Universität Stuttgart
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Item Open Access Modeling and timing analysis of micro-ROS application on an off-road vehicle control unit(2022) Bappanadu, Suraj RaoROS is known to be the most popular middleware for the development of software in modern day robots. It's next version, ROS 2 is highly modular and offers flexibility by supporting on microprocessors running desktop operating systems. Micro-ROS puts the major ROS 2 features on microcontrollers, i.e., highly resource-constrained computing devices running specialized real-time operating systems. ROS 2 is also of great importance for other domains, including autonomous driving and the off-road sector. Accordingly, there is significant interest in bringing micro-ROS to typical automotive control units. These embedded platforms support AUTOSAR Classic OSEK-like operating system which is very different in many aspects when compared to the platforms supported by micro-ROS. Some of the aspects have already been addressed in a previous work. This thesis mainly focuses on mapping the micro-ROS execution scheme to AUTOSAR scheme and dynamic memory management of the micro-ROS stack. From the micro-ROS architecture perspective, to successfully port the stack on an AUTOSAR-based ECU, the middleware and other layers of the stack are also analysed and adapted using a standard approach to support tasks-like execution model instead of threads-like execution model. Additionally, the support for standard CAN protocol based on custom transport configuration with the hardware CAN on the BODAS ECU is introduced. Model-based development methods have proven their utility in automotive industry. Therefore, we also focus on describing the timing properties of the micro-ROS stack in a model-based approach. We develop a generic model which is independent of a specific modeling language. In the next step, we realize the generic model using the widely used AMALTHEA language and analyse how well the developed model predicts the timing behavior of micro-ROS tasks. Finally, the effectiveness of the approach regarding timing and modeling is demonstrated with a micro-ROS test application first on Linux and then on the off-road vehicle control unit BODAS RC18-12/40 by Bosch Rexroth.Item Open Access Interdisciplinary composition of E-Learning platforms based on reusable low-code adapters(2022) Meißner, NiklasElectronic Learning (E-Learning) platforms or Learning Management Systems (LMSs) are becoming increasingly popular and, accordingly, are being used more and more by teachers at schools and university professors. They are used to digitally distribute educational material to students and provide the opportunity to, e.g., upload and collect assignments, solve tasks, and view grades. LMSs have been growing in popularity and are used alongside in-person lectures as an adjunct to self-study. Due to digital teaching during the COVID-19 pandemic, LMSs have increased in importance significantly. Even in after-pandemic times, with returning in-person lectures, it is hard to imagine teaching at universities without these platforms. The possibilities of working with the established LMSs are enormous. However, a closer look also reveals some negative aspects that were not considered in developing and using these platforms. The existing LMSs lack individualization for lecturers of their courses and a motivating design for students. Plugins attempt to remedy this, but they are complex and time-consuming to use. Thus, the underlying problems are, on the one hand, that lecturers are limited in the design of their courses and, on the other hand, that students experience disadvantages in terms of motivation and interactivity. This thesis aims to develop a concept for an e-learning platform that addresses these problems, supports lecturers in designing their courses, and motivates and assists students in learning. Under the aspect of generalization, a concept for a Software Product Line (SPL) was developed for the requirements of a wide variety of study programs, providing lecturers with a base platform and enabling them to use low-code adapters to design and modify their courses. In addition, the platform and a support team will assist lecturers in using the LMS and creating educational material. For the conceptual design of the LMS, some already existing solutions and approaches were examined to address a similar problem. However, similar problems have been insufficiently solved or overlap with the problem statement of this thesis only to a limited extent. After a requirements analysis, the requirements were gathered and listed so that solutions could then be developed. The prototypical implementation of the concept ’Interactive Training Remote Education Experience (IT-REX)’ was used to design the base e-learning platform and to include gamification aspects. However, since IT-REX was designed for computer science and software engineering students in the first semesters, it had to be modified for a broader range of uses. To evaluate the approach of the concept, a case study was conducted in which a low-fidelity prototype of the concept was presented to lecturers and other experts in the field of higher education didactics, learning psychology, and vocational and technical pedagogy. Subsequently, a questionnaire was used to assess and evaluate the previously defined requirements. The result of this elaboration is the concept for the e-learning