“…In [11] it has been proved that a necessary and sufficient condition for output synchronization in heterogeneous networks is the internal model principle. This concept has been adapted and extended to the nonlinear case in [12] and has become the widely accepted technique to face the problem known in literature as cooperative output regulation. The key aspect of this D. Astolfi is with the Université de Lorraine, CRAN, UMR 7039, Nancy, France and the CRNS, CRAN, UMR 7039, Nancy, France, daniele.astolfi@univ-lorraine.fr approach is that the consensus trajectory can be thought as generated by an exosystem, whose model is known to all the agents in the network.…”