Mechanical Engineering / Makina Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4129

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Active Fault Tolerant Control of a Wind Farm System
(IFAC Secretariat, 2018) Simani, Silvio; Turhan, Cihan
In order to enhance the 'sustainability’ of offshore wind farms, thus skipping unplanned maintenance operations and costs, that can be important for offshore systems, the earlier management of faults represents the key point. Therefore, this work studies the development of an adaptive sustainable control scheme with application to a wind farm benchmark consisting of nine wind turbine systems. They are described via their nonlinear models, as well as the wind and wake effects among the wind turbines of the wind park. The fault tolerant control strategy uses the recursive estimation of the faults provided by nonlinear estimators designed via a nonlinear differential algebraic tool. This aspect of the study, together with the more straightforward solution based on a data-driven scheme, is the key issue when on-line applications are proposed for a viable implementation of the proposed solutions.
Citation - WoS: 4
Citation - Scopus: 5
Active Heat Transfer Enhancement by Interface-Localized Liquid Dielectrophoresis Using Interdigitated Electrodes
(Elsevier, 2022-04) Yenigün, Onur; Barışık, Murat
We introduced an active heat transfer control between graphene and water using interdigitated electrodes (IDEs). Oppositely charged co-planer electrodes embedded on a graphene surface created a non-uniform electric field. Resulted interface localized liquid dielectrophoresis (LDEP) perpendicular to surface enhanced the water/graphene coupling and decreased interfacial thermal resistance (ITR) substantially. We correlated the theoretical calculations of average electric field strength near surface with Kapitza values measured at corresponding electrode configurations. We obtained a unified linear variation of Kapitza as a function of average electric strength independent of electrode size and charge. By increasing the electric field strength, we measured up to 96% decrease of Kapitza near electrodes. Since the IDEs generated electric field was only interface localized, it required lower electrode charges than any parallel-plate capacitor systems. We showed that ITR remains effective in heat transfer behavior for systems as big as 100nm such that interface localized electric field can at least increase the heat removal 50% by eliminating the ITR from both graphene/water interfaces of a channel system. By converting hydrophobic few-layer graphene to super-hydrophilic condition with ultra-low Kapitza, current results are important for graphene-based materials considered for the solution of the thermal management problem of current and next generation micro/nano-electronics.
Citation - Scopus: 2
Adaptive Actuator Failure Compensation for Concurrently Actuated Manipulators
(Elsevier, 2003) Keçeci, Emin Faruk; Tang, Xidong; Tao, Gang
This paper presents an adaptive actuator failure compensation method, which compensates for uncertainties due to unknown actuator failures and system dynamics, for a class of redundant manipulators where some joints concurrently actuated. Physical realization of concurrently actuated manipulators and their advantageous of use have been understood before, but adaptive failure compensation is still an open issue. In this research, failure formulation, controller structure and adaptive update rules for handling uncertainties from both the system dynamics and the failures are studied. The system stability is shown by a modified Lyapunov. Simulation results show the effectiveness of the proposed adaptive failure compensation control design.
Adaptive Actuator Failure Compensation for Cooperating Multiple Manipulator Systems
(Elsevier, 2003) Keçeci, Emin Faruk; Tang, Xidong; Tao, Gang
This paper presents adaptive actuator failure compensation for a cooperating multiple manipulator system with uncertain actuator failures in the task space. Advantages of designing control schemes in task spaces are emphasized, applications of task space control in robotics are discussed and a short review on control algorithms for cooperating multiple manipulator systems is given. Dynamic equations of motion of the multiple manipulator system in the task space are derived, and the adaptive actuator failure compensation problem is formulated. A compensation controller structure is proposed, for which adaptive parameter update laws are developed. The adaptive control scheme is able to compensate for the uncertainties arising from both the system parameters and the actuator failures. Based on Lyapunov stability analysis, the closed-loop signal boundedness and the convergence of the tracking error to zero are ensured. © 2003 International Federation of Automatic Control.
