Global sliding mode control based on observer for TCP network

The problem of network congestion control is studied for a class of TCP network systems with state delay and external disturbance. Because the state of the system is not fully measurable, the state observer is designed. The sufficient conditions for the robust stability of the error system is given based on linear matrix inequality (LMI) and Lyapunov stability theory. According to the reaching condition of sliding mode control theory, the global sliding mode controller is designed. Global sliding mode control is used to eliminates the reaching phase of the sliding mode control and ensure the robustness of the whole control process. The simulation results show that the proposed algorithm has good robustness and the instantaneous queue length can converge to the expected queue length effectively.