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Active queue management with discrete sliding modes in TCP networks

Ignaciuk P., Karbowańczyk M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2014

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Vol. 62, nr 4

701--711

EN

In this paper, a new active queue management (AQM) algorithm for data traffic control in TCP/IP networks is developed. The algorithm design is based on the principles of discrete sliding-mode control. Unlike majority of earlier studies, the design procedure considers the effects of both non-negligible delay in transferring data and feedback information and unpredictable capacity variations. The switching function is selected to incorporate a delay compensation mechanism, which ensures efficient network operation even for large bandwidthdelay product connections. The proposed algorithm, implemented as a packet marking scheme, is tested in discrete event ns-2 simulator. The results show that the algorithm provides fast convergence to steady state after sudden, unanticipated capacity changes. By generating smaller overshoots, the proposed algorithm also allows for reducing buffer space requirements to avoid packet loss as compared to the benchmark AQM solutions.

2

Dead-beat and reaching-law-based sliding-mode control of perishable inventory systems

Ignaciuk P., Bartoszewicz A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2011

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Vol. 59, nr 1

39-49

EN

In this paper we consider the problem of efficient control of inventory systems with perishable goods. In the analyzed setting the deteriorating stock at a distribution center used to fulfill unknown, time-varying demand is replenished with delay from a supply source. The challenging issue is to achieve the high service level with minimum costs when the replenishment orders are procured with lead-time delay spanning multiple review periods. On the contrary to the typical heuristic approaches, we apply formal methodology based on discrete-time sliding-mode (SM) control. The proposed SM controller with the sliding plane selected for a dead-beat scheme ensures that the maximum service level is obtained in the system with arbitrary delay and any bounded demand pattern. In order to account for the supplier capacity limitations in the systems with input constraints, we also develop an alternative control strategy based on reaching law. Both controllers achieve a given service level with smaller holding costs and reduced order-to-demand variance ratio as compared to the classical order-up-to policy.

3

Discrete-time control systems on homogeneous spaces: partition property

Jordan J.

Control and Cybernetics

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2006

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Vol. 35, no 4

863-871

EN

If the system semigroup of a control system is a roup, the system has the partition property, i.e., the reachable sets form a disjoint partition in the state space. The converse is ot true in general. In this work we give sufficient conditions for le partition property for a family of discrete-time control systems on homogeneous spaces. We apply our results to Inverse Iteration systems on flag manifolds, which are closely related to numerical aIgorithms.

4

An improved model of delay-locked loop in the z-domain

Orżanowski T.

Metrology and Measurement Systems

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2003

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Vol. 10, nr 3

309-318

EN

This paper presents an improved z-domain model of the delay-locked loop (DLL). This model describes more accurately the behavior and characteristics of the DLL than the commonly used s-domain models. Since DLL is a mixed-mode circuit, I show a transformation method of the continuous-time part of DLL from s-domain into z-domain. I derive the discrete-time transfer function of the DLL and define the stability conditions for some transfer functions of the loop filter. The z-domain DLL models described by other authors are also discussed.

PL

Artykuł przedstawia udoskonalony model dyskretny pętli DLL (Delay-locked loop) w dziedzinie z. Model ten dokładniej opisuje działanie i właściwości pętli niż stosowany powszechnie model w dziedzinie s. Ponieważ DLL jest układem mieszanym, zatem w artykule przedstawiono metodę transformacji części ciągłej pętli z dziedziny s do dziedziny z. Na podstawie nowego modelu w dziedzinie z wyprowadzono transmitancję dyskretną pętli DLL i dla dwóch transmitancji operatorowych filtru, podano warunki stabilności pętli. W artykule sa dyskutowane modele DLL w dziedzinie z opisane w literaturze.