platform with the corresponding prototype. Based on the feedback of the lecturers and experts, improvements and revisions could be identified. Furthermore, the evaluation helped to investigate how the platform’s usability could be enhanced to improve the structuring and design of the courses by the lecturers. Finally, future developments and further investigations based on the concept were described.Item Open Access Migrating monolithic architectures to microservices : a study on software quality attributes(2022) Koch, DanielEs gibt viele Beweggründe für die Migration von einer monolithischen zu einer Microservice-Architektur, z. B. hohe Skalierbarkeit oder verbesserte Wartbarkeit. Dabei müssen jedoch mehrere Faktoren im Migrationsprozess berücksichtigt werden, darunter auch Qualitätsmerkmale. Da die Migration zu einer Microservice-Architektur keine einfache Aufgabe ist, können definierte Qualitätsziele dabei helfen, einen geeigneten Migrationsansatz auszuwählen und anschließend geeignete Architekturentscheidungen zu treffen. Ziel dieser Arbeit ist es, zu untersuchen, wie Qualitätsattribute in den Migrationsprozess eingebunden werden können, um Praktiker und Softwarearchitekten dabei zu unterstützen. Ebenso wird untersucht, welche Rolle sie im Migrationsprozess spielen. Dazu wurde zunächst eine Literaturrecherche durchgeführt, um die Qualitätsattribute zu identifizieren, die für eine Microservice-Architektur relevant sind. Anschließend wurden die Qualitätsattribute den Migrationsansätzen zugeordnet, die sie in Richtung der Zielarchitektur optimieren. Ebenso wurden die Qualitätsattribute den Architekturmustern und Best Practices zugeordnet. Auf der Grundlage der zuvor gesammelten Ergebnisse wurde ein Qualitätsmodell erstellt, das auch die Interdependenzen und Kompromisse zwischen ihnen berücksichtigt. Auf diese Weise soll das Qualitätsmodell als Leitfaden dienen, der die Auswahl geeigneter Techniken und architektonischer Entscheidungen auf der Grundlage der definierten Qualitätsziele erleichtert. Das entwickelte Qualitätsmodell wurde anschließend in ein Tool integriert, das Praktiker durch den Migrationsprozess leiten sollte. Um die Nutzbarkeit des Werkzeugs in Bezug auf das Qualitätsmodell zu untersuchen, wurde eine Evaluierung in Form einer Umfrage mit vier Praktikern aus der Industrie durchgeführt. Das Ergebnis der Evaluation zeigt, dass das integrierte Qualitätsmodell den Migrationsprozess auf Basis der definierten Qualitätsziele in der Praxis unterstützen kann und die Erweiterung des Tools eine hohe Usability aufweist.Item Open Access Comparative visualization across physical and parameter space(2022) Zeyfang, AdrianWe designed and developed an interactive visualization approach for exploring and comparing image sequences in the context of porous media research. Our tool facilitates the visual analysis of two-dimensional image sequence datasets captured during fluid displacement experiments in a porous micromodel. The images are aggregated into a single graph-based representation, allowing for an experiment to be visualized across its entire temporal domain. This graph is generated from the viscous flow patterns of the invading fluid, reducing the need for manual image masking and clean-up steps. The Node-Link representation of the graph is superimposed onto the raw images, creating a composite spatio-temporal view of the dataset. We demonstrate the functionality of our implementation by evaluating its output and performance on a collection of related datasets. We found that separate experiments in the same porous medium yield topologically different, yet visually similar flow graphs with comparable node positions.Item Open Access Bimodal taint analysis for detecting unusual parameter-sink flows(2022) Chow, Yiu WaiFinding vulnerabilities is a crucial activity, and automated techniques for this purpose are in high demand. For example, the Node Package Manager (npm) offers a massive amount of software packages, which get installed and used by millions of developers each day. Because of the dense network of dependencies between npm packages, vulnerabilities in individual packages may easily affect a wide range of software. Taint analysis is a powerful tool to detect such vulnerabilities. However, it is challenging to clearly define a problematic flow. A possible way to identify problematic flows is to incorporate natural language information like code convention and informal knowledge into the analysis. For example, a user might not find it surprising that a parameter named cmd of a function named execCommand is open to command injection. Thus this flow is likely unproblematic as the user will not pass untrusted data to cmd. In contrast, a user might not expect a parameter named value of a function named staticSetConfig to be vulnerable to command injection. Thus this flow is likely problematic as the user might pass untrusted data to value, since the natural language information from the parameter and function name suggests a different security context. To effectively exploit the implicit information in code, we introduce a bimodal taint analysis tool, Fluffy. The first modality is code: Fluffy uses a mining analysis implemented in CodeQL to find examples of flows from parameters to vulnerable sinks. The second modality is natural language: Fluffy uses a machine learning model that, based on a corpus of such examples, learns how to distinguish unexpected flows from expected flows using