An open-loop control strategy of a reaction sphere for satellite attitude control

This paper presents an open-loop strategy for the control of the orientation of a reaction sphere actuator. The reaction sphere is a magnetic bearing spherical motor composed of an 8-pole permanent magnet spherical rotor and a 20-pole stator. The control law is based on a rotating magnetic field obtained from a sequence of desired rotor orientations. Hence, the reaction sphere can be accelerated about any desired axis. Force and torque inverse models are developed and employed to derive the control scheme. The proposed method is successfully employed to drive a reaction sphere laboratory prototype up to 480 rpm.