Department of Civil, Surveying and Environmental Engineering. Bibliography: leaves 246-255

The development of improved numerical methods for computer simulation of high velocity impact dynamics is of importance in a variety of science and engineering fields. The growth of computing capabilities has created a demand for improved parallel algorithms for high velocity impact modeling. In addition, there are selected impact applications where experimentation is very costly, or even impossible (e.g. when certain bioimpact or space debris problems are of interest). This dissertation extends significantly the class of problems where particle-element based impact simulation techniques may be effectively applied in engineering design. This dissertation develops a hybrid particle-finite element method for a general hexahedral mesh. This work included the formulation of a numerical algorithm for the generation of an ellipsoidal particle set for an unstructured hex mesh, and a new interpolation kernel for the density. The discrete model is constructed using thermomechanical Lagrange equations. The formulation is validated via simulation of published impact experiments. / text

In this work, flow through synthetic arrangements of contacting spheres is studied as a model problem for porous media and packed bed type flows. Direct numerical simulations are performed for moderate pore Reynolds numbers in the range, 10 ≤ Re ≤ 600, where non-linear porescale flow features are known to contribute significantly to macroscale properties of engineering interest. To first choose and validate appropriate computational models for this problem, the relative performance of two numerical approaches involving body conforming and non-conforming grids for simulating porescale flows is examined. In the first approach, an unstructured solver is used with tetrahedral meshes, which conform to the boundaries of the porespace. In the second approach, a fictitious domain formulation (Apte et al., 2009. J Comput. Phys. 228 (8), 2712-2738) is used, which employs non-body conforming Cartesian grids and enforces the no-slip conditions on the pore boundaries implicitly through a rigidity constraint force. Detailed grid convergence studies of both steady and unsteady flow through prototypical arrangements of spheres indicate that for a fixed level of uncertainty, significantly lower grid densities may be used with the fictitious domain approach, which also does not require complex grid generation techniques. Next, flows through both random and structured arrangements of spheres are simulated at pore Reynolds numbers in the steady inertial ( 10 ≲ Re ≲ 200) and unsteady inertial (Re ≈ 600) regimes, and used to analyze the characteristics of porescale vortical structures. Even at similar Reynolds numbers, the vortical structures observed in structured and random packings are remarkably different. The interior of the structured packings are dominated by multi-lobed vortex rings structures that align with the principal axes of the packing, but perpendicular to the mean flow. The random packing is dominated by helical vortices, elongated parallel to the mean flow direction. The unsteady dynamics observed in random and structured arrangements are also distinct, and are linked to the behavior of the porescale vortices. Finally, to investigate the existence and behavior of transport barriers in packed beds, a numerical tool is developed to compute high resolution finite-time Lyapunov exponent (FTLE) fields on-the-fly during DNS of unsteady flows. Ridges in this field are known to correspond to Lagrangian Coherent Structures (LCS), which are invariant barriers to transport and form the skeleton of time dependent Lagrangian fluid motion. The algorithm and its implementation into a parallel DNS solver are described in detail and used to explore several flows, including unsteady inertial flow in a random sphere packing. The resulting FTLE fields unambiguously define the boundaries of dynamically distinct porescale features such as counter rotating helical vortices and jets, and capture time dependent phenomena including vortex shedding at the pore level. / Graduation date: 2013

Millions of cranes are used around the world. Because of their wide-spread use in construction industries, boom cranes are an important class of cranes whose performance should be optimized. One limitation of most boom cranes is they are usually attached to a stationary base or a mobile base that is only used for initial positioning and not during operation. This limits the workspace of the boom crane significantly. If a boom crane was attached to a mobile base that could be safely used during lifting operations, then the boom crane workspace could be extended significantly. The problem with using cranes, and in particular mobile cranes, is the large oscillations of the payload that are typically induced when moving the crane. One control strategy that has been used to control oscillation on other types of cranes is called Input Shaping, a command filtering technique that reduces motion-induced vibration in oscillatory systems. This thesis develops a dynamics model for a mobile boom crane and analyzes the difficulty of controlling payload oscillation on a boom crane. Input shaping will shown to be effective for controlling oscillation on boom cranes. A new method for operating a boom crane in Cartesian coordinates will also be shown. This thesis will also detail the design of a small-scale mobile boom crane for experimental and research purposes. A substantial part of this thesis will also focus on the development of new input-shaping methods for nonlinear drive systems commonly found on boom and other types of cranes. An example application of a control system featuring input shaping for an industrial bridge crane will also be discussed.

