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It is well established that ductile iron (DI) with an ausferritic matrix shows superior mechanical properties compared to the conventional ferritic/pearlitic cast irons. Due to its excellent strength and toughness combination, ausferritic DI can compete successfully in the steel and aluminum markets. The goal of this work was to develop a process to produce as-cast ausferritic DI without a subsequent heat treatment. DI keel blocks were poured in our metal casting laboratory. After a premature shakeout at high temperature, the castings were cooled in air until the temperature range for the ausferritic transformation, and then introduced in an insulating medium holding them during the ausferritic reaction. Several holding temperature-time combinations and their effect on microstructure and properties were investigated. With the appropriate combination, the as-cast ausferritic DI satisfied the requirements of ASTM A897/897M- 06 (2011) for ADI. Steering knuckles were also produced and their mechanical properties evaluated matching the ADI grade 750/500/11.
Kirchenglocken werden beim Läuten aufgrund der Wirkung unterschiedlicher Schädigungsmechanismen hoch beansprucht. Einerseits tritt aufgrund des Klöppelanschlags im Bereich der Anschlagstellen an der Glocke Schlagverschleiß auf, der zur Schwächung des Schlagrings führt, andererseits bewirkt der Klöppel beim Läuten der Glocke abhängig von den dynamischen Eigenschaften des Systems aus Glocke, Joch, Klöppel und Läutemaschine lokal hohe Verformungen, die zu Ermüdungsschäden führen können. Diese Gefahr von Ermüdungsschäden kann durch eine optimierte Abstimmung des dynamischen Systems vermieden oder eingedämmt werden. Das Drehen von Glocken um etwa 20-30 kann zu einer Verlängerung der Lebensdauer von Glocken führen, da die Beanspruchungen über den Umfang nicht homogen sind. Fortschreitende Schäden an Glocken führen zu hörbaren Veränderungen des Klangs, die sich auch mithilfe geeigneter Analysen an Tonaufnahmen identifizieren lassen. Derzeit wird dieses Verfahren so weitreichend verfeinert, dass bereits solche Schaden erkannt werden, die selbst durch das geschulte Gehör noch nicht bemerkt werden.
In den letzten Jahren ist ein bruchmechanischer Prüfnachweis für viele Anwendungen von duktilen Gusseisen mit Kugelgrafit notwendig geworden. Die aktuellen Prüfmethoden erfordern jedoch einen hohen Anlagen-, Probenherstellungs- und Arbeitsaufwand, um entsprechende Kennwerte zu ermitteln. Daher wurde seit 2013 an der Hochschule für angewandte Wissenschaften Kempten (im Zuge des BMBF Vorhabens "GussTough") ein alternatives Prüfverfahren auf Basis des instrumentierten Kerbschlagbiegeversuches entwickelt. Neben einigen kleineren Modifikationen wurde hierfür ein bestehendes Pendelschlagwerk mit einem auf der Elektropotenzialdifferenz basierenden Risslängenmesssystem nachgerüstet sowie die Prüfsoftware umfassend modifiziert und um ein variables Berechnungsmodell ergänzt. Als Nachweis der Befähigung des Anlagenprototypen wurden umfangreiche Versuchsreihen durchgeführt, mittels welcher eine Kalibrierung des instrumentierten Pendelschlagwerks als auch der Risslängenmessung durchgeführt werden konnte. Die Validierung anhand einer Referenzprüfung an einer servohydraulischen Prüfanlage ergab für EN GJS 400-18-LT eine J-Integral-Ergebnisdifferenz von 15,45% (0,76 kJ/m2) bei einer kombinierten Standardabweichung von 50,54% (2,85 kJ/m2) unter einer Datenbasis von ca. 40 Proben je Verfahren. Die hohe Streuung ist teilweise mit dem heterogenen Probenwerkstoff begründbar, weshalb zum aktuellen Zeitpunkt weitere Versuchsreihen an homogenen Werkstoffen sowie weitere Optimierungsmaßnahmen umgesetzt werden, um die Belastbarkeit der ermittelten Kennwerte zu erhöhen.
The main customers of ductile cast iron are within the wind energy, the automotive and the general plant construction sector. Nowadays these customers frequently demand fracture mechanical evidence of the provided casts because of new design and certification guidelines (e. g. GL-DNV, FKM, BAM etc.). The determination of fracture mechanical values is possible using dynamic testing machines like servohydraulical or linearelectrical systems with a crack parameter sensor. In general these testing procedures are very time consuming and expensive (especially the testing facility itself). Alternative multiple-specimen-techniques only shift the expenses from the testing facilities and specimen to labor cost and are also not economically reasonable for small and medium sized foundries. One of the side tasks of the research project GussTough is the development of a Charpy Pendulum based single-specimen fracture mechanical testing technique which is able to provide fracture mechanical values for ductile and brittle material behaviour. The centerpiece of the development is the integration of an Alternating Current Potential Drop (ACPD) crack length measuring system. With a heavily modified calculation model based on SEB (Single Edge Bend) specimen and this crack parameter it is possible to create a J - Δa diagram out of one Charpy-V specimen.
Nachdem im ersten Teil untersucht wurde, mit welchen Methoden die Key- Performance-Indikatoren einer gegebenen Datenmenge ermittelt werden können, werden diese Methoden auf zwei betriebliche Datenmengen angewendet. Die Vorgehensweise wird zunächst an einer hinreichend vollständigen Datenmenge für die Fließspannung der Stahlsorte C15 ausführlich erläutert. Anschließend wird eine Datenmenge aus dem Gießereibereich betrachtet, mithilfe derer die mechanischen Eigenschaften von duktilem Gusseisen mit Kugelgraphit auf Basis der chemischen Analyse prognostiziert werden. Die Analyse von Prozessdaten mit Hilfe maschineller Lernverfahren stellt in der Stahlherstellung und -Verarbeitung einen mittlerweile in verschiedensten Prozessen validierten und verifizierten Weg zur Prozessstabilisierung und Optimierung im Hinblick auf Material- und Energieverbrauch, Ausschussminimierung und Eigenschaftsoptimierung dar. Wie beide erläuterten Beispiele zeigen, ist es dabei von größter Bedeutung, sich über die eine Zielgröße bestimmenden relevanten Wirkparameter des jeweiligen Prozesses im Klaren zu sein. Sind diese Informationen tatsächlich vollständig und sicher gemessen, zugeordnet und für eine statistische Analyse digital verfügbar, können datengetriebene Prozessmodelle (Prognosefunktionen) berechnet werden, die wiederum zur Optimierung und Steuerung von Prozessen benutzt werden können. Das vorliegende Beispiel aus einer Eisengießerei zeigt in diesem Zusammenhang, wie komplex sich letztendlich die Wirkzusammenhänge darstellen. Diese Komplexität ist bekannt, in Gießereien wird auf dieser Wissensgrundlage produziert. Soll aber eine laufende Fertigung mit den oben beschriebenen Werkzeugen optimiert oder letztlich auch gesteuert werden, muss in eine adäquate Ursache-Wirkungsanalyse, zielführende Datenerfassung sowie Datenmanagement investiert werden. Gemeinsam bilden diese eine Basis für eine erfolgreiche Prozessanalyse mit maschinellen Lernmethoden.
Daten bilden das Fundament der digitalisierten Wirtschaft. Der rapide Zuwachs produzierter Datenmengen - beispielsweise durch Integration digitaler Mess-, Steuer- und Regelsysteme in der Prozessindustrie - erschwert es, diejenigen Parameter einer gegebenen Datenmenge herauszufinden, die einen wesentlichen Einfluss auf die Qualitätsmerkmale eines Prozesses haben. Innerhalb dieser können Key- Performance-Indikatoren gefunden werden. Im vorliegenden Artikel wird untersucht, mit welchen Methoden des Bereichs Predictive Analytics diese Indikatoren einer geeigneten Datenmenge gefunden werden können. Dazu wurden Kriterien entwickelt, welche das Potenzial der Prognostizierbarkeit einer Datenmenge beurteilen können. Bei hinreichend guter Datenqualität können diese Indikatoren beispielsweise mit einer Sensitivitätsanalyse ermittelt werden.
One of the most complex manufacturing processes is the foundry process which consists of several sub-processes linked together to a complex process chain. The foundry process is defined by the individual dependencies between the process parameters and variables as well as by several elements of uncertainty which affect the stability of any sub-process applied and, consequently, product quality. The final quality of a cast part is made in a process situation where anything and anyone has direct control and correcting possibilities over the process. This fact induces strictly the demand on an extremely accurate and in advance control of all sub-processes. To this end, it is necessary to know and finally to control all causes and factors that contribute to the final quality of the cast part. The integrated control of this process, therefore, is a complex and challenging task. The main requirement of foundries is tools which are able to perform data analysis under consideration of any influences of sub-processes on manufacturing quality. This implicates highest flexibility regarding the availability and applicability of different data analyzing tools. During the last 20 years, several different methods have been developed for data analyzing in manufacturing processes. These are mainly Neural Networks (NN), Bayesian Networks (BN), further statistical data analyses and expert systems. Most of these tools have been designed for a specific application and do not have the ability to be applied on foundry problems. Due to the specific algorithms of analyses each of them provides separate results which are strongly related mostly to one sub-process. Correlation and interaction between several processes, parameters and variables are difficult to establish. An intelligent process control by self-adjusting systems which automatically trace back specific product quality attributes to input variables and fitting these to specified output results is hardly available. In many applications of these methodologies, it has also been substantiated that it is not possible to meet the demands of an intelligent process control using only a single tool, or simple combination of different tools. This is the basic problem using standard control tools in complex manufacturing processes like foundries. Against this background, we present here a new prediction methodology for foundry process that, on the basis of several machine learning methods, is able to perform a comprehensive analysis as well as preparation of data before it is provided as input to prediction tools. This methodology is implemented as software EIDOminer. The weaker tools, that is, which cannot predict good enough quality characteristics of the existing production process, are switched off automatically by socalled Supervisor in IAM of EIDOminer software. The Supervisor determines, for a given process, which analysis method or combination of methods achieve best prediction results and provide a single optimal output result. After learning from the quality data of a product, the software can give prediction in a run time. The software is tested in two German foundry enterprises and the implemented approach shows significant results.
Der vorliegende Artikel untersucht in einem Modell ohne Marktverzerrungen in Form von Umlagen als Bestandteil des Strompreises die Wirtschaftlichkeit der dezentralen Spitzenlasterzeugung anhand der Stromgestehungskosten. Analysiert wird konkret der Einsatz von Gas-, PV-Freiflächen- und Windenergieanlagen. Das Ergebnis dieser Untersuchung ist zum einen, dass der Aufbau von dezentralen Erzeugungskapazitäten zur Deckung der Spitzenlasten vor Ort im Vergleich zum Bezug aus dem vorgelagerten Netz bereits heute wirtschaftlich ist. Zum anderen wird geklärt, wann und unter welchen Rahmenbedingungen die Wirtschaftlichkeit des Einsatzes von Stromspeichertechnologien zur Verwendung der jährlichen Überschussstrommengen aufgrund der regenerativen Stromerzeugung als Lastmanagementmaßnahme gegeben ist.
