This thesis examines the design and implementation of an extensible objectoriented physics engine framework. The design and implementation consolidates concepts from the wide literature in the field and clearly documents the procedures and methods. Two primary dynamic behaviors are explored: rigid body dynamics and articulated dynamics. A generalized collision response model is built for rigid bodies and articulated structures which can be adapted to other types of behaviors. The framework is designed around the use of interfaces for modularity and easy extensibility. It supports both a standalone physics engine and a supplement to a distributed immersive rendering environment. We present our results as a number of scenarios that demonstrate the viability of the framework. These scenarios include rigid bodies and articulated structures in free-fall, collision with dynamic and static bodies, resting contact, and friction. We show that we can effectively combine different dynamics into one cohesive structure. We also explain how we can efficiently extend current behaviors to develop new ones, such as altering rigid bodies to produce different collision responses or flocking behavior. Additionally, we demonstrate these scenarios in both the standalone and the immersive environment.

The purpose of this thesis was to create a computational wrist model that predicts carpal bone motion in order to investigate the complex kinematics of the human wrist. The tuning of this model was primarily based on in vitro, kinematic measurements of the carpal bones obtained from the same cadaver arm as the geometry for the model was generated. A rigid body spring model of the wrist was built using the kinematic simulation software RecurDynTM 6.1. Surface models of the eight carpal bones, the bases of the five metacarpal bones, and the distal parts of the ulna and radius, all obtained from computed tomography (CT) scans of a cadaver upper limb, were utilized as the geometry for this model. Elastic contact conditions between the rigid bodies modeled the influence of the cartilage layers, and ligamentous structures were constructed using nonlinear, tension-only spring elements. Motion of the wrist was simulated by applying forces to the tendons of the five main wrist muscles modeled. Three wrist motions were simulated: extension, ulnar deviation and radial deviation. The model was mainly tuned by comparing the simulated displacement and orientation of the carpal bones with previously obtained CT-scans of the same cadaver arm in deviated (45 deg ulnar and 15 deg radial), and extended (57 deg) wrist positions. Simulation results for the scaphoid, lunate, capitate, hamate and triquetrum are presented here and provide credible prediction of carpal bone movement. The impact of certain model parameters on simulation results has been investigated by performing sensitivity analyses, and their severity has been documented. The results of the first simulations indicate that this model may assist in future wrist kinematics investigations. However, further optimization and validation are required to define and guarantee the reliability of this model. It is suggested that this rigid body spring model may be part of an interacting framework between in vitro and in vivo investigations, as well as other computational models, in order to improve and complement each biomechanical investigation method. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2007-08-30 16:30:32.543

The AASHTO 1993 Guide for Design of Pavement Structures is the most widely used pavement design method in both Canada and the United States, and is currently used by the Ministry of Transportation of Ontario (MTO) for both flexible and rigid pavement design. Despite its widespread use, the AASHTO 1993 pavement design method has significant limitations stemming primarily from the limited range of conditions observed at the AASHTO Road Test from which its empirical relationships were derived. The Mechanistic-Empirical Pavement Design Guide (MEPDG) was developed to address the perceived limitations of the AASHTO 1993 Guide. Although the MEPDG provides a rational pavement design procedure with a solid foundation in engineering mechanics, a considerable amount of work is required to adapt and validate the MEPDG to Ontario conditions. The purpose of this research was to conduct a comparative analysis of Ontario structural pavement designs using the AASHTO 1993 Guide for Design of Pavement Structures and the Mechanistic-Empirical Pavement Design Guide. Historical flexible, rigid, and asphalt overlay pavement designs completed using the AASHTO 1993 pavement design method for the MTO were evaluated using a two-stage procedure. First, the nationally-calibrated MEPDG pavement distress models were used to predict the performance of the pavements designed using the AASHTO 1993 method. The purpose of this stage of the analysis was to determine whether the two methods predicted pavement performance in a consistent manner across a range of design conditions typical of Ontario. Finally, the AASHTO 1993 and MEPDG methods were compared based on the thickness of the asphalt concrete or Portland cement concrete layers required to satisfy their respective design criteria. The results of the comparative analysis demonstrate that the AASHTO 1993 method generally over-predicted pavement performance relative to the MEPDG for new flexible pavements and asphalt overlays of flexible pavements. The MEPDG predicted that most of the new flexible pavements and asphalt overlays of flexible pavements designed using the AASHTO 1993 method would fail primarily due to permanent deformation and / or roughness. The asphalt layer thicknesses obtained using the MEPDG exceeded the asphalt layer thicknesses obtained using the AASHTO 1993 method, and a poor correlation was observed between the asphalt layer thicknesses obtained using the two methods. Many of the new flexible pavements and asphalt overlays of existing flexible pavements could not be re-designed to meet the MEPDG performance criteria by increasing the asphalt layer thickness. The results of the comparative analysis showed that the AASHTO 1993 method generally under-predicted rigid pavement performance relative to the MEPDG, although the results varied widely between alternative rigid pavement designs. The AASHTO 1993 rigid pavement designs that the MEPDG predicted would not meet the rigid pavement performance criteria generally failed due to pavement roughness. A very poor correlation was observed between the Portland cement concrete layer thicknesses obtained using the MEPDG and AASHTO 1993 design methods. The MEPDG predicted thinner Portland cement concrete layer thicknesses than the AASHTO 1993 design method for most of the rigid pavement designs.

