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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Navigation Control & Path Planning for Autonomous Mobile Robots / Navigation Control and Path Planning for Autonomous Mobile Robots

Pütz, Sebastian Clemens Benedikt 11 February 2022 (has links)
Mobile robots need to move in the real world for the majority of tasks. Their control is often intertwined with the tasks they have to solve. Unforeseen events must have an adequate and prompt reaction, in order to solve the corresponding task satisfactorily. A robust system must be able to respond to a variety of events with specific solutions and strategies to keep the system running. Robot navigation control systems are essential for this. In this thesis we present a robot navigation control system that fulfills these requirements: Move Base Flex. Furthermore, the map representation used to model the environment is essential for path planning. Depending on the representation of the map, path planners can solve problems like simple 2D indoor navigation, but also complex rough terrain outdoor navigation with multiple levels and varying slopes, if the corresponding representation can model them accurately. With Move Base Flex, we present a middle layer navigation framework for navigation control, that is map independent at its core. Based on this, we present the Mesh Navigation Stack to master path planning in complex outdoor environments using a developed mesh map to model surfaces in 3D. Finally, to solve path planning in complex outdoor environments, we have developed and integrated the Continuous Vector Field Planner with the aforementioned solutions and evaluated it on five challenging and complex outdoor datasets in simulation and in the real-world. Beyond that, the corresponding developed software packages are open source available and have been released to easily reproduce the provided scientific results.
132

[en] ABOUT THE MEASURE OF MAXIMAL ENTROPY AND HOROSPHERICAL FOLIATIONS OF GEODESIC FLOWS OF COMPACT MANIFOLDS WITHOUT CONJUGATE POINTS / [pt] SOBRE A MEDIDA DE MÁXIMA ENTROPIA E FOLIAÇÕES HORÓSFERICAS DE FLUXOS GEODÉSICOS EM VARIEDADES SEM PONTOS CONJUGADOS

EDHIN FRANKLIN MAMANI CASTILLO 04 November 2022 (has links)
[pt] Nesta tese, estudamos algumas propriedades dinâmicas e geométricas do fluxo geodésico de certas variedades compactas sem pontos conjugados. A tese tem duas partes principais. Primeiro estendemos o trabalho de Gelfert-Ruggiero sobre a existência de um fator expansivo para o fluxo geodésico ao caso de superfícies compactas sem pontos conjugados e gênero maior que um. A idéia principal é definir uma relação de equivalência que colapsa as órbitas bi-asintóticas do fluxo geodésico. Isto induz um fator que preserva o tempo e é semi-conjugado ao fluxo geodésico sob o mapa do quociente. Além disso, o fator é expansivo, topologicamente misto e tem uma estrutura de produto local. Estas propriedades implicam que o fator tem uma única medida de máxima entropia. Levantamos esta medida para o fibrado tangente unitário e nos certificamos de que é a única medida de máxima entropia para o fluxo geodésico. Isto fornece uma prova alternativa do teorema de Climenhaga-Knieper-War para o resultado de unicidade. Na última parte da tese, estendemos alguns resultados de Gelfert e Ruggiero de superfícies compactas do gênero superior e sem pontos conjugados para n-variedades compactas sem pontos conjugados e recobrimento universal Gromov hiperbólico. Assumindo que os fibrados de Green são contínuos e a existência de uma geodésica fechada hiperbólica, mostramos que os fibrados de Green são tangentes às foliações horósfericas. Além disso, as foliações horósfericas são as únicas foliações contínuas do fibrado tangente unitário, invariantes pelo fluxo geodésico e que satisfazem uma condição de transversalidade local. Este fato só foi conhecido para superfícies compactas sem pontos conjugados pelo trabalho de Barbosa-Ruggiero, e em dimensões mais elevadas assumindo a condição mais forte de assíntota limitada pelo trabalho de Eschenburg. / [en] In this thesis, we study some dynamical and geometrical properties of the geodesic flow of certain compact manifolds without conjugate points. The thesis has two main parts. We first extend Gelfert-Ruggiero s work about the existence of an expansive factor for the geodesic flow to the case of compact surfaces without conjugate points and genus greater than one. The main idea is to define an equivalence relation that collapses biasymptotic orbits of the geodesic flow. This induces a factor time-preserving semi-conjugate to the geodesic flow under the quotient map. Moreover, the factor is expansive, topologically mixing and has a local product structure. These properties imply that the factor has a unique measure of maximal entropy. We lift this measure to the unit tangent bundle and make sure that it is the unique measure of maximal entropy for the geodesic flow. This provides an alternative proof of Climenhaga-Knieper-War’s theorem for the uniqueness result. In the last part of the thesis, we extend some results of Gelfert and Ruggiero from compact higher genus surfaces without conjugate points to compact n-manifolds without conjugate points and Gromov hyperbolic universal covering. Assuming that Green bundles are continuous and the existence of a hyperbolic closed geodesic, we show that Green bundles are tangent to the horospherical foliations. Moreover, the horospherical foliations are the only continuous foliations of the unit tangent bundle, invariant by the geodesic flow and satisfying a condition of local transversality. This fact was only known for compact surfaces without conjugate points by Barbosa-Ruggiero s work, and in higher dimensions assuming the stronger condition of bounded asymptote by Eschenburg s work.
133

