@article{PrappacherBullmannBohnetal., author = {Prappacher, Nico and Bullmann, Markus and Bohn, Gunther and Deinzer, Frank and Linke, Andreas}, title = {Defect Detection on Rolling Element Surface Scans Using Neural Image Segmentation}, series = {Applied Sciences}, volume = {10}, journal = {Applied Sciences}, number = {9}, issn = {2076-3417}, doi = {10.3390/app10093290}, language = {en} } @inproceedings{BohnMoehringerKőroesietal., author = {Bohn, Gunther and M{\"o}hringer, Peter and Kőr{\"o}si, Adam and Mitesser, Oliver and Hovestadt, Thomas}, title = {Algorithms for flight path tracking of butterflies at inhomogeneous backgrounds}, series = {Papers of 33rd International Scientific Conference "Science in Practice"}, booktitle = {Papers of 33rd International Scientific Conference "Science in Practice"}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-2586}, pages = {50 -- 54}, abstract = {In this paper we describe the image processing algorithms for the tracking of the flight path of a single butterfly Polyommatus icarus in its natural surroundings. This tracking allows biologists to analyze the movement decision rules of the butterfly. Our butterfly video-screening and tracking system consists of a matrix of 6 stereo camera systems. The screening area is 4x3 meters. The tracking begins with a preprocessing algorithm, which is robust against the inhomogeneous background and optical distortions caused by the natural environment like moving shadows, change of illumination and color: The preprocessing algorithm works with grayscale images to eliminate the influence of the color changes. It adjusts the average intensity of consecutive images and calculates their difference image. So the influence of the inhomogeneous background and the shadows is greatly reduced. The reprocessing is followed by algorithms for thresholding, temporal tracking and calculation of the 3D-position using two corresponding images of the stereo camera systems. Results show, that the algorithms work robustly in spite of the inhomogeneous background and the optical distortions. The tracking algorithm generates the flight path of one butterfly in the screening area of one selected stereo camera system. A tracking of the butterfly movement is technically feasible over multiple stereo camera systems and so over large areas.}, language = {en} } @article{OeserHeinZiegleretal., author = {Oeser, David and Hein, Thiemo and Ziegler, Andreas and Seefried, Michael and Gielinger, Sebastian and Montesinos-Miracle, Daniel and Bohn, Gunther and Ackva, Ansgar}, title = {Age-related development of cell-to-cell variation under various operating conditions in commercial NMC/graphite lithium-ion cells}, series = {Journal of Energy Storage}, volume = {101}, journal = {Journal of Energy Storage}, publisher = {Elsevier}, doi = {10.1016/j.est.2024.113787}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-57585}, pages = {10}, abstract = {In real applications, lithium-ion cells are usually used in individual interconnections, with the worst cell determining capacity, performance and service life. Due to different ageing rates of the assembled cells, cell-to-cell variation changes over lifetime. In literature, cell-to-cell variation is usually investigated near room temperature under one operating condition. Data regarding cell-to-cell variation above and below room temperature under different operating conditions are hard to find. To fill the gap in literature, this study considers cell-to-cell variation as a function of different charge/discharge currents at ambient temperatures between 0 °C and 40 °C on commercial NMC/graphite cells (Samsung SDI ICR18650-26J). The results demonstrate that cell-to-cell variation strongly depends on the selected operating conditions. In particular, operating conditions near the lithium plating boundary at the beginning of the ageing process have a particularly high risk of developing a pronounced variation. Fast charging or charging at lower temperatures should therefore be avoided. Operation at moderate temperatures and currents, on the other hand, only leads to a slight increase in cell-to-cell variation in the tests carried out. A 24-month storage during the testing period at 30\% SOC and room temperature of the same cells shows even a slight reduction in cell-to-cell variation.}, language = {en} } @inproceedings{BohnTaubLinkeetal., author = {Bohn, Gunther and Taub, J. and Linke, Andreas and Bayer, Sven and Oeser, David and Ziegler, Andreas and Ettl, P. and Ackva, Ansgar}, title = {High-resolution Interferometric Measurement of Thickness Change on a Lithium-Ion Pouch Battery}, series = {3rd International Conference on Environmental and Energy Engineering (IC3E 2019)}, volume = {281}, booktitle = {3rd International Conference on Environmental and Energy Engineering (IC3E 2019)}, doi = {10.1088/1755-1315/281/1/012030}, pages = {8}, abstract = {Volume change of graphite leads to change in thickness of battery storage layers during discharging and charging. Pouch cell lithium ion batteries are used in the field of electric vehicles and solar home storage. This paper shows a measurement setup for the three-dimensional measurement of thickness change on a flat 6.7mm thick pouch cell using a white light interferometer. With a measuring field of 7.05mm diameter the resulting 3D thickness change record contains 226000 3D readings. The measuring points have a lateral distance of 13.1μm. The repeatability of the measurement is 312.8nm for the individual values and 64.1nm for the average value. In addition, this paper shows how the storage capacity of this pouch cell drops over 30 charge cycles.