Modern space situational awareness entails the detection, tracking, identification, and characterization of resident space objects. Characterization is typically accomplished through the use of ground and space based sensors that are able to identify some specific physical feature, monitor unique dynamical behaviors, or deduce some information about the material properties of the object. The present investigation considers the characterizaiton aspects of situational awareness from the perspective of a close-proximity formation reconnaissance mission. The present study explores both relative translational and relative rotational motion for deployment of a spacecraft and observation of a resident space object. This investigation is motivated by specific situations in which characterization with ground or fixed space based sensors is insufficient. Instead, one or more vehicles are deployed in the vicinity of the object of interest. These could be, for instance, nano-satellites with imaging sensors. Nano-satellites offer a low-cost and effective technological platform, which makes consideration of the proposed scenario more feasible. Although the motivating application is rooted in space situational awareness, the techniques explored are generally applicable to flight in the vicinity of asteroids, and both cooperative vs. non-cooperative resident space objects. The investigation is initially focused on identifying the key features of the relative dynamics that are relevant to space situational awareness applications. Subsequently, effective spacecraft control techniques are considered to achieve the reconnaissance goals. / text

Compliant mechanism theory permits a procedure called rigidbody replacement, in which two or more rigid links of the mechanism are replaced by a compliant flexure with equivalent motion. Methods for designing flexure with equivalent motion to replace rigid links are detailed in Pseudo-Rigid-Body Models (PRBMs). Such models have previously been developed for planar mechanisms. This thesis develops the first PRBM for spherical mechanisms. In formulating this PRBM for a spherical mechanism, we begin by applying displacements are applied to a curved beam that cause it todeflect in a manner consistent with spherical kinematics. The motion of the beam is calculated using Finite Element Analysis. These results areanalyzed to give the PRBM parameters. These PRBM parameters vary with the arc length and the aspect ratio of the curved beam.

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Conformational selection is the idea that proteins traverse positions on the conformational space represented by their potential energy landscape, and in particular positions considered as local energy minima. Conformational selection a useful concept in ligand binding studies and in exploring the behavior of protein structures within that energy landscape. Often, research that explores protein function requires the generation of conformational ensembles, or collections of protein conformations from a single structure. We describe a method of conformational ensemble generation that uses joint-constrained rigid-body dynamics (an approach that allows for explicit consideration of rigidity) and the elastic network model (providing structurally derived directional guides for the rigid-body model). We test our model on a selection of unbound proteins and examine the structural validity of the resulting ensembles, as well as the ability of such an approach to generate conformations with structural overlaps close to the ligand-bound versions of the proteins.

The aim of this study is to present a design approach for compliant bistable four-link mechanisms. The design constraints are the two positions of the mechanism, the force required to snap between the positions and the fatigue life of the designed mechanism. The theory presented here will be applied to the door lock mechanism used in commercial dishwashers, which is originally designed as a rigid inverted slider crank mechanism snapping between two positions with the force applied by a spring. The mechanism is re-designed as a compliant bistable four-link mechanism and a prototype has been manufactured.

Objetiva-se discutir e explorar as consequências da conservação do momento angular em situações físicas que apresentem dissipação de energia. Frequentemente, sistemas mecânicos dissipativos são omitidos nas formulações matemáticas da mecânica clássica. No entanto, a conservação da energia mecânica é uma idealização drasticamente incompatível, a longos períodos de tempo, com a maioria das situações reais. Apesar de parecer controversa, esta abordagem é compreensível desde que é incluída na dissipação toda a complexidade dos sistemas mecânicos, os quais não podemos modelar completamente. Espera-se assim que os resultados obtidos sejam parcialmente comprovados em experimentos, sendo que a discrepância é atribuída à parte desconhecida do fenômeno, que muitas vezes é considerada irrelevante para fins práticos. Devido à mencionada complexidade de fenômenos dissipativos, a postura adotada nesta dissertação foi analisar específicos exemplos, de natureza distinta, simplificados, que apresentem as duas propriedades em questão. Concentrou-se especialmente no problema de dissipação de energia em corpos deformáveis na ausência de estímulos externos. / The goal of this work is to study physical systems where angular momentum is a conserved quantity while energy is dissipated. It is a common practice among people working on classical mechanics to neglect energy dissipation. While this hypothesis leads to beautiful mathematical theories, it is strongly violated by the majority of real world systems. The physical complexity of the many ways in which energy is dissipated turns the mathematical modelling of dissipative forces troublesome. There is essentially no general mathematical model for dissipative forces in good agreement with a wide range of experiments. This is in contrast to the very few accepted conservative force models: gravity, elasticity and magneto-electricity. The dissipative force model usually varies among the various physical situations. So, in this work several systems where energy is dissipated while angular momentum is conserved will be considered. The main example will be the motion of a deformable body free from external forces and torques.