This dissertation describes several techniques to improve performance and controllability of large-scale rigid body simulations. We first describe a statistical simulation method that replaces certain stages of rigid body simulation with a statistically- based approximation. We begin by collecting statistical data regarding changes in linear and angular momentum for collisions of a given object. From the data, we extract a statistical ”signature” for the object, giving a compact representation of the object’s response to collision events. During object simulation, both the collision detection and the collision response calculations are replaced by simpler calculations based on the statistical signature. In addition, based on our statistical simulator, we develop a mixed rigid body simulator that combines an impulse-based with a statistically-based collision response method. This allows us to maintain high accuracy in important parts of the scene while achieving greater efficiency by simplifying less important parts of the simulation. The resulting system gives speedups of more than an order of magnitude on several large rigid body simulations while maintaining high accuracy in key places and capturing overall statistical behavior in other places. Also, we introduce two methods for directing pile behavior to form the desired shapes. To fill up the space inside the desired shapes and maintain the stability of the desired pile shapes, our methods analyze the configurations and status of all objects and properly select some candidates to have their degrees of freedom (DOFs) reduced. Our first method utilizes the idea of angles of repose to perform the analysis. According to the desired angle of repose, we create an additional spatial structure to track the piling status and select suitable objects to reduce their DOFs. In our second method, we adapt equilibrium analysis in a local scheme to find “stable” objects of the stacking structure. Then, we restrict their DOFs by adding constraints on them for stabilizing the structure. Overall, our directing methods generate a wider variety of piled structures than possible with strict physically-based simulation.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 216-237). Also available in electronic version.

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (p. 91-97).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 183-190). Also available via the Internet.

Thesis (Ph.D.)--University of Delaware, 2005. / Principal faculty advisor: Dennis R. Mertz, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed July 8, 2010). PDF text: ix, 195 p. : ill. (chiefly col.) ; 4 Mb. UMI publication number: AAT 3366273. Includes bibliographical references. Also available in microfilm and microfiche formats.

[pt] Este trabalho tem por objetivo apresentar uma introdução à dinâmica de sistemas de multicorpos compostos por partes rígidas e flexíveis, através da exposição das diversas etapas: Modelagem, Simulação e Controle. A modelagem de sistemas de multicorpos é apresentada, atentando para os problemas de representação de rotações, caracterização de deformações dos corpos flexíveis e manipulação simbólica para formulação das equações do movimento. A parametrização de rotações é apresentada utilizando parâmetros clássicos como ângulos de Euler e Bryant, parâmetros de Euler e Rodrigues, assim como, vetor rotação, vetor rotação conforme e quaternios. O problema de singularidade das parametrizações é estudado, através da comparação de diferentes parametrizações. Para a caracterização de deformações dos corpos flexíveis é apresentado o método de modos supostos. A formulação das equações do movimento é apresentada utilizando as equações de Lagrange e Maggi-Kane. O toolbox de manipulação simbólica do MATLAB é utilizado para derivar as equações do movimento. O controle linear de sistemas de multicorpos é apresentado utilizando a representação no espaço de estados. Duas metodologias de projeto de controle são apresentadas: controle via imposição de pólos e controle ótimo. A simulação de sistemas de multicorpos é apresentada por meio de alguns exemplos ilustrativos da dinâmica e do controle de multicorpos, atentando para a escolha do método de integração. Todas as etapas são realizadas no ambiente do MATLAB, utilizando suas funções de manipulação simbólica para a modelagem, suas funções de linearização e controle para o controle e seus algoritmos de integração e funções gráficas para a simulação. / [en] This work intends to present an introduction to the Dynamics of Multibody Systems, with rigid and flexible bodies, by presenting the following stages: Modelization, Control and Simulation. The modelization of multibody systems is presented, exploring finite rotation parametrization, description of deformation of the flexible bodies and symbolic derivation of the equations of motion. Finite rotations parametrization is presented using classical systems of parametrization such as Euler`s and Bryant`s angles, Euler`s and Rodrigues` parameters and conformal rotation vector, rotation vector and quaternions. The problem of singularity of parametrization is studied by the comparison of the various systems of parametrization. The method of assumed modes is presented to describe the deformation of flexible bodies. The formulation of the equations of motion is done using Lagrange`s and Maggi-Kane`s equations. The equations of motion are derived using the MATLAB`s Symbolic Math Toolbox. The state-space linear control of multibody systems is presented. Two different methods are presented to design the control system: eigenvalues imposition and optimal control. The simulation of some numerical examples of multibody systems is presented. An analysis of the integration methods is done. All the computations are done in MATLAB, using the Symbolic Math Toolbox functions to the modelization, the Control Toolbox to the control and the OdeSuite to the integration of the equations of motion.