My MFA Experience

Cuevas Santamaría, Sergio Axel 27 August 2018 (has links)
No description available.
134

AJUSTAMENTO DE LINHA POLIGONAL NO ELIPSÓIDE / TRAVERSE ADJUSTMENT IN THE ELLIPSOID

Bisognin, Márcio Giovane Trentin 26 April 2006 (has links)
Traverses Adjustment in the surface of the ellipsoid with the objectives to guarantee the solution unicity in the transport of curvilinear geodesic coordinates (latitude and longitude) and in the azimuth transport and to get the estimates of quality. It deduces the coordinate transport and the azimuth transport by mean Legendre s series of the geodesic line. This series is based on the Taylor s series, where the argument is the length of the geodesic line. For the practical applications, it has the necessity to effect the truncation of the series and to calculate the function error for the latitude, the function error for the longitude and the function error for the azimuth. In this research, these series are truncated in the derivative third and calculates the express functions error in derivative fourth. It is described the adjustment models based on the least-squares method: combined model with weighted parameters, combined model or mixed model, parametric model or observations equations and correlates model or condition equations model. The practical application is the adjustment by mean parametric model of a traverse measured by the Instituto Brasileiro de Geografia e Estatística (IBGE), constituted of 8 vertices and the 129.661 km length. The localization of errors in the observations is calculated by the Baarda s data snooping test in the last iteration of the adjustment that showed some observations with error. The estimates of quality are in the variance-covariance matrices and calculate the semiaxes of the error ellipse or standard ellipse of each point by means of the spectral decomposition (or Jordan s decomposition) of the submatrices of the variance-covariance matrix of the adjusted parameters (the coordinates). It is important to note that the application of the Legendre s series is satisfactory for short distances until 40km length. The convergence of the series is fast for the adjusted coordinates, where the stopped criterion of the iterations is four decimals in the sexagesimal second arc, where it is obtained from interation second of the adjustment. / Ajustamento de linhas poligonais na superfície do elipsóide com os objetivos de garantir a unicidade de solução no transporte de coordenadas geodésicas curvilíneas (latitude ϕ e longitude λ ) e no transporte de azimute e de obter as estimativas de qualidade. Deduz o transporte de coordenadas e o transporte de azimute pelas séries de Legendre da linha geodésica. Essa série se fundamenta na série de Taylor, em que o argumento é o comprimento da linha geodésica. Para as aplicações práticas, há a necessidade de efetuar o truncamento da série e calcular a função erro para a latitude, função erro para a longitude e função erro para o azimute. Nesta pesquisa, trunca-se a série na derivada terceira e calculam-se as funções erro expressas em derivada quarta. Expõe os modelos de ajustamento fundamentados no método dos mínimos quadrados (MMQ): modelo combinado com ponderação aos parâmetros, modelo combinado ou implícito, modelo paramétrico ou das equações de observação e modelo dos correlatos ou das equações de condição. A aplicação prática é o ajustamento pelo modelo paramétrico de uma linha poligonal medida pelo Instituto Brasileiro de Geografia e Estatística (IBGE), constituída de 8 vértices e de comprimento igual a 129,661 km. A localização de erros nas observações é efetuada pelo teste data snooping de Baarda na última etapa do ajustamento que mostrou algumas observações com erro. As estimativas de qualidade estão nas matrizes variância-covariância (MVC) e calcula-se os semieixos da elipse dos erros (ou elipse padrão) de cada ponto mediante a decomposição espectral (ou decomposição de Jordan) das submatrizes da MVC dos parâmetros (as coordenadas) ajustados. Mostra-se que a aplicação das séries de Legendre é satisfatória para distâncias curtas até 40km. A convergência da série é rápida para as coordenadas ajustadas, onde o critério de parada das iterações seja quatro decimais do segundo de arco em que se atingiu na segunda etapa do ajustamento.
135

Géométrie et dynamique des espaces de configuration / Geometry and dynamics of configuration spaces

