CAMPUS PLATTLING

The Power Electronics Department, led by Prof. Dr.-Ing. Otto Kreutzer, conducts research into the following areas:

• Power electronics for e-mobility (motor vehicles, rail vehicles, etc.)
• High-performance, high-efficiency charging stations (in combination with energy storage solutions)
• DC/DC conversion in the context of electrolysers/fuel cells, as well as
• Smart Grid & Renewable Energies
• AC/DC conversion in 16.7 and 50 Hz grids
• DC/AC conversion in drive inverters for fuel cell systems and battery-electric drives
• The central task is the development and optimisation of power electronic converters tailored to the specific application.

RESEARCH PROJECT

Analyses, calculations, simulations and the preparation of circuit diagrams and assembly drawings form the basis of the research work.

This is followed by the production of the prototypes. For this purpose, there is a small workshop for mechanical work, a winding station for the in-house production of wound components, and the power electronics laboratory for all electronic work.

^{Pictured: Assembly of the SMD components on a step-up regulator}

^{Pictured: Assembly of through-hole components}

In order to achieve high circuit efficiency, passive components – such as inductors – must also be manufactured in-house to meet the required specifications.

Once the circuits have been completed, they are commissioned and all parameters are tested and measured. In power electronics, measuring efficiency is of particular importance.

Ultimately, the final test of the research work takes place in practice.

^{Pictured: Intelligent single-cell-based battery management system for a multi-level battery system}

EXAMPLES OF CURRENT CHALLENGES

• Establishment of a self-sufficient system involving the feed-in of solar energy and the storage of energy in the form of hydrogen
• Development of an underground DC fast-charging point that can be powered from the railway traction power supply network (15 kV, 16.7 Hz) (Rail-HPC)
• Direct charging of electric vehicles from photovoltaic systems (Direct PV)
• Various commissioned research projects

OVERVIEW OF EQUIPMENT

• 4-quadrant AC mains simulator
• Bidirectional DC power supplies
• SMD assembly station (stencil printer, automatic placement machine, reflow soldering oven, etc.)
• Vector network analyser
• Saturation current tester
• Partial discharge tester
• Thick-wire bonder
• High-voltage insulation tester
• etc.

The full overview can be found at: Power Electronics Facilities in Plattling

CURRENT FUNDED PROJECTS

Nefton / Nefton 3000 – Electrification of commercial vehicles for grid connection optimised for the transport sector; sub-project: Passively cooled, unidirectional power electronics

The NEFTON project is developing a fast-charging system for battery-powered commercial vehicles. To this end, a highly efficient, bidirectional charging point operating in the megawatt range is being developed. In addition, a vehicle prototype is being developed that optimally meets both the technical and customer-specific requirements.

Within the scope of this sub-project, the focus is on the truck’s charging point.

Rail-HPC – Underground fast-charging point for battery-electric passenger cars powered by the railway overhead line

The aim of the project is to develop a highly efficient, scalable fast-charging station for electric vehicles (HPC = High Power Charger) with a charging capacity of 50 kW, which can be powered directly from the overhead lines of the railway power supply network (15 kV, 16.7 Hz), but optionally also from the public electricity grid. Specialised power electronics therefore enable both power grids to be utilised.

Residual Charge – Development and highly automated production of a DC wallbox with single-phase control; sub-project: development of highly efficient, phase-accurate power electronics and AI-based process data analysis

This project involves the development of a DC wallbox that monitors the available residual capacity in the individual phases of existing domestic connections, utilises this capacity on a phase-by-phase basis and can respond to changes in load, thereby ensuring that the individual phases of the connection are utilised optimally. This requires the development of new power electronics and control technology.

Innovative educational subject – An innovative, collaborative and cross-border educational concept for university students in the field of teaching

COMPLETED PROJECTS

DirektPV

The research group led by Prof. DI Dr.techn. Michael Sternad focuses on the following research topics:

• High-power lithium-ion batteries
• Ageing effects, including those associated with fast charging of lithium-ion batteries
• Lithium-metal batteries with electrolytes based on ionic liquids
• Novel electrode morphologies (e.g. using laser patterning)

Publications by Prof. Sternad: Google Scholar  Web of Science  ORCID

SELECTED PUBLICATIONS

Tracing the Powerfade: Location and Quantification of the Fluoridic Solid Electrolyte Interphase on Graphite Anodes (243^rd ECS-Meeting, Boston, 2023)

^{Positive correlation between the thickness of the fluoride-based SEI and the direct-current cell impedance (DC impedance) of a 21700 cell}

Furtmair, M.; Wolters, A.; Simic, S.; Thannhuber, M.; Ruhl, G.; Sternad, M., Tracing the Powerfade: Location and Quantification of the Fluoridic Solid Electrolyte Interphase on Graphite Anodes. In 243rd ECS Meeting, Boston, USA, 2023.

