Mekatronik Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/255

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A new systematic and exible method for developing hierarchical decision-making models
(Tubitak Scientific & Technological Research Council Turkey, 2015) Beldek, Ulas; Leblebicioglu, Mehmet Kemal; 59950
The common practice in multilevel decision-making (DM) systems is to achieve the final decision by going through a finite number of DM levels. In this study, a new multilevel DM model is proposed. This model is called the hierarchical DM (HDM) model and it is supposed to provide a flexible way of interaction and information flow between the consecutive levels that allows policy changes in DM procedures if necessary. In the model, in the early levels, there are primary agents that perform DM tasks. As the levels increase, the information associated with these agents is combined through suitable processes and agents with higher complexity are formed to carry out the DM tasks more elegantly. The HDM model is applied to the case study 'Fault degree classification in a 4-tank water circulation system'. For this case study, the processes that connect the lower levels to the higher levels are agent development processes where a special decision fusion technique is its integral part. This decision fusion technique combines the previous level's decisions and their performance indicator suitably to contribute to the improvement of new agents in higher levels. Additionally, the proposed agent development process provides flexibility both in the training and validation phases, and less computational effort is required in the training phase compared to a single-agent development simulation carried out for the same DM task under similar circumstances. Hence, the HDM model puts forward an enhanced performance compared to a single agent with a more sophisticated structure. Finally, model validation and efficiency in the presence of noise are also simulated. The adaptability of the agent development process due to the flexible structure of the model also accounts for improved performance, as seen in the results.
Abstraction-Based Supervisory Control for Recon-Gurable Manufacturing Systems?
(IFAC Secretariat, 2013) Khalid, H.M.; Kirik, M.S.; Schmidt, K.W.; 271229
Reconfiguration control for discrete event systems (DES) is concerned with the realization of different system configurations by modification of the supervisory control loop. In this paper, we study the reconfiguration supervisor design for reconfigurable manufacturing systems (RMS) that comprise multiple components. We construct a modular supervisor for each configuration and system component in order to realize each active configuration and to quickly change between configurations. Different from the existing literature that is focused on monolithic design, our method is abstraction-based, and, hence applicable to large-scale DES. © 2013 IFAC.
An Electromagnetic Micro-Power Generator for Low Frequency Vibrations With Tunable Resonance
(Elsevier Science Bv, 2011) Turkyilmaz, S.; Zorlu, O.; Muhtaroglu, A.; Kulah, H.
This paper presents an electromagnetic (EM) micro-power generator with tunable resonance frequency which can harvest energy from low frequency environmental vibrations. The reported power generator up-converts low frequency environmental vibrations before mechanical-to-electrical energy conversion by utilizing two diaphragms with different resonance frequencies. Power is generated through electromagnetic induction by a magnet attached to the low frequency diaphragm, and a 50 turn, 2.1 Omega coil, and a magnetic piece on the high frequency diaphragm. Both of the diaphragms are fixed to a common frame via rubber springs, which makes the resonance frequency of each diaphragm tunable. The fabricated prototype generates 5.2 mV and 3.21 mu W RMS power by up-converting 13 Hz, 7.5 mm peak-to-peak vibrations to 200 Hz. Tunability of the resonance frequency is experimentally verified by operating the same device at 2-30 Hz external vibrations. (C) 2011 Published by Elsevier Ltd.
Çekilebilir Sahte Hedef Etkinliğinin Modelleme Ve Simülasyon İle Analizi
(2019) Ergezer, Halit; Ergezer, Halit; 293396; 293396
Sahte hedefler, uçağın savaş alanında hayatta kalmasını artırmak için radar güdümlü füzeden korumak için kullanılan bir savunma yöntemlerindendir. Bu çalışmada savaş uçaklarında kullanılan çekilebilir aktif sahte hedeflerin uçağın hayatta kalabilirliğine etkisi, uçağın çekilebilir sahte hedef kullandığı ve kullanmadığı durumlar için vurulma olasılıkları ve füzenin kaçırma uzaklığı değerleri hesaplanarak analiz edilmiştir. Çalışmamızda açık kaynaktan elde edilen veriler kullanılmıştır. Jenerik yapıda kurgulanan savaş uçağı modeli, çekilebilir sahte hedef modeli ve radar modeli ile elde edilen veriler sunulmuştur. Benzetim sonuçları çekilebilir aktif sahte hedef kullanımının savaş uçaklarına özellikle angajmanın son safhasında koruma sağladığını ortaya koymaktadır.
