Publications at the Faculty of Computer Science and Automation since 2015

Results: 1907
Created on: Thu, 28 Mar 2024 23:11:04 +0100 in 0.0460 sec


Posielek, Tobias; Reger, Johann
Observability analysis for spacecraft attitude determination using a single temperature sensor. - In: 2021 European Control Conference (ECC), (2021), S. 1438-1445

We consider the problem of spacecraft attitude determination using temperature data. Common algorithms fuse multiple temperature measurements to reconstruct the attitude. However, a single sensor already contains a lot of information due to the temperature dynamics inherent to the nonlinear structure. In this work a rigorous observability analysis is carried out to determine the configurations in which the combination of a single temperature sensor with angular velocity measurements is sufficient for estimating the entire attitude. We evaluate the observability properties of the different configurations and give recommendations for the best configurations.



https://doi.org/10.23919/ECC54610.2021.9654904
Wulff, Kai; Honecker, Maria Christine; Reger, Johann
On the control design for the stabilisation of switched linear systems via eigenstructure assignment. - In: 2021 European Control Conference (ECC), (2021), S. 293-299

We are considering the control design problem for switched linear systems. We propose a method for the design of state-feedback controllers for the individual subsystems such that the closed-loop systems share a common eigenstructure. If additionally the eigenvalues of each individual subsystem can be chosen stable then the resulting switched system is stable for arbitrary switching. We present a necessary and a sufficient condition for which such controllers exist for systems of arbitrary order. For third-order systems, we show that a common eigenstructure can always be obtained by state-feedback given that the number of inputs offer enough degrees of freedom. We present a constructive procedure to obtain feedback controls such that the closed-loop systems have common eigenstructures. In all but one degenerated case the eigenvalues can be chosen arbitrarily such that the resulting closed-loop switched system is rendered asymptotically stable for arbitrary switching. We present an example for the degenerated case, where the eigenstructure may only be rectified if one of the closed-loop systems has a positive eigenvalue.



https://doi.org/10.23919/ECC54610.2021.9655006
Döring, Nicola; Mikhailova, Veronika; Brandenburg, Karlheinz; Broll, Wolfgang; Groß, Horst-Michael; Werner, Stephan; Raake, Alexander
Saying "Hi" to grandma in nine different ways : established and innovative communication media in the grandparent-grandchild relationship. - In: Technology, Mind, and Behavior, ISSN 2689-0208, (2021), insges. 1 S.

https://doi.org/10.1037/tms0000107
Walzer, Stefan;
Peeling close to the orientability threshold - spatial coupling in hashing-based data structures. - In: Proceedings of the Thirty-Second Annual ACM-SIAM Symposium on Discrete Algorithms, (2021), S. 2194-2211

https://dl.acm.org/doi/10.5555/3458064.3458195
Keßler, Jens;
Planungsmethoden für eine sozial akzeptable Navigation von Assistenzrobotern. - Ilmenau : Universitätsbibliothek, 2021. - 1 Online-Ressource (xiii, 195 Seiten)
Technische Universität Ilmenau, Dissertation 2021

