Monday 28 February 2025, 16:15h

TEMF building: S2|17 room 103, Schloßgartenstraße 8, 64289 Darmstadt

Stéphane Clénet, PhD HdR, Ecole Nationale Supérieure d'Arts et Métiers (ENSAM), Institute of Technology · L2EP

Title: Model order reduction: recent advances and treatment of non-linearity

Abstract:

The numerical simulation of nonlinear magneto-quasistatic problems based on the Finite Element (FE) method can lead to huge computational times. Then, Model Order Reduction (MOR) approaches based on the Proper Orthogonal Decomposition (POD) coupled with an interpolation method enables to reduce the computational time, but can lead also to numerical instabilities. In this seminar, we propose to present and compare different interpolation methods to account for non linearities like the Discrete Empirical Interpolation (DEI) method, the Gaussian Newton Augmented Tensors (GNAT) method and the Energy-Conserving Sampling and Weighting (ECSW) method. First the principles of the POD will be presented in the linear case and then in the non linear case. Then, the three methods (DEI, GNAT, ECSW) will be detailed. To compare the methods, a reduced model of a squirrel cage induction machine will be considered. The three non linear reduced models are evaluated in terms of accuracy on global and local quantities of interest and speedup versus the FE model.

Monday 17 February 2025, 15:00h

online only

M.Sc. Michael Wiesheu

Title: On Simulation Challenges, Implementation Strategies and Benchmarks of Electric Machines

Abstract:

Simulating electric machines poses a difficult task, where several kinds of equations (field discretization, lumped circuits, motion) meet different conditions for couplings (field-circuit, rotor-stator) meet complicated boundary conditions (dirichlet, (anti-)periodic, floating) meet different necessary solution strategies (static, transient, harmonic) to solve the problem. This talk suggests one solution of how these challenges can be overcome by a modular approach based on primitive stamps and a general formulation of boundary conditions. The simulations results are compared to A01’s measurements of the PMSM and induction machine (see Fig. 1), which will serve as a benchmark. In addition, it is explored, how the NURBS machine geometries can be exported to other tools (such as GMSH). Discussions about other solution approaches within CREATOR to solve these challenges are warmly welcome.

Monday 10 February 2025, 16:15h

TEMF building: S2|17 room 103, Schloßgartenstraße 8, 64289 Darmstadt

Ana Hanić, PhD, University of Zagreb, Department of Electric Machines, Drives and Automation

Title: Design optimization strategies for direct-on-line permanent magnet generators

Abstract:

This lecture focuses on the mathematical modelling and design optimization of direct-on-line permanent magnet generators, a class of machines with challenging grid integration requirements. The optimization process addresses not only high machine performance but also the quality of operational trajectories and dynamic conditions necessary for grid compatibility. The lecture examines the formulation of goal and constraint function

Monday 27 January 2025, 14:00h

Robert-Piloty building (Hochschulstraße 10, S2|02-C110)

Dr.-Ing. Christopher Beck and Dr.-Ing. Philipp Hollstegge, Mercedes-Benz AG

Title: Digital E-Machine Development at Mercedes-Benz: An Insight into the Electromagnetic and Thermal Simulation

Abstract:

Im Rahmen dieses Vortrags wird ein Einblick in die digitale und multidisziplinäre E-Maschinen-Auslegung in der Vorentwicklung gegeben, um bereits in frühen Entwicklungsphasen die richtigen Parameter zur Erfüllung projektspezifischer KPIs zu ermitteln. Neben einem Überblick über die E-Maschinen Designoptimierung liegt der Fokus des Vortrags auf der Simulationsmethodik zur Analyse des thermischen und strömungsdynamischen Verhaltens von Elektromotoren

Thursday 23 January 2025, 13:30h

TEMF building: S2|17 room 103, Schloßgartenstraße 8, 64289 Darmstadt

Dr. Philipp Schulze, TU Berlin

Title: Energy-Based Modeling via Structured Formulations

Abstract:

In this talk, we discuss energy-based modeling approaches based on port-Hamiltonian and other structured formulations. Each of the considered structures encodes the energy balance of the system, which often implies other important system properties such as stability. We demonstrate the structures and their benefits for discretization and model reduction by means of analytical and numerical examples.

