Computer Engineering Commons^™

An Extended Flux Model-Based Rotor Position Estimator For Sensorless Control Of Interior Permanent Magnet Synchronous Machines, Yue Zhao, Zhe Zhang, Wei Qiao, Long Wu

Department of Electrical and Computer Engineering: Faculty Publications

Starting from the classical dynamic model of interior permanent magnet synchronous machines (IPMSMs) expressed in the stationary reference frame, this paper presents a mathematical model reconstruction process for IPMSMs, from which an extended flux-based IPMSM model is derived. Compared with the commonly used extended electromotive force-based model, the extended flux-based model has notable advantages of simpler model structure and less sensitive to machine parameter and speed variations. An extended flux model-based position estimator is then proposed for sensorless control of an IPMSM by utilizing a sliding-mode observer with a dynamic position compensator. The latter improves the dynamic performance and low-speed …

Sensorless Control Of Surface-Mounted Permanent-Magnet Synchronous Machines For Low-Speed Operation Based On High-Frequency Square-Wave Voltage Injection, Yue Zhao, Zhe Zhang, Cong Ma, Wei Qiao, Liyan Qu

Department of Electrical and Computer Engineering: Faculty Publications

This paper proposes a high-frequency signal injection-based position estimation scheme for surface-mounted permanent-magnet synchronous machines (SPMSM) operating in the low-speed range. A square-wave voltage vector is injected in the estimated rotating reference frame. The rotor position information is then extracted from the envelopes of the resulting induced high-frequency currents in the stationary reference frame. The proposed position estimation method has almost no dependence on machine asymmetric properties and, therefore, is well suited for SPMSM applications. Simulation results are provided to verify the effectiveness of the proposed method from 1 Hz to 50 Hz electric fundamental frequency under all load conditions. …

Model Reference Adaptive System-Based Speed Estimators For Sensorless Control Of Interior Permanent Magnet Synchronous Machines, Yue Zhao, Wei Qiao, Long Wu

Department of Electrical and Computer Engineering: Faculty Publications

In this work, speed estimators are designed based on a model reference adaptive system (MRAS) for sensorless control of interior permanent magnet synchronous machines (IPMSMs). To provide better filtering performance and reduce the noise contents in the estimated speed, an adaptive line enhancer is proposed to work with a sliding-mode observer to provide an improved reference model for speed estimation. In addition, a heterodyning speed adaption scheme is proposed to replace the conventional speed adaption mechanism. The proposed MRASbased speed estimator has two different operating modes, which are suitable for generator- and motor-type applications, respectively. The effectiveness of the proposed …

Frequency Demodulation-Aided Condition Monitoring For Drivetrain Gearboxes, Dingguo Lu, Wei Qiao

Department of Electrical and Computer Engineering: Faculty Publications

Condition monitoring and fault diagnosis (CMFD) of drivetrain gearboxes has become a prominent challenge in assorted industries. Current-based diagnostic techniques have significant advantages over traditional vibration-based techniques in terms of accessibility, cost, implementation and reliability. This paper proposes a current-based, frequency demodulation-aided CMFD method for drivetrain gearboxes. A mathematical model is developed for a drivetrain consisting of a two-stage gearbox and a permanent magnet synchronous generator (PMSG), from which the characteristic frequencies of gearbox faults in the PMSG stator current are derived. An adaptive signal resampling method is proposed to convert the variable fault characteristic frequencies to constant values for …

Current-Based Fault Detection For Wind Turbine Systems Via Hilbert-Huang Transform, Dingguo Lu, Wei Qiao, Xiang Gong, Liyan Qu

Department of Electrical and Computer Engineering: Faculty Publications

Mechanical failures of wind turbines represent a significant cost in both repairs and downtime. Detecting incipient faults of wind turbine components permits maintenance to be scheduled and failed parts to be repaired or replaced before causing failures of other components or catastrophic failure of the system. This paper proposes a Hilbert-Huang transform (HHT)-based algorithm to effectively extract fault signatures in generator current signals for wind turbine fault diagnosis by using the HHT’s capability of accurately representing the instantaneous amplitude and frequency of nonlinear and nonstationary signals. A phase-lock-loop (PLL) method is integrated to estimate wind turbine rotating speed, which is …

Low-Power Analog Processing For Sensing Applications: Low-Frequency Harmonic Signal Classification, Daniel J. White, Peter E. Williams, Michael W. Hoffman, Sina Balkir