O presente trabalho dedica-se a uma modelagem da interação entre corpos celestes, em regime Newtoniano, levando-se em consideração as influências que suas deformações e viscosidades internas exercem sobre seus movimentos orbitais e suas velocidades angulares. A abordagem adotada é uma variação do conhecido problema do corpo pseudo-rígido, a qual simplifica drasticamente a determinação dos equilíbrios relativos e torna a questão da dinâmica matematicamente acessível. Com este tratamento, podemos relacionar ou comparar os resultados com aqueles estabelecidos na literatura, dentre eles: formato de equilíbrio de um fluido isolado em rotação, deformação de maré causada pela interação gravitacional e o torque de maré induzido no mesmo. Pela simplicidade do modelo pode-se ainda fazer uma análise qualitativa da dinâmica do sistema e obter estimativas sobre a velocidade com que se aproxima dos equilíbrios. / The present work is devoted to model the interaction among celestial bodies, in a Newtonian regime, but considering the role played by the internal deformation and viscosity on the orbital motion and angular velocities of the components of the system. The work is mainly developed with an alternative approach to the pseudo-rigid body model, which simplifies the determination of the relative equilibria and allows precise conclusions about the dynamics. So, we are able to compare the results of this theory with those established in the literature, namely: the equilibrium shape of an isolated fluid in rotation, the tidal elongation induced by gravitational interaction and the tidal torque. Due to its simplicity, we can further perform a qualitative analysis of the dynamics of the system and estimate the velocity of attraction of the equilibrium states.

This dissertation presents new concepts and methodology in designing shape-morphing structures using bistable elements. Developed using the Pseudo-Rigid-Body Model (PRBM), linear bistable compliant mechanism elements produce predictable and controllable length changes. Step-by-step design procedures are developed to guide the design process of these bistable elements. Two different examples of Shape-Morphing Space Frames (SMSFs) were designed and prototyped utilizing the bistable linear elements in a single-layer grid, in addition to flexures and rigid links, to morph a cylindrical space frame into both a hyperbolic and a spherical space frame. Moreover, bistable unit-cell compliant-mechanism elements were also developed to morph a compact structure from a specific initial shape to a final specific shape. The detailed design of those unit cells were done using Computer-aided design (CAD) software following a novel design procedure to transform a one-degree-of-freedom mechanism into a structure with sufficient compliance within its links to toggle between two chosen stable positions. Two different design examples were investigated in this research and prototyped to demonstrate the ability to morph disks into a hemisphere or a sphere with the structure being stable in both states (disk and sphere).

This thesis addresses the issue of rigid body simulation and possibilities of paralellization using GPU. It describes the basics necessary for implementation of basic physics engine for blocks and technologies which can be used for acceleration. In my thesis, I describe approach which allowed me to gradually accellerate physics simulation using OpenCL. Each significant change is described in its own section and includes measurement results with short summary.

The present work deals with simulation methods for rigid bodies and deformable bodies. In the first chapter you can find research of some methods for simulation of rigid body physics with emphasis on method used in open source physics engine Bullet. In second chapter you can find methods for simulation of deformable bodies, again with emphasis on Bullet physics engine. In last chapter model order reduction technique is presented. This method enables to reduce system of ordinary differential equations. These equations come for example from applying finite element method to partial differential equations describing motion of elastic body. The technique is studied on bar truss systems. Powered by TCPDF (www.tcpdf.org)