Robust decentralized PI observer for linear interconnected systems

This paper considers the problem of designing a decentralized PI observer with prescribed degree of convergence for a set of interconnected systems. Under the assumption of linear interactions, we provide a direct design procedure for the PI observer which can effectively be used in disturbance estimation and observer-based control design enhancing the robustness properties. In this connection we also extend the results to the case of designing controllers that attenuate the disturbance while preserving the stability. It is shown that the design can be formulated in terms of LMI which efficiently solve the problem. The design process requires a suitable modification of a decentralized PI observer design comprised of a set of local PI observers for the decoupled subsystems. The modification ensures a desired convergence rate for the overall PI observer and generally involves the use of additional inputs, which account for the interconnection effects, into the local PI observers.