Citation - WoS: 6
Citation - Scopus: 12
Adaptive Actuator Failure Compensation for Redundant Manipulators
(Cambridge University Press, 2009-01) Keçeci, Emin Faruk; Tang, Xidong; Tao, Gang
This paper presents an adaptive actuator failure compensation method, which compensates for uncertainties due to unknown actuator failures for redundant manipulator systems. The method is first developed for manipulators whose joints are concurrently actuated. While physical realization of concurrently actuated manipulators and the advantages of their use have been understood before, in this paper failure modeling, controller structure, and adaptive update rules for handling uncertainties from the actuator failures are studied. The adaptive actuator failure compensation method is then expanded for a cooperating multiple manipulator system with uncertain actuator failures. Dynamic equations of such a multiple manipulator system in the task space are derived and the adaptive actuator failure compensation problem is formulated in the task space, for which a compensation controller structure is proposed with stable adaptive parameter update laws. The adaptive control scheme is able to compensate for the uncertainties of system parameters and actuator failures in a more general sense. For both cases, closed-loop system stability and asymptotic tracking are proved, despite uncertain system failures.
Citation - WoS: 1
Citation - Scopus: 1
Adaptive Signal Processing Strategy for a Wind Farm System Fault Accommodation
(Institute of Electrical and Electronics Engineers, 2018-03) Simani, Silvio; Turhan, Cihan
In order to enhance the 'sustainability' of offshore wind farms, thus skipping unplanned maintenance operations and costs, that can be important for offshore systems, the earlier management of faults represents the key point. Therefore, this work studies the development of an adaptive sustainable control scheme with application to a wind farm benchmark consisting of nine wind turbine systems. They are described via their nonlinear models, as well as the wind and wake effects among the wind turbines of the wind park. The fault tolerant (i.e., sustainable) control strategy uses the recursive estimation of the faults provided by nonlinear estimators designed via a nonlinear differential algebraic tool. These estimators are not affected by the model uncertainty and the wake effects among the wind turbines. This work exploits also a data-driven method used for estimating the analytical form of these disturbance functions, which are employed for obtaining the nonlinear fault reconstructors. Note that purely analytic approaches, where the model nonlinearity and the disturbance decoupling features are directly taken into account, may lead to more complex design tools. This aspect of the study, together with the more straightforward solution based on a data-driven scheme, is the issue when online applications are proposed for a viable implementation of the proposed solutions. The benchmark is exploited to verify the features of the developed strategies with respect to various fault situations and unavoidable model-reality mismatch.
Citation - WoS: 17
Citation - Scopus: 25
Adaptive Vehicle Skid Control
(Elsevier Ltd., 2006-06) Keçeci, Emin Faruk; Tao, Gang
In this paper, adaptive vehicle skid control, for stability and tracking of a vehicle during slippage of its wheels without braking, is addressed. Two adaptive control algorithms are developed: one for the case when no road condition information is available, and one for the case when certain information is known only about the instant type of road surface on which the vehicle is moving. The vehicle control system with an adaptive control law keeps the speed of the vehicle as desired by applying more power to the drive wheels where the additional driving force at the non-skidding wheel will compensate for the loss of the driving force at the skidding wheel, and also arranges the direction of the vehicle motion by changing the steering angle of the two front steering wheels. Stability analysis proves that the vehicle position and velocity errors are both bounded. With additional road surface information available, the adaptive control system guarantees that the vehicle position error and velocity error converge to zero asymptotically even if the road surface parameters are unknown.
Citation - WoS: 59
Citation - Scopus: 71
Additive and Intensive Grinding Effects on the Synthesis of Cordierite
(Elsevier Ltd., 2006) Yalamaç, Emre; Akkurt, Sedat
Cordierite was mechanochemically synthesized by mixing proper amounts of kaolin, talc and Al(OH)3. Full factorial experiments were planned, conducted, and the results were analyzed by the use of statistical techniques in order to understand the effects of process variables on the amount of synthesized product. The powder products were analyzed by XRD, DTA, and SEM-EDS. As a result of the statistical analysis, temperature was found to be the most important factor. Based on XRD peak intensity measurements, the cordierite mixture was completely amorphized by grinding at 300 rpm for 60 min. Cordierite was successfully produced at temperatures as low as 1150 °C by using the mixture after intensive grinding. The combined effect of magnesium borate additive and grinding on cordierite synthesis was also studied. These factors successfully decreased the synthesis temperature down to 1000 °C.
