Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 203-216). / Rod-like structures are ubiquitous in both nature (e.g. bacterial flagella) and engineering (ropes, cables, pipelines, and Carbon nanotubes), from nanometer to kilometer scale, and often undergo geometrically nonlinear deformation. Due to the slender geometry of the structures, the material strain usually remains in linear elastic limit even though the deformed geometry deviates significantly from the original geometry. The geometric nonlinearities that result from the deformation process pose enormous challenges to traditional analytical and numerical tools. Moreover, it is often unfeasible to perform experiments at the original length-scale of these systems. We overcome these challenges by combining model experiments with cutting-edge computational tools ported from computer graphics, and theoretical analysis towards developing predictive physical understanding of these systems. The prominence of geometry in this class of systems enables the scaling (up or down) of the problem to the desktop scale, which allows for systematic experimental exploration of parameter space. In parallel, we conduct numerical simulations using the Discrete Elastic Rods (DER) method, which was originally developed for the animation industry for special effects of the visually dramatic dynamics of hair, fur, and other rod-like structures. We port DER into engineering as a predictive computational tool and test ride it against our own model experiments. A collection of problems from three a priori unrelated scenarios, at disparate length-scales, are explored. First, as a model for laying of submarine cables onto the seabed (kilometer scale), we consider deployment of elastic rods onto a moving substrate (conveyor belt) and quantify the resulting nonlinear coiling patterns. The DER method is employed to identify the phase boundaries between different patterns and characterize the morphology. Our results are interpreted using a reduced geometric model for the evolution of the position of the contact point with the belt and the curvature of the rod in its neighborhood. This geometric model reproduces all of the coiling patterns, which allows us to establish a universal link between our elastic problem and the analogous patterns obtained when depositing a viscous thread onto a moving surface; a well-known system referred to as the fluid mechanical sewing machine. Secondly, we consider a macroscopic analog model for the locomotion of uni-flagellar bacteria (micron scale) in a viscous fluid. Our precision experiments are compared against numerical simulations that employ the Lighthill's slender body theory (a non-local description of fluid force) and DER, with excellent quantitative agreement without any fitting parameter. A novel mechanical instability is uncovered, whereby the filament buckles above a critical rotation frequency. We then augment our experiments and simulations to include the effect of a no-slip rigid boundary on the locomotion of uni-flagellar bacteria. We find that the propulsive force is strongly affected by the presence of a nearby boundary. Thirdly, we perform precision desktop experiments with overhand knots (centimeter scale) with increasing values for the crossing number (our measure of topology) and characterize their mechanical response through tension-displacement tests. The tensile force required to tighten the knot is governed by an intricate balance between topology, bending, and friction. A reduced theory is developed, which predictively rationalizes the process. / by Mohammad Khalid Jawed. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (p. 145-147). / by Michael Landry Rynerson. / M.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. "September 2018." / Includes bibliographical references (pages 124-128). / In order to support a variety of situations in which students might seek additional prototyping support during project work, resources were designed to utilize a combination of photo and video formats. Annotated images are used to introduce technical language, comprehensive narrated videos are used to show prototyping equipment operation, and short looping animations are used to show detailed steps of prototyping techniques. Providing students with multiple media formats allowed them to choose which resources best suited their support needs. This platform was tested in two product design courses: 2.00b Toy Product Design, an introductory product design course taken mostly by freshman, and 2.744 Product Design, a skills-focused course taken mostly by graduate students. In 2.00b, students complete project work with significant staff supervision, whereas most of the project work in 2.744 is unsupervised. For this reason, testing in these courses provided an opportunity to evaluate the platform in course settings with different supervision models. Usage data showed that around half of the students in each course exhibited activity on the platform, with a core group of 24 students (27% of the student population) in 2.00b and 28 students (35% of the student population) in 2.744 contributing most of the platform activity. To characterize student use of the platform, use case descriptions were collected from students during interview sessions with both 2.744 students (n = 10) and 2.00b students (n = 9). Students cited using the platform to support planning prototypes, for preparing to work in the shop space, for exploring the landscape of available tools and techniques afforded through access to the workshop, and to directly support the execution of prototypes in the workshop. Course staff members had activity on the platform comparable to student activity, and used Designy to prepare for advising students on project work and as a source of multimedia resources for preparing lecture materials. Overall, providing the platform to students removed typical roadblocks to prototyping work, such as limited access to staff and difficulty operationalizing prototyping techniques learned through other means. Although some students prefer support of prototyping efforts through face-to-face interactions, Designy was found to contribute to student feelings of increased confidence and comfort while in the workshop, allowing students to work more efficiently and progress their project work further than if they did not have access to the platform. / by Joshua D. Ramos. / Ph. D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1990. / Includes bibliographical references (leaves 209-214). / by Anthony F. Varone Jr. