Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 175-181). / Humans possess the remarkable ability to control their four natural limbs in a voluntary, accurate and independent manner. The simultaneous use of two or more limbs allows humans to learn and robustly perform a wide range of complex tasks. Since the use of multiple limbs enables humans to master advanced motor skills, it would be interesting to study whether having additional limbs would enable users to expand their skill set beyond its natural limits. Inspired by this vision, we propose a new form of human augmentation: a wearable robot that augments its user by providing him with an additional set of robotic limbs. We named this new device Supernumerary Robotic Limbs (SRL). However, humans have never had the possibility to control additional, powered limbs besides their natural arms and legs. The main theme of this thesis, besides realizing a prototype of the robot and proving its usefulness in realworld tasks, is demonstrating that humans can voluntarily control additional limbs as if they were a part of their own body. We realized a lightweight (3.5 kg), comfortable prototype of the SRL that can be easily worn by an unassisted user. Two robotic limbs can assist the user in both manufacturing and locomotion tasks. We created control strategies that take advantage of the independence of the robotic limbs, enabling them to provide optimal assistance in specific tasks such as weight support, body stabilization, using powered tools, sitting/standing and dynamic walking. Finally, we developed an EMG-based control interface that enables users to voluntarily control the motion of the robotic limbs, without interfering with the posture of the rest of the body. The new augmentation technology presented in this thesis opens up new possibilities in the field of wearable robotics. The voluntary control of additional robotic limbs falls within the range of motor skills that humans can learn, and enables the acquisition of a new set of complex skills that would not be achievable using only the natural body.. / by Federico Parietti. / Ph. D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991. / Includes bibliographical references (leaves 150-153). / by Christopher Mark Atkinson. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (p. 71-73). / by Nils Olaya Fonstad. / M.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 421-427). / This thesis presents the design and control techniques of a variable reluctance actuator for driving a reticle motion stage in photolithography scanners. The primary thesis contributions include the design and experimental demonstration of a magnetic flux controller that uses a sense coil measurement, the design and experimental demonstration of a novel method to estimate actuator hysteresis in real-time, and the development of an actuator model that incorporates the effects of eddy currents. The reticle stage in a scanning lithography machine requires high accelerations combined with sub-nanometer position accuracy. Reluctance actuators are capable of providing high force densities (force per moving mass) and lower power values relative to the present state-of-the-art Lorentz actuators that are used to drive the reticle stage. However, reluctance actuators are highly nonlinear with both current and air gap. They also display other nonlinear behavior from hysteresis and eddy currents. Linearizing the reluctance actuator is required for the high force accuracy required in the scanning stage. In this thesis, we present a way to linearize the reluctance actuator with flux control using a sense coil as the feedback measurement. Because the sense coil is AC-coupled, we design a low-frequency estimate of the magnetic flux based upon the actuator current and air gap measurements. We combine the low-frequency estimate with the sense coil measurement using a complementary filter pair that provides an estimate of the flux from DC to frequencies of several kHz. For the low-frequency estimate, we develop a novel method for estimating the actuator hysteresis in realtime. For this flux estimator, we use an observer to model the actuator flux which treats the changing air gap as a disturbance to the plant model. The use of an observer allows the identification of a single-variable hysteresis model of actuator current rather than a two-variable hysteresis model of current and air gap. We also introduce a novel way for expressing the actuator hysteresis, whereby we incorporate the linearizing effect of the air gap directly into a Preisach hysteresis model via a change of variables. We demonstrate experimentally that this method is numerically stable in the presence of a dynamically changing gap, in contrast to some alternative methods. We designed and built a reluctance actuator prototype and 1-DoF motion testbed to demonstrate the accuracy of the actuator models and control techniques. We experimentally demonstrated that we can achieve a flux control bandwidth of 4 kHz that is capable of reducing the stiffness of the reluctance actuator to less than 0.012 N/[mu]m for frequencies up to 100 Hz. This results in a force error of less than 0.03% of the full-scale force for a 10 [mu]m air gap disturbance at this frequency. We also demonstrate that the actuator hysteresis model is capable of estimating the actuator flux accurately in the presence of dynamic gap disturbances of at least 35 1m peak-to-peak and with a static offset from the nominal air gap of at least 50 [mu]m. / by Ian MacKenzie. / Ph. D.

