Saturated attitude control for rigid spacecraft under attitude constraints

This paper addresses the attitude-maneuver control problem for a rigid-body spacecraft in the presence of attitude-constrained zones as well as input saturation. More specifically, attitude-constrained zones are properly encoded, and an admissible artificial potential function (APF) is developed under the unit-quaternion representation. The elaborately designed APF ensures a unique minimum without requiring convexity of constrained zones, which yields a less stringent condition from previous approaches. Benefiting from the bounded property of the gradient of the proposed APF, a saturated controller is presented to render the almost uniformly ultimate boundedness of maneuver errors while complying with underlying maneuver constraints. The associated stability analysis of the closed-loop system is ensured by using the primal Lyapunov and the dual Lyapunov techniques. Numerical simulation tests are presented to assess the efficiency and demonstrate the advantages of the proposed control scheme.