M.E. Mognaschi

Industrial Design With Multiple Criteria: Shape Optimization of a Permanent-Magnet Generator

The purpose of the paper is to demonstrate that the multicriteria formulation of an inverse problem fits well with current industrial electromagnetic design. The optimal shape design of a permanent-magnet (PM) generator is developed as the case study. Two well-known evolutionary algorithms, NSGA-II and MOESTRA, have been implemented and relevant results compared.

Biogeography-Inspired Multiobjective Optimization and MEMS Design

A new version of the biogeography-based optimization algorithm is proposed in order to consider multiple objectives. In fact, by exploiting non-dominated sorting of habitats, it is possible to approximate Pareto-optimal solutions in the objective space. The optimal shape design of an electrostatic micromotor, which is a benchmark in the Micro Electro-Mechanical Systems design, is considered as the case study.

Multiphysics field analysis and multiobjective design optimization: a benchmark problem

A magneto-thermal inverse problem, dealing with the optimal design of an induction heating device, is proposed as a benchmark. The coupled-field problem is analysed by means of a higher order finite element method. Then the optimal design problem is solved in terms of the Pareto front trading off two conflicting objective functions.

Recent experiences of multiobjective optimisation in electromagnetics

Purpose – The aim of this paper is to compare different methods for multiobjective optimisation with respect to the same benchmark problem.Design/methodology/approach – The following methods are considered: equilibrium of gradients GB, multi‐individual multi‐objective evolution‐strategy MOESTRA, and goal attainment GATT, respectively. They are applied to the shape design of the pole pitch of an electrical machine, with the aim of maximizing the air‐gap induction and minimizing the stray field in the winding.Findings – The same initial solution of the benchmark is considered for all methods. The final solution of GB and MOESTRA dominates the initial one because both objectives are improved. GB is the most expensive method and therefore is not suited when several non‐dominated solutions should be identified. Accordingly, the trade‐off curve was approximated by means of 15 non‐dominated solutions, resorting to MOESTRA.Originality/value – A multi‐objective multi‐individual evolution strategy of lowest order h...

Sorting Pareto solutions: a principle of optimal design for electrical machines

Purpose – The purpose of the paper is to show that the a posteriori analysis of the Pareto front associated with a given design problem facilitates the task of the decision maker and possibly helps to identify innovative solutions. The idea is to investigate the similarities existing among non‐dominated solutions.Design/methodology/approach – A permanent‐magnet alternator for automotive applications is considered as case study. The design problem exhibits six design variables and two energy‐related objective functions. A suitable sampling of the objective space is made and non‐dominated solutions, located along an L‐shaped front, are approximated. Results are assessed by means of a successive optimization using NSGA‐II algorithm.Findings – From the approximated Pareto front, three optimal devices have been selected and remapped in the design space in order to compare their performance. This is done in terms of iron and copper losses, material costs, rated voltage, and air‐gap induction. Moreover, making t...

Comparison of multi‐objective optimisation approaches for inverse magnetostatic problems

Purpose – The aim of the paper is to compare two different approaches to multi‐objective optimisation in magnetostatics; in this way, the case study is investigated as a possible benchmark.Design/methodology/approach – A Tabu search method modified with e‐constraint algorithm is compared with a multi‐objective multi‐individual evolution strategy. The case study is the automated shape design of a magnetic pole. In order to reduce the computational cost of solving the direct problem, which requires repeated analyses of the magnetic field, a neural network has been used to approximate the objective functions that depend on the design variables.Findings – An approximation of the Pareto front for each method is obtained. A twofold comparison between the two methods is made, based on both the result accuracy and the computational cost.Originality/value – Two different methods were already tested on a case study proposed as a benchmark for multi‐objective optimization in magnetostatics. The paper represents a co...

Synthesizing a Field Source for Magnetic Stimulation of Peripheral Nerves

We have developed an automated method for optimizing the design of a coil for magnetic stimulation of peripheral nerves, acting on the current distribution of the coil. The method consists of these steps: 1 generating a 3-D finite-element model of a coil laid on a forearm; 2 solving the model for two parameters,f1 and f2 of the activating function, which is responsible for the peripheral nerve stimulation; and 3 starting from an existing prototype, applying an evolutionary algorithm to maximize f1 and minimize f2 . The final aim is to obtain a focused and strong stimulation. In order to determine robust solutions, the method considers a sensitivity constraint and obtains two solutions, one without the sensitivity constraint and the other taking it into account. In both cases, the objective functions are improved with respect to the existing prototype. In conclusion, we discuss the structure of the objective space.

Multiobjective design optimization of an excitation arrangement used in superconducting magnetic bearings

The paper deals with the design optimization of high temperature superconducting magnetic bearings (SMB). The described algorithm allows a multiobjective optimal design with respect to the geometries of the gap oriented excitation arrangement as well as the superconducting bulks.

A Source Identification Problem for the Electrical Activity of Brain |During Hand Movement

A field source reconstruction of the dipoles modeling the activated area of the brain, while a subject performs the task of the voluntary motion of the hand, is solved. Experimental data resulting from fMRI are used for constraining the position of the equivalent dipole.

Electrical resistance in inhomogeneous samples during electroporation

In electrochemotherapy (ECT), electric field is applied by means of needle pairs to the tumor tissue in order to permeabilize cell membranes and, as a consequence, enhance the effects of chemotherapeutic drugs. The target tissue is not homogeneous and the electric field, generated by the needle pairs, is strongly affected by the specific electrical characteristics of different tissues. This paper analyzes the effect of tissue in homogeneity by means of numerical models and suitable experiments.