No description available.

The objective of the work described in this thesis is the development of a configuration estimation scheme for quasi soft-bodied robots, with the end goal being accurate soft-robot proprioception to enable robotic manipulation of unknown external loads. The first chapter introduces the problem and state-of-the-art modeling methods. The second chapter presents work we did building on previous research on a novel sensing scheme for soft-bodied robotic configuration estimation. The third chapter discusses the development of a geometric shape-sensing model based on overlapping tendon-length measurements. This model is geometrically exact for a body composed of two constant curvature segments in bending. The next chapter discusses our implemention of this model on a real world system and tested in two and three dimensions. We estimated the shape of a 215 mm long robotic segment with less then 3 mm of median error for a set of 50 configurations causing motion in two dimensions and approximately 27 mm of median translational error in three dimensions. The final chapter draws conclusions and proposes future work to allow for full robotic proprioception.

Let X be a planar or one-dimensional Peano continuum. Let E be a Hawaiian Earring with fundamental group H. We show that every homomorphism from H to the fundamental group of X is conjugate to a homomorphism which is induced by a continuous function.

Continuum robots, with the capability of bending and extending at any point along their length mimic the abilities of an octopus arm or an elephant trunk. These manipulators present a number of exciting possibilities. While calculating a static solution for the system has been proven with certain models to produce satisfactory results [1], this approach ignores the significant effects a dynamics solution captures. However, adding time and studying the physical effects produced on a continuum robot involves calculation of the robot’s shape at a number of discrete points. Typically, the separation between points will be very small and thus a solution requires large amounts of computational power. We present a method to improve calculation speed for dynamic problems with the use of CUDA, a framework for parallel GPU computing. GPUs are ideally suited for massively parallel computations because of their multi-processor architecture. Our dynamics solution will take advantage of this parallel environment.

Continuum robots are the biologically inspired robots that mimic the behaviors of mammalian tongues, elephant trunks, and octopus arms. These robots feature a backboneless structure similar to their biological counterparts, such as termed muscular hydrostats. The drawbacks of two existing designs are examined and a new mechanical design that uses a single latex rubber tube as the central member is proposed, providing a design that is both simple and robust. Next, a novel verification procedure is applied to examine the validity of the proposed model in two different domains of applicability. A two-level electrical control scheme enables rapid prototyping and can be used to control the continuum robot remotely with a joystick via a Local Area Network (LAN). Next, a new geometrical approach to solve inverse kinematics for continuum type robot manipulators is introduced. Given the tip of a three-section robot, end-points of section 1 and section 2 are computed, and a complete inverse kinematics solution for a multisection continuum robot is then achieved by applying inverse kinematics to each section continuum trunk. Moreover, the algorithm provides a solution space rather than a single valid solution. Finally, the techniques involved in visualization of AirOctor/OctArm in 3D space in real-time are discussed.The algorithm has been tested with several system topologies.

No description available.

An important part of an aerodynamic design process is optimizing designs to maximize quantities such as lift and the lift-to-drag ratio, in a process known as shape optimization. It is the goal of this thesis to develop and apply understanding of mixed finite element method and sensitivity analysis in a way that sets the foundation for shape optimization. The open-source Incompressible Flow Iterative Solution Software (IFISS) mixed finite element method toolbox for MATLAB developed by Silvester, Elman, and Ramage is used. Meshes are produced for a backward-facing step problem, using built-in tools from IFISS as well as the mesh generation software Gmsh, and grid convergence studies are performed for both sets of meshes along a sampled data line to ensure that the simulations converge asymptotically with increasing mesh resolution. As a preliminary study of sensitivity analysis, analytic sensitivities of velocity components along the backward-facing step data line to inflow velocity parameters are determined and verified using finite difference and complex step sensitivity values. The method is then applied to pressure drag calculated by integrating the pressure over the surface of a circular cylinder in a freestream flow, and verified and validated using published simulation data and experimental data. The sensitivity analysis study is extended to shape optimization, wherein the shape of a circular cylinder is altered and the sensitivities of the pressure drag coefficient to the changes in the cylinder shape are determined and verified. / Master of Science / When looking at designing an aircraft, it is important to consider the forces air flow exerts on the wings. The primary forces of interest for aerodynamic analysis are lift, which generally acts upward perpendicular to the flow of air, and drag, which opposes the motion of the wing through the air. Optimization is the process of developing a design in such a way that a specific quantity, such as lift or drag, is either maximized or minimized. Many methods exist of predicting the behavior of air flow, and various methods of optimization exist which take already existing predictive software and progressively alter the design to try to meet the minimized or maximized objective. This thesis outlines a multi-step effort to modify an open source software such that it could be used for design optimization.

