Mekatronik Mühendisliği Bölümü

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Citation - Scopus: 5
Abstraction-Based Supervisory Control for Recon-Gurable Manufacturing Systems
(IFAC Secretariat, 2013) Khalid, H.M.; Kirik, M.S.; Schmidt, K.W.; 271229; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.
Citation - WoS: 1
Citation - Scopus: 3
Analytical Solution of Thermal Stresses in a Functionally Graded Solid Cylinder Within Parabolic Continuous Grading
(Trans Tech Publications Ltd, 2013) Gulgec, Mufit; Ozturk, Ali; 4168; 01. Çankaya Üniversitesi; 06. Mühendislik Fakültesi; 06.08. Mekatronik Mühendisliği
This paper presents analytical solutions of the thermal stresses in a functionally graded solid cylinder with fixed ends in elastic region. These thermal stresses are due to the uniform heat generation inside the cylinder. Material properties of the functionally graded (FG) cylinder vary radially according to a parabolic form. The material properties are assumed to be independent of the temperature which are yield strength, elasticity modulus, thermal conduction coefficient, thermal expansion coefficient and Poisson's ratio. The solutions for the thermal stresses are valid for both homogeneous and functionally graded materials.
Citation - Scopus: 12
Applied Supervisory Control for a Flexible Manufacturing System
(IFAC Secretariat, 2010) Moor, T.; Schmidt, K.; Perk, S.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
This paper presents a case study in the design and implementation of a discrete event system (DES) of real-world complexity. Our DES plant is a flexible manufacturing system (FMS) laboratory model that consists of 29 interacting components and is controlled via 107 digital signals. Regarding controller design, we apply a hierarchical and decentralised synthesis method from earlier work in order to achieve nonblocking and safe closed-loop behaviour. Regarding implementation, we discuss how digital signals translate to discrete events from a practical point of view, including timing issues. The paper demonstrates how both, design and implementation, are supported by the open-source software tool libFAUDES.
Citation - WoS: 12
Citation - Scopus: 12
Averaging of Receiver Aperture for Flat-Topped Incidence
(Elsevier Sci Ltd, 2013) Kamacioglu, Canan; Baykal, Yahya; Yazgan, Erdem; 7812; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Using a flat-topped profile for the incident beam, the power scintillation index for weak atmospheric turbulence is formulated and analytically evaluated. Through the use of the aperture averaging factor, the averaging effect of the finite receiver aperture on the intensity fluctuations for a flat-topped incident beam is examined. The influence of the order of flatness on the averaging is investigated. At large propagation lengths, increasing the flatness parameter decreases the power scintillations and it is possible to further reduce the scintillation by increasing the receiver aperture. Increasing the structure constant increases this effect. (C) 2013 Elsevier Ltd. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 2
Classification of Low Probability of Intercept Radar Waveforms Using Gabor Wavelets
(Gazi Univ, Fac Engineering Architecture, 2021) Ergezer, Halit; 29339; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.
Citation - WoS: 20
Citation - Scopus: 21
A Comparison of Iterative Fourier Transform Algorithms for Image Quality Estimation
(Optical Soc Japan, 2018) Alsaka, Dina Yaqoob; Arpali, Caglar; Arpali, Serap Altay; 20809; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A comparison was established between two iterative Fourier transform algorithms (IFTAs), such as the original Gerchberg-Saxton (GS) and the mixed-region amplitude freedom (MRAF) algorithms, for the hologram reconstruction of different target images through the full reference image quality estimation (IQE) and pixel homogeneity in the Fourier plane presented theoretically and experimentally. The comparison was applied depending upon both algorithms based on a computer-generated hologram (CGH) implemented utilizing a reflective phase-modulated liquid-crystal spatial light modulator (LC-SLM) to obtain the digital kinoform holograms of the desired intensity distributions. These digital holograms were applied to reconstruct the intensity patterns for 852 nm, which represents a laser beam source. The theoretical and experimental results of the reconstructed patterns obtained using the MRAF algorithm were found to be smoother and better than the patterns obtained using the GS algorithm. Unmodulated light beam (dc term) is removed from the reconstructed patterns attributed to digital kinoform holograms of MRAF algorithm as an alternative to the theoretical and experimental results without using any additional optic equipment at the light path. Moreover, this paper discussed the full reference objective quality estimations, such as mean square error (MSE), peak signal-to-noise ratio (PSNR), structural content (SC), normalized absolute error (NAE), normalized cross correlation (NK), and homogeneity of pixels, through the contrast (Cont) and inverse difference moment (IDM) for numerical and experimental results. According to the two desired intensity distributions processed theoretically and experimentally, the results of MRAF algorithm were found to be in the highly accurate recovered phase, the quality of image was enhanced, and the dc term was decreased. Image quality estimation of full reference objective relay on the feedback algorithms experimental attestation has not been implemented yet.
