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Role of compliant mechanics and motor control in hopping - from human to robot
No full textCompliant leg function found during bouncy gaits in humans and animals can be considered a role model for designing and controlling bioinspired robots and assistive devices. The human musculoskeletal design and control differ from distal to proximal joints in the leg. The specific mechanical properties of different leg parts could simplify motor control, e.g., by taking advantage of passive body dynamics. This control embodiment is complemented by neural reflex circuitries shaping human motor control. This study investigates the contribution of specific passive and active properties at different leg joint levels in human hopping at different hopping frequencies. We analyze the kinematics and kinetics of human leg joints to design and control a bioinspired hopping robot. In addition, this robot is used as a test rig to validate the identified concepts from human hopping. We found that the more distal the joint, the higher the possibility of benefit from passive compliant leg structures. A passive elastic element nicely describes the ankle joint function. In contrast, a more significant contribution to energy management using an active element (e.g., by feedback control) is predicted for the knee and hip joints. The ankle and knee joints are the key contributors to adjusting hopping frequency. Humans can speed up hopping by increasing ankle stiffness and tuning corresponding knee control parameters. We found that the force-modulated compliance (FMC) as an abstract reflex-based control beside a fixed spring can predict human knee torque-angle patterns at different frequencies. These developed bioinspired models for ankle and knee joints were applied to design and control the EPA-hopper-II robot. The experimental results support our biomechanical findings while indicating potential robot improvements. Based on the proposed model and the robot’s experimental results, passive compliant elements (e.g. tendons) have a larger capacity to contribute to the distal joint function compared to proximal joints. With the use of more compliant elements in the distal joint, a larger contribution to managing energy changes is observed in the upper joints
Towards a spatially resolved, single-ended TDLAS system for characterizing the distribution of gaseous species
No full textMany applications require diagnostics that can quantify the distribution of chemical gas species and gas temperature along a single line-of-sight, which is challenging in process environments with limited optical access. To this end, we present an approach that combines time-of-flight Light Detection and Ranging (LiDAR) with Tunable Diode Laser Absorption Spectroscopy (TDLAS) to scan individual gas molecular transition lines. This method is applicable in situations where scattering objects are distributed along the beam path, such as solid fuel combustion, or when dealing with multiple gas volumes separated by weakly reflecting windows. The approach is demonstrated through simulation studies and an initial experimental proof of concept for separated gas volumes
Point cloud quality metrics for incremental image-based 3D reconstruction
No full textImage-based 3D reconstruction is a powerful method for accurately reconstructing an object’s geometry and texture from images. A crucial factor for the accuracy and completeness of the resulting reconstructed model is the choice of poses for capturing images, which is called view planning. One possible view planning strategy uses an iterative feedback loop that switches between planning poses and an incremental reconstruction to autonomously digitize an object without prior knowledge. However, this approach requires identifying which parts of an object are “poorly reconstructed” and thus would benefit from being part of additional images. This work explores the use of point cloud quality metrics to provide this feedback by comprehensively comparing a set of existing and newly introduced metrics in terms of their time-dependent behavior, similarity, and their applicability to view planning. Among the newly proposed metrics this work introduces the Reconstruction Quality Feedback (RQF) , which shows a significantly improved performance in simulations when being used for view planning. The effectiveness of RQF is also demonstrated for real objects on an autonomous robotic 3D digitization system
Eine wegweisende Berufung - 50-Jahr-Feier des Instituts für Geschichte
No full textDie Gründung und Entwicklung des Instituts für Geschichte sind eng verknüpft mit dem renommierten Wissenschaftler Karl Otmar Freiherr von Aretin
Vor 100 Jahren – „Kleine“ Hüpfer mit großer Wirkung
No full textDas Jahr 1912 bewies eindrucksvoll: Darmstadt war eine Wiege der deutschen Luftfahrt.
