Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2005. / "May 2005." Leaf 81 blank. / Includes bibliographical references (leaves 67-70). / The inherent strength of robotic manipulators can be used to assist humans in performing heavy lifting tasks. These robots reduce manpower, reduce fatigue, and increase productivity. This thesis deals with the development of a control system for a robot being built for this purpose. The task for this robot is to lift heavy payloads while performing complex insertion tasks. This task must be completed on the deck of a naval vessel where possible disturbances include wind, rain, poor visibility, and dynamic loads induced by a swaying deck. The primary objective of the controller being designed here is to allow for insertion of the payload despite tight positioning tolerances and disturbances like surface friction, joint friction, and dynamic loads from ship motions. A control structure designed for intuitive interaction between the robot and operator is analyzed and shown to be stable using an established environment interaction model. The controller is shown to perform within established specifications via numerical simulation based on simple user inputs. An additional objective of this controller design is to prevent part jamming during the insertion task. With a large, powerful manipulator, the chances of a jam occurring is high. Without the use of bilateral force feedback, it will be difficult for the operator feel when these jams will occur and there will be no information about how to prevent them. This thesis analyzes the geometry and mechanics of the jamming problem and derives a control system to assist the user in preventing these jams. These methods can be extended to other insertion tasks simply by specifying the appropriate geometry. / by Matthew A. DiCicco. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references. / Anodic bonding is a common way to package silicon with Pyrex. The anodic bonding process requires high temperature, voltage, and moderate pressure to occur. Often, there are also expectations of alignment of features for things such as power or material delivery. The following thesis proposes a design for a die-level anodic bonding apparatus. It consists of a separate module to meet each requirement; a module for heating, aligning, and applying force. The apparatus is capable of heating the MEMS device to over 400⁰C, applying more than 1000V across the device, applying greater than 4MPa of pressure, and aligning to within 0.5[micro]m in two directions to create an accurately aligned anodic bond. The apparatus met all of these functional requirements and is modular. enough to easily be configured for many other die-level anodic bonding situations. / by Christopher Joseph Khan. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 121). / This paper discusses a modification to the Exploration-Exploitation Experts algorithm - (EEE). The EEE is a generalization of the standard experts algorithm which is designed for use in reactive environments. In these problems, the algorithm is only able to learn about the expert that it follows at any given stage. As a result, the convergence rate of the algorithm is heavily dependent on the number of experts which it must consider. We adapt this algorithm for use with a very large set of experts. We do this by capitalizing on the fact that when a set of experts is large, many experts in the set tend to display similarities in behavior. We quantify this similarity with a concept called correlation, and use this correlation information to improve the convergence rate of the algorithm with respect to the number of experts. Experimental results show that given the proper conditions, the convergence rate of the modified algorithm can be independent of the size of the expert space. / by Jeremy Schwartz. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (leaves 141-146). / by Shih-Hung Li. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / Includes bibliographical references (leaves 93-94). / by Michael Yuan Feng. / B.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references. / As the price of energy increases and wind turbine technology matures, it is evident that cost effective designs for floating wind turbines are needed. The next frontier for wind power is the ocean, yet development in near shore waters has been slowed by aesthetic concerns of coastal residents. Going further offshore eliminates these aesthetic concerns and has the additional advantage of stronger and more consistent winds. However, the vast majority of promising locations beyond the view of land are in sufficiently deep water to make building a rigid structure to the ocean floor economically infeasible. Cost effective floating structures are needed to enable wind farm installation in deep water and increase the world's installed base of renewable energy. This thesis presents a parametric approach to the design of these floating structures for offshore wind turbines. It starts with the relevant design concepts from the offshore oil gas industry and presents appropriate combinations of structures and mooring systems that meet the requirements for a generic five mega watt wind turbine. The results of the parametric study are a number of designs that show Pareto fronts for mean square acceleration of the turbine versus multiple cost drivers for the offshore structure. These cost drivers include displacement of the floating structure and total mooring line tension. / by Christopher Tracy. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 65-67). / In this thesis, two new models are introduced for the purposes of (i) locating sites in hillside terrain suitable for central receiver solar thermal plants and (ii) optimization of heliostat field layouts for any terrain. Additionally, optimization of heliostat canting, is presented as an application of the heliostat layout optimization model. Using the site selection model, suitable sites are located based on heliostat field efficiency and average annual insolation. By iteratively defining the receiver location and evaluating the corresponding site efficiency, by sampling elevation data points from within the defined heliostat field boundary, efficiency can be mapped as a function of the receiver location. The case studies presented illustrate the use of the tool for two field configurations, both with ground-level receivers. The heliostat layout optimization model includes a detailed calculation of the annual average optical efficiency accounting for projection losses, shading & blocking, aberration and atmospheric attenuation. The model is based on a discretization of the heliostats and can be viewed as ray tracing with a carefully selected distribution of rays. The prototype implementation is sufficiently fast to allow for field optimization. In addition, inspired by the spirals of the phyllotaxis disc pattern, a new biomimetic placement heuristic is described and evaluated which generates layouts of both higher efficiency and better ground coverage than radially staggered designs. Case studies demonstrate that the new pattern achieves a better trade-off between land area usage and efficiency, i.e., it can reduce the area requirement significantly for any desired efficiency. Finally, heliostat canting is considered. Traditionally, canting has been parabolic, in which the focal point of the heliostat lies on the axis of symmetry. Two alternative off-axis canting methods are compared in this thesis, fixed facet (static) canting in which the facet alignment is optimized for a single design day and time and then rigidly mounted to the frame and dynamic canting in which the facets are actively controlled such that the center of each facet is always perfectly focusing. For both methods, two case studies are considered, a power tower with planar heliostat field and a hillside heliostat field which directs light down to a ground-level salt pond. / by Corey J. Noone. