Global ETD Search

81	Cooperative Navigation of Fixed-Wing Micro Air Vehicles in GPS-Denied Environments Ellingson, Gary James 05 November 2019 (has links) 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 fixed-wing aircraft. This dissertation enables fixed-wing aircraft to utilize relative navigation by accounting for their sensing requirements. The development of an odometry-like, front-end, EKF-based estimator that utilizes only a monocular camera and an inertial measurement unit is presented. The filter uses the measurement model of the multi-state-constraint Kalman filter and regularly performs relative resets in coordination with keyframe declarations. In addition to the front-end development, a method is provided to account for front-end velocity bias in the back-end optimization. Finally a method is presented for enabling multiple vehicles to improve navigational accuracy by cooperatively sharing information. Modifications to the relative navigation architecture are presented that enable decentralized, cooperative operations amidst temporary communication dropouts. The proposed framework also includes the ability to incorporate inter-vehicle measurements and utilizes a new concept called the coordinated reset, which is necessary for optimizing the cooperative odometry and improving localization. Each contribution is demonstrated through simulation and/or hardware flight testing. Simulation and Monte-Carlo testing is used to show the expected quality of the results. Hardware flight-test results show the front-end estimator performance, several back-end optimization examples, and cooperative GPS-denied operations. GPS degradation GPS denied navigation state estimation observability extended Kalman filter sensor fusion vision-aided INS consistency multirotor fixed wing micro air vehicle indoor flight outdoor flight simultaneous localization and mapping place recognition loop closure pose graph optimization visual odometry cooperative estimation Engineering
82	Enabling Autonomous Operation of Micro Aerial Vehicles Through GPS to GPS-Denied Transitions Jackson, James Scott 11 November 2019 (has links) 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 shown that performing optimal control directly over the error-state results in a vastly more computationally efficient system than competing methods while also dealing with the non-vector rotation components of the state in a principled way. In addition, real-time robust flight planning is considered with a method to navigate cluttered, potentially unknown scenarios with real-time obstacle avoidance. Robust state estimation is a critical component to reliable operation, and this dissertation focuses on improving the robustness of visual-inertial state estimation in a filtering framework by extending the state-of-the-art to include better modeling and sensor fusion. Further, this dissertation takes concepts from the visual-inertial estimation community and applies it to tightly-coupled GNSS, visual-inertial state estimation. This method is shown to demonstrate significantly more reliable state estimation than visual-inertial or GNSS-inertial state estimation alone in a hardware experiment through a GNSS-GNSS denied transition flying under a building and back out into open sky. Finally, this dissertation explores a novel method to combine measurements from multiple agents into a coherent map. Traditional approaches to this problem attempt to solve for the position of multiple agents at specific times in their trajectories. This dissertation instead attempts to solve this problem in a relative context, resulting in a much more robust approach that is able to handle much greater intial error than traditional approaches. GPS degradation GPS denied navigation state estimation observability error state sensor fusion vision-aided INS consistency multirotor micro air vehicle indoor flight outdoor flight pose graph optimization obstacle avoidance visual odometry Moving Horizon Estimation Pseudorange Linear Quadratic Regulator LQR Moving Horizon Estimation MHE Sliding Window Optimization Engineering
83	Through the Blur with Deep Learning : A Comparative Study Assessing Robustness in Visual Odometry Techniques Berglund, Alexander January 2023 (has links) In this thesis, the robustness of deep learning techniques in the field of visual odometry is investigated, with a specific focus on the impact of motion blur. A comparative study is conducted, evaluating the performance of state-of-the-art deep convolutional neural network methods, namely DF-VO and DytanVO, against ORB-SLAM3, a well-established non-deep-learning technique for visual simultaneous localization and mapping. The objective is to quantitatively assess the performance of these models as a function of motion blur. The evaluation is carried out on a custom synthetic dataset, which simulates a camera navigating through a forest environment. The dataset includes trajectories with varying degrees of motion blur, caused by camera translation, and optionally, pitch and yaw rotational noise. The results demonstrate that deep learning-based methods maintained robust performance despite the challenging conditions presented in the test data, while excessive blur lead to tracking failures in the geometric model. This suggests that the ability of deep neural network architectures to automatically learn hierarchical feature representations and capture complex, abstract features may enhance the robustness of deep learning-based visual odometry techniques in challenging conditions, compared to their geometric counterparts. artificial intelligence AI machine learning ML deep learning DL computer vision neural networks NN convolutional neural networks CNN visual odometry VO robustness motion blur AirForestry localization navigation ego-motion pose estimation SLAM DF-VO DytanVO ORB-SLAM3 artificiell intelligens maskininlärning datorseende Computer Sciences Datavetenskap (datalogi)
84	Creating Good User Experience in a Hand-Gesture-Based Augmented Reality Game / Användbarhet i ett handgestbaserat AR-spel Lam, Benny, Nilsson, Jakob January 2019 (has links) The dissemination of new innovative technology requires feasibility and simplicity. The problem with marker-based augmented reality is similar to glove-based hand gesture recognition: they both require an additional component to function. This thesis investigates the possibility of combining markerless augmented reality together with appearance-based hand gesture recognition by implementing a game with good user experience. The methods employed in this research consist of a game implementation and a pre-study meant for measuring interactive accuracy and precision, and for deciding upon which gestures should be utilized in the game. A test environment was realized in Unity using ARKit and Manomotion SDK. Similarly, the implementation of the game used the same development tools. However, Blender was used for creating the 3D models. The results from 15 testers showed that the pinching gesture was the most favorable one. The game was evaluated with a System Usability Scale (SUS) and received a score of 70.77 among 12 game testers, which indicates that the augmented reality game, which interaction method is solely based on bare-hands, can be quite enjoyable. AR Hand gestures Bare-hand interaction HGR Augmented reality usability user experience Manomotion ARKit Visual Odometry SLAM VO VIO 3D gestural interaction gesture recognition gesture tracking augmented environments Förstärkt verklighet 3D gestinteraktion gestigenkänning visuell odometri Manomotion ARKit Engineering and Technology Teknik och teknologier Interaction Technologies Interaktionsteknik Design Design Human Computer Interaction Probability Theory and Statistics Sannolikhetsteori och statistik Computer Systems Datorsystem Software Engineering Programvaruteknik

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