Monday 13. January 2025, 16:15h

TEMF building: S2|17 room 103, Schloßgartenstraße 8, 64289 Darmstadt

Dr.-Ing. Peer-Ole Gronwald, Volkswagen AG

Title: Traction Motor Cooling Systems

Abstract:

The lecture will present the various methods of cooling electric traction machines and their operating principles. Various cooling principles that can be found in the electric drive units of electric vehicles will be presented in more detail. Analytical and numerical methods for calculating these cooling principles will be described and discussed

Tuesday 16 December 2024, 16:15 Uhr

TEMF building: S2|17 room 103, Schloßgartenstraße 8, 64289 Darmstadt

Assoc. Prof. Dr. Martin Petrun from University of Maribor (Laboratory for electrical machines and control)

Title: Sensitivity of MTPA Control to Angle Errors for Synchronous Reluctance Machines

This talk will present the sensitivity of Maximum Torque Per Ampere (MTPA) control in Synchronous Reluctance Machines (SynRM) to angle errors, focusing on how deviations in the reference trajectory impact performance. We systematically analyzed this sensitivity using analytical and numerical methods, including the effects of magnetic saturation. We evaluated two MTPA control implementation schemes, with torque and current amplitude as reference variables, utilizing a template SynRM from the open-source simulation tool SyR-e. Results show that performance sensitivity to angle errors is moderately low near the MTPA trajectory, allowing for significant angle deviations with minimal performance loss. Magnetic saturation slightly increased this sensitivity, reducing the allowable error range by up to 25%. These findings suggest the potential for simplifying control implementations, reducing component costs through less precise position determination (sensor-based or sensorless), and achieving additional control objectives such as torque ripple reduction. Therefore, we further analyzed static control strategies to reduce torque ripple in SynRMs. The results show the feasibility of peak-to-peak torque ripple reduction, which could support the reduction of the fundamental component of torque ripple with active control approaches.

Friday 01 November 2024 ,10:00h

online only

Dr. techn. Jacques Zwar from TU Wien (Institute of Lightweight Design and Structural Biomechanics)

Title: Shape Optimization of CAD-Compliant Boundary-Conforming Microstructured Geometries

Abstract:

Recent developments in additive manufacturing have opened up a vast field of new design possibilities that cannot be fully exploited by traditional engineering methods. To address these challenges, this work provides methods for shape optimization of two-scale or microstructured designs compliant with CAD representations. It is based on a paradigm for constructing boundary-conforming microstructures through functional composition between splines that naturally conform to the external geometry. The microstructure is modeled using a volumetric representation, enabling IsoGeometric Analysis. The explicit nature of this method for construction allows for the computation of geometric derivatives, which are used to calculate sensitivities via an adjoint approach. The proposed framework is validated through applications in heat transfer and structural optimization.

Monday 1 July 2024, 16:15 Uhr

Prof. Dr. Peter Zaspel, University of Wuppertal, School of Mathematics and Natural Sciences, Scientific Computing and High Performance Computing

Title: Gaussian processes in light harvesting complexes

Abstract:

The molecular simulation of light harvesting complexes, i.e. systems of molecules that react on light, such as in photosynthesis or solar cells, is very computationally challenging. Multi-scale methods reduce the computational burden by formulating the underlying problem as a time-dependent Schrödinger equation in the molecules. Still, highly accurate quantum chemistry calculations in larger complexes are computationally infeasible. In the talk, we present approaches to replace some of the computationally challenging calculations to build the involved Hamiltonian by kernel-based or Gaussian process regression models. Since even the construction of appropriate training sets may become computationally intractable, we develop multi-fidelity techniques to optimally combine training data that has been generated with different accuracies. Practical examples show that this can lead to substantial cost reductions. In addition, we show preliminary results towards approximations of (port-Hamiltonian) ODEs/PDEs by Gaussian processes. Hence, instead of predicting individual entries of the Hamiltonian, we learn / approximate the full Hamiltonian at once from the system's state space dynamics

