Constrained velocity-free control of spacecraft attitude via explicit reference governor

Abstract: This paper introduces an explicit reference governor-based control scheme tailored for addressing the velocity-free spacecraft attitude maneuver problem. This problem is subject to specific constraints, namely the pointing constraint, angular velocity constraint, and input saturation. The proposed control scheme operates in two layers, ensuring the asymptotic stability of the spacecraft's attitude while adhering to the aforementioned constraints. The inner layer employs output feedback control utilizing an angular velocity observer based on immersion and invariance technology. This observer facilitates attitude stabilization without the measurement of angular velocity. Through an analysis of the geometry associated with the pointing constraint, determination of the upper bound of angular velocity, and optimization of the control input solution, the reference layer establishes a safety boundary described by the invariant set. Additionally, we introduce the dynamic factor related to the angular velocity estimation error into the invariant set to prevent states from exceeding the constraint set due to unmeasurable angular velocity information. The shortest guidance path is then designed in the reference layer. Finally, we substantiate the efficacy of the proposed constrained attitude control algorithm through numerical simulations.