Torque Characteristics of Interior Permanent Magnet Spherical Actuators

Actuating systems with multi degrees of freedom (multi-DOF) are composed of several single-DOF motors, which res ults in large, heavy and complicated structures. Therefore, multi-DOF actuators are expected to become a key technology to solve these problems, and various spherical actuators have been proposed. We have proposed a surface pennanent magnet (SPM) type outer rotor spherical actuator. In order to avoid the increase of the size the mover is supported using pillars with a spherical ball at their tip. Due to this support device, the inner surface of the mover must be covered with a resin part, and this increases the air gap length. In order to solve the problem, an interior permanent magnet (IPM) type is employed. By embedding the permanent magnets inside of the mover, the resin part is removed and the air gap length is decreased. Due to this structure, a high torque can be real ized. In this paper, the torque constant characteristics of the IPM type spherical actuator is investigated and compared with those of SPM type spherical actuator.