Adaptive Fault-Tolerant Attitude Consensus for Multispacecraft Systems Under Digraphs via Distributed Observers

The leader-following attitude consensus is investigated for multiple spacecraft with actuator faults, uncertain inertia parameters, and external disturbances. In view of the scenario that only several spacecraft directly interact with the leader, distributed higher order sliding-mode observers are first proposed for every follower to estimate leader's states under a directed interaction network. Then an adaptive fault-tolerant attitude tracking controller is constructed such that every follower tracks the estimates of the leader's attitude and angular velocity. It is proven that the estimation errors of the observers approach the origin globally and exponentially. Besides, the tracking errors of each follower's attitude and angular velocity relative to the estimates of the leader's attitude and angular velocity converge to the origin asymptotically. Therefore, the objective that the attitudes of all followers synchronize with the leader's attitude asymptotically is fulfilled.