Observer-based finite time control for spacecraft attitude stabilization

A novel time-varying sliding mode control based finite-time controller incorporated a modified second-order disturbances observer/differentiator is proposed for a rigid spacecraft attitude stabilization control system. Firstly, a modified observer is designed to estimate the time-varying sliding mode manifold and the combined disturbances caused by external disturbances, spacecraft inertia uncertainties and actuator misalignments. Then based the estimated values derived from the observer, a finite-time controller and an adaptive law for the time-varying variable gain are presented, and Lyapunov stability analysis shows that finite-time convergence of the uncertain spacecraft attitude control system to the equilibrium point can be accomplished with great robustness to disturbances and uncertainties. Numerical simulation results for the orbiting rigid spacecraft model show fine performance, which validates the effectiveness and feasibility of the proposed scheme.