Cellular core structures are the state-of-the-art technology for light weight structures in the aerospace industry. In an aerospace product, sandwich panels with cellular core represent the primary structural component as a given aerospace product may contain a large number of sandwich panels. This reveals the necessity of understanding the mechanical behavior of the cellular core and the impact of that behavior on the overall structural behavior of the sandwich panel, and hence the final aerospace product. As the final aerospace product must go through multiple qualification tests to achieve a final structure that is capable of withstanding all environments possible, analyzing the structure prior to testing is very important to avoid any possible failures and to ensure that the final design is indeed capable of withstanding the loads. To date, due to the lack of full understanding of the mechanical behavior of cellular cores and hence the sandwich panels, there still remains a significant lack of analytical capability to predict the proper behavior of the final product and failures may still occur even with significant effort spent on pre-test analyses. Analyzing cellular core to calculate the equivalent material properties of this type of structure is the only way to properly design the core for sandwich enhanced stiffness to weight ratio of the sandwich panels. A detailed literature review is first conducted to access the current state of development of this research area based on experiment and analysis. Then, one of the recently developed homogenization schemes is chosen to investigate the mechanical behavior of heavy, non-corrugated square cellular core with a potential application in marine structures. The mechanical behavior of the square cellular core is then calculated by applying the displacement approach to a representative unit cell finite element model. The mechanical behavior is then incorporated into sandwich panel finite element model and in an in-house code to test the predicted mechanical properties by comparing the center-of-panel displacement from all analyses to that of a highly detailed model. The research is then expanded to cover three cellular core shapes, hexagonal cores made of corrugated sheets, square cores made of corrugated sheets, and triangular cores. The expansion covers five different cell sizes and twenty one different core densities for each of the core shapes considering light cellular cores for space applications, for a total of 315 detailed studies. The accuracy of the calculated properties for all three core shapes is checked against highly detailed finite element models of sandwich panels. Formulas are then developed to calculate the mechanical properties of the three shapes of cellular cores studied for any core density and any of the five cell sizes. An error analysis is then performed to understand the quality of the predicted equivalent properties considering the panel size to cell size ratio as well as the facesheet thickness to core thickness ratio. The research finally expanded to understand the effect of buckling of the unit cell on the equivalent mechanical property of the cellular core. This part of the research is meant to address the impact of the local buckling that may occur due to impact of any type during the manufacturing, handling or assembly of the sandwich panels. The variation of the equivalent mechanical properties with the increase in transverse compression load, until the first folding of the unit cell is complete, is calculated for each of the three core shapes under investigation. / Ph. D.

