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Kreipe, Stefan; Helbig, Thomas; Witte, Hartmut; Schumann, Nikolaus; Anders, Christoph
Comparison of sEMG onset detection methods for occupational exoskeletons on extensive close-to-application data. - In: Bioengineering, ISSN 2306-5354, Bd. 11 (2024), 2, 119, S. 1-13

The design of human-machine interfaces of occupational exoskeletons is essential for their successful application, but at the same time demanding. In terms of information gain, biosensoric methods such as surface electromyography (sEMG) can help to achieve intuitive control of the device, for example by reduction of the inherent time latencies of a conventional, non-biosensoric, control scheme. To assess the reliability of sEMG onset detection under close to real-life circumstances, shoulder sEMG of 55 healthy test subjects was recorded during seated free arm lifting movements based on assembly tasks. Known algorithms for sEMG onset detection are reviewed and evaluated regarding application demands. A constant false alarm rate (CFAR) double-threshold detection algorithm was implemented and tested with different features. Feature selection was done by evaluation of signal-to-noise-ratio (SNR), onset sensitivity and precision, as well as timing error and deviation. Results of visual signal inspection by sEMG experts and kinematic signals were used as references. Overall, a CFAR algorithm with Teager-Kaiser-Energy-Operator (TKEO) as feature showed the best results with feature SNR = 14.48 dB, 91% sensitivity, 93% precision. In average, sEMG analysis hinted towards impending movements 215 ms before measurable kinematic changes.



https://doi.org/10.3390/bioengineering11020119
Andrada, Emanuel; Hildebrandt, Gregor; Witte, Hartmut; Fischer, Martin S.
Positioning of pivot points in quadrupedal locomotion: limbs global dynamics in four different dog breeds. - In: Frontiers in Bioengineering and Biotechnology, ISSN 2296-4185, Bd. 11 (2023), 1193177, S. 1-16

Dogs (Canis familiaris) prefer the walk at lower speeds and the more economical trot at speeds ranging from 0.5 Fr up to 3 Fr. Important works have helped to understand these gaits at the levels of the center of mass, joint mechanics, and muscular control. However, less is known about the global dynamics for limbs and if these are gait or breed-specific. For walk and trot, we analyzed dogs’ global dynamics, based on motion capture and single leg kinetic data, recorded from treadmill locomotion of French Bulldog (N = 4), Whippet (N = 5), Malinois (N = 4), and Beagle (N = 5). Dogs’ pelvic and thoracic axial leg functions combined compliance with leg lengthening. Thoracic limbs were stiffer than the pelvic limbs and absorbed energy in the scapulothoracic joint. Dogs’ ground reaction forces (GRF) formed two virtual pivot points (VPP) during walk and trot each. One emerged for the thoracic (fore) limbs (VPPTL) and is roughly located above and caudally to the scapulothoracic joint. The second is located roughly above and cranially to the hip joint (VPPPL). The positions of VPPs and the patterns of the limbs’ axial and tangential projections of the GRF were gaits but not always breeds-related. When they existed, breed-related changes were mainly exposed by the French Bulldog. During trot, positions of the VPPs tended to be closer to the hip joint or the scapulothoracic joint, and variability between and within breeds lessened compared to walk. In some dogs, VPPPL was located below the pelvis during trot. Further analyses revealed that leg length and not breed may better explain differences in the vertical position of VPPTL or the horizontal position of VPPPL. The vertical position of VPPPL was only influenced by gait, while the horizontal position of VPPTL was not breed or gait-related. Accordingly, torque profiles in the scapulothoracic joint were likely between breeds while hip torque profiles were size-related. In dogs, gait and leg length are likely the main VPPs positions’ predictors. Thus, variations of VPP positions may follow a reduction of limb work. Stability issues need to be addressed in further studies.



https://www.frontiersin.org/articles/10.3389/fbioe.2023.1193177
Lutherdt, Stefan; Maron, Mandy; Hertlein, Anna; Henze, Nicola
Ein Ansatz für digitales, kompetenzorientiertes Prüfen in den Ingenieurwissenschaften. - Graz : Forum Neue Medien in der Lehre Austria (fnma). - 1 Online-Ressource (Seite 22-24)Online-Ausgabe: fnma Magazin. - Graz : Forum Neue Medien in der Lehre Austria (fnma), ISSN 2410-5244, (2023), 2

In dem Artikel wird ein Ansatz zur Verbesserung und Implementierung digitaler, kompetenzorientierter Prüfungsformate in ingenieurswissenschaftlichen Bachelorstudiengängen vorgestellt. Dazu wird das mit diesem Ziel geförderte Projekt examING des Zentralinstituts für Bildung der TU Ilmenau vorgestellt und die drei Säulen des Projekts erläutert. Zur Erarbeitung und Überprüfung von Lösungsansätzen wurden in allen Fakultäten der Universität insgesamt neun Teilprojekte initiiert, von denen eines (im FG Biomechatronik) zur Ausbildung der Bachelor in der Mechatronik und Biomedizinischen Technik näher vorgestellt wird.



https://doi.org/10.22032/dbt.57632
Jäger, Max; Helbig, Thomas; Goos, Moritz; Köhring, Sebastian; Witte, Hartmut
Characterization of an antagonistic actuation system with nonlinear compliance for an upper-arm exoskeleton. - In: Actuators, ISSN 2076-0825, Bd. 12 (2023), 5, 196, S. 1-24