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 PDF version of thesis. / Includes bibliographical references (pages 126-137). / Tin (II) sulfide (SnS) is a promising Earth-abundant, non-toxic alternative to commercially available thin-film photovoltaic (PV) materials because of its near-ideal bandgap, high absorption coefficient, and potential for facile manufacturing. However, SnS-based photovoltaic devices have reached a maximum experimental efficiency of only 4.4%, compared to a theoretical maximum of 32%, primarily due to a low minority-carrier lifetime. In this work, I assess the impact of structural defects and anisotropy on the minority-carrier lifetime and other key device parameters, shedding light on the path to high-efficiency SnS-based photovoltaics. SnS thin films are deposited by thermal evaporation in a range of growth temperatures with varying structural defect density. Extended structural defects including intragranular defects and grain boundaries are directly related to minority-carrier collection length using high-resolution correlative electron microscopy. The results suggest that intragranular point defects, as opposed to extended structural defects, are likely responsible for the short minority-carrier lifetimes in present-day SnS films. Inhomogeneities in the polycrystalline SnS thin films due to the anisotropic material properties of SnS may also impact the device performance. Device simulations taking into account the orientation-dependent electron affinity of SnS show that a uniform grain orientation distribution is optimal. As a route toward both uniform grain orientation and low structural defect density, the anisotropic surface energy of SnS is harnessed by growth on a van der Waals-terminated substrate. An enhancement in both orientation uniformity and minority-carrier lifetime is measured, showing a promising path toward the ideal SnS film. Lastly, the process of optimization to reduce structural defect density may be expedited by in-situ characterization of micro- and nanoscale defects under realistic processing conditions. Toward this end, an in-situ temperature stage for synchrotron X-ray spectromicrosopy is developed to track nanoscale defects up to a sample temperature of 600°C. The stage enables previously unattainable in-situ studies of defect kinetics, allowing both a deeper understanding of how process conditions affect defect characteristics and the ability to rapidly optimize process conditions toward a defect-free film. / by Rupak Chakraborty. / Ph. D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 86-89). / The purpose of this thesis is to help Varian Semiconductor Equipment Associates, Inc. (VSEA) to smooth the production and reduce the manufacturing cost. Without an efficient way to track on its high-value components, VSEA thereby spends hundreds of thousands of dollars to respond to customers' fraudulent claims and adds extra burdens to manufacturing teams. RFID system is introduced to improve the traceability of high-value components. By physically applying a RFID tag on a component and associating the tag with necessary information of the component, VSEA is able to avoid accepting a fraudulent claim by providing reliable and accurate record for a particular component. After testing different types of RFID tags and various checking system setups, the RFID system is verified feasible to be implemented in the high-value component tracking. Specially, a guideline of tag placements on different components is generated for reference in further implementation. / by Rui Jia. / M.Eng.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 221-243). / Discovering the genetic causes of common diseases may require scanning for mutations in all of the genes in a million people, a significant undertaking. Such discoveries would revolutionize biotechnology, potentially enabling simple genetic tests for risk and targeted preventative or therapeutic strategies. An increase in throughput of genetic analysis instrumentation by several orders of magnitude is essential to undertake such an ambitious task. In this thesis, progress will be presented towards the creation of such a "mutational spectrometer" instrument containing up to 10,000 capillary channels and enabled with subsystems for loading, separating, and detecting fluorescently-labeled DNA. Challenges include DNA manipulation, optical signal detection, macro/micro design integration, precision alignment and assembly, and thermal control. To manipulate DNA, we have utilized a bioMEMS design platform for interfacing to an array of separation channels that enables electrokinetic biomolecule loading, detection, and fraction collection in independent wells. / (cont.) Signal detection is accomplished by a sensitive (107 molecule limit-of-detection), scalable (to 10,000 independent channels), end-of-column fluorescence detection technology that accommodates tightly packed capillary arrays as required for ultra-high throughput electrophoretic separation. Capillary array assembly and constraint technologies have been developed for 2-D arrays containing as many as 10,000 replaceable capillaries. Thermal control requirements of 0.3 °C over the entire 10,000 channel array are met with a cross-flow water heat exchanger. Additional subsystems for forcing a viscous polymer matrix into the capillaries, and interfacing the capillary array to a fluid reservoir for electrophoresis have also been developed, as required. This work lays the foundation for the realization of a mutational spectrometer instrument that will enable population-wide pangenomic analyses to uncover the genetic causes of common diseases. / by Craig Richard Forest. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003. / Includes bibliographical references (leaves 67-69). / by Abraham Schneider. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 91-94). / A suspension of network-forming, electrically conductive particles imparts electrical conductivity to an otherwise insulating medium. This effect can be used to great effect in many industrial applications. The ability to describe these networks and to predict their physical properties is a key step in designing systems that rely on these properties. In addition, many times these networks are suspended in a flowing fluid, which disrupts existing networks and forms new ones. The extra layer of complexity introduced by flow requires more sophisticated tools to model the effect on the network and its properties. In the first chapter, we derive a model for the full, tensorial effective conductivity of a particle particle network as a function of a local tensor description of the particle network, the "fabric tensor." We validate our model against a large number of computer-generated networks and compare its performance against an analogous existing model in the literature. We show that the model accurately predicts the isotropic magnitude, deviatoric magnitude, and deviatoric direction of a particle network. In the second chapter, we set out to model the effects of flow on a particle network. We propose two frame-indifferent constitutive equations for the evolution of the fabric tensor. We perform conductivity measurements of real flowing carbon black suspensions and fit our models to the results by using the conductivity model derived in chapter 1. We find that our models are able to reproduce out-of-sample experimental results with a high degree of accuracy. / by Tyler J. Olsen. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 43). / In this work, a six-axis load cell based on the geometry of a Stewart platform was developed. Its geometry and functional requirements were motivated by the needs of robotic limbs designed to be attached to human workers to support them in typically unergonomic positions. The sensor can measure forces and torques in six degrees of freedom, and can stably support the worker in various hanging positions while still being sensitive to load measurements in different directions. Furthermore, it is made from inexpensive, commonly available cantilever beam load cells. In the least accurate direction, Mx, our measurements were consistently 20% below the nominal applied load. In the most accurate directions, Fx, My, and Mz, our measurements were consistently within 5% of the nominal applied loads. Performance can be optimized using the condition number of the transformation matrix. The full-scale version of the hex sensor is also designed and optimized based on its condition number. / by Maria Rosa Ruiz. / S.B.