Development of a Novel Rotor-Embedded-Type Multidegree-of-Freedom Spherical Ultrasonic Motor

Abstract

An actuator system with multidegree-of-freedom (MDOF) motion and complicated action has recently attracted interest in the field of robotic technology. The present paper proposes a novel rotor-embeddedtype MDOF spherical ultrasonic motor (SUSM). The MDOF SUSM consists of a spherical rotor and a stator vibrator with an all-in-one structure. The spherical rotor is embedded in the center of an almost annular stator vibrator with a spherical inner surface, and a motor shaft is mounted on the rotor. The stator vibrator with piezoceramic disks and plates adhering to the surfaces of the vibrator can excite five vibration modes independently and simultaneously. The spherical rotor rotates around three axes by combining two of the five vibration modes. The present paper describes the basic construction and the operating principle of the rotor-embedded-type MDOF SUSM, modal analysis results for the stator vibrator, and experimental results based on trial manufacture. The proposedMDOF SUSM confirmed the operating principle of design has a simple structure and is compact and lightweight, so a large torque-to-weight ratio is expected to be realized.