Leader-Following Almost Output Consensus for Linear Multi-Agent Systems with Disturbance-Affected Unstable Zero Dynamics

In this paper, we formulate and investigate the leader-following almost output consensus problem for linear multi-agent systems with disturbance affected unstable zero dynamics. Conditions on the communication topology, agent dynamics and the way the disturbances affect the zero dynamics are established under which low-and-high gain based consensus protocols are designed. These protocols are shown to achieve leader-following almost output consensus, that is, output consensus of the system can be achieved to an arbitrary level of accuracy with the states remain bounded in the absence of the disturbances, and when the system is operating in output consensus within the desired accuracy, the L-2-gain from the disturbances to the difference between each follower agent's output with and without the disturbances from the same initial condition can be made arbitrarily small.