Universität Stuttgart
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Item Open Access Enzyme-assisted circular additive manufacturing as an enabling technology for a circular bioeconomy : a conceptual review(2024) Protte-Freitag, Kristin; Gotzig, Sophia; Rothe, Hannah; Schwarz, Oliver; Silber, Nadine; Miehe, RobertAdditive manufacturing (AM) is a decisive element in the sustainable transformation of technologies. And yet its inherent potential has not been fully utilized. In particular, the use of biological materials represents a comparatively new dimension that is still in the early stages of deployment. In order to be considered sustainable and contribute to the circular economy, various challenges need to be overcome. Here, the literature focusing on sustainable, circular approaches is reviewed. It appears that existing processes are not yet capable of being used as circular economy technologies as they are neither able to process residual and waste materials, nor are the produced products easily biodegradable. Enzymatic approaches, however, appear promising. Based on this, a novel concept called enzyme-assisted circular additive manufacturing was developed. Various process combinations using enzymes along the process chain, starting with the preparation of side streams, through the functionalization of biopolymers to the actual printing process and post-processing, are outlined. Future aspects are discussed, stressing the necessity for AM processes to minimize or avoid the use of chemicals such as solvents or binding agents, the need to save energy through lower process temperatures and thereby reduce CO2 consumption, and the necessity for complete biodegradability of the materials used.Item Open Access Selbsteinstellende Regelung von Schwungmassenspeichersystemen in industriellen Gleichspannungszwischenkreisen(Stuttgart : Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA, 2024) Laribi, Raoul; Sauer, Alexander (Univ.-Prof. Dr.-Ing. Dipl.-Kfm.)Der industrielle Energieeinsatz ist zum Großteil auf motorische Verbraucher zurückzuführen. Die elektrische Leistung für die dynamischen Beschleunigungs- und Bremsvorgänge von Industriemaschinen müssen durch Gleichrichter vorgehalten werden, auch wenn die maximalen Leistungen nur kurzzeitig auftreten. Dies führt zu überdimensionierten Anschlussleistungen und dementsprechenden Kosten für die elektrische Versorgung. Schwungmassenspeichersysteme können dazu eingesetzt werden, die Spitzenleistungen einer Industriemaschine aus Netzsicht zu reduzieren, Bremsenergie aufzunehmen und zusätzliche Erzeugungskapazität für neuinstallierte Prozesse bereitzustellen. Die Nachrüstung eines Schwungmassenspeichersystems in einer Industriemaschine ist ein komplexer Inbetriebnahmevorgang, der mithilfe der vorliegenden Arbeit vereinfacht wird. In der Arbeit wird ein Software-Artefakt für eine selbsteinstellende Regelung von Schwungmassenspeichersystemen in industriellen Gleichspannungszwischenkreisen entwickelt. Es ermöglicht die virtuelle Inbetriebnahme eines nachgerüsteten Schwungmassenspeichersystems, bevor die Hardware des Speichersystems integriert wird. Darüber hinaus werden die relativen Potenziale der Leistungsreduktion und Nutzung von Bremsenergie simulativ bestimmt und bewertet. Das Software-Artefakt der selbsteinstellenden Regelung setzt sich aus vier Funktionsmodulen zusammen. Dazu gehören die Lastprofilerkennung, die Systemidentifikation des Frequenzumrichters der Industriemaschine, der Reglerentwurf und die Speicherregelung. Die selbsteinstellende Regelung wurde in zwei Fallbeispielen für die Lastprofile einer Werkzeugmaschine und einer Holzbearbeitungsmaschine erfolgreich validiert.Item Open Access Online motion planning for dual arm industrial robots(Stuttgart : Fraunhofer Verlag, 2020) Beuke, Felix; Verl, Alexander (Prof. Dr.-Ing. Dr. h.c. mult.)The trend toward consumer products of ever-increasing individuality poses several challenges for the domain of manufacturing automation. One of these challenges relates to the flexibility of devices used in industrial automation. In classical low-variability and high-throughput automation, plants could be designed and financed with several years of constant uptime in mind. In contrast, automated manufacturing of more and more individualized goods requires adapted manufacturing processes with shorter cycles and more flexible automation equipment. The higher variability and shorter life-cycle of manufactured goods often entails an uncertainty that makes investment in highly-specialized but inflexible automation equipment