Hamiltonian Structure-Based Robust Station-Keeping for Unstable Libration Point Orbits

In this work, a controller for spacecraft station-keeping in an unstable libration point orbit was designed based on the Hamiltonian structure of the system. The proposed controller exploits the inherent Hamiltonian structure of the system, and therefore the performance of the controller can be easily adjusted while ensuring the stability of the closed-loop system. A filtered extended high-gain observer was also designed to compensate for the performance degradation of the controller due to external disturbances and model uncertainty. The filtered extended high-gain observer includes an integral state feedback to alleviate navigation error amplification due to the high gain of the observer. The global convergence of the proposed observer was demonstrated, and the tracking error was ultimately bounded to the reference libration point orbit by applying the Hamiltonian structure-based controller. The performance of the proposed controller and observer was demonstrated by numerical simulation of the Earth-Moon system.