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A global sensitivity analysis (SA) method enhanced with a kriging surrogate model is considered in this work. To decide on the importance of many model parameters in the case of a functional output, the Sobol’ sensitivity indices—being functions of an independent variable—are to be calculated over a domain of interest. Since for expensive-to-evaluate models obtaining such a sensitivity map is highly computationally demanding, the number of required samples is reduced by a kriging approximation combined with an adaptive sampling strategy that exploits the probability information provided by the kriging model. The advantages of the approach are demonstrated through the example of an electromagnetic interference (EMI) filter. [ABSTRACT FROM AUTHOR]

Darwin’s model is a reduced form of Maxwell’s equations, where radiations are neglected, while inductive, resistive, and capacitive effects are still taken into account. In this article, we propose a method for the efficient modeling of electrically long, thin wires using a Darwin-based integral equation approach, thus keeping the number of DoFs and runtime low. This model provides further numerical techniques to efficiently take into account special inhomogeneities via the modification of the Green’s functions unlike in full-wave models. The benefits are discussed through the example of the automotive CISPR 25 measurement setup. [ABSTRACT FROM AUTHOR]

Integral equation (IE) methods have recently been proposed for the modeling of inductively coupled resonant wireless power transfer. These approaches usually result in a low number of degrees of freedom. However, their applicability is mostly limited to homogeneous background media. In the present contribution, integral formulations are extended to take certain foreign objects into account in the model. By using quasi-static approximations, homogeneous foreign objects of canonical shape (e.g., spheres, plates) modify the Green’s function such that it can still be analytically expressed; thus, the computational cost of the IE method remains low. The method is validated against 3-D finite-element simulation and experimental data. [ABSTRACT FROM AUTHOR]

A full-wave surface integral equation method is used for modeling coils in a wide frequency range. This is of high importance in the analysis of resonant wireless power transfer links, for example. This paper presents a nonlocal generalization of the impedance boundary condition (BC) concept by incorporating a 2-D model (using the finite element method here) of the quasi-static electromagnetic field within the wire. This yields a numerical approximation of the nonlocal impedance BC on the wire surface that holds true at any frequency. The 2-D eddy-current model has to be evaluated only twice at one frequency, which makes the scheme computationally efficient. The method accurately predicts the ohmic loss as shown by the validations against alternative methods. [ABSTRACT FROM AUTHOR]

A full-wave integral equation scheme for modeling resonant coils applied in wireless power transfer systems is presented. An A-\Phi formulation is applied with current and charge densities on the wire surface as unknowns. The method overcomes the limitation of the “thin-wire approximation” as it enables the unknowns to vary on the wire surface. Thus, proximity effects (that typically emerge when modeling dense windings) are taken into account. The numerical implementation of the formulation has smaller computation cost than, for example, finite element methods. The proposed scheme is tested against closed-form solutions and alternative simulations. [ABSTRACT FROM AUTHOR]

In non-destructive testing, model selection is a common problem, e.g., to determine the number of defects present in the inspected workpiece. Statistical model selection requires to approximate the marginal likelihood also called model evidence. Its numerical approximation is usually computationally expensive. Nested sampling (NS) offers a good compromise between estimation accuracy and computational cost. But, it requires to evaluate the forward model many times. Here, we first propose a general framework where data-fitting surrogate models are used to accelerate the computation. Then, improvements benefiting from surrogate modeling are introduced into the traditional NS algorithm to further reduce the computational cost. These improvements include the use of a sparse-grid surrogate model to deal with the “curse-of-dimensionality” in large dimensional problems and of the preestimated posterior space to save warming-up time. Based on eddy-current simulations, we show that this improved model selection approach has high model selection ability and can jointly perform model selection and parameter inversion. [ABSTRACT FROM AUTHOR]