unprofitable. This creates a growing need for more flexible equipment that can be reused when the produced goods or parts of the production process change. Against this backdrop, the field of collaborative robotics has received increased interest and development activity over the past years. These robots can work in close proximity to humans and do not need to be fenced off in dedicated safety areas, thus enabling a more flexible use of the equipment. The idea of flexibility is taken further in this context by the development of dual-arm robots that mimic the morphology of the human upper body with two arms mounted on one common body. While these devices potentially offer increased flexibility and can work on a set of tasks otherwise reserved for humans (e.g., dual-arm handling, parallel work with both arms) the close proximity of the arms brings about new problems in the application of these robots. Using available programming methods for creating collision-free and coordinated motions for dual-arm robots is often complex and leads to long application times, which takes away a considerable part of the added flexibility introduced by dual-arm robots. To enable users to leverage the potential flexibility of industrial dual-arm robots more easily, this work develops a coordinated motion planner and associated control infrastructure for dual-arm industrial robots. Together, these components relieve the programmer of the responsibility to prevent arm collisions by specifying an exact temporal synchronization for both arms. Instead, collision-free and coordinated motions are automatically planned and executed based on a geometrical model. Moreover, it can serve as an application basis for more high-level planners for dual-arm industrial robots. The proposed planner and control architecture are implemented and evaluated on a real dual-arm robot.Item Open Access Optimization of disassembly strategies for electric vehicle batteries(2021) Baazouzi, Sabri; Rist, Felix Paul; Weeber, Max; Birke, Kai PeterVarious studies show that electrification, integrated into a circular economy, is crucial to reach sustainable mobility solutions. In this context, the circular use of electric vehicle batteries (EVBs) is particularly relevant because of the resource intensity during manufacturing. After reaching the end-of-life phase, EVBs can be subjected to various circular economy strategies, all of which require the previous disassembly. Today, disassembly is carried out manually and represents a bottleneck process. At the same time, extremely high return volumes have been forecast for the next few years, and manual disassembly is associated with safety risks. That is why automated disassembly is identified as being a key enabler of highly efficient circularity. However, several challenges need to be addressed to ensure secure, economic, and ecological disassembly processes. One of these is ensuring that optimal disassembly strategies are determined, considering the uncertainties during disassembly. This paper introduces our design for an adaptive disassembly planner with an integrated disassembly strategy optimizer. Furthermore, we present our optimization method for obtaining optimal disassembly strategies as a combination of three decisions: (1) the optimal disassembly sequence, (2) the optimal disassembly depth, and (3) the optimal circular economy strategy at the component level. Finally, we apply the proposed method to derive optimal disassembly strategies for one selected battery system for two condition scenarios. The results show that the optimization of disassembly strategies must also be used as a tool in the design phase of battery systems to boost the disassembly automation and thus contribute to achieving profitable circular economy solutions for EVBs.Item Open Access Comparison of the temperature, radiation, and heat flux distribution of a hydrogen and a methane flame in a crucible furnace using numerical simulation(2024) Mages, Alexander; Sauer, AlexanderSustainable technologies to replace current fossil solutions are essential to meet future CO2 emission reduction targets. Therefore, this paper compares key performance indicators of a hydrogen- and a methane-flame-fired crucible furnace with computational fluid dynamics simulations at identical firing powers, aiming to fully decarbonize the process. Validated numerical models from the literature were used to compare temperatures, radiation fields, radiation parameters and heat transfer characteristics. As a result, we observed higher combustion temperatures and a 