Sensor distribution for collaborative localization using radio ranging

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008.Includes bibliographical references (p. 119-122).This thesis explores the localization of a group of networked agents using range measurements between themselves in a global reference frame. While operating in an environment with sparse Global Positioning System availability and intermittent inter-agent range measurements, additional sensors may be needed to maintain a given level of position accuracy. This research explores the balance between penalties associated with the addition of sensors and the ability to localize all agents to a specified accuracy. The problem is defined as an optimization formulation that minimizes the cost of additional sensors over the group while requiring accurate positioning knowledge for all agents. The first result of this thesis is a novel method for solving the posed optimization problem. This method avoids searching all possible instrumentations by exploiting structure in the problem: testing a single sensor configuration for localization accuracy sometimes allows for implicit elimination of multiple configurations. Discerning the best configuration to test for localization accuracy decreases the re- quired search time to solve the optimization problem. The second contribution of this thesis comes from the application of the optimization's search procedure to problem of distributing inertial measurement units to a group of agents. The effects of various environmental conditions on the required distribution of inertial measurement units are investigated.by Benjamin Alfred S. Werner.S.M

The effect of compositional and geometrical changes to the bending strength of the Ghanaian ceramic pot filter

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010."June 2010." Cataloged from PDF version of thesis.Includes bibliographical references (p. 97-100).Pure Home Water (PHW) is a non-profit organization with the goal of providing safe drinking water through household water treatment and storage (HWTS) to the inhabitants of Ghana, particularly in the Northern Region. To this end, PHW has pursued the distribution and training in the use of the Kosim ceramic pot filter (CPF), and now wishes to pursue its manufacture. Laboratory studies have found the CPF to be between 97.8 and 100% efficient in the removal of E. coil bacteria. One of the main reasons for a household's discontinued use of the CPF is breakage. In a follow up monitoring of 1,000 homes receiving CPFs after an emergency flood distribution in 2008, the rate of breakage was found to be 12%. To address this critical problem, the author performed a three-point bending test on rectangular-prism clay samples with varying recipes and thicknesses in an attempt to determine bending strengths associated with the recipes with the aim of moderating the lip failure due to the possible failure mechanism of bending stress. Filter recipes were assigned numbers 1 through 14 based on combustible type, presence or absence of grog, combustible volume, and manufacturing process. The recipes which incorporated only fine, sieved combustible materials yielded the highest mean bending strengths. Statistically significant decreases in bending strength were realized with the increase of combustible mass. The inclusion of grog was generally found to have no statistically significant impact on the bending strength. Experimentally observed gains in bending strength with increased thickness supported theoretical strength gains with the square of the thickness. The variable of firing condition was found to be a significant but unquantifiable variable in the bending strength of the samples. In all cases, the lower bound of a 95% confidence interval of the mean bending strength of the materials was found to exceed the expected bending stress on the filter lip due to predicted loading conditions. It is recommended that PHW pursue the manufacture of a fine-and-waste rice husk recipe with a 3:8 combustible-to-clay ratio without the inclusion of grog. It is recommended that the lip of the filter be thickened to 25 mm. It is recommended that pyrometric cones be placed in the spy-hole and door of the kiln during each firing and monitored once an hour until the guide cone bends, and once every fifteen minutes thereafter until the firing cone bends, at which time firing should cease. It is recommended that consultation with kiln designer Manny Hernandez be maintained so as to create even firing conditions within the kiln.by Travis Watters.M.Eng