Department of Electrical and Computer Engineering: Faculty Publications

A low-power analog sensor front-end is described that reduces the energy required to extract environmental sensing spectral features without using Fast Fourier Transform (FFT) or wavelet transforms. An Analog Harmonic Transform (AHT) allows selection of only the features needed by the back-end, in contrast to the FFT, where all coefficients must be calculated simultaneously. We also show that the FFT coefficients can be easily calculated from the AHT results by a simple back-substitution. The scheme is tailored for low-power, parallel analog implementation in an integrated circuit (IC). Two different applications are tested with an ideal front-end model and compared to …

Fiber-Optic Refractometer Based On An Etched High-Q Π-Phase-Shifted Fiber-Bragg-Grating, Qi Zhang, Natale J. Ianno, Ming Han

Department of Electrical and Computer Engineering: Faculty Publications

We present a compact and highly-sensitive fiber-optic refractometer based on a high-Q π-phase-shifted fiber-Bragg-grating (πFBG) that is chemically etched to the core of the fiber. Due to the π phase-shift, a strong πFBG forms a high-Q optical resonator and the reflection spectrum features an extremely narrow notch that can be used for highly sensitivity refractive index measurement. The etched πFBG demonstrated here has a diameter of ~9.3 μm and a length of only 7 mm, leading to a refractive index responsivity of 2.9 nm/RIU (RIU: refractive index unit) at an ambient refractive index of 1.318. The reflection spectrum of the …

Optimal Receiver Antenna Location In Indoor Environment Using Dynamic Differential Evolution And Genetic Algorithm, Shu-Han Liao, Chien-Hung Chen, Chien-Ching Chiu, Min-Hui Ho, Tadeusz A. Wysocki, Beata J. Wysocki

Department of Electrical and Computer Engineering: Faculty Publications

Using the impulse responses of these multipath channels, the bit error rate (BER) performance for binary pulse amplitude modulation impulse radio ultra-wideband communication system is calculated. The optimization location of receiving antenna is investigated by dynamic differential evolution (DDE) and genetic algorithm (GA) to minimize the outage probability. Numerical results show that the performance for reducing BER and outage probability by DDE algorithm is better than that by GA.

Broadening The Cloaking Bandwidth With Non-Foster Metasurfaces, Pai-Yen Chen, Christos Argyropoulos, Andrea Alu

Department of Electrical and Computer Engineering: Faculty Publications

We introduce the concept and practical design of broadband, ultrathin cloaks based on non-Foster, negatively capacitive metasurfaces. By using properly tailored, active frequency-selective screens conformal to an object, within the realm of a practical realization, we show that it is possible to drastically reduce the scattering over a wide frequency range in the microwave regime, orders of magnitude broader than any available passive cloaking technology. The proposed active cloak may impact not only invisibility and camouflaging, but also practical antenna and sensing applications.

Terahertz Antenna Phase Shifters Using Integrally-Gated Graphene Transmission-Lines, Pai-Yen Chen, Christos Argyropoulos, Andrea Alu

Department of Electrical and Computer Engineering: Faculty Publications

We propose the concept and design of terahertz (THz) phase shifters for phased antenna arrays based on integrally- gated graphene parallel-plate waveguides (GPPWGs). We show that an active transmission-line may be realized by combining GPPWGs with double-gate electrodes, in which the applied gate voltage can control the guiding properties of the gated sections. This may enable the realization of THz electronic switches and tunable loaded-lines for sub mm-wave antenna systems. Based on these active components, we theoretically and numerically demonstrate several digital and analog phase shifter designs for THz frequencies, with a wide range of phase shifts and small return …

Negative Refraction, Gain And Nonlinear Effects In Hyperbolic Metamaterials, Christos Argyropoulos, Nasim Mohammadi Estakhri, Francesco Monticone, Andrea Alu

Department of Electrical and Computer Engineering: Faculty Publications

The negative refraction and evanescent-wave canalization effects supported by a layered metamaterial structure obtained by alternating dielectric and plasmonic layers is theoretically analyzed. By using a transmission-line analysis, we formulate a way to rapidly analyze the negative refraction operation for given available materials over a broad range of frequencies and design parameters, and we apply it to broaden the bandwidth of negative refraction. Our analytical model is also applied to explore the possibility of employing active layers for loss compensation. Nonlinear dielectrics can also be considered within this approach, and they are explored in order to add tunability to the …

Testing Robustness Of Relative Complexity Measure Method Constructing Robust Phylogenetic Trees For Galanthus L. Using The Relative Complexity Measure, Yasin Bakis, Hasan H. Otu, Nivart Tasci, Cem Meydan, Nese Bilgin, Sirri Yuzbasioglu, O Ugur Sezerman

Department of Electrical and Computer Engineering: Faculty Publications

Background: Most phylogeny analysis methods based on molecular sequences use multiple alignment where the quality of the alignment, which is dependent on the alignment parameters, determines the accuracy of the resulting trees. Different parameter combinations chosen for the multiple alignment may result in different phylogenies. A new non-alignment based approach, Relative Complexity Measure (RCM), has been introduced to tackle this problem and proven to work in fungi and mitochondrial DNA.

