Mekatronik Mühendisliği Bölümü

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Citation Count: Hazir, Oencue; Haouari, Mohamed; Erel, Erdal, "Robust scheduling and robustness measures for the discrete time/cost trade-off problem", European Journal of Operatıonal Research, Vol. 207, No. 2, pp. 633-643, (2010)
Robust Scheduling and Robustness Measures for the Discrete Time/Cost Trade-Off Problem
(Elsevier Science BV, 2010) Hazır, Öncü; Erel, Erdal; Haouari, Mohamed; 4168
Projects are often subject to various sources of uncertainties that have a negative impact on activity durations and costs. Therefore, it is crucial to develop effective approaches to generate robust project schedules that are less vulnerable to disruptions caused by uncontrollable factors. In this paper, we investigate the robust discrete time/cost trade-off problem, which is a multi-mode project scheduling problem with important practical relevance. We introduce surrogate measures that aim at providing an accurate estimate of the schedule robustness. The pertinence of each proposed measure is assessed through computational experiments. Using the insights revealed by the computational study, we propose a two-stage robust scheduling algorithm. Finally, we provide evidence that the proposed approach can be extended to solve a complex robust problem with tardiness penalties and earliness revenues. (C) 2010 Elsevier B.V. All rights reserved.
Citation Count: Schmidt, Klaus; Schmidt, Ece G. "Optimal Message Scheduling for the Static Segment of FlexRay", 2010 Ieee 72nd Vehicular Technology Conference Fall, (2010).
Optimal Message Scheduling for the Static Segment of Flexray
(IEEE, 2010) Schmidt, Klaus Werner; Schmidt, Ece G.; 271229
In this paper, we study the scheduling of periodic messages in the static segment of the FlexRay protocol. Our approach is based on two performance metrics. Similar to previous work, we seek to allocate a minimum number of frame IDs (FIDs) in the static segment. In addition, different from existing work, we want to minimize the message jitter, i.e., the deviation of the message transmission from the required periodicity. To this end, we first derive analytical expressions that quantify the FID allocation and the jitter, and then formulate a linear integer programming problem whose solution is the desired message schedule. An example illustrates our schedule optimization.
Citation Count: Moor, T.; Schmidt, K.; Perk, S.,"Applied Supervisory Control for A Flexible Manufacturing System",Ifac Proceedings Volumes (Ifac-Papersonline), Vol. 10, No. 1, (2010).
Applied Supervisory Control for A Flexible Manufacturing System
(2010) Moor, Thomas; Schmidt, Klaus Werner; Perk, Sebastian
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 Count: Schmidt, Klaus Werner; Schmidt, E.G, "A Longest-Path Problem for Evaluating the Worst-Case Packet Delay of Switched Ethernet", 2010 International Symposium On Industrial Embedded Systems, Sies 2010 - Conference Proceedings, pp. 205-208, (2010).
A Longest-Path Problem for Evaluating the Worst-Case Packet Delay of Switched Ethernet
(2010) Schmidt, Klaus Werner; 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
Citation Count: Schmidt, Klaus; Schmidt, Ece G. "Schedulability Analysis and Message Schedule Computation for the Dynamic Segment of FlexRay",2010 Ieee 72Nd Vehicular Technology Conference Fall, (2010).
Schedulability Analysis and Message Schedule Computation for the Dynamic Segment of Flexray
(IEEE, 2010) Schmidt, Klaus Werner; Schmidt, Ece G.; 271229
In this paper, we perform the schedulability analysis and schedule computation for sporadic real-time messages in the dynamic segment of the FlexRay protocol. We first formulate a linear integer programming problem that allows to determine if a given message schedule is feasible, i.e., the worst-case delay of each message is smaller than its deadline. Then, we develop a heuristic algorithm that enables the efficient computation of feasible schedules. Our results are illustrated by an experimental setup with three FlexRay nodes.
Citation Count: Schmidt, K...et al. (20109. "An Experimental Study of the Flexray Dynamic Segment",Ifac Proceedings Volumes (Ifac-Papersonline), Vol. 43, No. 7, pp. 413-418.
An Experimental Study of the Flexray Dynamic Segment
(IFAC Secretariat, 2010) Schmidt, Klaus Werner; Schmidt, Ece G.; Demirci, Ali; Yürüklü, Emrah; Karakaya, Utku
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.
Citation Count: Schmidt K.,"Computation of Projections for the Abstraction-Based Diagnosability Verification",Ifac Proceedings Volumes (Ifac-Papersonline), Vol. 10, No. 1, pp. 199-204, (2011).
