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Mouad, Mehdi. "Architecture de COntrôle/COmmande dédiée aux systèmes Distribués Autonomes (ACO²DA) : application à une plate-forme multi-véhicules." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22437/document.
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La complexité associée à la coordination d’un groupe de robots mobiles est traitée dans cette thèse en investiguant plus avant les potentialités des architectures de commande multi-contrôleurs dont le but est de briser la complexité des tâches à exécuter. En effet, les robots mobiles peuvent évoluer dans des environnements très complexes et nécessitent de surcroît une coopération précise et sécurisée pouvant rapidement devenir inextricable. Ainsi, pour maîtriser cette complexité, le contrôleur dédié à la réalisation d’une tâche est décomposé en un ensemble de comportements/contrôleurs élémentaires (évitement d’obstacles et de collision entre les robots, attraction vers une cible, planification, etc.) qui lient les informations capteurs (provenant des capteurs locaux du robot, etc.) aux actionneurs des différentes entités robotiques. La tâche considérée dans cette thèse correspond à la navigation d’un groupe de robots mobiles dans des environnements peu ou pas connus en présence d’obstacles (statiques et dynamiques). La spécificité de l’approche théorique consiste à allier les avantages des architectures multi-contrôleurs à ceux des systèmes multi-agents et spécialement les modèles organisationnels afin d’apporter un haut niveau de coordination entre les agents/robots mobiles. Le groupe de robots mobiles est alors coordonné suivant les différentes normes et spécifications du modèle organisationnel. Ainsi, l’activation d’un comportement élémentaire en faveur d’un autre se fait en respectant les contraintes structurelles des robots en vue d’assurer le maximum de précision et de sécurité des mouvements coordonnés entre les différentes entités mobiles. La coopération se fait à travers un agent superviseur (centralisé) de façon à atteindre plus rapidement la destination désirée, les événements inattendus sont gérés quant à eux individuellement par les agents/robots mobiles de façon distribuée. L’élaboration du simulateur ROBOTOPIA nous a permis d’illustrer chacune des contributions de la thèse par un nombre important de simulations<br>The difficulty of coordinating a group of mobile robots is adressed in this thesis by investigating control architectures which aim to break task complexity. In fact, multi-robot navigation may become rapidly inextricable, specifically if it is made in hazardous and dynamical environment requiring precise and secure cooperation. The considered task is the navigation of a group of mobile robots in unknown environments in presence of (static and dynamic) obstacles. To overcome its complexity, it is proposed to divide the overall task into a set of basic behaviors/controllers (obstacle avoidance, attraction to a dynamical target, planning, etc.). Applied control is chosen among these controllers according to sensors information (camera, local sensors, etc.). The specificity of the theoretical approach is to combine the benefits of multi-controller control architectures to those of multi-agent organizational models to provide a high level of coordination between mobile agents-robots systems. The group of mobile robots is then coordinated according to different norms and specifications of the organizational model. Thus, activating a basic behavior in favor of another is done in accordance with the structural constraints of the robots in order to ensure maximum safety and precision of the coordinated movements between robots. Cooperation takes place through a supervisor agent (centralized) to reach the desired destination faster ; unexpected events are individually managed by the mobile agents/robots in a distributed way. To guarantee performance criteria of the control architecture, hybrid systems tolerating the control of continuous systems in presence of discrete events are explored. In fact, this control allows coordinating (by discrete part) the different behaviors (continuous part) of the architecture. The development of ROBOTOPIA simulator allowed us to illustrate each contribution by many results of simulations
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Jahn, Jiří. "Potlačení turbulentního proudění v potrubí." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-444297.
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This thesis deals with ways to suppress turbulent flow in pipelines. In the first part various methods of laminarization are presented, when the turbulent flow is transformed into laminar flow, including the results of experiments published by the authors. The next part presents the results from CFD. The calculations were performed for one of the methods mentioned in the first part and the results were compared with each other. In addition, several options have been suggested to improve the original method.
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Hajjdiab, Hassan. "Vision-based localization, map building and obstacle reconstruction in ground plane environments." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/29109.
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The work described in this thesis develops the theory of 3D obstacle reconstruction and map building problems in the context of a robot, or a team of robots, equipped with one camera mounted on board. The study is composed of many problems representing the different phases of actions taken by the robot.
This thesis first studies the problem of image matching for wide baseline images taken by moving robots. The ground plane is detected and the inter-image homography induced by the ground plane is calculated. A novel technique for ground plane matching is introduced using the overhead view transformation.
The thesis then studies the simultaneous localization and map building (SLAM) problem for a team of robots collaborating in the same work site. A vision-based technique is introduced in this thesis to solve the SLAM problem.
The third problem studied in this thesis is the 3D obstacle reconstruction of the obstacles lying on the ground surface. In this thesis a Geometric/Variational level set method is proposed to reconstruct the obstacles detected by the robots.
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Chuhran, Christopher D. "Obstacle avoidance control in the vertical plane for the REMUS autonomous underwater vehicle." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03sep%5FChuhran.pdf.
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RIFAI, SAID. "Etude du rayonnement acoustique d'un obstacle cylindrique place dans un ecoulement d'air subsonique." Poitiers, 1989. http://www.theses.fr/1989POIT2280.
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On etudie le rayonnement acoustique engendre par un ecoulement subsonique autour de cylindres de section circulaire. Dans une premiere partie, des methodes de mesure bidimensionnelles de l'intensite acoustique sont utilisees pour caracteriser le champ sonore du a un cylindre isole, a surface lisse ou a rugosite fine aleatoire. La seconde partie est une determination experimentale des pressions parietales sur un ou deux cylindres consideres comme des maquettes de cables de transport electrique, et ayant en consequence une structure de surface a rugosite forte et periodique. Les lois de coherence dans une section ou en envergure, ainsi que les fonctions de reponse en frequence des pressions instationnaires entre les deux cylindres sont donnees. Dans la troisieme partie est propose un modele numerique plan de rayonnement acoustique d'un ensemble de monopoles places dans ce plan. En introduisant les parametres issus des experiences ci-dessus, un modele de calcul du bruit du, a un ou deux cables de transport electriques places l'un derriere l'autre, est enfin presente
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Cutzach, Pierre-Marie. "Influence d'une interface plane sur la diffraction des ondes acoustiques et électromagnetiques par un obstacle." Rennes 1, 1997. http://www.theses.fr/1997REN10022.