Result: In this work, we present an application of the RCM method to reconstruct robust phylogenetic trees using sequence data for genus Galanthus obtained from different regions in Turkey. Phylogenies …

Transparent, Flexible, And Solid-State Supercapacitors Based On Graphene Electrodes, Y. Gao, Y. S. Zhou, W. Xiong, L. J. Jiang, M. Mahjouri-Samani, P. Thirugnanam, X. Huang, M. M. Wang, L. Jiang, Y. F. Lu

Department of Electrical and Computer Engineering: Faculty Publications

In this study, graphene-based supercapacitors with optical transparency and mechanical flexibility have been achieved using a combination of poly(vinyl alcohol)/ phosphoric acid gel electrolyte and graphene electrodes.An optical transmittance of ∼67% in a wavelength range of 500-800 nm and a 92.4% remnant capacitance under a bending angle of 80◦ have been achieved for the supercapacitors. The decrease in capacitance under bending is ascribed to the buckling of the graphene electrode in compression. The supercapacitors with high optical transparency, electrochemical stability, and mechanical flexibility hold promises for transparent and flexible electronics.

Mass Sensor, Mathias M. Schubert, Eva Schubert, Tino Hofmann, Daniel Schmidt

Department of Electrical and Computer Engineering: Faculty Publications

A mass sensor is provided for determining the mass of small objects. The mass sensor has a plurality of nanostructures attached to a substrate. The nanostructures and the substrate are irradiated with an electromagnetic wave to determine a first mechanical-electromagnetic wave to determine a first mechanical-electromagnetic resonant frequency of the mass sensor. After a particle is attached to the nanostructures, the substrate and the nanostructures to which the particle is attached are irradiated with an electromagnetic wave to determine a second mechanical electromagnetic resonant frequency of the mass sensor. A mass of the particle is determined based on a difference …

Terahertz Resonator, Eva Schubert, Mathias M. Schubert, Tino Hofmann

Department of Electrical and Computer Engineering: Faculty Publications

A tunable terahertz resonator includes a semiconductor Substrate and a metal layer contacting a surface of the semiconductor substrate. A depletion layer is formed in the semiconductor substrate near an interface between the metal layer and the semiconductor Substrate. A chiral nanostructure is coupled to the substrate or the metal layer, the chiral nanostructure including a conducting or semiconducting material and having an inductance. A bias circuit applies a bias Voltage across the metal layer and the semiconductor Substrate to control a capacitance of a tunable capacitor that includes the depletion layer. The chiral nanostructure and the tunable capacitor form …

A P2p Computing System For Overlay Networks, Grzegorz Chmaj, Krzysztof Walkowiak

Electrical & Computer Engineering Faculty Research

A distributed computing system is able to perform data computation and distribution of results at the same time. The input task is divided into blocks, which are then sent to system participants that offer their resources in order to perform calculations. Next, a partial result is sent back by the participants to the task manager (usually one central node). In the case when system participants want to get the final result, the central node may become overloaded, especially if many nodes request the result at the same time. In this paper we propose a novel distributed computation system, which does …

Composite Power System Adequacy Assessment Based On Postoptimal Analysis, Amir Safdarian, Mahmood Fotuhi-Firuzabad, Farrokh Aminifar

Turkish Journal of Electrical Engineering and Computer Sciences

The modeling and evaluation of enormous numbers of contingencies are the most challenging impediments associated with composite power system adequacy assessment, particularly for large-scale power systems. Optimal power flow (OPF) solution, as a widely common approach, is normally employed to model and analyze each individual contingency as an independent problem. However, mathematical representations associated with diverse states are slightly different in one or a few generating units, line outages, or trivial load variations. This inherent attribute brings a promising idea to speed up the contingency evaluation procedure. In this paper, postoptimal analysis (POA), as a well-recognized technique to attack a …

A Novel Multirobot Map Fusion Strategy For Occupancy Grid Maps, Sebahatti̇n Topal, İsmet Erkmen, Aydan Müşerref Erkmen

