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Full-Text Articles in Engineering
Robust Localization And Landing For Autonomous Unmanned Aerial Vehicles In Maritime Environments, Alexander D. Jordan
Robust Localization And Landing For Autonomous Unmanned Aerial Vehicles In Maritime Environments, Alexander D. Jordan
Theses and Dissertations
This thesis presents methods for robust precision landing of unmanned air vehicles (UAVs) on platforms at sea. Localization methods are proposed for UAV-to-boat state estimation for systems that employ real- time kinematic (RTK) global navigation satellite system (GNSS) and vision sensors. Solutions for GNSS-only are first presented, followed by the fusion of GNSS and vision. The important problem of sensor intrinsic calibration is solved with a novel offline batch estimation approach. Hardware results are presented for all methods. Our calibration of GNSS-to-camera is shown to estimate sensor offsets with millimeter level accuracy. Localization systems are combined with custom state machines …
Enabling Autonomous Operation Of Micro Aerial Vehicles Through Gps To Gps-Denied Transitions, James Scott Jackson
Enabling Autonomous Operation Of Micro Aerial Vehicles Through Gps To Gps-Denied Transitions, James Scott Jackson
Theses and Dissertations
Micro aerial vehicles and other autonomous systems have the potential to truly transform life as we know it, however much of the potential of autonomous systems remains unrealized because reliable navigation is still an unsolved problem with significant challenges. This dissertation presents solutions to many aspects of autonomous navigation. First, it presents ROSflight, a software and hardware architure that allows for rapid prototyping and experimentation of autonomy algorithms on MAVs with lightweight, efficient flight control. Next, this dissertation presents improvments to the state-of-the-art in optimal control of quadrotors by utilizing the error-state formulation frequently utilized in state estimation. It is …
Cooperative Navigation Of Fixed-Wing Micro Air Vehicles In Gps-Denied Environments, Gary James Ellingson
Cooperative Navigation Of Fixed-Wing Micro Air Vehicles In Gps-Denied Environments, Gary James Ellingson
Theses and Dissertations
Micro air vehicles have recently gained popularity due to their potential as autonomous systems. Their future impact, however, will depend in part on how well they can navigate in GPS-denied and GPS-degraded environments. In response to this need, this dissertation investigates a potential solution for GPS-denied operations called relative navigation. The method utilizes keyframe-to-keyframe odometry estimates and their covariances in a global back end that represents the global state as a pose graph. The back end is able to effectively represent nonlinear uncertainties and incorporate opportunistic global constraints. The GPS-denied research community has, for the most part, neglected to consider …
Collaborative Uav Planning, Mapping, And Exploration In Gps-Denied Environments, Jacob Moroni Olson
Collaborative Uav Planning, Mapping, And Exploration In Gps-Denied Environments, Jacob Moroni Olson
Theses and Dissertations
The use of multirotor UAVs to map GPS-degraded environments is useful for many purposes ranging from routine structural inspections to post-disaster exploration to search for survivors and evaluate structural integrity. Multirotor UAVs are able to reach many areas that humans and other robots cannot safely access. Because of their relatively short operational flight time compared to other robotic applications, using multiple UAVs to collaboratively map these environments can streamline the mapping process significantly. This research focuses on four primary areas regarding autonomous mapping and navigation with multiple UAVs in complex unknown or partially unknown GPS-denied environments: The first area is …
Relative Navigation Of Micro Air Vehicles In Gps-Degraded Environments, David Orton Wheeler
Relative Navigation Of Micro Air Vehicles In Gps-Degraded Environments, David Orton Wheeler
Theses and Dissertations
Most micro air vehicles rely heavily on reliable GPS measurements for proper estimation and control, and therefore struggle in GPS-degraded environments. When GPS is not available, the global position and heading of the vehicle is unobservable. This dissertation establishes the theoretical and practical advantages of a relative navigation framework for MAV navigation in GPS-degraded environments. This dissertation explores how the consistency, accuracy, and stability of current navigation approaches degrade during prolonged GPS dropout and in the presence of heading uncertainty. Relative navigation (RN) is presented as an alternative approach that maintains observability by working with respect to a local coordinate …
Relative Navigation Of Autonomous Gps-Degraded Micro Air Vehicles, David O. Wheeler, Daniel P. Koch, James S. Jackson, Gary J. Ellingson, Paul W. Nyholm, Timothy W. Mclain, Randal W. Beard
Relative Navigation Of Autonomous Gps-Degraded Micro Air Vehicles, David O. Wheeler, Daniel P. Koch, James S. Jackson, Gary J. Ellingson, Paul W. Nyholm, Timothy W. Mclain, Randal W. Beard
Faculty Publications