Classification of low probability of intercept radar waveforms using gabor wavelets
(Gazi Univ, Fac Engineering Architecture, 2021) Ergezer, Halit; Ergezer, Halit; 29339
Low Probability of Intercept (LPI Radar) is a class of radar with specific technical characteristics that make it very difficult to intercept with electronic support systems and radar warning receivers. Because of their properties as low power, variable frequency, wide bandwidth, LPI radar waveforms are difficult to intercept by ESM systems. In recent years, studies on the classification of waveforms used by these types of radar have been accelerated. In this study, Time-Frequency Images (TFI) has been obtained from the LPI radars waveforms by using Choi-Williams Distribution method. From these images, feature vectors have been generated using Gabor Wavelet transform. In contrast to many methods in the literature, waveform classification has been performed by directly comparing the feature vectors obtained without using any machine learning method. With the method we propose, classification accuracies were obtained at intervals of 2 dB between -20 dB and 10 dB and performed at reasonable classification accuracy rates up to -8 dB SNR value. Better results than the best reported in the literature were obtained for some signal types. The results obtained for all waveform types are given in comparison with the results of the existing methods in the literature.
Clothoid-based Lane Change Trajectory Computation for Self-Driving Vehicles
(2017) Mohammed Ali Kahya, Ardam Haseeb; Schmidt, Klaus Werner
The subject of this paper is the efficient computation of lane change trajectories for self-driving vehicles. The paper first identifies that a certain type of clothoid-based bi-elementary paths can be used to represent lane change trajectories for vehicles. It is further highlighted that the curvature of such trajectories must be adjusted to the driving situation in order to obtain feasible lane change trajectories. Accordingly, the paper establishes an analytical relation between the maximum admissible curvature of the lane change trajectory and the velocity profile during a lane change. Using this relation, the paper proposes an efficient Newton iteration for computing the parameters of bi-elementary paths for lane changes. The resulting lane change trajectories are as short as possible, while meeting the constraint on the maximum curvature. Simulation experiments for various driving situations show that the computed bi-elementary paths can be computed efficiently and constitute suitable lane change trajectories.
Çoklu ˙IHA Kullanımı ile Kabloya Asılı Yük Ta¸sınımı Transportation of Cable Suspended Slung Load System Using Multiple UAVs
(2022) Ergezer, Halit; Leblebicioğlu, M. Kemal; Ergezer, Halit; 293396
Bu çalı¸smada, kablolar ile asılı esnemeyen bir yükün ortakla¸sa ta¸sınımı için kontrolcü tasarımı tanıtılmı¸stır. Yük, birden çok insansız hava aracına (˙IHA) yükün kablo ile baglanması ˘ ile ta¸sınmakta olup, istenen üç boyutlu rota üzerinde hareket etmesi saglanmaktadır. Sistemde yük lider olarak alınmaktadır. ˘ Hiyerar¸sik ve merkezcil bir yapıda kontrol edilmektedir. Ta¸sıma görevi, bir optimizasyon problemi olarak ele alınmı¸stır. Sistemi istenen rotada hareket ettirebilmek için bir otopilot algoritması tasarlanmı¸s olup PD yapıları kullanılarak olu¸sturulmu¸stur. Pozisyon kontrolcüsünün çıktısı kontrol atama matrisi tarafından ele alınmaktadır ve uygun kuvvet dagılımını sistemin istenen ˘ davranı¸slarına uygun olacak ¸sekilde türetmektedir. Kontrolcü performansları, takip edilmesi istenen bir rota üzerinde test edilmektedir.
Computation of Fault-Tolerant Supervisors for Discrete Event Systems ?
