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Current results of research or teaching activities

Diss.: Methodics for design of wound rotors in permanently excited axial flux machines

The current electrification in automotive technology and industry necessitates the best possible utilization of the available installation space. Due to the high built-in storage capacities with a simultaneous low energy density, attempts are being made to accommodate the drives in previously unused and unsuitable installation spaces for energy storage. Axial flux motors can be suitable for this issue because of their disc-shaped construction. In addition, they offer a higher torque density than radial flux motors with the same diameter.For radial flux machines, electrical sheet metal layered in the direction of the rotor axis is used to reduce stray fields. The individual layers are aligned parallel to the direction of the magnetic flux. For conventional axial flow machines, the alignment must be adjusted accordingly. Radially aligned the sheets would be necessary to be produced with non-constant thickness. That is why steel disks with SMC elements are used as rotors to compensate for stray fields between the magnets in practice.For axial flux machines, layered electrical sheet metal with constant thickness can still be used. Instead of the steel disc, sheet metal wound on a hub can be used, onto which the magnets are glued. However, this means that the wound rotor has to absorb the entire load. Conventionally, one would calculate the entire assembly with an FEM. The difficulty, however, is that the metal strip can be several hundred meters long and has many contact points with itself. Therefore, it is very complex to model the problem with FEM. In addition, this problem converges very slowly, and the evaluation takes a lot of time.To avoid solving the complete problem with the FEM, the problem itself is modified in this work. Instead of the spirally wound electrical steel sheet, sheet metal rings are pulled onto a hub. The mounting of a ring on a hub can be solved analytically and the behaviour of such bandages is known and used in practice. The properties and the calculation are published i.e. in DIN7990. This approximation is justified in this thesis by the fact, that there is an asymmetry in the load capacity with regard to the load direction. This is due to the spiral shape of the sheet. The coefficient of friction is different in the ring modelling, but these errors can be compensated by adapting the coefficient of friction and these errors are negligible small.It is obvious that the modelled sheet metal rings may be regarded as infinitely thin due to the low thickness of conventional electrical steel sheets compared to the other dimensions. This allows more general statements to be made and the errors that occur are characterized and the limits of applicability are determined.In the next step, the load limits for different possible types of loading are determined and the form in which the prestressing must be carried out in order to achieve simultaneous failure in every layer. It is also shown that not only plasticizing is a failure criterion, but that lifting of the individual layers from one another leads to a loss of prestress and thus a failure.In order to be able to predict where and in what way the rotor will fail, general diagrams are developed for the wound rotor and drum. Limits to the possible number of layers are also sought before plasticizing occurs during the winding itself.The magnetic pockets can be produced either before winding by cutting out the pockets in the sheet metal strip itself or after winding by milling out of the rotor. The former is preferred for series production, while the latter is preferred for test bench verification of prototypes. Due to the different production, however, there is a change in the preloading and therefore a change in the load capacity of the rotor. These differences and effects are examined.How strong a rotor can be loaded depends, among other things, on the shape of the magnet and the way the magnetic forces are transferred through the adhesive layer into the rotor itself. To investigate this, an algorithm is presented that models the adhesive layer as a FEM model. Deformations are applied in three characteristic directions and the algorithm is used to convert the stresses into a force distribution curve that can be used for numerical analysis. Additionally, curves for simple magnet shapes and a method for determining the magnet shape based on the curve are presented.The main parameter of the load capacity of the rotor is the pre-tensioning force during winding. To check this during production, the ideal position of a deformation measurement for hollow hubs is derived depending on the geometry. Changes in the stress curve when using hollow hubs are also shown. Slotted hollow hubs can approximate hollow hubs with axial screw connections.This method is implemented as a Matlab script. This and the implementation details are explained within the commented code.The entire algorithm requires many material and geometry-dependent parameters. The effect on the torque characteristic is examined using an example. An example how the algorithm can be used to select a suitable electrical steel sheet is presented.
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Diss.: Generic visualization approach for SysML models in PDM systems

Authoring tools for creating system models using the Systems Modeling Language (SysML), like CAD tools, use proprietary, mutually incompatible formats for model data storage. The XMI standard available for model data exchange between different editors has degrees of freedom for its implementation, which also leads to incompatibilities here. SysML model information can therefore often only be exchanged between development partners and other stakeholders and linked to further product models with great effort. In sufficiently complex development projects, the management of the different models and organization of the cooperative activities is done in product data management systems (PDMS), which can only display SysML model information with the help of authoring tool-specific plug-ins. The visualization approach presented here is intended to enable access to SysML model information of different generating editors directly in PDMS without additional software components requiring a license. 
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Bac. thesis: Optimization methods for the design of neural networks

Motivation / Starting point:
One challenge in the initialization of neural networks is to find optimal starting parameters.
Based on the use case of an existing modular neural network design, which simulates the behavior of a production plant, different optimization methods are to be tested in order to find those initial settings for which the network performance can be maximized.
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Bac. thesis: Looking at common software solutions for isolating applications on edge devices in an industrial environment using container-based virtualization

Container-based virtualization holds great potential for change for companies in the information technology sector. The driving forces are, among others, corporations such as Google, Microsoft and Amazon. However, the world of containers is also supported by an active developer community, which, supported by open standards, is laying a foundation for the use of containers. Since Docker popularized container technology in 2013, there has been a growing the number of existing offerings in this area continuously. This bachelor thesis aims to provide an overview of the different products and then compare them.
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Bac. thesis: Development of a criteria catalog for the evaluation of industrial edge devices for the performance of machine learning analyses

Motivation:
Edge devices are intelligent network components that play a central role in the autonomous control of production landscapes. The increasing miniaturization and rising performance of modern chipsets has made it possible to perform machine learning analyses on edge devices. As a result, a wide variety of manufacturers have developed corresponding devices or hardware extensions. The diversity of devices and their use cases makes their analysis and evaluation difficult. In this context, a catalog of criteria is needed that can be used to analyze and compare the edge devices.
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Bac. thesis: Evaluation of the state of the art of preprocessing methods in industrial application areas

Motivation:
As more and more data is created in the world and seemingly the whole world is connected, this bachelor thesis pays special attention to data analysis or data preprocessing. The data preprocessing step takes about 80% of the total time spent in a data mining process. The difficulty in this step is to identify valuable information or patterns from the large amounts of data. However, by carefully performing data preparation, a more reliable data analysis results. 
Since these growing volumes of data are often generated at the edge of the network, the possibility of local data processing is also considered. Due to network bandwidth and concerns about data privacy, it is often unnecessary and ineffective to send data to a remote cloud. 
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