Der Projektverbund UMWELTnanoTECH wurde 2013 vom Bayerischen Staatsministerium für Umwelt und Verbraucherschutz gestartet und erstreckte sich über eine Laufzeit von drei Jahren. Es waren neun bayerische Hochschulen beteiligt. Die insgesamt zehn Teilprojekte gliederten sich in neun Forschungsprojekte und ein Koordinierungsprojekt. Jeweils drei der Forschungsprojekte waren in den thematischen Schwerpunkten Organische Photovoltaik, Energiespeicher und Thermoelektrizität zusammengefasst. Über die Tätigkeiten des Verbunds wurde in mehr als 70 Beiträgen berichtet, darunter über 30 wissenschaftliche Originalartikel in internationalen Fachzeitschriften und über 15 Konferenzbeiträge. Es wurden mehrere Kapitel für Fachbücher verfasst, in die die Erkenntnisse der Projekte eingeflossen sind. Ziele und Ergebnisse der Projekte wurden in knapp 20 nichtwissenschaftlichen Beiträgen und Meldungen im Internet, in Magazinen und Berichten zusammengefasst. In allen Schwerpunkten konnten die untersuchten nanotechnologischen Anwendungen auch mit Hilfe umweltverträglicherer Verfahren und Materialien realisiert werden, ohne dadurch entscheidend an Leistungsfähigkeit einzubüßen.
In this article we present a method which indicates the most important parameters of influence concerning the fuel consumption and regulated emissions. Using RDE measurements a consumption map of the vehicle and enhanced mathematical models are created that allow the prediction of fuel consumption and emissions for simulated driving routes.
The results show that the simulated fuel consumption fits the measured consumption of the vehicle very good. The deviations between calculated and measured NO2 and NO are relatively high. This is due to the lack of simulation of the emissions after-treatment which is not possible as the relevant parameters are not monitored.
Further investigations are planned for hybrid vehicles, extended environmental con-ditions and modelling of the aftertreatment.
Hintergrund: Fluktuierende erneuerbare Energien erfordern flexible Kraftwerke zum Lastausgleich
Projektziele: Erhöhung der Flexibilität kommunaler Kraft-Wärme-Kopplungsanlagen (KWK) durch:
- Optimierte Anlagendynamik
- Wärmespeicherung
- Nutzung von Power-to-Heat
- Einbindung von Strommärkten
Vorgehensweise:
- Instationäre Prozesssimulation der Anlagen
- Nicht-lineare Optimierung der Anlageneinsatzplanung
- Demonstration durch Einbindung in die Leitstandstechnik
- Erstellung eines Betreiberleitfadens
Load Forecasting in District Heating Systems Using Stacked Ensembles of Machine Learning Algorithms
(2021)
For district heating, heat demand forecasting is playing a key role for an optimised power plant dispatch. Machine Learning can help to significantly improve forecasts of thermal loads. The prediction quality of neural networks is higher than that of decision trees in most cases. However, compared to decision trees neural networks have weaknesses when extrapolating outside known ranges. This work presents a novel method called “Deep DHC” (Deep Learning for District Heating and Cooling), which combines these two approaches in order to benefit from strengths of both methods. On the one hand, the novel approach uses conventional decision tree based regression algorithms such as the AdaBoost and Random Forest, as well as artificial neural networks. In addition to common feed forward neural networks (FNN), a deep learning network structure, which consists of long short-term memory (LSTM) cells, is used for the first time. The LSTM method has already proven to be very powerful in modern speech recognition. In order to achieve best possible heat demand forecasts, the aforementioned methods for load forecasting are combined and weighted by an additional machine learning method. Results show that it is possible to achieve a further improvement in forecasting quality for district heating loads by purposefully combining individual forecasting methods. Hence, mean and absolute deviations are significantly reduced in comparison to the individual methods.
Es wurde der Ansatz der Phosphorrückgewinnung aus Klärschlammasche durch Mitverwertung bei der konventionellen nasschemischen Phosphorsäureherstellung untersucht. Laborversuche mit realen Klärschlammaschen unter simulierten Industriebedingungen ergaben, dass eine direkte Beimischung der Asche zum Primärrohstoff Rohphosphat verschiedene verfahrenstechnische Nachteile mit sich bringt. Als Alternative zur direkten Beimischung wird das verfahrenstechnische Konzept der Rückstromextraktion vorgeschlagen, dessen Umsetzung einige der identifizierten Nachteile umgeht.
City busses and coaches are typically ventilated with high fresh air rates without monitoring of air quality according to recommendations and requirements of associations of public transport companies. The air quality of cabin air regarding humidity and CO2-concentration depends however on the number of passengers. Hence the air quality of the ambient air could be monitored and air conditioning units could be switched on re-circulation air, which is called here “monitored fresh air rate”. Average occupancy of city busses is 30 %. This means the cabin will be ventilated with a surplus of about 70 % of the required fresh air. This causes a high energy consumption which could be saved. The aim of this work is the monitoring of the cabin air quality with the help of sensors and development of appropriate control algorithms that could reduce energy consumption without any impairment of safety, comfort, stress and health.
This paper describes the process of developing a technology roadmap for deploying bioenergy technologies at a country level. A method for energy technology roadmapping adapted to the conditions of developing countries is proposed. This method combines an acknowledged roadmapping framework from prior art, a new strategy to build consensus based on the Delphi method and a strong focus on analytical modeling for supporting expert judgment. This method aims to be simple, transparent and affordable. The proposed method is applied to Colombia for creating a plan to deploy sustainable bioenergy technologies in Colombia until 2030. This plan consists of a set of long-term goals, milestones, barriers and action items identified by over 30 experts for key bioenergy technology areas (viz. bioethanol, biodiesel, renewable diesel, biomethane, biogas, waste-to-energy and power generation and combined heat and power). Finally, the relevance of the process of developing a technology roadmap for bioenergy exploitation in Colombia in other developing countries is discussed.
Diese Formelsammlung umfasst die Gebiete technische Thermodynamik, technische Strömungsmechanik, Wärmeübertragung und in geringerem Umfang auch die Stoffübertragung. Sie basiert auf den gleichnamigen Vorlesungen der Autoren an der Hochschule für angewandte Wissenschaften Kempten.
Systematisch gegliedert werden in der Formelsammlung grundlegende Berechnungsgleichungen, umfangreiche Stoffdaten sowie Lösungsdiagramme für wichtige Berechnungsfunktionen bereitgestellt. Aus Gründen der Kompaktheit und Übersichtlichkeit wird dabei weitgehend auf Erläuterungen von Gleichungen und Formelzeichen verzichtet. Die Formelsammlung eignet sich daher besonders als vorlesungs- oder prüfungsbegleitendes Hilfsmittel für Studierende in Ingenieurstudiengängen an Hochschulen oder Universitäten. Eine weitere Zielgruppe bilden Ingenieure mit entsprechenden Vorkenntnissen, die im Berufsalltag schnell auf wesentliche Gleichungen und Daten zugreifen möchten.
Ökonomische Aspekte von CCS
(2015)
Brennstoffzellensysteme mit oxidkeramischer Brennstoffzelle (SOFC) eignen sich besonders für eine hocheffiziente und emissionsarme Energiebereitstellung. Aufgrund der für diesen Brennstoffzellentyp nur sehr begrenzt vorhandenen Betriebserfahrungen ist das Ziel der vorliegenden Arbeit, eine möglichst verallgemeinerbare dynamische Systemsimulation für SOFC-Kraftwerke zu entwickeln. Auf diese Weise können bereits im Vorfeld des Anlagenbetriebes Wechselwirkungen zwischen Teilsystemen analysiert sowie Strategien für einen ressourcensparenden Betrieb entworfen werden.
Die in dieser Arbeit vorgestellte Systemsimulation basiert auf einem gemeinsamen generischen Modellansatz für sämtliche Prozesseinheiten. Die Modelldetails der einzelnen Anlagenkomponenten orientieren sich an realen Bauteilen eines am Forschungszentrum Jülich im Aufbau befindlichen 20 kW Brennstoffzellensystems. Vor diesem Hintergrund stehen umfangreiche Messdaten zur Verfügung, mit denen alle entwickelten Komponentenmodelle validiert werden.
Dynamische Systemrechnungen für sämtliche Betriebszustände wie Aufheizen, Anfahren, Nenn- und Teillast sowie eine Außerbetriebnahme bilden den Schwerpunkt der Arbeit. Für den Aufheizvorgang werden in Bezug auf den Energie- sowie Zeitbedarf optimierte Betriebsstrategien ermittelt. Die simulierte Aufheizzeit von Raumtemperatur auf 600°C liegt für das betrachtete SOFC-System unter den gegebenen Randbedingungen bei mindestens fünf Stunden. Das anschließende elektrochemische Anfahren bis in den Nennlastzustand dauert rund eine Stunde. Wie die Untersuchungen zeigen, lassen sich in der Regel sowohl Lastreduzierungen als auch -erhöhungen unverzüglich durchführen, sofern sich das System nahe seiner Betriebstemperatur befindet. Ein stabiler Betrieb der SOFC-Anlage bei Teillast ist zudem selbst bei geringen Stromdichten möglich. Lediglich für einen mehrstündigen reinen Stand-by-Betrieb muss das System durch Wärmezufuhr auf Temperatur gehalten werden. Mit einem hohen Kühlluftzusatz lässt sich ein Abkühlvorgang im Rahmen einer Außerbetriebnahme derart forcieren, dass alle Systemkomponenten innerhalb eines Tages wieder Umgebungstemperatur erreichen.
Die Berechnungen erfolgen für ein SOFC-System mit separater Bereitstellung von Wasserdampf für die Vorreformierung. Die Simulation einer zusätzlichen Anlagenkonfiguration, in der mittels eines Ejektors Anodenabgas rezykliert wird, zeigt zudem Möglichkeiten einer weiteren Steigerung des Gesamtwirkungsgrades auf.
High temperature fuel cells are considered a promising option for highly efficient distributed power generation. This paper presents a dynamic model of a solid oxide fuel cell (SOFC) system. Detailed models for all process components were developed and validated with experimental data, which is demonstrated using the burner model as an example. Focus of this paper is on SOFC system heat-up. Different strategies are discussed, and dynamic simulation results of heat-up processes are shown.
Development and validation of a hybrid simulation model for Darrieus vertical-axis wind turbines
(2019)
The increasing interest in deep-water floating applications and in wind turbine installations in turbulent flows, is putting vertical-axis wind turbines back again in research agendas. However, due to the lack of activities in past years, the accuracy and robustness of available design tools is much lower than the corresponding ones for horizontal-axis rotors. Moving from this background, the study presents the development of a hybrid simulation model able to simulate H-type Darrieus turbines with low computational effort and an accuracy higher than that of conventional low-fidelity models. It is based on the coupling of unsteady RANS CFD with the Actuator Line theory to replace the airfoils. The present tool has been implemented within the commercial solver ANSYS® FLUENT® and it is then of practical interest for a large number of potential users. With respect to other examples in the literature, the present approach includes some new findings in the correct manipulation of airfoil polars that notably increased its accuracy. The validation of the model is assessed by means of two different study cases featuring a simplified 1-blade rotor and a real 3-blade turbine, for which both detailed CFD simulations and experiments were available. The model was able to produce accurate results - both in terms of aggregate power production and of flow field description - for turbines with a medium-low chord-to-radius ratio and the tipspeed ratios typical of turbine operation.
