05 Fakultät Informatik, Elektrotechnik und Informationstechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6
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Item Open Access Inferring object hypotheses based on feature motion from different sources(2015) Fuchs, SteffenPerception systems in robotics are typically closely tailored to the given task, e.g., in typical pick-and-place tasks the perception systems only recognizes the mugs that are supposed to be moved and the table the mugs are placed on. The obvious limitation of those systems is that for a new task a new vision system must be designed and implemented. This master's thesis proposes a method that allows to identify entities in the world based on motion of various features from various sources. This is without relying on strong prior assumptions and to provide an important piece towards a more general perception system. While entities are rigid bodies in the world, the sources can be anything that allows to track certain features over time in order to create trajectories. For example, these feature trajectories can be obtained from RGB and RGB-D sensors of a robot, from external cameras, or even the end effector of the robot (proprioception). The core conceptual elements are: the distance variance between trajectory pairs is computed to construct an affinity matrix. This matrix is then used as input for a divisive k-means algorithm in order to cluster trajectories into object hypotheses. In a final step these hypotheses are combined with previously observed hypotheses by computing the correlations between the current and the updated sets. This approach has been evaluated on both simulated and real world data. Generating simulated data provides an elegant way for a qualitative analysis of various scenarios. The real world data was obtained by tracking Shi-Tomasi corners using the Lucas-Kanade optical flow estimation of RGB image sequences and projecting the features into range image space.Item Open Access Concept and implementation of digital beacons(2015) Chughtai, Muhammad BilalItem Open Access Lastbalancierungsverfahren für dynamische und heterogene Linked-Cell Molekülsimulation(2015) Hirschmann, SteffenIn dieser Arbeit wird die Lastbalancierung von Molekül- beziehungsweise Teilchensimulationen mit kurzreichweitigen Potenzialen betrachtet. Eine solche ist notwendig, um inhomogene Szenarien effizient über längere Zeiträume hinweg auf Parallelrechnern simulieren zu können. Hierzu werden die vorkommenden Arten von Last analysiert und in sogenannten Lastmodellen quantifiziert. Hierbei liegt der Fokus auf Rechen- und Kommunikationslasten. Anschließend wird das Problem der Lastbalancierung beschrieben. Es werden verschiedene in der Literatur bekannte Verfahren zur Lastbalancierung betrachtet, untersucht und evaluiert. Der Fokus liegt hierbei nicht auf einem einzelnen Anwendungsszenario, sondern auf der generellen Machbarkeit, den Eigenschaften und den Einschränkungen der jeweiligen Verfahren.Item Open Access Modellierung und Ausführung einer gekoppelten Festkörpersimulation mit Workflow-Choreographien(2014) Hintermayer, KerstinIm wissenschaftlichen Umfeld wird vermehrt die Workflow-Technologie eingesetzt, um Simulationen oder Berechnungen computergesteuert auszuführen. Die vorliegende Arbeit beschäftigt sich mit der Modellierung einer gekoppelten Festkörpersimulation als Workflow-Choreographie nach dem Top-Down-Ansatz. Auftauchende Herausforderungen werden identifiziert und mögliche Lösungsansätze beschrieben. Aufbauend auf dem Modellierungsergebnis werden die für die Ausführung der gekoppelten Festkörpersimulation benötigten Prozesse implementiert und vorgestellt. Die fertige Modellierung wird im Vergleich mit den Anforderungen beurteilt. Die Modellierung kann als Basis für zukünftige Arbeiten dienen und bietet Ansätze für aufbauende Untersuchungen. Dadurch wird eine Verfeinerung für zukünftige Workflowmodellierungen auf Basis einer Choreographie ermöglicht.Item Open Access Robust Quasi-Newton methods for partitioned fluid-structure simulations(2015) Scheufele, KlaudiusIn recent years, quasi-Newton schemes have proven to be a robust and efficient way for the coupling of partitioned multi-physics simulations in particular for fluid-structure interaction. The focus of this work is put on the coupling of partitioned fluid-structure interaction, where minimal interface requirements are assumed for the respective field solvers, thus treated as black box solvers. The coupling is done through communication of boundary values between the solvers. In this thesis a new quasi-Newton variant (IQN-IMVJ) based on a multi-vector update is investigated in combination with serial and parallel coupling systems. Due to implicit incorporation of passed information within the Jacobian update it renders the problem dependent parameter of retained previous time steps unnecessary. Besides, a whole range of coupling schemes are categorized and compared comprehensively with respect to robustness, convergence behaviour and complexity. Those coupling algorithms differ in the structure of the coupling, i.\,e., serial or parallel execution of the field solvers and the used quasi-Newton methods. A more in-depth analysis for a choice of coupling schemes is conducted for a set of strongly coupled FSI benchmark problems, using the in-house coupling library preCICE. The superior convergence behaviour and robust nature of the IQN-IMVJ method compared to well known state of the art methods such as the IQN-ILS method, is demonstrated here. It is confirmed that the multi-vector method works optimal without the need of tuning problem dependent parameters in advance. Furthermore, it appears to be especially suitable in conjunction with the parallel coupling system, in that it yields fairly similar results for parallel and serial coupling. Although we focus on FSI simulation, the considered coupling schemes are supposed to be equally applicable to various kinds of different volume- or surface-coupled problems.Item Open Access Extending parking assistance for automative user interfaces(2014) Georoceanu, RaduNowadays the trend in the automotive industry is to integrate systems that go beyond the scope of just maneuvering the car. Navigation, communication, and entertainment functions have become usual in most cars. The multitude of sensors present in vehicles today can be used to collect information that can be shared with other drivers in order to make the roads safer and cleaner. A more troubling issue that affects drivers is the search for