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L. Krähenbühl - IEEE Xplore Author Profile

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This article proposes a circuit model (CM) to calculate the current along printed coils used in resonant wireless power transfer (RWPT). It considers a system composed of a metamaterial and two coplanar coils, transmitter (Tx) and receiver (Rx), respectively. First, a CM for the system is presented. Then, an analytical model is proposed to calculate the self-inductance of printed inductors, their ...Show More
This work proposes a circuit model to calculate the current along printed coils used in resonant wireless power transmission systems. The proposed formulation is based on the Neumann formula for calculating the mutual inductance between coils, and due to the generality of this approach, it can be applied to more complex structures such as metasurfaces. Finally, this formulation is used to calculat...Show More
Currently, the training in the lumbar epidural anesthesia procedure, a very common procedure, is mainly performed on patients under the supervision of experts. The reason for this situation is that the simulators that exist on the market are not realistic enough to efficiently learn this particularly haptic-sense-based gesture. To avoid this ethical issue and provide an efficient, repeatable, and ...Show More
We studied the harmonic magnetodynamic behavior (without free space wave propagation) of a resonant surface metamaterial, made of many identical and regularly arranged LC cells. The circuit model gives the exact solution, but it is not numerically efficient for simulating very large structures (e.g., 1000 × 1000 cells giving 106 unknowns with a full 106 × 106 matrix). For the first time, we highli...Show More
In this article, an unstructured-partial element equivalent circuit (PEEC) method for modeling electromagnetic thin regions is proposed. Two coupled circuits' representations are used for solving both electric and/or magnetic effects in thin regions discretized by a finite-element surface mesh. Dynamic effects across the thickness of the sheet are modeled by equivalent complex conductivity and rel...Show More
A test-case for examining the energy-based hysteresis model is presented. An experimental setup constituted of a E-E core transformer is built in order to study the vector hysteresis modeling and multiple harmonic signals in different configurations. Simulation results are compared to measurements made on a soft ferrite Mn-Zn and discussed.Show More
In order to predict magnetic quantities in the magnetic cores of electrical devices, scientists and engineers need hysteresis models sufficiently accurate. Whatever the chosen model, a parameter identification protocol has to be elaborated requiring specific material measurements. This article compares two parameter identification protocols for the same hysteresis model. The protocols, their input...Show More
Epidural anesthesia, despite being a relatively common medical procedure, remains quite demanding in terms of skills as it is mostly blind and thus heavily reliant on the haptic sensations. Although some training support solutions exist, anesthetists consider them mostly inefficient or impractical. A few attempts at creating a simulator for this particular procedure exist but each one lacks one of...Show More
Devices using power electronics are ubiquitous today and they are unfortunately intrinsic sources of electromagnetic interference. To address these electromagnetic compatibility problems at the initial design phase, a predictive method based on multipole expansion in spherical harmonics of the near field around each device was developed. To determine the basic expansions of a given source, a dedic...Show More
In the electromagnetic compatibility behavior of power electronic converters, parasitic magnetic couplings between components are one of the main causes of dysfunctions or poor filtering. These couplings may be either conducted or near-field interferences. To handle interaction problems, full knowledge of these magnetic couplings is essential. This paper is an overview of the work on near magnetic...Show More
The characterization of near-field couplings becomes an extremely important activity to optimize the best nominal performance of any electronic device in the presence of others. In order to handle the electromagnetic compatibility (EMC) problems at the initial design phase, a predictive method based on multipolar expansion in spherical harmonics has been developed. A new automatic measurement syst...Show More
An important way to decrease the EMC issue is to predict near-field coupling between components. The using of their electromagnetic equivalent model in spherical multipolar expansion, allow to calculate the near-field magnetic coupling. The method cannot be properly applied when the sources are too close. In this paper we use a spheroidal expansion system, propose to solve the problem which enable...Show More