Monday 24 June 2024, 15:15h

at the TEMF building (Schlossgartenstraße 8, S2|17-103)

Asst.Prof. Dipl.-Phys. Dr.sc.techn. Jan Hansen from TU Graz (Institute of Electronics)

Tilte: Electromagnetics and electric vehicles: How to predict the electromagnetic emissions of the electric power train

Abstract:

The road approval of electric vehicles is subject to strict electromagnetic emission limits. Electromagnetic theory has become indispensable for design optimization. The system complexity and the subtlety of the electromagnetic coupling paths still pose challenges. A mixture of deterministic (Maxwell) and statistical (machine learning) methods appears promising. In this lecture, an overview of the state-of-the-art of electromagnetic modeling for the electric power train is given, as well as several open problems.

Monday 17 June 2024, 14:00h

online only

Prof. Dr.-Ing. Simon Adrian from University of Rostock (Institute of General Electrical Engineering, Theoretical Electrical Engineering)

Title: Recent advances in the low-frequency stabilization of the electric field integral equation

Abstact:

The electric field integral equation (EFIE) is a popular means to solve electromagnetic scattering and radiation problems where the underlying geometry is a perfect electric conductor. Its popularity stems from the fact that open boundary conditions are naturally incorporated, only the surface of the geometry needs to be discretized, and no numerical pollution occurs. The discretization of the EFIE with the boundary element method and standard basis functions such as Rao-Wilton-Glisson functions lead, however, to a system matrix that suffers from the low-frequency breakdown: when the frequency is decreased, the condition number grows, leading to slowly- or non-converging iterative solvers. For extremely low frequencies, various round-off errors occur that prohibit an accurate solution. This talk discusses our latest progress in the stabilization of the EFIE: preconditioning techniques are presented that not only lead to a bounded condition number in the static limit but that, moreover, do not suffer from a flawed solution due to round-off errors. The approach is based on an implicit quasi-Helmholtz decomposition, and we demonstrate its effectiveness for various excitations and topologies of the underlying geometry. Furthermore, we show how the technique can be extended to a higher-order discretization leveraging B-splines.

Friday 14 June 2024, 12:00 Uhr

Prof. Gershon Elber, Technion, Israel Institute of Technology, Department of Computer Science

Title: Volumetric Representations (V-reps): the Geometric Modeling of the Next Generation

Abstract:

The needs of modern (additive) manufacturing (AM) technologies can be satisfied no longer by boundary representations (B-reps), as AM enables the manipulation and fabrication of interior (graded) materials as well as porosity. Further, while the need for a tight coupling between design and analysis has been recognized as crucial almost since geometric modelling (GM) has benn conceived, contemporary GM systems only offer a loose link between the two, if at all. For about half a century, since the 70’s, (trimmed) Non Uniform Rational B-spline (NURBs) surfaces have been the B-rep of choice for virtually all the GM industry.  Fundamentally, B-rep GM has evolved little during this period and is no longer able to fulfill the needs of modern (additive) manufacturing, namely heterogeneity and lattice/porosity support. In this talk, we seek to examine an extended (trimmed) NURBs volumetric representation (V-rep) that successfully confronts the existing and anticipated design, analysis, and manufacturing foreseen challenges.  We extend all fundamental B-rep GM operations, such as primitive and surface constructors and Boolean operations, to trimmed trivariate V-reps.  This enables the much-needed tight link to (Isogeometric) analysis (IGA) on one hand and the full support of (porous, heterogeneous, and anisotropic) modern/additive manufacturing needs on the other.

