Mekatronik Mühendisliği Bölümü Yayın Koleksiyonu

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

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Citation - Scopus: 11
A Longest-Path Problem for Evaluating the Worst-Case Packet Delay of Switched Ethernet
(2010) Schmidt, K.; Schmidt, E.G.; 17337
In the recent years, the use of real-time Ethernet protocols becomes more and more relevant for time-critical networked industrial applications. In this context, this paper presents a method to compute the worst-case packet delays on switched Ethernet. Based on an evaluation of the packet delays at each switch port and the network topology, we construct a weighted directed graph that allows to find the worst-case end-toend packet delay by solving a conventional longest-path problem. © 2010 IEEE.
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
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: 3
Citation - Scopus: 8
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.
Citation - Scopus: 2
An Experimental Study of the Flexray Dynamic Segment
(IFAC Secretariat, 2010) Schmidt, K.; Schmidt, E.G.; Demirci, A.; Yürüklü, E.; Karakaya, U.
It is expected that the time-triggered FlexRay bus will replace the event-triggered Controller Area Network (CAN) for the high-speed in-vehicle communication in future automobiles. To this end, FlexRay provides a static segment for the transmission of periodic messages and a dynamic segment that is suitable for exchanging event-based (sporadic) messages. In this paper, we experimentally evaluate the operation of the FlexRay dynamic segment. In particular, we study how the maximum and average message delays are affected if the length of the dynamic segment, the message payload, the utilization of the dynamic segment and the priority assignment changes. Our experiments are carried out on a FlexRay network with 6 nodes. © 2010 IFAC.
Citation - Scopus: 2
An Optimization Model to Coordinate Scheduling and Controling in Projects: Case With İnstantaneous Control Constraints
(National Technical University of Athens, 2014) Hazir, Ö.; Schmidt, K.W.; Eryilmaz, U.; 17337
Today, many enterprises in different industries take part in various projects, and organizational performances depend more and more on project performances. In order to maximize performance, effective management of project functions is crucial. In this regard, we focus on scheduling and control functions and their relation. Characteristics of data sharing among them and possible integration strategies are theoretically investigated. A model base for a decision support framework that accounts for these interdependencies and supports managers is developed. To solve the formulated integrated project scheduling and control problem, a tabu search algorithm is combined with optimal control techniques. As a result, a project schedule as well as the means and timing of interventions are determined such that the project cost is minimized. The obtained results are supported by computational experiments. Integrated models and algorithms to be developed aim to fill an important theoretical gap in project management.
Citation - WoS: 0
Citation - Scopus: 2
Analytical Solution of Thermal Stresses In A Functionally Graded Solid Cylinder Within Parabolic Continuous Grading
(Trans Tech Publications Ltd, 2013) Ozturk, Ali; Gülgeç, Müfit; Gulgec, Mufit; 4168
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.
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 - Scopus: 0
Comprehensive Comparison of Various Machine Learning Algorithms for RF Fingerprints Classification
(Institute of Electrical and Electronics Engineers Inc., 2023) Gundogan, B.; Ergezer, Halit; Ergezer, H.; 293396
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
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.
Citation - Scopus: 0
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.
Citation - Scopus: 2
Computation of Supervisors for Fault-Recovery and Repair for Discrete Event Systems
(Univelt Inc., 2014) Sulek, A.N.; Schmidt, K.W.; 17337; 107424
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. Copyright © 2014 IFAC.
Citation - WoS: 0
Citation - Scopus: 0
Controller Design for CACC with Time-varying Communication Delays
(Ieee, 2023) Bingol, Hilal; Bingöl, Hilal; Soysal, Gokhan; Schmidt, Klaus Werner; 218795
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) Ates, A.; Ergezer, Halit; Cosan, O.; Degirmenci, B.; Ergezer, H.; Ozgehan, M.; 293396
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.
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: 0
Citation - Scopus: 0
Design and Implementation of Visual Simultaneous Localization and Mapping (VSLAM) Navigation System
(Ieee, 2021) Bekcan, Arda; Ergezer, Halit; Ergezer, Halit; 293396
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
Citation - Scopus: 2
Determination of onset of yield due to material properties in a heat generating two-layered compound cylinder
(2013) Ozturk, A.; Gülgeç, Müfit; Gulgec, M.; 4168
In this theoretical study, based on Tresca's yield criterion and its associated flow rule, the elastic deformation of a centrally heated compound cylinder with fixed ends is investigated analytically by taking into consideration not only the geometrical but also the material parameters such as yield strength, modulus of elasticity, Poisson's ratio, thermal conductivity and coefficient of thermal expansion. These material parameters are assumed to be independent of the temperature. The compound cylinder is assumed to be very long such that axisymmetric condition exists. Both of the constituent materials of the two layers are supposed to be elastic-perfectly plastic materials. There is heat generation in the interior solid cylinder but no heat generation in the outer hollow cylinder. Both of the cylinders are assumed to be bounded perfectly at the interface. Elastic stress analysis is performed to prevent yield in the compound cylinder. © (2013) Trans Tech Publications, Switzerland.
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.
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.
Citation - WoS: 1
Citation - Scopus: 0
Evaluation of features used in electromyography classification
(Ieee, 2021) Alguner, Ayber Eray; Ergezer, Halit; Ergezer, Halit; 293396
Classification of electromyography (EMG) signals using machine learning has been studied for a long time. Today, this classification is tried to be made more accurate, fast and applicable by using the methods developed. However, beside this effort, it is suspected that researchers are using features without taking into account the effects on the classification performance, but often by influence of other researches. From this point of view, the effects of some features used in studies published in recent years on classification performance were tested and the results obtained were shared. In the experiments performed using a common method support vector machine (SVM), it was found that increasing the number of features does not always provide an increase in performance, even in some cases, it causes a decrease in accuracy rates.
Citation - WoS: 1
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.

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