In this paper the coupling of natural element method with the boundary element method (Hybrid NEM - BEM method) is proposed to solve the electromagnetic scattering problem. A dielectric cylinder is solved by the proposed approach and the results are compared with the analytical solution showing the usefulness and accuracy of the method.Show More
Using the method of multipolar expansion in spherical harmonics, the electromagnetic interference between two systems can be determined from their equivalent models. However, a multipolar expansion depends on the position of the origin: a bad choice can yield a complicated equivalent model, even for a simple source. As a consequence, the calculation of the coupling between two sources can also bec...Show More
In the electromagnetic compatibility (EMC) behavior of power electronic converters, it is important to predict the near-field coupling between the complex components (e.g., in EMC filter). Using the components of the near-field multipolar expansion of electromagnetic sources, the close magnetic coupling between two elements is determined from their equivalent model. In this paper, a new measuremen...Show More
This paper deals with the time-domain homogenization of laminated cores in 2-D or 3-D finite-element (FE) models of electromagnetic devices, allowing for net circulating current in the laminations (e.g., due to imperfect or damaged insulation). The homogenization is based on the expansion of the induction throughout the lamination thickness using a set of orthogonal polynomial basis functions (BFs...Show More
Progressive refinements of the current sources in magnetic vector potential finite-element (FE) formulations are done with a subproblem method. The sources are first considered through magnetomotive force or Biot-Savart models up to their volume FE models, from statics to dynamics. A novel way to define the source fields is proposed to lighten the computational efforts, through the conversion of t...Show More
In EMC behavior of power electronic converters, it is important to predict near-field coupling between the complex components (e.g. in EMC filter). By using the components of near-field multipolar expansion of electromagnetic sources, the close magnetic coupling between two sources is determined from their equivalent model. It is shown that the complete identification of all components of multipol...Show More
In line with the trend toward continuous miniaturization and price reduction, it is crucial to analyze the impact of uncertainties on the performance of electrical circuits. Performance is evaluated for the worst-case scenario and in the frequency domain by computing upper and lower bounds. The purpose is not only to propose a method for the worst-case tolerance analysis but also to provide an eff...Show More
We propose a non-linear steady-state model of irreversible electropermeabilization in a biological tissue. The non-linear problem is solved using a modified fixed point iteration. The unknown parameters are experimentally estimated from the observation of the necrosis on a potato tissue for different applied voltages. A variability study of the parameters involved in the model is performed.Show More
Progressive refinements of inductors are done with a subproblem method, from their wire or filament representations with Biot–Savart models up to their volume finite-element models, from statics to dynamics. The reaction fields of additional magnetic and/or conducting regions are also considered. Accuracy improvements are efficiently obtained for local fields and global quantities, i.e., inductanc...Show More
Transcutaneous Energy Transmitters (TETs) transfer wireless energy through an inductive link established between two pancake coils placed, respectively, outside and inside the body of a patient. The simulation of the misalignment between the coils must be performed in 3-D, e.g., with a Finite Element (FE) method. This paper introduces a homogenization method to minimize the cost of the expensive 3...Show More
A finite element subproblem method is developed to correct the inaccuracies proper to perfect conductor and impedance boundary condition models, particularly near edges and corners of the conductors, for a large range of conductivities and frequencies. Successive local corrections, supported by fine local meshes, can be obtained from each model to a more accurate one, allowing efficient extensions...Show More
The use of artificial organs completely implanted in the patient's body requires a transcutaneous energy transmitter (TET) design that provides more comfort and reliability to the patient, i.e., a TET as small as possible with the least increase of temperature and that meets several project requirements. The multiobjective genetic algorithm optimization method is used here to minimize volume and d...Show More
In the context of mechatronic systems design, this paper addresses a parameter tolerance synthesis with respect to specifications including output epistemic uncertainties. The methodology proposed here concerns uncertainties modelled with fuzzy logic. The procedure relies on output uncertainties propagation through an inverse model. Design parameter tolerance is then synthesized. The results are v...Show More