Probabilistic state estimation in regimes of nonlinear error growth

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2005.Includes bibliographical references (p. 273-286).State estimation, or data assimilation as it is often called, is a key component of numerical weather prediction (NWP). Nearly all implementable methods of state estimation suitable for NWP are forced to assume that errors remain in regimes of linear error growth and retain distributions of Gaussian uncertainty, yet nonlinear systems like the atmosphere can readily allow regimes of nonlinear error growth and, in turn, produce distributions of non- Gaussian uncertainty. State-of-the-art, ensemble-based methods of state estimation suitable for NWP are examined to gauge the consequences and relevance of violating the linear error growth assumption. For quite generic sources of non-Gaussian uncertainty, the methods are observed to fail, as they must, and the obtained analyses become probabilistically unreliable before becoming inaccurate. The mispositioning of coherent features is identified as a specific, geophysically relevant source of non-Gaussian uncertainty that can easily cause the state-of-the-art methods of state estimation to fail. However, an understanding of relevant phenomenology sometimes allows these same methods to remain successful owing to an available redefinition of the involved errors. The redefinition is phrased as an alternative error model. It is recognized and exploited that non-Gaussian additive Eulerian errors can come from Gaussian Lagrangian position errors. A two-step, augmented state vector approach is developed that is suitable for use with coherent features and that relies only on implementable methods of state estimation.(cont.) By combining the dual Eulerian and Lagrangian state information into one vector, an ensemble can approximate their covariance, thus allowing each component's uncertainty to be reduced. The first step of the two-step approach reduces the feature position errors in an effort to render the residual additive errors Gaussian, thereby allowing the second step of an implementable state estimation method to proceed successfully. Philosophically, the two-step approach uses physical knowledge of the problem (as phrased by the error model) to compensate for neglected important non-Gaussian uncertainty structure in the state estimation process. The proposed two-step approach successfully allows use of implementable methods of state estimation to obtain probabilistically reliable analyses in regimes of nonlinear error growth, something unavailable using current standards.by W. Gregory Lawson.Ph.D

Untethered human motion recognition for a multimodal interface

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 55-58).This thesis used machine learning techniques to extract useful information about human body articulations. First, it presents a learning approach to model non-linear constraints; a support vector classifier is trained from motion capture data to model the boundary of the space of valid poses. Next, it proposes a system that incorporates body tracking and gesture recognition for an untethered human-computer interface. The detection step utilizes an SVM to identify periods of gesture activity. The classification step uses gesture-specific Hidden Markov Models (HMMs) to determine which gesture was performed at any time period, and to extract the parameters of those gestures. Several experiments were performed to verify the effectiveness of these techniques with encouraging results.by Teresa H. Ko.M.Eng

1999 Flight Mechanics Symposium

This conference publication includes papers and abstracts presented at the Flight Mechanics Symposium held on May 18-20, 1999. Sponsored by the Guidance, Navigation and Control Center of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

Self consistent bathymetric mapping from robotic vehicles in the deep ocean

Submitted In partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution June 2005Obtaining accurate and repeatable navigation for robotic vehicles in the deep ocean is difficult and consequently a limiting factor when constructing vehicle-based bathymetric maps. This thesis presents a methodology to produce self-consistent maps and simultaneously improve vehicle position estimation by exploiting accurate local navigation and utilizing terrain relative measurements. It is common for errors in the vehicle position estimate to far exceed the errors associated with the acoustic range sensor. This disparity creates inconsistency when an area is imaged multiple times and causes artifacts that distort map integrity. Our technique utilizes small terrain "submaps" that can be pairwise registered and used to additionally constrain the vehicle position estimates in accordance with actual bottom topography. A delayed state Kalman filter is used to incorporate these sub-map registrations as relative position measurements between previously visited vehicle locations. The archiving of previous positions in a filter state vector allows for continual adjustment of the sub-map locations. The terrain registration is accomplished using a two dimensional correlation and a six degree of freedom point cloud alignment method tailored for bathymetric data. The complete bathymetric map is then created from the union of all sub-maps that have been aligned in a consistent manner. Experimental results from the fully automated processing of a multibeam survey over the TAG hydrothermal structure at the Mid-Atlantic ridge are presented to validate the proposed method.This work was funded by the CenSSIS ERC of the Nation Science Foundation under grant EEC-9986821 and in part by the Woods Hole Oceanographic Institution through a grant from the Penzance Foundation

