Development of a novel spherical permanent magnet actuator

The analysis, design and control of a novel actuator, with a spherical permanent magnet rotor and a simple stator winding and position sensing arrangement, is described. The actuator is capable of two degrees-of-freedom, and has a high specific torque. Expressions for the magnetic field distribution and the torque vector and back-EMF constants are derived analytically, and optimal design parameters, which result in maximum output torque or maximum acceleration for a given payload, are derived. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model and the application of a robust control law. The validity of the analysis and design techniques, and the effectiveness of the control strategy, have been confirmed by measurements. (10 pages)