bluuebunny/crossref_metadata_2025_split huggingface dataset:
Post processing for the vector finite element method: from edge to nodal values
Authors: Vollaire Christian , Musy François , Perrussel Ronan 
Published: January 2007

PurposePropose post processing methods for the edge finite element (FE) method on a tetrahedral mesh. They make it possible to deduce vector values on the vertices from scalar values defined on the edges of the tetrahedra.Design/methodology/approachThe new proposed techniques are based on a least squares formulation leading to a sparse matrix system to be solved. They are compared in terms of accuracy and CPU time on a FEs formulation for open boundary – frequency domain problems.FindingsA significant improvement of vector values accuracy on the vertices of the tetrahedra is obtained compared to a classical approach with a very small additional computation time.Originality/valueThis work presents techniques: to obtain the values at the initial nodes of the mesh and not inside the tetrahedra; and to take into account the discontinuity to the interface between two media of different electromagnetic properties.
Algorithms for automatic torus motor parameters identification: comparative study
Authors: Al‐Badi Abdullah , Gastli Adel , Jervase Joseph A. 
Published: January 2007

PurposeThe parameters of axial‐field machines are very small compared with the parameters of conventional machines. Different measuring methods are normally used in order to obtain good estimates of the machine parameters. These methods are difficult to perform, costly and time consuming. This paper proposes the use of genetic algorithms to predict the self and mutual inductances of a specific type of axial‐field machine, the Torus motor.Design/methodology/approachThe parameter extraction is reformulated as a search and optimization problem in which the only requirement is a set of values of current versus time and an approximate estimate of the parameters.FindingsThe predicted machine self and mutual inductances are verified by comparing with several measuring methods and excellent agreement is obtained.Originality/valueDemonstrates that genetic algorithms can predict the self and mutual inductances of the Torus machine automatically with high accuracy.
A combined multicell‐WENO solver for the Boltzmann‐Poisson system of 1D semiconductor devices
Authors: Domaingo A. , Galler M. , Schürrer F. 
Published: January 2007

PurposeTo present a new direct solution method for the Boltzmann‐Poisson system for simulating one‐dimensional semiconductor devices.Design/methodology/approachA combination of finite difference and finite element methods is applied to deal with the differential operators in the Boltzmann transport equation. By taking advantage of a piecewise polynomial approximation of the electron distribution function, the collision operator can be treated without further simplifications. The finite difference method is formulated as a third order WENO approach for non‐uniform grids.FindingsComparisons with other methods for a well‐investigated test case reveal that the new method allows faster simulations of devices without losing physical information. It is shown that the presented model provides a better convergence behaviour with respect to the applied grid size than the Minmod scheme of the same order.Research limitations/implicationsThe presented direct solution methods provide an easily extensible base for other simulations in 1D or 2D. By modifying the boundary conditions, the simulation of metal‐semiconductor junctions becomes possible. By applying a dimension by dimension approximation models for two‐dimensional devices can be obtained.Practical implicationsThe new model is an efficient tool to acquire transport coefficients or current‐voltage characteristics of 1D semiconductor devices due to short computation times.Originality/valueNew grounds have been broken by directly solving the Boltzmann equation based on a combination of finite difference and finite elements methods. This approach allows us to equip the model with the advantages of both methods. The finite element method assures macroscopic balance equations, while the WENO approximation is well‐suited to deal with steep gradients due to the doping profiles. Consequently, the presented model is a good choice for the fast and accurate simulation of one‐dimensional semiconductor devices.
A new methodology for distribution systems faults identification, location and characterization
Authors: Campoccia A. , Di Silvestre M.L. , Incontrera I. , Riva Sanseverino E. 
Published: January 2007

PurposeIdentify a new methodology for fault characterization, identification and location in electrical distribution systems, based on the use of matrix algebra.Design/methodology/approachThe developed diagnostic methodology is based on a high precision analytical model of the network using a distributed parameters representation.FindingsTest results have proved the approach to be efficient and precise, while providing a generalized quadripolar model of a line affected by the most common kinds of fault.Research limitations/implicationsGeneralization to a greater number of fault cases, experimental tests.Practical implicationsUtilities are quite interested in such items, since the new required quality standards put severe constraints on faults management and clearance. On the other hand, the system requires a rather complete measurement equipment of secondary substations.Originality/valueThe paper presents a new diagnostic technique for faults identification, location and characterization in distribution systems.
Application of different saturation curves in a mathematical model of hysteresis
Authors: Włodarski Zdzisław , Włodarska Jadwiga , Brykalski Andrzej 
Published: January 2007