Cette thèse est située dans le cadre du projet FUI OASIS ayant comme objectif la modélisation d'un processus d'emboutissage optimisé. Le travail consiste essentiellement au développement des algorithmes de contact plus appropriés à ce type de mise en forme. Dans la littérature et pour plusieurs codes de calcul industriels, l'approche NTS (nœud à segment) demeure la plus utilisée pour la résolution d'un problème de contact. Dans certaine configuration, cette méthode présente des insuffisances et un manque de précision. On la remplaçant par l'approche mortier, on arrive à résoudre une gamme assez large de problèmes de contact. La méthode mortier, utilisée au initialement pour un calcul avec décomposition de domaine, a été le centre d'intérêt de plusieurs travaux de recherche pour la modélisation du contact. Dans ce travail, on va regrouper plusieurs méthodes de gestion du contact en les combinant avec l'approche mortier. L'algorithme de résolution, les éléments d'implémentation ainsi quelques exemples de validation présentant une critique des avantages et les limites de chaque techniques sont détaillés dans ce travail afin d'obtenir un support technique pour tous travail ultérieurs avec la méthode mortier. Le principal avantage de la méthode mortier se manifeste dans l'application des conditions de contact sous forme d'intégrale dans l'interface. Bien que cette méthode permette de réduire la différence des contraintes dans l'interface de contact d'un élément à un autre pour obtenir une meilleure continuité de la pression de contact, elle demeure insuffisante dans certaines applications en particulier pour les problèmes en grande déformation. Le lissage des surfaces de contact, qu'on peut appliquer par différentes techniques, présente une solution classique à ce genre de problème en mécanique de contact. L'originalité de ce travail, c'est la combinaison de l'utilisation des courbes B-Spline cubiques pour la description presque exacte de la surface de contact d'un côté avec une formulation avec l'approche mortier pour l'application des conditions de contact d'un autre côté. Cette combinaison forme un duo gagnant permettant de résoudre un problème de contact en grandes déformation. Les termes permettant l'implémentation des différentes techniques de lissage pour la résolution d'un problème de contact sont détaillés. Une attention particulière est accordée au lissage avec les B-Spline Cubiques.Tous les algorithmes détaillés dans ce travail sont implémentés dans un code maison FiEStA. C'est un code de calcul par éléments finis libre en langage C++. Certains développements concernant la loi de comportement hyper-élastique et l'intégralité du module du contact sont développés dans ce travail de thèse. / This thesis is situated in the FUI OASIS project which the objective is the modeling of an optimized stamping process. The work mainly involves the development of the most appropriate contact algorithms such formatting. In the literature and several industrial computing codes, the NTS approach (node to segment) remains the most used for the resolution of a contact problem. In certain configuration, this method has shortcomings and a lack of precision. We replacing it with mortar approach, we manage to solve a broad range of contact problems. The mortar method, used for the initial for calculation using domain decomposition, was the focus of several research projects for the modeling of the contact. In this work, we will consolidate multiple contact formulation methods in combination with mortar approach. The resolution algorithm, the elements of implementation and some examples of validation with a review of the advantages and limitations of each technique are detailed in this work in order to get technical support for subsequent work with the mortar method. The main advantage of the mortar method is in the application of the contact conditions in integral form in the interface. Although this method reduces the difference of the stresses in the contact interface of a component to another to obtain a better continuity of the contact pressure, it is still insufficient in some applications, particularly for large deformation problems. The smoothing of contact surfaces, which can be applied by various techniques, presents a classic solution to this problem in mechanical contact. The originality of this work is the combination of using cubic B-Spline curves for the almost exact description of the contact surface on one side with the use of the mortar approach to the application of the contact conditions on the other hand. This combination forms a winning combination for solving a contact problem in large deformation. The terms allowing the implementation of the different smoothing techniques for solving a problem of contact are detailed. Particular attention is paid to smoothing with Cu bic B-Spline. All algorithms detailed in this work are implemented in a house code 'Fiesta'. This is a free finite elements computer code in C ++. Some developments in the law of hyper-elastic behavior and completeness of the contact module are developed in this thesis.

The thesis deal with programing of algorithm for creating measuring box composed of measuring points. Coordinates of these points will be used for planing trajectory of the robot’s effector. It describes construction of structural model in Solid Works and calculate dynamic model by matrix formalism in MATLAB. In conslusion dynamic model of positioning system is used for the choice of appropriate motors.

