Output feedback control of relative spacecraft attitude

In this paper we present a controller-observer scheme for relative spacecraft attitude control. The system of interest is a leader-follower formation, where we assume that the leader is controlled by some stable controller and we want the follower to track the attitude of the leader. Furthermore we assume that only the relative attitude is available for control purposes, and to estimate the relative angular velocity we introduce an error observer. The resulting closed-loop system is proved to be uniformly practically asymptotically stable to a ball centered at the origin.