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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Electrical Engineering and Technology
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The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 11, Issue 4 - Jul 2016
Volume 11, Issue 3 - May 2016
Volume 11, Issue 2 - Mar 2016
Volume 11, Issue 1 - Jan 2016
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Adaptive Firefly Algorithm based OPF for AC/DC Systems
Babu, B. Suresh ; Palaniswami, S. ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 791~800
DOI : 10.5370/JEET.2016.11.4.791
Optimal Power Flow (OPF) is an important operational and planning problem in minimizing the chosen objective functions of the power systems. The recent developments in power electronics have enabled introduction of dc links in the AC power systems with a view of making the operation more flexible, secure and economical. This paper formulates a new OPF to embrace dc link equations and presents a heuristic optimization technique, inspired by the behavior of fireflies, for solving the problem. The solution process involves AC/DC power flow and uses a self adaptive technique so as to avoid landing at the suboptimal solutions. It presents simulation results of IEEE test systems with a view of demonstrating its effectiveness.
Damping for Wind Turbine Electrically Excited Synchronous Generators
Tianyu, Wang ; Guojie, Li ; Yu, Zhang ; Chen, Fang ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 801~809
DOI : 10.5370/JEET.2016.11.4.801
The electrically excited synchronous generator (EESG) is applied in wind turbine systems recently. In an EESG control system, electrical torque is affected by stator flux and rotor current. So the control system is more complicated than that of the permanent-magnet synchronous generator (PMSG). Thus, the higher demanding of the control system is required especially in case of wind turbine mechanical resonance. In this paper, the mechanism of rotor speed resonant phenomenon is introduced from the viewpoint of mechanics firstly, and the characteristics of an effective damping torque are illustrated through system eigenvalues analysis. Considering the variables are tightly coupled, the four-order small signal equation for torque is derived considering stator and rotor control systems with regulators, and the bode plot of the closed loop transfer function is analyzed. According to the four-order mathematical equation, the stator flux, stator current, and electrical torque responses are derived by torque reference step and ramp in MATLAB from a pure mathematical deduction, which is identical with the responses in PSCAD/EMTDC simulation results. At last, the simulation studies are carried out in PSCAD software package to verify the resonant damping control strategy used in the EESG wind turbine system.
Optimal Scheduling of Electric Vehicles Charging in low-Voltage Distribution Systems
Xu, Shaolun ; Zhang, Liang ; Yan, Zheng ; Feng, Donghan ; Wang, Gang ; Zhao, Xiaobo ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 810~819
DOI : 10.5370/JEET.2016.11.4.810
Uncoordinated charging of large-scale electric vehicles (EVs) will have a negative impact on the secure and economic operation of the power system, especially at the distribution level. Given that the charging load of EVs can be controlled to some extent, research on the optimal charging control of EVs has been extensively carried out. In this paper, two possible smart charging scenarios in China are studied: centralized optimal charging operated by an aggregator and decentralized optimal charging managed by individual users. Under the assumption that the aggregators and individual users only concern the economic benefits, new load peaks will arise under time of use (TOU) pricing which is extensively employed in China. To solve this problem, a simple incentive mechanism is proposed for centralized optimal charging while a rolling-update pricing scheme is devised for decentralized optimal charging. The original optimal charging models are modified to account for the developed schemes. Simulated tests corroborate the efficacy of optimal scheduling for charging EVs in various scenarios.
A Priority Index Method for Efficient Charging of PEVs in a Charging Station with Constrained Power Consumption
Kim, Seung Wan ; Jin, Young Gyu ; Song, Yong Hyun ; Yoon, Yong Tae ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 820~828
DOI : 10.5370/JEET.2016.11.4.820
The sizable electrical load of plug-in electric vehicles may cause a severe low-voltage problem in a distribution network. The voltage drop in a distribution network can be mitigated by limiting the power consumption of a charging station. Then, the charging station operator needs a method for appropriately distributing the restricted power to all plug-in electric vehicles. The existing approaches have practical limitation in terms of the availability of future information and the execution time. Therefore, this study suggests a heuristic method based on priority indexes for fairly distributing the constrained power to all plug-in electric vehicles. In the proposed method, PEVs are ranked using the priority index, which is determined in real time, such that a near-optimal solution can be obtained within a short computation time. Simulations demonstrate that the proposed method is effective in implementation, although its performance is slightly worse than that of the optimal case.