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La premiere partie de ce memoire est consacree a l'etude de problemes de diffraction d'ondes acoustiques et electromagnetiques, par un obstacle place dans un milieu contenant deux couches homogenes separees par une interface plane. On montre que l'utilisation des conditions de rayonnement habituelles dans chaque couche fournit des problemes de diffraction bien poses. L'analyse repose sur l'etude des noyaux de green, ce qui permet de relier les conditions de rayonnement a des formules de representation integrale. Dans une seconde partie, nous nous interessons au traitement numerique des problemes ci-dessus. En electromagnetisme, nous presentons une technique de regularisation des equations de maxwell qui conduit a une discretisation par elements finis nodaux.
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Lefaudeux, Benjamin. "Détection, localisation et suivi des obstacles et objets mobiles à partir d'une plate-forme de stéréovision." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2013. http://tel.archives-ouvertes.fr/tel-00918508.
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Les véhicules autonomes se mouvant dans un environnement quelconque peuvent être confrontés à la présence de nombreux objets mobiles, dont la localisation et la trajectoire sont indépendantes. Cette problématique est particulièrement présente dans la thématique du transport en milieu urbain, mais sa portée est plus générale. On présente dans cette thèse une solution de perception d'un environnement dynamique, à partir d'une paire de caméra, qui vise à fournir en temps réel une cartographie en trois dimensions de l'environnement courant, ainsi que la vitesse indépendante des points suivis. Cette solution propose par ailleurs des algorithmes de détection, segmentation et suivi des objets mobiles, et fourni donc une liste des objets mobiles de l'environnement, dont les positions, dimensions et vitesses sont connues.
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Hemminger, Daniel L. "Vertical plane obstacle avoidance and control of the REMUS autonomous underwater vehicle using forward look sonar." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FHemminger.pdf.
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Xu, Bo Garner Brian Alan. "A linked-plane obstacle-set algorithm for modeling broad muscle paths application to the deltoid muscle /." Waco, Tex. : Baylor University, 2008. http://hdl.handle.net/2104/5212.
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Lefaudeux, Benjamin. "Détection, localisation et suivi des obstacles et objets mobiles à partir d'une plate forme de stéréo-vision." Thesis, Paris, ENMP, 2013. http://www.theses.fr/2013ENMP0091/document.
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Cette thèse s'inscrit dans la problématique de la perception des véhicules autonomes, qui doivent notamment être capables de détecter et de positionner à tout moment les éléments fixes et mobiles de leur environnement. Les besoins sont ensuite multiples, de la détection d'obstacles à la localisation du porteur dans l'espace, et de nombreuses méthodes de la littérature s'y attellent. L'objectif de cette thèse est de reconstituer, à partir de prises de vues de stéréo-vision, une carte en trois dimensions décrivant l'environnement proche ; tout en effectuant une détection, localisation et suivi dans le temps des objets mobiles.La détection et le suivi dans le temps d'un grand nombre de points d'intérêt constitue une première étape. Après avoir effectué une comparaison exhaustive de divers détecteurs de points d'intérêt de la littérature, on propose pour réaliser le suivi de points une implémentation massivement parallélisée de l'algorithme KLT, dans une configuration redondante réalisée pendant cette thèse. Cette implémentation autorise le suivi fiable de milliers de points en temps réel, et se compare favorablement à l'état de l'art.Il s'agit ensuite d'estimer le déplacement du porteur, et de positionner ces points dans l'espace, tâche pour laquelle on propose une évolution robuste d'une procédure bien connue, dite "SVD", suivie d'un filtrage par UKF, qui nous permettent d'estimer très rapidement le mouvement propre du porteur. Les points suivis sont ensuite positionnés dans l'espace, en prenant en compte leur possible mobilité, en estimant continuellement la position la plus probable compte tenu des observations successives.La détection et le suivi des objets mobiles font l'objet d'une dernière partie, dans laquelle on propose une segmentation originale tenant compte des aspects de position et de vitesse. On exploite ainsi une des singularités de notre approche, qui conserve pour chaque point positionné un ensemble cohérent de positions dans le temps. Le filtrage et le suivi des cibles se basent finalement sur un filtre GM-PHD<br>This PhD work is to be seen within the context of autonomous vehicle perception, in which the detection and localisation of elements of the surroundings in real time is an obvious requirement. Subsequent perception needs are manyfold, from localisation to obstacle detection, and are the subject of a continued research interest. The goal of this work is to build, in real time and from stereovision acquisition, a 3D map of the surroundings ; while detecting and tracking moving objects.Interest point selection and tracking on picture space are a first step, which we initiate by a thorough comparison of detectors from the literature. As regards tracking, we propose a massively parallel implementation of the standard KLT algorithm, using redundant tracking to provide reliable quality estimation. This allows us to track thousands of points in real-time, which compares favourably to the state of the art.Next step is the ego-motion estimation, along with the positioning of tracked points in 3D space. We first propose an iterative variant of the well known “SVD” process followed by UKF filtering, which allows for a very fast and reliable estimation. Then the position of every followed interest point is filtered on the fly over time, in contrast to most dense approaches from the literature.We finally propose a segmentation of moving objects in the augmented position-speed space, which is made possible by our continuous estimation of feature points position. Target tracking and filtering finally use a GM-PHD approach
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Kim, Nam Shin. "Analyse expérimentale d'un jet turbulent impactant sur un plaque plane et sur un obstacle de section carrée." Toulouse 3, 2005. http://www.theses.fr/2005TOU30074.