Citation - WoS: 6
Citation - Scopus: 7
Aerodynamic Optimization of Through-Flow Design Model of a High By-Pass Transonic Aero-Engine Fan Using Genetic Algorithm
(SAGE Publications Inc., 2018-05) Kor, Orçun; Acarer, Sercan; Özkol, Ünver
This study deals with aerodynamic optimization of a high by-pass transonic aero-engine fan module in a through-flow inverse design model at cruise condition. To the authors’ best knowledge, although the literature contains through-flow optimization of the simplified cases of compressors and turbines, an optimization study targeting the more elaborate case of combined transonic fan and splitter through-flow model is not considered in the literature. Such a through-flow optimization of a transonic fan, combined with bypass and core streams separated by an aerodynamically shaped flow splitter, possesses significant challenges to any optimizer, due to highly non-linear nature of the problem and the high number of constraints, including the fulfillment of the targeted bypass ratio. It is the aim of this study to consider this previously untouched area in detail and therefore present a more sophisticated and accurate optimization environment for actual bypass fan systems. An in-house optimization code using genetic algorithm is coupled with a previously developed in-house through-flow solver which is using a streamline curvature technique and a set of in-house calibrated empirical models for incidence, deviation, loss and blockage. As the through-flow models are the backbone of turbomachinery design, and great majority of design decisions are taken in this phase, such a study is assessed to result in significant guidelines to the gas turbine community.
Citation - WoS: 17
Citation - Scopus: 25
Air Leakage Measurement and Analysis in Duct Systems
(Elsevier Ltd., 2006-03) Aydın, Çiğdem; Özerdem, Barış
Air ducts and related equipments are used in a large number of buildings having thermal comfort. In this study, energy loss related with air leakage is studied. The leakage measurement setup was produced according to NEN-EN standards and the evaluation of data have been conducted by using power law model. The measurements were made on 300 and 1000 mm diameter single circular ducts, 300 mm × 250 mm and 1000 mm × 500 mm flanged joint rectangular ducts, 300 and 630 mm diameter circular beaded slip joint ducts, 300 mm × 200 mm and 500 mm × 300 mm rectangular flanged and drive slip joint ducts, and an branched air distribution system having different diameters for positive internal pressures. Test results have showed that the most of air leakage is from the joints. The seam contribution to air leakage is relatively lower than the joints. Using sealing gaskets help to improve the air leakage by about 50%.
Citation - WoS: 82
Citation - Scopus: 92
Airfoil Optimization for Noise Emission Problem and Aerodynamic Performance Criterion on Small Scale Wind Turbines
(Elsevier Ltd., 2012-10) Göçmen, Tuhfe; Özerdem, Barış
Noise emission is one of the major concerns in wind turbine industry and especially for small scale wind turbines, which are mostly erected to the urban areas; the concern is turning into a problem. This paper focuses on the optimization of six airfoils which are widely used on small scale wind turbines in terms of the noise emission and performance criteria and the numerical computations are performed for a typical 10 kW wind turbine. The main purpose of this optimization process is to decrease the noise emission levels while increasing the aerodynamic performance of a small scale wind turbine by adjusting the shape of the airfoil. The sources of the broadband noise emission are defined and their dominancy is investigated with respect to the operating conditions. While redesigning, together with the principals of reducing the airfoil self-noise, the aerodynamic prospects of increasing the performance have been taken into account. The codes which are based on aero-acoustic empirical models and a collection of well-known aerodynamic functions are used in this study. The results obtained from the numerical analysis of the optimization process have shown that, the considered commercial airfoils for small scale wind turbines are improved in terms of aero-acoustics and aerodynamics. The pressure sides of the baseline airfoils have been manipulated together with the trailing edge and redesigned airfoils have lower levels of noise emission and higher lift to drag ratios. © 2012 Elsevier Ltd.