Trade-Off Strategies in Designing Capacitor Voltage Balancing Schemes for Modular Multilevel Converter HVDC
Nam, Taesik ; Kim, Heejin ; Kim, Sangmin ; Son, Gum Tae ; Chung, Yong-Ho ; Park, Jung-Wook ; Kim, Chan-Ki ; Hur, Kyeon ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 829~838
DOI : 10.5370/JEET.2016.11.4.829
This paper focuses on the engineering trade-offs in designing capacitor voltage balancing schemes for modular multilevel converters (MMC) HVDC: regulation performance and switching loss. MMC is driven by the on/off switch operation of numerous submodules and the key design concern is balancing submodule capacitor voltages minimizing switching transition among submodules because it represents the voltage regulation performance and system loss. This paper first introduces the state-of-the-art MMC-HVDC submodule capacitor voltage balancing methods reported in the literatures and discusses the trade-offs in designing these methods for HVDC application. This paper further proposes a submodule capacitor balancing scheme exploiting a control signal to flexibly interchange between the on-state and the off-state submodules. The proposed scheme enables desired performance-based voltage regulation and avoids unnecessary switching transitions among submodules, consequently reducing the switching loss. The flexibility and controllability particularly fit in high-level MMC HVDC applications where the aforementioned design trade-offs become more crucial. Simulation studies for MMC HVDC are performed to demonstrate the validity and effectiveness of the proposed capacitor voltage balancing algorithm.
Energy Management of a Grid-connected High Power Energy Recovery Battery Testing System
Zhang, Ke ; Long, Bo ; Yoo, Cheol-Jung ; Noh, Hye-Min ; Chang, Young-Won ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 839~847
DOI : 10.5370/JEET.2016.11.4.839
Energy recovery battery testing systems (ERBTS) have been widely used in battery manufactures. All the ERBTS are connected in parallel which forms a special and complicated micro-grid system, which has the shortcomings of low energy recovery efficiency, complex grid-connected control algorithms issues for islanded detection, and complicated power circuit topology issues. To solve those shortcomings, a DC micro-grid system is proposed, the released testing energy has the priority to be reutilized between various testing system within the local grid, Compared to conventional scheme, the proposed system has the merits of a simplified power circuit topology, no needs for synchronous control, and much higher testing efficiency. The testing energy can be cycle-used inside the local micro-grid. The additional energy can be recovered to AC-grid. Numerous experimental comparison results between conventional and proposed scheme are provided to demonstrate the validity and effectiveness of the proposed technique.
A Clustering-Based Fault Detection Method for Steam Boiler Tube in Thermal Power Plant
Yu, Jungwon ; Jang, Jaeyel ; Yoo, Jaeyeong ; Park, June Ho ; Kim, Sungshin ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 848~859
DOI : 10.5370/JEET.2016.11.4.848
System failures in thermal power plants (TPPs) can lead to serious losses because the equipment is operated under very high pressure and temperature. Therefore, it is indispensable for alarm systems to inform field workers in advance of any abnormal operating conditions in the equipment. In this paper, we propose a clustering-based fault detection method for steam boiler tubes in TPPs. For data clustering, k-means algorithm is employed and the number of clusters are systematically determined by slope statistic. In the clustering-based method, it is assumed that normal data samples are close to the centers of clusters and those of abnormal are far from the centers. After partitioning training samples collected from normal target systems, fault scores (FSs) are assigned to unseen samples according to the distances between the samples and their closest cluster centroids. Alarm signals are generated if the FSs exceed predefined threshold values. The validity of exponentially weighted moving average to reduce false alarms is also investigated. To verify the performance, the proposed method is applied to failure cases due to boiler tube leakage. The experiment results show that the proposed method can detect the abnormal conditions of the target system successfully.