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, we consider the problem of merging partial occupancy grid environment maps, which are extracted independently by individual robot units during search and rescue (SAR) operations in icomplex disaster environments. Moreover, these maps are combined using intensity-based and area-based features without knowing the initial position and orientation of the robots. Our proposed approach handles the limitation of existing studies in the literature; for example, the limited overlapped area between partial maps of robots is enough for good merging performance and unstructured and complex partial environment maps can be merged efficiently. These abilities allow multirobot teams to efficiently generate …

A Bacterial Foraging Optimization Approach For Tuning Type-2 Fuzzy Logic Controller, Mohammad Kiani, Seyed Mohammad Ali Mohammadi, Ali Akbar Gharaveisi

Turkish Journal of Electrical Engineering and Computer Sciences

The type-1 fuzzy sets theory was proposed to handle uncertainty in control systems, but some cases showed some liabilities of type-1 fuzzy sets when faced with unpredictable disturbance and uncertainties. Therefore, type-2 fuzzy sets were introduced and extended while providing more degrees of freedom in designing criteria. The most important specification of type-2 fuzzy sets is the interval between a superior membership function and an inferior membership function, which is called the footprint of uncertainty. This paper presents a bacterial foraging optimization approach for optimizing the parameterized membership function. The above criterion is applied to an automatic voltage regulator system …

A Temporal Xml Data Model In Anaesthesia Information Systems, Oya Ünlü Duygulu, Taflan İmre Gündem

Turkish Journal of Electrical Engineering and Computer Sciences

Time information is an important aspect of a health information system. Health information cannot be represented and queried correctly without time in medical research, auditing, and medicolegal cases. Extensible Markup Language (XML) is being used in health information systems and has been formerly proposed as a data model for anaesthesia information systems. In this paper, we propose incorporating time into an XML model for anaesthesia information systems. A new storage structure and a temporal index structure are proposed in order to store temporal XML data and process time queries efficiently. In our proposed model, time has 4 dimensions: valid time, …

Design And Evaluation Of Schemes For Computing Sum Of Squares In Fixed Point, Meti̇n Mete Özbi̇len, Milos D. Ercegovac

Turkish Journal of Electrical Engineering and Computer Sciences

Several schemes for computing the sum of squares for fixed point numbers are designed, synthesized, and evaluated in this study. The schemes use radix-2 folding, radix-4 folding, and radix-4 dual recoding approaches for squaring. The schemes have been modeled in hardware description language, simulated, and synthesized using Cadence SOC81 in 45 nm and 90 nm libraries and with Mentor Graphics Leonardo Spectrum for 180 nm. We show delay and area for 16-, 24-, and 32-bit operands. After hard-wire and software optimizations, it is seen that schemes with radix-4 give better results, especially in area.

End-To-End Transmission Time-Based Opportunistic Routing Protocols For Bus Networks, Luobei Kuang, Zhijun Wang, Ming Xu, Yingwen Cheng

Turkish Journal of Electrical Engineering and Computer Sciences

Single path routing protocols for Internet access in bus networks (composed of traveling city public buses) may not achieve satisfactory performance because of frequent bus mobility. This paper studies the opportunistic routing protocols in bus networks to improve the system throughput and reduce the access delay. In this paper, we first propose an end-to-end transmission time (EET)-based opportunistic routing (OR) framework. We then derive 3 EET-based OR protocols, EETOR (EET-based OR), EETMcOR (EET-based OR with MAC contention consideration), and EETCcOR (EET-based OR with congestion control consideration), which consider 3 different EET metrics. EETOR considers the network layer transmission behavior to …

Performance Analysis Of Bid Calculation Methods In Multirobot Market-Based Task Allocation, Burak Kaleci̇, Osman Parlaktuna

Turkish Journal of Electrical Engineering and Computer Sciences

In this study, the empirical results of a market-based task allocation method for heterogeneous and homogeneous robot teams and different types of tasks in 2 different environments are presented. The proposed method allocates robots to tasks through a parallel multiitem auction-based process. The main contribution of the proposed method is energy-based bid calculations, which take into account both the heterogeneity of the robot team and features of the tasks. The multirobot task allocation problem is considered as the optimal assignment problem and the Hungarian algorithm is used to clear the auctions. Simulations are carried out using energy-based, distance-based, and time-based …

A Word Spotting Method For Farsi Machine-Printed Document Images, Yaghoub Pourasad, Houshang Hassibi, Azam Ghorbani