In den vergangenen Jahren wurde im Bereich der mobilen Assistenzrobotik auch das Themenfeld der sozial-akzeptablen Navigation weiterentwickelt. Dabei kommt zu den vorhandenen Herausforderungen der Navigation nun auch der Faktor Mensch hinzu. Aus dem Themenbereich der sozial-akzeptablen Navigation widmet sich die vorliegende Arbeit zwei Aspekten, wobei der Fokus immer auf einem mobilen Roboter liegt, welcher sich im häuslichen Umfeld bewegt. Der erste Aspekt der Arbeit behandelt, wie ein Roboter sich in einer häuslichen Umgebung bewegen soll. Dabei ist von Interesse, welche Pfade der mobile Roboter im Beisein eines Bewohners plant. Die wissenschaftliche Leistung der Arbeit ist, vorhandene Planungsansätze auf Raum und Zeit zu erweitern und es so zu ermöglichen, die Bewegung einer Person in die Planungsphase zu integrieren. Dazu werden simple Bewegungsprädiktionsmethoden untersucht und es wird eine mathematische Beschreibung entwickelt, die Bewegungsvorhersagen von Personen in die Planung mit einbezieht. Durch die so weiterentwickelten Planungsverfahren werden zwei Szenarien experimentell näher untersucht: A) frontales Heranfahren an eine Person, B) frühzeitiges Ausweichen einer entgegenkommenden Person. Im zweiten Aspekt der vorliegenden Arbeit wird auf ein bisher nur sehr wenig beachtetes Problem der mobilen Robotik eingegangen: wie findet ein mobiler Roboter für seine jeweilige - häufig nur abstrakt formulierbare - Aufgabe sinnvolle Zielpunkte in seiner Einsatzumgebung, ohne dass diese statisch vorgegeben sein müssen? Als Lösungsansatz wird in dieser Arbeit ein Verfahren vorgeschlagen, welches eine abstrakte Aufgabe auf mehrere Kriterien abbildet und diese nach Extrempunkten untersucht. Diese Extrempunkte ergeben einzeln oder in Kombination mögliche Zielpunkte des Roboters. Die wissenschaftlichen Beiträge sind, für dieses Verfahren zu untersuchen, welche mathematische Formulierung der Einzelkriterien sinnvoll ist, welche Ergebnisse eine Optimierung mit unabhängigen Einzelkriterien liefert (Pareto-Optimalität) bzw. welche Ergebnisse die Kombination der einzelnen Kriterien zu einer Gesamtfunktion erzielt werden können (Superpositionsprinzip). Durch den hier präsentierten Ansatz werden folgende zwei Szenarien für die häusliche Navigation experimentell untersucht: C) Beobachten einer Person, D) Finden einer Parkposition bei potentiellen Engstellen. Für alle Szenarien gilt: es soll insbesondere das Weltwissen des Roboters zur Lösungsfindung genutzt werden. Dies alles setzt eine Akquise von Umweltwissen durch den Roboter voraus. Hierzu werden in der Arbeit praktisch einsetzbare Verfahren vorgestellt, welche das nötige Umweltwissen zur Schätzung der Oberkörperpose, Beobachtbarkeit und Bewegungsprädiktion ermitteln können.



https://doi.org/10.22032/dbt.50287
Comani, Silvia; Bertollo, Maurizio; Haueisen, Jens
Editorial: Dry electroencephalography for brain monitoring in sports and movement science. - In: Frontiers in neuroscience, ISSN 1662-453X, Bd. 15 (2021), 809227, S. 1-2

https://doi.org/10.3389/fnins.2021.809227
Kutschka, Hermann; Doeller, Christian F.; Haueisen, Jens; Maess, Burkhard
Magnetic field compensation coil design for magnetoencephalography. - In: Scientific reports, ISSN 2045-2322, Bd. 11 (2021), 22650, S. 1-12

While optically pumped magnetometers (OPMs) can be attached to the head of a person and allow for highly sensitive recordings of the human magnetoencephalogram (MEG), they are mostly limited to an operational range of approximately 5 nT. Consequently, even inside a magnetically shielded room (MSR), movements in the remnant magnetic field disable the OPMs. Active suppression of the remnant field utilizing compensation coils is therefore essential. We propose 8 compensation coils on 5 sides of a cube with a side length of approximately 2 m which were optimized for operation inside an MSR. Compared to previously built bi-planar compensation coils, the coils proposed in this report are more complex in geometry and achieved smaller errors for simulated compensation fields. The proposed coils will allow for larger head movements or smaller movement artifacts in future MEG experiments compared to existing coils.



https://doi.org/10.1038/s41598-021-01894-z
Blum, Maren-Christina; Leydolph, Lilly; Klee, Sascha
Influence of electric field orientation on the effect of ocular current stimulation using full field electroretinogram. - In: Current directions in biomedical engineering, ISSN 2364-5504, Bd. 7 (2021), 2, S. 167-170

Ocular current stimulation (CS) exhibits potential for the treatment of neurodegenerative ocular diseases. For a full field electroretinogram (ffERG) we found no CS effect on the characteristic waves (a-wave, b'-wave, and b-wave). To investigate whether the orientation of the generated electric field has an influence on the CS effect, this study repeated the previous ffERG study with changing one CS electrode position and compared the results of both studies. In the first study 15 (8 m, 27.5 ± 4.5 years) and in the second study 17 (7 m, 22.0 ± 1.9 years) healthy volunteers were stimulated with an anodal, cathodal, and sham direct CS of 800 [my]A for 5 min in three sessions (randomized, different days). For both studies, a cut-sized ring rubber electrode was placed around the eye. A square rubber electrode was placed for the first study at the ipsilateral temple and for the second study at the visual cortex. Before (ERG 1) and during (ERG 2) the CS, the ffERG was measured. For both studies, the difference between the ERG 1 and ERG 2 measurement (CS effect) for the three characteristic waves was analyzed and compared between the studies. For statistical analysis, the Mann-Whitney U test with Bonferroni correction was applied (α = 0.05). The comparison of the data distribution showed only slight differences between the studies. The Mann-Whitney U test found no significant difference of the CS effect between the studies for all amplitudes and CS groups (p ≥ 0.0055). In the mean, the latency differences were smaller than the time resolution, therefore no statements for latency effects were possible. It can be concluded that the retinal cells generating the ffERG are not affected by ocular CS in either electrode montages tested.