19.0% higher fuel utilization rate in the hydrogen case, indicating more efficient operating modes, which could be related to the increased radiant heat flux and temperature ranges above 1750 K. Furthermore, higher scattering of the heat flux distribution on the crucible surface could be determined indicating more uneven melt bath temperatures. Further research could focus on quantifying the total fuel consumption required for the heating up of the furnace, for which a transient numerical model could be developed.Item Open Access Multi-method model for the investigation of disassembly scenarios for electric vehicle batteries(2023) Baazouzi, Sabri; Grimm, Julian; Birke, Kai PeterDisassembly is a pivotal technology to enable the circularity of electric vehicle batteries through the application of circular economy strategies to extend the life cycle of battery components through solutions such as remanufacturng, repurposing, and efficient recycling, ultimately reintegrating gained materials into the production of new battery systems. This paper aims to develop a multi-method self-configuring simulation model to investigate disassembly scenarios, taking into account battery design as well as the configuration and layout of the disassembly station. We demonstrate the developed model in a case study using a Mercedes-Benz battery and the automated disassembly station of the DeMoBat project at Fraunhofer IPA. Furthermore, we introduce two disassembly scenarios: component-oriented and accessibility-oriented disassembly. These scenarios are compared using the simulation model to determine several indicators, including the frequency of tool change, the number and distribution of robot routes, tool utilization, and disassembly time.Item Open Access Model-based biomechanical exoskeleton concept optimization for a representative lifting task in logistics(2022) Schiebl, Jonas; Tröster, Mark; Idoudi, Wiem; Gneiting, Elena; Spies, Leon; Maufroy, Christophe; Schneider, Urs; Bauernhansl, ThomasOccupational exoskeletons are a promising solution to prevent work-related musculoskeletal disorders (WMSDs). However, there are no established systems that support heavy lifting to shoulder height. Thus, this work presents a model-based analysis of heavy lifting activities and subsequent exoskeleton concept optimization. Six motion sequences were captured in the laboratory for three subjects and analyzed in multibody simulations with respect to muscle activities (MAs) and joint forces (JFs). The most strenuous sequence was selected and utilized in further simulations of a human model connected to 32 exoskeleton concept variants. Six simulated concepts were compared concerning occurring JFs and MAs as well as interaction loads in the exoskeleton arm interfaces. Symmetric uplifting of a 21 kg box from hip to shoulder height was identified as the most strenuous motion sequence with highly loaded arms, shoulders, and back. Six concept variants reduced mean JFs (spine: >70%, glenohumeral joint: >69%) and MAs (back: >63%, shoulder: >59% in five concepts). Parasitic loads in the arm bracing varied strongly among variants. An exoskeleton design was identified that effectively supports heavy lifting, combining high musculoskeletal relief and low parasitic loads. The applied workflow can help developers in the optimization of exoskeletons.Item Open Access Gestaltung eines auf dem föderierten Lernen basierenden Systems zur energetischen Anomalieerkennung in Produktionsprozessen(Stuttgart : Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA, 2025) Kaymakci, Can; Sauer, Alexander (Prof. Dr.-Ing. Dipl.-Kfm.)Um die nationalen Effizienzziele zu erreichen, ist es unerlässlich, Energie und Material einzusparen. Die frühzeitige Erkennung von energetischen Anomalien in Produktionsprozessen kann hier mit Modellen aus dem Bereich des maschinellen Lernens erfolgen. Für das Training der Modelle werden von Anwendern von Maschinen und Anlagen innerhalb der Produktionsprozesse erfasste Daten benötigt, die viele Anwender in der Praxis nicht freigeben. Daher ist ein umfassendes Training und ein erfolgreiches Erkennen von Unregelmäßigkeiten aus der Perspektive des Maschinen- und Anlagenbauers nicht möglich. Diese Arbeit zielt darauf ab, ein auf dem föderierten Lernen basierendes System zur Erkennung von energetischen Anomalien in Produktionsprozessen zu entwickeln. Dieses System soll Produktionsunternehmen in die Lage versetzen energetische Anomalien zu erkennen, ohne dabei sensible Maschinen- und Betriebsdaten weiterzugeben. Daher adressiert diese Arbeit die