Browsing by Author "Özbay, Hitay"
Now showing items 1-20 of 121
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Analysis of a gene regulatory network model with time delay using the secant condition
Ahsen, M. E.; Özbay, Hitay; Nicolescu, Silviu-Iulian (IEEE, 2016-10-04)A cyclic model for gene regulatory networks with time delayed negative feedback is analyzed using an extension of the so-called secant condition, which is originally developed for systems without time delays. It is shown ... -
Analysis of blood cell production under growth factors switching
Djema, W.; Özbay, Hitay; Bonnet, C.; Fridman, E.; Mazenc, F.; Clairambault, J. (Elsevier B.V., 2017)Hematopoiesis is a highly complicated biological phenomenon. Improving its mathematical modeling and analysis are essential steps towards consolidating the common knowledge about mechanisms behind blood cells production. ... -
Analysis of deterministic cyclic gene regulatory network models with delays
Ahsen, M. E.; Özbay, Hitay; Niculescu, S. -I. (Springer Publishing Company, 2015)This brief examines a deterministic, ODE-based model for gene regulatory networks (GRN) that incorporates nonlinearities and time-delayed feedback. An introductory chapter provides some insights into molecular biology and ... -
Comparing PI controllers for delay models of TCP/AQM networks
Ünal H.U.; Melchor-Aguilar, D.; Üstebay, D.; Niculescu, S.-I.; Özbay, Hitay (Elsevier, 2010)In this paper, ns-2 simulations and related comparisons of four different PI controllers designed for TCP/AQM networks will be presented. The simulations are performed for various scenarios. © 2010 IFAC. -
Comparison of PI controllers designed for the delay model of TCP/AQM networks
Ünal H. U.; Melchor-Aguilar, D.; Üstebay, D.; Niculescu, S. -I.; Özbay, Hitay (Elsevier, 2013)One of the major problems of communication networks is congestion. In order to address this problem in TCP/IP networks, Active Queue Management (AQM) scheme is recommended. AQM aims to minimize the congestion by regulating ... -
Computation of H∞ controllers for infinite dimensional plants using numerical linear algebra
Özbay, Hitay (John Wiley & Sons, 2012-02-14)The mixed sensitivity minimization problem is revisited for a class of single-input-single-output unstable infinite dimensional plants with low order weights. It is shown that H∞ controllers can be computed from the ... -
Computation of optimal H∞ controllers and Approximations of fractional order systems: A tutorial review
Karagül, A. E.; Demir, O.; Özbay, Hitay (Applied Mathematics Scientific Research Institute, 2013)This paper briefly reviews the recent techniques in the field of fractional order systems, and concentrates on the design of 'H00 optimal controllers for a magnetic suspension system model, derived in (25). The plant ... -
Control of subsonic cavity flows by neural networks-analytical models and experimental validation
Efe, M. Ö.; Debiasi, M.; Yan, P.; Özbay, Hitay; Samimy, M. (American Institute of Aeronautics and Astronautics, 2005)Flow control is attracting an increasing attention of researchers from a wide spectrum of specialties because of its interdisciplinary nature and the associated challenges. One of the main goals of The Collaborative Center ... -
Controller design for delay margin improvement
Gündeş, A. N.; Özbay, Hitay (IEEE, 2019)Two important design objectives in feedback control are steady-state error minimization and delay margin maximization. In general these two objectives work against each other. This paper starts with an initial controller ... -
Controller design for plants with internal delayed feedback
Gündeş, A. N.; Özbay, Hitay (IEEE, 2021-06-14)A special class of retarded and neutral time delay systems is considered: These are plants with internal delayed feedback, and they may have finitely many or infinitely many unstable poles. Stabilizing controllers are ... -
Controller redesign for delay margin improvement
Gündeş, A. N.; Özbay, Hitay (Elsevier, 2020-01)Two important design objectives in feedback control are steady-state error minimization and delaymargin maximization. For many practical systems it is not possible to have infinite delay margin andzero steady state error ... -
A coupled model for healthy and cancerous cells dynamics in Acute Myeloid Leukemia
Avila, J. L.; Bonnet, C.; Özbay, Hitay; Clairambault, J.; Niculescu, S. I.; Hirsch, P.; Delhommeau, F. (IFAC, 2014)In this paper we propose a coupled model for healthy and cancerous cell dynamics in Acute Myeloid Leukemia. The PDE-based model is transformed to a nonlinear distributed delay system. For an equilibrium point of interest, ... -
Decentralised robust flow controller design for networks with multiple bottlenecks
Munyas, I.; Yelbaşi, Ö.; Biberovic, E.; İftar, A.; Özbay, Hitay (Taylor & Francis, 2009)Decentralised rate-based flow controller design in multi-bottleneck data-communication networks is considered. An H∞ problem is formulated to find decentralised controllers which can be implemented locally at the bottleneck ... -
Delay margin optimization for systems with ınternal delayed feedback
Özbay, Hitay (Elsevier, 2021-07-16)In this brief paper, controller design for delay margin optimization is considered for systems with internal feedback delays (systems with delays in the state variables). Similar to existing results on delay margin ... -
Design and trajectory tracking control of a piezoelectric nano-manipulator with actuator saturations
Liu, P.; Yan, P.; Özbay, Hitay (Academic Press, 2018)This paper presents the design of an XYZ nano-manipulator as well as the model based high precision tracking control of the nano-manipulating system. Aiming at large range and high mechanical bandwidth, the proposed ... -
Design of a switched robust control scheme for drug delivery in blood pressure regulation
Ahmed, S.; Özbay, Hitay (Elsevier B.V., 2016)A control algorithm based on switching robust controllers is presented for a Linear Parameter Varying (LPV) time-delay system modeling automatic infusion of vasodilator drug to regulate postsurgical hypertension. The system ... -
Dwell time optimization in switching control of parameter varying time delay systems
Yan, P.; Özbay, Hitay; Şansal, M. (IEEE, 2011)It has been shown that parameter varying systems with time delays can be robustly stabilized by switching control, provided that the plant's parameter varies slowly enough such that the dwell time conditions of the switched ... -
Dwell time-based stabilisation of switched delay systems using free-weighting matrices
Koru, A. T.; Delibaşı, A.; Özbay, Hitay (Taylor and Francis, 2018)In this paper, we present a quasi-convex optimisation method to minimise an upper bound of the dwell time for stability of switched delay systems. Piecewise Lyapunov-Krasovskii functionals are introduced and the upper bound ... -
Dwell time-based stabilisation of switched linear delay systems using clock-dependent Lyapunov-Krasovskii functionals
Koru, A. T.; Delibaşı, A.; Özbay, Hitay (Taylor and Francis, 2018)Dwell time stability conditions of the switched delay systems are derived using multiple clock-dependent Lyapunov-Krasovskii functionals. The corresponding conditions are approximated by both using piecewise linear functions ... -
Dwell time-based stabilisation of switched linear delay systems using clock-dependent Lyapunov–Krasovskii functionals
Koru, A. T.; Delibaşı, A.; Özbay, Hitay (Taylor and Francis, 2020)Dwell time stability conditions of the switched delay systems are derived using multiple clock-dependent Lyapunov–Krasovskii functionals. The corresponding conditions are approximated by both using piecewise linear functions ...