Yeni bir PI ve PID kontrolü tasarımı methodu ve TCP akışları için AQM tasarımı uygulaması

PID controllers are continuing to be used in many control applications due totheir simple structures. Design of such controllers for unstable systems with timedelays is an active research area. Recently, stabilizing PI and PD controllers fora class of unstable MIMO (multi-input multi-output) systems with input/outputdelays have been investigated and allowable controller gain intervals for suchcontrollers have been maximized. Motivated by these studies, this thesis proposesa new method for tuning the parameters of PI, PD and PID controllers forintegrating processes with time delays. The method is based on selecting thecenters of the maximized gain intervals as the controller gains for the purposeof obtaining optimal controllers. As an application of this method, controllersfor AQM (Active Queue Management) of TCP (Transmission Control Protocol)flows have been designed. AQM is a congestion control method used in computernetworks to increase link utilization with less queueing delays. The fluid flowmodel of TCP?s congestion avoidance mode based on delay differential equationssupplies the mathematical background for modelling the AQM as a feedbackcontrol system and designing different control schemes accordingly. Firstly, theproposed controller design method has been applied to AQM for the case oftime invariant time delay and secondly the method has been supported withswitching control technique to obtain optimum system performance in the caseof time varying time delay. The performance of the designed controllers for bothcases has been illustrated by packet level simulations in ns-2.Keywords: PID control, time delay, Active Queue Management (AQM), switch-ing control, ns-2