Citation - Scopus: 6
The 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.; 3837; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.
Comprehensive Comparison of Various Machine Learning Algorithms for Rf Fingerprints Classification
(Institute of Electrical and Electronics Engineers Inc., 2023) Ergezer, H.; Gundogan, B.; 293396; 01. Çankaya Üniversitesi; 06. Mühendislik Fakültesi; 06.08. Mekatronik Mühendisliği
In these days, the use of drones has become quite common. Remote controls can do the control of these drones with RF signals. It is important to prevent security vulnerabilities caused by using drones in our daily lives. A complex dataset was created by extracting the characteristics of the RF signals and preprocessing them. To solve this complex data set and problem, the application of models including Support Vector Machine (SVM), Random Forest, Decision Tree, Gradient Boosting, XGBoost and Neural Network (NN) models, including various ML models and comparison of optimization studies of these applied models are examined in this article. In addition, a wide range of studies was carried out to compare ML models, including comparison metrics such as Accuracy, Precision, Recall, Mean Squared Error (MSE), F1 Score, $R^{2}$ and Training Time. In line with these results, the highest score was obtained in the $\mathrm{R}^{2}$ comparison metric (97%) in the Neural Network (NN). Compared to the others, the results of Neural Network (NN) were more successful, but the Training Time (245 sec) in the Neural Network (NN) method is by far more than the other ML methods, which shows us that the NN method requires a very high computing process. As a result of the comparison, another outstanding Ensemble-based ML method is Decision Tree. This is because besides the very low Training Time $(5\sec)$, it has managed to be the 2nd ML algorithm with the highest $\mathrm{R}^{2}$ score (96%). Apart from these, among other ML methods, SVM performed slightly less well $(\mathrm{R}^{2}$ 91%) in solving this complex problem. The advanced Gradient Method (95%) and XGBoost (96%), which also have the Ensemble structure, showed a head-to-head performance regarding $\mathrm{R}^{2}$ scores. However, XGBoost (30 sec) has a very short Training Time compared to Gradient Boosting (180 sec). As a result, the approach of each ML method to solving the complex problem differed from each other, and the success rates and Training Time also differed equally. The most important work to be done here is to choose which ML method you want to achieve according to the limited system in hand and the performance-accuracy dilemma. © 2023 IEEE.
Citation - Scopus: 8
Computation of Fault-Tolerant Supervisors for Discrete Event Systems
(IFAC Secretariat, 2013) Sülek, A.N.; Schmidt, K.W.; 17337; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.
Citation - Scopus: 2
Computation of Supervisors for Fault-Recovery and Repair for Discrete Event Systems
(Univelt Inc., 2014) Sülek, A.N.; Schmidt, K.W.; 17337; 107424; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this paper, we study the fault-recovery and repair of discrete event systems (DES). To this end, we first develop a new method for the fault-recovery of DES. In particular, we compute a fault-recovery supervisor that follows the specified nominal system behavior until a fault-occurrence, that continues its operation according to a degraded specification after a fault and that finally converges to a desired behavior after fault. We next show that our method is also applicable to system repair and we propose an iterative procedure that determines a supervisor for an arbitrary number of fault occurrences and system repairs. We demonstrate our method with a manufacturing system example. © IFAC.