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Cette étude aborde l'impact d'un jet sur une plaque plane et sur un obstacle de section carrée. L'objectif de ce travail est l'analyse expérimentale de l'écoulement, et du transfert de chaleur associé, lorsque la surface est chauffée à densité de flux constante. Les mesures de vitesse et de turbulence ont été menées par la Vélocimétrie par Images des Particules (PIV) et l'anémométrie à fil chaud, ce qui a permis la mesure de chaque composante et du champ complet en particulier au voisinage des parois. Différents post-traitements de la PIV ont permis une nette amélioration de l'évaluation des fluctuations de vitesse. Les mesures de la température ont été effectuées par la thermographie infrarouge et la thermométrie à fil froid. La caméra utilisée, de technologie avancée, possède une résolution thermique très faible. Un travail important de post traitement des images infrarouge a permis de quantifier le champ de coefficient d'échange avec une précision inférieure à 5%. Plusieurs corrections de la température ont été menées sur les mesures par la thermométrie à fil froid pour tenir compte des effets inertiel et de conduction au niveau de la sonde. Les mesures concernant l'impact d'un jet sur une plaque plane ont complété les données de la littérature tout en mettant en évidence quelques désaccords. Nous proposons une analyse qui permet d'expliquer l'effet de la distance d'impact sur le coefficient de transfert de chaleur local. Ce travail représente une base de données aérothermiques cohérente pour la validation des modèles de turbulence. L'impact du jet sur un barreau à section carrée a montré plusieurs structures d'écoulement 3D intéressantes et une distribution complexe du coefficient de transfert de chaleur associée. Les phénomènes de décollement et de recirculation 3D ont été identifiés et analysés. Egalement, l'influence de la position du jet par rapport au barreau sur la topologie de l'écoulement a été clairement mise en évidence<br>This study approaches the jet impingement on a flat plate and on a square sectioned obstacle. The objective of this work is the experimental analysis of the flow and the associated heat transfer when surface is heated with a constant heat flux. The turbulence and velocity measurements were carried out by the Particle Image Velocimetry (PIV) and the hot wire anemometer, which allow to the measurements of each velocity component and of the complete field, specially close to the wall. Several post processing of the PIV allowed an improvement of the evaluation of the velocity components fluctuations. The temperature was measured using the infrared thermography and the cold wire thermometry. The chosen camera, using a advanced technology, have a very small temperature resolution. An important post processing analysis of infrared pictures allows the quantification of the field of heat transfer coefficient with an accuracy lower than 5%. Several corrections of the temperature were conducted in the cold wire thermometry measurement to take into account probe inertia and conduction effects. These measurements concerning the impingement of a jet on a flat plate supplemented the literature data (Baughn & Shimizu (1989) and Cooper et al. (1993)) but emphasized some discrepancy. We proposed an analysis to understand the effect of jet distance from the surface on the local heat transfer coefficient. This work also represent a coherent aerothermal new database for the validation of turbulence models. The impingement of jet on a square sectioned bar showed several interesting 3D flow structures and associated complex heat transfer coefficient distributions. The phenomena of flow seperation and 3D recirculation were identified and analyzed. Also, the influence of the jet position to the bar on the flow topology and on the heat transfer was investigated
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Durusu, Deniz. "Camera Controlled Pick And Place Application With Puma 760 Robot." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606759/index.pdf.
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This thesis analyzes the kinematical structure of Puma 760 arm and introduces the implementation of image based pick and place application by taking care of the obstacles in the environment. Forward and inverse kinematical solutions of PUMA 760 are carried out. A control software has been developed to calculate both the forward and inverse kinematics solution of this manipulator. The control program enables user to perform both offline programming and real time realization by transmitting the VAL commands (Variable Assembly Language) to the control computer.
Using the proposed inverse kinematics solutions, an interactive application is generated on PUMA 760 arm. The picture of the workspace is taken using a fixed camera attached above the robot workspace. The captured image is then processed to find the position and the distribution of all objects in the workspace. The target is differentiated from the obstacles by analyzing some specific properties of all objects, i.e. roundness. After determining the configuration of the workspace, a clustering based search algorithm is executed to find a path to pick the target object and places it to the desired place. The trajectory points in pixel coordinates, are mapped into the robot workspace coordinates by using the camera calibration matrix obtained in the calibration procedure of the robot arm with respect to the attached camera. The required joint angles, to get the end effector of the robot arm to the desired location, are calculated using the Jacobian type inverse kinematics algorithm. The VAL commands are generated and sent to the control computer of PUMA 760 to pick the object and places it to a user defined location.
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Baxter, Steven J. "Numerical simulation of three-dimensional free surface film flow over or around obstacles on an inclined plane." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11343/.
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Within the bearing chamber of a gas turbine aero-engine, lubrication of the shaft and other bearings is achieved by an oil film which may become significantly disturbed by interacting with a range of chamber geometries which protrude from the chamber wall. Minimizing these disturbances and preventing possible dry areas is crucial in optimizing a bearing chambers design. In addition, multiple obstructions may be located close to one another, resulting in a more complex disturbed film profile than by individual obstacles. Prediction of the disturbance of the film is an important aspect of bearing chamber design. For analysis of the film profile over or around a local obstacle, typical bearing chamber flows can be approximated as an incompressible thin film flow down an inclined wall driven by gravity. The Reynolds number of thin film flows is often small, and for the bulk of this thesis a Stokes flow assumption is implemented. In addition, thin films are often dominated by surface tension effects, which for accurate modelling require an accurate representation of the free surface profile. Numerical techniques such as the volume of fluid method fail to track the surface profile specifically, and inaccuracies will occur in applying surface tension in this approach. A numerical scheme based on the boundary element method tracks the free surface explicitly, alleviating this potential error source and is applied throughout this thesis. The evaluation of free surface quantities, such as unit normal and curvature is achieved by using a Hermitian radial basis function interpolation. This hermite interpolation can also be used to incorporate the far field boundary conditions and to enable contact line conditions to be satisfied for cases where the obstacle penetrates the free surface. Initial results consider a film flowing over an arbitrary hemispherical obstacle, fully submerged by the fluid for a range of flow configurations. Comparison is made with previously published papers that assume the obstacle is small and / or the free surface deflection and disturbance velocity is small. Free surface profiles for thin film flows over hemispherical obstacles that approach the film surface are also produced, and the effects of near point singularities considered. All free surface profiles indicate an upstream peak, followed by a trough downstream of the obstacle with the peak decaying in a “horseshoe” shaped surface deformation. Flow profiles are governed by the plane inclination, the Bond number and the obstacle geometry; effects of these key physical parameters on flow solutions are provided. The disturbed film profiles over multiple obstacles will differ from the use of a single obstacle analysis as their proximity decreases. An understanding of the local interaction of individual obstacles is an important aspect of bearing chamber design. In this thesis the single obstacle analysis is extended to the case of flow over multiple hemispheres. For obstacles that are separated by a sufficiently large distance the flow profiles are identical to those for a single obstacle. However, for flow over multiple obstacles with small separation, variations from single obstacle solutions maybe significant. For flow over two obstacles placed in-line with the incident flow, variations with flow parameters are provided. To identify the flexibility of this approach, flows over three obstacles are modelled. The calculation of flows around obstacles provides a greater challenge. Notably, a static contact line must be included such that the angle between the free surface and the obstacle is introduced as an extra flow parameter that will depend both on the fluid and the obstacle surface characteristics. The numerical models used for flow over hemispheres can be developed to consider film flow around circular cylinders. Numerical simulations are used to investigate flow parameters and boundary conditions. Solutions are obtained where steady flow profiles can be found both over and around a cylindrical obstacle raising the awareness of possible multiple solutions. Flow around multiple obstacles is also analyzed, with profiles produced for flow around two cylinders placed in various locations relative to one another. As for flow over two hemispheres, for sufficiently large separations the flow profiles are identical to a single obstacle analysis. For flow around two obstacles spaced in the direction of the flow, effects of altering the four governing parameters; plane inclination angle, Bond number, obstacle size, and static contact angle are examined. The analysis of flow around three cylinders in two configurations is finally considered. In addition, for two obstacles spaced in-line with the incident flow, the numerical approaches for flow over and flow around are combined to predict situations where flow passes over an upstream cylinder, and then around an identical downstream cylinder. The final section of this thesis removes the basic assumption of Stokes flow, through solving the full Navier-Stokes equations at low Reynolds number and so incorporating the need to solve nonlinear equations through the solution domain. An efficient numerical algorithm for including the inertia effects is developed and compared to more conventional methods, such as the dual reciprocity method and particular integral techniques for the case of a three-dimensional lid driven cavity. This approach is extended to enable calculation of low Reynolds number film profiles for both flow over and around a cylinder. Results are compared to the analysis from previous Stokes flow solutions for modest increases in the Reynolds number.