PurposeThe increase of the accuracy of a mathematical model of hysteresis by the choice of the optimum saturation curve for a given material.Design/methodology/approachHysteresis loops of typical soft magnetic materials are approximated with the help of the Taka´cs magnetization model using different saturation curves. The quality of approximations is determined by the deviation of computed magnetic induction amplitudes, iron losses, apparent remanences and coercivities from the measured values.FindingsBy the proper choice of saturation curve, the relative inaccuracy of approximations can be reduced with reference to the original model based on tangent hyperbolic function.Research limitations/implicationsThe accuracy of approximations worsens close to saturation because of the excessive rise of magnetization due to the linear term of the model. This effect should be minimized by the application of complex saturation curves using greater number of parameters.Practical implicationsOwing to the convenient analytical form and increased accuracy, the model equations can be used in simpler practical evaluations of hysteresis effects and for teaching purposes.Originality/valuePresented form of model equations enables approximation of hysteresis loops and the evaluation of main characteristics of magnetic materials on the basis of any saturation curve.
Wave reflection on unconventional mirrors
Authors: Hillion P. 
Published: January 2007

PurposeTo extend to electromagnetism the acoustic wave reflections on time reversal mirrors used in medical imaging, nondestructive testing and underwater acoustics.Design/methodology/approachRecent works (1993‐2004) analyse the reflection of acoustic waves on time reversal mirror. To perform the same job in electromagnetism, the behaviour of the electromagnetic field tensor under the space and time inversions of the referential is investigated and also, when in addition an exchange of two coordinates exists. All these reflections are supposed obtained from perfect but unconventional mirrors.FindingsElectromagnetic reflections on unconventional mirrors have remarquable features since some of them give birth to a real twin source of the incident source with an opposite polarization.Practical implicationsThe techniques used in acoustic to manufacture time reversal mirrors can be used in electromagnetism with possible applications of such mirrors for instance in cameras to avoid reversed photographs but no information on practical realizations has appeared in the open literature.Orginality/valueExtends research on electromagnetism.
Tracing AM‐detector transfer characteristics
Authors: Tadeusiewicz M. , Hałgas S. 
Published: January 2007

PurposeShowing both theoretically and experimentally that the Newton‐Raphson algorithm is a very efficient tool for computing the transfer factor characteristic of AM detectors.Design/methodology/approachAn equation which describes the diode and transistor AM detectors has been investigated. Using elementary techniques of mathematical analysis, some theoretical properties of the equation have been formulated and convergence of the Newton‐Raphson algorithm has been proved.FindingsIt is shown that the Newton‐Raphson algorithm is an efficient tool for tracing the transfer factor characteristics of both diode and transistor AM detector. The convergence of this algorithm is proved and a comparison with SPICE simulation is made. Furthermore, the diode and transistor AM detectors have been built up and validating measurements have been carried out. The comparison shows that the algorithm proposed in the paper computes the characteristics fast achieving good accuracy.Research limitations/implicationsThe results obtained are limited to those described in the paper diode and transistor AM detectors.Originality/valueSome properties of the nonlinear equation describing the AM detectors are formulated and convergence of the Newton‐Raphson algorithm to a unique solution is proved.
A discrete‐time model including cross‐saturation for surface permanent‐magnet synchronous machines
Authors: De Belie Frederik M.L.L. , Melkebeek Jan A.A. , Vandevelde Lieven , Geldhof Kristof R. , Boel René K. 
Published: January 2007

PurposeTo provide a discrete‐time nonlinear model for surface permanent‐magnet synchronous machines (SPMSMs) in order to discuss the stability of such machines.Design/methodology/approachThrough differencing the co‐energy, obtained from a finite element method, the main flux path can be described by a complex reluctance. Furthermore, for a SPMSM, an equivalent circuit is presented that includes the eddy‐current losses and the voltage drops across stator resistance and leakage inductance. The model is transformed to a discrete‐time state‐space model by using a forward rectangular rule. By using a root locus technique, the stability of the new model is discussed.FindingsFrom the calculated root locus it is concluded that the stability of a SPMSM is only guaranteed for certain values of the open loop gain. Moreover, by using the forward rectangular rule, it is concluded that a well‐considered time step has to be chosen.Research limitations/implicationsThe model considers the fundamental space harmonic components only. Moreover, the saturation of the leakage flux path is neglected.Practical implicationsAs the model is formulated in discrete time, it can be used in modern drives where a digital controller is used.Originality/valueThis paper presents an equivalent electrical circuit for SPMSMs that takes into account the saturation of the magnetizing flux paths as well as the magnetic interaction between the two orthogonal magnetic axes.
Frequency and time domain homogenization of laminated magnetic cores and windings in FE models of high‐frequency electromagnetic devices
Authors: Gyselinck J. , López‐Fernández X.M. 
Published: January 2007

