Reduced-order observer based decentralized controller design: The LMI approach

The robust stabilization problem is considered for a class of nonlinear interconnected systems consisting of linear subsystems coupled by nonlinear interconnections. The interconnections are unknown and quadratically bounded. A novel decentralized dynamic output feedback based linear controller is proposed, which is characterized by the observer-controller separation property. The feedback gain matrices of local controllers are obtained by solving an optimization problem subject to linear matrix inequalities. The local projection operator based reduced-order unknown input observer is employed to asymptotically estimate the states of each subsystem. The closed-loop system driven by the proposed decentralized controller is guaranteed to be connectively stable with maximized interconnection bounds.