Şahan, Gökhan
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Sahan, G
Sahan, Gokhan
Sahan, Gökhan
Şahan, G.
Şahan, G
Sahan, G.
Sahan, Gokhan
Sahan, Gökhan
Şahan, G.
Şahan, G
Sahan, G.
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Email Address
gsahan@iyte.edu.tr
Main Affiliation
04.02. Department of Mathematics
Status
Current Staff
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Sustainable Development Goals
SDG data is not available
Documents
11
Citations
57
h-index
5
Documents
11
Citations
55
Scholarly Output
11
Articles
8
Views / Downloads
49841/2599
Supervised MSc Theses
0
Supervised PhD Theses
0
WoS Citation Count
51
Scopus Citation Count
53
Patents
0
Projects
1
WoS Citations per Publication
4.64
Scopus Citations per Publication
4.82
Open Access Source
5
Supervised Theses
0
| Journal | Count |
|---|---|
| Systems and Control Letters | 2 |
| European Journal of Control | 2 |
| IEEE Transactions on Automatic Control | 1 |
| IFAC - PapersOnLine | 1 |
| Journal of The Franklin Institute-Engineering and Applied Mathematics | 1 |
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11 results
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Now showing 1 - 10 of 11
Article Citation - WoS: 7Citation - Scopus: 7Structure and Stability of Bimodal Systems in R-3: Part 1(Azerbaijan National Academy of Sciences, 2014) Eldem, Vasfi; Şahan, GökhanIn this paper, the structure and global asymptotic stability of bimodal systems in R3 are investigated under a set of assumptions which simplify the geometric structure. It is basically shown that one of the assumptions being used reduces the stability problem in R3 to the stability problem in R2. However, structural analysis shows that the behavior of the trajectories changes radically upon the change of the parameters of individual subsystems. The approach taken is based on the classification of the trajectories of bimodal systems as i) the trajectories which change modes finite number of times as t ? ?, and ii) the trajectories which change modes infinite number of times as t ? ?. Finally, it is noted that this approach can be used without some of the assumptions for all bimodal systems in R3, and for bimodal systems in Rn. © 2014, Azerbaijan National Academy of Sciences. All rights reserved.Article Relaxation of Conditions of Lyapunov Functions(2021) Şahan, GökhanIn this study, stability conditions are given for nonlinear time varying systems using the classical Lyapunov 2nd Method and its arguments. A novel approach is utilized and so that uniform stability can also be proved by using an unclassical Lyapunov Function. In contrast with the studies in the literature, Lyapunov Function is allowed to be negative definite and increasing through the system. To construct a classical Lyapunov Function, we use a reverse time approach methodology for the intervals where the unclassical one is increasing. So we prove the stability using a new Lyapunov Function construction methodology. The main result shows that the existence of such a function guarantees the stability of the origin. Some numerical examples are also given to demonstrate the efficiency of the method we use.Article Citation - WoS: 12Citation - Scopus: 12Uniform Asymptotic and Input To State Stability by Indefinite Lyapunov Functions(Elsevier, 2024) Sahan, Gokhan; Ozdemir, DeryaIn this work, we study uniform, uniform asymptotic, and input -to -state stability conditions for nonlinear timevarying systems. We introduce an easily verifiable condition for uniform attractivity by utilizing an indefinite sign upper bound for the derivative of the Lyapunov function. With this bounding structure, we propose novel conditions that enable us to test uniform stability, uniform asymptotic stability, and ISS, easily. As a result, the constraints on the coefficients of the bound that identify uniformity for stability and attractivity, and many of the available conditions have been relaxed. The results are also used for the perturbation problem of uniformly stable and uniformly asymptotically stable linear time -varying systems. Consequently, we demonstrate that uniform asymptotic stability of nonlinear time -varying systems can be robust for perturbations, but with special time -varying coefficients.Editorial Comments on “Relaxed Conditions for the Input-to-State Stability of Switched Nonlinear Time-Varying Systems”(Ieee-inst Electrical Electronics Engineers inc, 2025) Sahan, Gokhan; Trenn, StephanThis study addresses the deficiencies in the assumptions of the results in (Chen and Yang, 2017) due to the lack of uniformity. We first show the missing hypothesis by presenting a counterexample. Then, we prove why they are wrong in that form and show the errors in the proof of the main result of (Chen and Yang, 2017). Next, we compare the assumptions