FEM Analyses Of Levitation Characteristics Of A Noncontact Rotary Ultrasonic Motor With A Bowl-shaped Stator

This research is supported by National Natural Science Foundation of China (Grant Nos.11174149,51075212and91123020) and Aviation Science Foundation (Grant No.2011ZC52035).This paper was focused on the FEM analysis of the axial levitation and actuation actuator of theaxial/radial coupling type piezoelectric actuator prototype, which is the miniature of the bowl-shapedpiezoelectric actuator prototype, with COMSOL MULTIOHYSICS software. The distribution of thesound pressure in the air gap between the stator and the rotor was calculated. At the same time, theacoustic radiation force and levitation stiffness were also calculated. The main research achievementswere summarized as follows:1. I Designed a new type of piezoelectric actuator by compacting the bowl-shapedpiezoelectric actuator. Analysis dynamic mechanism of this new actuator.2. I Measured this actuator. The actuator consisted of a bowel-shaped radial stator andcylinder-shaped axial stator. I built a test platform and measured the modal, levitation height andspeed characteristics at the same time. The rotor which was semi-sphere shape was levitated byacoustic field in the air gap between the radial stator and rotor, generated by a traveling wavevibration of the stator. It has no mechanical bearing and provides a full-noncontact rotary drive.3. A FEM model was built in the COMSOL MULTIOHYSICS software. After verifying theeffectiveness of the calculation method by experimental results, the distribution of acoustic radiationpressure on the rotor’s surface. To solve the problem which appeared in the experiment,dependenceof the levitation force and stiffness on design parameters were theoretically investigated.4. The design parameters include the radius of the stator’s radiation surface, shape of the rotor,dimensions of a ring slot on the stator’s surface, etc. Useful guidelines were obtained by the FEMcalculation. The acoustic radiation pressure on the rotor’s surface was uneven. The levitation forceand stiffness were very sensitive to the radius of the stator’s radiation surface and the rotor’s shape. Aring slot on the stator’s outer surface may increase the levitation force and stiffness if its size andposition were proper.