PurposeTo review and discuss recently proposed homogenization methods for laminated magnetic cores and multi‐turn windings in FE models of electromagnetic devices.Design/methodology/approachThe frequency‐domain homogenization is based on the adoption of complex and frequency‐dependent material characteristics (e.g. reluctivity) in the homogenized domain. The value of the complex quantity is obtained analytically or by means of a simple 2D FE model. The time‐domain counterpart requires the introduction of additional unknowns and equation.FindingsThe homogenization methods allow to take into account the global eddy current effect in the individual laminations and wires, with a reasonable precision and computational cost.Research limitations/implicationsThe homogenization methods have been validated numerically, i.e. by comparison with brute‐force FE computations where the eddy current effects are directly and accurately taken into account. Experimental validation should follow.Originality/valueThe analogy between the homogenization of laminated cores and windings has been evidenced.
Comparison of artificial immune systems and genetic algorithms in electrical engineering optimization
Authors: Freschi Fabio , Repetto Maurizio 
Published: January 2007

PurposeThe purpose of this study is to investigate and compare the ability of a new optimization technique based on the emulation of the immune system to detect the global maximum with multimodal functions and to test the capability of exploring the parameter space with respect to clustering enhanced Genetic Algorithms (GA).Design/methodology/approachBoth algorithms have been tested on analytical test functions and on numerical functions of applicative interest. A set of performance criteria has been defined in order to numerically compare the performances of both optimization strategies.FindingsResults show the great ability of Artificial Immune Systems (AIS) in thoroughly exploring the space of variables. On the other side, GA are faster to converge to the global optimum, but selection pressure can reduce the number of detected local optima.Originality/valueThis work is an attempt to assess the performances of a relatively new optimization algorithm based on AIS and to find its behavior on multimodal test functions, using GAs as reference optimization technique.
Hybrid GA neuro‐fuzzy damping control system for UPFC
Authors: Khan Laiq , Lo K.L. , Jovanovic S. 
Published: January 2007

PurposeThe aim of the paper is to develop a novel genetic algorithm (GA)‐based supplementary NeuroFuzzy damping control system for the unified power flow controller (UPFC).Design/methodology/approachThe designed scheme employs a micro‐GA (μ‐GA) to avoid being trapped in a local minimum as opposed to the use of the classical back‐propagation technique. The scheme also uses the “Grand‐Parenting” technique for seeding the initial population to hasten the GA convergence speed. To further speed up the GA for solving the optimization problem, a parallelμ‐GA scheme is also used.FindingsIt has been discovered that a parallelμ‐GA scheme with three computers setup is approximately three times faster than theμ‐GA with a single computer node. Also whenμ‐GA is integrated with the “Grand‐Parenting” technique for seeding the initial population, it would hasten the convergence speed. The control scheme exhibits strong robustness and excellent damping performance when tested on a multi‐machine power system.Originality/valuePresentation of a novel NeuroFuzzy‐based UPFC that exhibits strong robustness and excellent damping performance.
A new computational approach for optimal reconfiguration of radial distribution systems using a fuzzy controlled genetic algorithm
Authors: Prasad K. , Sahoo N.C. , Ranjan R. , Chaturvedi A. 
Published: January 2007

PurposeThis research paper reports a novel genetic algorithm (GA)‐based approach for reconfiguration of radial distribution networks for real loss minimization and power quality improvement.Design/methodology/approachA fuzzy controlled GA has been used for efficient reconfiguration of radial distribution systems for loss minimization and power quality improvement. The special features of the proposed algorithm are: an improved chromosome coding/decoding for network representation so as to preserve the radial property without islanding any load after reconfiguration and an efficient convergence characteristics attributed to fuzzy controlled mutation.FindingsThe proposed network reconfiguration algorithm is very much effective in arriving at the global optimal solution (minimum loss network structure) because of efficient search of the solution space. Also, no invalid chromosomes are generated in the genetic evolution because of appropriate coding/decoding. The algorithm is found to be very much suitable for real time implementations.Research limitations/implicationsThis research paper provides the power distribution engineers with a computationally efficient approach for optimal operation of distribution systems.Practical implicationsThe algorithm proposed in this paper is computationally much faster compared to most of the present day mathematical programming approaches for distribution system operation. This makes it very much attractive for online implementations in any radial distribution network.Originality/valueThis paper has proposed a novel chromosome coding/decoding technique for radial distribution system and a fuzzy logic‐based mutation probability controller for efficient search of global solution space to be used in GA‐based optimal operation of radial distribution systems.
Novel efficient methods for inductance calculation of meander inductor
Authors: Stojanović Goran , Živanov Ljiljana , Damnjanović Mirjana 
Published: January 2007