Recently, an increasing interest has been devoted to external combustion cycles (e.g. supercritical CO2 Brayton cycles) due to the opportunity to use low quality fuels. Among these, the use of biomass is of particular relevance for its low environmental impact. On the other hand, the combustion of biomass has several critical aspects that might hamper the efficiency of the process, especially in case of solid biomass (woodchip). A detailed experimental analysis of biomass woodchips behavior inside the combustion bed can provide useful information on fuel distribution, combustor loading pattern, fuel segregation and stacking. Unfortunately, a detailed experimental analysis is quite hard to perform due to the harsh environment, the difficulty in setting up a well scaled model of the device (both as geometrical and power sizes) and an efficient particle tracking method. Regarding this last issue, in this study, an optical tracking method to provide information on the main pattern of motion of the fuel inside of a model of biomass fixed bed combustion system is proposed.
Tests were performed without combustion, by inserting the woodchips in the bed through a charging screw. A portion of the fuel has been colored according to its size with negligible modification of the particles mass and dimensions. A digital camera, placed above the bed, was used to constantly capture pictures of the bed surface. The position of the screw during its revolution was correlated to the acquired images. A Matlab tool was developed to detect the movement of the particles on the top of the fuel bed over time (theoretically exposed directly to the flame) by distinguishing the path according to the particle sizes.
The motion of the particles was detected by using a specifically developed procedure which operates in four steps:
1) Image resizing to avoid perspective deformation or orientation variations (a set of reference pins was installed on the test bed and used to have all the images with the same orientation and size)
2) Identification of the particle size by detecting their color
3) Sseparation of the images in sub images according to particle size
4) Detection of particle position and definition of particle centers
5) Calculation of particle motion by comparing the particle center position in subsequent images
The procedure, allowed the detection of the particles preferential pattern as a function of their size and the bed parameters. The results were particularly useful to understand potential inefficiencies of the combustion system due to an uneven woodchips distribution. In addition, the results achieved with the proposed test rig and the adopted methodology can also be used to validate results from Discrete Element Modelling (DEM) simulations.
The present study investigated the mental workload associated with driving a vehicle equipped with Lane Keeping Assistance System (LKAS). Specifically, an experiment was carried out with16participants driving with LKAS in four real-world scenarios. Effects on mental workload were evaluated with psychophysiological measures such as heart rate and skin conductance response (SCR). The driving performance, which is also a measure of evaluating mental workload, was assessed by measure such as steering reversal rate, variation of lateral position and steering effort. The result suggested that LKAS has reduced physical workload in the steering task. However, the lane keeping performance was not improved. Moreover, the NASA-TLX showed that participants perceived higher mental workload while driving with LKAS. This effect was mirrored in the SCR. The objective data showed that LKAS was associated with higher steering reversal rate, which might explain the reason of participants perceiving higher mental workload. Overall, it was suggested that the mental workload was higher with the tested LKAS.
Due to the rapid progress in the development of automated vehicles over the last decade, their market entry is getting closer. One of the remaining challenges is the safety assessment and type approval of automated vehicles, as conventional testing in the real world would involve an unmanageable mileage. Scenario-based testing using simulation is a promising candidate for overcoming this approval trap. Although the research community has recognized the importance of safeguarding in recent years, the quality of simulation models is rarely taken into account. Without investigating the errors and uncertainties of models, virtual statements about vehicle safety are meaningless. This paper describes a whole process combining model validation and safety assessment. It is demonstrated by means of an actual type-approval regulation that deals with the safety assessment of lane-keeping systems. Based on a thorough analysis of the current state-of-the-art, this paper introduces two approaches for selecting test scenarios. While the model validation scenarios are planned from scratch and focus on scenario coverage, the type-approval scenarios are extracted from measurement data based on a data-driven pipeline. The deviations between lane-keeping behavior in the real and virtual world are quantified using a statistical validation metric. They are then modeled using a regression technique and inferred from the validation experiments to the unseen virtual type-approval scenarios. Finally, this paper examines safety-critical lane crossings, taking into account the modeling errors. It demonstrates the potential of the virtual-based safeguarding process using exemplary simulations and real driving tests.
When will automated vehicles come onto the market? This question has puzzled the automotive industry and society for years. The technology and its implementation have made rapid progress over the last decade, but the challenge of how to prove the safety of these systems has not yet been solved. Since a market launch without proof of safety would neither be accepted by society nor by legislators, much time and many resources have been invested into safety assessment in recent years in order to develop new approaches for an efficient assessment. This paper therefore provides an overview of various approaches, and gives a comprehensive survey of the so-called scenario-based approach. The scenario-based approach is a promising method, in which individual traffic situations are typically tested by means of virtual
simulation. Since an infinite number of different scenarios can theoretically occur in real-world traffic, even the scenario-based approach leaves the question unanswered as to how to break these down into a finite set of scenarios, and find those which are representative in order to render testing more manageable. This
paper provides a comprehensive literature reviewof related safety-assessment publications that deal precisely with this question. Therefore, this paper develops a novel taxonomy for the scenario-based approach, and classifies all literature sources. Based on this, the existing methods will be compared with each other and,
as one conclusion, the alternative concept of formal verification will be combined with the scenario-based approach. Finally, future research priorities are derived.
Unified Framework and Survey for Model Verification, Validation and Uncertainty Quantification
(2020)
Simulation is becoming increasingly important in the development, testing and approval process in many areas of engineering, ranging from finite element models to highly complex cyber-physical systems such as autonomous cars. Simulation must be accompanied by model verification, validation and uncertainty quantification (VV&UQ) activities to assess the inherent errors and uncertainties of each simulation model. However, the VV&UQ methods differ greatly between the application areas. In general, a major challenge is the aggregation of uncertainties from calibration and validation experiments to the actual model predictions under new, untested conditions. This is especially relevant due to high extrapolation uncertainties, if the experimental conditions differ strongly from the prediction conditions, or if the output quantities required for prediction cannot be measured during the experiments. In this paper, both the heterogeneous VV&UQ landscape and the challenge of aggregation will be addressed with a novel modular and unified framework to enable credible decision making based on simulation models. This paper contains a comprehensive survey of over 200 literature sources from many application areas and embeds them into the unified framework. In addition, this paper analyzes and compares the VV&UQ methods and the application areas in order to identify strengths and weaknesses and to derive further research directions. The framework thus combines a variety of VV&UQ methods, so that different engineering areas can benefit from new methods and combinations. Finally, this paper presents a procedure to select a suitable method from the framework for the desired application.
This paper proposes a methodology for determining strategically bundled relevant test scenarios for the simulation- based evaluation of sensor constellations. This is achieved by gogri identification of important use cases for the autonomous driving operation, (b) the conversion of these use cases into Regions of Interests (ROIs) around the vehicle along with (c) a definition of a critical index (CI) for each of these regions and (d) a procedure to derive crucial scenarios and (e) categorise them into scenario families. The derived test scenarios help to optimise the field of view of the sensor constellation for the most important regions around the ego vehicle. The novelty lies in its independence from traditional methods of deriving test scenarios and its capability of providing targeted feedback to improve the sensor constellation at the identified pain points. The test scenario families can reduce the development time of highly automated vehicles by providing virtual testing of the sensor constellation performance in the vehicle concept phase.
Two-Dimensional ECMS for System Analysis of Hybrid Concepts featuring Two Electric Traction Motors
(2019)
This work is focusing on the extension of the well-known equivalent consumption minimization strategy (ECMS) for analysis of new hybrid electric vehicle (HEV) concepts featuring two traction motors. Given the contribution to advanced systems engineering, the control algorithm is derived under consideration of causality and practicality. Having more than one traction motor, a two-dimensional torque-split allowing full parallel operation of the HEV powertrain is required. Furthermore, this HEV enables series operation mode, and an example of implementation is given as well. Since we define the capability of comprehensive system analysis as a major attribute of the energy management, we abstain from restricting the solution space via heuristics e.g. mode selection in advance. This gives birth to affect the control behavior only by applying constraints directly to the control problem and thus enables analysis based on the respective (sub)optimal solutions. In this paper, a brief example of implementing so-called soft constraints for reducing the number of engine starts is given. The practicality of the proposed 2D-ECMS is proven within a simulation study and control behavior is analyzed. Additionally, different effects of variable constraints and parameter settings are investigated.
To find the optimal system-level design of hybrid electric vehicles (HEVs), component models are used in simulations to evaluate a large number of different designs within a high dimensional design space. As the electrical machine (EM) represents a key component of the HEV powertrain in terms of energy consumption, models require scalability and sufficient accuracy with manageable computational effort. This paper presents a novel approach for the development of scalable EM models based on Neural Networks (NN). The models are trained with data derived by a Finite Element Analysis (FEA) based scaling procedure and capable to represent the characteristics of a wide range of EM designs without the incorporation of further details. Once a model is trained, it can be directly used in system-level design optimization. The practicality of the model is proven within an exemplary simulation study and its goodness of fit to the training data is validated by a statistical analysis. This approach can help to reduce the computational effort of EM efficiency maps calculation, since only a small number of time-consuming FEA based scaling simulations must be performed prior to the optimization.
Polymer materials that regulate the relative humidity in their environment are relevant for applications in the packaging and building sectors. By integration of salts in polymer structures, such materials are able to absorb and desorb high amounts of water vapor. In this study, films of polylactic acid and polypropylene with dispersed calcium chloride (2 and 4 wt %) were produced and biaxially stretched to induce the formation of cavities. The resulting cavities in these films account up to 10 vol % and are able to contain emerging calcium chloride solution formed by water vapor absorption. These films absorb reversibly up to 15 wt % water vapor at 75% relative humidity at 23 °C. This absorption behavior is described by effective diffusion and effective sorption coefficients. Using a simple model, the effective water vapor diffusion coefficient of these films can be estimated from the permeation coefficient of the polymer and the sorption coefficient of the absorber.
Dieser Beitrag behandelt ein erweitertes analytisches Berechnungsmodell zum mechanischen Verhalten von beliebig rechtwinklig berandeten Mehrschraubenverbindungen (MV). Es werden die Modellvoraussetzungen, -einschränkungen, Theorie und Ergebnisgüte vorgestellt. Dazu werden die Ergebnisse des analytischen Berechnungsmodells den Ergebnissen der numerischen Untersuchungen gegenübergestellt.
Die mechanischen Eigenschaften additiv gefertigter Bauteile lassen sich nicht nur durch bessere Verfahrens- und Anlagentechnik steigern. Vor allem beim Lasersintern lohnt sich ein genauer Blick auf das eingesetzte Polymerpulver. Eine umfangreiche Untersuchung zeigt, warum und wie sich eine spezifische Pulverqualifizierung auswirkt.
The mechanical properties of additively produced components can only be increased by means of improved processing and plant technology. Particularly with laser sintering, a closer look at the polymer powder used is worthwhile. A comprehensive investigation shows why and how such a specific powder qualification has an effect.
Polymer powders for laser sintering must exhibit special intrinsic and extrinsic properties. A new concept for the characterization and evaluation of laser sintering powders permits conclusions to be drawn about aging as well as the suitability of novel powder systems – even before the first build job.
