Distributed functional interval observers for nonlinear interconnected systems with time-delays and additive disturbances

In this article, a novel distributed functional interval observer design method is developed for nonlinear interconnected time-delay systems with additive disturbances in the outputs. The traditional distributed functional state observer is replaced by two distributed ones corresponding to two bounds (upper and lower bound) of functions of the state variables which need to be estimated. The structures of the functional interval observer for each subsystem are first proposed and then existence conditions are provided and formulated in terms of linear programmings (LPs). Finally, three examples are provided to illustrate the feasibility of the propounded theories.