Citation - WoS: 9
Citation - Scopus: 10
Computation of Supervisors for Reconfigurable Machine Tools
(Springer, 2015) Schmidt, Klaus Werner; 17337; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The rapid reconfiguration of manufacturing systems is an important issue in today's manufacturing technology in order to adjust the production to varying product demands and types. In this paper, we study the control of reconfigurable machine tools (RMTs) with the aim of fast reconfiguration and an easy controller implementation. We first formulate a particular reconfiguration problem for RMTs in a discrete event system setting, and then provide a necessary and sufficient condition for its solution. Moreover, we propose a polynomial-time algorithm for the construction of a reconfiguration supervisor as the composition of one modular supervisor for each separate RMT configuration. Each modular supervisor operates in three modes. In the first mode, it tracks the plant state if its corresponding configuration is inactive. In the second mode, it performs a configuration change if its corresponding configuration becomes active and in the third mode, it follows the specified behavior of its corresponding configuration if the configuration is active. An important property of the proposed reconfiguration supervisor is that it performs reconfigurations in a bounded number of event occurrences. In addition, the modular realization of our reconfiguration supervisor enables controller modifications such as adding or removing configurations during run-time. All results presented in the paper are illustrated by an RMT example.
Citation - WoS: 2
Citation - Scopus: 3
Control Structure Design With Constraints for a Slung Load Quadrotor System
(Sage Publications Ltd, 2024) Leblebicioglu, Kemal; Ergezer, Halit; 293396; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.
The Controllability Prefix for Supervisory Control Under Partial Observation With an Application To Fault-Tolerant Control
(Elsevier, 2017) Moor, Thomas; Schmidt, Klaus Werner; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The controllability prefix is known as a useful concept for the discussion and solution of synthesis problems in supervisory control of cp-languages, i.e., formal languages of infinite-length words. There, the controllability prefix is defined as the set of all finite-length prefixes that can be controlled to satisfy prescribed liveness and safety properties. In this paper, we discuss a variation of the controllability prefix to address supervisory control under partial observation for regular *-languages, i.e., formal languages of finite-length words. We derive algebraic properties that are useful for a quantitative analysis on how an upper-bound language-inclusion specification affects achievable lower-bound specifications. Our study is motivated by the synthesis of fault-tolerant supervisory controllers, where the possible occurrence of a fault may restrict the achievable pre-fault behaviour so severe, that a relaxation of the upper-bound specification becomes a practical option. As our study shows, such a relaxation can be systematically constructed in terms of the controllability prefix. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 6
Controller Area Network With Priority Queues and Fifo Queues: Improved Schedulability Analysis and Message Set Extension
(inderscience Enterprises Ltd, 2016) Schmidt, Klaus Werner; Alkan, Burak; Schmidt, Ece Guran; Karani, Duygu Culum; Karakaya, Utku; 17337; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Controller area network (CAN) enables communication of electronic control units (ECUs) via messages using priority-based arbitration, which requires the implementation of priority queues (PQs) in the ECU device driver. Nevertheless, it is possible that not all ECUs on a CAN support PQs but use FIFO queues (FQs) instead. In this case, the classical CAN scheduling model with PQs is not suitable for the computation of message worst-case responsetimes (WCRTs) that are essential for verifying the correct vehicle operation. This paper considers an existing scheduling model for CAN with both PQs and FQs. First, an improved algorithm for speeding up the WCRT computation is proposed. Second, the practical case where an existing CAN message set is extended by new messages is addressed. An original algorithm for assigning priorities to new messages while keeping the priority order of existing messages is developed. Both algorithms are evaluated by computational experiments.