Um konkrete Kundenanforderungen beim Vertrieb neuer Fahrzeuge zuverlässig berücksichtigen zu können, wurde ein Verfahren erarbeitet, mit dem sich Straßen aus Sicht wesentlicher Einsatzparameter wie z.B. die Straßengüte, der Straßentyp sowie die Längs- und Querdynamik aus Sicht der Beanspruchung bewerten und kategorisieren lassen. Das Belastungs- und Beanspruchungsgeschehen lässt sich weitgehend fahrzeugunabhängig nach Höhe, Häufigkeit und Frequenz anhand erfasster Beschleunigungen zutreffend beschreiben. So können Straßen aus Sicht der Beanspruchung bewertet und in Wort und Bild beschriebenen Straßenqualitäts-klassen zugeordnet werden. Umgekehrt erlauben geeignete Kunden-Abfragen mittels eines Anforderungs- und Einsatzkataloges zu Straßenqualität und Einsatzparametern, die kundengerechte Konfiguration von Fahrzeugen.
Eine Möglichkeit zum verstärkten Schutz kühlpflichtiger Molkereiprodukte gegenüber den in der Logistikkette auftretenden mechanischen Belastungen besteht in der räumlichen Trennung von Lebensmitteln und Temperierelementen innerhalb der Versandverpackung. Je nach Art der Isolierverpackung kann das Temperaturhaltevermögen durch die optimierte Anordnung der Temperierelemente deutlich gesteigert werden.
Der Versand kühlpflichtiger Molkereiprodukten muss unter Einhaltung eines definierten Temperaturbereichs erfolgen. Die systematische Analyse auftretender Wärmetransportprozesse an Isolierverpackungen verdeutlicht deren Aufbau und Wirkungsprinzip und signalisiert ergebnisrelevante Einflussgrößen auf das Temperaturhaltevermögen.
Die rasant voranschreitende Digitalisierung treibt die Vermarktung und den Vertrieb von Lebensmitteln via Internet voran. Allerdings weisen die meisten Molkereiprodukte eine enorme Empfindlichkeit gegenüber den in der Logistikkette typisch auftretenden Belastungsarten auf. Die Sicherstellung eines hohen Qualitätsniveaus fordert deren verstärkten Schutz durch eine geeignete Versandverpackung.
In order to be able to reliably take account of specific customer requirements when selling new vehicles, a method has been developed with which roads can be compared from the point of view of essential operational parameters such as, evaluate and categorize the road grade, the type of road and the longitudinal and lateral dynamics in terms of the load. The load and stress conditions can be described largely vehicle-independent according to height, amount and frequency based on detected accelerations. Hence, roads can be assessed in view of stress and combined to street-quality classes described in words and pictures. Conversely, suitable customer queries by means of a requirement catalog for road quality and operational parameters allow a specific configuration of vehicles.
Equations of the form ?[?] = 0, ?: ? ⟶ ?̅ smooth, ?, ?̅ real Banach spaces are investigated with the aim of continuing the basic solution ?[0] = 0 with ? ′ [0] Fredholm operator to a solution curve ?[?(?)] = 0 with the implicit function theorem. If ? ′ [0] is surjective, then the transversality condition of the implicit function theorem can be satisfied in a straightforward way, yielding a regular solution curve, whereas otherwise the equation ?[?] = 0 has to be extended appropriately for reaching a surjective linearization accessible to the implicit function theorem. This extension process, implying in the first step the standard bifurcation theorem of simple bifurcation points, is continued arbitrarily, yielding a sequence of bifurcation results presumably being applicable to bifurcation points with finite degeneracy.
The system of undetermined coefficients of a bifurcation problem
?[?] = 0 in Banach spaces is investigated for proving the existence of families of solution curves by use of the implicit function theorem. The main theorem represents an Artin-Tougeron type result in the sense that approximation of order 2? ensures exact solutions agreeing up to order ? with the approximation
[13], [22]. Alternatively, it may be interpreted as Hensel’s Lemma in Banach spaces. In the spirit of [9] and [18], the required surjectivity condition is interpreted as a direct sum condition of order ? that allows for solving the remainder equation
with respect to graded subspaces derived from an appropriate filtration [24], [25]. In the direction of these subspaces, the determinant can be calculated in a finite dimensional setting, enabling the investigation of secondary global bifurcation phenomena by sign change of Brouwer’s degree [18]. The direct sum
condition seems to be a generalization of the direct sum condition introduced in [9].
The implicit function theorem delivers stability of ? leading coefficients [?̅1 , … , ??̅] with respect to perturbations of order 2? +1 and uniqueness in pointed wedges around the solution curves. Further, denoting by ?̅∞ the subset of arc space ?∞ with [?̅1 , … , ??̅] fixed, ?̅∞ is iteratively approximated by ?̅ 2?+? as ? → ∞. In addition, a lower bound of the Greenberg function ?(?) of a singularity is constructed by use of a step function obtained from ?-degree of different solution curves.
Finally, based on Kouchnirenko’s theorem [17] and an extension in [6], the results are applied to Newton-polygons where it is shown that the Milnor number of a singularity can be calculated by the sum of ?-degrees of corresponding solution curves. Simple ???-singularities are investigated in detail. The main theorem represents a version of strong implicit function theorem in Banach spaces, possibly comparable to theorems in [2]. Moreover, our aim is to extend the direct sum condition of order ? from [9] to certain topics in singularity and approximation theory. Generalizations to modules as well as specializations to polynomials seem to be promising.
A note on an expansion formula with application to nonlinear Differential-Algebraic-Equations
(2019)
In [DL] systems of differential polynomials are investigated with
respect to properties of Artin approximation type. The key tool in [DL] is an extended version of a formula by Hurwitz [Hu] expressing high order derivatives of an expansion by lower ones. The formula is further refined in [VFZ] to deliver sufficient conditions concerning the existence of power series solutions of scalar algebraic differential equations of order?.
In the paper at hand, the main results from [VFZ] are first reproduced and further extended to systems of nonlinear differential algebraic equations. In addition, a simple extension of Tougeron’s implicit function theorem is given in a specific constellation.
The results follow from [S1], [S2] where Artin approximation is treated within a Banach space setting, thereby constructing an expansion formula that expresses accurately the required dependency of low and high order derivatives within the system of undetermined coefficients.
Tougeron’s implicit function theorem and Hensel’s lemma are well known representatives concerning 2?-approximation/?-nondegeneracy implying existence of solutions with identity of order ?. This note aims to extend this
principle to equations ?[?] = 0 in Banach spaces, using ?-transversality concepts, which may geometrically be interpreted as generalized cones spanned by
submanifolds, each characterized by a certain expansion rate.
The number of manifolds in the cone, as well as their expansion rates, is recursively increased until an appropriate desingularization of the cone is build up
with linearization expressed by first ? + 1 derivatives of the singular operator
at the base point.
Along these lines, a well-defined submersion is constructed in the cone with
uniformly bounded inverse when approaching the singularity. The techniques
are restricted to curves, possibly touching by high order the singular locus of ?, but ultimately traversing it, in this way defining an isolated singularity of the
operator family given by the linearization along the curve.
The fine resolution of the cone by the manifolds represents an improvement
compared to measuring the variation of the nonlinear operator exclusively by
the overall behaviour of the determinant.
In case of finite dimensions, each half-cone is characterized by a constant topological degree that can be used to investigate a solution curve in general position with respect to secondary bifurcation.
The core of all considerations is given by some characteristic patterns, valid in
the system of undetermined coefficients that allow for detailed analysis of the
power series resulting from plugging the power series of the ansatz into the
power series of the nonlinear operator.
Open Source
(2020)
In der IT-Branche hat sich Open-Source-Software (OSS) heute durchgesetzt, führende IT-Konzerne verwenden Open-Source-Code und entwickeln ihn auch selbst. Doch auch für Unternehmen anderer Branchen bietet Open-Source-Software Potenzial. In diesem Beitrag erfahren Sie, dass Open-Source-Software nicht nur ein Schlagwort, sondern genau definiert ist,was es mit den Risiken von Open Source auf sich hat und wie man damit umgeht, welche Vorteile und Potenziale Open-Source-Software auch für Nicht-IT-Firmen bietet.
Im Projekt KWK-Flex untersuchte die Hochschule Kempten innovative Methoden und Anlagenbetriebsstrategien zur flexiblen, stromgeführten Fahrweise von Kraft-Wärme-Kopplungs-(KWK)-Anlagen in Fernwärmeverbundnetzen im Kontext steigender Anteile erneuerbarer Energien. Solche KWK-Anlagenverbunde im Leistungsbereich ab einigen MW werden in Deutschland aufgrund ihrer hohen Brennstoffnutzungsgrade und der daraus folgenden Ressourcen- und Klimafreundlichkeit von mehreren hundert Stadtwerken bzw. Fernwärmeversorgern betrieben.
Bei der Methodenentwicklung und den daraus resultierenden optimierten Anlagenbe-triebsstrategien standen neben den Zielgrößen Dynamik und Flexibilität der Strombe-reitstellung insbesondere die Ressourceneffizienz, d.h. hohe Wirkungsgrade, geringe Emissionen und hohe Wirtschaftlichkeit, sowie eine hohe Versorgungssicherheit im Fokus. Als Schwerpunkte des Forschungsvorhabens wurde Untersuchungen zur in-stationären Prozesssimulation von KWK-Kraftwerken mit dem Ziel der Erhöhung der stromseitigen Anlagendynamik mit dem Einsatz numerischer Methoden zur optimierten Anlageneinsatzplanung der Kraftwerke in KWK-Verbunden kombiniert.
Das Projekt wurde am Institut für Energie- und Antriebstechnik (IEAT) der Hochschule Kempten mit Unterstützung der beiden assoziierten gewerblichen Partner Fernwärme Ulm GmbH (FUG) und ZAK Energie GmbH (ZAK) sowie dem Fernwärmeversorgerdachverband AGFW | Der Energieeffizienzverband für Wärme, Kälte u. KWK e.V. durchgeführt.
Die verstärkte Einbindung fluktuierender erneuerbarer Energien erfordert hochflexible thermische Kraftwerke zur Netzstabilisierung und bedarfsgerechten Abdeckung der verbleibenden Netzlasten. Für einen effizienten Anlageneinsatz spielt dabei die möglichst genaue Kenntnis der zu erwartenden Fernwärmelast eine zentrale Rolle. Für die Fernwärmelastprognose können innovative Verfahren unter Verwendung moderner maschineller Lernverfahren zum Einsatz kommen, die im Folgenden vorgestellt werden.