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987. / Bibliography: leaves 177-179. / by Mark Russell Torpey. / M.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (leaf 24). / The Synchronized Position Hold Engage and Reorient Experimental Satellites (SPHERES) formation flight testbed is being developed at the MIT Space Systems Lab. Through this program, the SSL is developing and testing algorithms for formation flight of spacecraft. Three of the five mini-satellites that have been built will be launched to the ISS for development, testing and primarily, validation of the formation flight algorithms in a zero-gravity environment. The remaining two are designated ground units. Their function is to provide an infrastructure where the bulk of the development and testing aspect of the algorithms are being carried out since resources are more readily accessible. To accomplish this, the MIT SSL has developed air carriages for operation of these mini-satellites (spheres) on a two dimensional table. These air carriages' designs only provide three out the six degrees of freedom that is experienced by a spacecraft in a zero-gravity environment. Therefore, an air carriage that allows for five degrees of freedom to be tested on ground would allow for further testing. / by Jesus Bolivar. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997. / Includes bibliographical references (p. 81-82). / by Norman Peralta. / M.S.

Thesis (S.M. in Ocean Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Includes bibliographical references (p. 87-93). / The Odyssey IV autonomous underwater vehicle (AUV) is the next generation of unmanned subsurface robots from the MIT Sea Grant AUV Laboratory. The Odyssey IV AUV has a novel propulsion system, which includes a pair of azimuthing thrusters for maneuvering in surge and heave. An analytical model was developed to describe the complex nonlinear vehicle dynamics, and experiments were performed to refine this model. The fluid dynamics of unsteady azimuthing marine propulsors are largely unstudied, especially for small vehicles like the Odyssey IV AUV. Experiments suggest that thrust developed by an azimuthing propulsor is dependent on the azimuth angle rate of change, and can substantially affect vehicle dynamics. A simple model capturing the effects of azimuthing on the thruster dynamics is developed, and is shown to improve behavior of the model.The use of azimuthing thrusters presents interesting problems and opportunities in maneuvering and control. Nonlinear model predictive control (MPC) is a technique that consists of the real-time optimization of a nonlinear dynamic system model, with the ability to handle constraints and nonlinearities. In this work, several variations of simulated and experimental MPC-based controllers are investigated. The primary challenge in applying nonlinear MPC to the Odyssey IV is solving the time intensive trajectory optimization problem online. Simulations suggest that MPC is able to capitalize on its knowledge of the system, allowing more aggressive trajectories than a traditional PID controller. / by Lauren Alise Cooney. / S.M.in Ocean Engineering

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 20-21). / In this thesis, I present the design and motion-capture analysis of two previously well-studied dynamic-walking machines, the rimless wheel and the compass gait robot. These robots were the basis for my undergraduate research at the Computer Science/Artificial Intelligence Laboratory (CSAIL) at the Massachusetts Institute of Technology. The rimless wheel is a real-world physical realization built to compare to a long-analyzed model, the simplest example of passive dynamic walking. Despite the seemingly deterministic model, undeniable experimental evidence for unpredictable stochasitic behavior is observed. The compass gait is the second iteration of a previous design by Dr. Fumiya Iida in my laboratory. Both machines are among the most fundamental walking models, and are important for developing energy-efficient dynamic walkers. / by Timothy J. Villabona. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 65-66). / The structure of light around a scene may be contained in a 4-dimensional array known as a light field. This thesis describes methods for acquiring and manipulating light fields for applications in 3-dimensional imaging. By actively sampling parts of the wavefront impinging on a lens, or using microlens arrays and patterned sinusoidal masks to modulate the rays reaching a camera, both the spatial distribution and directionality of light may be captured to produce light fields. Simple depth estimation algorithms using stereo and focus measures are then applied to recover quantitative depth information. Experiments on real-world light fields demonstrate their utility in performing digital refocusing, reconstructing occluded objects as well as accurately estimating depth and shape. The performance of the algorithms developed are discussed theoretically and compared empirically. / by Wenxian Hong. / S.B.