Forschungsfrage, wie ein auf dem föderierten Lernen basierendes System zur energetischen Anomalieerkennung in Produktionsprozessen ausgelegt werden kann. Hierzu wird eine Architektur und eine Methode entwickelt, die sowohl die Identifikation der Datenverarbeitung, die Modellarchitektur als auch die Optimierung der Konfigurationsparameter des Systems umfasst. Die in der Arbeit definierten funktionalen Komponenten der Architektur können mit der Methode hergeleitet und instanziiert werden. Der vorgestellte Ansatz wird anhand zweier Anwendungsfälle validiert. Der erste Anwendungsfall befasst sich mit der Erkennung von Bedienfehlern beim Lichtbogenschweißen. Der zweite Anwendungsfall konzentriert sich auf die Erkennung von Druckluftleckagen, welche erhebliche Energieverluste verursachen können. In beiden Anwendungsfällen zeigt sich, dass eine Nutzung des auf dem föderierten Lernen basierenden Systems zur energetischen Anomalieerkennung eine Erkennung von Unregelmäßigkeiten in Produktionsprozessen ermöglicht, ohne dass sensible Maschinen- und Betriebsdaten zentral gespeichert werden.Item Open Access Design of fiber-composite/metal-hybrid structures made by multi-stage coreless filament winding(2022) Mindermann, Pascal; Müllner, Ralf; Dieringer, Erik; Ocker, Christof; Klink, René; Merkel, Markus; Gresser, Götz T.The methods presented in this study assist in fabricating load-bearing structures with high mass-specific mechanical performance at various scales. Possible applications include primary and secondary structures in engineering, architecture, automotive, or aerospace industries.Additive manufacturing processes, such as coreless filament winding with fiber composites or laser powder bed fusion with metals, can produce lightweight structures while exhibiting process-specific characteristics. Those features must be accounted for to successfully combine multiple processes and materials. This hybrid approach can merge the different benefits to realize mass savings in load-bearing structures with high mass-specific stiffnesses, strict geometrical tolerances, and machinability. In this study, a digital tool for coreless filament winding was developed to support all project phases by natively capturing the process-specific characteristics. As a demonstration, an aluminum base plate was stiffened by a coreless wound fiber-composite structure, which was attached by additively manufactured metallic winding pins. The geometrical deviations and surface roughness of the pins were investigated to describe the interface. The concept of multi-stage winding was introduced to reduce fiber–fiber interaction. The demonstration example exhibited an increase in mass-specific component stiffness by a factor of 2.5 with only 1/5 of the mass of a state-of-the-art reference. The hybrid design approach holds great potential to increase performance if process-specific features, interfaces, material interaction, and processes interdependencies are aligned during the digitized design phase.Item Open Access Methodik zur automatisierten Generierung einer best-practice-basierten Ablaufplanung manueller Montagesysteme(Stuttgart : Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA, 2024) Kärcher, Susann; Bauernhansl, Thomas (Prof. Dr.-Ing.)In manuellen Montagesystemen ist die Variantenvielfalt oft hoch, die Stückzahlen sind gering und sie unterliegen häufigen Änderungen. Klassische Methoden der Montageplanung sind bei diesen Herausforderungen oft zu aufwändig. Dies führt dazu, dass Montagesysteme häufig eine unzureichende Planungstiefe und noch großes Optimierungspotential haben. In der vorliegenden Arbeit wurde eine Methodik entwickelt, die automatisiert eine Montageablaufplanung generiert. Sie überträgt den Grundgedanken des Benchmarkings - von anderen Best Practices zu lernen - auf die manuelle Montage. Auf Basis von Ist-Daten aus der Montage vergleicht die Methodik unterschiedliche Montageabläufe eines Produktes und generiert daraus den besten Montageablauf. Weiter werden unter Einbeziehung der Leistungsgrade und Arbeitsplatzfaktoren Vorgabezeiten generiert. Die Methodik ist an ein Benchmarking-Vorgehensmodell angelehnt und in vier Schritte gegliedert: die Planung, die Datenerhebung, die Datenanalyse und das Vornehmen von Verbesserungen. Die Vorteile der Methodik liegen in der automatisierten Montageablaufplanung in manuellen Montagesystemen. Sie erhöht so die Produktivität in manuellen Montagesystemen und reduziert den Planungsaufwand. Das generische Modell erlaubt eine Anwendung der Methodik in unterschiedlichen manuellen Montagesystemen.