Monday 10 June 2024, 13:30 Uhr

Room: S2|17 27

Moritz Hartmann, Institute for Maritime Energy Systems, German Aerospace Center (DLR), Germany

Title: Galerkin-type time-domain coupled boundary element method for the analysis of wave-body dynamics in hydrodynamic applications

Abstract:

As the assessment of motions and wave loads on ships and offshore structures is relevant e.g. in the research and development of innovative concepts, in the design process, or the optimization of offshore operations, the development of fast and accurate numerical methods is of interest. Having in mind an assistance tools for ship and offshore operations by accompanying deterministic observations of the surrounding sea state for forecasting the future body motion to identify valid operational time frames, a real-time capable and precise algorithm is of interest. To reach the target of efficiency and accuracy, the time-domain coupled Boundary Element Method (cBEM) is conceptualized. The two-dimensional, linear prototype is introduced in the presentation and the monolithic coupling of wave and body motions is outlined. The main focus is set in detailing the incorporation of an efficient and accurate wave dynamic solver in the Galerkin boundary integral equation framework, the definition of the mixed boundary value problem with appearing surface discontinuities, and the assembly of boundary integral operators including the desingularization of hypersingular kernel functions. The validity of the approach is underlined by presenting results of analytical and hydrodynamic test cases and future development steps are discussed

Tuesday 21 May 2024, 13:00 Uhr

S2|17 27

Anouar Belahcen

Title: Research activities in computational electromechanics at Aalto University

Monday 8 April 2024, 16:30 UHr

SR Betonbau (NA01158F), Lessingstraße 25, 1. OG, Graz

Michael Loibl from the Universität der Bundeswehr München will give a talk on „Patch-wise quadrature of trimmed surfaces in Isogeometric Analysis”

Monday 11 March 2024, 16:15h

at the TEMF building (Schlossgartenstraße 8, S2|17-103)

Benjamin Rodenberg, M.Sc., from the Technical University of Munich (Chair of Scientific Computing, Group-Bungartz)

Title: Waveform iteration in partitioned multiphysics with preCICE

Abstract:

With its new version, the partitioned multiphysics library preCICE introduces a user interface that supports higher-order and multirate time stepping. In this talk, I will explain how preCICE uses an approach that is a variant of waveform iteration for this purpose. The user interface of preCICE allows coupling independent solvers, such as OpenFOAM or FEniCS, to solve a multiphysics problem collaboratively. Our approach does not require exchanging expert knowledge or implementation details across the API. Simultaneously, it supports higher-order time-stepping schemes. To evaluate this approach, we used academic example cases from mechanics, heat transfer, and fluid-structure interaction that I will present to the audience. preCICE, as well as the presented example cases, are open source and available on www.github.com/precice (http://www.github.com/precice).

Monday 5 February 2024, 16:15 Uhr

at the TEMF building (Schlossgartenstraße 8, S2|17-103)

Prof. Dr. Barbara Verfürth from the University of Bonn will talk about

Title:Numerical homogenization for wave propagation in metamaterials

Abstract:

Metamaterials are artificially constructed materials with fine composite structures that can have astonishing effective properties. The numerical simulation of wave propagation in such media is challenging because the fields can oscillate on small spatial scales. In this talk, we present the core ideas of some computational multiscale methods that allow to simulate the overall macroscopic behavior of the fields. A special focus will be on media with high contrasts between the material components. Numerical experiments illustrate some unusual wave phenomena caused by resonance effects

Wednesday 17 January 2024, 16:30 Uhr

SR Betonbau, Lessingstraße 25, 1. OG (NA01158F)

D. Seibel from Saarland University

Title: “Calculation of matrix entries in Galerkin boundary element methods”

Abstract:

In this presentation, we introduce explicit formulas for the calculation of matrix entries within the context of Galerkin boundary element methods (BEM) in 3D. The computation involves integrating singular kernel functions over pairs of surface panels, which becomes challenging when these panels intersect. While coordinate transformations can eliminate singularities, the use of numerical integration remains expensive since the integrals are still four-dimensional. Our proposed alternative approach employs analytical calculations for the standard Galerkin discretization of the Laplace equation, focusing on piece-wise constant and linear boundary elements on flat triangles. We demonstrate that employing the Duffy transformation yields regularized integrals with closed and exact formulas for the cases of identical triangles and triangles sharing a common edge. In the remaining cases, we reduce the integrals to one- or two-dimensional counterparts. This method enables accurate computation of matrix entries while

Monday 15 January 2024, 16:15h

at the TEMF building (Schlossgartenstraße 8, S2|17-103).

