162 research outputs found

    Golf ball picker robot: path generation in unstructured environments towards multiple targets

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    Tese de doutoramento Engineering Design and Advanced Manufacturing Leaders for Technical IndustriesThe new TWIN-RRT* algorithm solves a motion planning problem in which an agent has multiple possible targets where none of them is compulsory, and retrieves feasible, ―low cost‖, asymptotically optimal and probabilistically complete paths. The TWIN-RRT* algorithm solves path planning problems for both holonomic and non-holonomic robots with or without kinodynamic constraints in a 2D environment, but it was designed to work as well with higher DOF agents and different applications. The new algorithm provides a practical implementation of feasible and fast planning especially where a closed loop is required. Initial and final configurations are allowed to be exactly the same. The TWIN-RRT* algorithm computes an efficient path for one sole agent towards multiple targets where none of them is mandatory. It inherits the low computational cost, probabilistic completeness and asymptotical optimality from RRT*. It uses efficiency as cost function, which can be adapted depending on the application. The TWIN-RRT* complies both with kinodynamic constraints and different cost functions. It was developed to solve a real problem where a robot has to collect golf balls in a driving range, where thousands of balls accumulate every day. This thesis is part of a bigger project, Golfminho, to develop an autonomous robot capable of efficiently collecting balls in a golf practice field.O novo algoritmo TWIN-RRT* resolve problemas de planeamento de trajetĂłrias em que um agente tem mĂșltiplos alvos, onde nenhum deles Ă© obrigatĂłrio, e produz um plano exequĂ­vel, de "baixo custo" computacional, assintoticamente Ăłtimo e probabilisticamente completo. O TWINRRT* resolve problemas de planeamento de trajetĂłrias tanto para robĂŽs holonĂłmicos como nĂŁo holonĂłmicos com ou sem restriçÔes cinemĂĄticas e/ou dinĂąmicas num ambiente 2D, mas foi projetado para funcionar tambĂ©m com agentes com maiores graus de liberdade e em diferentes aplicaçÔes. O novo algoritmo fornece uma implementação prĂĄtica de um planeamento viĂĄvel e rĂĄpido, especialmente quando Ă© necessĂĄrio produzir uma trajetĂłria fechada. As configuraçÔes iniciais e finais podem ser exatamente iguais. O algoritmo TWIN-RRT* calcula um caminho eficiente para um agente Ășnico em direção a mĂșltiplos alvos, onde nenhum deles Ă© obrigatĂłrio. Herda o baixo custo computacional, integralidade probabilĂ­stica e otimização assintĂłtica do RRT*. Usa a eficiĂȘncia como função de custo, que pode ser adaptada em função das diferentes aplicaçÔes. Para alĂ©m de diferentes funçÔes de custo, o TWIN-RRT* tambĂ©m mostra conformidade com restriçÔes cinemĂĄticas. Foi desenvolvido para resolver um problema real em que um robĂŽ tem que recolher bolas de golfe num Driving Range, onde se acumulam milhares de bolas de golfe por dia. Esta tese Ă© parte integrante do projeto Golfminho, para o desenvolvimento de um robĂŽ autĂłnomo capaz de recolher eficientemente bolas num campo de prĂĄticas de golfe.Fundação para a CiĂȘncia e Tecnologia (FCT) for the PhD grant nÂș. SFRH/BD/43008/2008

    A COLLISION AVOIDANCE SYSTEM FOR AUTONOMOUS UNDERWATER VEHICLES

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    The work in this thesis is concerned with the development of a novel and practical collision avoidance system for autonomous underwater vehicles (AUVs). Synergistically, advanced stochastic motion planning methods, dynamics quantisation approaches, multivariable tracking controller designs, sonar data processing and workspace representation, are combined to enhance significantly the survivability of modern AUVs. The recent proliferation of autonomous AUV deployments for various missions such as seafloor surveying, scientific data gathering and mine hunting has demanded a substantial increase in vehicle autonomy. One matching requirement of such missions is to allow all the AUV to navigate safely in a dynamic and unstructured environment. Therefore, it is vital that a robust and effective collision avoidance system should be forthcoming in order to preserve the structural integrity of the vehicle whilst simultaneously increasing its autonomy. This thesis not only provides a holistic framework but also an arsenal of computational techniques in the design of a collision avoidance system for AUVs. The design of an obstacle avoidance system is first addressed. The core paradigm is the application of the Rapidly-exploring Random Tree (RRT) algorithm and the newly developed version for use as a motion planning tool. Later, this technique is merged with the Manoeuvre Automaton (MA) representation to address the inherent disadvantages of the RRT. A novel multi-node version which can also address time varying final state is suggested. Clearly, the reference trajectory generated by the aforementioned embedded planner must be tracked. Hence, the feasibility of employing the linear quadratic regulator (LQG) and the nonlinear kinematic based state-dependent Ricatti equation (SDRE) controller as trajectory trackers are explored. The obstacle detection module, which comprises of sonar processing and workspace representation submodules, is developed and tested on actual sonar data acquired in a sea-trial via a prototype forward looking sonar (AT500). The sonar processing techniques applied are fundamentally derived from the image processing perspective. Likewise, a novel occupancy grid using nonlinear function is proposed for the workspace representation of the AUV. Results are presented that demonstrate the ability of an AUV to navigate a complex environment. To the author's knowledge, it is the first time the above newly developed methodologies have been applied to an A UV collision avoidance system, and, therefore, it is considered that the work constitutes a contribution of knowledge in this area of work.J&S MARINE LT

