A Novel Electrodynamic Reaction Sphere Prototype for Spacecraft Attitude Control

This paper proposes an aerostatic-bearing supported electrodynamic reaction sphere prototype for ground experiments to validate the technical feasibility of the electrodynamic reaction sphere functioning as an alternative actuator for the spacecraft attitude control system. First, the detailed prototype configuration is introduced and the main structural parameters are designed utilizing the derived analytical electromagnetic torque model. Then a simple but effective measuring scheme and a calculation algorithm based on mouse optical sensors are proposed for the omnidirectional rotation speed measurement of the spherical rotor. Moreover, the special electromagnetic dynamic distortion effect (EDDE) induced by the rapid omnidirectional rotation of the spherical rotor is originally modeled and analyzed by means of the finite-element method (FEM) and the superposition principle. And a current distribution algorithm based on the EDDE coupling torque model is presented to handle the strong torque coupling brought about by omnidirectional rotation. Finally, the proposed models and algorithms are experimentally verified on the developed laboratory prototype. And the closed-loop omnidirectional rotation control at a speed up to 1500 r/min is achieved which validates the feasibility of the electrodynamic reaction sphere.