Output synchronization of uncertain nonlinear multi-agent systems with relative degree one

In this paper, we address the problem of controlled output synchronization of uncertain, nonlinear agents with relative degree one. Under the additional assumption that all agents are weakly minimum phase, it is well known that the agents are then feedback equivalent to a passive system. This feedback equivalence has been exploited by [1] to deal with output synchronization on strongly connected graphs, and in the presence of time delays. We exploit this feedback equivalence in this paper to develop adaptive control laws in order to generalize the aforementioned results to achieve output synchronization even in the presence of uncertain agent dynamics. Furthermore, we show that the main results also hold true for the practical case when there are constant time delays in the communication. The results are finally illustrated by a numerical example.