Control barrier function-based fixed-time spacecraft attitude control under pointing constraints

This paper investigates the optimal spacecraft reorientation issue while adhering to attitude pointing and actuator constraints. To handle the second-order nature of the pointing constraint in the attitude dynamics, a high-order control barrier function (HOCBF) is developed, ensuring forward invariance of the pointing constraint set via Lyapunov-like conditions. A fixed-time stability (FxTS) Lyapunov function is introduced to achieve fixed-time reorientation using sliding mode techniques. The problem is formulated as a quadratic programming (QP) optimisation with actuator limits, leveraging slack variables to ensure feasibility. Numerical simulations validate the effectiveness of the proposed control strategy.