Browsing by Subject "navigation"
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Item A framework for roadmap-based navigation and sector-based localization of mobile robots(Texas A&M University, 2004-11-15) Kim, JinsuckPersonal robotics applications require autonomous mobile robot navigation methods that are safe, robust, and inexpensive. Two requirements for autonomous use of robots for such applications are an automatic motion planner to select paths and a robust way of ensuring that the robot can follow the selected path given the unavoidable odometer and control errors that must be dealt with for any inexpensive robot. Additional difficulties are faced when there is more than one robot involved. In this dissertation, we describe a new roadmapbased method for mobile robot navigation. It is suitable for partially known indoor environments and requires only inexpensive range sensors. The navigator selects paths from the roadmap and designates localization points on those paths. In particular, the navigator selects feasible paths that are sensitive to the needs of the application (e.g., no sharp turns) and of the localization algorithm (e.g., within sensing range of two features). We present a new sectorbased localizer that is robust in the presence of sensor limitations and unknown obstacles while still maintaining computational efficiency. We extend our approach to teams of robots focusing on quickly sensing ranges from all robots while avoiding sensor crosstalk, and reducing the pose uncertainties of all robots while using a minimal number of sensing rounds. We present experimental results for mobile robots and describe a webbased route planner for the Texas A&M campus that utilizes our navigator.Item An analysis of navigational instruments in the Age of Exploration: 15th century to mid-17th century(Texas A&M University, 2006-04-12) Swanick, Lois AnnDuring the Age of Exploration, navigation evolved from a field filled with superstition into a modern science in Portugal, Spain, and England. The most common navigation instruments utilized and their subsequent innovations are discussed. The refinement of these instruments led to increased accuracy in cartography, safer shipping, and increased trade globally in the period. In order to have the most comprehensive collection of navigation instruments, I investigated 165 shipwrecks dated between 1500 and 1700. Each of these vessels have been located, surveyed, and/or excavated in whole or in part. A comprehensive list of these vessels, compiled for the first time, has been included. This thesis analyzes navigation-related artifacts recovered from 27 of these shipwreck sites. These instruments provide the basis to develop a typology for archaeologists to more closely date these finds. The navigation instruments recovered from the wreck of LaBelle (1686) are discussed in detail. These instruments and related historical documents kept by the navigator provide a more comprehensive picture of the instruments? accuracy and usefulness. This thesis particularly focuses on the nocturnal/planisphere recovered from the site. This unique instrument is one of only four known to exist worldwide and remains accurate enough to be utilized today. Analysis by a modern astronomer has been included, as well as a partial translation of the common names for constellations inscribed on the instrument. These common names provide some important insights into the received knowledge of sailors and non-academic astronomy during this period. It is hoped that this thesis will be of assistance to archaeologists working to identify, study, and appreciate navigational instruments recovered from shipwrecks. With increased documentation and closer dating, these instruments will become a more valuable portion of the archaeological record.Item Instrucci??ica (1587) by Diego Garc?de Palacio: an early nautical handbook from Mexico(2009-05-15) Laanela, Erika ElizabethIn 1587, an ambitious colonial bureaucrat in Mexico City published a handbook titled Instrucci?n n?utica. Although navigational books were common throughout the 16th century, the Instrucci?n n?utica was the first printed volume that included an extensive discussion of ship construction and design, and its publication was thus a significant event in the history of early modern nautical technology. While the work is frequently cited in discussions of 16th-century Spanish ship construction and seafaring, little in-depth analysis of the text has been undertaken to verify its accuracy. In order to understand the significance of the book, a critical evaluation was undertaken of its context and content and of the motivations and background of its author. Analysis of documents written by, about, and to Diego Garc?a de Palacio reveals that he held positions of academic, religious, and political power in New Spain, that his motives for publishing the book were complex, and that he consulted a range of disparate sources. Significantly, archival correspondence suggests that Garc?a de Palacio was an observer and administrator of navigation and ship construction, rather than an expert practitioner. Nonetheless, comparison of the technical content of the book with other sources of information for 16th-century ships and seafaring, including contemporary treatises, iconography, and archaeological materials confirms the overall accuracy of the text. The navigational materials included in the Instrucci?n n?utica reflect information adapted from existing texts, providing a solid overview of the most common techniques of navigation in use at the time. While useful, Garc?a de Palacio?s discussion of ship design was clearly intended for a non-specialist audience. Perhaps the most original technical contributions are his descriptions of the rigging of Spanish ships. The brief discussion of naval strategy is historically significant due to its juxtaposition between the last of the great naval battles fought primarily with boarding tactics, and the movement toward increasing reliance on the broadside. By comparing Garc?a de Palacio?s text to other sources of information, this study has confirmed the reputation of the Instrucci?n n?utica as one of the most comprehensive and accurate written descriptions of 16th-century Spanish seafaring practices.Item On-line optical flow feedback for mobile robot localization/navigation(Texas A&M University, 2004-09-30) Sorensen, David KristinOpen-loop position estimation methods are commonly used in mobile robot applications. Their strength lies in the speed and simplicity with which an estimated position is determined. However, these methods can lead to inaccurate or unreliable estimates. Two methods are developed in this thesis. The first uses a single optical sensor and can accurately estimate position under ideal conditions and when wheel slip perpendicular to the axis of the wheel occurs. A second method which uses two optical sensors is developed which can accurately estimate position even when wheel slip parallel to the axis of the wheel occurs. Location of the optical sensors is investigated in order to minimize errors caused by inaccurate sensor readings. Finally, the method is implemented and tested using a potential field based navigation scheme. Estimates of position were found to be as accurate as dead-reckoning in ideal conditions and much more accurate in cases where kinematic violations occur.Item Optimal Path Generation for Monocular Simultaneous Localization and Mapping(2014-09-01) Roorda, Timothy IsaacMonocular Simultaneous Localization and Mapping (MonoSLAM), a derivative of Simultaneous Localization and Mapping (SLAM), is a navigation method for autonomous vehicles that uses only an inertial measurement unit and a camera to map the environment and localize the vehicle's position within the environment. Prior to this work, multiple different attempts have been made to generate optimal paths for SLAM, but no optimal path work has been performed specifically for MonoSLAM. The author details an optimal path generation (OPG) method designed specifically for MonoSLAM. In MonoSLAM, the vehicle gains useful data when it can detect a change in bearing to objects in the environment (also known as features). The OPG in question maximizes parallax among all visible features in the environment, with the goal of optimizing fuel usage and estimation accuracy. In simulations comparing paths from this OPG method with typical MonoSLAM paths, it is evident that the OPG method produces extremely large fuel savings (up to 98%). These fuel savings come at the expense of estimation accuracy, however the OPG method still produces estimation performance that is acceptable for many applications. Looking forward, this work proves that it is indeed possible to improve upon the paths that are typically used in MonoSLAM. This thesis examines a two-dimensional MonoSLAM simulation only; no hardware implementation is performed.