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Cuerington, Andre M. "The shortest path problem in the plane with obstacles : bounds on path lengths and shortest paths within homotopy classes." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28532.
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Tarcin, Serkan. "Fast Feature Extraction From 3d Point Cloud." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615659/index.pdf.
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To teleoperate an unmanned vehicle a rich set of information should be gathered from surroundings.These systems use sensors which sends high amounts of data and processing the data in CPUs can be time consuming. Similarly, the algorithms that use the data may work slow because of the amount of the data. The solution is, preprocessing the data taken from the sensors on the vehicle and transmitting only the necessary parts or the results of the preprocessing. In this thesis a 180 degree laser scanner at the front end of an unmanned ground vehicle (UGV) tilted up and down on a horizontal axis and point clouds constructed from the surroundings. Instead of transmitting this data directly to the path planning or obstacle avoidance algorithms, a preprocessing stage has been run. In this preprocess rst, the points belonging to the ground plane have been detected and a simplied version of ground has been constructed then the obstacles have been detected. At last, a simplied ground plane as ground and simple primitive geometric shapes as obstacles have been sent to the path planning algorithms instead of sending the whole point cloud.
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Jenkins, Kevin Dean. "The shortest path problem in the plane with obstacles : a graph modeling approach to producing finite search lists of homotopy classes." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26761.
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The problem of finding the shortest path between two points in a plane containing obstacles is considered. The set of such paths is uncountably infinite, making an exhaustive search impossible. This difficulty is overcome by reducing the size of the search space. The search is first restricted to a countably infinite set by focusing attention on the set of homotopy classes. By applying simple optimality principles, a finite list of such classes is obtained whose union contains the shortest path. This process of simplification is accomplished by modeling the topology of the region with a graph. Optimality principles come into play during a graph traversal which is used to produce the finite search list. In addition, a computational investigation of two methods by which homotopy classes can be named is discussed, and properties of the graph models are investigated. The thesis of CPT Andre M. Cuerington, U.S. Army, calculates the actual shortest path using the search list produced here
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Villeret, Olivier. "Les obstacles à la mise en place d'une démarche d'investigation problématisante par des enseignants débutants de sciences physiques : identification et travail en formation." Thesis, Nantes, 2018. http://www.theses.fr/2018NANT2005/document.
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L’ambition de la thèse est d’une part de mettre en évidence les obstacles à la préparation et à la mise en place de séances d’enseignement basées sur la démarche d’investigation pour les enseignants débutants en sciences physiques, d’autre part de proposer et de valider des modalités de formation adaptées. Dix-sept étudiants ont participé à cette recherche visant à la fois à élucider les obstacles et surtout à les travailler lors de séances d’auto-confrontation croisée mobilisant la réflexivité des participants, menées avec le chercheur-formateur (recherche impliquée). Les analyses portent sur la transcription de cinq séances d’enseignement et de formation filmées (préparation, exécution et débriefing) et dix-sept compte rendus écrits de séances. Les obstacles principaux concernent la vraisemblance et l’ouverture du scénario permettant ou non la problématisation, les malentendus (glissement de sens) de tous ordres, les représentations (conceptions) des élèves et de l’enseignant débutant, le guidage trop contraignant pouvant conduire à court-circuiter le travail cognitif des élèves, la survalorisation de certaines phases de la démarche au détriment d’autres, l’absence de travail épistémologique et une institutionnalisation incomplète. Les stratégies pédagogiques sont reliées aux valeurs de l’enseignant (profil pédagogique). Le dispositif mis en place a permis lors des débriefings un travail réflexif sur les pratiques pédagogiques qui a débouché sur des évolutions de celles-ci<br>The aim of the thesis is to highlight the obstacles to the preparation and implementation of teaching sessions based on the inquiry based science teaching for beginners in physical sciences, on the other hand to propose and validate adapted training methods. Seventeen students participated in this research. The aim is to elucidate the obstacles and work them during sessions of cross self-confrontation mobilizing the reflexivity of the participants. The research is conducted with the researcher-trainer (action research). The analyzes focus on the transcription of five filmed instructional and training sessions (preparation, execution and debriefing) and seventeen written minutes of the sessions. The main obstacles concern the likelihood and openness of the scenario, allowing or not the problematization, the misunderstandings (shifting of meaning) of all kinds, the pupils’ and beginner teachers’ representations (conceptions), too restrictive guidance leading to short-circuiting students' cognitive work, overemphasizing certain phases of the process to the detriment of others, lack of epistemological work and incomplete institutionalization. Pedagogical strategies are linked to the values of the teacher (pedagogical profile). The system put in place allowed during the debriefings a reflexive work on the pedagogical practices which led to changes
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Lucanu, Nicolae. "Contribution à l'étude de la diffraction d'une onde électromagnétique plane par des obstacles métalliques en utilisant la méthode itérative basée sur le concept d'onde." Toulouse, INPT, 2001. http://www.theses.fr/2001INPT024H.