Reconstruction of the surface of the Sun from stereoscopic images

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

The development of high-speed PIV techniques and their application to jet noise measurement

This thesis describes the design, development and deployment of a high-speed jet flow measurement system. The apparatus was created in response to the need to collect a large quantity of statistically-converged aerodynamic data from a series of commercial turbofan engine models. This acquisition was performed in conjunction with acoustic measurements as part of the ED CoJeN project to investigate jet noise production, and associated noise reduction techniques. Particle Image Velocimetry is a well established flow measurement technique, but its application outside of the laboratory can be limited by a relatively low sample rate and' the need to operate in a hostile environment. This thesis presents a multiple camera technique - used as the basis for the j et measurement system - that is capable of acquiring both time-series PIV data at MHz rates, and continuous, statistically independent measurements at up to 14 Hz. The resultant PIV measurement rig was therefore capable of acquiring time-averaged velocity and turbulence data from the whole of a 110 scale coaxial engine exhaust plume (down to 4m or 20D) in no more than 1 hour. The -500aC Mach:5 0.9 jets were also scanned volumetrically in order to check the spatial alignment of the nozzle and flow streams,.and all PIV measurements were synchronised to simultaneous LDA acquisition, thus enabling the data to be validated. Finally, the cameras were used to acquire novel6-frame time-series data at:5 330 kHz, which was used to calculate time-space correlations within the exhaust. By providing a highly automated and completely remote-controlled system, the exhaust measurements could be repeated over 3 operating conditions and 2 nozzle geometries, thereby providing a comprehensive description of the flow field. The data, having been systematically post-processed, has been shown to agree well with concurrent measurements, and it will now be used to validate CFD models of coaxial jet flow. By improving the quality of computational flow prediction in this way, the time taken to design and test quieter jet engines will be significantly reduced.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Efficient data structures for piecewise-smooth video processing

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 95-102).A number of useful image and video processing techniques, ranging from low level operations such as denoising and detail enhancement to higher level methods such as object manipulation and special effects, rely on piecewise-smooth functions computed from the input data. In this thesis, we present two computationally efficient data structures for representing piecewise-smooth visual information and demonstrate how they can dramatically simplify and accelerate a variety of video processing algorithms. We start by introducing the bilateral grid, an image representation that explicitly accounts for intensity edges. By interpreting brightness values as Euclidean coordinates, the bilateral grid enables simple expressions for edge-aware filters. Smooth functions defined on the bilateral grid are piecewise-smooth in image space. Within this framework, we derive efficient reinterpretations of a number of edge-aware filters commonly used in computational photography as operations on the bilateral grid, including the bilateral filter, edgeaware scattered data interpolation, and local histogram equalization. We also show how these techniques can be easily parallelized onto modern graphics hardware for real-time processing of high definition video. The second data structure we introduce is the video mesh, designed as a flexible central data structure for general-purpose video editing. It represents objects in a video sequence as 2.5D "paper cutouts" and allows interactive editing of moving objects and modeling of depth, which enables 3D effects and post-exposure camera control. In our representation, we assume that motion and depth are piecewise-smooth, and encode them sparsely as a set of points tracked over time. The video mesh is a triangulation over this point set and per-pixel information is obtained by interpolation. To handle occlusions and detailed object boundaries, we rely on the user to rotoscope the scene at a sparse set of frames using spline curves. We introduce an algorithm to robustly and automatically cut the mesh into local layers with proper occlusion topology, and propagate the splines to the remaining frames. Object boundaries are refined with per-pixel alpha mattes. At its core, the video mesh is a collection of texture-mapped triangles, which we can edit and render interactively using graphics hardware. We demonstrate the effectiveness of our representation with special effects such as 3D viewpoint changes, object insertion, depthof- field manipulation, and 2D to 3D video conversion.by Jiawen Chen.Ph.D