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, a word spotting approach for Farsi printed document images has been presented. The main idea of the paper is the font recognition of Farsi document images and query word modification according to the document image's font before searching. This operation increases the similarity between the query word image and its instances in the document image; therefore, the performance of the word spotting system increases. In the proposed word spotting approach, after the query word modification, the query word image rectangle is searched in the text lines of the document image using XNOR similarity measurement. In order to …

Investigation Of The Telluric Effects Arising Along The Cathodically Protected Natural Gas Pipeline Between Karadeniz Ereğli And Düzce, Bi̇lal Demi̇rel, Hayri̇ Yalçin

Turkish Journal of Electrical Engineering and Computer Sciences

Cathodic protection is one of the most widely used applications for protecting underground and submarine metallic structures from corrosion. This method is based on providing the electrons, which metallic structures lose as a result of electrolytic reaction, by the cathodic protection system. However, from time to time, it may be possible that there is some unwanted interference input into the metallic structure in such applications. This study is aimed at ascertaining the existence, arising frequency, and magnitude of an interference called the telluric effect that is going in and out of the natural gas pipeline between Düzce and Karadeniz Ereğli …

A New Multiobjective Fuzzy Shuffled Frog-Leaping Algorithm For Optimal Reconfiguration Of Radial Distribution Systems In The Presence Of Reactive Power Compensators, Hossein Dehghan Dehnavi, Saeid Esmaeili

Turkish Journal of Electrical Engineering and Computer Sciences

This paper presents a new approach for the optimal reconfiguration of radial distribution systems in the presence of reactive power compensators (RPCs). The proposed method is based on the simultaneous reconfiguration and RPC allocation for the mitigation of losses, equalizing the feeder load balancing as well as improving the voltage profile in power distribution networks. In this paper, the compensators are the capacitor bank and distribution static compensator, which is a type of distribution flexible alternating current transmission system device representative of conventional and modern RPCs. In this regard, the optimal states of the distribution system tie switches are determined …

Cancer Risk Analysis By Fuzzy Logic Approach And Performance Status Of The Model, Atinç Yilmaz, Kürşat Ayan

Turkish Journal of Electrical Engineering and Computer Sciences

Cancer is the leading life-threatening disease for people in today's world. Although cancer formation is different for each type of cancer, it has been determined by studies and research that stress also triggers cancer types. Early precaution is very important for people who have not fallen ill yet with a disease like cancer that has a high mortality rate and expensive treatment. With this study, we expound that the possibility of developing such disease may be decreased and people could take measures against it. For the 3 cancer types selected as pilot work by introducing a fuzzy logic model, the …

A Framework For Medical Image Retrieval Using Merging-Based Classification With Dependency Probability-Based Relevance Feedback, Hossein Pourghassem, Sabalan Daneshvar

Turkish Journal of Electrical Engineering and Computer Sciences

Content-based image retrieval (CBIR) systems are used to retrieve relevant images from large-scale databases. In this paper, a framework for the image retrieval of a large-scale database of medical X-ray images is presented. This framework is designed based on query image classification into several prespecified homogeneous classes. Using a merging scheme and an iterative classification, the homogeneous classes are formed from overlapping classes in the database. For this purpose, the shape and texture features, selected using the forward selection algorithm, are optimized by a novel genetic algorithm-based feature reduction and optimization algorithm in the feature space. In this algorithm, using …

Biogeography-Based Optimization For Voltage Stability Improvement And Reactive Reserve Management, Subramanian Annamalai, Ravi Govinthabamy

Turkish Journal of Electrical Engineering and Computer Sciences

This paper proposes a biogeography-based optimization algorithm to enhance the voltage stability of a power system. It computes the optimal quantity of reactive power support with a view to place the static VAR compensator at the most appropriate nodes. The scheme inflicts an effective management of VAR resources in the process of improving the voltage profile and reducing the network losses. It includes the results of IEEE 30-node system to illustrate the feasibility of the approach.

Novel Control Strategy For Voltage Source Converters Based On Energy Function, Sanaz Namayan Tavana, Gevork Gharehpetian, Mehrdad Abedi, Ali Bidadfar

Turkish Journal of Electrical Engineering and Computer Sciences

This paper proposes a nonlinear control strategy for pulse-width modulated voltage source converters (VSCs). A passivity-based approach, resulting from the Lyapunov direct method, is presented for designing an effective nonlinear VSC controller to improve their dynamic behaviors under perturbed conditions. The differential equations of the converters are obtained and then transformed into a d-q frame. Considering the nonlinearity of the transformed equations, the Lyapunov direct method is utilized to find a solution to improve the transient response. The time derivative of the Lyapunov function guarantees that increasing its dissipative term will result in the trajectory of the VSC system returning …