Computation of Projections for the Abstraction-Based Diagnosability Verification
(2011) Schmidt, Klaus Werner
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 Count: Hazir, Oncu; Erel, Erdal; Gunalay, Yavuz, "Robust optimization models for the discrete time/cost trade-off problem", International Journal of Production Economics, Vol.130, No.1, (2011).
Robust Optimization Models for the Discrete Time/Cost Trade-Off Problem
(Elsevier Science BV, 2011) Hazır, Öncü; Erel, Erdal; Günalay, Yavuz
Developing models and algorithms to generate robust project schedules that are less sensitive to disturbances are essential in today's highly competitive uncertain project environments. This paper addresses robust scheduling in project environments; specifically, we address the discrete time/cost trade-off problem (DTCTP). We formulate the robust DTCTP with three alternative optimization models in which interval uncertainty is assumed for the unknown cost parameters. We develop exact and heuristic algorithms to solve these robust optimization models. Furthermore, we compare the schedules that have been generated with these models on the basis of schedule robustness. (C) 2010 Elsevier B.V. All rights reserved.
Citation Count: Turkyilmaz, S...et al. (2011). "An Electromagnetic Micro-Power Generator for Low Frequency Vibrations with Tunable Resonance", Eurosensors XXV, Vol. 25.
An Electromagnetic Micro-Power Generator for Low Frequency Vibrations With Tunable Resonance
(Elsevier Science BV, 2011) Türkyılmaz, S.; Zorlu, O.; Muhtaroğlu, A.; Kulah, Haluk
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 Count: Hazir, O.; Shtub, A. "Effects of the information presentation format on project control", Journal of the Operational Research Society, Vol. 62, No. 12, pp. 2157-2161, (2012)
Effects of the Information Presentation Format On Project Control
(Taylor&Francis LTD, 2011) Hazır, Öncü; Shtub, A.
In this paper, we investigate the relationship between the information presentation format and project control. Furthermore, the effects of some system conditions, namely the number of projects to be controlled and the level of time pressure, on the quality of the project control decisions are analyzed. Information provided by Earned Value Analysis is used to monitor and control projects, and simulation is applied to replicate and model the uncertain project environments. Software is developed to generate random cost figures, to present the data in different visual forms and to collect users' responses. Having performed the experiments, the statistical significance of the results is tested. Journal of the Operational Research Society (2011) 62, 2157-2161. doi: 10.1057/jors.2011.11 Published online 2 March 2011
Citation Count: Öztürk, A., Gülgeç, M. (2011). Elastic-plastic stress analysis in a long functionally graded solid cylinder with fixed ends subjected to uniform heat generation. International Journal of Engineering Science, 49(10), 1047-1061. http://dx.doi.org/10.1016/j.ijengsci.2011.06.001
Elastic-plastic stress analysis in a long functionally graded solid cylinder with fixed ends subjected to uniform heat generation
(Pergamon-Elsevier Science Ltd, 2011) Öztürk, Ali; Gülgeç, Müfit; 4168
Elastic-plastic deformation of a solid cylinder with fixed ends, made of functionally graded material (FGM) with uniform internal heat generation is investigated, based on Tresca's yield criterion and its associated flow rule, considering four of the material properties to vary radially according to a parabolic form. These four material properties are yield strength, modulus of elasticity, coefficients of thermal conduction and thermal expansion, assumed to be independent of temperature as Poisson's ratio which is taken as constant. The materials which compose the functionally graded cylinder are supposed to be elastic-perfectly plastic materials. Expressions for the distributions of stress, strain and radial displacement are found analytically in terms of unknown interface radii. After determining these radii numerically by means of Mathematica 5.2, the distributions are plotted versus dimensionless radius, increasing heat generation, to compare the FGM cylinder with the homogeneous one. The numerical values used in this work for material parameters are arbitrarily chosen to point out the effect of the non-homogeneity on the stress distribution. The results obtained show that the stress distribution, as well as the development of plastic region radii, is influenced substantially by the material non-homogeneity
Citation Count: Schmidt, K., Breindl, C. (2011). Maximally permissive hierarchical control of decentralized discrete event systems. IEEE Transactions On Automatic Control, 56(4), 723-737. http://dx.doi.org/10.1109/TAC.2010.2067250
Maximally permissive hierarchical control of decentralized discrete event systems
(IEEE-INST Electrical Electronics Engineers INC, 2011) Schmidt, Klaus Werner; Breindl, Christian
The subject of this paper is the synthesis of natural projections that serve as nonblocking and maximally permissive abstractions for the hierarchical and decentralized control of large-scale discrete event systems. To this end, existing concepts for nonblocking abstractions such as natural observers and marked string accepting (msa)-observers are extended by local control consistency (LCC) as a novel sufficient condition for maximal permissiveness. Furthermore, it is shown that, similar to the natural observer condition and the msa-observer condition, also LCC can be formulated in terms of a quasi-congruence. Based on existing algorithms in the literature, this allows to algorithmically compute natural projections that are either natural observers or msa-observers and that additionally fulfill LCC. The obtained results are illustrated by the synthesis of nonblocking and maximally permissive supervisors for a manufacturing system
Citation Count: Evci, C., Gülgeç, M. (2012). An experimental investigation on the impact response of composite materials. International Journal of Impact Engineering, 43, 40-51.