Das Flugzeug steckte noch in den Kinderschuhen, entwickelte sich aber rasant. Der Flugpionier August Euler baute seit 1909 auf dem Griesheimer Sand eigene Gleit- und Motorflugzeuge. In Darmstadt begannen im selben Jahr fünf befreundete Schüler, in der Flug-Sport-Vereinigung (FSV) ebenfalls Segelflugzeuge zu bauen
Pionierin ohne Sogwirkung. Vor 100 Jahren schloss an der TH Darmstadt erstmals eine Frau ihr Studium mit Ingenieur-Titel ab
No full textAm 18. Juli 1913 verlieh die Technische Hochschule Darmstadt zum ersten Mal den Titel Diplomingenieur an eine Frau. Von einer damaligen Zeitung wurde sie als „Fräulein Ingenieur“ und die erste Dame bezeichnet, die in Deutschland diesen Titel erhalten habe. Der Bezeichnung Ingenieurin war 14 Jahre nach der Einführung des Dipl.-Ing. wohl noch zu ungewöhnlich, um Jovanka Bontschits auch so zu nennen
A tunable transition metal dichalcogenide entangled photon-pair source
No full textEntangled photon-pair sources are at the core of quantum applications like quantum key distribution, sensing, and imaging. Operation in space-limited and adverse environments such as in satellite-based and mobile communication requires robust entanglement sources with minimal size and weight requirements. Here, we meet this challenge by realizing a cubic micrometer scale entangled photon-pair source in a 3R-stacked transition metal dichalcogenide crystal. Its crystal symmetry enables the generation of polarization-entangled Bell states without additional components and provides tunability by simple control of the pump polarization. Remarkably, generation rate and state tuning are decoupled, leading to equal generation efficiency and no loss of entanglement. Combining transition metal dichalcogenides with monolithic cavities and integrated photonic circuitry or using quasi-phasematching opens the gate towards ultrasmall and scalable quantum devices
Kershaw, Ian: Der Mensch und die Macht. Über Erbauer und Zerstörer Europas im 20. Jahrhundert, übers. v. Klaus-Dieter Schmidt, 592 S., DVA, München 2022.
No full textDie deutsche Geschichtswissenschaft tut sich mit Biografien schwer – auch das ist ein Erbe der seit den 1950er Jahren erfolgten Abkehr von der Tradition. Lebensbeschreibungen sind zwar auch hierzulande oft Verkaufserfolge, aber innerhalb der Zunft verdient man sich damit im Regelfall keine Meriten. Besser gesagt: Man hat sie zumeist schon, wenn man in einer oft späten Phase seines Forscherlebens dieses Genre bedient. In den angelsächsischen Ländern, zumal in Großbritannien, ist das ganz anders. Dort wird das Publikum auch regelmäßig zur Abstimmung über die ‚größte‘ Persönlichkeit der britischen Geschichte, über „100 Greatest Britons“ (so die BBC 2002) gebeten. In Deutschland dagegen teilte das Nachschlagewerk „Die großen Deutschen“ nicht nur das Schicksal aller gedruckten Nachschlagewerke und verschwand vom Markt, sondern dokumentierte unfreiwillig auch noch den Konstruktionscharakter dieser Kategorie: In der ersten, von Willy Andreas herausgegebenen Auflage fehlte 1936 in Band 4 Gustav Stresemann als verhasster „Erfüllungspolitiker“, während Theodor Heuss dafür sorgte, dass Stresemann in der von ihm mitverantworteten Neuauflage 1957 als ewig „finassierender“ Machtpolitiker wieder nicht aufgenommen wurde
Sustainable Urban Governance and the Digital Divide: Patterns of E-Participation in Istanbul
No full textDigital transformation in public service delivery holds the potential to foster sustainable urban governance by promoting transparency, inclusivity, and citizen engagement. However, unequal access to digital tools and competencies poses challenges to the equitable use of these services. This study examines how different dimensions of the digital divide—socio-demographic characteristics, digital literacy, physical access to technology, and the perceived necessity of the internet—influence citizen engagement with digital public services in Istanbul. Drawing on secondary data from the Istanbul Metropolitan Municipality, a three-step methodology is employed combining logistic regression, thematic analysis, and spatial comparison. The results indicate that factors such as education, gender, age, and perceived necessity significantly affect digital engagement. Notably, digital literacy does not consistently predict e-government service use, suggesting that necessity may override competence. The study also finds that engagement remains limited to passive information-seeking rather than participatory functions. These findings highlight the importance of addressing digital inequalities to promote more inclusive service access. Ultimately, the study contributes to the understanding of how digital inclusion can advance sustainable urban governance and emphasizes the need for policies that ensure digital platforms benefit all segments of the population
