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Cette thèse propose une méthode de navigation fondée sur les risques, y compris à la fois la notion traditionnelle de risque de collision et la notion de risque de perturbation. Avec la demande croissante d'assistance à la mobilité personnelle et de la robotique de services mobiles, les robots et les gens doivent partager les mêmes espaces physiques et suivre les mêmes conventions sociales. Les robots doivent respecter les contraintes de proximité, mais aussi respecter les gens qui interagissent. Par exemple, ils ne doivent pas briser l'interaction entre les gens qui parlent, à moins que la tâche du robot est de prendre part à la conversation. Dans ce cas, il doit être en mesure de rejoindre le groupe à l'aide d'un comportement socialement adapté. Le système de navigation socialement conscient proposée dans cette thèse intègre à la fois l'évaluation d'un risque de collision en utilisant des modèles prédictifs d'obstacles mobiles, et une évaluation de conformité avec les conventions sociales. La gestion humaine de l'espace (espace personnel, o-espace, espace d'activité ...) inspirée de la sociologie et la littérature robotique sociale est intégré, mais aussi des modèles de comportement qui permettent au robot la realisation de une prédiction à moyen terme des positions de l'homme. Les résultats de la simulation et des expériences sur un fauteuil roulant robotisé donnent validite a la méthode en montrant que notre robot est capable de naviguer dans un environnement dynamique en évitant les collisions avec des obstacles et des personnes et, en même temps, en réduisant l'inconfort chez les personnes en respectant les espaces mentionnés ci-dessus. / This thesis proposes a risk-based navigation method including both the traditional notion of risk of collision and the notion of risk of disturbance. With the growing demand of personal assistance to mobility and mobile service robotics, robots and people must share the same physical spaces and follow the same social conventions. Robots must respect proximity constraints but also respect people interacting. For example, they should not break interaction between people talking, unless the robot task is to take part in the conversation. In this case, it must be able to join the group using a socially adapted behavior. The socially-aware navigation system proposed in this thesis integrates both an assessment of a risk of collision using predictive models of moving obstacles, and an assessment of accordance with social conventions. Human management of space (personal space, o-space, activity space...) inspired from sociology and social robotics literature is integrated, but also models of behavior that enable the robot to make medium-term prediction of the human positions. Simulation and experimental results on a robotic wheelchair validate the method by showing that our robot is able to navigate in a dynamic environment avoiding collisions with obstacles and people and, at the same time, minimizing discomfort in people by respecting spaces mentioned above.

The Gulf of St. Lawrence Is closed to commercial navigation for nearly five months each year due to ice conditions. In order to lengthen the shipping season, greater knowledge of the behaviour of the ice is necessary. A step in this direction was the inauguration in 1940 of aerial ice surveys in the gulf during the breakup season. The surveys have continued annually for the past thirteen years. Based primarily on the data provided by these surveys, maps were drawn showing the limits of the main ice areas in each breakup season. Although the maps enabled the isolation of several distinct patterns and rates of breakup, they revealed that the behaviour of the ice was extremely variable. The factors influencing ice conditions, including tides, ocean currents, temperature, and wind, were examined with the aim of discovering the causes of the breakup patterns. A number of factors were found to be important in determining the fundamental behaviour of the ice, bat the meteorological factors of temperature and wind appeared to be the chief agents in causing the variable behaviour from year to year. In spite of these variations, it was possible to trace average conditions throughout the Ice season. The chief characteristics of the ice season may be stated briefly. The Gulf of St. Lawrence is never completely covered with ice, but rather, it is partly covered with fields of shifting pack ice between which lie broad stretches of open water. The southern part of the gulf is an area of accumulation where ice conditions are most serious. The clearing of ice from the gulf begins slowly in January and February and becomes accelerated in March and April. The bulk of the ice moves through Cabot Strait to the open Atlantic rather than remaining inside the gulf until it melts. Generally, the ice either withdraws from west to east, passing through Cabot Strait directly, or it stagnates in the southern part of the gulf toward the end of the season. By the first of May the gulf is usually clear of ice which constitutes a hinderance to navigation. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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An extended Kalman filter is modified to support only magnetometer data as a measurement for spacecraft attitude information. Actual on-orbit data from a student satellite is used in the filter from three different time periods and varying data frequencies. The extended Kalman filter has a thermal model that utilizes external temperature data as a verification tool for filter convergence and for parameter tuning. It can capture the frequency of temperature changes and the correct side panel being lit by the sun as long as the filter converges properly, but not the magnitude of the temperature at a specific time. A solar panel power model is also attempted, which was found to be unusable due to power budget issues and the side panel current sensors railing. Convergence of the three sets of data showed that a 30 second snapshot rate converges to a more accurate attitude information when the satellite has a 0.1 rev/min rotation rate compared to the 1.0 rev/min rotation rate data. A 10 second snapshot rate gives more accurate attitude information for data from a satellite with a 1.0 rev/min rotation rate. By investigating the drastic reduction in the satellite’s rotation rate over 6 months, it was discovered that the satellite’s antenna is most likely magnetized, causing it to try to align itself with the Earth’s magnetic field, slowing down the rotation rate of the satellite from 1 rev/min to 0.1 rev/min.

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Unlike many terrestrial applications, GPS is unavailable to autonomous underwater vehicles (AUVs) while submerged due to the rapid attenuation of radio frequency signals in seawater. Underwater vehicles often use other navigation technologies. This thesis describes a range-based acoustic navigation system that utilizes range measurements from a single moving transponder with a known location to estimate the position of an AUV in geodetic coordinates. Additionally, the navigation system simultaneously estimates the currents acting on the AUV. Thus the navigation system can be used in locations where currents are unknown. The main contribution of this work is the implementation of a range-based navigation system in geodetic coordinates for an AUV. This range-based navigation system is implemented in the World Geodetic System 1984 (WGS 84) coordinate reference system. The navigation system is not restricted to the WGS 84 ellipsoid and can be applied to any reference ellipsoid. This thesis documents the formulation of the navigation system in geodetic coordinates. Experimental data gathered in Claytor Lake, VA, and the Chesapeake Bay is presented. / Master of Science

This thesis describes the development of a new zero-turn-radius (ZTR) differentially driven robotic vehicle hereinafter referred to as NEVEL. The primary objective of this work was to develop a device that could be used as a test-bed for continued autonomous vehicle research at Virginia Tech while meeting the entry requirements of the Annual International Unmanned Ground Robotics Competition. In developing NEVEL, consideration was given to the vehicle's mechanical and electrical design, sensing and computing systems, and navigation strategy. Each of these areas was addressed individually, but always within the context of optimal integration to produce the best overall vehicle system. A constraint that directed much of the design process was the desire to integrate industrially available and proven components rather than creating custom designed systems. This thesis also includes a review of the relevant literature as it pertains to both subsystem and overall vehicle design. NEVEL, the vehicle that was created from this research effort, is novel in several respects. It is one of the few true embodiments of a fully functioning, three-wheel, differential drive autonomous vehicle. Several previous studies have developed this concept for indoor applications, but none has resulted in a working test-bed that can be applied to an unstructured, outdoor environment. NEVEL also appears to be one of the few autonomous vehicle systems to fully incorporate a commercially available laser range finder. These features alone would make NEVEL a useful platform for continued research. In addition, however, by using common, off-the-shelf components and a personal computer platform for all computation and control, NEVEL has been created to facilitate testing of new navigation and control strategies. As testimony to the success of this design, NEVEL was recognized at the Sixth Annual International Unmanned Ground Robotics Competition as the best overall design. / Master of Science