Yazar "Akgul, Akif" seçeneğine göre listele

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    A family of circulant megastable chaotic oscillators, its application for the detection of a feeble signal and PID controller for time-delay systems by using chaotic SCA algorithm
    (Pergamon-Elsevier Science Ltd, 2021) Rajagopal, Karthikeyan; Cimen, Murat Erhan; Jafari, Sajad; Singh, Jay Prakash; Roy, Binoy Krishna; Akmese, Omer Faruk; Akgul, Akif
    Chaotic systems with cyclic symmetry are very rare and have been less discussed in the literature. Similarly, megastable oscillators, which can have a finite or infinite number of coexisting attractors, have also attracted researchers. We propose a class of cyclic symmetry oscillators with the megastable property with infinite coexisting attractors for the first time in the literature. Various dynamical properties of the proposed oscillators are discussed in detail. An application for the detection of a feeble signal by using the proposed circulant megastable oscillator is presented. Since chaotic oscillators are highly sensitive to a tiny change in the parameters or an external input to the oscillator, this property of the proposed oscillator is used for the detection of a feeble signal. Simulated results validate the effectiveness of the proposed application. After that, a new chaotic Sine-Cosine Algorithm (SCA) is developed using the randomness of megastable oscillators. Subsequently, this new chaotic sine-cosine algorithm is used to determine the PID controller parameters of time-delay systems concerning the objective function. As a result, the proposed chaotic sine-cosine algorithm presents better performance for time-delay systems when compared with the available algorithms in the literature. (c) 2021 Elsevier Ltd. All rights reserved.
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    A New Chaotic Mixer Design Based on the Delta Robot and Its Experimental Studies
    (Hindawi Ltd, 2021) Kalayci, Onur; Pehlivan, Ihsan; Akgul, Akif; Coskun, Selcuk; Kurt, Ersin
    In this study, a new chaotic mixer based on the Delta robot was designed and produced which had been controlled with Arduino Uno card and MATLAB. First of all, chaotic mixing systems with different dynamic properties were chosen for the chaotic mixing process. Then, by solving the chaotic systems selected in the MATLAB with the Runge Kutta 45 (RK45) numerical solution algorithm, the results in the integer format were obtained. The obtained chaotic time-series results were transformed into 3-dimensional position information for the servomotors used in the mixer with the algorithm developed in MATLAB. The supervision was provided to ensure that the newly designed chaotic mixer was pacing chaotically in x, y, and z coordinates by transferring the chaotic position information to the Arduino Uno R3 card via USB 2.0. With the software developed in MATLAB, the performances of 7 diversified chaotic systems' trajectories and circular motion trajectories were compared over the numerical simulation orbital distribution ratio (ODR). In the final stage, in a solid-liquid mixture type, at the selected constant mixing time, experimental studies were performed where homogeneity and orbital distribution ratio (ODR) parameters were compared by using 7 diversified chaotic systems. The designed and produced chaotic mixer can also be used in experimental studies of certain liquid-liquid mixture types. It is thought that this prototype presented in the article will serve the aim of developing new chaotic mixer systems and algorithms to derive more homogeneous mixtures in a shorter time.
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    A new hyperchaotic system from T chaotic system: dynamical analysis, circuit implementation, control and synchronization
    (Emerald Group Publishing Ltd, 2021) Emiroglu, Selcuk; Akgul, Akif; Adiyaman, Yusuf; Gumus, Talha Enes; Uyaroglu, Yilmaz; Yalcin, Mehmet Ali
    Purpose The purpose of this paper is to develop new four-dimensional (4D) hyperchaotic system by adding another state variable and linear controller to three-dimensional T chaotic dynamical systems. Its dynamical analyses, circuit experiment, control and synchronization applications are presented. Design/methodology/approach A new 4D hyperchaotic attractor is achieved through a simulation, circuit experiment and mathematical analysis by obtaining the Lyapunov exponent spectrum, equilibrium, bifurcation, Poincare maps and power spectrum. Moreover, hardware experimental measurements are performed and obtained results well validate the numerical simulations. Also, the passive control method is presented to make the new 4D hyperchaotic system stable at the zero equilibrium and synchronize the two identical new 4D hyperchaotic system with different initial conditions. Findings The passive controllers can stabilize the new 4D chaotic system around equilibrium point and provide the synchronization of new 4D chaotic systems with different initial conditions. The findings from Matlab simulations, circuit design simulations in computer and physical circuit experiment are consistent with each other in terms of comparison. Originality/value The 4D hyperchaotic system is presented, and dynamical analysis and numerical simulation of the new hyperchaotic system were firstly carried out. The circuit of new 4D hyperchaotic system is realized, and control and synchronization applications are performed.
