Decentralized PI observer-based control of nonlinear interconnected systems with disturbance attenuation

We consider the problem of designing decentralized PI observer-based controller for nonlinear interconnected systems using linear matrix inequalities (LMIs). The overall system is composed of linear subsystems and nonlinear time-varying interconnections depending on both time and state. We take advantage of additional degrees of freedom in PI observer to maximize the bound on nonlinear interconnection terms. Also we extend the original problem of robust stabilization by including a disturbance term and provide a sufficient condition for connective stability with disturbance attenuation in the L₂ gam sense. An example is included to validate the theoretical results.