A Lithium‐Silicon Microbattery with Anode and Housing Directly Made from Semiconductor Grade Monocrystalline Si

(Advanced Materials Technologies, 2021, in collaboration with Infineon Technologies Austria AG, published with funding from the European Union (European Regional Development Fund, ERDF))

^{Fully integrated lithium-silicon microbattery, using monocrystalline silicon as the anode and casing material}

Sternad, M.; Hirtler, G.; Sorger, M.; Knez, D.; Karlovsky, K.; Forster, M.; Wilkening, H. M. R., A Lithium‐Silicon Microbattery with Anode and Housing Directly Made from Semiconductor Grade Monocrystalline Si. Advanced Materials Technologies 2021.

Nascent SEI-Surface Films on Single Crystalline Silicon Investigated by Scanning Electrochemical Microscopy

(2019, in collaboration with Prof. G. Wittstock’s seminar group, University of Oldenburg)

^{Investigation of the formation of the surface electron-insulating layer (SEI) on a battery anode made of single-crystal silicon using SECM (Scanning Electrochemical Microscopy)}

dos Santos Sardinha, E.; Sternad, M.; R. Wilkening, H. M.; Wittstock, G., Nascent SEI-Surface Films on Single Crystalline Silicon Investigated by Scanning Electrochemical Microscopy. ACS Applied Energy Materials 2019, 2, (2), 1388-1392.

Aging of Tesla's 18650 Lithium-Ion Cells: Correlating Solid-Electrolyte-Interphase Evolution with Fading in Capacity and Power

(2017, in collaboration with AVL List GmbH)

^{Characterisation of a 18650 Tesla cell; investigation of ageing behaviour at different temperatures and C-rate charging conditions}

Uitz, M.; Sternad, M.; Breuer, S.; Täubert, C.; Traußnig, T.; Hennige, V.; Hanzu, I.; Wilkening, M., Aging of Tesla's 18650 Lithium-Ion Cells: Correlating Solid-Electrolyte-Interphase Evolution with Fading in Capacity and Power. Journal of The Electrochemical Society 2017, 164, (14), A3503-A3510.

The microstructure matters: breaking down the barriers with single crystalline silicon as negative electrode in Li-ion batteries

(Scientific reports, Nature Publishing Group, 2016)

^{A study of the fundamental electrochemical properties of single-crystal silicon (100) during lithiation}

Sternad, M.; Forster, M.; Wilkening, M., The microstructure matters: breaking down the barriers with single crystalline silicon as negative electrode in Li-ion batteries. Sci Rep 2016, 6, 31712.

AVAILABLE METHODS AND EQUIPMENT

Working in an inert atmosphere

• MBRAUN Labmaster Pro SP Glovebox (Argon, < 0.5 ppm H₂O)

Preparation of laboratory test cells (Swagelok cells, button cells, pouch cells)

• Fritsch PULVERISETTE 7 planetary mill (slurry preparation)
• Proceq ZAA 2300 automatic film-spreading apparatus (squeegee 80–100 mm)
• Low-vacuum drying line (p = 10⁻²–10⁻³ mbar), Büchi glass furnaces
• Metrohm 831 Karl Fischer coulometer with 860 KF headspace oven
• Mettler XSR105DU analytical balance (0.01 µg resolution)
• Swagelok, Knopf and Puchcell production

Electrochemical characterisation of laboratory test cells

• Biologic MPG 2 potentiostat, 2 x 16 channels
• Biologic SP 50 potentiostat, 1 channel
• Memmert temperature-controlled cabinets (25, 40, 60°C)

Electrochemical characterisation of industrial cells (e.g. 21700)

• Arbin LBT21084HC Battery Cycler, 40 channels, 0–5 V, 60 A
• High-precision temperature control unit for 18650/21700 cells (T ± 1 K under a 20 A load)

Chemical analysis, imaging techniques and other equipment

• Agilent Cary 630 FTIR/ATR spectrometer (diamond and Ge crystal optics)
• Agilent 8860/5977C GC-MS system
• Thermo Fisher NEXSA X-ray photoelectron spectrometer (XPS, TC-Teisnach)
• Zeiss Ultra 55 scanning electron microscope, EDAX EDS detector
• ZEISS METROTOM computed tomography scanner (5 µm spot size)
• Rotofix 32 A bench-top centrifuge (electrolyte sampling from battery cells)
• Access to Hg porosimeter, Dionex ion-exchange chromatography, flame and graphite furnace atomic absorption spectrometry (AAS), etc.