Made available in DSpace on 2016-08-31T13:33:46Z (GMT). No. of bitstreams: 1 TayaraCPB_Dissert.pdf: 1984521 bytes, checksum: 5a46c1781124a49b404a083b87b969bd (MD5) Previous issue date: 2015-08-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / With advances in technology and the popularization of the use of Unmanned Aerial Vehicles (UAV's) so does the need to use more robust and more effective control techniques. Among the various types of unmanned aerial vehicles, this paper will focus on quadrotor model, which has a mechanical structure in the form of x, whose ends have an engine and propeller assembly, where the rotation of this group is responsible for the lift and the movements developed by quadrotor. This feeling, aiming to apply drivers that provide stability to the dynamic system. This study aims to conduct mathematical modeling using the Euler-Lagrange. With this, it is proposed a PID controller (Proportional Integral Derivative) to maintain stable the three orientation angles and height to a desired value. The development of the proposed controller will be validated via simulation confirming the application feasibility of the technique presented stability / Com o avanço tecnológico e a popularização do uso dos Veículos Aéreos Não Tripulados (VANT s) cresce também a necessidade do uso de técnicas de controle mais robustas e mais eficazes. Dentre os mais diversos tipos de veículos aéreos não tripulados, este trabalho irá focar no modelo do quadrotor, que possui uma estrutura mecânica em forma de cruz, cujas extremidades têm um conjunto de motor e hélice, onde a rotação desse conjunto é responsável pela força de sustentação e pelos movimentos desenvolvidos pelo mesmo. Objetivando aplicar controladores que proporcione estabilidade ao sistema dinâmico deste veiculo aéreo. O presente trabalho tem como objetivo realizar a modelagem matemática deste sistema usando as equações de Euler-Lagrange. Tendo isso, é proposto um controlador PID (Proporcional Integral Derivativo) para manter os três ângulos de orientação estáveis e a altura em um valor desejado. O desenvolvimento do controlador proposto será validado via simulação confirmando a viabilidade da aplicação da técnica de estabilidade apresentada

No presente trabalho estudamos e analisamos o método do Tubo de Trajetórias, um algoritmo conservativo, explícito, simples, fisicamente intuitivo, semi-Lagrangiano para equação de convecção. Mostramos que o método é incondicionalmente estável, essencialmente não-dispersivo, convergente e acurado de ordem 2 no tempo e no espaço. Soluções numéricas de sistemas e equações diferenciais ordinárias são testadas no contexto do método do Tubo de Trajetórias, com difíceis problemas clássicos. Aplicações são consideradas no âmbito do transporte oceânico e na advecção de frentes atmosféricas. A fim de testar as propriedades conservativas do método estudado, uma estimativa do erro de balanço de massa é usado aqui. Comparações com outras metodologias mostram a superioridade do método do Tubo de Trajetórias. / In the present work we studied and analyzed the Trajectories Tube method, a conservative, explicit, simple, physically intuitive, semi-Lagrangian algorithm for the convection equation. Kinematical aspects of the mechanics of continuous media are essentially the tools used for formulation and feasibility analysis. We showed that this method is unconditionally stable, essentially nondispersive, convergent and accurate of order two in time and space. Computational experiments with non-isochoric and isochoric motions show that the studied method can be used in compressible and incompressible flow. Numerical solutions of systems of ordinary differential equations (necessary conditions for acomplishment of the scheme) are tested in the Trajectories Tube method context, with classical difficult examples. Applications are considered in the ambit of oceanic transport and advection of atmospheric fronts, including the tracer problem within a Stommel gyre and the computation of the Dowell frontogenesis. Comparisions with other methodologies show the superiority of the Trajectories Tube method.

No presente trabalho estudamos e analisamos o método do Tubo de Trajetórias, um algoritmo conservativo, explícito, simples, fisicamente intuitivo, semi-Lagrangiano para equação de convecção. Mostramos que o método é incondicionalmente estável, essencialmente não-dispersivo, convergente e acurado de ordem 2 no tempo e no espaço. Soluções numéricas de sistemas e equações diferenciais ordinárias são testadas no contexto do método do Tubo de Trajetórias, com difíceis problemas clássicos. Aplicações são consideradas no âmbito do transporte oceânico e na advecção de frentes atmosféricas. A fim de testar as propriedades conservativas do método estudado, uma estimativa do erro de balanço de massa é usado aqui. Comparações com outras metodologias mostram a superioridade do método do Tubo de Trajetórias. / In the present work we studied and analyzed the Trajectories Tube method, a conservative, explicit, simple, physically intuitive, semi-Lagrangian algorithm for the convection equation. Kinematical aspects of the mechanics of continuous media are essentially the tools used for formulation and feasibility analysis. We showed that this method is unconditionally stable, essentially nondispersive, convergent and accurate of order two in time and space. Computational experiments with non-isochoric and isochoric motions show that the studied method can be used in compressible and incompressible flow. Numerical solutions of systems of ordinary differential equations (necessary conditions for acomplishment of the scheme) are tested in the Trajectories Tube method context, with classical difficult examples. Applications are considered in the ambit of oceanic transport and advection of atmospheric fronts, including the tracer problem within a Stommel gyre and the computation of the Dowell frontogenesis. Comparisions with other methodologies show the superiority of the Trajectories Tube method.

