Distributed adaptive output consensus tracking of higher-order systems with unknown control directions

This paper investigates the distributed adaptive output consensus tracking problem of higher-order subsystems with unknown control directions and unknown dynamic parameters. Only a subset of the subsystems is given access to the desired trajectory information directly, and the subsystems are connected through an undirected and connected graph with a time-invariant topology. A distributed adaptive controller is deduced using the backstepping technique and a Nussbaum-type function to drive all the subsystems to track the desired trajectory asymptotically. Moreover, these controllers are distributed in the sense that the controller design for each subsystem only requires relative state information between itself and its neighbors. It is proven that the output tracking error converges to zero asymptotically and that all the closed-loop system signals are bounded. A simulation is carried out to demonstrate the effectiveness of the proposed control scheme.