An experimental investigation on the impact response of composite materials
(Pergamon-Elsevier Science Ltd, 2012) Evci, Celal; Gülgeç, Müfit; 243247; 4168
Due to the improved impact performance characteristics, composites are widely used in engineering and military applications to absorb the impact energy. Determination of impact response of composite materials provides the engineer and the manufacturer with critical knowledge to understand the failure criteria, initiation of the first failure and damage growth through the laminates. This study covers the investigation of impact damage growth and determination of Hertzian failure and maximum force thresholds in three different types of composites. Unidirectional E-Glass, woven E-Glass and woven Aramid composite samples with dimensions of 100 x 100 mm are subjected to low velocity impact with an instrumented impact test system. Rebound, on-set of perforation and perforation limits of composites are found out. Also, energy profile diagrams of both unidirectional and plain weave E-Glass composites are obtained. According to test results, woven composites are found to be superior to unidirectional composites in the protection limit of low velocity impact. It is also observed that damage growth in woven composites is restricted within a smaller area. Impact tests conclude that strength of the composite materials under dynamic loading increases considerably compared to static loading case as a result of strain rate sensitivity.
Citation Count: Boutalis, Yiannis; Moor, Thomas; Schmidt, Klaus (2012). "Fuzzy Hybrid Systems modeling with application in decision making and control", IS'2012 - 2012 6th IEEE International Conference Intelligent Systems, Proceedings, pp. 290-296.
Fuzzy Hybrid Systems modeling with application in decision making and control
(2012) Boutalis, Yiannis; Moor, Thomas; Schmidt, Klaus
Hybrid Systems are systems containing both discrete event and continuous variable components. Many recent contributions address crisp situations, where ambiguity or subjectivity in the measured data is absent. In this paper, we propose Fuzzy Hybrid Systems to account for inaccurate measurements and uncertain dynamics. We present a strategy to determine the most appropriate control actions in a sampled data setting. The proposed approach is based on three basic steps that are performed in each sampling period. First, the current discrete fuzzy state of the system is determined by a sensor evaluation. Next, the future discrete fuzzy state is predicted for the possible control actions and the best action, in respect to desired continuous states, is selected. Finally, the decision is cross-evaluated by a limited horizon prediction of the continuous system variables. The proposed method is explained and demonstrated for a variation of the a well-known two-tank scenario.
Citation Count: Kartal, Yusuf Bora; Schmidt, Ece Güran; Schmidt, Klaus Werner (2012). "The verification of a novel framework for real-time shared medium communication network protocols", 2012 20th Signal Processing and Communications Applications Conference, SIU 2012, Proceedings.
The verification of a novel framework for real-time shared medium communication network protocols
(2012) Kartal, Yusuf Bora; Schmidt, Ece Güran; Schmidt, Klaus Werner
The subject of this work is the real-time communication of the distributed industrial control applications over shared-medium Ethernet. We developed a framework for the real-time communication protocols over shared-medium Ethernet in our previous work. The framework is designed using the Timed Input/Output Automata formalism to serve the changing real-time communication needs of the embedded control applications. In this paper we present the modeling, simulation and formal verification process of the proposed framework using UPPAAL toolbox.
Citation Count: Schmidt, K.W., Boutalis, Y.S. (2012). Fuzzy discrete event systems for multiobjective control: framework and application to mobile robot navigation. IEEE Transactions On Fuzzy Systems, 20(5), 910-922. http://dx.doi.org/10.1109/TFUZZ.2012.2189219
Fuzzy discrete event systems for multiobjective control: framework and application to mobile robot navigation
(IEEE-Inst Electrical Electronics Engineers Inc, 2012) Schmidt, Klaus Werner; Boutalis, Yiannis S.