^{Glovebox, with a fine-vacuum drying line integrated into the fume cupboard}

^{Arbin High-Current Cycler}

^{Copper heat exchangers for the precise temperature control of battery cells during testing}

^{Manufacture of electrodes: coating of current-collecting foils with a so-called ‘slurry’ (a viscous mixture of active material)}

^{Laboratory calender for compacting the dried active material coating, with a finished electrode sheet in the foreground}

SERVICES

Qualification of battery cells:

Before a cell is used in a specific product, it is usually the responsibility of the cell manufacturer to demonstrate the quality and safety of its cells to, for example, an equipment or motor vehicle manufacturer (to ‘qualify’ them).

A typical battery qualification process includes:

• Cycle testing of the cells at 25, 40 and 60 °C, comprising 750 cycles under the charge and discharge conditions specified by the cell manufacturer (as per the specification sheet). Electrical and electrochemical parameters such as discharge capacity, Coulombic efficiency (charge efficiency) and AC (1 kHz) and DC (5 s, 20 A) impedance are recorded.
• The opening of one selected cell per temperature under inert gas in a glovebox (‘post-mortem analysis’):

1. a. Assessment of the macroscopic condition, particularly of the anodes (with regard to lithium plating) and the separators (short circuits or thermal anomalies, hotspots)
2. b. Detailed photographic documentation of all cell components (anodes, cathodes, separators, cell housings and safety devices)
3. c. Determination of the geometric parameters of the electrode tracks and the separator, including the thicknesses of the active material layers
4. d. Macroscopic inspection of the cell’s safety devices (e.g. the CID or the PTC)

• reporting accompanied by an expert assessment of the quality and safety of the tested cell design, to serve as a basis for decision-making for potential buyers of the cells

If you have any questions regarding ‘battery qualification’, the experts at AG Sternad will be happy to help!

Example of the results of a cycling test comprising 750 cycles (750 charge and discharge cycles) at 25, 40 and 60 °C:

^{Electrochemical experiment (cycling) on an industrial 3 Ah 21700 cell type under temperature-controlled conditions}

If any faults occur in the battery cell during the experiment, which lasts approximately 4–5 weeks, the test procedures are automatically terminated:

^{Cycle testing of nine (three per temperature) Samsung INR21700-40T, 4000 mAh cells; activation of the cell-internal circuit interrupter (‘CID activation’) due to excessive internal cell pressure at 60 °C}

In order to assess the condition of the electrode coatings and the safety status of the cells after 750 cycles, one cell per temperature is partially discharged and opened in a glovebox under an inert gas (argon) atmosphere (post-mortem analysis):

^{Opening and disassembling a 21700 cell under an inert gas atmosphere (left) and macroscopic inspection of the separator and electrode surfaces (right)}

CURRENT PROJECTS

• Research and service projects with corporate partners such as Einhell Germany AG and the DRÄXLMAIER Group.
• FestBatt – Cluster of competence for solid-state batteries

COMPLETED PROJECTS

OptiStore - Optimised energy storage systems for sustainable utilisation (European Union, ERDF)

The Autonomous Driving and Driver Assistance Systems Group, led by Prof. Thomas Limbrunner, conducts research into autonomous systems and driver assistance systems. The research group’s overall objective is to carry out applied research across the broad spectrum of autonomous systems.

The focus will be primarily on the following key areas:

• (Environmental) sensor technology
• Algorithms for object discrimination
• Object tracking
• Anomaly detection
• META data generation and analysis (including via artificial intelligence)
• Overall system architecture of autonomous systems

^{Model-scale test platform}

RESEARCH PROJECT

In terms of infrastructure, the research group relies on high-performance AI servers for algorithm development and simulation, on testbed environments for applications such as automotive Ethernet, and – as planned – on high-precision driving parameter measurement technology. This enables studies in the areas of driving function precision, type approval, as well as user experience (UX) and usability.

The research team’s work covers almost all areas of autonomous driving, as well as the further development of driver assistance systems.