Numerical investigations of collisional physics have historically been impeded by the issue of computational expense. While the continuum-kinetic Vlasov-Maxwell-Fokker-Planck system is well-established in theory and has been used as the basis for many approximate fluid equations, simulations utilizing the distribution function are relatively uncommon, due primarily to the high dimensionality of the problem. However, advances in numerical methods are steadily making these models more accessible. In this work, we utilize the Gkeyll framework, which applies a novel, highly efficient discontinuous Galerkin (DG) finite element method to the Vlasov-Maxwell-Fokker-Planck system. We first investigate the Rayleigh-Taylor (RT) instability in a neutral gas in regimes of finite collisionality which are inaccessible to the fluid codes that are traditionally applied to this instability. Utilizing a spatially constant, finite collision frequency, we demonstrate the ability of the Vlasov-Boltzmann model to approach the fluid result at high collision frequency while also accessing a regime of intermediate collisionality in which the RT instability deviates greatly from classic fluid behavior. We then extend upon this finding by choosing a collision frequency that varies spatially, resulting in new dynamics with asymmetric diffusion affecting the development of the RT instability. Having demonstrated the utility of collisional kinetic modeling even in the simple case of a neutral gas with a basic collision operator, we transition to development and implementation of a fully-conservative, recovery-based DG algorithm for the full nonlinear Rosenbluth/Fokker-Planck collision operator (FPO). Details of the novel recovery scheme for the cross-derivatives and conservation enforcement are presented, and we show that the scheme converges and exhibits stability criteria as expected. Finally, the FPO is applied to test cases that demonstrate the importance of accurate handling of the velocity-dependent collision frequency as compared to an approximate model. / Doctor of Philosophy / Under the right conditions, the electrons and ions that comprise the particles in a gas separate, or ionize, forming a plasma. Plasma is the most common state of matter in the universe, existing at a wide range of scales. Whether concerning a supernova, the solar wind, a plume of material ablated by a laser, or a nuclear fusion reactor, all of these plasmas are governed by the same set of rules, with the main differences being which length and time scales are relevant. Understanding the dynamics of these collections of ionized particles offers a unique challenge, as particles interact not only by colliding with one another but through longer-range electromagnetic interactions. A number of methods exist for modeling plasmas, and one must choose which of the many scales in the plasma are relevant in order to make the best choice of model. In this work, we apply the continuum-kinetic method, which captures the statistical effect of individual particle motions while avoiding the noise that arises when tracking individual particles directly. Kinetic methods are not applied nearly as often as fluid methods, primarily because of the computational expense involved in resolving the wide range of scales and accounting for quantities that evolve as a function of both position and velocity. However, recent advances in numerical methods have made continuum-kinetic methods much more accessible. This work utilizes the Gkeyll code framework, which applies a discontinuous Galerkin method, to simulate plasma with a continuum-kinetic model. We begin by considering the Rayleigh-Taylor (RT) instability, which occurs when a heavy fluid is balanced atop a lighter fluid and perturbed, resulting in fluid mixing. The RT instability is ubiquitous in nature and is commonly modeled with fluid methods that assume particle collide with one another with effectively infinite frequency. With the continuum-kinetic method, we demonstrate that situations arise where the collision frequency is finite but the RT instability still grows. In these regimes, the instability growth is no longer well-described by fluid methods, and a kinetic model must be applied to accurately predict its evolution. Following this, we introduce an algorithm that utilizes a novel discontinuous Galerkin (DG) method to model one of the most complex and accurate collision operators for plasmas: the Fokker-Planck operator (FPO). The FPO is notoriously difficult to implement numerically and computationally expensive due to its nonlinear nature, so simulations generally utilize approximate forms rather than the full operator. By applying this DG method, we are able to ensure the numerical FPO implementation maintains many of the desirable properties of the original model while running highly efficiently. We conclude by verifying that the code is stable and highly accurate while reproducing expected results and improvements over simplified collision models.

This thesis is about a potential trade-off between integrity and long-term usability in the choice of file formats for preservation of text documents. Five common formats are discussed: plain text, PDF/A, Office Open XML Document, Open Document Text, and Markdown. The formats are compared with respect to four criteria related to integrity and usability and to the records continuum model: support by widely used software, stability, rendering of contents and reusability. It is concluded that no single format is optimal with respect to all four criteria, when it comes to preserving typical documents in a modern environment, with more or less complex formatting and document structure. Therefore, the feasiblity of using two or more formats for preservation of a single document (e.g. PDF/A combined with Markdown and/or Office Open XML) is discussed. It is necessary to weigh the importance of integrity and long-term usability against the costs of preserving documents in multiple formats. This is a two years master's thesis in Archival Science, Library and Museum studies.