A 3 kW Bidirectional DC-DC Converter for Electric Vehicles
Ansari, Arsalan ; Cheng, Puyang ; Kim, Hee-Jun ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 860~868
DOI : 10.5370/JEET.2016.11.4.860
A bidirectional DC-DC converter (BDC) is an indispensable electrical unit for the electric vehicles (EVs). High efficiency, high power density, isolation, light weight and reliability are all essential requirements for BDC. In this paper, a 3 kW BDC for the battery charger of EVs is proposed. The proposed converter consists of a half-bridge structure on the primary side and an isolation transformer and a synchronous rectifier structure on the secondary side. With this topology, minimum number of switching devices are required for bidirectional power flow between the two dc buses of EVs. The easy implementation of the synchronous rectification gives advantages in terms of efficiency, cost and flexibility. The proposed BDC achieves high efficiency when operating in both modes (step-up and step-down). A 3 kW prototype is implemented to verify theoretical analysis and the performance of the proposed converter.
ARIMA Based Wind Speed Modeling for Wind Farm Reliability Analysis and Cost Estimation
Rajeevan, A.K. ; Shouri, P.V ; Nair, Usha ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 869~877
DOI : 10.5370/JEET.2016.11.4.869
Necessity has compelled man to improve upon the art of tapping wind energy for power generation; an apt reliever of strain exerted on the non-renewable fossil fuel. The power generation in a Wind Farm (WF) depends on site and wind velocity which varies with time and season which in turn determine wind power modeling. It implies, the development of an accurate wind speed model to predict wind power fluctuations at a particular site is significant. In this paper, Box-Jenkins ARIMA (Auto Regressive Integrated Moving Average) time series model for wind speed is developed for a 99MW wind farm in the southern region of India. Because of the uncertainty in wind power developed, the economic viability and reliability of power generation is significant. Life Cycle Costing (LCC) method is used to determine the economic viability of WF generated power. Reliability models of WF are developed with the help of load curve of the utility grid and Capacity Outage Probability Table (COPT). ARIMA wind speed model is used for developing COPT. The values of annual reliability indices and variations of risk index of the WF with system peak load are calculated. Such reliability models of large WF can be used in generation system planning.
Cogging Torque Reduction in Line Start Permanent Magnet Synchronous Motor
Behbahanifard, Hamidreza ; Sadoughi, Alireza ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 878~888
DOI : 10.5370/JEET.2016.11.4.878
Cogging torque has a negative impact on the operation of permanent magnet machines by increasing torque ripple, speed ripple, acoustic noise and vibration. In this paper Magnet Shifting Method has been used as a tool to reduce the cogging torque in inset Line Start Permanent Magnet Synchronous Motor (LSPMSM). It has been shown that Magnet Shifting Method can effectively eliminate several lower-order harmonics of cogging torque. In order to implement the method, first the expression of cogging torque is studied based on the Fourier analysis. An analytical expression is then introduced based on Permanent Magnet Shifting to reduce cogging torque of LSPMS motors. The method is applied to some existing machine designs and their performances are obtained using Finite Element Analysis (FEA). The effect of magnet shifting on pole mmf (magneto motive force) distribution in air gap is discussed. The side effects of magnet shifting on back-EMF, core losses and torque profile distortion are taken into account in this investigation. Finally the experimental results on two prototypes 24 slot 4 pole inset LSPMS motors have been used to validate the theoretical analysis.
Compensation Method of Position Signal Error with Misaligned Hall-Effect Sensors of BLDC Motor
Park, Joon Sung ; Choi, Jun-Hyuk ; Lee, Ju ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 889~897
DOI : 10.5370/JEET.2016.11.4.889
This paper presents an improved approach for compensating rotor position signal displacement in brushless DC (BLDC) motors with misaligned hall-effect sensors. Typically, the hall-effect sensors in BLDC motors are located in each phase and positioned exactly 120 electrical degrees apart. However, limitations in mechanical tolerances make it difficult to place hall-effect sensors at the correct location. In this paper, a position error compensator to counteract the hall-effect sensor positioning error is proposed. The proposed position error compensator uses least squares error analysis to adjust the relative position error and back-EMF information to reduce the absolute offset error. The effectiveness of the proposed approach is verified through several experiments.
