Basic Characteristics of a Multi-Pole Spherical Synchronous Motor

A multi pole spherical synchronous motor with two degrees of freedom is developed and tested. The developed motor has a rotor supported by a gymbal mechanism and a stator with two pairs of armature pole units. 260 small permanent magnets are attached on the rotor surface so that the North Poles and the South Poles appear on the concentric circles alternatively. Four armature pole units are positioned on the stator. Each armature pole unit has three windings. The pitch of the windings is 4/3 of the pitch of the permanent magnets. The motor size is 265 x 265 x 266 [mm] and the diameter of the rotor is 130 [mm]. The motor has two degrees of freedom and the working area is +/- 45 [deg] around X and Y axis. Maximum trajectory control error is 0.7 [deg]. The maximum repeated positioning error of the vertical position is 0.00348 [deg]. The maximum moving speed is 90 [deg/sec], and the maximum output torque is 0.69 [Nm].