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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

3D rekonstrukce zaniklých plavebních nádrží pomocí UAV fotogrammetrie / 3D reconstruction of abandonned ponds using UAV photogrammetry

Stanovský, Tomáš January 2019 (has links)
The main focus of the thesis is the reconstruction of 3D models and digital elevation models of five abandoned splash dams in Roklanský brook catchment using UAV photogrammetry methods. The aim of this work is to compare accuracy of the models with available conventional data sources and historical sources. Parallel topic is the research of accuracy of the models created through UAV methods and application of retention potential of small water reservoirs, in headwater areas. The images were taken with a drone-mounted camera. Modelling was done by processing images in software Agisoft PhotoScan through a workflow process, dense point cloud classification and subsequent DEM interpolation. Subsequent delineation of reservoirs retention space, altimetry correction and bathymetric analysis was performed in ArcMap over the interpolated DEM. The results and discussion point to the benefits and limitations of UAV methods, especially to altimetric accuracy of the resulting models relative to conventional DMR5G data and bathymetric characteristics derived from the models. Keywords: UAV; DEM; retention; GIS; model; pond
132

Fotogrammetrisk 3D-modellering av en kraftledningsstolpe med UAV : Undersökning av modellernas geometriska kvalitet / Photogrammetric 3D-modeling of a power line pole with UAV : Examination of the models geometric quality

Grimstad, Benjamin January 2019 (has links)
The overall objective of the study was to investigate how much a photogrammetrically modelled power line pole differs from reality and test what flight height gives the best result. In the study, two 3D models were created using UAV images supported by RTK-measured ground points. In both models, vertical images from a height of 40 meters were used. The first model was supplemented with oblique images taken from a height of 40 meters and the second model with oblique images taken from a height of 30 meters. In order to compare both models with the actual power line pole, a total of 25 details on the pole were measured with a total station and used as control points. The control points were then compared to the same points in the 3D models and the deviations between the real pole and models were calculated. The result shows a radial mean deviation in plane of 0,04 meters for model 1 and 0,03 meters for model 2. The average error in height is 0,03 meters for model 1 and 0,02 meters for model 2. It was also found that oblique images taken at a lower altitude results in a larger camera angle and smaller pixel size. This fact turns out to be of great importance when the Pix4Dmapper program is to recreate a correct scaled and detailed 3D model. The conclusion is that images taken from the flight height of 30 meters results in a better quality of the 3D model. / Det övergripande syftet med studien är att undersöka hur mycket en fotogrammetriskt modellerad kraftledningsstolpe skiljer sig från verkligheten och undersöka vilken flyghöjd som ger bäst resultat. I studien har två 3D-modeller skapats med hjälp av UAV-bilder tillsammans med RTK-inmätta markstöd. I båda modellerna har lodbilder tagna från 40 meters höjd använts. Den första modellen kompletterades med snedbilder tagna från 40 meters höjd och den andra modellen med snedbilder tagna från 30 meters höjd. För att jämföra modellerna med den verkliga kraftledningsstolpen mättes totalt 25 detaljer på stolpen in med en totalstation och användes som kontrollpunkter. Dessa jämfördes med motsvarande punkter i 3D-modellerna och avvikelser räknades fram. Resultatet visar en radiell medelavvikelse i plan på 0,04 meter för modell 1 och 0,03 meter för modell 2. Medelfelet i höjd är 0,03 meter för modell 1 och 0,02 meter för modell 2. Resultatet visar också att snedbilder tagna på en lägre höjd, vilket innebär större kameravinkel och mindre pixelstorlek, har stor betydelse när programmet Pix4Dmapper ska återskapa en skalriktig och detaljrik 3D-modell. Slutsatsen är att bilder tagna från flyghöjden 30 meter ger en högre kvalitet på modellen.
133