Characteristic Analysis and Experimental Verification of the Axially Asymmetric Structured Outer-Rotor Type Permanent Magnet Motor
Seo, Myung-Ki ; Lee, Tae-Yong ; Park, Kyungsoo ; Kim, Yong-Jae ; Jung, Sang-Yong ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 898~904
DOI : 10.5370/JEET.2016.11.4.898
In this study, we have dealt with a design characteristic of outer-rotor type permanent magnet (PM) motor applied for Engine Cooling Fan (ECF). When we design a motor with structure like this type, it is required as a requisite to consider 3-Dimensional (3-D) effect by implementing a non-linear Finite Element Analysis (FEA) due to a yoke-ceiling, which is perpendicular to the axis of rotation. We have analyzed identical models under three different conditions. The analysis has been performed through a non-linear 2-Dimensional (2-D) and 3-D FEA. Finally, the results have been compared with Back Electro-Motive Force (BEMF) value of actual motor model. As a result, a yoke-ceiling function as an additional flux path and the operating point on B-H curve of rotor material is shifted to non-saturation region relatively. Accordingly, magnetic flux linkage can be increased and motor size can be decreased under same input condition to satisfy ECF specification, such as torque.
A Phase Current Reconstruction Technique Using a Single Current Sensor for Interleaved Three-phase Bidirectional Converters
Lee, Young-Jin ; Cho, Younghoon ; Choe, Gyu-Ha ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 905~914
DOI : 10.5370/JEET.2016.11.4.905
This paper proposes a new phase current reconstruction technique for interleaved three-phase bidirectional dc-dc converters using a single current sensor. In the proposed current reconstruction algorithm, a single current sensor is employed at the dc-link, and the dc-link current information is sampled at either the peak or valley point of the pulse-width modulation (PWM) carriers regularly. From the obtained current information, all phase currents are reconstructed in a single PWM cycle. After that, the digital current controller is applied to achieve current balancing in each phase. Compare to the previous multiple current sensor method, the proposed strategy reduces the number of the current sensors in the interleaved three-phase bidirectional converter as well as reducing potential current sensing error caused by non-ideal characteristics of the multiple current sensors. The effectiveness of the proposed method is verified from the experiments based on a 3kW three-phase bidirectional converter prototype for the automotive battery charging application.
Systematic Topology Selection Method for Multiple-Input DC-DC Converters
Choung, Seung H. ; Bae, Sungwoo ; Kim, Myungchin ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 915~920
DOI : 10.5370/JEET.2016.11.4.915
A power system designer may have difficulties in choosing a suitable multiple-input converter topology for a specific target application because each multiple-input converter topology presented in the literature has its own advantages and disadvantages. In this perspective, this paper presents a systematic topology selection method for multiple-input converters with three comparison criteria including cost-saving effect, modularity potential and flexibility. Based on these criteria, this paper proposes a strategic flow chart example for choosing a proper multiple-input converter topology. This flow chart will provide a powerful selection tool to a power system designer when he or she chooses a specific multiple-input converter for a given application.
Design and Control Method for Sub-module DC Voltage Ripple of HVDC-MMC
Gwon, Jin-Su ; Park, Jung-Woo ; Kang, Dea-Wook ; Kim, Sungshin ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 921~930
DOI : 10.5370/JEET.2016.11.4.921
This paper proposes a design and control method for a high-voltage direction current modular multilevel converter (HVDC-MMC) considering the capacitor voltage ripple of the submodule (SM). The capacitor voltage ripple consists of the line frequency and double-line-frequency components. The double line- frequency component does not fluctuate according to the active power, whereas the line-frequency component is highly influenced by the grid-side voltage and current. If the grid voltage drops, a conventional converter increases the current to maintain the active power. A grid voltage drops, current increment, or both occur with a capacitor voltage ripple higher than the limit value. In order to reliably control an MMC within a limit value, the SM capacitor should be designed on the basis of the capacitor voltage ripple. In this paper, the capacitor voltage ripple according to the grid voltage and current are analyzed, and the proposed control method includes a current limitation method considering the capacitor voltage ripple. The proposed design and control method are verified through simulation using PSCAD/EMTDC.
