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We present a compact battery charger topology for weight and cost sensitive applications with an average output current of 9A targeted for 36V batteries commonly found in electric bicycles. Instead of using a conventional boost converter with large DC-link capacitors, we accomplish PFC-functionality by shaping the charging current into a sin²-shape. In addition, a novel control scheme without input-current sensing is introduced. A-priori knowledge is used to implement a feed-forward control in combination with a closed-loop output current control to maintain the target current. The use of a full-bridge/half bridge LLC converter enables operation in a wide input-voltage range.
A fully featured prototype has been built with a peak output power of 1050W. An average output power of 400W was measured, resulting in a power density of 1.8 kW/dm³. At 9A charging current, a power factor of 0.96 was measured and the efficiency exceeds 93% on average with passive rectification.
The impact of pulse charging has been evaluated on a 400Wh battery which was charged with the proposed converter as well as CC-CV-charging for reference. Both charging schemes show similar battery surface temperatures.
Der vorliegende Beitrag zeigte die Anwendung eines Extended Kalman Filters für die Beurteilung des Verschleißzustandes von Rollenketten. Anders als in den üblicherweise eingesetzten signalbasierten Verfahren wurde damit ein modellbasierter Ansatz gewählt. Der Einsatz des Extended Kalman Filters ermöglicht die Schätzung von Parametern eines reduzierten Kettenmodells, das die Dynamik der einzigen Messgröße, nämlich des Drehmoments des antreibenden Motors näherungsweise nachbildet. Im Beitrag wurde dieses Verfahren auf Messdaten aus vier Dauerversuchen an Rollenketten eingesetzt und gezeigt, dass mit steigendem Verschleiß eine Änderung ausgewählter Modellparameter erfolgt.
Diese Vorgehensweise ist ein erster Ansatz, der durch weitere Forschungsarbeiten noch verbessert werden muss. In zukünftigen Forschungsarbeiten wird zusätzlich zur Parameterschätzung eine Prädiktion durchgeführt, um einen Schätzwert für die Restlebensdauer zu erhalten. Hierzu gibt es Ansätze in der Literatur, die auf das konkrete Problem angepasst werden müssen. Zudem muss die Modellierungssystematik so erweitert werden, dass Wissen über das Prozessverhalten in die Modellierung mit eingebracht wird, um die Aussagekraft der Ergebnisse sowie die Robustheit des Verfahrens bezüglich Betriebsparametern, Umgebungsbedingungen und Exemplarstreuungen zu verbessern.
The aim of this work was to investigate the mean fill weight control of a continuous capsule-filling process, whether it is possible to derive controller settings from an appendant process model. To that end, a system composed out of fully automated capsule filler and an online gravimetric scale was used to control the filled weight. This setup allows to examine challenges associated with continuous manufacturing processes, such as variations in the amount of active pharmaceutical ingredient (API) in the mixture due to fluctuations of the feeders or due to altered excipient batch qualities. Two types of controllers were investigated: a feedback control and a combination of feedback and feedforward control. Although both of those are common in the industry, determining the optimal parameter settings remains an issue. In this study, we developed a method to derive the control parameters based on process models in order to obtain optimal control for each filled product. Determined via rapid automated process development (RAPD), this method is an effective and fast way of determining control parameters. The method allowed us to optimize the weight control for three pharmaceutical excipients. By conducting experiments, we verified the feasibility of the proposed method and studied the dynamics of the controlled system. Our work provides important basic data on how capsule filler can be implemented into continuous manufacturing systems.
Frost reduction in mechanical balanced ventilation by efficient means of preheating cold supply air
(2019)
This study has focused on evaluating the financial potential of wastewater and geothermal heat recovery systems in a multi-family building. The recovered heat was used to improve the performance of mechanical ventilation with heat recovery (MVHR) system during the coldest days in central Sweden. The main issue, which was targeted with these solutions, was to reduce frost formation in the system and hence increase its thermal efficiency. By looking at the life cycle cost over a lifespan of 20 years, the observed systems were being evaluated economically. Furthermore, statistical analyses were carried-out to counter the uncertainty that comes with the calculation. It was found that the studied wastewater systems have a high possibility of generating savings in this period, while the one fed by geothermal energy is less likely to compensate for its high initial cost. All designed systems however, managed to reduce operational cost by 35-45% due to lower energy usage.
We propose a method for recognizing dynamic gestures using a 3D sensor. New aspects of the developed system include problem-adapted data conversion and compression as well as automatic detection of different variants of the same gesture via clustering with a suitable metric inspired by Jaccard metric. The combination of Hidden Markov Models and clustering leads to robust detection of different executions based on a small set of training data. We achieved an increase of 5% recognition rate compared to regular Hidden Markov Models. The system has been used for human-machine interaction and might serve as an assistive system in physiotherapy and neurological or orthopedic diagnosis.