(IFAC Secretariat, 2013) Sülek, A.N.; Schmidt, K.W.; 17337
Fault-tolerance addresses the problem of operating a system even in case of faults. In this paper, we study fault-tolerance in the supervisory control framework for discrete event systems (DES). We consider DES, where certain events might no longer be possible in case a fault happens. In this setting, we first identify necessary and suficient conditions for the existence of a supervisor that realizes a given behavioral specification both in the non-faulty and in the faulty case. We further show that it is possible to determine a supremal fault-tolerant sublanguage in case the existence condition is violated. Finally, we propose an algorithm for the computation of this sublanguage and prove its correctness. Different from existing work, our fault-tolerant supervisor allows fault occurrences and system repairs at any time. The concepts and results developed in this paper are illustrated by a manufacturing system example. © 2013 IFAC.
Computation of Projections for the Abstraction-Based Diagnosability Verification
(IFAC Secretariat, 2010) Schmidt, K.
The verification of language-diagnosability (LD) for discrete event systems (DES) generally requires the explicit evaluation of the overall system model which is infeasible for practical systems. In order to circumvent this problem, our previous work proposes the abstraction-based LD verification using natural projections that fulfill the loop-preserving observer (LPO) property. In this paper, we develop algorithms for the verification and computation of such natural projections. We first present a polynomial-time algorithm that allows to test if a given natural projection is a loop-preserving observer. Then, we show that, in case the LPO property is violated, finding a minimal extension of the projection alphabet such that the LPO condition holds is NP-hard. Finally, we adapt a polynomial-time heuristic algorithm by Feng and Wonham for the efficient computation of loop-preserving observers.
Control structure design with constraints for a slung load quadrotor system
(Sage Publications Ltd, 2024) Ergezer, Halit; Ergezer, Halit; Leblebicioglu, Kemal; 293396
We propose a control structure for a quadrotor carrying a slung load with swing-angle constraints. This quadrotor is supposed to pass through the waypoints at specified speeds. First, a cascaded PID autopilot is designed, which adaptively gives attention to position and speed requirements as a function of their errors. Its parameters are found from an optimization problem solved using the PSO algorithm. Second, this controller's performance is improved by adding the Complementary Controller employing an ANN. 5. Training data for the ANN is created by solving optimal control problems. The ANN is activated when the swing angle constraint is about to be violated. It is trained using optimal control values corresponding to the cases where the swing angle falls in a particular band about the upper swing angle constraint. Simulations are performed in a MATLAB environment. Finally, some of the simulation results are validated on a physical system.
Cooperative adaptive cruise control for vehicle following during lane changes
(Elsevier, 2017) Schmidt, Klaus W.
This paper addresses the longitudinal vehicle behavior before and during lane changes. Hereby, it is desired that the lane-changing vehicle simultaneously follows its predecessors on the lanes before and after the lane change. Specifically, the lane changing vehicle should keep a safe distance to the rearmost predecessor vehicle, while maintaining a small inter vehicle spacing and supporting driving comfort. To this end, the paper develops an extension of cooperative adaptive cruise control (CACC). Instead of following a single vehicle as in the classical realization of CACC, it is proposed to follow a virtual vehicle that is evaluated based on distance measurements and communicated state information from the predecessor vehicles. A simulation study demonstrates the practicability of the proposed method. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
Development of air-to-ground engagement analysis model of fighter aircrafts
(Gazi Univ, Fac Engineering Architecture, 2022) Erdogan, Sinem; Ergezer, Halit; Bektas, Almila; Ergezer, Halit; 293396
In operational analysis studies; it is possible to model and simulate at an engineering level, engagement level, task level and campaign forces level. In this study, modelling and simulation studies are performed in engagement-level allowing the analysis of air-to-ground engagement effectiveness of fighter aircraft according to the operational environment. The operating environment of the combat aircraft, which provides survivability analysis based on low visibility and electronic mixing capabilities, is created. The search radar and tracking radar models for ground-to-air threats have been designed in accordance with the engagement level. The dynamic model of the fighter aircraft and the ground-to-air missile have been modelled using pseudo 5 degree-of-freedom. Modelling has been carried out to allow the use of changes in the Radar Crosssectional Area (RCS), which is one of the most important factors affecting the survivability of the aircraft, with respect to azimuth and elevation angles. The Radio Frequency (RF) jamming capability of the fighter aircraft has also been modelled in accordance with the engagement level. The results of the generic scenarios for the analysis of the effect of these models' parameters on the survivability of fighter aircraft have been presented.