natural language information. We instantiate four neural models, offering different trade-offs between manual efforts required and accuracy of predictions. In our evaluation, Fluffy is able to achieve a F1-score of 0.85 or more on four common vulnerability types. In addition, Fluffy is able to flag eleven previously unknown vulnerabilities in real-life projects, of which six are confirmed.Item Open Access Analysis and development of a digital picking system using IoT and Logistic 4.0(2022) Jahagirdar, AniruddhaOrder picking is a crucial step in nearly all distribution networks and has a significant impact on how well warehouses run. Even though the majority of businesses still use manual order picking, development into diverse options for optimizing order picking operations or providing technological support for human order pickers is advancing quickly. A development in the logistics industry known as Logistics 4.0, or Industry 4.0 in logistics sector is taking place; it addresses new goals and the use of technology to handle impending issues in logistics and warehouse operations. More than half of a warehouse’s operational expenses are largely linked to order picking, which is the process of collecting material from the warehouse and delivering it to the packing station. Order picking procedures still primarily rely on manual labour, which notably contributes to the relatively high process costs, despite the prospect of digitising these procedures growing. In this study, a new way is proposed to optimise the manual operations of the paper-based order picking system by integrating the warehouse routing problem with an interactive webpage to give routes for pickers and order data in order to improve productivity and lower picking error rates. To evaluate the current level of knowledge in this area, a thorough literature study is conducted, and potential research areas in order picking are identified. Along with this, various Travelling Salesman Problem (TSP) heuristics are also examined, and thorough cost and performance analyses are done for various TSP heuristics. Additionally, an economic analysis is performed where several factors are taken into account for both the current paper-based system and the recently built digital system. In the end, this thesis work discovers that the digital picking method performs better in terms of worker ergonomics and efficiency than the traditional paper-based approach. Under the general conditions set, this is the only order picking solution that requires no modification of the warehouse’s environment and a minimum of initial investment in infrastructure.Item Open Access Factors that enhance female participation in german computer science curricula: An exploration(2022) Schäfer, MelanieDas Phänomen der Unterrepräsentation von Frauen in Informatik-Studiengängen an Deutschlands Universitäten und Hochschulen lässt sich aus zwei Perspektiven untersuchen. Die negativen Faktoren, warum sich Frauen gegen ein solches Studium entscheiden, wurden in verschiedenen wissenschaftlichen Forschungsarbeiten betrachtet. Ziel dieser Arbeit ist es, die positiven Faktoren, warum sich Frauen für ein Informatik-Studium entscheiden aufzudecken. Mittels der Constructivist Grounded Theory von Kathy Charmaz soll hierzu eine initiale Theorie oder Taxonomie zu konzipiert werden. Für die Datengenese wurden $5$ Studentinnen der Universität Stuttgart interviewt, um ihre Beweggründe und Entscheidungen zu ergründen. Die parallel stattfindende Coding-Analyse und die initiale Theoriebildung ergaben insgesamt $5$ zentrale Faktoren. Die Interessensentwicklung, die die Initiierung bis zur Identifikation, der Spezifikation und Differenzierung gegenüber anderen Interessen, definiert. Im Zusammenhang dessen steht der Selbstwirksamkeitsprozess, also die Entwicklung der inneren Überzeugung in das eigene Können schwierige Herausforderungen zu meistern. Als dritter Faktor der Persönlichkeitsentfaltung gehört der Autonomieprozess, der die Selbstständigkeit der Studentinnen bis zum Studienanfang begleitet. Zusätzlich fanden sich zwei weitere Faktoren. Die Konvergenz beschreibt die Annäherung beiden Parteien, die durch Berührungspunkte geprägt werden. Entscheidend ist nicht die Anzahl, sondern die Intensität der Interessensförderung. Letzter Faktor beschreibt die MINT-Fähigkeiten, die speziell das mathematische Verständnis der Studentinnen betrifft. Hinsichtlich der Informatik stehen die fünf Faktoren in einer starken Kohärenz, die sich sowohl negativ als auch positiv beeinflussen können. Das Wissen über die Faktoren und ihren Beeinflussungsgrad von außerhalb können dazu eingesetzt werden, um Förderungen anzustreben, um mehr Frauen für ein solches Studium zu gewinnen.Item Open Access Generating code for distributed deployments of cyber-physical systems using the MechatronicUML(2022) Stürner, DavidModels are applied in engineering disciplines to describe systems from a higher level of abstraction. In Model-Driven Software Engineering (MDSE), formal models are used to design and verify software systems and to infer platform-specific models and implementations. The MechatronicUML is an MDSE method specifically designed for distributed cyber-physical systems (CPS). This thesis explores how the MechatronicUML may be used for generating code. The exact state of previous code generation approaches is not precisely known. The objective of this thesis is to design and implement a MechatronicUML-based code generator