Based on a survey among customers of seven German municipal utilities, we estimate hierarchical multiple regression models to identify consumer motivations for participating in P2P electricity trading and develop implications for marketing strategies for this currently relatively unknown product. Our results show a low importance of socio-demographics in explaining differences between consumer groups, but high influence of attitudes, knowledge and likelihood to purchase related products. The most valuable target groups for P2P electricity trading marketing strategies of municipal utilities first and foremost should aim at are innovators, especially prosumers. They are well-informed about and open minded concerning electricity sharing and highly environmentally aware. They ask for transparency and are willing to purchase related products. They are attracted by the ability to share generation and consumption and to a lesser extent by economic reasons. Our results indicate that the marketing efforts should to a special degree take peer effects into account, as they are found to wield great influence on general openness towards and purchase intention for P2P electricity products. Finally, municipal utilities should build on the high level of satisfaction and trust of consumers and use P2P electricity trading as measure to keep and win customers willing to change their supplier.
Die Steigerung der Energieeffizienz ist eine gesellschaftliche Notwendigkeit und bildet neben dem Umstieg auf erneuerbare Energien den entscheidenden Hebel zur Realisierung der Energiewende und Minderung der CO2-Emissionen in Deutschland. Kleine und mittlere Unternehmen (KMU) nehmen in diesem Zusammenhang eine besondere Stellung ein: Aktuelle Studien deuten auf geringere Steigerungsraten der Energieeffizienz gegenüber Großunternehmen hin, die zumeist mit unterschiedlichen materiellen und personalen Voraussetzungen erklärt werden.
Das Forschungsprojekt "Entscheidungen für Energieeffizienz" widmete sich vor diesem Hintergrund der Situation produzierender KMU in Baden-Württemberg. Mit dem Ziel, ein verbessertes Verständnis über die Energieeffizienz-Entscheidungen der KMU zu gewinnen, wurde der Frage nachgegangen, wie der Umgang mit Energie in der täglichen Praxis in KMU organisiert wird, wie über Energieeffizienz entschieden wird und welche Treiber und Hemmnisse sich dabei ergeben.
Zur Beantwortung der Fragen wurde ein Ansatz verfolgt, der kulturelle Einflüsse mitberücksichtigt. Forschungsstrategisch kam ein Mixed-Methods-Ansatz zur Anwendung, der durch die Kombination von qualitativen Daten (Einzelfallstudien) und quantitativen Daten (Fragebogenerhebung) methodisch umgesetzt wurde.
Contemporary public enterprises differ from their forebears. Today, they are more similar to private enterprises, receiving far more attention than previously, when privatization processes all over the world were in the spotlight. Furthermore, the broad research stream of entrepreneurship has so far neglected the consideration of public enterprises. To set a future research agenda, the author examines the dispersed literature using an integrative and organizing framework to identify major topics and research findings. This paper reviews articles that investigate the entrepreneurship in contemporary public enterprises. Despite the growing scholarly interest globally, this systematic literature review indicates there is no more than a loose connection between the literature streams of public entrepreneurship and corporate entrepreneurship. Specifically, the review shows that the multidimensional concept of entrepreneurial orientation has thus far been ignored, although autonomy plays a significant role in the literature review, namely in the context of the interference of the public owner. It also reveals other essential research gaps, such as the development of a modern theory of public enterprises. The linked research stream of public-sector corporate entrepreneurship offers a broad area of scholarly research and should encourage further investigation.
Um die ökologischen und ökonomischen Potenzaile der Elektromobilität zu nutzen, setzen kommunale Energieversorger heute auf das Betreiben öffentlicher Ladestationen, den Handel mit Ladestationen und das Bereitstellen spezieller Elektromobilitätstarife; ebenso auf elektrifiziertes Carsharing oder das Vermieten elektrifizierter Fahrzeuge und den Betrieb elektrifizierter Omnibusse im ÖPNV. Auch die Entwicklung und Planung individueller Elektromobilitätskonzepte, teils in Kombination mit Photovoltaikanlage, gehören in einigen Unternehmen zum Portfolio. Für die Zukunft sollten Stadtwerke ihre Aktivitäten im Bereich Elektromobilität an individuell definierten Zielen und Strategien ausrichten.
The complexity of supply chains increases, especially due to the geographical spread of supplier and customer networks. In the connected and automated supply chains of the industry 4.0, even more nodes are incorporated in supply chains. This paper discusses the possible improvement of process quality in the industry 4.0 through the different blockchain and distributed ledger technologies. We derived hypotheses from a literature review and asked German blockchain experts from the industry to validate and discuss the hypotheses. We find that the different blockchain technologies and consensus algorithms have different strength with regard to quality improvement. One central finding is that IOTA, developed especially for the IoT and deemed the ’next evolutionary step’ is scalable and hence may increase the process efficiency, but at the same time is more vulnerable than other blockchain implementations, which again may reduce the overall process quality.