Robust mixed control of networked control systems with random time delays in both forward and backward communication links

This paper is concerned with the two-mode-dependent robust control synthesis of networked control systems where random delays existing in both forward controller-to-actuator (C–A) and feedback sensor-to-controller (S–C) communication links are modeled as Markov chains. The output feedback controller is designed to depend on the current S–C delay and the previous C–A delay. Then, the closed-loop system is formulated as a special jump linear system. The generalized definitions of the H 2 and H ∞ norms for such underlying special systems are proposed. Further, the two-mode-dependent robust H 2 and robust mixed H 2 / H ∞ control design methods for NCSs are developed. The design examples illustrate the effectiveness of the proposed methods.