  A network of agents, modeled by a class of wave PDEs, is under investigation.
One agent in the network plays the role of a leader, and all the remaining
"follower" agents are required to asymptotically track the state of the leader.
Only boundary sensing of the agent's state is assumed, and each agent is
controlled through the boundary by Neumann-type actuation. A linear interaction
protocol is proposed and analyzed by means of a Lyapunov-based approach. A
simple set of tuning rules, guaranteeing the exponential achievement of
synchronization, is obtained. In addition, an exponential ISS relation,
characterizing the effects on the tracking accuracy of boundary and in-domain
disturbances, is derived for the closed loop system.