Silica gel is a well-known desiccant. Through dispersion of silica gel in a polymer, films can be made that absorb and desorb water vapor. The water vapor absorption becomes reversible by exposing such films to a water vapor pressure below that of the water vapor pressure during absorption, or by heating the film. The intention of this study was to achieve a better understanding about the water vapor absorption, permeability (H2O, N2, O2, CO2), and mechanical properties of films with dispersed silica gel. Low-density polyethylene (PE-LD) monolayer films with a nominal silica gel concentration of 0.2, 0.4, and 0.6 g dispersed silica gel per 1 g film (PE-LD) were prepared and they absorbed up to 0.08 g water vapor per 1 g of film. The water vapor absorption as a function of time was described by using effective diffusion coefficients. The steady state (effective) water vapor permeation coefficients of the films with dispersed silica gel were a factor of 2 to 14 (8.4 to 60.2·10−12 mg·cm·(cm2·s·Pa)−1, 23 °C) higher than for pure PE-LD films (4.3·10−12 mg·cm·(cm²·s·Pa)−1, 23 °C). On the other hand, the steady state gas permeabilities for N2, O2, and CO2 were reduced to around one-third of the pure PE-LD films. An important result is that (effective) water vapor permeation coefficients calculated from results of sorption and measured by permeation experiments yielded similar values. It has been found that it is possible to describe the sorption and diffusion behavior of water by knowing the permeability coefficient and the sorption capacity of the film (Peff.≈Seff.⋅Deff.). The tensile stress changed only slightly (values between 10 and 14 N mm−2), while the tensile strain at break was reduced with higher nominal silica gel concentration from 318 length-% (pure PE-LD film) to 5 length-% (PE-LD with 0.6 g dispersed silica gel per 1 g film).
Polymers with dispersed desiccants are relevant for various packaging applications to protect packaged goods from water vapor. The intention of this study was to analyze and to describe a relevant system. Therefore, films with calcium oxide (CaO) were investigated, because such materials are hardly described in scientific literature. Monolayer films with 0.14 to 0.51 g dispersed CaO per 1 g film (PE‐LD) were prepared and they absorbed up to 0.2 g water vapor per 1 g of film. The water vapor absorption was described by effective diffusion coefficients. By the use of effective diffusion coefficients and the absorption capacity, the absorption behavior of layers with various thicknesses can be estimated. The steady state (effective) water vapor permeation coefficients of the films with dispersed CaO were a factor of 2 to 24 (8.4 to 101.5 mg cm [cm2 s Pa]–1 × 1012, at 23 °C) higher than for pure PE‐LD films (4.26 mg cm [cm2 s Pa]−1 × 1012, 23 °C). The tensile stress changed only slightly (pure PE‐LD: 9.5 N mm−2; PE‐LD with 0.14 g dispersed CaO per 1 g film: 8.1 N mm−2; PE‐LD with 0.51 g dispersed CaO per 1 g film: 10.5 N mm−2), while the tensile strain at break was reduced with higher CaO concentration from 318% (pure PE‐LD) to 10% (PE‐LD with 0.51 g dispersed CaO per 1 g film). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47460.
Packaging materials containing certain salts can regulate the humidity of packaged products. This study investigated whether thermoforming of foamed monolayer PP films with dispersed NaCl increases the water vapour sorption capacity and rate. Foamed monolayer PP-films (thickness 630 μm, porosity 0.28) with 6 (g/100 g) dispersed NaCl crystals were thermoformed to cups with depths up to 90 mm. By thermoforming the porosity increased up to 0.63 and the effective water vapour diffusion coefficient elevated by one order of magnitude from 10−11 to 10−10 cm²∙s−1. Therefore, such films absorb and desorb water vapour with a higher rate and they can bind more salt solution which is formed from solid salt crystals by water vapour absorption. Our results are important for packaging producers who thermoform films to cups and trays. This study addresses markets for fresh produce and other products with a high water activity.
Der moderne Karosseriebau ist geprägt durch den Wunsch nach einer schlanken Prozesskette, die sich durch hohe Prozesssicherheit auszeichnet. Im Umfeld der Fügetechnik rücken zur Erreichung dieses Ziels vermehrt sogenannte „unmittelbare Verbindungen“ in den Vordergrund. Hierbei handelt es sich um Fügeverbindungen, zu deren Erzeugung keine zusätzlichen Verbindungsmittel wie Schrauben oder Niete bereitgestellt werden müssen. Daher werden spezielle Schnappelemente für den Karosseriebau entwickelt, die als integraler Bestandteil aus dem Fügeteil ausgeformt werden. Durch den Einsatz derartiger Schnappelemente lässt sich die Teilevielfalt signifikant reduzieren. Das Fügen derartiger Teile erfolgt hierbei mit geringstem Zeitaufwand und nur mit der ohnehin zur Zuführung des Fügeteils benötigten Handhabungsvorrichtung.
Die assistierte Querführung wie das Spurhalteassistenzsystem ist ein Schlüssel zur erfolgreichen Einführung des hochautomatisierten Fahrens. Was empfindet der Kunde beim Einsatz von Spurhalteassistenzsystemen, und welche psychischen und physischen Belastungen lösen die verschiedenen Fahrsituationen aus? Welche Erwartungen hat er an das Fahrerlebnis? Was wird als angenehm und unangenehm empfunden, was wird akzeptiert, und welche Attribute sind inakzeptabel? Die Hochschule Kempten und MdynamiX sind diesen Fragen in breit angelegten Studien mit insgesamt 120 Probanden im Realeinsatz nachgegangen.
Support prospect of success in mathematics for first-year students in engineering by early feedback
(2020)
Providing students with the necessary mathematical skills is a growing challenge in German engineering degree courses. This is due to manifold mostly pre-university reasons, for example, inadequate or heterogeneous secondary education in Germany. Preparatory courses, a common remedy offered by many universities, often turn out to lack the expected effect. However, implying an early, mandatory test that scans the basic mathematical skills defined as entrance standard, showed positive results, as it detects the individual knowledge gaps of first-year students and motivates them to take action. For this purpose, we coupled the test with detailed, individual feedback and a cluster of affiliated support offers - preparatory to the test as well as attendant to the first year. Being mandatory, the test already pushes more students in our preparatory math courses. Whereas its detailed, individual feedback enables students to choose among the subsequent support offers and to cope with remaining gaps. The support offers range from transition workshops, co-learning tutorials, an online exercise platform, video tutorials up to conventional worksheets and consultation hours. This setup of mandatory test, early and detailed feedback and versatile supporting offers, tackling the missing skills, significantly increased the success in the basic mathematics and mathematics dependent modules of our engineering bachelor courses. In the process, this setup generates several additional, statistical outcomes, like a rating of the different German pre-university school systems, which helps to further work on measures dealing with the decreasing skills of beginners.
Church bells are exposed to severe loading conditions during ringing, which results in different damage modes due to material wear, fatigue loading, material deficiencies, different clapper-to-bell layouts, etc. As part of the activities of an EU-funded project called Maintenance and Protection of Bells (PROBELL), experimental investigations and finite-element simulations of the local contact between the clapper and the bell were carried out to study the wear-related damage to bells. First a simplified model was built to assess under the laboratory-controlled conditions the consequences of the repetitive impacts between a spherical body made from steel and a flat block made from bronze. After the results of the finite-element simulations for a simplified model were in reasonable agreement with the measured data a full-scale finite-element model for simulating the repetitive clapper-to-bell strokes was built. The simulations with the full-scale model were performed for variations of the parameters that influence the structural behaviour of the bell and the clapper: the clapper material, the clapper mass, the relative impact velocity of the clapper, the shape of the clapper, the clapper's pin support, the clapper's impact angle, the clapper's guide accuracy, the bell's sound-burp thickness and the coefficient of friction between the clapper and the bell. The agreement between the simulated and the measured results and the relation between the local stress–strain state and the damage to the bell in the contact area are discussed.
To investigate the combustion and emission behavior of straight vegetable oils (SVO), jatropha oil, soybean oil, and diesel fuel were tested. For this research, a 2.2L common-rail engine with a two-stage turbocharging concept was equipped with a cylinder pressure indication system, an exhaust-gas analyzer, an AVL Micro Soot sensor and a Scanning Mobility Particle Sizer 3936 (SMPS) device to detect the particle-size-distribution (PSD). At a low- and mid-load engine-operating point (EOP), the thermodynamic and emissions were investigated under various exhaust gas recirculation (EGR) rates with respect to the PSD. Moreover, the injection behavior of the three test fuels was analyzed separately using an injection rate analyzer. This procedure facilitates the thermodynamic investigations of the engine process and allows the calculation of the hydraulic delay (HD) as well as the ignition delay (ID). The ID of the SVO fuels compared to diesel fuel was found to be lower at all engine-operating modes, while jatropha oil always showed the shortest ID. In the particulate-nitrogen oxide (NOX) trade-off, the SVO fuels showed higher particulate matter (PM) emissions at the low-load EOP, whereas the PM emissions of diesel fuel overtop the SVO fuels at a higher engine load. With increased EGR-rates, a rise in the particle size was observed for all fuels. At the low-load EOP, the SVO fuels showed larger particles for high EGR-rates. This effect also changed by increasing the engine-load to the mid-load EOP, wherein the particle size of the diesel fuel emissions is higher by applying elevated EGR-rates.
A scanning Kerr microscope with a temporal resolution of <230 fs and a spatial resolution of 210 nm is presented. Equipped with a large temporal and spatial scanning range of 8 ns and 320 μm, respectively, the microscope allows studying nonuniform magnetization dynamics on many different time scales over a large area. For demonstration, we study the magnetization dynamics in Fe/Gd multilayer dot arrays exhibiting a spin reorientation transition (SRT) on three different time scales, namely, femtosecond, picosecond, and nanosecond scales. The dynamics on all time scales varies from one dot to another. This is attributed to the high sensitivity of the SRT to the variations of the layer thicknesses and the Fe/Gd interface structure.
The oxygen permeability of films is relevant for packaging related and technical applications. An increasingly used test method for the measurement of oxygen permeability is the optical test method, because it allows a simple and cost-efficient measurement setup. This method is based on optical chemical sensors. However, not much is known about its validity. Therefore, method validation is necessary which is subject of this study. The optical method is compared with the carrier gas method for a variety of film samples. In the tested permeability range of 0.5–2500 cm3 (STP)·(m2 d bar)−1 both methods deviated less than 20% for zero and 50% relative humidity.
Oxygen scavengers are used in food packaging to protect oxygen-sensitive food products. A mixture of gallic acid (GA) and sodium carbonate was used as an oxygen scavenger (OSc) in bio-based multilayer packaging films produced in a three-step process: compounding, flat film extrusion, and lamination. We investigated the film surface color as well as oxygen absorption at different relative humidities (RHs) and temperatures, and compared the oxygen absorption of OSc powder, monolayer films, and multilayer films. The films were initially brownish-red in color but changed to greenish-black during oxygen absorption under humid conditions. We observed a maximum absorption capacity of 447 mg O2/g GA at 21 °C and 100% RH. The incorporation of GA into a polymer matrix reduced the rate of oxygen absorption compared to the GA powder because the polymer acted as a barrier to oxygen and water vapor diffusion. As expected, the temperature had a significant effect on the initial absorption rate of the multilayer films; the corresponding activation energy was 75.4 kJ/mol. Higher RH significantly increased the oxygen absorption rate. These results demonstrate for the first time the production and the properties of a bio-based multilayer packaging film with GA as the oxygen scavenger. Potential applications include the packaging of food products with high water activity (aw > 0.86).
