Scalable Domain Decomposition for Parallel Solution of 3D Finite Element Multibody Rotorcraft Aeromechanics

A specialized mesh partitioner is developed for large-scale multibody three-dimensional finite element models. This partitioner enables modern domain decomposition algorithms to be leveraged for the parallel solution of complex, multibody, three-dimensional finite element-based rotor structural dynamics problems. The partitioner works with any domain decomposition algorithm, but contains special features for FETI-DP, a state-of-the-art iterative substructuring algorithm. The algorithm was implemented into an aeroelastic rotor solver X3D, with several modifications to improve performance. The parallel solver was applied to two practical test cases: the NASA Tiltrotor Aeroacoustic Model (TRAM) and the NASA Rotor Optimization for the Advancement of Mars eXploration (ROAMX) rotor blade. The mesh partitioner was developed from two sets of requirements: one standard to any domain decomposition algorithm and one specific to the FETI-DP method. The main feature of the partitioner is the ability to robustly partition any multibody structure, but with several special features for rotary-wing structures. The NASA TRAM, a 1/4 scale V-22 model, was specially released by NASA as a challenge test case. This model contained four flexible parts, six joints, nearly twenty composite material decks, a fluid-structure interface, and trim control inputs. The solver performance was studied for three test problems of increasing complexity: 1) an elementary beam, 2) the isolated TRAM blade, and 3) the TRAM blade and hub assembly. A key conclusion is that the use of a skyline solver for the coarse problem eliminates the coarse problem scalability barrier. Overall, the principle barrier of computational time that prevented the use of high-fidelity three-dimensional structures in rotorcraft is thus resolved. The two selected cases provided a template for how 3D structures should be used in the future. A detailed aeromechanical analysis of the NASA TRAM rotor was conducted. The solver was validated against experimental results in hover. The stresses in the blade and hub components were examined, illustrating the unique benefit of 3D structures. The NASA ROAMX blade was the first rotor blade to our knowledge designed exclusively with 3D structures. The torsional stability, blade loads, blade deformations, and 3D stresses/strains were evaluated for multiple blade designs before the final selection. The aeroelastic behavior of this blade was studied in steady and unsteady hover. Inertial effects were found to dominate over aerodynamics on Mars. The rotor blade was found to have sufficient factor of safety and damping for all test conditions. Over 20 thousand cases were executed with detailed stresses/strains as means of downselection, demonstrating the efficiency and utility of the parallel solver, and providing a roadmap for its use in future designs

Interface design of educational games for middle school students

The purpose of this report is to identify interface design elements in educational games for a middle school audience. The four games in this report were selected based on their availability to the general public and their reputable developers. The purpose in undertaking this research is to determine interface and interaction conventions in educational games for 11-14 year olds in order to make recommendations to designers and developers. This report identifies the ways each game approaches important features such as art direction, providing feedback, portraying significant events, indicating clickable items, and event timing. It discusses the games’ techniques to guide gameplay. This report also addresses how interface design supports pedagogical goals.Curriculum and Instructio

Collaborative Robotics Strategies for Handling Non-Repetitive Micro-Drilling Tasks Characterized by Low Structural Mechanical Impedance

Mechanical micro-drilling finds widespread use in diverse applications ranging from advanced manufacturing to medical surgery. This dissertation aims to develop techniques that allow programming of robots to perform effective micro-drilling tasks. Accomplishing this goal is faced with several challenges. Micro-drills suffer from frequent breakage caused from variations in drill process parameters. Micro-drilling tasks afford extremely low feed rates and almost zero tolerance for any feed rate variations. The accompanying robot programming task is made difficult as mathematical models that capture the micro-drilling process complexities and sensitive variations in micro-drill parameters are highly difficult to obtain. Therefore, an experimental approach is adopted to identify the feasible parameter space by carrying out a systematic characterization of the tool-specimen interaction that is crucial for understanding the robotic micro-drilling process. The diameter of the hole to be drilled on a material is a primary defining factor for micro-drilling. For the purposes of this dissertation, micro-drills are defined as having a diameter less than or equal to 1 mm. The Sawyer and KUKA collaborative robots that meet the sensitive speed requirements have been chosen for this study. A regression analysis revealed a relationship between feed rate and reaction forces involved in the micro-drilling process that matched the underlying mathematical model of the tool-specimen interactions. Subsequently, this dissertation addresses the problem of destabilization in robotic micro-drilling caused by the low impedance of the collaborative robot’s cantilever structure. A semi-robotic method that combines force-controlled adaptive drill feed rate and human-assisted impedance enhancement strategy is developed to address the destabilization problem. This approach is inspired by the capability of humans to stabilize unstable dynamics while performing contact-based tasks by using selective control of arm mechanical impedance. A human-robot collaborative kinesthetic drilling mode was also developed using the selective compliance capability of the KUKA robot. Experimental results show that the Sawyer and KUKA robots can use the developed strategies to drill micro-holes of diameters up to a minimum of 0.6 mm and 0.2 mm, respectively. Finally, experiments involving drilling in different materials reveal the potential application of the collaborative robotic micro-drilling approach in composite repairs, micro-channels, dental drilling, and bone drilling

Assisted Interaction for Improving Web Accessibility: An Approach Driven and Tested by Userswith Disabilities

148 p.Un porcentaje cada vez mayor de la población mundial depende de la Web para trabajar, socializar, opara informarse entre otras muchas actividades. Los beneficios de la Web son todavía más cruciales paralas personas con discapacidades ya que les permite realizar un sinfín de tareas que en el mundo físico lesestán restringidas debido distintas barreras de accesibilidad. A pesar de sus ventajas, la mayoría depáginas web suelen ignoran las necesidades especiales de las personas con discapacidad, e incluyen undiseño único para todos los usuarios. Existen diversos métodos para combatir este problema, como porejemplo los sistemas de ¿transcoding¿, que transforman automáticamente páginas web inaccesibles enaccesibles. Para mejorar la accesibilidad web a grupos específicos de personas, estos métodos requiereninformación sobre las técnicas de adaptación más adecuadas que deben aplicarse.En esta tesis se han realizado una serie de estudios sobre la idoneidad de diversas técnicas de adaptaciónpara mejorar la navegación web para dos grupos diferentes de personas con discapacidad: personas conmovilidad reducida en miembros superiores y personas con baja visión. Basado en revisionesbibliográficas y estudios observacionales, se han desarrollado diferentes adaptaciones de interfaces web ytécnicas alternativas de interacción, que posteriormente han sido evaluadas a lo largo de varios estudioscon usuarios con necesidades especiales. Mediante análisis cualitativos y cuantitativos del rendimiento yla satisfacción de los participantes, se han evaluado diversas adaptaciones de interfaz y métodosalternativos de interacción. Los resultados han demostrado que las técnicas probadas mejoran el acceso ala Web y que los beneficios varían según la tecnología asistiva usada para acceder al ordenador