Spacecraft Close-range Position Tracking Control via System Uncertainty Observer

In this paper, the nonsingular fast terminal sliding mode control for spacecraft close-range position system is investigated with model uncertainty and external disturbances. First, a system uncertainty linear observer is employed to estimate and compensate for the system uncertainty. Second, based on the nonsingular fast terminal sliding mode surface, the position tracking control law with unmeasured velocity is proposed which not only eliminates the chattering phenomenon but also guarantees the tracking errors of the system converge in finite time. Finally, through the simulation results, the effectiveness of the proposed control law is demonstrated.