Prof. Brahim Ramdane from Univ. Grenoble Alpes, G2Elab

Title: Some research works about the volume integral method applied to the superconducting materials modelling and about the development of an Isogeometric FEM-BEM coupling for magnetostatic problems modelling

Abstract:

The talk will focus on three points: – First, I will present briefly our research group (Models, Methods and Methodologies Applied to Electrical Engineering) of the G2ELAB (Grenoble Electrical Engineering laboratory). – Then, some works about the development of a volume integral formulation based on a generalization of the PEEC method (Partial Element Equivalent Circuit) for the superconducting materials modelling will be developed and detailed. This can be achieved by the use of finite element facet interpolation for the current density. Several strengths appear with this approach. The method which is both light (we don’t require to mesh the air) and precise, ensures highly the conservation of current and therefore leaves hope for a good performance in solving highly nonlinear problems. – Finally, an Isogeometric FEM-BEM coupling for magnetostatic problems modelling using magnetic scalar potential will be presented. In fact, the application of the Isogeometric context to electromagnetic problems leads to the Isogeometric representation of air region, a particularly ineffective process. To overcome this hindrance, in a magnetostatic context, a magnetic scalar potential Finite element – Boundary element coupling will be presented. Numerical considerations and implementation specificities will be discussed, and the efficiency of the method will be demonstrated.

Thursday 14 December 2023, 11:40 Uhr

Prof. Albert E. Ruehli, Missouri University of Science and Technology, Rolla, USA

Title: 50 Years of the Partial Element Equivalent Circuit (PEEC) method

Abstract:

The PEEC method establishes a connection between circuit analysis and the EM solution for integral equations. PEEC results in the full spectrum solutions from dc to high frequencies. The original version of this work was developed in 1972. Much progress has been made over the years in the advancement of the practical utility of the method. The aim of this presentation is to give an overview of the approach and its practical development over the years. The further development of PEEC was in parallel to the requirements for the electrical modeling of computer chips and packages.

Thursday 7 December 2023, 16:00 Uhr

online only

Bernard Kapidani from EPFL, Lausanne, who works in the group of Annalisa Buffa (“Numerical Modelling and Simulation” – High order FIT for the Maxwell equations: a tale of two approaches

Abstract:

The celebrated Finite Integration Technique for the time integration of Maxwell’s equation has enjoyed a lot of success due to its computational efficiency. In recent years several ways to overcome its limitation to linear convergence in the mesh size have been proposed. I will explore two main roads to achieve this enhancement: one based on spline complexes of differential forms and one based on staggered discontinuous Galerkin methods. Both approaches are rooted in insights from the low order classic approach and preserve its amenable properties of energy conservation, explicit in time integration and absence of spurious numerical solutions

Monday 13 November 2023, 16:15h

at the TEMF building (Schlossgartenstraße 8, S2|17-103).

Prof. Paavo Rasilo from Tampere University

Title: Some Approaches for Core Loss Modeling in Electrical Machines and Magnetic Materials

Abstract:

Power losses in laminated magnetic cores of electrical machines are usually modeled by so-called dynamic hysteresis models, that describe the relationship between the average magnetic flux density and the surface magnetic field strength in the lamination. I will discuss some aspects related to deriving such dynamic hysteresis models and implementing them electrical machine simulations. Applicability of such models to other kind of magnetic materials used in higher-frequency applications will also be discussed.

Friday 10 November 2023, 10:45h

at the TEMF building (Schlossgartenstraße 8, S2|17-103)

Prof. Dr.-Ing. Ulrich Römer from TU Braunschweig

Title: Uncertainty Quantification for Frequency Domain Problems with the Stochastic and Statistical Finite Element Method

Abstract:

This talk is concerned with vibroacoustic modeling in the frequency domain to model, e.g., aircraft noise. We first introduce a fluid-structure coupled model problem, where we associate a probability density function to uncertain model input parameters. Then, we introduce a surrogate model, which features local interpolation of reduced order models (ROMs) on a sparse grid. In this way, we can handle a large number of input parameters and the local ROMs allow for sweeping over frequency intervals of interest. The overall surrogate is constructed in a fully adaptive way, where the accuracy is controlled with adjoint error indicators. We will illustrate how the surrogate can be used to propagate uncertainties through the vibroacoustic model and finally outline how data can be assimilated with a statistical finite element formulation.