Citation - WoS: 1
Citation - Scopus: 1
Alternating Error Effects on Decomposition Method in Function Generation Synthesis
(Springer Verlag, 2017) Maaroof, Omar W.; Dede, Mehmet Ismet Can; Kiper, Gokhan
In approximate function generation synthesis methods, error between the desired function's output and designed mechanism's output oscillate about zero error while crossing the zero error margin at precision points. The common goal of these methods is to minimize the error within the selected working region of the mechanism. For mechanisms like Bennett overconstrained six-revolute jointed linkages that have relatively large number of construction parameters, it is a difficult task to solve for them at once. Decomposition method enables to divide such linkages into two loops and independently solve for each loop with less construction parameters. Although some approximation methods are proven to produce smaller errors than others for a single-loop synthesis, in this work, it is shown that smaller errors are not guaranteed for a certain method when used along with decomposition method. Numerical examples indicate that in decomposition method, more attention should be given to the alternation of the error of each decomposed mechanism, rather than the approximation method used.
Citation - WoS: 1
Citation - Scopus: 2
Analysis and Application of Advanced Control Strategies To a Heating Element Nonlinear Model
(IOP Publishing Ltd., 2017) Turhan, Cihan; Simani, Silvio; Zajic, Ivan; Gökçen Akkurt, Gülden
This paper presents the design of different control strategies applied to a heating element nonlinear model. The description of this heating element was obtained exploiting a data-driven and physically meaningful nonlinear continuous-time model, which represents a test-bed used in passive air conditioning for sustainable housing applications. This model has low complexity while achieving high simulation performance. The physical meaningfulness of the model provides an enhanced insight into the performance and functionality of the system. In return, this information can be used during the system simulation and improved model- based and data-driven control designs for tight temperature regulation. The main purpose of this study is thus to give several examples of viable and practical designs of control schemes with application to this heating element model. Moreover, extensive simulations and Monte- Carlo analysis are the tools for assessing experimentally the main features of the proposed control schemes, in the presence of modelling and measurement errors. These developed control methods are also compared in order to evaluate advantages and drawbacks of the considered solutions. Finally, the exploited simulation tools can serve to highlight the potential application of the proposed control strategies to real air conditioning systems.
Analysis and Comparison of the Projectile Impact Response of an Electron Beam Melt-Ti64 Body Centered Cubic Lattice-Cored Sandwich Plate
(Springer, 2025) Erten, H.İ.; Çimen, G.; Yıldıztekin, F.M.; Güden, M.
Background: One potential application of additively fabricated lattice structures is in the blade containment rings of gas turbine engines. The blade containment rings are expected to be able to absorb the kinetic energy of a released blade (broken blade) in order to protect the engine parts from damaging. Metallic lattice-cored sandwich plates provide a gap (free space) between two face sheets, which helps to arrest the released blade and increases the energy absorption capability of containment rings. Objective: The objective was to investigate numerically the projectile impact response of Body-Centered-Cubic (BCC) Electron-Beam-Melt (EBM) lattice-cored/Ti64 face sheet sandwich plates as compared with that of an equal-mass monolithic EBM-Ti64 plate. Methods: The projectile impact simulations were implemented in LS-DYNA using the previously determined flow stress and damage models and a spherical steel impactor at the velocities ranging from 150 to 500 m s−1. The experimental projectile impact tests on the monolithic plate were performed at two different impact velocities and the results were used to confirm the validity of the used flow stress and damage models for the monolithic plate models. Results: Lower impact stresses were found numerically in the sandwich plate as compared with the monolithic plate at the same impact velocity. The bending and multi-cracking of the struts over a wide area in the sandwich plate increased the energy absorption and resulted in the arrest of the projectile at relatively high velocities. While monolithic plate exhibited a local bent area, resulting in the development of high tensile stresses and the projectile perforations at lower velocities. Conclusions: The numerical impact stresses in the sandwich plate were distributed over a wider area around the projectile, leading to the fracture and bending of many individual struts which significantly increased the resistance to the perforation. Hence, the investigated lattice cell topology and cell, strut, and face sheet sizes and the lattice-cored sandwich plate was shown potentially more successful in stopping the projectiles than the equal-mass monolithic plates. © The Author(s) 2025.
