Modelling of a novel spherical permanent magnet actuator

A new form of actuator with a spherical permanent magnet rotor and a simple stator winding arrangement is described and analyzed. The actuator incorporates a simple position sensing technique, and, by utilizing a rare-earth permanent magnet and optimizing its design, is capable of developing a high specific torque. The magnetic field distribution, torque vector and back-EMF constants are derived analytically, and a detailed kinematic analysis is presented. These allow a complete and accurate dynamic model of the actuator to be established, and facilitate the development of the closed-loop control law