Using AQM for Performance Improvement of Networked Control Systems

This paper presents a new scheme to jointly control the plant and the network to improve the overall performance of the networked control system (NCS). Using an analytical transmission control protocol (TCP) model for the network, an active queue management (AQM) is designed to achieve desired queue length. This leads to keeping network induced delay and its variation to be small enough to improve the overall performance of the NCSs. By augmenting the TCP communication model with the control system equations, the closed loop system is transformed to a state-dependent delay differential equation (SDDDE). Then using the Lyapunov-Krasovskii method, a sufficient condition for the stability of this class of systems is presented in terms of linear matrix inequality (LMI). Simulation results are presented and compared to some other methods, the superiority of the proposed approach is shown.