Mekatronik Mühendisliği Bölümü
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Browsing Mekatronik Mühendisliği Bölümü by Publication Index "TR-Dizin"
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Article Citation - WoS: 1Citation - Scopus: 2Classification of Low Probability of Intercept Radar Waveforms Using Gabor Wavelets(Gazi Univ, Fac Engineering Architecture, 2021) Ergezer, HalitLow 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.Article Citation - Scopus: 6The Comparison of Performance of Electrolytic Cu and Cube Tool Electrodes in Electric Discharge Machining of Ti6al4v Alloy(TUBITAK, 2021) Bozkurt, F.; Özerkan, H.B.; Çoğun, C.; Uslan, İ.; Urtekin, L.The most crucial cost element of Electric Discharge Machining (EDM) is the production of tool electrode (shortly electrode). Copper, its alloys, and graphite are the most commonly used electrode materials. Selecting the proper electrode material with low production and material cost, high workpiece material removal rate (MRR) and low tool electrode wear rate (TWR) is key to reducing machining costs with EDM. In this study, the EDM performance of CuBe tool electrodes in the machining of Ti6Al4V alloy was experimentally investigated in comparison to electrolytic Cu (E-Cu) electrodes for different pulse time (ts) and discharge current (I) settings. An increase in MRR and a decrease in TWR and relative wear (RW=TWR/MRR) were observed in machining with CuBe electrodes. However, the high raw material cost of CuBe alloy is an essential drawback in widely using these electrodes in industrial applications. A new performance index formulation is introduced for EDM applications that factor in the production cost of the electrode and its life (i.e., RW). According to our results, the CuBe could be used advantageously as the electrode material at medium current settings. However, at low and high current settings, the low raw material cost of E-Cu makes it more favorable. © 2021, TUBITAK. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 2Development of Air-To Engagement Analysis Model of Fighter Aircrafts(Gazi Univ, Fac Engineering Architecture, 2022) Bektas, Almila; Ergezer, Halit; Erdogan, SinemIn 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.Article Elektro Erozyon ile Delik Delmede İşlemenin İşparçası Yüzey Karakteristiklerine Etkisi(2019) Erdem, Oguz; Çoğun, Can; Uslan, İbrahimElektro 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.Article Elektrokimyasal Jet İşleme (Eji̇) Parametrelerinin İşlenen Kanal Geometrilerine Etkisi(2021) Ayhan, Emre; Yurdakul, Mustafa; Çoğun, CanBu 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.Article Lpi Radar Waveform Classification Using Binary Svm and Multi-Class Svm Based on Principal Components of Tfi(2020) Ergezer, Halit; Bektas, AlmilaSince cognition has become an important topic in Electronic Warfare(EW) systems, Electronic Support Measures (ESM) are used to monitor, interceptand analyze radar signals. Low Probability of Intercept (LPI) radars are preferredto be able to detect targets without being detected by ESM systems. Because of theirproperties as low power, variable frequency, wide bandwidth, LPI Radarwaveforms are difficult to intercept with ESM systems. In addition to intercepting,the determination of the waveform types used by the LPI Radars is also veryimportant for applying counter-measures against these radars. In this study, asolution for the LPI Radar waveform recognition is proposed. The solution is basedon the training of Support Vector Machine (SVM) after applying PrincipalComponent Analysis (PCA) to the data obtained by Time-Frequency Images (TFI).TFIs are generated using Choi-Williams Distribution. High energy regions on theseimages are cropped automatically and then resized to obtain uniform data set. Toobtain the best result in SVM, the SVM Hyper-Parameters are also optimized.Results are obtained by using one-against-all and one-against-one methods. Betterclassification performance than those given in the literature has been obtainedespecially for lower Signal to Noise Ratio (SNR) values. The cross-validated resultsobtained are compared with the best results in the literature.