https://doi.org/10.1515/cdbme-2021-2043
Schramm, Stefan; Dietzel, Alexander; Blum, Maren-Christina; Link, Dietmar; Klee, Sascha
Technical light-field setup for 3D imaging of the human nerve head validated with an eye model. - In: Current directions in biomedical engineering, ISSN 2364-5504, Bd. 7 (2021), 2, S. 433-436

With the new technology of 3D light field (LF) imaging, fundus photography can be expanded to provide depth information. This increases the diagnostic possibilities and additionally improves image quality by digitally refocusing. To provide depth information in the human optic nerve head such as in glaucoma diagnostics, a mydriatic fundus camera was upgraded with an LF imager. The aim of the study presented here was the validation of the technical setup and resulting depth estimations with an appropriate eye model. The technical setup consisted of a mydriatic fundus camera (FF450, Carl Zeiss Meditec AG, Jena, Germany) and an LF imager (R12, Raytrix GmbH, Kiel, Germany). The field of view was set to 30˚. The eye model (24.65 mm total length) consisted of a two-lens optical system and interchangeable fundus models with papilla excavations from 0.2 to 1 mm in steps of 0.2 mm. They were coated with red acrylic lacquer and vessels were drawn with a thin brush. 15 images were taken for each papilla depth illuminated with green light (wavelength 520 nm ± 20 nm). Papilla depth was measured from the papilla ground to the surrounding flat region. All 15 measurements for each papilla depth were averaged and compared to the printed depth. It was possible to perform 3D fundus imaging in an eye model by means of a novel LF-based optical setup. All LF images could be digitally refocused subsequently. Depth estimation in the eye model was successfully performed over a 30˚ field of view. The measured virtual depth and the printed model papilla depth is linear correlated. The presented LF setup allowed high-quality 3D one-shot imaging and depth estimation of the optic nerve head in an eye model.



https://doi.org/10.1515/cdbme-2021-2110
Warsito, Indhika Fauzhan; Machts, René; Griebel, Stefan; Fiedler, Patrique; Haueisen, Jens
Influence of silver/silver chloride electroless plating on the Shore hardness of polyurethane substrates for dry EEG electrodes. - In: Current directions in biomedical engineering, ISSN 2364-5504, Bd. 7 (2021), 2, S. 9-12

Dry electrodes enable a shorter preparation time for infant EEG. Since infant skin is more sensitive than adult skin, soft electrodes are required to reduce the mechanical stress for this sensitive skin. Thus, soft electrodes are crucial for eventual repetitive and long-term use like in neonatal intensive care units. A biocompatible polyurethane (PU) can be produced in low hardness resulting in a soft and flexible electrode substrate. Silver/silver chloride (Ag/AgCl) electroless plating provides a conductive, electrochemically stable coating but the process may alter the mechanical properties of the electrode substrate. In this study, we assess the hardness of PU material before and after Ag/AgCl plating. The test sample design for Shore hardness measurement is based on ISO 7619-1:2010. Sample production consists of a 3D print master model, silicone molding, PU casting, and finally electroless plating. UPX 8400-1 (Sika AG, Switzerland) is used for the sample substrates. Test samples are produced with 7 different Shore hardness (range A40-A95) and 14 samples (each hardness: 1 uncoated and 1 coated). The hardness measurements are carried out with a lever-operated test stand Shore hardness tester model with a digital hardness tester (TI-AC with HDA 100-1, KERN & SOHN GmbH, Germany). It is shown that there is a hardness increase (Shore A) due to Ag/AgCl coating with a grand average of 1.1±0.7 (p<0.05). The largest increase of 2.1±0.2 is seen on the initial lowest Shore hardness sample (Shore hardness: 43.4±0.1). The absolute increase of hardness due to the Ag/AgCl coating decreases with increasing substrate hardness. It is concluded that there is no strong hardness increase of PU substrates due to Ag/AgCl plating. Therefore, the material is suitable as a soft electrode for repetitive and long-term use in infant applications.



https://doi.org/10.1515/cdbme-2021-2003