Development of rotary-type noncontact-synchronous ultrasonic motor

As an application of noncontact transportation utilizing the near-field acoustic levitation phenomenon, a rotary-type noncontact-synchronous ultrasonic motor (NCSyn-USM) using acoustic viscous force was examined. The NCSyn-USM consisted of six fan-shaped stators arranged in a circle and a flat fan-shaped rotor installed above stators via small an air gap. The possibility of the NCSyn-USM was investigated by both of numerical simulation and measurement. From the acoustic-structure and fluid-structure interaction analyzes by finite element method, the correlation between the sound pressure in the air gap and the rotational force was obtained, and it was found that the rotational force was increased by utilizing the acoustic resonance of the air gap. In the experiment, the change of rotational torque with respect to the rotor angular position approximately corresponded with analysis results. The rotation of the rotor by switching driving stators was actually obtained, so that a rotary-type NCSyn-USM would be realized. (C) 2019 The Japan Society of Applied Physics