Position Estimator Employing Kalman Filter for PM Motors Driven with Binary-type Hall Sensors
Lee, Dong-Myung ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 931~938
DOI : 10.5370/JEET.2016.11.4.931
Application of vector control scheme for consumer products is enlarging to improve control performance. For the field-oriented control, accurate position detection is essential and generally requires expensive sensors. On the other hand, cost-reduction is important in home appliances, so that binary-type Hall-effect sensors are commonly used rather than using an expensive sensor such as an encoder. The control performance is directly influenced by the accuracy of the position information, and there exist non-uniformities related to Hall sensors in electrical and mechanical aspects, which result in distorted position information. Therefore, to get high-precision position information from low-resolution Hall sensors, this paper proposes a new position estimator consisting of a Kalman filter and feedforward compensation scheme, which generates a linearly changing position signal. The efficacy of the proposed scheme is verified by simulation and experimental results carried out with a 48-pole permanent magnet motor.
Low Reverse Saturation Current Density of Amorphous Silicon Solar Cell Due to Reduced Thickness of Active Layer
Iftiquar, S M ; Yi, Junsin ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 939~942
DOI : 10.5370/JEET.2016.11.4.939
One of the most important characteristic curves of a solar cell is its current density-voltage (J-V) curve under AM1.5G insolation. Solar cell can be considered as a semiconductor diode, so a diode equivalent model was used to estimate its parameters from the J-V curve by numerical simulation. Active layer plays an important role in operation of a solar cell. We investigated the effect thicknesses and defect densities (N
) of the active layer on the J-V curve. When the active layer thickness was varied (for N
) from 800 nm to 100 nm, the reverse saturation current density (J
) changed from 3.56×10
and its ideality factor (n) changed from 5.28 to 2.02. For a reduced defect density (N
), the n remained within 1.45≤n≤1.92 for the same thickness range. A small increase in shunt resistance and almost no change in series resistance were observed in these cells. The low reverse saturation current density (J
) and diode ideality factor (n = 2.02 or 1.45) were observed for amorphous silicon based solar cell with 100 nm thick active layer.
Using of Scattering Bond Graph Methodology for a Physical Characteristics Analysis of “D-CRLH” Transmission Line
Taghouti, Hichem ; Jmal, Sabri ; Mami, Abdelkader ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 943~950
DOI : 10.5370/JEET.2016.11.4.943
In this paper, we propose to analyze the physical characteristics of a planar dual-composite right-left handed transmission line by a common application of Bond Graph approach and Scattering formalism (Methodology S.BG). The technique, we propose consists, on the one hand, of modeling of a dual composite right-left metamaterial transmission line (D-CRLH-TL) by Bond Graph approach, and, it consists of extracting the equivalent circuit of this studied structure. On the other hand, it consists to exploiting the scattering parameters (Scattering matrix) of the DCRLH-TL using the methodology which we previously developed since 2009. Finally, the validation of the proposed and used technique is carried out by comparisons between the simulations results with ADS and Maple (or MatLab).
