Decentralized disturbance attenuating control for large-scale nonlinear interconnected systems

A global decentralized robust adaptive output-feedback dynamic compensator is proposed for stabilization, tracking and disturbance attenuation of the decentralized generalized output-feedback canonical form representing the largest class for which decentralized robust adaptive output-feedback tracking and disturbance attenuation results are currently available. The system may contain unknown parameters multiplying output-dependent nonlinearities and unknown nonlinearities satisfying certain bounds. Under certain assumptions, it is shown that reduced-order observers and backstepping controllers can be designed to achieve practical stabilization of the tracking error in each subsystem in the presence of bounded disturbance inputs. Sufficient conditions under which asymptotic tracking and stabilization can be achieved are derived. Signal gains from the disturbance inputs to the tracking errors are presented in the input-to-output-practical-stability and integral-input-to-output-practical-stability frameworks. A particular case in which the standard L₂-gain disturbance attenuation is achieved is also provided.