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Dellaert, Frank

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Author: Beall, Chris × End date: 2020 × Start date: 2010 × search.filters.applied.f.isOrgUnitOfPublicationTitle: College of Computing ×

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    Eliminating Conditionally Independent Sets in Factor Graphs: A Unifying Perspective based on Smart Factors
    (Georgia Institute of Technology, 2014) Carlone, Luca ; Kira, Zsolt ; Beall, Chris ; Indelman, Vadim ; Dellaert, Frank
    Factor graphs are a general estimation framework that has been widely used in computer vision and robotics. In several classes of problems a natural partition arises among variables involved in the estimation. A subset of the variables are actually of interest for the user: we call those target variables. The remaining variables are essential for the formulation of the optimization problem underlying maximum a posteriori (MAP) estimation; however these variables, that we call support variables, are not strictly required as output of the estimation problem. In this paper, we propose a systematic way to abstract support variables, defining optimization problems that are only defined over the set of target variables. This abstraction naturally leads to the definition of smart factors, which correspond to constraints among target variables. We show that this perspective unifies the treatment of heterogeneous problems, ranging from structureless bundle adjustment to robust estimation in SLAM. Moreover, it enables to exploit the underlying structure of the optimization problem and the treatment of degenerate instances, enhancing both computational efficiency and robustness.
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    Attitude Heading Reference System with Rotation-Aiding Visual Landmarks
    (Georgia Institute of Technology, 2012-07) Beall, Chris ; Ta, Duy-Nguyen ; Ok, Kyel ; Dellaert, Frank
    In this paper we present a novel vision-aided attitude heading reference system for micro aerial vehicles (MAVs) and other mobile platforms, which does not rely on known landmark locations or full 3D map estimation as is common in the literature. Inertial sensors which are commonly found on MAVs suffer from additive biases and noise, and yaw error will grow without bounds. The bearing-only measurements, which we call vistas, aid the vehicle’s heading estimate and allow for long-term operation while correcting for sensor drift. Our method is experimentally validated on a commercially available low-cost quadrotor MAV.
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    Bundle Adjustment in Large-Scale 3D Reconstructions based on Underwater Robotic Surveys
    (Georgia Institute of Technology, 2011-06) Beall, Chris ; Dellaert, Frank ; Mahon, Ian ; Williams, Stefan B.
    In this paper we present a technique to generate highly accurate reconstructions of underwater structures by employing bundle adjustment on visual features, rather than relying on a filtering approach using navigational sensor data alone. This system improves upon previous work where an extended information filter was used to estimate the vehicle trajectory. This filtering technique, while very efficient, suffers from the shortcoming that linearization errors are irreversibly incorporated into the vehicle trajectory estimate. This drawback is overcome by applying smoothing and mapping to the full problem. In contrast to the filtering approach, smoothing and mapping techniques solve for the entire vehicle trajectory and landmark positions at once by performing bundle adjustment on all the visual measurements taken at each frame. We formulate a large nonlinear least-squares problem where we minimize the pixel projection error of each of the landmark measurements. The technique is demonstrated on a large-scale underwater dataset, and it is also shown that superior results are achieved with smoothing and mapping as compared to the filtering approach.