Citation - WoS: 6
Citation - Scopus: 11
Analysis of Adhesively Bonded Joints of Laser Surface Treated Composite Primary Components of Aircraft Structures
(Elsevier, 2023) Martin, Seçkin; Nuhoğlu, Kaan; Aktaş, Engin; Tanoğlu, Metin; İplikçi, Hande; Barışık, Murat; Yeke, Melisa; Türkdoğan, Ceren; Esenoğlu, Gözde; Dehneliler, Serkan
The performance of the adhesively bonded aerospace structures highly depends on the adhesion strength between the adhesive and adherents, which is affected by, in particular, the condition of the bonding surface. Among the various surface treatment methods, as state of the art, laser surface treatment is a suitable option for the CFRP composite structures to enhance the adhesion performance, adjusting the roughness and surface free energy with relatively minimizing the damage to the fibers. The aim of this study is the validation and evaluation of the adhesive bonding behavior of the laser surface-treated CFRP composite structures, using the finite element technique to perform a conservative prediction of the failure load and damage growth. Such objectives were achieved by executing both experimental and numerical analyses of the secondary bonded CFRP parts using a structural adhesive. In this regard, to complement physical experiments by means of numerical simulation, macro-scale 3D FEA of adhesively bonded Single Lap Joint and Skin-Spar Joint specimens has been developed employing the Cohesive Zone Model (CZM) technique in order to simulate bonding behavior in composite structures especially skin-spar relation in the aircraft wing-box.
Analytical Dynamic Analysis of a Kinesthetic Haptic Device
(Dokuz Eylül Üniversitesi, 2018-05) Dede, Mehmet İsmet Can; Maaroof, Omar Waleed Najm; Ceccarelli, Marco
A hybrid-structured kinesthetic haptic device based on an R-CUBE mechanism and a serial spherical wrist mechanism is considered in this article. This device is designed to simulate point-type contacts on the user. Hence, only three-dimensional forces are simulated to the user through the R-CUBE mechanism. This paper presents the quasi-static force analysis, gravity compensation calculations and dynamic analysis of the R-CUBE mechanism to serve for better understanding the capabilities of the mechanism and to be used in haptics controller development in the future studies. Making use of the derived dynamic equations, torque requirements from the actuators are examined for use in the haptic application scenarios.
Citation - WoS: 4
Citation - Scopus: 4
Analytical Solution of Micro-/Nanoscale Convective Liquid Flows in Tubes and Slits
(Springer, 2017) Kalyoncu, Gülce; Barışık, Murat
Analytical solutions examining heat transport in micro-/nanoscale liquid flows were developed. Using the energy equation coupled with fully developed velocity, we solved developing temperature profiles with axial conduction and viscous dissipation terms. A comprehensive literature review provided the published range of velocity slip and temperature jump conditions. While molecular simulations and experiments present constant slip and jump values for a specific liquid/surface couple independent of confinement size, non-dimensional forms of these boundary conditions were found appropriate to calculate non-equilibrium as a function of flow height. Although slip and jump conditions are specific for each liquid/surface couple and hard to obtain, we proposed modeling of the slip and jump as a function of the surface wetting, in order to create a general, easy to measure methodology. We further developed possible correlations to calculate jump using the slip value of the corresponding surface and tested in the results. Fully developed Nu showed strong dependence on slip and jump. Heat transfer stopped when slip and jump coefficients became higher than a certain value. Strong variation of Nu in the thermal development length was observed for low slip and jump cases, while an almost constant Nu in the flow direction was found for high slip and jump coefficients. Variation of temperature profiles was found to dominate the heat transfer through the constant temperature surface while surface and liquid temperatures became equal at heat transfer lengths comparable with confinement sizes for no-dissipation cases. In case of non-negligible heat dissipation, viscous heating dominated the Nu value by enhancing the heating while decreasing the heat removal in cooling cases. Implementation of proposed procedure on a micro-channel convection problem from a micro-fluidics application showed the dominant effect of the model defining the slip and jump relationship. Direct use of kinetic gas theory resulted in an increase of Nu by an increase in non-equilibrium, while models developed from published liquid slip and jump values produced an opposite behavior.