Effect of Machining on Workpiece Surface Characteristics in Electric Discharge Drilling (EDD)
(2019) Çoğun, Can; Erdem, Oguz; Çoğun, Can; Uslan, İbrahim; 3837
Elektro erozyon ile delik delmede (EEDD), işparçası yüzeyinin elektriksel boşalmalar yoluyla hızlı bir şekilde bölgesel olarak ısıtılması ve soğutulması, yüzey katmanlarına (tekrardan katılaşmış, ısıl etkilenmiş ve ana malzeme) neden olur. Bu çalışmada, ana işparçası yüzey dokusu, yani tekrardan katılaşmış katman kalınlığı (RLT) ve ortalama yüzey pürüzlülüğü (Ra) özellikleri, farklı işleme parametreleri için (boşalım akımı ve vurum süresi) araştırılmıştır. Yapılan deneyler, yüzey özelliklerinin işleme parametrelerine kuvvetle bağımlılığını ortaya koymuştur.
ELECTROCHEMICAL SMALL DIAMETER DEEP HOLE DRILLING OF POWDER METAL STEEL
(Univ Zagreb Fac Mechanical Engineering & Naval Architecture, 2020) Ozerkan, Haci Bekir; Çoğun, Can; Cogun, Can; 3837
In this study, a new hybrid electrochemical drilling (ECD) method is proposed. The method makes use of a tubular tool capable of rotating and an electrolyte flushing through the inner hole at the same time. The designed and manufactured small size ECD machine's most important features are the regulation of the tool feed rate via current feedback control and the use of a rotating tubular tool with internal electrolyte flushing. The powder metal (PM) FLN2 4405 steel was drilled by using a brass tubular tool with various combinations of machining parameters such as machining voltage, electrolyte concentration and flushing pressure, and tool rotation speed. The machining performance outputs, namely, material removal rate (MRR), average radial overcut (RADOC), conicity (CO) and hole geometries were calculated and compared in different machining conditions. The results have shown that the aforementioned variables had a direct impact on the machining performance outputs in ECD. In all experiments, MRR increased with an in increase in machining voltage, tool rotational speed, electrolyte concentration and flushing pressure. RADOC values decreased with the rotational speed of the tool. The present study shows that deep holes with precise geometries and dimensions can be drilled successfully by employing the proposed hybrid ECD method. The method is economical and environmentally friendly since it requires low machining current values (0.1 to 0.7A) and a small amount of non-hazardous halide salt solutions instead of acidic solutions throughout the drilling process.
Elektro Erozyon İle İşlemede Cu-Cr T/M Elektrot Kullanımının İşleme Performansına Etkisi
(2015) Çoğun, Can; Uslan, İbrahim; Usta, Yusuf; Çoğun, Can; 3837
Bu çalışmada, Cu-Cr toz metal (T/M) elektrot kullanımının elektro erozyon ile işleme (EEİ) performans çıktılarından işparçası işleme hızı (İİH), elektrot aşınma hızı (EAH), işlenmiş yüzeyin ortalama ve azami yüzey pürüzlülükleri (Ra ve Rz) ve işparçası yüzey katman kalınlıklarına etkileri deneysel olarak incelenmiştir. Farklı toz karıştırma oranları, sıkıştırma basınçları ve sinterleme sıcaklıklarında elde edilen Cu-Cr T/M elektrotlar SAE 1040 çeliğinin işlenmesinde kullanılmıştır. Analizler, elektrot malzemesinin işparçası yüzeyinde katman halinde alaşımlandığını ve karıştırma oranı, sıkıştırma basıncı ve sinterleme sıcaklığının EEİ performans çıktılarını etkilediğini göstermiştir.