Current work includes, amongst other things, in-vehicle big data analytics systems for the development of data-driven algorithms using intelligent edge nodes. In the INSTATE funded project, metadata is generated directly within the vehicle using intelligent edge devices. These are connected to the vehicle’s sensors. The metadata generated in this way can be used by a big data platform to understand the current scenario. Furthermore, data – including the metadata – is recorded only on an as-needed basis.

• Data-driven algorithms for autonomous driving using intelligent edge nodes
• Metadata generation directly in the vehicle
• Conversion of sensor data into compressed streams
• Back-end connection via a 5G gateway

^{The INSTATE project aims to use AI methods to explore new ways of collecting and processing sensor data}

Work on innovative verification concepts for the start-up capability of the complete vehicle has recently been completed as part of the iAATG project. As part of this project, research was carried out, amongst other things, into the detection of specific events arising from high functional and system complexity using artificial intelligence methods (single event analysis).  Furthermore, work was carried out on the verification of automated driving functions using inductive test strategies for ‘Vehicle Integrated Testing’ (Vitbox), as well as on the verification and validation of backend interaction relating to automated driving functions.

• Single-event analysis
• Vehicle-integrated testing
• Back-end interaction

^{The iAATG project is investigating innovative strategies for ensuring the safety of autonomous driving functions.}

STUDENT PROJECTS

A key aspect of the research group led by Professor Thomas Limbrunner is its collaboration with students on student projects and final-year dissertations. As part of these projects, a wide variety of sensor systems are commissioned and integrated, and the data is subsequently evaluated and analysed.

An important collaboration in this regard is the partnership between TC Plattling and the ‘Master of Applied Research’ degree programme.

^{Example of an IMU (inertial measurement unit)}

^{Example of a Master’s thesis: simulation-based data generation and analysis}

In addition to the analysis of real-world data, the research also focuses on the generation of simulation-based training data for image processing using artificial intelligence.

OVERVIEW OF EQUIPMENT

• GPU-powered Kubernetes cluster for AI development  
• Various workstations (additive manufacturing, electronics assemblies, lifting platforms, etc.) for the creation of prototype assemblies for research
• Automotive Ethernet testbed for stress testing and time synchronisation
• 5G campus network
• ADAS measurement technology with reference sensors
• Development and test equipment for vehicle bus communication
• Monitor HiL and ADAS simulation environment
• Various mobile autonomous platforms for sensor and functional development 
• GNSS – RTK reference station

CURRENT PROJECTS

DaDriVe - Data Driven Vehicle Validation by AI

INSTATE - In-vehicle big data analytics system for developing data-driven algorithms using intelligent edge nodes

COMPLETED PROJECTS

iAATG - Innovative safety concepts for ensuring the start-up capability of the complete vehicle; Press release

Project partners: BMW Group Dingolfing, b-plus

Borderland 5G

The Robo-CT research group led by Prof. Dr Simon Zabler is conducting research into the 3D digitisation of large objects, including entire vehicles, using a robot-based digitisation cell based on X-ray computed tomography.

• Multimodal non-destructive testing using optical measurement and X-ray technology
• Automated 2D & 3D X-ray inspection of large, industrially relevant objects
• Flexible three-dimensional positioning
• Collision-free, automated robotic movement
• Key research areas
• Computed tomography-based, collision-free trajectory optimisation
• Precise positioning and calibration of X-ray components
• Data completeness of scan trajectories
• Further application examples

EXAMPLES OF CURRENT CHALLENGES

• Optimisation of object placement to avoid inaccessible areas
• Determination of the degrees of freedom required for the robots’ movement

OVERVIEW OF EQUIPMENT

• Robots: 2 x KUKA KR 120 R2900, each fitted with a ‘KUKA Linear Unit KL 4000’ on the linear axes
• Heavy-duty table: WEISS – CR1000C
• X-ray source: Comet – XRS-225VF
• X-ray detector: Varex Imaging – PaxScan 4343DX-I
• Laser tracker: API – Radian
• 3D scanner: Photoneo – PhoXi 3D Scanner

^{Robot with an X-ray detector}

^{Robot with an X-ray source}

CURRENT PROJECTS

SmartCT

The SmartCT project develops and applies AI methods that enable robot-assisted computed tomography systems (robot-CT) to autonomously and non-destructively map the external and internal structures of any object. The data generated forms the basis for novel, innovative and data-driven business models in many sectors, such as product development (vehicle components, aircraft wings, battery cells, etc.).

^{X-ray image of an e-bike}