An Intelligent Portable Aerial Surveillance System: Modeling and Image Stitching

Du, Ruixiang 29 May 2013 (has links)
"Unmanned Aerial Vehicles (UAVs) have been widely used in modern warfare for surveillance, reconnaissance and even attack missions. They can provide valuable battlefield information and accomplish dangerous tasks with minimal risk of loss of lives and personal injuries. However, existing UAV systems are far from perfect to meet all possible situations. One of the most notable situations is the support for individual troops. Besides the incapability to always provide images in desired resolution, currently available systems are either too expensive for large-scale deployment or too heavy and complex for a single solder. Intelligent Portable Aerial Surveillance System (IPASS), sponsored by the Air Force Research Laboratory (AFRL), is aimed at developing a low-cost, light-weight unmanned aerial vehicle that can provide sufficient battlefield intelligence for individual troops. The main contributions of this thesis are two-fold (1) the development and verification of a model-based flight simulation for the aircraft, (2) comparison of image stitching techniques to provide a comprehensive aerial surveillance information from multiple vision. To assist with the design and control of the aircraft, dynamical models are established at different complexity levels. Simulations with these models are implemented in Matlab to study the dynamical characteristics of the aircraft. Aerial images acquired from the three onboard cameras are processed after getting the flying platform built. How a particular image is formed from a camera and the general pipeline of the feature-based image stitching method are first introduced in the thesis. To better satisfy the needs of this application, a homography-based stitching method is studied. This method can greatly reduce computation time with very little compromise in the quality of the panorama, which makes real-time video display of the surroundings on the ground station possible. By implementing both of the methods for image stitching using OpenCV, a quantitative comparison in the performance is accomplished."
134

A Collaborative Conceptual Aircraft Design Environment for the Design of Small-Scale UAVs in a Multi-University Setting

Becar, Joseph Samuel 01 May 2015 (has links)
In today's competitive global market, there is an ever-increasing demand for highly skilled engineers equipped to perform in teams dispersed over several time-zones by geography. Aerospace Partners for the Advancement of Collaborative Engineering (AerosPACE) is a senior design capstone program co-developed by academia and industry to help students develop the necessary skills to excel in the aerospace industry by challenging them to design, build, and fly an unique unmanned aerial vehicle (UAV). Students with little to no experience designing UAVs are put together in teams with their peers from geographically dispersed universities. This presents a significant challenge for the students in assimilating and applying aircraft design principles, using and interpreting output from analysis tools in multiple disciplines, and communicating their findings with their team members in an effective way. This thesis documents the development of a collaborative design tool for the generation and evaluation of small-scale electric-powered UAV concepts in AerosPACE. The integrated design and optimization software CCADE (Collaborative Conceptual Aircraft Design Environment) enables the immersion of team members from different universities in a software environment which shares design information and analysis results in a central database. Input files for use by open-source analysis tools are automatically generated, and output files read in and displayed in a user-friendly graphical interface. Analysis codes for initial sizing, geometry, airfoil selection, aerodynamics, propulsion, stability and control, and structures are included in the software. Optimization methods are proposed for implementation in future versions of CCADE to explore the breadth of the design space and help students understand the sensitivity of their design to certain key parameters. Testing of CCADE by students during the 2014-2015 AerosPACE course showed an increased volume of explored concepts and prompted questions from students to fill gaps in understanding of fundamental principles. Suggestions for increased student acceptance and use of the software are given. Through its unique architecture and application, CCADE aims to increase productivity and teamwork among AerosPACE participants by increasing the number of concepts which can be fully analyzed, enabling broader exploration of the feasible design space to produce unique and innovative aircraft configurations, and allowing teammates to share thoughts and learning via a shared design and analysis work-space.
135

Diseño, Construcción e Integración de un Módulo de Interfaz Digital Análogo para Sistemas Repetidores de Globo Sonda Usados en Situaciones de Emergencia

Abarca Mesa, Ignacio Andrés January 2011 (has links)
Memoria para optar al título de Ingeniero Civil Electricista / En esta memoria se propone un diseño para un módulo de interfaz digital-análogo, usado como modem, codificador y decodificador. Su función es enviar y recibir información digital a través de un canal de audio en radiofrecuencia. Se presenta además el estudio y análisis de la factibilidad técnica de este diseño. En periodos de catástrofe o en lugares aislados los servicios de emergencia y seguridad requieren plataformas de comunicación exclusivas, portables y de bajo costo (en lo posible desechables). Como eventual solución se plantean globos aerostáticos y/o vehículos aéreos autónomos (UAVs) de bajo costo que puedan actuar como repetidor de comunicación de audio. Sin embargo la posición GPS de estos objetos es necesaria para el monitoreo y toma de decisiones de la comunicación haciendo necesario un módulo interfaz que permita transmitir los datos digitales de la posición a través de este canal de audio. En particular el objetivo de este trabajo es el desarrollo de un prototipo del módulo interfaz que incluye tanto hardware como software. El hardware del módulo está compuesto principalmente por un microcontrolador y un modem de audio, mientras que el software de comunicación se basa en el protocolo APRS. En este documento se especifica el diseño del software y de los algoritmos que manejan el protocolo y las funcionalidades del sistema. El hardware de bajo costo, el cual es requisito para esta solución, dificulta el uso de protocolos de comunicación estándares dado el ruido y distorsiones de las señales que este producen. Debido a esto el software de comunicación debe ser más robusto que los protocolos usuales. El nuevo protocolo presentado en este trabajo cambia la estrategia de muestreo y decodificación de los datos. Finalmente se realiza un análisis funcional del software que controla el hardware del módulo. Los resultados de desempeño del módulo son presentados junto con estrategias de mejoras futuras.
136

