A novel modal-independent ultrasonic motor with dual stator

In this paper, a novel modal-independent ultrasonic motor with dual stator is proposed, in order to relieve the difficulty of adjustment for coincidence of modal frequencies of a stator for multi-modal coupling type ultrasonic motor (USM). It consists of two stators (an upper stator and a lower stator) and a rotor. The stators are excited the 3rd longitudinal vibration mode, by arranging the location of rotor and two stators, the rotor can realize rotary motion by friction effect with the stators. The rotor is mounted between the maximum deformation location of the upper stator and the nodal line of the lower stator. Since two stators are the same and are excited the same vibration mode, the modal-independent USM can adjust the coincidence of modal frequencies conveniently. Furthermore, the stator of the modal-independent USM has the characteristics of simple structure, which promised advantages of easy designing, manufacturing, miniaturizing and suitable for the mass production of USM. Modal test shows the disparity between the modal frequencies of the stators is 0.78%. Mechanical characteristic test shows the rotary speed of the USM is 75 revolutions per minute (clockwise) and 65.8 revolutions per minute (anti-clockwise) at the voltage of 400 Vp-p. And at the same voltage, the maximum torque is 8.4 N·mm. The resolution of the modal-independent USM can up to 0.34 mrad at the applied voltage of 400 Vp-p.