A Random Forest Model Based Pollution Severity Classification Scheme of High Voltage Transmission Line Insulators
Kannan, K. ; Shivakumar, R. ; Chandrasekar, S. ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 951~960
DOI : 10.5370/JEET.2016.11.4.951
Tower insulators in electric power transmission network play a crucial role in preserving the reliability of the system. Electrical utilities frequently face the problem of flashover of insulators due to pollution deposition on their surface. Several research works based on leakage current (LC) measurement has been already carried out in developing diagnostic techniques for these insulators. Since the LC signal is highly intermittent in nature, estimation of pollution severity based on LC signal measurement over a short period of time will not produce accurate results. Reports on the measurement and analysis of LC signals over a long period of time is scanty. This paper attempts to use Random Forest (RF) classifier, which produces accurate results on large data bases, to analyze the pollution severity of high voltage tower insulators. Leakage current characteristics over a long period of time were measured in the laboratory on porcelain insulator. Pollution experiments were conducted at 11 kV AC voltage. Time domain analysis and wavelet transform technique were used to extract both basic features and histogram features of the LC signal. RF model was trained and tested with a variety of LC signals measured over a lengthy period of time and it is noticed that the proposed RF model based pollution severity classifier is efficient and will be helpful to electrical utilities for real time implementation.
Effects of Non-uniform Pollution on the AC Flashover Performance of Suspension Insulators
Zhijin, Zhang ; Jiayao, Zhao ; Donghong, Wei ; Xingliang, Jiang ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 961~968
DOI : 10.5370/JEET.2016.11.4.961
The non-uniform distribution of contamination on insulator surface has appreciable effects on flashover voltage, and corresponding researches are valuable for the better selection of outdoor insulation. In this paper, two typical types of porcelain and glass insulators which are widely used in ac lines were taken as the research subjects, and their corrections of AC flashover voltage under non-uniform pollution were studied. Besides, their flashover characteristics under different ratio (T/B) of top to bottom surface salt deposit density (SDD) were investigated, including the analysis of flashover voltage, surface pollution layer conductivity and critical leakage current. Test results gave the modified formulas for predicting flashover voltage of the two samples, which can be directly applied in the transmission line design. Also, the analysis delivered that, the basic reason why the flashover voltage increases with the decrease of T/B, is due to the decrease of equivalent surface conductivity of the whole surface and the decrease of critical leakage current. This research will be of certain value in providing references for outdoor insulation selection, as well as in proposing more information for revealing pollution flashover mechanism.
Thermal Recovery Characteristics of a CO
Mixture Gas Circuit Breaker
Oh, Yeon-Ho ; Song, Ki-Dong ; Lee, Hae-June ; Hahn, Sung-Chin ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 969~973
DOI : 10.5370/JEET.2016.11.4.969
Interruption tests were conducted using the same circuit breaker for an initial pressure of SF
0.5 MPa (gauge pressure) and CO
mixture 1.0 MPa, 0.8 MPa, and 0.6 MPa. The pressure-rises in the compression and thermal expansion chambers were measured for verifying the computational results using a simplified synthetic test facility. Further, the possibility of the CO
mixture substituting SF
gas was confirmed. Moreover, in view of the thermal recovery capability, it has also been confirmed that the pressure of the CO
mixture can be reduced almost to the same value as that of the SF
gas by optimizing the design parameters of the interrupter.
Reversible Data Hiding Using a Piecewise Autoregressive Predictor Based on Two-stage Embedding
Lee, Byeong Yong ; Hwang, Hee Joon ; Kim, Hyoung Joong ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 974~986
DOI : 10.5370/JEET.2016.11.4.974
Reversible image watermarking, a type of digital data hiding, is capable of recovering the original image and extracting the hidden message with precision. A number of reversible algorithms have been proposed to achieve a high embedding capacity and a low distortion. While numerous algorithms for the achievement of a favorable performance regarding a small embedding capacity exist, the main goal of this paper is the achievement of a more favorable performance regarding a larger embedding capacity and a lower distortion. This paper therefore proposes a reversible data hiding algorithm for which a novel piecewise 2D auto-regression (P2AR) predictor that is based on a rhombus-embedding scheme is used. In addition, a minimum description length (MDL) approach is applied to remove the outlier pixels from a training set so that the effect of a multiple linear regression can be maximized. The experiment results demonstrate that the performance of the proposed method is superior to those of previous methods.
