Torque Map Based Rotation Control Technique of a Spherical Motor driven by Electromagnets Applying Convex Programming Problem

Abstract

　This study proposes a rotation control technique for a spherical motor driven by electromagnets using a torque map that expresses a rotation torque to the rotor by an electromagnet flowing unit current and is obtained in advance for various relative spatial relations between the electromagnet and the rotor. The rotation control technique determines an optimal set of currents for electromagnets arranged in the stator by solving the convex programming problem obtained from the equations expressing the relations among the currents of electromagnets and rotation torque under constraints and a convex-type objective function. The applicability of the technique is demonstrated by an example to obtain an optimal set of currents for a constant torque rotation of a spherical motor that arranges 12 permanent magnets on the surface of the rotor and 10 electromagnets in the stator.