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1 – 10 of 281M. Chiampi, M. Repetto, V. Chechurin, A. Kalimov and L. Leboucher
A simulation of the motion of molten aluminium inside an electrolytic cell is presented. Since the driving term of the aluminium motion is the Lorentz (j × B) body force acting…
Abstract
A simulation of the motion of molten aluminium inside an electrolytic cell is presented. Since the driving term of the aluminium motion is the Lorentz (j × B) body force acting within the fluid,this problem involves the solution of the magneto‐hydro‐dynamic equations. Different solver modules for the magnetic field computation and for the fluid motion simulation are coupled together. The interactions of all these are presented and discussed.
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G. Gruosso and M. Repetto
The scope of the work is to provide an identification procedure for an hysteresis model based on nonlinear circuit cells.
Abstract
Purpose
The scope of the work is to provide an identification procedure for an hysteresis model based on nonlinear circuit cells.
Design/methodology/approach
An identification procedure for an hysteresis model based on nonlinear circuit cells is presented. The response of elementary cell is equal to a generalized play operator. The procedure allows the identification of the limit symmetric hysteresis loop and of minor loops. The identification procedure is based on the relationship between the circuit parameters and the discretization of the first derivative of the BH curve by means of a staircase function.
Findings
The model obtained is employed for the simulation of soft magnetic composite material cores under different supply voltage waveforms. The proposed identification procedure is able to define an accurate model of an hysteretic material with a low number of elemental network cells. The identification algorithm is simple and makes use of the limit hysteresis cycle only. Symmetric minor loops are used to tune “soft” operators for the correct reconstruction of cycles which do not reach saturation.
Research limitations/implications
The model is limited to scalar and static hysteresis model.
Practical implications
The model obtained can be used in network simulator like SPICE in order to model circuits in which magnetic devices are involved.
Originality/value
The circuit hysteresis model has been presented in literature, while its identification is newly proposed by the authors.
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A. Canova, G. Gruosso and M. Repetto
The scope of the work is to provide an hybrid numerical technique for the solution of electric field.
Abstract
Purpose
The scope of the work is to provide an hybrid numerical technique for the solution of electric field.
Design/methodology/approach
In this paper an integral approach for the solution of static electric field based on a dual discretization (DD) and on a surface method of moment (MoM) is presented. The proposed technique is applied to the solution of 3D electric field problems where different perfectly conducting bodies are placed in a homogeneous and isotropic medium. The approach is also extended to the analysis of static current field. In the presented formulation MoM is applied on a surface domain which is discretized according to a baricentrical dual scheme.
Findings
The procedure has been applied to several practical cases and it represents an efficient tool for the evaluation of lumped circuit parameters as capacitances of 3D conducting bodies and ground resistance of grounding systems.
Research limitations/implications
The formulation presented in the paper is limited to the calculus of electric field in homogeneous media. For future development the authors are working in order to include non‐homogeneous media.
Practical implications
The proposed approach aids the designer of electrical systems as large scale grounding systems or integrated circuit connections in the calculations of lumped electrical parameters.
Originality/value
The originality of the paper lies in the coupling of MoM with finite formulation and DD.
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A. Canova, F. Freschi, M. Repetto and M. Tartaglia
The definition of a simple model of low frequency magnetic field created by power industrial installations can be approached by using an equivalent source system (ESS). Given a…
Abstract
Purpose
The definition of a simple model of low frequency magnetic field created by power industrial installations can be approached by using an equivalent source system (ESS). Given a set of measured magnetic field points, the ESS, made by a limited set of current carrying wires or turns, must be placed and supplied in order to fit the measured magnetic field values. An optimisation procedure can be used to define the current values and the location of the ESS which minimize the error between the measured and computed magnetic field values.
Design/methodology/approach
A two‐step optimal procedure is defined: in the outer step a stochastic optimisation routine is used to drive the geometric control parameters of the ESS while, in the inner step, the current values flowing through the sources are computed to find the minimization of the error with respect to a set of measured magnetic field values. The optimisation procedure is based on an artificial immune system algorithm which focuses on a deep exploration of the search space and gave interesting results both in terms of accuracy and computational efficiency.
Findings
The results show that the proposed approach is able to reconstruct the magnetic field created by complex source system and give some accuracy measure on the reconstruction error. The optimisation process carried out also on conductor positions has allowed to find out the location of the real sources in an accurate way, also in presence of measurement errors.
Originality/value
The approach proposed uses optimisation procedures to solve the inverse problem of source reconstruction starting by a set of measured magnetic field values. The definition of a simple equivalent source structure, together with an optimisation procedure to set its control parameters, allows to simulate complex magnetic field sources, like power substations or cable systems, in a very efficient and compact way.
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D. Lahaye, A. Canova, G. Gruosso and M. Repetto
This work aims to present a multilevel optimization strategy based on manifold‐mapping combined with multiquadric interpolation for the coarse model construction.