Fuzzy discrete event systems (FDESs) have been introduced in recent years to model systems whose discrete states or discrete state transitions can be uncertain and are, hence, determined by a possibility degree. This paper develops an FDES framework for the control of sampled data systems that have to fulfill multiple objectives. The choice of a fuzzy system representation is justified by the assumption of a controller realization that depends on various potentially imprecise sensor measurements. The proposed framework consists of three basic steps that are performed at each sampling instant. First, the current fuzzy state of the system is determined by a sensor evaluation. Second, the fuzzy state in the future sampling instant is predicted for all possible control actions of the system. Finally, an original multiobjective weighting strategy is proposed to determine the control action to be applied in the current sampling instant. The features of the proposed approach are demonstrated by a detailed mobile robot example, which includes a simulation study.
Citation Count: Kamacıoğlu, C., Baykal, Y. Generalized expression for optical source fields. Optics and Laser Technology, 44(6), 1706-1712. http://dx.doi.org/10.1016/j.optlastec.2012.01.008
Generalized expression for optical source fields
(Elsevier Science Ltd, 2012) Kamacıoğlu, Canan; Baykal, Yahya; 7812
A generalized optical beam expression is developed that presents the majority of the existing optical source fields such as Bessel, Laguerre-Gaussian, dark hollow, bottle, super Gaussian, Lorentz, super-Lorentz, flat-topped, Hermite-sinusoidal-Gaussian, sinusoidal-Gaussian, annular, Gauss-Legendre, vortex, also their higher order modes with their truncated, elegant and elliptical versions. Source intensity profiles derived from the generalized optical source beam fields are checked to match the intensity profiles of many individual known beam types. Source intensities for several interesting beam combinations are presented. Our generalized optical source beam field expression can be used to examine both the source characteristics and the propagation properties of many different optical beams in a single formulation
Citation Count: Gözcü, Ahmet Korhan...et al (2012). "The implementation of dynamic distributed real time industrial communication protocol (D 2RIP)", 2012 20th Signal Processing and Communications Applications Conference, SIU 2012, Proceedings.
The implementation of dynamic distributed real time industrial communication protocol (D 2RIP)
(2012) Gözcü, Ahmet Korhan; Turan, Ulaş; Schmidt, Ece Güran; Schmidt, Klaus Werner
Ethernet is a popular technology for industrial networking thanks to its low cost and high bandwidth. The current proposals to achieve real-time communication over Ethernet do not consider the determinism of the control applications resulting in inefficient use of bandwidth resources. We proposed a protocol stack architecture that works with standard Ethernet to address this problem. This paper describes the implementation of this architecture over Real-time Linux operating system and the first experiments to verify the operation. The implementation and performance of IEEE 1588 protocol which provides the required synchronization is also presented.
Citation Count: Schmidt, K.W., Schmidt, E.G. (2012). Distributed real-time protocols for industrial control systems: framework and examples. IEEE Transactions on Parallel And Distributed Systems, 23(10), 1856-1866. http://dx.doi.org/ 10.1109/TPDS.2011.300
Distributed real-time protocols for industrial control systems: framework and examples
(IEEE-Computer Soc, 2012) Schmidt, Klaus Werner; Schmidt, Ece Güran; 17337
The automation of today's large-scale industrial systems relies on the operation of distributed controller devices that perform local computations and exchange information via communication networks. The subject of this paper is the development of a family of shared-medium industrial communication protocols that support the transmission of real-time (RT) and nonreal-time (nRT) data among distributed controller devices. Different from existing protocols, we suggest to incorporate information that is available from the control application in the protocol definition. As a result, our protocols dynamically change the bandwidth allocation on the shared medium according to the instantaneous communication requirements while ensuring hard RT guarantees. Following the recent developments in industrial automation, our protocols can be realized as software layers on top of low-cost conventional Ethernet
Citation Count: Ozturk, Ali; Gulgec, Mufit, "Analytical Solution of Thermal Stresses in a Functionally Graded Solid Cylinder within Parabolic Continuous Grading", Mechatronics and Computational Mechanics, Vol. 307, pp. 364-, (2012)
Analytical Solution of Thermal Stresses In A Functionally Graded Solid Cylinder Within Parabolic Continuous Grading
(Trans Tech Publications LTD, 2012) Öztürk, Ali; Gülgeç, Müfit; 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.

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