Monday 23 October 2023, 16:15h

at the TEMF building (Schlossgartenstraße 8, S2|17-103)

Prof. Christophe Geuzaine from the University of Liège

Title: Efficient modelling of ferromagnetic laminations using homogenization and neural networks

Abstract:

Eddy currents and magnetic hysteresis in individual laminations of ferromagnetic cores are usually outright disregarded when simulating electromagnetic energy conversion systems. The associated magnetic losses are then only evaluated a posteriori, by means of Steinmetz-like formulas. This approach however yields seriously inaccurate computed fields and losses whenever the operating frequency increases, or in the presence of higher harmonics. In this presentation I will introduce a pragmatic multiscale modelling approach based on homogenization and neural networks, which can be easily implemented in standard finite element software. We demonstrate the efficiency of the algorithm, in particular for a large number of optimization variables and a large number of uncertainties.

Wednesday 11 October 2023

HS i6, Inffeldgasse 25, 1 OG, TU Graz

Anna Melina Merkel

Title: Isogeometric Analysis for the Simulation of Rotating Electric Machines

Abstract:

In the simulation of electric machines, the accuracy of the magnetic field in the air gap between stator and rotor is important to correctly predict the behavior and performance of the machine. In the standard finite element case, the cylindrical structure of electric machines is approximated by piecewise polynomials, introducing a geometry error. This error can be avoided using isogeometric analysis (IGA), where the geometry is described exactly using NURBS. One bottleneck of IGA is the time-consuming geometry discretization which often has to be carried out manually. To avoid the need for rediscretizing the geometry during rotation of the machine in order to obtain a conforming patch-wise discretization, we investigate methods that can deal with non-conforming discretizations, such as mortaring, in the context of IGA. Furthermore, we explore treecotree gauging to remove the kernel of the discrete system based on the magnetic vector potential formulation. The obtained formulation allows for the straightforward use of higher-order basis functions and enables an accurate and efficient simulation of rotating electric machines.

Thursday July 06 2023, 10:00 am

TEMF building: S2|17 room 103, Schloßgartenstraße 8, 64289 Darmstadt

Prof. Wil Schilders

Title: Mathematics: key enabling technology for scientific machine learning

Abstract:

Wil Schilders is a Full Professor (Emeritus since two weeks) and Chair of Scientific Computing in the Industry in the Department of Mathematics and Computer Science at Eindhoven University of Technology (TU/e). His research focuses on numerical linear algebra, indefinite systems, model order reduction, scientific computing, discretisation techniques, boundary element method, singularly perturbed problems, exponential fitting, uniform methods, solution of nonlinear systems, nonlinear variable transformations and numerical methods for the simulation of semiconductor devices and electronic circuits. Wil’s key areas of expertise include computer systems, architectures, networks, numerical analysis, model order reduction, scientific computing and computational science. He has worked in industry for over 30 years and his emphasis has always been on the development of novel mathematical methods for a large variety of industrial challenges. This is also reflected in his current work, with many national and international industrial contacts, and his presidency of ECMI, EU-MATHS-IN and soon ICIAM.

Wednesday 28 June 2023

Room HS i6, Inffeldgasse 25/D, 1.OG

Prof. Laurent Daniel from Group of Electrical Engineering Paris, CNRS, CentraleSupélec, Université Paris-Saclay, Sorbonne Université

Title: Multiscale approach for magnetic materials

Abstract:

Prof. Laurent Daniel from Group of Electrical Engineering Paris, CNRS, CentraleSupélec, Université Paris-Saclay, Sorbonne Université (see https://pageperso.geeps.centralesupelec.fr/index.php?page=laurent-daniel-en) will visit us and is going to hold a seminar on “Multiscale approach for magnetic materials”