Robust-control using model-error-feedback CDOB and DOB under variable-time-delay

This paper presents the robustness improvement of the Communication-Disturbance-OBserver (CDOB) based on Lyapunov-Krasovskii functional(LKF), and proposes the Network-based-Control-System (NCS) using the LKF based CDOB and a local-side DOB. The CDOB is a compensation method for a output signal includes a communication delay. By using LKF, a steady-state output-estimation-error of the CDOB under variable time-delay and parameter-perturbations is suppressed. However, the latest studies have not shown the robustness to the disturbance-input. In this paper, the frequency- weight of CDOB to the disturbance is introduced to the design of the LKF based CDOB, to suppress the error. From a calculated error-characteristic and a numerical simulation, the account of the weight is validated. Additionally, implementing a disturbance observer in the local (controlled object) side, the robustness of the NCS is improved much in the numerical simulation.