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Le travail est basé sur une méthode originale, la méthode itérative basée sur le concept d'onde, utilisée pour étudier des problèmes de diffraction d'une onde électromagnétique plane par des obstacles métalliques placés en espace libre. Le travail est structuré en deux parties, la première dédiée aux obstacles singuliers, la deuxième traitant des cas de diffraction par des structures multiples de géomètrie arbitraire. Des structures diffractantes classiques sont étuduées d'abord, dans le but de valider la méthode itérative. Celle-ci est testée avec succès pour des obstacles ayant une solution analytique exacte au problème de diffraction sous l'incidence d'une onde plane, un cylindre circulaire infini métallique et une sphère métallique. Par la suite, des géométries diffractantes plus complexes sont abordées. La méthode itérative basée sur le concept d'onde est validée pour les cas d'un cylindre infini métallique de section carrée et d'un dipôle métallique placé d'un manière arbitraire par rapport à l'onde incidente. A la fin de la première partie, l'influence du rayonnement d'un point appartenant à une structure diffractante sur les uatres points de même structure est étudiée, d'abord pour un obstacle cylindrique de section circulaire, ensuite pour le cas d'une surface de forme quelconque. La deuxième partie traite des structures diffractantes multiples, comportant plusieurs dipôles métalliques, distribués dans des géométries quelconques. Le problème de la diffraction par deux pôles métalliques est étudié d'abord, en examinant l'influence mutuelle du rayonnement des distributions de densités de courant sur les dipôles. Une comparaison avec la méthode des moments est réalisée pour un nuage de plusieurs dipôles métalliques, en gardant comme priorité la rapidité du calcul numérique, sans affecter la précision des résultats.
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Machado, Júlio César Epifânio. "A sequência didática como estratégia para aprendizagem dos processos físicos nas aulas de geografia do ciclo II do ensino fundamental." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/48/48134/tde-27062013-161524/.
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A presente dissertação insere-se no grupo de estudos dedicado a Metodologia de Ensino de Geografia. Investigamos como ocorre a superação dos obstáculos para aprendizagem de um processo físico elementar nas aulas desta disciplina, organizadas através de uma Sequência Didática. Sua principal contribuição é fornecer subsídios teóricos e metodológicos para o planejamento de aulas de Geografia do Ensino Fundamental II que visem trabalhar com temas e conceitos comuns à Geografia Física. Este trabalho apóia-se em autores clássicos e contemporâneos que versam sobre a aprendizagem, a construção do conhecimento e os conceitos geográficos (PIAGET, 1948/2005; BACHELARD, 1938/2008; MEIRIEU, 2000; CAMILLONI, 1997; CASTELLAR; VILHENA, 2010; MONBEIG, 1956; SANTOS, 1997; ROSS, 2006; dentre outros). Procuramos demonstrar e analisar o processo de aprendizagem de um conceito no contexto de uma rotina escolar e segundo os pressupostos pedagógicos e geográficos adotados, o que nos permitiu estabelecer uma relação entre teoria e prática e, a partir desta experiência, teorizar a prática vivenciada.<br>This present work is part of a study group dedicated to Teaching Methodology of Geography. We investigate how does the overcoming of obstacles to learning an elementary physical process in classes of this discipline, organized through a teaching sequence. Its main contribution is to provide theoretical and methodological planning classes of Geography to Ensino Fundamental II, aiming to work with themes and concepts common to Physical Geography. This work is supported by classic and contemporary authors that deal with learning, construction of knowledge and geographical concepts (PIAGET, 1948/2005; BACHELARD, 1938/2008; MEIRIEU, 2000; CAMILLONI, 1997; CASTELLAR; VILHENA, 2010; MONBEIG, 1956; SANTOS, 1997; ROSS, 2006, among others). We demonstrate and analyze the process of learning a concept in the context of a school routine and according to the geographical and pedagogical assumptions adopted, which allowed us to establish a relationship between theory and practice, and from this experience, theorising our experienced practice.
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Dumont, Peggy Lemauff Pierre. "Les maisons médicales de garde dans les départements de Loire-Atlantique et de Vendée Organisations et objectifs de ces structures; quels obstacles et difficultés rencontrés à leur mise en place ? /." [S.l.] : [s.n.], 2004. http://theses.univ-nantes.fr/thesemed/MEDdumont.pdf.
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Wheeler, David Orton. "Relative Navigation of Micro Air Vehicles in GPS-Degraded Environments." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6609.
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Most micro air vehicles rely heavily on reliable GPS measurements for proper estimation and control, and therefore struggle in GPS-degraded environments. When GPS is not available, the global position and heading of the vehicle is unobservable. This dissertation establishes the theoretical and practical advantages of a relative navigation framework for MAV navigation in GPS-degraded environments. This dissertation explores how the consistency, accuracy, and stability of current navigation approaches degrade during prolonged GPS dropout and in the presence of heading uncertainty. Relative navigation (RN) is presented as an alternative approach that maintains observability by working with respect to a local coordinate frame. RN is compared with several current estimation approaches in a simulation environment and in hardware experiments. While still subject to global drift, RN is shown to produce consistent state estimates and stable control. Estimating relative states requires unique modifications to current estimation approaches. This dissertation further provides a tutorial exposition of the relative multiplicative extended Kalman filter, presenting how to properly ensure observable state estimation while maintaining consistency. The filter is derived using both inertial and body-fixed state definitions and dynamics. Finally, this dissertation presents a series of prolonged flight tests, demonstrating the effectiveness of the relative navigation approach for autonomous GPS-degraded MAV navigation in varied, unknown environments. The system is shown to utilize a variety of vision sensors, work indoors and outdoors, run in real-time with onboard processing, and not require special tuning for particular sensors or environments. Despite leveraging off-the-shelf sensors and algorithms, the flight tests demonstrate stable front-end performance with low drift. The flight tests also demonstrate the onboard generation of a globally consistent, metric, and localized map by identifying and incorporating loop-closure constraints and intermittent GPS measurements. With this map, mission objectives are shown to be autonomously completed.
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Almeida, Nuno Miguel Dias. "Curricular internship in a clinical research unit." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17113.
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Mestrado em Biomedicina Farmacêutica<br>O presente relatório descreve em detalhe as tarefas e atividades desenvolvidas no contexto de um estágio curricular durante o segundo ano do Mestrado em Biomedicina Farmacêutica, da Universidade de Aveiro. Este estágio teve lugar na Unidade de Farmacologia Clínica do Professor Joaquim Ferreira, do Instituto de Medicina Molecular, de 14 de setembro de 2015 a 27 de junho de 2016.
Esta experiência permitiu-me pôr em prática aquilo que aprendi no mestrado durante dez meses. Tive a oportunidade de trabalhar em três áreas diferentes da biomedicina farmacêutica: farmacovigilância, coordenação de ensaios clínicos e gestão de dados.
Durante o estágio, surgiram múltiplas dificuldades e obstáculos. Contudo, consegui ultrapassá-los, melhorando as minhas capacidades profissionais, tais como organização, responsabilidade, comunicação, espírito critico, entre outras qualidades fundamentais para ser um bom profissional.
Em conclusão, este estágio curricular permitiu o meu crescimento, não só como profissional, mas também como pessoa. Considero que tenha sido um desafio concretizado com sucesso e estou consciente que me abriu muitas janelas para a minha carreira futura.<br>This report describes in detail the tasks and activities developed in the context of a curricular internship during the second year of the Master’s degree in Pharmaceutical Medicine of the University of Aveiro. This internship took place in the Professor Joaquim Ferreira’s Clinical Pharmacology Unit (CPU) of the Instituto de Medicina Molecular, from September 14th, 2015 to June 27, 2016.
