Constrained attitude stabilization for rigid spacecraft with two internal torques using artificial potential function

This paper proposes a control algorithm for stabilizing an underactuated spacecraft with attitude-forbidden constraints. An unactuated axis of the angular velocity is determined by solving the dynamic equation under the assumption of zero angular momentum and relaxed into an inequality constraint of the Euler axis to identify the feasible attitude region for the underactuated system. Moreover, the forbidden pointing regions are established as cones in the inertial space inaccessible to the spacecraft attitude. Then, an artificial potential function- based control law is proposed to evade the hazardous zones while stabilizing the underactuated system to equilibrium. It is shown that the closed-loop system converges to the largest invariant set of the set of critical points by the LaSalle invariant set theorem. Finally, numerical simulations are conducted to corroborate the effectiveness and performance of the proposed control scheme.