and related results of (Chen and Yang, 2017) with similar works in the literature. Lastly, we give suggestions to complement the shortcomings of the hypotheses and thus correct them.Article Citation - WoS: 8Citation - Scopus: 7Exponential Stability and Boundedness of Nonlinear Perturbed Systems by Unbounded Perturbation Terms(Elsevier, 2023) Şahan, GökhanWe study the exponential stability and boundedness problem for perturbed nonlinear time-varying systems using Lyapunov Functions with indefinite derivatives. As the limiting function for the perturbation term, we use different forms and give stability and boundedness conditions in terms of the coefficients in these bounds. Contrary to most of the available conditions, we allow the coefficients to be unbounded. But instead, we put forward a condition that requires a series produced by coefficients to be limited and exponentially decaying. We perform our results on Linear time-varying systems and generalize many of the available results. & COPY; 2023 The Franklin Institute. Published by Elsevier Inc. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 2Well Posedness Conditions for Planar Conewise Linear Systems(SAGE Publications Inc., 2019) Şahan, Gökhan; Eldem, VasfiIn this study, we give well-posedness conditions for planar conewise linear systems where the vector field is not necessarily continuous. It is further shown that, for a certain class of planar conewise linear systems, well posedness is independent of the conic partition of R-2. More specifically, the system is well posed for any conic partition of R-2.Conference Object Existence and Uniqueness of Solution for Discontinuous Conewise Linear Systems(Elsevier, 2020) Şahan, GökhanIn this study, we give necessary and sufficient conditions for well posedness of Conewise Linear Systems in 3-dimensional space where the vector field is allowed to be discontinuous. The conditions are stated using the subspaces derived from subsystem matrices and the results are compared with the existing conditions given in the literature. We show that even we don't have a fixed structure on system matrices as in bimodal systems, similar subspaces and numbers again determines well posedness. Copyright (C) 2020 The Authors.Article Citation - WoS: 6Citation - Scopus: 6Well Posedness Conditions for Bimodal Piecewise Affine Systems(Elsevier Ltd., 2015) Şahan, Gökhan; Eldem, VasfiThis paper considers well-posedness (the existence and uniqueness of the solutions) of Bimodal Piecewise Affine Systems in ℝn. It is assumed that both modes are observable, but only one of the modes is in observable canonical form. This allows the vector field to be discontinuous when the trajectories change mode. Necessary and sufficient conditions for well-posedness are given as a set of algebraic conditions and sign inequalities. It is shown that these conditions induce a joint structure for the system matrices of the two modes. This structure can be used for the classification of well-posed bimodal piecewise affine systems. Furthermore, it is also shown that, under certain conditions, well-posed Bimodal Piecewise Affine Systems in ℝn may have one or two equilibrium points or no equilibrium points.Conference Object Citation - WoS: 1Citation - Scopus: 4Uniform Asymptotic Stability by Indefinite Lyapunov Functions(IEEE, 2022) Sahan, Gokhan; Ozdemir, DeryaIn this work, we consider Uniform Asymptotic Stability (UAS) of nonlinear time-varying systems. We utilize an indefinite signed polynomial of Lyapunov Function (LF) for the upper bound of the derivative of LF. This special bound is especially useful for perturbation problems. Compared to the ones in the literature we improve the upper bound of the LF and its related properties. Since UAS is the first step for input to state stability (ISS) and integral ISS, it should be thought that these improvements will give rise to new advances in real-world applications as well.Article Citation - WoS: 3Citation - Scopus: 3The Effect of Coupling Conditions on the Stability of Bimodal Systems in R3(Elsevier Ltd., 2016) Eldem, Vasfi; Şahan, GökhanThis paper investigates the global asymptotic stability of a class of bimodal piecewise linear systems in R3. The approach taken allows the vector field to be discontinuous on the switching plane. In this framework, verifiable necessary and sufficient conditions are proposed for global asymptotic stability of bimodal systems being considered. It is further shown that the way the subsystems are coupled on the switching plane plays a crucial role on global asymptotic stability. Along this line, it is demonstrated that a constant (which is called the coupling constant in the paper) can be changed without changing the eigenvalues of subsystems and this change can make bimodal system stable or unstable.