Water loss, gain or transfer results in a decline in the overall quality of food. The aim of this study was to form a uniform layer of sodium alginate-based edible coating (1.25% sodium alginate, 2% glycerol, 0.2% sunflower oil, 1% span 80, 0.2% tween 80, (w/w)) and investigate the effects on the water barrier characteristics of fresh-cut cantaloupe and strawberries. To this end, a uniform and continuous edible film formation was achieved (0.187 ± 0.076 mm and 0.235 ± 0.077 mm for cantaloupe and strawberries, respectively) with an additional immersion step into a calcium solution at the very beginning of the coating process. The coating application was effective in significantly reducing the water loss (%) of the cantaloupe pieces. However, no significant effect was observed in water vapor resistance results and weight change measurements in a climate chamber (80%→60% relative humidity (RH) at 10 °C). External packaging conditions (i.e., closed, perforated, and open) were not significantly effective on water activity (aw) values of cantaloupe, but were effective for strawberry values. In general, the coating application promoted the water loss of strawberry samples. Additionally, the water vapor transmission rate of stand-alone films was determined (2131 g·100 µm/(m2·d·bar) under constant environmental conditions (23 °C, 100%→50% RH) due to the ability to also evaluate the efficacy in ideal conditions.
Achieving high quality of a coated food product is mostly dependent on the characteristics of the food material to be coated, the properties of the components in the coating solution, and the obtained coating material. In the present study, usability and effectiveness of various components as well as their concentrations were assessed to produce an effective coating material. For this purpose, different concentrations of gelling agent (sodium alginate 0–3.5%, w/w), plasticizers (glycerol and sorbitol (0–20%, w/w), surfactants (tween 40, tween 80, span 60, span 80, lecithin (0–5%, w/w), and vegetable oils (sunflower oil, olive oil, rapeseed oil (0–5%, w/w) were used to prepare edible coating solutions. Formulations were built gradually, and characteristics of coatings were evaluated by analyzing surface tension values and its polar and dispersive components, emulsion droplet size, and optical appearance in microscopic scale. The results obtained showed that 1.25% sodium alginate, 2% glycerol, 0.2% sunflower oil, 1% span 80, and 0.2% tween 40 or tween 80 can be used in formulation to obtain an effective coating for hydrophobic food surfaces. Three formulations were designed, and their stability (emulsion droplet size, optical characteristics, and creaming index) and wettability tests on strawberry showed that they could be successfully used in coating applications
The water vapour transmission rate (WVTR) of packaging materials and edible coatings is one of their critical parameters for the shelf life of many food products. The water vapour transmission rates of flat bodies such as films are determined by permeation measurements which are a steady-state method. Another method is based on water vapour sorption measurements which is a non-steady-state method. It can be used only for mono-material flat bodies. It allows using smaller sample areas compared to permeation measurements. However, not much is known about how well both methods correlate with each other. Therefore, the aim of this study was to compare the WVTR results of different materials determined by both methods. The results of both methods differed by up to factor of three, measured at identical samples. In a few cases the difference was up to factor five. The exact reasons for these differences are unknown. Nonetheless, the water vapour sorption method is a suitable method to determine the magnitue of order of the water vapour transmission rate but not its exact value.
For “on board” diagnosis purposes of the injected fuel quantity flow sensitive elements based on the thermo-resistive measurement principle were integrated into finished Common Rail injection nozzles of valve-covered orifice (VCO) or mini-sac hole (MSH) class. Electron-discharge machining as well as electron beam welding technique are key technologies for a reliable integration procedure. To demonstrate negligible influence on the hydraulic performance of the nozzle after modification an optical measurement set-up is used to record temporally resolved the propagation of the spray patterns ejected from the six injection holes simultaneously. From these investigations the impact on the structural distortion of the valve caused by the welding seam is proved as its position can be directly linked to any chances in spray performance of each individual injection hole. Reducing the energy input during the electron beam welding lowers substantially the asymmetry in spray patterns from hole to hole as the needle uncovers the six injection holes more symmetrically. Besides this important finding, the numerical calculations indicate that the implementation of the sensor chip slightly amplifies the asymmetry induced by the welding process due to an additional weakening of the nozzle body which is confirmed experimentally. Despite these challenges, however, it is demonstrated that appropriate parameters for the integration procedure can be found affecting the hydraulic performance negligible compared to the original state.
Alginate is a naturally occurring polysaccharide used in the bio industry. It is mainly derived from brown algae species. Alginate-based edible coatings and films attract interest for improving/maintaining quality and extending the shelf-life of fruit, vegetable, meat, poultry, seafood, and cheese by reducing dehydration (as sacrificial moisture agent), controlling respiration, enhancing product appearance, improving mechanical properties, etc. This paper reviews the most recent essential information about alginate-based edible coatings. The categorization of alginate-based coatings/film in food packaging concept is formed gradually with the explanation of the most important titles. Emphasis will be placed on active ingredients incorporated into alginate-based formulations, edible coating/film application methods, research and development studies of coated food products and mass transfer and barrier characteristics of the alginate-based coatings/films. Future trends are also reviewed to identify research gaps and recommend new research areas. The summarized information presented in this article will enable researchers to thoroughly understand the fundamentals of the coating process and to develop alginate-based edible films and coatings more readily.
Edible coating based on sodium alginate solution was applied to fresh‐cut cantaloupe melon by dipping and vacuum impregnation coating methods. One aim of this work is to produce more technical information concerning these conventional and novel coating processes. For this purpose, the effect of various coating parameters (dipping time, draining time, time length of the vacuum period, vacuum pressure, atmospheric restoration time) with several levels on physical quality parameters (percentage of weight gain, color, and texture) of noncoated and coated samples were determined in order to define adequate coating process parameters to achieve a successful coating application. Additionally, the effects of dipping and vacuum impregnation processes were compared. Both processes improved the firmness of the melon pieces. However, vacuum impregnation application had higher firmness and weight gain results, and had significant effect (P < 0.05) on color (lower luminosity, higher redness, yellowness, and chroma values). Experimental results affirm that vacuum impregnation method can be used successively to improve mechanical and structural properties of food products.
Friction surfacing offers a means of producing coatings between dissimilar materials through a solid state process; a union that would otherwise be classed as incompatible for liquid state coating processes. A method of using a rotating consumable friction rod supplemented by inductive heating was employed to produce conditions necessary for a sound bond between a stainless steel coating and an aluminium substrate. The rotational speed of and load on the coating rod influenced the bond strength significantly with low rotational speeds and high load values producing a good bond quality; however, cavitations at the coating-substrate interface showed a detrimental effect on the bond quality. Mechanical interlocking could be identified from images of longitudinal cross-sectional slices which were recorded using optical microscopy. An image recognition software tool was used to generate an interfacial roughness profile graph which described the coating-substrate interface. Additional filtering of the profile graph showed the depth of mechanical interlocking of the stainless steel coating into the aluminium substrate with the degree of this interlocking quantified by roughness values calculated from the profile graph. Large roughness values can be related to high coating push-off strengths (up to 107 MPa), and also were a result of low rotational speeds and high load values during friction surfacing. Dovetail shaped mechanical interlocks identified in the profile produced both high push-off and shear strength when compared with wedge-shaped interlocks; which, overall, provided good shear strengths up to 126 MPa.
Inductive heating effects on friction surfacing of stainless steel onto an aluminium substrate
(2015)
An experimental setup was designed to compare the principal process parametric relationships with the classical approach to friction surfacing with the addition of inductive heating. The production of the flash is described quantitatively and its influence on coating geometry and mass is presented. It was found that the coating mass and thickness decreased for an increase in the rotational speed of the consumable rod; the amount of flash produced by the consumable rod also increased. However, the effect of an increase in this rod contact pressure on the coating thickness is insignificant, whilst the coating mass decreases with rising pressure and the coating width increases coupled with an increase in flash production. Cross sections showed good bonding quality and mechanical interlocking at the bond interface. The substrate-coating interface showed a varying degree of mechanical interlocking and the presence of cavitations. Bond strength values applying shear and push-off testing of up to 106 MPa and 96 MPa, respectively, could be identified.
Friction surfaced specimens produced by the application of inductive heating and utilising a flash-reducing tool were compared with those obtained through the classical approach. It was found that the use of inductive heating resulted in an increased consumption of the coating material; however, the push-off strength could be more than doubled when compared with the classical process with high shear strength values of up to 111 MPa. The application of the flash-reducing tool reduced the flash to less than 0.05% of the material deposited as a coating and manifested itself in the form of small chips. High push-off strength values of up to 135 MPa were observed, accompanied by an increased coating thickness, coating width and bonding area. Temperature measurements with thermocouples taken during the coating process showed that the melting temperature of the aluminium substrate was reached at the substrate–coating interface. Mixed mode failure was evident at the fractured surfaces of the push-off test specimens and mechanical interlocking appears to be a main bonding mechanism. The presence of cavities were shown to have a detrimental effect on the bonding integrity, but could be reduced in size and number by the application of the flash-reducing tool.
High fogging is a power augmentation device where water is sprayed upstream of the compressor inlet with higher mass flow than that which would be needed to saturate the intake air. The main focus of this paper is on applications of high fogging on the ALSTOM gas turbine engines of the family GT24/GT26. Engine operation and performance are illustrated based on test results obtained from four different engines that have meanwhile accumulated more than 12,000 operating hours (OH) in commercial operation with ALSTOM’s ALFog® high fogging system. The effect of internal cooling (water evaporation inside the compressor) is investigated considering actual compressor boundaries matched within the complete engine. Changes in the secondary air system (SAS) and corresponding movement of the engine operating line have been taken into account. Power output gain as high as 7.1% was experimentally demonstrated for injected water mass fraction (f=mH2O∕mair) equal to 1% and considering internal cooling effects only. Higher figures can be obtained for operation at low ambient relative humidity and partial evaporation upstream of the compressor inlet.
Joining sheet metal can be problematic using traditional friction welding techniques. Friction crush welding (FCW) offers a high speed process which requires a simple edge preparation and can be applied to out-of-plane geometries. In this work, an implementation of FCW was employed using an additional wire to weld sheets of EN AW5754 H22, DC01, and Cu-DHP. The joint is formed by bringing together two sheet metal parts, introducing a wire into the weld zone and employing a rotating disk which is subject to an external force. The requirements of the welding preparation and the fundamental process variables are shown. Thermal measurements were taken which give evidence about the maximum temperature in the welding center and the temperature in the periphery of the sheet metals being joined. The high welding speed along with a relatively low heat input results in a minimal distortion of the sheet metal and marginal metallurgical changes in the parent material. In the steel specimens, this FCW implementation produces a fine grain microstructure, enhancing mechanical properties in the region of the weld. Aluminum and copper produced mean bond strengths of 77 and 69 pct to that of the parent material, respectively, whilst the steel demonstrated a strength of 98 pct. Using a wire offers the opportunity to use a higher-alloyed additional material and to precisely adjust the additional material volume appropriate for a given material alignment and thickness.
Large arrays of ordered magnetic nanostructures have been fabricated by sputter depositing Fe/Gd multilayers on an array of self-assembled nanospheres. On a planar substrate the system shows an in-plane magnetization whereas a spin reorientation transition (SRT) to out-of-plane orientation occurs on the spherules. This SRT cannot only be explained by the reduction in the shape anisotropy due to patterning of the extended film into nanometer sized islands. In fact, more important is the curved surface of the film on the nanocaps. Micromagnetic simulations of various geometries reveal that the crescent shape of the magnetic film on the spheres is ideal to get small values of the shape anisotropy for all diameters of the spheres, ranging from 1 μm down to 20 nm. The observed SRT enables a simple and cost effective bottom-up approach to produce patterned perpendicular magnetic nanostructures, having a high potential for magnetic data storage and spintronic applications.