A full-wave integral formulation has recently been proposed for the simulation of magnetically coupled resonant wireless power transfer (WPT) arrangements in homogeneous medium. In this paper, the formulation is extended to the case where two different types of dielectrics are separated by a planar interface. This configuration has extensive practical interest nowadays, especially for modeling biomedical WPT applications. The new formulation is based on a stationary approximation, which is valid at the typical operating frequencies. The proposed scheme requires much less computational resources compared with standard finite-element simulations. The results are validated against alternative simulations and measured data as well. [ABSTRACT FROM AUTHOR]

With resonant wireless power transfer systems in operation, objects and/or humans having divers material properties come into the vicinity of the resonant coils. To model such systems efficiently, a novel full-wave multisolver is developed where the tangentially continuous vector finite element (FE) method is coupled with a method of moments (MoM) technique. The MoM technique is based on an electric field integral equation specifically designed to model the singular behavior of the thin coil wires, while the FE method is used to model the scattered field due to material inhomogeneities. A simplified sequential solver similar to the scattered field formulation is derived from the linear system of the multisolver in order to be applied as an efficient preconditioner, thereby speeding up the solution time significantly. The impedance change due to the material inhomogeneities can be calculated directly by applying the reaction concept. This ensures that the accuracy of the impedance change does not depend on the relative magnitude of the impedance change compared with the total impedance. The performance of the multisolver is illustrated by solving a test problem with a helical coil and a dielectric sphere with moderate conductivity, and comparing the multisolver results with the full FE solutions. [ABSTRACT FROM AUTHOR]

A sparse grid surrogate model (or metamodel) is proposed to reduce the computational time involved by accurate electromagnetic (EM) simulators. Sparse grids have already been used in many applications for interpolation and integration. The method can treat a high ber of independent parameters that are intractable for many other techniques due to the curse of dimensionality. Beyond the conventional method, adaptive sparse girds are also studied. The capabilities are illustrated through the examples drawn from the EM nondestructive evaluation. [ABSTRACT FROM AUTHOR]

The subdomain perturbation (SDP) finite-element (FE) method is a very efficient numerical technique and it speeds up the analysis of magneto- and electroquasi-static problems significantly. In order to solve quasi-static Darwin models, the authors have recently developed a low-frequency stable FE A-V formulation that incorporates both capacitive and the inductive effects, thereby allowing solving for resonances. This article combines the Darwin FE formulation with the SDP strategy at the first time. It successfully validates the combined technique and demonstrates a significant run-time improvement compared to the full Darwin FE solution. The breakdown of the Darwin approximation at higher frequencies is also investigated. [ABSTRACT FROM AUTHOR]

The change in the two-port parameters of a wireless power transfer (WPT) chain is evaluated when an object (foreign object) with given material parameters is placed in the vicinity of the WPT transmitter and receiver. An integral formula for the change of the two-port parameters due to the presence of a foreign object has been derived by using the generalized theory of reciprocity. It is emphasized that—instead of taking the differences of the two-port parameters calculated with and without the presence of the foreign object—the presented method provides the change of the two-port parameters directly from the calculated electromagnetic field at the location of the foreign object. As a result, the relatively small parameter changes can be predicted with good accuracy. Based on the application of the Born approximation, the possibility of computing an approximation of the changes of the two-port parameters is explored. [ABSTRACT FROM AUTHOR]

An integral equation method is used for the modeling of electromagnetic scattering from a rotating propeller, of which the length is about half a wavelength. This provides a convenient way of calculating its backscattering spectrum that is useful, for example, when radar detection capabilities are studied. This theoretical model is used to predict the discrete nature of the scattered spectrum and the intensity of its peaks. The simulations are compared with anechoic chamber measurements for different orientations of the propeller’s axis with respect to the polarization of the incident wave. [ABSTRACT FROM AUTHOR]

An efficient method is proposed for the numerical simulation of the bundle-level skin effect and its consequences arising in certain types of litz wires. The method is based on a probabilistic approach. The theory presented allows characterization of the repartition of currents between bundles and predicts some unexpected unique features. The method is tested on a coil unit that is used for inductive wireless power transfer. Simulations are verified by experimental data. [ABSTRACT FROM AUTHOR]