for distributed deployments of CPS. Previous code generation approaches are analyzed for this purpose and one approach is selected and extended to support a particular type of robot car as a target platform. A taxonomy for model-based code generation is proposed to structure the analysis of the previous approaches. Based on the selected previous approach, a code generator is presented and implemented. Additionally, an automotive application scenario is used as a case study for evaluating the concept and the implementation of the presented code generator. This code generator supports modeling the distributed deployment of a CPS with the MechatronicUML and generates platform-specific source code which can be successfully compiled and deployed on the Arduino-based robot cars. Ultimately, the thesis presents a proof of concept to generate the code for a distributed CPS based on the MechatronicUML.Item Open Access Generierung und Abdeckung repräsentativer Pfadmengen in Straßennetzwerken(2022) Berner, LukasFür die Suche nach kürzesten Pfaden in sehr großen Graphen wurden verschiedene Beschleunigungstechniken, wie z.B. Contraction Hierarchies, Hub-Labels oder Transit Node Routing, entwickelt. Um optimale Anfragezeiten und Speicherverbrauch zu erreichen, benötigen viele Beschleunigungstechniken eine Menge wichtiger Knoten. In dieser Arbeit wird eine Methode zur Berechnung wichtiger Knoten eines Graphen vorgestellt. Um diese Knoten zu finden, wird auf einer repräsentativen Pfadmenge ein Hitting Set Problem mit einem Greedy-Algorithmus gelöst. Die repräsentative Pfadmenge, die möglichst unterschiedliche kürzeste Pfade des Graphen enthalten soll, wird mit einer well-separated pair decomposition und einem Quadtree berechnet. Das Verfahren wurde mit dem deutschen Straßennetzwerk (25M Knoten) getestet und liefert hier einige tausend wichtige Knoten, mit denen bereits etwa 99,9 % aller kürzesten Pfade im Graph abgedeckt sind.Item Open Access Occlusion handling in behavior planning using imitation learning for autonomous driving(2022) Palaniswamy, JanaranjaniCommissioning a self driving vehicle to run on road, requires the facilitation of complete vehicle system to work at all conditions. Behavior planning is a crucial part of the autonomous driving system and it is important to ensure safe and comfortable navigation of the ego vehicle. More advancements are required to enhance the data-driven approaches for the planning systems. The urban driving scenarios always possess a variety of disturbances and inefficiencies. In which, the roundabout is a challenging driving task where uncertainties are caused due to static priority rules and occlusions that limits the field of view for the ego vehicle. Thus behavior planning must make sure to consider the uncertainty of limited visibility of the environment explicitly. Although machine learning-based approaches show promising results for behavior planning. A single planner cannot handle all other urban driving scenarios. Hence, an imitation learning-based technique can help the behavior planner to mimic the human expert behavior. In this context, an end-to-end planning system based on imitation learning proposed by Waymo is used. The behavior planning framework makes use of mid-level input and output representations making it viable to be interfaced with existing vehicle system. The planner outputs a set of waypoints to drive the vehicle controller. However, the existing imitation learning-based planning framework with the Intelligent Driver Model (IDM) as an expert and policy model made of a multi-task network did not address this use case of occluded roundabouts. As the default IDM generates training data with a visibility of the environment, there arises a need for a strategic approach to handle the occluded environments. This thesis work aims at leveraging the existing planning system to handle the situations in a roundabout with limited visibility. Ultimately, the goal is to train the policy model with more realistic data and enable it to make safe and comfortable driving decisions. For this purpose, an occlusion algorithm is implemented to induce limited visibility of the roundabout environment in simulation. And the expert model is enhanced to handle the limited field of view much similar to how a human driver behaves. Consequently, the training dataset generated from the expert is upgraded with an additional input feature. This add-on feature in the input data provides enough knowledge for the policy to perform well in the occluded environment. A study on modern architecture search is performed and a suitable convolutional network is adopted as the backbone for this multi-task model. The enhanced behavior of the proposed approach is demonstrated via detailed quantitative analysis. For this purpose, a new comfort metric is defined and used as Key performance Indicator (KPI) to evaluate the models. An ablation study is conducted with the expert and confirmed that the new extended IDM behaves more carefully in an occlusion environment. In the end, the influence of the training data is inferred by a detailed comparison of the policy model in default and occlusion environments with different dataset configurations. The importance of more realistic data is realized and also shows that the policy model can imitate the expert behavior well enough. It is exhibited that the proposed methodology can handle the occlusions in the complex roundabout situations in simulation.