For a further optimization of the automotive power train of diesel engines, advanced combustion processes require a highly flexible injection system, provided e.g., by the Common Rail (CR) injection technique. In the past, the feasibility to implement in the injection nozzle injection quantity sensors based on a thermo-resistive measurement principle has been demonstrated up to injection pressures of 135 MPa (1350 bar). Due to a very complex integration procedure a less-costly implementation is realized in the range of the high-pressure pipe connecting each single injector with the common pressure reservoir. The sensor output signals measured at this location of the hydraulic system are compared to those obtained from the nozzle as well as from an injection amount indicator used as standard reference method. Finally, hydraulic simulations on system level are performed showing a good correspondence in respect to the onset of fuel flow and to the period of pressure oscillations generated in the hydraulic system after termination of the drive pulse.
The aim of this study was to evaluate the influence of relative humidity (RH) on the oxygen permeability and water vapour transmission rate (WVTR) of whey protein coated Polyethylene terephthalate (PET) or whey protein monolayer films. Furthermore, the activation energies for the permeability of oxygen, carbon dioxide and nitrogen as well as the permselectivities under different set of temperatures were measured. The results showed that the permeability values through the whey protein coating and whey protein film increased with increasing RH. The water vapour permeability measured at 50% RH of (9.3 ± 0.6)−10 cm3 (STP) cm cm−2 s−1 Pa−1 increased to (16.2 ± 0.9)−10 cm3 (STP) cm cm−2 s−1 Pa−1 at 85% RH. An increase in temperature showed an expected increase of the permeability in both uncoated PET and the whey protein monolayer. The permselectivity of whey protein film was determined and the calculated ratios of the permselectivity (P(N2)/P(O2)/P(CO2):1/(4–6/(34–35)) differed from the simplified ratios given in the literature (P(N2)/P(O2)/P(CO2):1/4/16). Furthermore the calculated activation energy values for whey (51 kJ mol−1) were in agreement with other studies.
This study investigates chemical grafting with fatty acid chlorides as a method for the surface modification of hydrophilic web materials. The resulting changes in the water repellence and barrier properties were studied. For this purpose, different grades of polyvinyl alcohol (PVOH) were coated on regenerated cellulose films (“cellophane”) and paper and then grafted with fatty acid chlorides. The PVOH grades varied in their degree of hydrolysis and average molecular weight. The surface was esterified with two fatty acid chlorides, palmitoyl (C16) and stearoyl chloride (C18), by chemical grafting. The chemical grafting resulted in water-repellent surfaces and reduced water vapor transmission rates by a factor of almost 19. The impact of the surface modification was greater for a higher degree of hydrolysis of the polyvinyl alcohol and for shorter fatty acid chains. Although the water vapor barrier for palmitoyl-grafted PVOH was higher than for stearoyl-grafted PVOH, the contact angle with water was lower. Additionally, it was shown that a higher degree of hydrolysis led to higher water vapor barrier improvement factors after grafting. Furthermore, the oxygen permeability decreased after grafting significantly, due to the fact that the grafting protects the PVOH against humidity when the humidity is applied on the grafted side. It can be concluded that the carbon chain length of the fatty acid chlorides is the limiting factor for water vapor adsorption, but the grafting density is the bottleneck for water diffusing in the polymer.
Autonomous Vehicles (AVs) will soon be a reality on our roads. Up to now, their standard behaviour is predetermined since it is the result of programmed algorithms. Under risky traffic situations, however, they will face dilemmas such as, deciding between affecting the passenger or affecting others. Thus, in this experiment, we investigate how people solve a reframed version of the well-known Trolley-problem [Foot, P. 1967. “The problem of abortion and the doctrine of double effect,” Oxford Review 5: 5–15] under two conditions: when subjects actually drive a vehicle simulator, versus when they solve the same dilemma by programming a hypothetical AV. In both settings, the participants’ decisions have real monetary consequences, which affect others and themselves. Our Probit models indicate that subjects who program an AV and who are more cautious in terms of speed are less (more) likely to sacrifice a pedestrian (themselves) compared to those who actually drive and prefer a higher driving speed. Moreover, we find that the subjects’ choices are associated with risk aversion but not with moral beliefs or loss aversion. Implications of the driving vs programming discrepancies for the design of AVs algorithms are discussed.
The focus of this publication is on the development of lane-precise “Ground Truth” (GT) maps for the objective quality evaluation of automated driving functions. Therefore, attention is paid to the proper measurement of road geometry. The road geometry forms the basic layer of the HD maps.
A new map format Curved Regular Objects (CRO) is developed, which is based on the idea of OpenCRG®. For the evaluation of current Advanced Driver Assistance Systems (ADAS) an accurate High Definition (HD) maps as GT are necessary. This makes it possible to locate the high precision vehicle position and motion with centimeter accuracy. The aim is to achieve maximum accuracy of the absolute 3D positions when measuring lanes. This method for the generation of highly accurate GT maps promises an absolute accuracy of < ± 0.05 m. Various research activities benefit from the exact street reference at the Kempten University of Applied Sciences (UAS Kempten) in the Adrive Living Lab. First of all, the publication deals with the current Lane Keeping Assistant Systems (LKAS). The accuracy of the vehicle’s localization on the GT map and an objective evaluation of the LKAS is shown. In addition, the CRO data is used as a virtual sensor for the steering assistant in real time. Another application is the Visual Range Finder (VRF), which requires less computation power by using the CRO data. In addition, a current LKAS camera sensor performance is evaluated using CRO maps.
Fahrerassistenzsysteme und automatisiertes Fahren sind ein Megatrend in der Fahrzeugindustrie. Dabei stellen sich folgende Fragen: Können sich die Fahrzeughersteller auch noch in Zukunft markenspezifisch differenzieren, oder fahren alle Fahrzeuge gleich? Wie lässt sich eine Marken-DNA implementieren, und wie erzielt man den Übergang von Fahrspaß zum Spaß am Gefahrenwerden? Um Antworten zu generieren, sind klare Fahreigenschaftsziele "vor Kunde" und daraus die Anforderungen an die Fahrzeugsysteme und -komponenten abzuleiten. Aber was sind Fahreigenschaften im Kontext des assistierten und automatisierten Fahrens, und wie können diese in einer Entwicklung gezielt erreicht werden? Dieser Herausforderung hat sich Porsche gemeinsam mit der Hochschule für angewandte Wissenschaften Kempten und MdynamiX angenommen. Um die Eigenschaftsziele in allen Phasen der Entwicklung auf Gesamtfahrzeugebene validieren zu können, wurde eine modulare Simulationsumgebung, bestehend aus der Umfeldsimulation Vires VTD, Porsche-Fahrdynamikmodell und einem Reglersystemverbund inklusive Spurhalteregler aufgebaut. Die Co-Simulationsplattform AVL Model.Connect stellt dabei die Vernetzung der einzelnen Simulationen/Modelle dar und bietet entsprechende Funktionen, um diese durchgängig in den Verfahren Model in the Loop (MiL), Software in the Loop (SiL) und Hardware in the Loop (HiL) einzusetzen. Um die Spurführungsgüte, Fahrzeugreaktion und Fahrer-Fahrzeug-Interaktion realistisch abbilden zu können, ist ein gutes Lenkmodell mit Effekten im On-Center-Bereich notwendig.
Claim and Reality? Lane Keeping Assistant: the Conflict Between Expectation and Customer Experience
(2018)
In a current customer study with over 50 subjects, the customer wishes/acceptance of the Lane Keeping Assistance System were tested, evaluated and compared over 4000 km in a real road test. As a result, a considerable amount of potential can be seen for improvement in terms of customer acceptance for all three Lane Keeping Assistance Systems tested. The feeling of safety is the most important criterion, followed by the HMI and the edge guide. Furthermore, specific properties can be derived from the study, which must be fulfilled from the customer's point of view in order to fulfil the customer's wishes. There was a clear "GAP" between the degree to which the criteria were met and their importance. Only 27 % of customers would finally buy the LKAS on the basis of the product quality they have experienced. The results show that, in addition to differentiated expectations, there are primarily knowledge and experience-based deficits. Although a large part of the ADAS is known, only a few of the drivers surveyed have system expertise. Furthermore, it becomes clear from the questions according to Kano that, in addition to the pure transfer of knowledge, above all the subjective experience of the systems contributes to the enthusiasm of the users and to the increase in acceptance, provided that the first contact with the Lane Keeping Assistance represents a successful experience. Therefore, more attention should be paid to the capabilities and needs of end-users when designing vehicles. ADAS have the potential to counteract people's performance limitations, to support you where people reach their limits. However, only under the condition that they find acceptance in the target group and are used safely. The system is only used if it has the system behavior expected by the driver and he can therefore trust the system. Arndt also points out that too little confidence in ADAS means that it is not used. However, in the same context, she stresses that too much confidence can tempt the driver into relying too much on the ADAS, leading to system abuse. In addition to technical feasibility, knowledge of the requirements, needs and wishes of drivers is indispensable for their acceptance and use. Therefore, the recommendation to automotive manufacturers and suppliers is to involve various user groups in the product development process as early as possible, for example using the QFD method. In this way, ADAS are developed that meet the expectations of the customers. Especially the emotional comfort experience of the users, like lack of system trust, fear of negligence, distraction, paternalism and loss of control, will gain importance with increasing degree of automation. In order to lay the foundation for the acceptance of current developments in the field of highly automated and autonomous driving, drivers must develop a comprehensive system understanding and trust in comparison with today's ADAS of level 2 functions. Acceptance and trust in ADAS depends largely on a suitable and transparent human-machine interface. This theory has been also proven in this study. The customer wants to be informed about the current status of the system at any time during the journey via an understandable display concept and to be clear. He wants a predictable system that gives him enough time to intervene in the event of a system crash due to system limitations. In current systems, the warning comes - if at all - at the time of the drop. The driver has often already crossed the lane limit. Taking human situational awareness into account, such a short-term warning is critical. In addition, users' expectations for a Lane Keeping Assistance System do not always match the system's functionalities. According to the participants, the current system design does not offer any added value, as the driver must be ready to intervene at all times. This means that the driver not only has the task of checking himself for his primary task of driving, but must also monitor the availability of the system and prepare himself for unforeseen, in some cases also unforeseen drops off of the system. Since human hands over control to the vehicle, trust and the associated acceptance plays a central role. Ultimately the break-out of automated driving will decide on customer acceptance. "If only the engineer realizes the differences and understands the system, the customer has no benefit". The findings of the study show that in ADAS/AD development, the human being, or rather the customer should be placed much more at the center of development. Furthermore, it is necessary to focus on driving attributes and the driving experience in the sense of an attribute-based development.