Citation - WoS: 27
Citation - Scopus: 31
Analytical Solution of Thermally Developing Microtube Heat Transfer Including Axial Conduction, Viscous Dissipation, and Rarefaction Effects
(Elsevier Ltd., 2015-10) Barışık, Murat; Yazıcıoğlu, Almıla Güvenç; Çetin, Barbaros; Kakaç, Sadık
The solution of extended Graetz problem for micro-scale gas flows is performed by coupling of rarefaction, axial conduction and viscous dissipation at slip flow regime. The analytical coupling achieved by using Gram-Schmidt orthogonalization technique provides interrelated appearance of corresponding effects through the variation of non-dimensional numbers. The developing temperature field is determined by solving the energy equation locally together with the fully developed flow profile. Analytical solutions of local temperature distribution, and local and fully developed Nusselt number are obtained in terms of dimensionless parameters: Peclet number, Knudsen number, Brinkman number, and the parameter Kappa accounting temperature-jump. The results indicate that the Nusselt number decreases with increasing Knudsen number as a result of the increase of temperature jump at the wall. For low Peclet number values, temperature gradients and the resulting temperature jump at the pipe wall cause Knudsen number to develop higher effect on flow. Axial conduction should not be neglected for Peclet number values less than 100 for all cases without viscous dissipation, and for short pipes with viscous dissipation. The effect of viscous heating should be considered even for small Brinkman number values with large length over diameter ratios. For a fixed Kappa value, the deviation from continuum increases with increasing rarefaction, and Nusselt number values decrease with an increase in Knudsen number.
Citation - WoS: 45
Citation - Scopus: 57
Analytical Synthesis of Function Generating Spherical Four-Bar Mechanism for the Five Precision Points
(Elsevier Ltd., 2005) Alizade, Rasim I.; Alizade, Rasim; Kilit, Özgür
This paper presents an analytical method for synthesis of function generating spherical 4R mechanisms for the five precision points. For the design requirements an additional parameter, reference value of output angle, ψ0, was added to angular link length parameters, α i(i = 1, ..., 4). In the dimensional synthesis procedure, a novel approach of polynomial approximation method was proposed to determine these five design parameters. Using this method, a set of five non-linear equations was easily transformed into a set of fifteen linear equations. Hence, the problem was reduced to the solution of a cubic polynomial equation. Moreover, a graphical method in a CAD environment is proposed to verify the solutions. © 2005 Elsevier Ltd. All rights reserved.
Citation - WoS: 10
Citation - Scopus: 18
Ann Model for Prediction of Powder Packing
(Elsevier Ltd., 2007) Sütçü, Mücahit; Akkurt, Sedat
A multilayer feed forward backpropagation (MFFB) learning algorithm was used as an artificial neural network (ANN) tool to predict packing of fused alumina powder mixtures of three different sizes in green state. The data used in model construction were collected by mixing and pressing powders with average particle sizes of 350, 30 and 3 μm and with narrow particle size distributions. The data sets that were composed of green densities of cylindrical pellets were first randomly partitioned into two for training and testing of the ANN models. Based on the training data an ANN model of the packing efficiencies was created with low average error levels (3.36%). Testing of the model was also performed with successfully good average error levels of 3.39%.