}, language = {en} } @article{BohnBayerStolzetal., author = {Bohn, Gunther and Bayer, Sven and Stolz, M. and Ackva, Ansgar and Arndt, Bernhard}, title = {Lifetime Simulation of Rechargeable Batteries for Solar Powered Fishing Lights}, series = {Applied mechanics and materials}, volume = {848}, journal = {Applied mechanics and materials}, issn = {1662-7482}, doi = {10.4028/www.scientific.net/AMM.848.115}, pages = {115 -- 118}, language = {en} } @article{GielingerHeinZiegleretal., author = {Gielinger, Sebastian and Hein, Thiemo and Ziegler, Andreas and Oeser, David and Breitfelder, Sebastian and Bohn, Gunther}, title = {A Short Time Expansion Measurement Method for the Detection of Aging Effect of Lithium Ion Cells Using a High Resolution Laser Interfometric Setup}, series = {IEEE Access}, volume = {11}, journal = {IEEE Access}, publisher = {IEEE}, doi = {10.1109/ACCESS.2023.3341505}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-53654}, pages = {11}, abstract = {In this work a new expansion measurement methodology for the detection of ageing mechanisms in lithium ion cells is described and evaluated. For this purpose, a polarization-optical homodyne Michelson interferometer with a resolution of approx. 10 nm was set up to allow measurements of different cell types, cell sizes, and cell chemistry within a Memmert IP55 climate chamber. The used interferometric measurement setup is ten times more accurate than measurement systems commonly used for battery measurements in the literature. The better spatial resolution of an interferometer setup enables the recording of the expansion response to short current pulses with low transferred charge. This offers the possibility to detect ageing mechanisms such as lithium plating within short measuring times. With this measurement setup, a lithium iron phosphate pouch cell from the company A123, with the model identification AMP20M1HD-A, is measured. First, an expansion measurement over a full charge and discharge cycle with a constant load of ± C 20 (b=1 A) is performed. Here, the cell undergoes an expansion of about 42 μm. Subsequently, the in this work proposed measurement methodology is presented to show the influence of effects such as the formation of overshooting graphite stages or lithium plating on cell expansion. For this purpose, at a residual capacitance of 50\%, the cell is pulsed with current of different intensity I ∈ {±20A,±80A} for t = {240 s, 60 s}, at T = {10 ◦C, 20 ◦C, 30 ◦C}, respectively, and the mechanical response is recorded using the high accuracy interferometer setup. A mechanical relaxation of the cell after the pulses with a time constant in the range between 10 s and 20 s can be observed. It is shown that this relaxation behavior can be associated with effects of the anode known from the literature, such as the formation of overshooting graphite stages or lithium plating. These effects can be recorded by the very high-resolution measurement already with little transferred charge and within a short measurement time.}, language = {en} } @article{GielingerBohnDeinzeretal., author = {Gielinger, Sebastian and Bohn, Gunther and Deinzer, Frank and Linke, Andreas}, title = {Investigation of an inline inspection method for the examination of cylinder-like specular surfaces using deflectometry}, series = {applied sciences}, volume = {12}, journal = {applied sciences}, number = {13}, issn = {2076-3417}, abstract = {An optical measuring method is presented, with which it is possible to measure and evaluate reflective cylindrical surfaces using a combination of deflectometry and subsequent reconstruction of the surface. The system is set up and tested on rolling elements of cylindrical roller bearings. However, it is not limited to this use case and can be applied to other cylindrical specular surfaces. The system distinguishes itself from existing test methods through the combination of high-resolution three-dimensional defect measurement with a very short recording time, and offers the possibility of introducing tolerance limits in the production of cylindrical specular surfaces. With this method, it is possible to record a defect with the dimensions of 1.3 mm by 1.8 mm within 5 s and to reconstruct the absolute depth. The resolution of the system is below 10 μm in both X- and Y-direction, and is therefore sufficiently accurate to detect typical surface defects such as scratches, dents, or deformations. To validate the measured values of the system, the results of an artificially generated 10.35 μm deep defect location were compared with those of a highly accurate mechanical stylus measurement.}, language = {en} }