Infimalfolgen nichtkonvexer Variationsprobleme haben aufgrund feiner Oszillationen häufig keinen starken Grenzwert in Sobolevräumen. Diese Oszillationen haben eine physikalische Bedeutung; Finite-Element-Approximationen können sie jedoch im Allgemeinen nicht auflösen. Relaxationsmethoden ersetzen die nichtkonvexe Energie durch ihre (semi)konvexe Hülle. Das entstehende makroskopische Modell ist degeneriert: es ist nicht strikt konvex und hat eventuell mehrere Minimalstellen. Die fehlende Kontrolle der primalen Variablen führt zu Schwierigkeiten bei der a priori und a posteriori Fehlerschätzung, wie der Zuverlässigkeits- Effizienz-Lücke und fehlender starker Konvergenz. Zur Überwindung dieser Schwierigkeiten erweitern Stabilisierungstechniken die relaxierte Energie um einen diskreten, positiv definiten Term. Bartels et al. (IFB, 2004) wenden Stabilisierung auf zweidimensionale Probleme an und beweisen dabei starke Konvergenz der Gradienten. Dieses Ergebnis ist auf glatte Lösungen und quasi-uniforme Netze beschränkt, was adaptive Netzverfeinerungen ausschließt. Die vorliegende Arbeit behandelt einen modifizierten Stabilisierungsterm und beweist auf unstrukturierten Netzen sowohl Konvergenz der Spannungstensoren, als auch starke Konvergenz der Gradienten für glatte Lösungen. Ferner wird der sogenannte Fluss-Fehlerschätzer hergeleitet und dessen Zuverlässigkeit und Effizienz gezeigt. Für Interface-Probleme mit stückweise glatter Lösung wird eine Verfeinerung des Fehlerschätzers entwickelt, die den Fehler der primalen Variablen und ihres Gradienten beschränkt und so starke Konvergenz der Gradienten sichert. Der verfeinerte Fehlerschätzer konvergiert schneller als der Fluss- Fehlerschätzer, und verringert so die Zuverlässigkeits-Effizienz-Lücke. Numerische Experimente mit fünf Benchmark-Tests der Mikrostruktursimulation und Topologieoptimierung ergänzen und bestätigen die theoretischen Ergebnisse. / Infimising sequences of nonconvex variational problems often do not converge strongly in Sobolev spaces due to fine oscillations. These oscillations are physically meaningful; finite element approximations, however, fail to resolve them in general. Relaxation methods replace the nonconvex energy with its (semi)convex hull. This leads to a macroscopic model which is degenerate in the sense that it is not strictly convex and possibly admits multiple minimisers. The lack of control on the primal variable leads to difficulties in the a priori and a posteriori finite element error analysis, such as the reliability-efficiency gap and no strong convergence. To overcome these difficulties, stabilisation techniques add a discrete positive definite term to the relaxed energy. Bartels et al. (IFB, 2004) apply stabilisation to two-dimensional problems and thereby prove strong convergence of gradients. This result is restricted to smooth solutions and quasi-uniform meshes, which prohibit adaptive mesh refinements. This thesis concerns a modified stabilisation term and proves convergence of the stress and, for smooth solutions, strong convergence of gradients, even on unstructured meshes. Furthermore, the thesis derives the so-called flux error estimator and proves its reliability and efficiency. For interface problems with piecewise smooth solutions, a refined version of this error estimator is developed, which provides control of the error of the primal variable and its gradient and thus yields strong convergence of gradients. The refined error estimator converges faster than the flux error estimator and therefore narrows the reliability-efficiency gap. Numerical experiments with five benchmark examples from computational microstructure and topology optimisation complement and confirm the theoretical results.