output of USM could be improved by using friction material with special gradient properties. In this paper, one kind of gradient coating friction material was made according to design principle of gradient friction material for USM. The gradient friction material is combined by three coating layers. Its elastic modulus declines from surface layer to bottom layer with decrease of whole thickness of gradient friction material. The contact state and drive properties of USM were measured between gradient friction material and one kind of homogeneous friction material. Compared to homogeneous friction material, USM with gradient friction material can obtain more stable of contact state and drive properties. The result could provide experimental guidance for design and choosing of friction material for USM.