The Decentralized Control Expanding System Problem

Suppose a controlled system denoted by Sold exists with the property that robust tracking and regulation occurs in each of the system's local control agents. We wish to examine the conditions under which a new subsystem and a new set of local control agents denoted by Snew can be connected to Sold' so that the new outputs and previous outputs are regulated, without the need for retuning the original control agents. This problem is a generalizaiton of the results obtained in [3] which deals with the case when the control agents of Snew are centralized.