Nonlinear robust H∞ control via a stable decentralized nonlinear output feedback controller

This paper presents a procedure to solve a decentralized robust H^∞ control problem for a nonlinear uncertain system. The admissible uncertainties and nonlinearities of the system satisfy Integral Quadratic Constraints and Global Lipschitz Conditions, respectively. The decentralized controller is required to be stable and is constructed by exploiting the interconnections between subsystems without treating them as uncertainties. Instead, additional uncertainties are introduced due to the discrepancies between each local controller and the full nonlinear output feedback controller. The solution to this problem involves the solutions of Algebraic Riccati Equations. Also, the closed loop system is required to be absolutely stabilized with a specified disturbance attenuation level.