Controller Design for Cacc With Time-Varying Communication Delays
(Ieee, 2023) Soysal, Gokhan; Schmidt, Klaus Werner; Bingol, Hilal; 218795; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Cooperative Adaptive Cruise Control (CACC) aims at the safe and comfortable travel of vehicles at short distances in the form of platoons. Hereby, it is generally desired to attenuate disturbances along vehicles in a platoon, which is captured by different string stability conditions. In this paper, we focus on L-infinity string stability. This condition ensures reducing the magnitude of the acceleration signal along the platoon, which helps to avoid actuator saturation and increases driving comfort. Since the performance of CACC is adversely affected by time-varying communication and actuator delays, we develop the first controller design method for L-infinity-string stability, combining the Lyapunov-Krasovskii method and our custom bisection algorithm. Simulation experiments demonstrate the effectiveness of our method.
Citation - Scopus: 3
Controller Design for Quadrotor-Slung Load System With Swing Angle Constraints Using Particle Swarm Optimization
(Institute of Electrical and Electronics Engineers Inc., 2021) Cosan, O.; Degirmenci, B.; Ergezer, H.; Ozgehan, M.; Ates, A.; 293396; 01. Çankaya Üniversitesi; 06. Mühendislik Fakültesi; 06.08. Mekatronik Mühendisliği
In this paper, the controller is designed for a quadrotor carrying a slung load with a rope. When we consider the quadrotor and load pair, there are two cases: the quadrotor carries the load, and the load is on the ground. Since the dynamics of the system are different for these two cases, they must be considered separately. Therefore, a different PID controller is designed for each case. The necessary mechanism has been created to ensure that the transitions between these two controllers are smooth. The controller coefficients are adjusted so that the swing angles of the load are minimal. IMU has been added to the load-bearing mechanism to find out what angle the load is. Also, images of the load have been obtained with the camera located under the quadrotor. The swing angles have been calculated according to the position of the load in the image. Although our physical system studies continue, both the IMU and camera models have been created and integrated into the quadrotor-slung load model. PID coefficients have been obtained using the Particle Swarm Optimization method. Tests have been carried out on different flight profiles and the results obtained are presented. © 2021 IEEE.
Citation - WoS: 12
Citation - Scopus: 18
Cooperative Adaptive Cruise Control for Vehicle Following During Lane Changes
(Elsevier, 2017) Schmidt, Klaus W.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.
Citation - WoS: 6
Citation - Scopus: 6
Design and Implementation of an Electrode Feed Rate Control System in the Electrochemical Drilling Process
(Springer Heidelberg, 2022) Cogun, Can; Ozerkan, Haci Bekir; 3837; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The interelectrode gap distance control is essential for preventing short circuit and spark discharge occurrences in the machining gap and ensuring a constant distance between the tool electrode (shortly electrode) and the workpiece throughout the electrochemical drilling (ECD) process. In this study, a gap distance control system was designed and implemented in the constructed ECD machine tool. The gap distance control strategy was based on the machining current's discrete measurement (in microsecond intervals) and changing the gap distance according to a set current value by feeding the electrode towards the workpiece or retracting it during the ECD process. The small diameter deep hole ECD experiments were conducted using 0.5 mm diameter side insulated tubular rotational electrodes with through-hole electrolyte flushing to drill Hadfield and AISI 1040 steels. The experimental results demonstrated the success of the developed control system in ECD operations yielding uniform hole geometries and smooth hole surfaces. The use of the control system eliminated the undesirable formations of spark discharges and short circuit pulses.
Design and Implementation of Visual Simultaneous Localization and Mapping (Vslam) Navigation System
(Ieee, 2021) Ergezer, Halit; Bekcan, Arda; 293396; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
It is very important to guess the location of the redetected objects and loop closures with the visual simultaneous localization and mapping system (VSLAM), one of the biggest problems of a mobile robot. VSLAM makes it possible to eliminate and/or reduce these applications' errors and realize or improve the robot's direction and position correctly by creating a map of the environment. This study aims to achieve an autonomous indoor/outdoor navigation of a ground robot using VSLAM algorithm in an unknown environment using a monocular camera. In this context, the theoretical information was tested in real-world conditions. Performance of localization and loop closing were compared based on the results obtained by experiments

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