This experience allowed me to put in practice what I learned from my master’s degree during ten months. I had the opportunity to work in three different areas of pharmaceutical medicine: pharmacovigilance, clinical trial coordination and data management.
During the internship, several difficulties and obstacles showed up. However, I managed to surpass them, improving my professional skills, such as organization, responsibility, communication, critical thinking, among other fundamental qualities to be a good professional.
In conclusion, this curricular internship allowed me to grow up, not only as a professional but also as a person. I think it was a successful challenge and I’m aware that it has opened many windows to future career.
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Wei, Chen Li, and 陳力維. "Numerical Simulation of Heat Transfer Distributions around Plate-Mounted Obstacles." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/40287857458156671754.
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碩士<br>國立成功大學<br>機械工程學系<br>89<br>Abstract
This study presents the numerical Simulation of local heat transfer coefficient distributions around plate-mounted obstacles. The turbulent governing equations are solved by a Control-Volume-based finite-difference method with power-law scheme and the well know turbulence model and its associate wall function to describe the turbulent structure. The velocity and pressure terms of momentum equations are solved by SIMPLE (Semi-Implicit Method for Pressure-Linked Equation) method. An orthogonal non-uniform staggered grids are used for the establishment of mesh grids.
The parameters studied include geometries（cylinder、square cylinder），the entrance flow Reynolds number （Re = 2100、3500、4200、5000）and the obstacles space（S = d , 2d , 4d）; whereas the plate-mounted obstacles characteristic length（H）and hydraulic diameter（d） is fixed at 20mm， and the working medium is air. The flow field numerical calculations indicate that the downstream attachment length becomes shorter when the space between two cylinders decreases. At the same obstacles’ number and space, it is obvious that the downstream wake region of the cylinder obstacle is smaller than that of the square, it means that the drag force of the cylinder obstacle is smaller than that of the square one. In addition，the downstream outlet velocity profile shows no obvious change with different obstacles’ number with the same Reynolds number and geometry conditions.
As to the heat transfer effect，the heat transfer coefficient between two obstacles and around the second obstacle increases with increasing the obstacles’ space. As might be expected, the predicted heat transfer coefficient increasing with increasing Reynolds number from Re = 2100 to 3500 or 4200 due to the increasing of eddy intensity. Surprised, as Reynolds number Re 3500, the enhancement of heat transfer is not significant.
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Porwal, Kamana. "A Posteriori Error Analysis of Discontinuous Galerkin Methods for Elliptic Variational Inequalities." Thesis, 2014. http://hdl.handle.net/2005/3107.
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The main emphasis of this thesis is to study a posteriori error analysis of discontinuous Galerkin (DG) methods for the elliptic variational inequalities. The DG methods have become very pop-ular in the last two decades due to its nature of handling complex geometries, allowing irregular meshes with hanging nodes and different degrees of polynomial approximation on different ele-ments. Moreover they are high order accurate and stable methods. Adaptive algorithms refine the mesh locally in the region where the solution exhibits irregular behaviour and a posteriori error estimates are the main ingredients to steer the adaptive mesh refinement.
The solution of linear elliptic problem exhibits singularities due to change in boundary con-ditions, irregularity of coefficients and reentrant corners in the domain. Apart from this, the solu-tion of variational inequality exhibits additional irregular behaviour due to occurrence of the free boundary (the part of the domain which is a priori unknown and must be found as a component of the solution). In the lack of full elliptic regularity of the solution, uniform refinement is inefficient and it does not yield optimal convergence rate. But adaptive refinement, which is based on the residuals ( or a posteriori error estimator) of the problem, enhance the efficiency by refining the mesh locally and provides the optimal convergence. In this thesis, we derive a posteriori error estimates of the DG methods for the elliptic variational inequalities of the first kind and the second kind.
This thesis contains seven chapters including an introductory chapter and a concluding chap-ter. In the introductory chapter, we review some fundamental preliminary results which will be used in the subsequent analysis. In Chapter 2, a posteriori error estimates for a class of DG meth-ods have been derived for the second order elliptic obstacle problem, which is a prototype for elliptic variational inequalities of the first kind. The analysis of Chapter 2 is carried out for the general obstacle function therefore the error estimator obtained therein involves the min/max func-tion and hence the computation of the error estimator becomes a bit complicated. With a mild assumption on the trace of the obstacle, we have derived a significantly simple and easily com-putable error estimator in Chapter 3. Numerical experiments illustrates that this error estimator indeed behaves better than the error estimator derived in Chapter 2. In Chapter 4, we have carried out a posteriori analysis of DG methods for the Signorini problem which arises from the study of the frictionless contact problems. A nonlinear smoothing map from the DG finite element space to conforming finite element space has been constructed and used extensively, in the analysis of Chapter 2, Chapter 3 and Chapter 4. Also, a common property shared by all DG methods allows us to carry out the analysis in unified setting. In Chapter 5, we study the C0 interior penalty method for the plate frictional contact problem, which is a fourth order variational inequality of the second kind. In this chapter, we have also established the medius analysis along with a posteriori analy-sis. Numerical results have been presented at the end of every chapter to illustrate the theoretical results derived in respective chapters. We discuss the possible extension and future proposal of the work presented in the Chapter 6. In the last chapter, we have documented the FEM codes used in the numerical experiments.
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Yan-WeiCheng and 鄭晏維. "Study on Gravity Compensation and Plane Obstacle Avoidance of 6-axis Robot Motion." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/3w2qky.
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碩士<br>國立成功大學<br>電機工程學系<br>102<br>In recent years, manipulators have been used extensively in the pick-and-place task. This kind of task requires trajectory planning when there are obstacles in the workspace. Generally, trajectory planning for obstacle avoidance is performed by the operator/engineer in advance. However, one of the major drawbacks for this kind of approach is that trajectory planning must be performed again when there is change in the work environment, in which it is time-consuming and a waste of manpower. One of the possible solutions to the aforementioned problems is to use a camera to obtain the image of the obstacle offline, and the use computer vision technique to obtain the position information of the obstacle. Subsequently, we use an obstacle avoidance algorithm to help the manipulator avoid obstacle during a pick-and-place task. Furthermore, setting the operation mode of the manipulator to the torque mode, rather than position mode or velocity mode can help the manipulator detect whether it touches other objects so as to take further measures to prevent from damaging the manipulator. The influence caused by nonlinear terms such as gravity should be considered when the manipulator is operated in the torque mode. As a result, this thesis focuses on the identification of the gravity parameters of the links of the manipulator that experience significant influence by gravity, and subsequently uses these parameters to compensate for gravity. Regarding the obstacle avoidance algorithm, this thesis exploits the artificial potential field to guide the end-effector of the manipulator moving toward the target position in the plane and also avoid obstacles. In addition, the position controller employed in this thesis includes a gravity compensation term and a PD controller. Experimental results verify that the gravity compensation scheme with identified parameters has exhibited decent performances. In addition, the PD controller combined with gravity compensation can yield good position control. Experimental results also verify that using the artificial potential field successfully assists the end-effector of the manipulator in accomplishing plane obstacle avoidance.