free parking spots, because of the time waste, fuel consumtion and effort. There are already solutions available that try to help drivers diminish these problems, like crowdsourcing smartphone apps, but they are still far away from being a reliable solution. The overall goal of this thesis is to find new ways of providing parking information to drivers. This information is collected from vehicles which are equipped with latest sensoric hardware capable of detecting parking spaces while driving and distribute these information to the cloud, sharing it with other drivers using smartphones or vehicle's integrated displays. Though the idea is simple, there are many challanges that need to be addressed. The thesis will also look into ways of improving parking surveillance for vehicles to make them less susceptible to vandalism and thefts, by using latest vehicle-integrated video camera systems. A study will be made to see what information drivers want to have related to parking and how this information can be displayed to them. Further, a cloud based-implementation of such a system will be presented in detail and an evaluation will be made to see how the system behaves in the real world.Item Open Access Modeling of a multi-core microblaze system at RTL and TLM abstraction levels in systemC(2013) Eissa, KarimTransaction Level Modeling (TLM) has recently become a popular approach for modeling contemporary Systems-on-Chip (SoCs) on a higher abstraction level than Register Transfer Level (RTL). In this thesis a multi-core system based on the Xilinx MicroBlaze micro-processor is modeled at RTL and TLM abstraction levels in SystemC. Both implemented models have cycle accurate timing, and are verified against the reference VHDL model using a VHDL / SystemC mixed-language simulation with ModelSim. Finally, performance measurements are carried out to evaluate simulation speedup at the transaction level. Modeling of the MicroBlaze processor is based on a MicroBlaze Instruction Set Simulator (ISS) from SoCLib. A wrapper is therefore implemented to provide communication interfaces between the processor and the rest of the system, as well as control the timing of the ISS operation to reach cycle accurate models. Furthermore, a local memory module based on Block Random Access Memories (BRAMs) is modeled to simulate a complete system consisting of a processor and a local memory.Item Open Access Cost optimization for data placement strategies in an analytical cloud service(2016) Saleem, Muhammad UsmanAnalyzing a large amount of business-relevant data in near-realtime in order to assist decision making became a crucial requirement for many businesses in the last years. Therefore, all major database system vendors offer solutions that assist customers in this requirement with systems that are specially tuned for accelerating analytical workloads. Before the decision is made to buy such a huge and expensive solution, customers are interested in getting a detailed workload analysis in order to estimate potential benefits. Therefore, a more agile solution is desirable having lower barriers to entry that allows customers to assess analytical solutions for their workloads and lets data scientists experiment with available data on test systems before rolling out valuable analytical reports on a production system. In such a scenario where separate systems are deployed for handling transactional workloads of daily customers business and conducting business analytics on either a cloud service or a dedicated accelerator appliance, data management and placement strategies are of high importance. Multiple approaches exist for keeping the data set in-sync and guaranteeing data coherence with unique characteristics regarding important metrics that impact query performance, such as the latency when data will be propagated, achievable throughputs for larger data volumes, or the amount of required CPU to detect and deploy data changes. So the important heuristics are analyzed and evolved in order to develop a general model for data placement and maintenance strategies. Based on this theoretical model, a prototype is also implemented that predicts these metrics.Item Open Access REST compliant clients for REST APIs(2014) Jaber, MustafaIn today's distributed systems, REST services play a centric role in defining applications' architecture. Current technologies and literature focus on building server-side REST applications. But they fail to build generic and REST compliant client solutions. Therefore, most offered services and especially client applications rarely comply to the constraints that constitute the REST architecture. In this thesis, the architecture of a new generic framework for building REST compliant client applications is introduced. In addition, a new description language that conforms to REST's constraints and helps reduce development time is presented. We describe in this work the building-blocks of the proposed solutions and show a software implementation of a library that leverages the solutions' architectures. Using the proposed framework and description language, client applications that conform to the full set of REST's constraints can be built in an easy and optimized way. In addition, REST service providers can rely on the proposed description language to eliminate the complexity of repetitively building customized solutions for different technologies or platforms.Item Open Access Serialization of foreign types with SKilL(2016) Weißer, ConstantinSKilL provides a language independent means to specify serialisable data types. Bindings for these types can be generated automatically for multiple supported languages based on this specification. However, using these bindings is only hassle-free for newly written code, because existing types must be replaced by the controlled generated bindings. This impedes the usefulness of SKilL in old projects. We investigate a new approach. SKilL is to be extended in order to support the reuse of existing Java classes, so-called foreign types. The tool shall be able to analyse classes, associate them with specified SKilL types, verify the type correctness of this association and generate the required code in order to serialise objects of these types. This thesis points out the occurring challenges and discusses potential solutions. We experiment with several alternatives and provide insight into their pros and cons, as well as justification for our design. Functional and performance tests assess our implementation and shortcomings are addressed in detail.