Fully Actuated System Approach for 6DOF Spacecraft Control Based on Extended State Observer

This paper deals with the problem of position and attitude tracking control for a rigid spacecraft. A fully actuated system (FAS) model for the six degree-of-freedom (6DOF) spacecraft motion is derived first from the state-space model by variable elimination. Considering the uncertainties from external disturbance, unknown motion information, and uncertain inertia properties, an extended state observer (ESO) is designed to estimate the total disturbance. Then, a tracking controller based on FAS approach is designed, and this makes the closed-loop system a constant linear one with an arbitrarily assignable eigenstructure. The solution to the parameter matrices of the observer and controller is given subsequently. It is proved via the Lyapunov stability theory that the observer errors and tracking errors both converge into the neighborhood of the origin. Finally, numerical simulation demonstrates the effectiveness of the proposed controller.