Unit quaternion-based output feedback control for leader-following attitude consensus of multiple rigid spacecraft systems

In this paper, we study the leader-following attitude consensus problem for multiple rigid spacecraft systems by a distributed unit quaternion-based output feedback control law. The control law is based on the certainty equivalence principle and contains a distributed observer for estimating the state of the leader and an auxiliary system compensating for the unavailability of the angular velocity. It is shown that the problem is solvable under the standard assumption that each follower can access the information from the leader through a directed path.