${\cal H}_{\infty}$ Almost Output Synchronization for Heterogeneous Networks Without Exchange of Controller States

We consider the H
_∞
almost output synchronization and regulated output synchronization problem for heterogeneous directed networks with external disturbances where agents are introspective (i.e., agents have access to a part of their own states). A decentralized protocol is designed for each agent, without exchanging internal controller states with neighboring agents, to achieve output synchronization and regulated output synchronization while making the H
_∞
norm from the disturbances to the synchronization errors in the network arbitrarily small. Furthermore, the idea for output synchronization is applied to a formation problem in the presence of disturbances. The method is illustrated by simulation examples.