Energy Aware Task Scheduling for a Distributed MANET Computing Environment
Kim, Jaeseop ; Kim, Jong-Kook ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 987~992
DOI : 10.5370/JEET.2016.11.4.987
This study introduces an example environment where wireless devices are mobile, devices use dynamic voltage scaling, devices and tasks are heterogeneous, tasks have deadline, and the computation and communication power is dynamically changed for energy saving. For this type of environment, the efficient system-level energy management and resource management for task completion can be an essential part of the operation and design of such systems. Therefore, the resources are assigned to tasks and the tasks may be scheduled to maximize a goal which is to minimize energy usage while trying to complete as many tasks as possible by their deadlines. This paper also introduces mobility of nodes and variable transmission power for communication which complicates the resource management/task scheduling problem further.
An Automatic Diagnosis System for Hepatitis Diseases Based on Genetic Wavelet Kernel Extreme Learning Machine
Avci, Derya ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 993~1002
DOI : 10.5370/JEET.2016.11.4.993
Hepatitis is a major public health problem all around the world. This paper proposes an automatic disease diagnosis system for hepatitis based on Genetic Algorithm (GA) Wavelet Kernel (WK) Extreme Learning Machines (ELM). The classifier used in this paper is single layer neural network (SLNN) and it is trained by ELM learning method. The hepatitis disease datasets are obtained from UCI machine learning database. In Wavelet Kernel Extreme Learning Machine (WK-ELM) structure, there are three adjustable parameters of wavelet kernel. These parameters and the numbers of hidden neurons play a major role in the performance of ELM. Therefore, values of these parameters and numbers of hidden neurons should be tuned carefully based on the solved problem. In this study, the optimum values of these parameters and the numbers of hidden neurons of ELM were obtained by using Genetic Algorithm (GA). The performance of proposed GA-WK-ELM method is evaluated using statical methods such as classification accuracy, sensitivity and specivity analysis and ROC curves. The results of the proposed GA-WK-ELM method are compared with the results of the previous hepatitis disease studies using same database as well as different database. When previous studies are investigated, it is clearly seen that the high classification accuracies have been obtained in case of reducing the feature vector to low dimension. However, proposed GA-WK-ELM method gives satisfactory results without reducing the feature vector. The calculated highest classification accuracy of proposed GA-WK-ELM method is found as 96.642 %.
Hole Filling Algorithm for a Virtual-viewpoint Image by Using a Modified Exemplar Based In-painting
Ko, Min Soo ; Yoo, Jisang ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 1003~1011
DOI : 10.5370/JEET.2016.11.4.1003
In this paper, a new algorithm by using 3D warping technique to effectively fill holes that are produced when creating a virtual-viewpoint image is proposed. A hole is defined as the region that cannot be seen in the reference view when a virtual view is created. In the proposed algorithm, to reduce the blurring effect that occurs on the hole region filled by conventional algorithms and to enhance the texture quality of the generated virtual view, Exemplar Based In-painting algorithm is used. The boundary noise which occurs in the initial virtual view obtained by 3D warping is also removed. After 3D warping, we estimate the relative location of the background to the holes and then pixels adjacent to the background are filled in priority to get better result by not using only adjacent object's information. Also, the temporal inconsistency between frames can be reduced by expanding the search region up to the previous frame when searching for most similar patch. The superiority of the proposed algorithm compared to the existing algorithms can be shown through the experimental results.
Robust Nonlinear Control of a Mobile Robot
Zidani, Ghania ; Drid, Said ; Chrifi-Alaoui, Larbi ; Arar, Djemai ; Bussy, Pascal ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 1012~1019
DOI : 10.5370/JEET.2016.11.4.1012
A robust control intended for a nonholonomic mobile robot is considered to guarantee good tracking a desired trajectory. The main drawbacks of the mobile robot model are the existence of nonholonomic constraints, uncertain system parameters and un-modeled dynamics. in order to overcome these drawbacks, we propose a robust control based on Lyapunov theory associated with sliding-mode control, this solution shows good robustness with respect to parameter variations, measurement errors, noise and guarantees position and velocity tracking. The global asymptotic stability of the overall system is proven theoretically. The simulation results largely confirm the effectiveness of the proposed control.