The parallel connection of technical and biological systems with a comparable mechanical behavior offers the possibility of reducing the interaction forces between those systems. Especially in the context of human-robot interaction (e.g., exoskeletons), it can improve user safety and acceptance at the same time. With this aim, we used antagonistic actuators with nonlinear compliance for a modular upper-extremity exoskeleton following biological paragons, mirroring the “blueprint” of its human user. In a test-bed setup, we compared antagonistic compliant actuation with antagonistic stiff, unilateral stiff and unilateral compliant actuation in the artificial “elbow joint” of the exoskeleton test bed. We show that this type of actuation allows the variation of the joint stiffness during motion, independent of the position. With the approach we propose, compliance leads to reduced force peaks and angular jerk, without sacrifices in terms of time constants and overshoot of amplitudes. We conclude that the presented actuation principle has considerable benefits in comparison to other types of exoskeleton actuation, even when using only commercially available and 3D printed components. Based on our work, further investigations into the control of compliant antagonistically actuated exoskeletons become realizable.



https://doi.org/10.3390/act12050196
David, Jonas Paul; Helbig, Thomas; Witte, Hartmut
SenGlove - a modular wearable device to measure kinematic parameters of the human hand. - In: Bioengineering, ISSN 2306-5354, Bd. 10 (2023), 3, 324, S. 1-29

For technical or medical applications, the knowledge of the exact kinematics of the human hand is key to utilizing its capability of handling and manipulating objects and communicating with other humans or machines. The optimal relationship between the number of measurement parameters, measurement accuracy, as well as complexity, usability and cost of the measuring systems is hard to find. Biomechanic assumptions, the concepts of a biomechatronic system and the mechatronic design process, as well as commercially available components, are used to develop a sensorized glove. The proposed wearable introduced in this paper can measure 14 of 15 angular values of a simplified hand model. Additionally, five contact pressure values at the fingertips and inertial data of the whole hand with six degrees of freedom are gathered. Due to the modular design and a hand size examination based on anthropometric parameters, the concept of the wearable is applicable to a large variety of hand sizes and adaptable to different use cases. Validations show a combined root-mean-square error of 0.99° to 2.38° for the measurement of all joint angles on one finger, surpassing the human perception threshold and the current state-of-the-art in science and technology for comparable systems.



https://doi.org/10.3390/bioengineering10030324
Witte, Hartmut;
The interplay of biomimetics and biomechatronics. - In: Biomimetics, ISSN 2313-7673, Bd. 7 (2022), 3, 96, S. 1-9

Biomechatronics is an engineering subject in which biomimetics as a method is one of its two supporting pillars: biology for engineering, or Bio4Eng. This is contrasted with biocompatible design, or Eng4Bio, examples of which are human-serving systems, such as exoskeletons, and biomedical engineering. The paper aims to illustrate that the research fields of biomimetics, biomechatronics, and biomedical engineering are not in competition but mutually supportive. The current attempts to place biomechatronics under the umbrella of biomimetics or biomedical engineering are therefore not expedient; they deprive the subject of its strength of combining Bio4Eng and Eng4Bio at any time in a task-related manner. In addition to research and development, however, the training of the specialists supporting the subjects must not be disregarded and is therefore described based on a proven design.



https://doi.org/10.3390/biomimetics7030096
Sartori, Julian; Köhring, Sebastian; Bruns, Stefan; Moosmann, Julian; Hammel, Jörg Ulrich
Gaining insight into the deformation of Achilles tendon entheses in mice. - In: Advanced engineering materials, ISSN 1527-2648, Bd. 23 (2021), 11, 2100085, S. 1-11

Understanding the biomechanics of tendon entheses is fundamental for surgical repair and tissue engineering but also relevant in biomimetics and paleontology. Examinations into the 3D tissue deformation under load are an important element in this process. However, entheses are difficult objects for microcomputed tomography due to extreme differences in X-ray attenuation. Herein, the ex vivo examination of Achilles tendon entheses from mice using a combination of tensile tests and synchrotron radiation-based microcomputed tomography is reported. Strains and volume changes are compared between the more proximal free tendon and the distal tendon that wraps around the Tuber calcanei. Tomographic datasets of relaxed and deformed entheses are recorded with propagation-based phase contrast. The tissue structure is rendered in sufficient detail to enable manual tracking of patterns along the tendon, as well as digital volume correlation in a suitable pair of tomographic datasets. The strains are higher in the distal than in the proximal tendon. These results support the existence of a compliant zone near the insertion. Necessary steps to extend the automatic tracking of tissue displacements to all stages of the deformation experiment are discussed.



https://doi.org/10.1002/adem.202100085
Döring, Tanja; Lutherdt, Stefan; Fritz, Jessica
Mensch-Maschine-Schnittstelle in der digitalen Fabrikhalle 2030 : DKE : Teil 5: "Umgang mit Unterschieden zwischen Kulturen, Milieus, Generationen, Bildungsniveaus, Überforderungsschwellen". - In: DIN-Mitteilungen + Elektronorm, ISSN 0722-2912, Bd. 99 (2020), 8, S. 35-38

Herrmann, Thomas; Lutherdt, Stefan; Fritz, Jessica
Mensch-Maschine-Schnittstelle in der digitalen Fabrikhalle 2030 : DKE : Teil 2: "Die Kooperation mehrerer Nutzer in unterschiedlichen Rollen beim Maschineneinsatz" (Zukunftszenario 1). - In: DIN-Mitteilungen + Elektronorm, ISSN 0722-2912, Bd. 99 (2020), 2, S. 10-14

Noubissi, André; Lutherdt, Stefan; Klippert, Jürgen
Mensch-Maschine-Schnittstelle in der digitalen Fabrikhalle 2030 : DKE : Teil 7: Szenario 7 "Die Maschine als Lernort" und Szenario 8 "Smartwatches im Fertigungsumfeld". - In: DIN-Mitteilungen + Elektronorm, ISSN 0722-2912, Bd. 99 (2020), 12, S. 20-24