Development of an ultrasonic motor as a fine-orienting stage

This paper describes the development of a new application of a traveling-wa ve-type ultrasonic motor as an orienting stage with the precision to cover the fine rotation of a tool at a submicrometer-level orienting system. The defined term of orienting here implies the micro positioning with a fine ro tation motion. The proposed fine-orienting stage consists of a half spheric al-type rotor and three pieces of ring-type stators. The fine rotation at t he center of the rotor is determined by controlling friction forces, which generate rotation at the three contact points between the rotor and the sta tors. A method to rotate the rotor in fine rotation to attain a desired ori entation is also proposed. Three different sizes of ultrasonic motors are p resented to verify performance of the ultrasonic motor as a fine-orienting stage and to investigate an extreme of the ultrasonic motor motion. The res ults of the three models of the orienting stages are discussed and the vali dity of the ultrasonic motor as a fine-orienting stage is confirmed.