Specified-time adaptive attitude tracking control for spacecraft with guaranteed prescribed performance

To address the spacecraft attitude tracking control problem under external disturbances and inertial uncertainties, a specified-time adaptive guaranteed-performance control scheme is proposed. First, the attitude kinematics, dynamics, and tracking error models are established based on the modified Rodrigues parameters. By transforming the constrained tracking problem into an unconstrained one via monotonic preset performance and error transformation functions, a quantitative mapping is established among user-tunable performance indices (steady-state accuracy, convergence time, and overshoot). Furthermore, an exponential-polynomial combined time-varying gain function is designed to ensure a smooth transition of the system state from the transient to the steady-state phase, thereby avoiding non-smooth behaviors caused by control law switching. On this basis, an adaptive fuzzy guaranteed performance controller is developed to ensure that the attitude tracking error converges to a neighborhood of the origin within the prescribed time and strictly satisfies the preset performance constraints. Based on Lyapunov stability theory, it is proven that all signals in the closed-loop system are uniformly ultimately bounded, and the effectiveness and engineering applicability of the proposed strategy are verified through numerical simulations.