    The review of migration decisions — a story of borders and orders

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    In the last decade in Australia and the United Kingdom, the review of immigration decisions in tribunals and courts has been marked by constitutional conflict between the executive and the judiciary; a crisis of confidence; and continual change. This thesis explores what this tumultuous story of immigration review tells us about the law — as a social practice, as an institution, and as a linguistic genre — in these jurisdictions, in these times. This thesis argues that the story of immigration review is explained best not through the conventional story of a battle between the executive and the judiciary, but rather as a story of the fundamental challenges immigration poses to the social, institutional, ideological and linguistic dimensions of law, and of the attempt by judges and the legal community to defend their different conceptions of the legitimacy of the law from those challenges, in different ways. Four fundamental challenges are identified. First, immigration challenges the coherence of the legal framework, as it exposes tensions within and between the different legal regimes. Second, the more reductive language used in legal contexts competes badly with more complex, and more socially powerful, discourses about immigration. Third, immigration challenges the capacity of law to perform the functions of resolving disputes and regulating behaviour. Fourth, immigration challenges our deepest concepts of legality. The thesis examines these challenges, and the responses they provoke, by drawing on the insights of migration studies, contemporary political philosophy, language and the law, and regulatory theory, as well as examining important case law in detail. In doing so, it aims both to capture the story of immigration review more fully, and to illuminate some of the complexities of, and limits to, the contemporary social practice of law

    Supplement 1

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    The 7th Nordic Conference on Epidemiology and Registry-based Health Research – NordicEpi 201

    Policy and institutional arrangements on the provision and sustainability of Non-Formal Secondary Education (NFSE) in Tanzania

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    Shirima GH. Policy and institutional arrangements on the provision and sustainability of Non-Formal Secondary Education (NFSE) in Tanzania. Bielefeld: UniversitÀt Bielefeld; 2016

    Re-forming multi-storey housing: the regeneration of urban housing estates in Britain

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    A thesis submitted to the Faculty of Science, Technology and Design, University of Luton, in partial fulfilment of the requirements for the degree of Doctor of PhilosophyEstates of multi-storey housing present some of the most intractable problems for urban policy. Socially, many are characterised by a complex of deprivation. Physically, they often suffer from serious technical problems and poor environmental quality. This study traces the development of multi-storey housing from its early beginnings in the 19th century to the period from the mid-1950s to the early 1970s when most of the contemporary legacy of estates was built. In this period, it is suggested, the concentration on 'low cost' led to the poor design of access systems, the use of untried mass-production techniques and the virtual elimination of social facilities. All these economies sowed the seeds of the social rejection and degeneration that was to follow. The central question is whether such estates can be successfully modernised -or whether the only solution is to demolish them. In seeking an answer the various responses of social landlords are analysed. It emerges that the older, smaller estates can be effectively adapted to provide good housing. The large scale, more recent estates, however, have proved more resistant to improvement. Despite the fact that government has increasingly targeted the problem estates of the 1960s and 70s, many improvement schemes have met with limited success. Drawing on an analysis of past practice, a 'model of regeneration' is defined. This concentrates on the need for tenant participation; on the importance of design solutions which are both technically and socially appropriate; and on management which is sensitive to local needs. This model was tested through case studies on recent improvement schemes. From the results, conclusions are drawn about the value of the model and the prospects for regenerating the various types of multi-storey housing Finally, a strategic approach is defined which can re-form the estates and re-integrate them into the mainstream urban environment

    Sustainable Agriculture and Advances of Remote Sensing (Volume 1)

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    Agriculture, as the main source of alimentation and the most important economic activity globally, is being affected by the impacts of climate change. To maintain and increase our global food system production, to reduce biodiversity loss and preserve our natural ecosystem, new practices and technologies are required. This book focuses on the latest advances in remote sensing technology and agricultural engineering leading to the sustainable agriculture practices. Earth observation data, in situ and proxy-remote sensing data are the main source of information for monitoring and analyzing agriculture activities. Particular attention is given to earth observation satellites and the Internet of Things for data collection, to multispectral and hyperspectral data analysis using machine learning and deep learning, to WebGIS and the Internet of Things for sharing and publishing the results, among others
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