Abstract
Purpose
This work aims to present a multilevel optimization strategy based on manifold‐mapping combined with multiquadric interpolation for the coarse model construction.
Design/methodology/approach
In the proposed approach the coarse model is obtained by interpolating the fine model using multiquadrics in a small number of points. As the algorithm iterates the response surface model is improved by enriching the set of interpolation points.
Findings
This approach allows to accurately solve the TEAM Workshop Problem 25 using as little as 33 finite element simulations. Furthermore, it allows a robust sizing optimization of a cylindrical voice‐coil actuator with seven design variables.
Research limitations/implications
Further analysis is required to gain a better understanding of the role that the initial coarse model accuracy plays in the convergence of the algorithm. The proposed model allows to carry out such analysis by varying the number of points included in the initial response surface model. The effect of the trust‐region stabilization in the presence of manifolds of equivalent solutions is also a topic of further investigations.
Originality/value
Unlike the closely related space‐mapping algorithm, the manifold‐mapping algorithm is guaranteed to converge to a fine model optimal solution. By combining it with multiquadric response surface models, its applicability is extended to problems for which other kinds of coarse model such as lumped parameter approximations for instance are tedious or impossible to construct.
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N. Bianchi, A. Canova, G. Gruosso, M. Repetto and F. Tonel
The optimisation of a tubular linear motor with interior permanent magnets is described. For a rapid design the whole process is divided in three parts: an analytical approach for…
Abstract
The optimisation of a tubular linear motor with interior permanent magnets is described. For a rapid design the whole process is divided in three parts: an analytical approach for the a preliminary investigation, a parametric analysis by means of a finite element method and an optimisation. The obtained results show that the adopted optimisation process is efficient for rapid and effective optimisation of the tubular linear motor.
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A. Canova, F. Freschi and M. Repetto
The paper presents an hybrid optimization technique which couples the artificial immune system (AIS) algorithm with a zeroth order deterministic method.
Abstract
Purpose
The paper presents an hybrid optimization technique which couples the artificial immune system (AIS) algorithm with a zeroth order deterministic method.
Design/methodology/approach
AIS has been developed to tackle multi‐modal optimization problems and it has shown a great ability to explore the objective function space. The algorithm is subdivided into two phases: an outer and an inner cycle. The outer cycle is devoted to the exploration of the space while the inner is a local exploration of the objective function. The new hybrid method proposes to replace the local search by a zeroth order deterministic search to speed up the overall convergence.
Findings
Results on two multi‐modal analytical objective functions show an increase of speed of the new procedure with respect to the standard AIS. The method is also tested on the TEAM 22 numerical problem and some a posteriori techniques for the analysis of multimodal blind objective functions are discussed.
Originality/value
The new Multimodal optimization algorithm has allowed to explore thoroughly feasibility space giving rise to a partition of the whole space, the use of hybrid technique increases the performances of standard AIS increasing the convergence to the optimal points.
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L. Vattuoneb, M. Repettoa and M. Roccab
Electron energy loss spectrometers (EELS) for surface studies require a high energy resolution (▵E ? 3 meV) monochromatic electron beam with the highest possible current. In order…
Abstract
Electron energy loss spectrometers (EELS) for surface studies require a high energy resolution (▵E ? 3 meV) monochromatic electron beam with the highest possible current. In order to improve the transmission of such a device, and so the achievable current, a 3D simulation of electron trajectories taking into account space charge effects was performed for typical three lenses cathode systems, electrostatic cylindrical deflector analyzer (CDA 127°) and acceleration lenses. The results of the analysis are presented and their effects on the overall design of the device are discussed.
Aldo Canova, Giambattista Gruosso and Maurizio Repetto
The synthesis of electro‐mechanic actuators is formulated as a constrained optimization problem where some performance function of the device is to be met, subject to the…
Abstract
The synthesis of electro‐mechanic actuators is formulated as a constrained optimization problem where some performance function of the device is to be met, subject to the satisfaction of some constraints about its dimensions and supply conditions. The optimization problem is tackled by means of a genetic algorithm coupled to a multi‐objective definition of the objective function that merge together objectives and constraints in one single scalar objective function. A fast magnetic analysis tool has been developed so that the computational cost of the genetic optimization run is acceptable. Some results about the synthesis of a tubular linear motor in two sizes are presented and discussed.
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Th. Ebner, Ch. Magele, B.R. Brandstätter, M. Luschin and P.G. Alotto
Global optimization in electrical engineering using stochastic methods requires usually a large amount of CPU time to locate the optimum, if the objective function is calculated…
Abstract
Global optimization in electrical engineering using stochastic methods requires usually a large amount of CPU time to locate the optimum, if the objective function is calculated either with the finite element method (FEM) or the boundary element method (BEM). One approach to reduce the number of FEM or BEM calls using neural networks and another one using multiquadric functions have been introduced recently. This paper compares the efficiency of both methods, which are applied to a couple of test problems and the results are discussed.
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