Elektrokimyasal Jet İşleme (EJİ) Parametrelerinin İşlenen Kanal Geometrilerine Etkisi
(2021) Ayhan, Emre; Çoğun, Can; Yurdakul, Mustafa; Çoğun, Can; 3837
Bu çalışmada alışılmamış imal usullerinden elektrokimyasal jet işleme yöntemi (EJİ) kullanılarak HSS malzeme üzerine kanallar oluşturularak, işleme parametrelerinin kanal kesit geometrisine etkileri incelenmiştir. Çalışmada, işleme parametreleri olarak takım ilerleme hızı, işleme gerilimi, elektrolit sıvı basıncı ve elektrolit tuz derişimi ele alınmıştır. Her deneye ait kanal kesit geometrileri için profil tamlık değerleri, ortalama kanal derinliği ve genel uyum değerleri hesaplanmıştır. Hesaplanan genel uyum değerlerinde en iyi sonuçların işleme geriliminin 20 V olduğu deneylerde elde edildiği görülmüştür. Takım ilerleme hızının 0,5 mm/dak olduğu deneylerde genel uyum değerlerinin daha yüksek olduğu görülmüştür.
Eyleyici doyumu altında dizi kararlı kooperatif otomatik seyir kontrolü
(Pamukkale Univ, 2016) Bingöl, Hilal; Bingol, Hilal; Cankaya, Erkam; Schmıdt, Klaus Werner; Schmidt, Klaus Werner; 218795
Cooperative adaptive cruise control (CACC) enables safe vehicle following in dense traffic based on distance measurements and communicated data via vehicle-to-vehicle communication. Existing CACC designs achieve the essential property of string stability but are limited to linear vehicle models. In this paper, we show that string stability is preserved when using a nonlinear vehicle model if the input signal of the leader vehicle does not saturate.
Farklı İşleme Derinliklerinde Uygulanan Titreşimlerin Elektro-Erozyon ile İşleme Performansına Etkisi
(2014) Çoğun, Can; Çoğun, Can; 3837
Bu çalışmada, Elektro-Erozyon ile İşleme (EEİ) tekniğinin performans çıktılarını iyileştirmek amacı ile işparçasına farklı frekansta titreşimlerin uygulandığı boşalım akımı ve işleme derinliği gibi farklı işleme koşullarında deneyler yapılmıştır. Deneylerde titreşimsiz koşullara göre elektrot aşınma hızı (EAH) ve bağıl aşınma (BA) değerlerinde belirgin azalma elde edilmiştir. Titreşimli deneylerde işparçası işleme hızı (İİH) ve ortalama yüzey pürüzlülüğü (Ra) değerlerinde EAH ve BA değerlerine göre daha küçük değişimler tespit edilmiştir.
Fault-tolerant control of discrete-event systems with lower-bound specifications
(Elsevier, 2015) Moor, Thomas; Schmidt, Klaus Werner
Fault-tolerant control addresses the control of dynamical systems such that they remain functional after the occurrence of a fault. To allow the controller to compensate for a fault, the system must exhibit certain redundancies. Alternatively, one may relax performance requirements for the closed loop behaviour after the occurrence of a fault. To achieve fault tolerance for a hierarchical control architecture, a combination of both options appears to be advisable: on each individual level of the hierarchy, the controller may compensate the fault as far as possible, and then pass on responsibility to the next upper level. This approach, when further elaborated for discrete-event systems represented by formal languages, turns out to impose a hard lower-bound inclusion specification on the closed-loop behaviour. The present paper discusses the corresponding synthesis problem and presents a solution. (C) 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
Investigition on the Influence of Parameter Uncertainties in the Position Tracking of Robot Manipulators
(Univ North, 2019) Ghanbarpour Asl, Habib; Han, Kerim Youde
This paper presents a novel trajectory tracking method for robot arms with uncertainties in parameters. The new controller applies the robust output feedback linearization method and is designed so that it is robust to the variation of parameters. Robustness of the algorithm is evaluated when the parameters of the system are floating over 10 percent up and down. An Unscented Kalman Filter (UKF) is applied for state and parameter estimation purposes. As the considered system has 8 unknown parameters while only 5 of them are independent parameters, UKF is applied only to the augmented system with independent parameters. Three types of simulations are applied depending on sensor groups - first with both position and joint sensors, second with only position sensors and third with only joint sensors. The observation of parameters in these groups is discussed. Simulation results show that when both position sensors and joint sensors are used, all the parameters and states are observable and good tracking performances are obtained. When only position sensors are used, the accuracy of the estimated parameters is reduced, and low tracking performances are revealed. Finally, when only joint sensors are applied, the lengths of robot arms are unobservable, but other parameters related to the dynamic system are observable, and poor tracking performances are given.

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