Kourganoff, Mickaël 04 December 2015 (has links)
Cette thèse est divisée en trois parties. Dans la première, on étudie des systèmes articulés (mécanismes formés de tiges rigides) dont l'espace ambiant n'est pas le plan, mais diverses variétés riemanniennes. On étudie la question de l'universalité des mécanismes : cette notion correspond à l'idée que toute courbe serait tracée par un sommet d'un mécanisme, et que toute variété différentiable serait l'espace de configuration d'un mécanisme. On étend les théorèmes d'universalité au plan de Minkowski, au plan hyperbolique et enfin à la sphère.Toute surface dans R^3 peut être aplatie selon l'axe des z, et la surface aplatie s'approche d'une table de billard dans R^2. Dans la seconde partie, on montre que, sous certaines hypothèses, le flot géodésique de la surface converge localement uniformément vers le flot de billard. De plus, si le billard est dispersif, les propriétés chaotiques du billard remontent au flot géodésique : on montre qu'il est alors Anosov. En appliquant ce résultat à la théorie des systèmes articulés, on obtient un nouvel exemple de systèmes articulé Anosov, comportant cinq tiges.Dans la troisième partie, on s'intéresse aux variétés munies de connexions localement métriques, c'est-à-dire de connexions qui sont localement des connexions de Levi-Civita de métriques riemanniennes ; on donne dans ce cadre un analogue du théorème de décomposition de De Rham, qui s'applique habituellement aux variétés riemanniennes. Dans le cas où une telle connexion préserve une structure conforme, on montre que cette décomposition comporte au plus deux facteurs ; de plus, lorsqu'il y a exactement deux facteurs, l'un des deux est l'espace euclidien R^q. La démonstration des résultats de cette partie passe par l'étude des feuilletages munis d'une structure de similitude transverse. Sur ces feuilletages, on montre un résultat de rigidité qui peut être vu indépendamment des autres: ils sont soit transversalement plats, soit transversalement riemanniens. / This thesis is divided into three parts. In the first part, we study linkages (mechanisms made of rigid rods) whose ambiant space is no longer the plane, but various Riemannian manifolds. We study the question of the universality of linkages: this notion corresponds to the idea that every curve would be traced out by a vertex of some linkage, and that any differentiable manifold would be the configuration space of some linkage. We extend universality theorems to the Minkowski plane, the hyperbolic plane, and finally the sphere.Any surface in R^3 can be flattened with respect to the z-axis, and the flattened surface gets close to a billiard table in R^2. In the second part, we show that, under some hypotheses, the geodesic flow of the surface converges locally uniformly to the billiard flow. Moreover, if the billiard is dispersing, the chaotic properties of the billiard also apply to the geodesic flow: we show that it is Anosov in this case. By applying this result to the theory of linkages, we obtain a new example of Anosov linkage, made of five rods.In the third part, we first consider manifolds with locally metric connections, that is, connections which are locally Levi-Civita connections of Riemannian metrics; we give in this framework an analog of De Rham's decomposition theorem, which usually applies to Riemannian manifolds. In the case such a connection also preserves a conformal structure, we show that this decomposition has at most two factors; moreover, when there are exactly two factors, one of them is the Euclidean space R^q. The proofs of the results of this part use foliations with transverse similarity structures. On these foliations, we give a rigidity theorem of independant interest: they are either transversally flat, or transversally Riemannian.
136

Geometric approach to multi-scale 3D gesture comparison

Ochoa Mayorga, Victor Manuel 11 1900 (has links)
The present dissertation develops an invariant framework for 3D gesture comparison studies. 3D gesture comparison without Lagrangian models is challenging not only because of the lack of prediction provided by physics, but also because of a dual geometry representation, spatial dimensionality and non-linearity associated to 3D-kinematics. In 3D spaces, it is difficult to compare curves without an alignment operator since it is likely that discrete curves are not synchronized and do not share a common point in space. One has to assume that each and every single trajectory in the space is unique. The common answer is to assert the similitude between two or more trajectories as estimating an average distance error from the aligned curves, provided that the alignment operator is found. In order to avoid the alignment problem, the method uses differential geometry for position and orientation curves. Differential geometry not only reduces the spatial dimensionality but also achieves view invariance. However, the nonlinear signatures may be unbounded or singular. Yet, it is shown that pattern recognition between intrinsic signatures using correlations is robust for position and orientation alike. A new mapping for orientation sequences is introduced in order to treat quaternion and Euclidean intrinsic signatures alike. The new mapping projects a 4D-hyper-sphere for orientations onto a 3D-Euclidean volume. The projection uses the quaternion invariant distance to map rotation sequences into 3D-Euclidean curves. However, quaternion spaces are sectional discrete spaces. The significance is that continuous rotation functions can be only approximated for small angles. Rotation sequences with large angle variations can only be interpolated in discrete sections. The current dissertation introduces two multi-scale approaches that improve numerical stability and bound the signal energy content of the intrinsic signatures. The first is a multilevel least squares curve fitting method similar to Haar wavelet. The second is a geodesic distance anisotropic kernel filter. The methodology testing is carried out on 3D-gestures for obstetrics training. The study quantitatively assess the process of skill acquisition and transfer of manipulating obstetric forceps gestures. The results show that the multi-scale correlations with intrinsic signatures track and evaluate gesture differences between experts and trainees.
137

Geometric approach to multi-scale 3D gesture comparison

Ochoa Mayorga, Victor Manuel Unknown Date
No description available.

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