PurposePresent 3D electromagnetic simulators have high accuracy but they are time and memory expensive. Owing to a fast and simple expression for inductance is also necessary for initial inductor design. In this paper, new efficient methods for total inductance calculation of meander inductor, are given. By using an algorithm, it is possible to predict correctly all inductance variations introduced by varying geometry parameters such as number of turns, width of conductor or spacing between conductors.Design/methodology/approachThe starting point for the derivation of the recurrent formula is Greenhouse theory. Greenhouse decomposed inductor into its constituent segments. Meander inductor is divided into straight conductive segments. Then the total inductance of the meander inductor is a sum of self‐inductances of all segments and the negative and positive mutual inductances between all combinations of straight segments. The monomial equation for the total inductance of meander inductor has been obtained by fitting procedure. The fitting technique, using the method of least squares, finds the parameters of the monomial equation that minimize the sum of squares of the error between the accurate data and fitted equation. The paper presents new expression for inductance of meander inductor, in the monomial form, which is suitable for optimization via geometric programming. The computed inductances are compared with measured data from the literature.FindingsThe first, recurrent, expression has the advantage that it indicates to the designer how the relative contributions of self, positive, and negative mutual inductance are related to the geometrical parameters. The second expression presents the inductance of the meander inductor in the monomial form, so that the optimization of the inductor can be done by procedure of the geometric programming. Simplicity and relatively good accuracy are the advantages of this expression, but on the other hand the physical sense of the expression is being lost. Thus, the effects of various geometry parameters on inductance are analyzed using two expressions and the software tool INDCAL.Practical implicationsApplied flexible efficient methods for inductance calculation of meander inductor are able to significantly increase the speed of RF and sensor integrated circuit design.Originality/valueFor the first time a simple expression for fast inductance calculation for meander inductor in monomial form is presented. It is explained how such an expression is generated, which can be directly implemented in circuit simulators.
The multi‐mode chaotic behaviors: N+N and 2D N‐scroll chaotic attractors
Authors: Türk Mustafa , Ata Fikret 
Published: January 2007

PurposeThe purpose of this paper is to present a simulation and realization of the different types of chaotic attractors using the generalized Chua's circuit equations.Design/methodology/approachThis paper presents n+n‐scroll and 2D n‐scroll chaotic attractors by introducing multiple breakpoints to the nonlinearity. Two piece‐wise linear elements controlled with x‐ and y‐state space variables are used. Chaotic scrolls are originated through both x‐ and y‐axes. The current feedback operational amplifiers are preferred in the experimental circuits because of their wide bandwidth.FindingsIt is possible to increase the number of the scrolls in two directions by varying the number of breakpoints in the piece‐wise linear characteristics or changing the location of equilibrium points of the system on 2D‐plane. Theoretically developed behaviors are also experimentally tested.Originality/valueThe excellent adaptation is observed between theoretical and experimental results. This paper also provides useful information about how to build the multiple breakpoints nonlinear elements using the simulation results.
Sliding‐mode control for speed sensorless induction machine drive using an adaptive nonlinear rotor flux observer
Authors: Arab Markadeh G.R. , Soltani J. 
Published: January 2007

PurposeTo propose and adaptive nonlinear controller for adjustable speed sensorless induction motor drive, using a novel adaptive rotor flux observer. The adaptive flux observer scheme in this paper provides the simultaneous estimation of the rotor speed, rotor resistance and stator resistance.Design/methodology/approachThe IM rotor speed and rotor flux controllers are designed based on combination of input‐output feedback linearizing, linear optimal feedback control and sliding‐mode (SM) control methods. In addition a novel adaptive rotor flux observer is designed based on Lyapunov theory. The proposed control method is tested by simulation and experimental results.FindingsThe composite rotor speed and rotor flux observer in combination with adaptive rotor flux scheme guarantees a perfect speed, torque and flux tracking control for the IM sensorless drive.Research limitations/implicationsThe proposed control method has a drawback in the IM low speed operating region. Additional research may be able to solve this problem as well as should analyze the sensitivity of the IM drive system performance with respect to variation of the system controller and adaptive flux observer gains. In addition, this research should also analyze the influence of sampling rate, truncation errors, measurement noise, simplifying model assumption and magnetic saturation.Practical implicationsThe proposed control method can be used for adaptive and robust control of the IM drive where an optimal efficiency is desired subject to the variable load torque demand.Originality/valueBased on Lyapunov theory, a novel adaptive rotor flux observer is introduced in which the rotor speed, rotor resistance and stator resistance are treated as the unknown constant parameters.