Advanced Driver Assistance Systems (ADAS) warn, inform and perform monotonous tasks so that the strain on the driver's side is greatly reduced. They should lead to a further increase in customer mobility through greater comfort, efficiency and safety. As far as the theory goes - in practice, the comfort benefits addressed by the customer are not evident with all driver assistance systems. A previous study of the Lane Keeping Assistance System (LKAS) at Kempten University has shown that the physiological stress and perceived stress of the subjects using the LKAS during a test drive are significantly higher than if the same person refrains from using it. This finding clearly shows that the product "still" misses the purpose of comfort gain through relief. As a result, customer acceptance is very moderate. The motivation of this study was to identify requirements for the LKAS from the customer's point of view, to measure the degree of fulfilment in a competitive comparison and to learn from the customer assessments overall. By implementing these features, customer satisfaction with the LKAS is to be increased. The feeling of strain should lead to relief and consequently to an increase in the customer's acceptance of the product. Switching off or deactivating the system and the resulting increased safety risk should no longer occur in the future. The customer's wishes should be recognizable in the product specifications.
Validation of X-in-the-Loop Approaches for Virtual Homologation of Automated Driving Functions
(2018)
Securing and homologating automated driving functions presents a huge challenge for their market introduction due to an enormous number of scenarios and environment parameter combinations. Confronting conventional real world tests with the new challenges of automated driving is not feasible anymore and yields to a virtualization of the testing methods by means of X-in-the-Loop approaches. Since their validity is a key enabler for virtual homologation, this paper focuses on the validation of X-in-the-Loop approaches. A generic validation methodology is introduced and demonstrated for the specific use case of an automated longitudinal driving function. As a proof of concept equal scenarios are performed in real driving tests as reference and in two X-in-the-Loop approaches based on a test bed resp. a purely virtual co-simulation environment. The paper describes how a consistent implementation can be ensured to evaluate the collected data. First results show a promising correlation regarding multiple repetitions on the test bed and regarding the validation of both X-in-the-Loop approaches for a future virtual homologation of automated driving functions.
Advanced driver assistance systems (ADAS) of longitudinal control are widely used. In contrast to longitudinal controls, lateral controls are a growing market since this technique plays a major role in a successful introduction of automated driving. Customer and benchmark studies conducted by theUniversity of Applied Sciences Kempten and Consline AG have clearly shown that the vehicle behavior and customer experience such as tracking performance, driver-vehicle interaction, availability, degree of stress and the sense of security of today's lane keeping assistance systems are consistently rated as extremely unsatisfactory. As a consequence, there is a moderate level of trust and low customer acceptance. A new measuring method based on high-precision and accurate digital maps (ground truth) was developed. With this method, analysis of the entire chain of action, from sensor to tracking is possible. Position, direction and motion of the vehicle and its reference distance to road markings can be precisely measured in the digital map using a high-precision inertial measurement system (IMU) with RTK-DGPS and SAPOS correction service. The measuring method can be used in particular on public routes, since test areas are still insufficient due to the very small tracks and driving maneuver variations for lane keeping assistance systems. For a precise assessment of the sensor, planning and control performance as well as the overall driving characteristics, a very precise knowledge of the routes and the route excitation is required. For this purpose, high precision and accurate digital maps (ground truth) of real tracks were generated. A roof mounted stereo camera system combined with an RTK-DGPS IMU was used to provide offline-generated digital maps with high precision in the OpenDRIVE or OpenStreetMap format, as well as other common simulation formats like IPG CarMaker. In order to be able to carry out the dynamic driving evaluation as well as the simultaneous evaluation of the sensor, planning and control performance in the digital maps in real time, a route format with a regular grid, based on OpenCRG (Curved Regular Grid), was further developed. An IMU with RTK-DGPS and correction service (e.g. SAPOS) provides in real time the highly accurate position, direction and movement of the ego vehicle of up to two centimeters in the lateral and longitudinal direction. In addition, a special measuring steering wheel was built to objectify the driver-vehicle interaction, in particular the steering torque curve and the tracking. Particular attention was paid to the reuse of the original steering wheel with all functions, such as airbag, operation and hands-off detection. The novelty is the ability to measure the recognition, planning and control performance of environmental sensors, algorithms and controllers compared to the reference "Ground Truth". In addition, the driving characteristics of the entire vehicle can be assessed in terms of its tracking performance, driver-vehicle interaction, availability, degree of relieving and a sense of security. Another novelty is the consistent use of digital maps in driving tests as well as in the MIL / SIL / HIL simulation as a digital twin.
In a recent study with N = 50 subjects, the lane keeping assistant was tested on more than 3,500 km on public roads in the Allgäu. To test the various settings of the lane keeping assistant, different conditions were tested: 120km/h versus 160km/h as well as with versus without lane keeping assistant. The evaluation of the criteria for lane keeping assistant, such as edge management and degree of relief show a significant relationship with the experienced workload. The increased workload as well as stress when using the lane keeping assistant system could be detected and proved subjectively as well as with physiological measuring devices. The significantly higher stress experienced with the use of the lane keeping assistant system shows the immense importance that the further research on this system has.
Simulation methods supporting homologation of Electronic Stability Control in vehicle variants
(2017)
Vehicle simulation has a long tradition in the automotive industry as a powerful supplement to physical vehicle testing. In the field of Electronic Stability Control (ESC) system, the simulation process has been well established to support the ESC development and application by suppliers and Original Equipment Manufacturers (OEMs). The latest regulation of the United Nations Economic Commission for Europe UN/ECE-R 13 allows also for simulation-based homologation. This extends the usage of simulation from ESC development to homologation. This paper gives an overview of simulation methods, as well as processes and tools used for the homologation of ESC in vehicle variants. The paper first describes the generic homologation process according to the European Regulation (UN/ECE-R 13H, UN/ECE-R 13/11) and U.S. Federal Motor Vehicle Safety Standard (FMVSS 126). Subsequently the ESC system is explained as well as the generic application and release process at the supplier and OEM side. Coming up with the simulation methods, the ESC development and application process needs to be adapted for the virtual vehicles. The simulation environment, consisting of vehicle model, ESC model and simulation platform, is explained in detail with some exemplary use-cases. In the final section, examples of simulation-based ESC homologation in vehicle variants are shown for passenger cars, light trucks, heavy trucks and trailers. This paper is targeted to give a state-of-the-art account of the simulation methods supporting the homologation of ESC systems in vehicle variants. However, the described approach and the lessons learned can be used as reference in future for an extended usage of simulation-supported releases of the ESC system up to the development and release of driver assistance systems.
Die Integration fluktuierender erneuerbarer Energien erfordert hoch flexible Kraftwerke, Energiespeicher und Power-to-X-Anlagen zur Netzstabilisierung und bedarfsgerechten Abdeckung der verbleibenden Netzlasten.
Im Projekt KWK-Flex untersucht die Hochschule Kempten mit den Partnern Fernwärme Ulm GmbH (FUG) aus Baden-Württemberg und der ZAK Energie GmbH (ZAK) aus Bayern die Entwicklung innovativer Methoden und Anlagenbetriebsstrategien zur flexiblen, stromgeführten Fahrweise von Kraft-Wärme-Kopplungs-(KWK)-Anlagen mit hohen Anteilen erneuerbarer Energien.
Die Analysen wurden unterstützt von der AGFW | Der Energieeffizienzverband für Wärme, Kälte und KWK e.V.
The hydrocarbons present in the diesel exhaust gas are analyzed. A mass spectrometer is used for the measurements, and it operates on the basis of an ion‐molecule reaction. This method is especially suitable because it is selective, is as free of fragments as possible, and is highly sensitive to the species that need to be measured. The study shows that numerous hydrocarbons in diesel exhaust gas can be identified. In particular, three molecules, ethyne, ethene and propene, were analyzed online in‐depth on an engine test bench under different engine operating conditions.
The variety of products on the market that are offered with advanced driver assistance systems is huge. Besides systems like the lane keeping assistant also camera based systems are more and more in the foreground. The Full Display Mirror (FDM), a camera-based hybrid mirror, is also being installed in vehicles. User experience in the sense of acceptance and peace of mind as well as benefit of the product are essential not only to know the systems are installed, but also to know how to use them. In a customer study with N = 60 persons, interviews and questionnaires were conducted during a test drive in real road traffic with various scenarios in order to test and evaluate the FDM. In comparison to the normal mirror, the FDM scored very well - especially in the field of view, the feedback was extremely positive. The increased safety with the use of the system, among other things due to the considerably larger field of view, is an absolute plus point of this camera-based mirror version. The fast familiarization with the system as well as the high user friendliness make the FDM a meaningful invention.
Advanced Driver Assistance Systems and Automated Driving are a megatrend in the automotive industry. The following questions arise: Will vehicle manufacturers still be able to differentiate themselves “brand-specifically” in the future or will all vehicles be perceived the same when being driven? How can a brand DNA be implemented and how can the transfer of “fun to drive” to “fun to be driven” be achieved? In order to reach this, clear driving characteristic goals – in front of the customer – should be defined and the requirements for vehicle systems and components shall be derived from this. However, what are driving characteristics in the context of assisted and automated driving, Figure 1, and how can those specifically be achieved in the development? Porsche has addressed this question together with the University of Applied Sciences Kempten and MdynamiX. How can an attribute-based development look like and how can Porsche effectively design a brand-typical characteristic in this area?
Advanced driver assistance systems (ADAS) support the driver in certain traffic situations and can increase road safety. For this appropriate interaction, concepts between the driver and the assistance systems are required, which focuses on driver’s needs. In a user-centered study with N = 48 subjects, interviews and questionnaires were conducted during a test drive in real road traffic in order to test and evaluate the lane keeping assistant system (LKAS) with head-up display (HUD). In addition, two current premium vehicles from various manufacturers were used to investigate the influence of the HUD on the user experience and to derive optimization potential for current and future automatic driving functions. In comparison to the test rides with LKAS in combination without HUD (with head-down display), it can be determined that there is a positive influence of HUD on the experience with LKAS.
Advanced Driver Assistance Systems (ADAS) and Highly Automated Driving Systems (HAD) are among the most important megatrends in the automotive development. Accompanying this one big question arises: do all assisted and automated driving cars drive the same or will vehicle manufacturers be able to differentiate themselves with DNA of their own? And - especially for a sportscar-manufacturer like Porsche – how can ADAS and HAD impart typical attributes like driving fun and sportiness, Figure 1? In order to achieve this, clear driving characteristic goals (from a customer’s point of view) must be defined and the system requirements for ADAS and HAD (including all components like sensors, ECU’s and actors) shall be derived from this. However, what are driving and brand characteristics in the context of assisted and automated driving? And how can those be realized in the development? Porsche has addressed this question together with the University of Applied Sciences Kempten and MdynamiX.
From an engineering point of view, church bells are structures that, during ringing, are exposed to severe loading conditions. They are damaged due to material wear, fatigue loading, material deficiencies, different clapper-to-bell layouts, ringing conditions, etc. To get an insight into the wear-related damage of bells, experimental investigations and numerical simulations of the local contact between the clapper and the bell were carried out as part of the activities of an EU-funded project called Maintenance and Protection of Bells. In order to make a full-scale comparison between the measured and simulated results a simplified model was set up. In this model the clapper was replaced by a cylinder with a rounded tip that was dropped against a block representing the bell wall. The aim of the simplified model was to study the impact phenomenon in a controlled way and to adapt the numerical model for simulating the local contact. In the article the synthesis of a finite-element model for simulating the cylinder-drop test is presented. The results of the finite-element simulations of repetitive cylinder drops are compared to the data that were measured in the laboratory. The effects of the cylinder material, the cylinder radius and the drop height of the cylinder on the local elastic–plastic behaviour of the cylinder and the block are also presented and discussed.