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Hsieh, Jui-Chin, and 謝瑞青. "Measurement of Heat Transfer Distributions around Plate－Mounted Obstacles Using Liquid Crystal Image Technique." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/14071122239531656028.
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碩士<br>華梵大學<br>機電工程研究所<br>87<br>In this study, local convective heat transfer was determined from a plate-mounted single obstacle and single array of obstacles along a flat plate with the transient liquid crystal image method. Three geometrical shapes of the obstacle (cylinder, square and diamond) with variations in the obstacle height, spacing, number and Reynolds number of the mainstream are comparatively examined. The obstacle height H is varied with 0.25, 0.5 and 1 hydraulic diameter, while the streamwise pitch between obstacles S sets at 1, 2 or 4 hydraulic diameter. The Reynolds number Re ranges from 2100 to 4200.
The experimental results show that, for a fixed obstacle shape, an increase in the Reynolds number Re from 2100 to 3500 would lead to an increase in the vortex strength, which in turn, causes an enhancement of heat transfer distribution. But as Re≧3500, the effects of Reynolds number on the heat transfer become insignificant. For the case with the pitch between obstacles S=4d, the flow patterns between the obstacles include the reattachment and separation flows. A relatively high value of the heat transfer coefficient occurs at the reattachment point. As for the case with S=2d, the heat transfer distributions between the obstacles are relatively low due to the appearance of the recirculation flow. The heat transfer distribution around the upstream region of the obstacle is affected by the difference in obstacle height. This is due to the fact that an increase in the obstacle height H will enhance the horeshoe vortex strength around the obstacle. The effects of obstacle shape on the heat transfer enhancement at the upstream of the obstacle are the most significant for the case with the square obstacle. The measurements demonstrate that the liquid crystal image method can provide good experimental accuracy and operation convenience.
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Yen, Wen-Cheng, and 顏文成. "The Interaction of a Monopolar Vortex with a 2-D Cylindrical Obstacle on a Beta-plane." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/79750961984419768983.
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Lin, Sheng-Hui, and 林昇輝. "Implementation of a Linear-Time Shortest Path Algorithm on the Euclidean Plane with Obstacles." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/usrtsn.
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碩士<br>國立臺灣海洋大學<br>電機工程學系<br>103<br>In the Euclidean planes with obstacles, the shortest path problem is to find an optimal path between the source and the destination. There are three different approaches to solve this problem, namely, roadmaps, cell decomposition, and potential field. Of the roadmap approaches, visibility graph is considered as one of the most widely used method.
Recently, Jan et al. proposed a novel method based on the concepts of Delaunay triangulation, an improved version of Dijkstra’s algorithm, and Fermat points, to construct a reduced visibility graph and obtained a near-shortest path in the Euclidean plane with O(n log n) time, where n is the number of obstacles [17]. More recently, Jan has further reduced the time complexity to O(n) by applying the concepts of convex hull, enclosing ellipse, and constrained Delaunay triangulation [18]. In this thesis, we present software implementation of this novel algorithm as well as experimental results for performance evaluation. The results show that the average path length obtained by Jan’s algorithm is only 0.92% longer than the shortest one, but the time complexity is optimal in the context of current state of the art.
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Chi, Kai-Hui, and 紀凱暉. "The Evaluation of UKF Approach for 2D-Plane IMU/Camera Indoor Localization System and Obstacle Avoidance Behavior." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/26740850846042355276.
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碩士<br>國立臺灣科技大學<br>自動化及控制研究所<br>100<br>In recent year, autonomous mobile robot has become an important and popular research topic. It is widely used in the application of homecare system, exploring in dangerous, rescue task and military. The foundation of the mobile robot behavior is the obstacle avoidance, and localization system is also same priority which applied for the indoor environment.
In this thesis, the specific indoor environment is the set up as scenario which is applied for homecare service robot and joint robot system. The nonlinear motion of mobile robot and signal state processing of IMU is the two main proposed approaches to overcome. The methodology in framework is illustrated the Unscented Kalman filter to solve the problem about accumulated error of IMU integrate with ceiling omni-directional camera. The main structure of the algorithm executes and updates of the IMU’s nonlinear state output by observing signal from camera. The other part proposes a Neural Network control system that is able to guide the mobile robots traverse through a maze with arbitrary obstacles. For input data, laser range finder is main sensors for passing on information of environment.
The empirical results show the effectiveness and the validity of the obstacle avoidance behavior of Neural Network control strategy. The evaluation of UKF applied on system state of IMU’s output state can be actuality convergence to overcome the accumulated error and finish the goal of localization.
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Chang, Hsi-Tse, and 張惠澤. "SMOOTH TRAJECTORY PLANNING FOR INDUSTRIAL MANIPULATORS ALONG AN EUCLIDEAN OPTIMAL PATH WITH OBSTACLES IN THE PLANE." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/79949475518899635676.
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碩士<br>大同大學<br>電機工程研究所<br>89<br>In this thesis, we proposed an algorithm about the smooth trajectory planning for industrial manipulators along the shortest path with obstacles in the plane. First, an Euclidean shortest path, avoiding obstacles which were well covered by ellipses, was found by our algorithms. A smooth trajectory could be kept by limiting the torque and torque rate of the joints when the manipulator worked along the shortest path. From the Euclidean shortest path, determined by the thesis, we can be sure that the summation of distances is smallest for manipulators working along the Euclidean shortest path. After finding the shortest path, we added two conditions, i.e., the torque and torque rate limits, and a prespecified work could be executed for ensuring that the manipulator could worked quickly and smoothly along the shortest path. For ensuring the smoothness of the trajectory, the manipulator, executing an prespecified work, may spent extra time. Finally, we could get an executing time for the manipulator working smooth along the shortest path with obstacles. The models of the SCORBOT ER VII manipulator and nonholonomic mobile robot are used to illustrate the effectiveness of the proposed algorithm for achieving the tracking purpose.
