Jean-Louis Coulomb

Interaction between ring-shaped permanent magnets with symbolic gradients: application to magnetic bearing system optimization

This paper presents a semi-analytical calculation of the interaction between magnetic bodies with ring shapes. It leads to fast and accurate evaluation of forces and torques but also to the symbolic expression of their gradients. Our method can be used to compute partial derivatives to address optimization needs. It has been implemented into CADES environment in order to be automatically available for end users. A very efficient optimization of a magnetic bearing system is demonstrated.

A New Method to Evaluate Residual Flux Thanks to Leakage Flux, Application to a Transformer

This paper presents a new method to estimate the residual flux in the magnetic circuit of a transformer, which is the key data to determine the ideal closing time for the re-energization of a transformer. The methodology described is based on the measurement with fluxgate sensors of the magnetic field induced by the leakage flux around a single-phase transformer.

Analytical model for external induction variations of a ferromagnetic cylinder undergoing high mechanical stresses in a low magnetic field of any orientation

This paper introduces an original approach for characterizing and modeling the external induction variation of a complex ferromagnetic structure undergoing magneto-mechanical effects. From the Jiles Law of Approach that describes the intrinsic magnetization changes due to magnetostriction, an expression of the law in terms of conveniently external measurable induction B is derived for thin ferromagnetic devices. Based on measurements of induction performed by external sensors on an internally pressurized cylinder, an analytical model is found. This model is then tested for any orientation of the magnetic field with respect to stress, from parallel to orthogonal .

Original article: Manifold mapping optimization with or without true gradients

This paper deals with the Space Mapping optimization algorithms in general and with the Manifold Mapping technique in particular. The idea of such algorithms is to optimize a model with a minimum number of each objective function evaluations using a less accurate but faster model. In this optimization procedure, fine and coarse models interact at each iteration in order to adjust themselves in order to converge to the real optimum. The Manifold Mapping technique guarantees mathematically this convergence but requires gradients of both fine and coarse model. Approximated gradients can be used for some cases but are subject to divergence. True gradients can be obtained for many numerical model using adjoint techniques, symbolic or automatic differentiation. In this context, we have tested several Manifold Mapping variants and compared their convergence in the case of real magnetic device optimization.

Conducted interferences of power converters with parametric uncertainties in the frequency domain

This paper presents a new methodology to analyse the conducted interferences of power converters when its parameters are described by probability density functions rather than numerical values. The methodology has several advantages when compared to classical approaches, such as Monte Carlo and Collocation methods. The results are presented as probability density functions and confidence intervals.

Inverse problem approach to characterize and model magnetization changes in a thin shell structure undergoing magneto-mechanical effects

Direct measurement of magnetization M inside a complex ferromagnetic geometry is generally impossible. In this paper, we propose to use an inverse problem algorithm to determine the law of variation of M for such structures, accounting for the magneto-mechanical effects it is undergoing. The analytical law obtained leads to an intrinsic characterization model of magnetostriction inside the structure. Validation of the approach is achieved on a prototype undergoing high mechanical stresses in low magnetic field, by comparison with the predicted magnetic signature in the vicinity of the prototype, and measurements performed on external magnetic sensors.

Framework for the optimization of online computable models

Purpose – The purpose of this paper is to make easily accessible models to test and compare the optimization algorithms we develop. Design/methodology/approach – For this, the paper proposes an optimization framework based on software component, web service, and plugin to exploit these models in different environments. Findings – The paper illustrates the discussion with optimizations in Matlab™ and R (www.r-project.org) of a transformer described and exploitable from the internet. Originality/value – The originality is to make easy implementation of simulation model and optimization algorithm coupling using software component, web service, and plugin.

Identification of ferromagnetic thin sheets magnetization: Use of gradient and potential measurements

Purpose – This paper aims to present the use of magnetic gradient, and magnetic potential measurements in the specific case of magnetization identification for a thin sheet. Usually, induction measurements are only used.Design/methodology/approach – After a brief description of the magnetic gradient and magnetic scalar potential notions, methods to calculate them are presented and validated. These two kinds of measurements are tested for a numerical identification case. Then, virtual measurements can be generated and used for inverse problem resolution. Advantages of using induction, magnetic gradient or magnetic potential measurements are then discussed.Findings – A previous method to solve inverse problem based on induction measurement has been increased by the capability of using other kind of measurements. A numerical approach has allowed to validate the use of magnetic gradient or magnetic scalar potential measurement as information sources.Originality/value – Usually, induction measurements are only...