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / 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 (p. 74-77). / The withdrawal and consumption of water at thermoelectric power plants affects regional ecology and supply security of both water and electricity. The existing field data on US power plant water use, however, is of limited granularity and poor quality, hampering efforts to track industry trends and project future scenarios. Furthermore, there is a need for a common quantitative framework on which to evaluate the effects of various technologies on water use at power plants. To address these deficiencies, Part 1 of this thesis develops an analytical system-level generic model (SGEM) of water use at power plants. The S-GEM applies to fossil, nuclear, geothermal and solar thermal plants, using either steam or combined cycles, and outputs water withdrawal and consumption intensity, in liters per megawatt-hour. Two validations of the S-GEM are presented, one against data from the literature for a variety of generation types, the other against field data from coal plants in South Africa. Part 2 of the thesis then focuses on cooling systems, by far the largest consumers of water in most power plants. The water consumption of different cooling systems is placed on a common quantitative basis, enabling direct comparison of water consumption between cooling system types, and examination of the factors that affect water consumption within each cooling system type. The various cost, performance, and environmental impact tradeoffs associated with once-through, pond, wet tower, dry, and hybrid cooling technologies are qualitatively reviewed. Part 3 examines cooling of concentrating solar power (CSP) plants, which presents particular problems: the plants generate high waste heat loads, are usually located in water-scarce areas, and are typically on the margin of economic viability. A case study is conducted to explore the use of indirect dry cooling with cold-side thermal energy storage, in which cooling water is chilled and stored at night, when ambient temperatures are lower and the plant is inactive, and then used the following day. This approach is shown to hold promise for reducing the capital, operational, and performance costs of dry cooling for CSP. / by Michael J. Rutberg. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 84-86). / The purpose of this thesis is to design and validate a controllable energy recovery device with application to photovoltaic powered reverse osmosis (PVRO). The energy consumption of a reverse osmosis plant depends significantly on the efficiency of its energy recovery process. This work presents a concept for a controllable energy recovery process, so that a system can operate optimally based on the incoming water and power characteristics. The design presented here uses a variable nozzle and a Pelton wheel to recover energy from the high pressure concentrated brine exiting the reverse osmosis membrane. The components are designed, analytically modeled using fundamental engineering principles, and experimentally tested. The experimental data is then used to check the validity of the formulated concept models. This research encompasses the modeling and testing of a variable nozzle using a needle valve to control the flow through the nozzle, and also of a Pelton bucket, to examine the effectiveness of the momentum transfer from a high velocity jet to the Pelton wheel. This research is done to examine the feasibility of this concept for potential implementation on a full scale PVRO system. The component validation is performed to prove that the concept is effective and competitive with other options. / by Elizabeth Anne Reed. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 217-227). / Control of micro/nano scale surface structures and properties is crucial to developing novel functional materials. From an engineering point of view, the development of scalable and economical micro/nano-fabrication methods has been in high demand. In this dissertation, electrophoretic deposition (EPD) and breakdown anodization (BDA) are examined for their potential to produce multi-scale structured surfaces. EPD uses electrophoresis to deposit thin films of nanoparticles, dispersed in suspension, onto charged or porous substrates. Depending upon the dispersion stability, the surface roughness can be modulated in order to affect the resulting wettability. BDA can be utilized to alter surface features by employing instabilities during high voltage anodization, which lead to micro scale topography. Different microporous structures are generated depending on electric potential and electrolyte temperature during BDA. A hybrid method employing EPD and BDA results in hierarchical surface structures with both nano/micro scale features. In this work EPD and BDA are utilized for the development of superhydrophobic and superhydrophilic surfaces; sample applications include anti-wetting fabric, capillarity driven flow design, and critical heat flux enhancement. In many applications it is critical to understand how moving liquid water droplets will behave when they encounter these modified surfaces. We investigate drop impingement on porous thin films produced by BDA and EPD in order to understand the effects of surface structure and chemical properties on droplet dynamics. Using dimensional analysis we've discovered a novel dimensionless parameter, named the Washburn- Reynolds number, which can predict the droplet impingement modes. Intriguingly we've also discovered that under certain conditions drop impingement results in gas trapped in the spreading droplet, leading to the generation of aerosol above the droplet when the gas bubbles burst. The Washburn-Reynolds number also largely dictates the aerosol generation process. Our results inform the understanding of dynamic interactions between porous surfaces and liquid drops for applications ranging from droplet microfluidics to aerosol generators. In summary, EPD and BDA provide promising micro and nano-scale fabrication technologies with reasonable control of surface morphology and properties in a cost-effective and time-effective and scalable. / by Young Soo Joung. / Ph. D.