Emanuele Dilettoso

A self-adaptive niching genetic algorithm for multimodal optimization of electromagnetic devices

A new niching genetic algorithm (NGA) called self-adaptive NGA (SANGA) is proposed. The main innovation is that the niche radius is estimated as an additional variable of the optimization problem and is not assigned a priori, as is usually done in other standard NGAs. SANGA, coupled with the deterministic pattern search method, forms a hybrid optimization method which works well in the optimization of multimodal functions and in the design of electromagnetic devices

Finite-element solution of eddy-current problems in unbounded domains by means of the hybrid FEM-DBCI method

A hybrid method, called finite-element method-Dirichlet boundary-condition iteration (FEM-DBCI), is described for the finite-element solution of time-harmonic eddy current problems in three-dimensional unbounded domains. The procedure couples a differential equation for the interior problem in terms of the electric field with an integral equation for the exterior one, which expresses the Dirichlet condition on the truncation boundary. The global algebraic system is efficiently solved in an iterative way. FEM-DBCI leads to shorter solving times and not much higher memory requirements with respect to the FEM-boundary-element method.

An Iterative Solution to FEM-BEM Algebraic Systems for Open-Boundary Electrostatic Problems

This paper shows that the global system of equations in the hybrid FEM-BEM solution of open-boundary electrostatic problems can be efficiently solved in an iterative way by making use of the conjugate gradient solver for the FEM equations and the direct LU solver for the BEM equations. To do so, it is convenient to implement the BEM equations in a non-conventional way, by making the nodes for the potential non coinciding with the nodes for its normal derivatives

A proposal for a universal parameter configuration for genetic algorithm optimization of electromagnetic devices

Genetic algorithms (GAs) are widely used in the optimization of electromagnetic devices. However, if finite element analyses are needed for the evaluation of the objective function, GAs require a long computation time. They also need a difficult tuning session before starting optimization, to select the best configuration of the parameters that control the algorithm. This paper proposes a universal choice of the GA parameters in order to spare the designer the tuning session and to reduce the computing time for the whole procedure.

A Parallel Version of the Self-Adaptive Low-High Evaluation Evolutionary-Algorithm for Electromagnetic Device Optimization

The self-adaptive low-high evaluation evolutionary-algorithm (SALHE-EA) is used to solve multimodal optimization problems. SALHE-EA is able to find the multiple optima of a single objective function (OF) and to give an idea of the fitness landscape in the neighborhood of these optima. This aspect is of crucial importance when the single OF is obtained using the weighted sum of the OFs, each related to a different goal of the optimization problem. This paper presents an improved version of SALHE-EA. This new version has several new features and, mainly, the suitability for parallelization.

Improving the accuracy of the integral equation in the hybrid FEM-DBCI method for open boundary electrostatic problems

In this paper, the accuracy of the integral equation of the hybrid finite-element-method-Dirichlet boundary condition iteration method is improved for the computation of open boundary electrostatic fields. This is achieved by selecting the integration curve (or surface) as lying in the middle of the triangular (or tetrahedral) elements. A notable improvement in accuracy is obtained compared with selecting the integration curve (or surface) as constituted by element sides

Simulated annealing with restarts for the optimization of electromagnetic devices

The simulated annealing (SA) algorithm is often used in the optimization of electromagnetic devices, but in multi-modal continuous problems it may be affected by premature convergence. This paper proposes an improvement to prevent the algorithm from becoming trapped in local minima, called SA with restarts. This algorithm allows an enhancement of performance and a reduction in computing effort, appreciated especially in the optimization of electromagnetic devices, where the single evaluation of an objective function calls for the numerical solution of an electromagnetic field problem

A GMRES iterative solution of FEM‐BEM global systems in skin effect problems

Purpose – This paper aims to extend an efficient method to solve the global system of linear algebraic equations in the hybrid finite element method – boundary element method (FEM‐BEM) solution of open‐boundary skin effect problems. The extension covers the cases in which the skin effect problem is set in a truncated domain in which no homogeneous Dirichlet conditions are imposed.Design/methodology/approach – The extended method is based on use of the generalized minimal residual (GMRES) solver, which is applied virtually to the reduced system of equations in which the unknowns are the nodal values of the normal derivative of the magnetic vector potential on the fictitious truncation boundary. In each step of the GMRES algorithm the FEM equations are solved by means of the standard complex conjugate gradient solver, whereas the BEM equations are not solved but used to perform fast matrix‐by‐vector multiplications. The BEM equations are written in a non‐conventional way, by making the nodes for the potenti...

A Modified FEM-DBCI Method for Static and Quasi-Static Electromagnetic Field Problems

This paper presents a modified version of the hybrid FEM-DBCI (Finite Element Method-Dirichlet Boundary Condition Iteration) method to solve static and quasi-static electromagnetic field problems in open boundary domains. The modification consists of overlapping the fictitious truncation boundary with the integration one, as in the FEM-BEM (Boundary Element Method) method. The global algebraic system obtained is solved iteratively by means of the GMRES (Generalized Minimal Residual) solver, applied virtually to a reduced system in which the unknowns are those relative to the potential on the truncation boundary only. Some validation examples are provided.

Transient Thermal Analysis of an Eddy-Current Heated Conductor Applying FEM-DBCI

A method is proposed for the computation of the transient heating of a conductor in which eddy currents flow, induced by time-harmonic source currents. The electrical field is assumed as unknown on a mesh of edge elements and is computed by a time-harmonic analysis. The heating power density inside the conductor is computed and a transient thermal analysis is started on the same mesh of nodal elements. This analysis is continued until the temperature-dependent electrical conductivity changes enough to require another time-harmonic eddy-current analysis. The combined procedure is iterated.