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    A Novel Security Methodology for Smart Grids: A Case Study of Microcomputer-Based Encryption for PMU Devices
    (Wiley-Hindawi, 2021) Varan, Metin; Akgul, Akif; Kurugollu, Fatih; Sansli, Ahmet; Smith, Kim
    Coordination of a power system with the phasor measurement devices (PMUs) in real time on the load and generation sides is carried out within the context of smart grid studies. Power systems equipped with information systems in a smart grid pace with external security threats. Developing a smart grid which can resist against cyber threats is considered indispensable for the uninterrupted operation. In this study, a two-way secure communication methodology underpinned by a chaos-based encryption algorithm for PMU devices is proposed. The proposed system uses the IEEE-14 busbar system on which the optimum PMU placement has been installed. The proposed hyperchaotic system-based encryption method is applied as a new security methodology among PMU devices. The success of results is evaluated by the completeness of data exchange, durations, the complexity of encryption-decryption processes, and strength of cryptography using a microcomputer-based implementation. The results show that the proposed microcomputer-based encryption algorithms can be directly embedded as encryption hardware units into PMU and PDC devices which have very fast signal processing capabilities taking into considerations the acceptable delay time for power system protection and measuring applications and quality metering applications which is 2 ms and 10 ms, respectively. While proposed algorithms can be used in TCP or UDP over IP-based IEEE C37.118, IEC 61850, and IEC 61850-90-5 communication frameworks, they can also be embedded into electronic cards, smartcards, or smart tokens which are utilized for authentication among smart grid components.
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    A simple fractional-order chaotic system based on memristor and memcapacitor and its synchronization application
    (Pergamon-Elsevier Science Ltd, 2021) Akgul, Akif; Rajagopal, Karthikeyan; Durdu, Ali; Pala, Muhammed Ali; Boyraz, omer Faruk; Yildiz, Mustafa Zahid
    Memelements play an important part in the design of high density memory systems and low power memory. In this paper, we created a novel fractional-order chaotic circuit with a memristor and a memcapacitor with a linear inductor. The various dynamical properties of the fractional-order system are investigated by using some dynamic analysis methods like Lyapunov exponents and bifurcation after the numerical solution for the fractional-order system. In addition, to show the applicative advantages of the proposed chaotic system, we have realized about the synchronization of fractional-order chaotic systems and used it in secure communication systems first time in the literature according to our knowledge. The results of the theoretical analysis and simulation show that the simple fractional-order chaotic system has very rich dynamic properties and can be used in different engineering applications. (c) 2021 Elsevier Ltd. All rights reserved.
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    Circuit application of chaotic systems: modeling, dynamical analysis and control
    (Springer Heidelberg, 2021) Lai, Qiang; Bao, Bocheng; Chen, Chaoyang; Kengne, Jacques; Akgul, Akif
    This special issue selects some interesting contributions of recent scientific achievements in circuit application of chaotic systems, focusing on showing the new methods and technologies of the modeling, dynamical analysis and control of chaotic systems. This presented letter summarizes the work of the special issue and discusses some thoughts on the future directions of chaotic circuits and systems.
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    Development of micro computer based mobile random number generator with an encryption application
    (Elsevier, 2021) Akgul, Akif; Gurevin, Bilal; Pehlivan, Ihsan; Yildiz, Muhammed; Kutlu, Mustafa C.; Guleryuz, Emre
    In this study, an equation is derived by changing the parameter values of a chaotic system in the literature and analyzing its chaotic behavior. In the analysis of chaotic behaviors, chaotic system analyses such as phase portraits, sensitivity to initial conditions, Lyapunov exponential spectrum and dimension analysis, bifurcation diagram with Matlab (R) software were investigated. The derived equations were embedded into a mobile random number generator (RNG). RNG was developed on the Raspberry Pi 3 Model B microcomputer. It has been shown that the obtained random numbers can be securely used in encryption applications by successfully passing the statistical tests NIST 800-22, FIPS 140-1 and ENT. An image encryption application with the generated random numbers was implemented on the Raspberry Pi 3 Model B microcomputer. Finally, the encrypted image was subjected to security tests such as histogram analysis, correlation and entropy coefficients, correlation card, NPCR, UACI utilizing MATLAB software. The performance and reliability of the encryption algorithm were also measured. This paper improves the current state of art as it implements chaotic random number generation algorithm in a small footprint micro computer.
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    Fractional-Order Analysis of Modified Chua's Circuit System with the Smooth Degree of 3 and Its Microcontroller-Based Implementation with Analog Circuit Design
    (Mdpi, 2021) Wang, Junxia; Xiao, Li; Rajagopal, Karthikeyan; Akgul, Akif; Cicek, Serdar; Aricioglu, Burak
    In the paper, we futher consider a fractional-order system from a modified Chua's circuit system with the smooth degree of 3 proposed by Fu et al. Bifurcation analysis, multistability and coexisting attractors in the the fractional-order modified Chua's circuit are studied. In addition, microcontroller-based circuit was implemented in real digital engineering applications by using the fractional-order Chua's circuit with the piecewise-smooth continuous system.