Low-Complexity Sub-Pixel Motion Estimation Utilizing Shifting Matrix in Transform Domain
Ryu, Chul ; Shin, Jae-Young ; Park, Eun-Chan ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 1020~1026
DOI : 10.5370/JEET.2016.11.4.1020
Motion estimation (ME) algorithms supporting quarter-pixel accuracy have been recently introduced to retain detailed motion information for high quality of video in the state-of-the-art video compression standard of H.264/AVC. Conventional sub-pixel ME algorithms in the spatial domain are faced with a common problem of computational complexity because of embedded interpolation schemes. This paper proposes a low-complexity sub-pixel motion estimation algorithm in the transform domain utilizing shifting matrix. Simulations are performed to compare the performances of spatial-domain ME algorithms and transform-domain ME algorithms in terms of peak signal-to-noise ratio (PSNR) and the number of bits per frame. Simulation results confirm that the transform-domain approach not only improves the video quality and the compression efficiency, but also remarkably alleviates the computational complexity, compared to the spatial-domain approach.
Anti-Sway Control of the Overhead Crane System using HOSM Observer
Kwon, Dongwoo ; Eom, Myunghwan ; Chwa, Dongkyoung ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 1027~1034
DOI : 10.5370/JEET.2016.11.4.1027
This paper proposes a sum of squares (SOS) method for anti-swing control of overhead crane system using HOSM (High-Order Sliding-Mode) observer. By representing the dynamic equations of overhead crane as the polynomial dynamic equations via Taylor series expansion, the control input is obtained from the converted polynomial dynamic equations by numerical tool SOSTOOL. Since the actual crane systems include disturbance such as wind and friction, we propose a method to compensate for the disturbance by estimating the disturbance using HOSM observer. Numerical simulations show the effectiveness and the applicability of the proposed method.
A Robust Crack Filter Based on Local Gray Level Variation and Multiscale Analysis for Automatic Crack Detection in X-ray Images
Peng, Shao-Hu ; Nam, Hyun-Do ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 1035~1041
DOI : 10.5370/JEET.2016.11.4.1035
Internal cracks in products are invisible and can lead to fatal crashes or damage. Since X-rays can penetrate materials and be attenuated according to the material’s thickness and density, they have rapidly become the accepted technology for non-destructive inspection of internal cracks. This paper presents a robust crack filter based on local gray level variation and multiscale analysis for automatic detection of cracks in X-ray images. The proposed filter takes advantage of the image gray level and its local variations to detect cracks in the X-ray image. To overcome the problems of image noise and the non-uniform intensity of the X-ray image, a new method of estimating the local gray level variation is proposed in this paper. In order to detect various sizes of crack, this paper proposes using different neighboring distances to construct an image pyramid for multiscale analysis. By use of local gray level variation and multiscale analysis, the proposed crack filter is able to detect cracks of various sizes in X-ray images while contending with the problems of noise and non-uniform intensity. Experimental results show that the proposed crack filter outperforms the Gaussian model based crack filter and the LBP model based method in terms of detection accuracy, false detection ratio and processing speed.
Control of the Lateral Displacement Restoring Force of IRWs for Sharp Curved Driving
Ahn, Hanwoong ; Lee, Hyungwoo ; Go, Sungchul ; Cho, Yonho ; Lee, Ju ;
Journal of Electrical Engineering and Technology, volume 11, issue 4, 2016, Pages 1042~1048
DOI : 10.5370/JEET.2016.11.4.1042
This paper presents a lateral displacement restoring force control for the independently rotating wheelsets (IRWs) of shallow-depth subway systems. In the case of the near surface transit, which has recently been introduced, sharp curved driving performance is required for the city center service. It is possible to decrease the curve radius and to improve the performance of the straight running with the individual torque control. Therefore, the individual torque control performance of the motor is the most important point of the near surface transit. This paper deals with a lateral displacement restoring force control for sharp curved driving. The validity and usefulness of the proposed control algorithm is verified by experimental results using a small-scale bogie system.