Forming Distributed State Estimation Network From Decentralized Estimators

In this paper, we focus on the distributed state estimation of nonlinear systems comprised of several subsystems. We assume that a decentralized state estimation system already exists for the nonlinear system, where the local estimators can be of different types. In order to achieve improved estimation performance, the existing decentralized estimators may be connected together via a communication network to form a distributed state estimation network. We propose a systematic approach to take advantage of the existing decentralized estimators potentially of different types to form a distributed state estimation network without performing a complete redesign of the estimation system. Specifically, a compensator is designed for each subsystem, and is connected to the corresponding decentralized estimator to obtain an augmented estimator (AE). The AEs for the subsystems communicate with each other to exchange subsystem state estimates and measurements via a communication network every sampling time. We derive sufficient conditions on the convergence and boundedness of the estimation error of the proposed distributed estimation network. The proposed approach is demonstrated via the application to two chemical process examples and one hybrid tank plant.