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"Dynamics and Motion of a Six Degree of Freedom Robot Manipulator." Thesis, 2012. http://hdl.handle.net/10388/ETD-2012-12-871.
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In this thesis, a strategy to accomplish pick-and-place operations using a six degree-of-freedom (DOF) robotic arm attached to a wheeled mobile robot is presented. This research work is part of a bigger project in developing a robotic-assisted nursing to be used in medical settings. The significance of this project relies on the increasing demand for elderly and disabled skilled care assistance which nowadays has become insufficient. Strong efforts have been made to incorporate technology to fulfill these needs.
Several methods were implemented to make a 6-DOF manipulator capable of performing pick-and-place operations. Some of these methods were used to achieve specific tasks such as: solving the inverse kinematics problem, or planning a collision-free path. Other methods, such as forward kinematics description, workspace evaluation, and dexterity analysis, were used to describe the manipulator and its capabilities. The manipulator was accurately described by obtaining the link transformation matrices from each joint using the Denavit-Hartenberg (DH) notations. An Iterative Inverse Kinematics method (IIK) was used to find multiple configurations for the manipulator along a given path. The IIK method was based on the specific geometric characteristic of the manipulator, in which several joints share a common plane. To find admissible solutions along the path, the workspace of the manipulator was considered. Algebraic formulations to obtain the specific workspace of the 6-DOF manipulator on the Cartesian coordinate space were derived from the singular configurations of the manipulator. Local dexterity analysis was also required to identify possible orientations of the end-effector for specific Cartesian coordinate positions. The closed-form expressions for the range of such orientations were derived by adapting an existing dexterity method. Two methods were implemented to plan the free-collision path needed to move an object from one place to another without colliding with an obstacle. Via-points were added to avoid the robot mobile platform and the zones in which the manipulator presented motion difficulties. Finally, the segments located between initial, final, and via-points positions, were connected using straight lines forming a global path. To form the collision-free path, the straight-line were modified to avoid the obstacles that intersected the path.
The effectiveness of the proposed analysis was verified by comparing simulation and experimental results. Three predefined paths were used to evaluate the IIK method. Ten different scenarios with different number and pattern of obstacles were used to verify the efficiency of the entire path planning algorithm. Overall results confirmed the efficiency of the implemented methods for performing pick-and-place operations with a 6-DOF manipulator.
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Wang, Yu-Da, and 王鈺達. "Obstacle Detection and Road Classification Applied to Navigation of Automatic Land Vehicle Based on Back-propagation Neural Network and Ground Plane Stereo Techniques." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/dtyy2x.
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碩士<br>國立臺北科技大學<br>自動化科技研究所<br>100<br>In this thesis, we present an approach for environment recognition in automatic land vehicle (ALV). By using block matching for the two ground plane alignment images, we can obtain the disparity map. In the map, we can clearly detect obstacles from ground plane, and calculate the height and depth information of the obstacles. To sufficient environment information, we can obtain the features of the road (like colors, textures, etc.) from the original image. By the environment information obtained, and using back-propagation neural network (BPNN) to train and classification, the ALV will be able to recognize drivable surface, with a recognition rate of 85%, providing various options for navigation. Due to classification results are only template similar, using 3D information and road features to verify classified image will be able to achieve ALV navigation system. In this study, ALV platform is controlled by a PIC controller, and the controlling instruction is sent from a computer. The motor control system is divided into two parts: one for controlling the direction derived by a servo motor, and the other for controlling the speed of going forward or backward with a DC motor. The proposed ALV system can reach at a rate of 15 frames per second. The ALV system has been performed in NTUT campus to demonstrate the effectiveness of the proposed method.
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Steinmoeller, Derek. "Flow Separation on the β-plane". Thesis, 2009. http://hdl.handle.net/10012/4417.
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In non-rotating fluids, boundary-layer separation occurs when the nearly inviscid flow just outside a viscous boundary-layer experiences an appreciable deceleration due to a region of adverse pressure gradient. The fluid ceases to flow along the boundary due to a flow recirculation region close to the boundary. The flow is then said to be "detached."
In recent decades, attention has shifted to the study of boundary-layer separation in a rotating reference frame due to its significance in Geophysical Fluid Dynamics (GFD). Since the Earth is a rotating sphere, the so-called β-plane approximation f = f0 + βy is often used to account for the inherent meridional variation of the Coriolis parameter, f, while still solving the governing equations on a plane. Numerical simulations of currents on the β-plane have been useful in understanding ocean currents such as the Gulf Stream, the Brazil Current, and the Antarctic Circumpolar Current to name a few.
In this thesis, we first consider the problem of prograde flow past a cylindrical obstacle on the β-plane. The problem is governed by the barotropic vorticity equation and is solved using a numerical method that is a combination of a finite difference method and a spectral method. A modified form of the β-plane approximation is proposed to avoid computational difficulties. Results are given and discussed for flow past a circular cylinder at selected Reynolds numbers (Re) and non-dimensional β-parameters (β^). Results are
then given and discussed for flow past an elliptic cylinder of a fixed aspect ratio (r = 0.2) and at two angles of inclination (90°, 15°) at selected Re and β^. In general, it is found that the β-effect acts to suppress boundary-layer separation and to allow Rossby waves to form in the exterior flow field. In the asymmetrical case of an inclined elliptic cylinder, the β-effect was found to constrain the region of vortex shedding to a small region near the trailing edge of the cylinder. The shed vortices were found to propagate around the trailing edge instead of in the expected downstream direction, as observed in the non-rotating case.
The second problem considered in this thesis is the separation of western boundary currents from a curved coastline. This problem is also governed by the barotropic vorticity equation, and it is solved on an idealized model domain suitable for investigating the effects that boundary curvature has on the tendency of a boundary current to separate. The numerical method employed is a two-dimensional Chebyshev spectral collocation method and yields high order accuracy that helps to better resolve the boundary-layer dynamics in comparison to low-order methods. Results are given for a selection of boundary curvatures, non-dimensional β-parameters (β^), Reynolds numbers (Re), and Munk Numbers (Mu). In general, it is found than an increase in β^ will act to suppress boundary-layer separation. However, a sufficiently sharp obstacle can overcome the β-effect and force the boundary current to separate regardless of the value of β^. It is also found that in the inertial limit (small Mu, large Re) the flow region to the east of the primary boundary current is dominated by strong wave interactions and large eddies which form as a result of shear instabilities. In an interesting case of the inertial limit, strong waves were found to interact with the separation region, causing it to expand and propagate to the east as a large eddy. This idealized the mechanism by which western
boundary currents such as the Gulf Stream generate eddies in the world's oceans.