Sharif Digital Repository

Beside the major objective of providing congestion control, achieving predictable queuing delay, maximizing link utilization, and robustness are the main objectives of an active queue management (AQM) controller. This paper proposes an improved queue dynamic model while incorporating the packet drop probability as well. By applying the improved model, a new compensated PID AQM controller is developed for Transmission Control Protocol/Internet Protocol (TCP/IP) networks. The non-minimum phase characteristic caused by Padé approximation of the network delay restricts the direct application of control methods because of the unstable internal dynamics. In this paper, a parameter-varying dynamic... 

When the network suffers from congestion, the core or edge routers signal the incidence of congestion through the active queue management (AQM) to the sources. The time-varying nature of the network dynamics and the complex process of retuning the current AQM algorithms for different operating points necessitate the development of a new AQM algorithm. Since the non-minimum phase characteristics of the network dynamics restrict direct application of the proportional-integral-derivative (PID) controller, we propose a compensated PID controller based on a new control strategy addressing the phase-lag and restrictions caused by the delay. Based on the unstable internal dynamics caused by the... 

The turbine control system is one of the key control loops in the dynamic performance of steam power generation units. In this paper a multivariable PID controller is designed for the governing system of steam turbine power generators. The necessary and sufficient conditions for existence of a strong robust H ∞ dynamic compensator are established in terms of linear matrix inequality (LMI) approach. This controller is designed in succeeding to the existing proportional controller in a power plant. To reach to this goal, the complete dynamic model of an actual turbine-generator including the governor, turbine and generator, are derived. Simulation results show that proposed controller has good...