Many current approaches for navigation of micro air vehicles (MAVs) in GPS-degraded environments use a globally-referenced state for estimation and control, even though this state is not observable when GPS is unavailable. By working with respect to a local reference frame, the relative navigation (RN) framework presented in this paper ensures that the state maintains observability and that the uncertainty remains bounded, consistent, and normally-distributed. RN further insulates flight-critical estimation and control processes from the large global updates common in GPS-degraded MAV flight. This paper provides a thorough description of the details needed to successfully implement the RN framework on …
Globally Consistent Map Generation In Gps-Degraded Environments, Paul William Nyholm
Globally Consistent Map Generation In Gps-Degraded Environments, Paul William Nyholm
Theses and Dissertations
Heavy reliance on GPS is preventing unmanned air systems (UAS) from being fully inte- grated for many of their numerous applications. In the absence of GPS, GPS-reliant UAS have difficulty estimating vehicle states resulting in vehicle failures. Additionally, naively using erro- neous measurements when GPS is available can result in significant state inaccuracies. We present a simultaneous localization and mapping (SLAM) solution to GPS-degraded navigation that al- lows vehicle state estimation and control independent of global information. Optionally, a global map can be constructed from odometry measurements and can be updated with GPS measurements while maintaining robustness against outliers.We detail …
Compact Fmcw Radar For Gps-Denied Navigation And Sense And Avoid, James David Mackie
Compact Fmcw Radar For Gps-Denied Navigation And Sense And Avoid, James David Mackie
Theses and Dissertations
Location information is vital for any type of aircraft and even more crucial for Unmanned Aerial Systems (UAS). GPS is a readily available solution but signals can easily be jammed or lost. In this thesis, radar is explored as a backup system for self-localization when GPS signals are not available. The method proposed requires that an area be pre mapped by collecting radar data with known latitude and longitude coordinates. New radar data is then collected and compared to previously stored values. Channel matrices are stored at each point and are used as the basis for location comparisons. Various methods …
Efficient Estimation For Small Multi-Rotor Air Vehicles Operating In Unknown, Indoor Environments, John Charles Macdonald
Efficient Estimation For Small Multi-Rotor Air Vehicles Operating In Unknown, Indoor Environments, John Charles Macdonald
Theses and Dissertations
In this dissertation we present advances in developing an autonomous air vehicle capable of navigating through unknown, indoor environments. The problem imposes stringent limits on the computational power available onboard the vehicle, but the environment necessitates using 3D sensors such as stereo or RGB-D cameras whose data requires significant processing. We address the problem by proposing and developing key elements of a relative navigation scheme that moves as many processing tasks as possible out of the time-critical functions needed to maintain flight. We present in Chapter 2 analysis and results for an improved multirotor helicopter state estimator. The filter generates …
Relative Navigation And Control Of A Hexacopter, Timothy Mclain, Randal W. Beard, Robert C. Leishman, John Macdonald
Relative Navigation And Control Of A Hexacopter, Timothy Mclain, Randal W. Beard, Robert C. Leishman, John Macdonald
Faculty Publications
This paper discusses the progress made on developing a multi-rotor helicopter equipped with a vision-based ability to navigate through an a priori unknown, GPS-denied environment. We highlight the backbone of our system, the relative estimation and control. We depart from the common practice of using a globally referenced map, preferring instead to keep the position and yaw states in the EKF relative to the current map node. This relative navigation approach allows simple application of sensor updates, natural characterization of the transformation between map nodes, and the potential to generate a globally consistent map when desired. The EKF fuses view …
Real-Time Evaluation Of Vision-Based Navigation For Autonomous Landing Of A Rotorcraft Unmanned Aerial Vehicle In A Non-Cooperative Environment, Dale D. Rowley
Real-Time Evaluation Of Vision-Based Navigation For Autonomous Landing Of A Rotorcraft Unmanned Aerial Vehicle In A Non-Cooperative Environment, Dale D. Rowley
Theses and Dissertations
Landing a rotorcraft unmanned aerial vehicle (RUAV) without human supervision is a capability that would significantly broaden the usefulness of UAVs. The benefits are even greater if the functionality is expanded to involve landing sites with unknown terrain and a lack of GPS or other positioning aids. Examples of these types of non-cooperative environments could range from remote mountainous regions to an urban building rooftop or a cluttered parking lot. The research of this thesis builds upon an approach that was initiated at NASA Ames Research Center to advance technology in the landing phase of RUAV operations. The approach consists …