Some issues in decentralized control of nonlinear systems

The authors present two results on controlling nonlinear systems via decentralized feedback. They begin with a method for observing the system state at a particular input/output port by closing the loop with output feedback at the other input/output ports. The conditions for observing the state with linearized error dynamics are met by choosing the output feedback functions to satisfy the local observability conditions. They also examined a system with nonlinear subsystems and nonlinear interconnections. For this class of systems, a local feedback linearizing controller is proposed, and a linear state feedback law which compensates for the interconnections resulting in exponential stability of the system is given