Design of unbiased functional observers for interconnected discrete-time delay systems

This paper proposes a method of designing an unbiased functional observer for each subsystem of a large scale delay discrete-time system. The method uses a rewriting of the observation error to avoid the constraint (due to the interconnection terms) that generally arises in observer design for these systems. The approach that we use to express the observation error permits to use results on stabilization of large scale delay discrete-time systems to solve the problem. The proposed observers are free of the interconnection terms and the observation error are unbiased. Each observer gain is parameterized via a single gain matrix which is computed via LMI. A tractable algorithm permits to compute the proposed observer easily.