Topics in navigation and guidance of wheeled robots

Teimoori Sangani, Hamid, Electrical Engineering & Telecommunications, Faculty of Engineering, UNSW January 2009 (has links)
Navigation and guidance of mobile robots towards steady or maneuvering objects (targets) is one of the most important areas of robotics that has attracted a lot of attention in recent decades. However, in most of the existing methods, both the line-of-sight angle (bearing) and the relative distance (range) are assumed to be available for navigation and guidance algorithms. There is also a relatively large body of research on navigation and guidance with bearings-only measurements. In contrast, only a few results on navigation and guidance towards an unknown target using range-only measurements have been published. Various problems of navigation, guidance, location estimation and target tracking based on range-only measurements often arise in new wireless networks related applications. Recent advances in these applications allow us to use inexpensive transponders and receivers for range-only measurements which provide information in dynamic and noisy environments without the necessity of line-of-sight. To take advantage of these sensors, algorithms must be developed for range-only navigation. The main part of this thesis is concerned with the problem of real-time navigation and guidance of Wheeled Mobile Robots (WMRs) towards an unknown stationary or moving target using range-only measurements. The range can be estimated using the signal strength and the robust extended Kalman filtering. Several similar algorithms for navigation and guidance termed Equiangular Navigation and Guidance (ENG) laws are proposed and mathematically rigorous proofs of convergence and stability of the proposed guidance laws are given. The experimental investigation into the use of range data for a WMR navigation is documented and the results and discussions on the performance of the proposed guidance strategies are presented, where a wheeled robot successfully approach a stationary or follow a maneuvering target. In order to safely navigate and reliably operate in populated environments, ENG is then modified into Augmented-ENG (AENG), which enables the robot to approach a stationary target or follow an unpredictable maneuvering object in an unknown environment, while keeping a safe distance from the target, and simultaneously preserving a safety margin from the obstacles. Furthermore, we propose and experimentally investigate a new biologically inspired method for local obstacle avoidance and give the mathematically rigorous proof of the idea. In order for the robot to avoid collision and bypass the enroute obstacles in this method, the angle between the instantaneous moving direction of the robot and a reference point on the surface of the obstacle is kept constant. The proposed idea is combined with the ENG law, which leads to a reliable and fast long-range navigation. The performance of both navigation strategy and local obstacle avoidance techniques are confirmed with computer simulations and several experiments with ActivMedia Pioneer 3-DX wheeled robots. The second part of the thesis investigates some challenging problems in the area of wheeled robot navigation. We first address the problem of bearing-only guidance of an autonomous vehicle following a moving target with smaller minimum turning radius compared to that of the follower and propose a simple and constructive navigation law. In compliance with the increasing research on decentralized control laws for groups of mobile autonomous robots, we consider the problems of decentralized navigation of network of WMRs with limited communication and decentralized stabilization of formation of WMRs. New control laws are presented and simulation results are provided to illustrate the control laws and their applications.
137

A systems approach to model the conceptual design process of vertical take-off unmanned aerial vehicle.

Rathore, Ankush, ankushrathore@yahoo.com January 2006 (has links)
The development and induction in-service of Unmanned Air Vehicles (UAV) systems in a variety of civil, paramilitary and military roles have proven valuable on high-risk missions. These UAVs based on fixed wing configuration concept have demonstrated their operational effectiveness in recent operations. New UAVs based on rotary wing configuration concept have received major attention worldwide, with major resources committed for its research and development. In this thesis, the design process of a rotary-wing aircraft was re-visualised from an unmanned perspective to address the requirements of rotary-wing UAVs - Vertical Take-off UAVs (VTUAV). It investigates the conventional helicopter design methodology for application in UAV design. It further develops a modified design process for VTUAV addressing the requirements of unmanned missions by providing remote command-and-control capabilities. The modified design methodology is automated to address the complex design evaluations and optimisation process. An illustration of the automated design process developed for VTUAVs is provided through a series of inputs of the requirements and specifications, resulting in an output of a proposed VTUAV design configuration for
138

Multi-Objective and Multidisciplinary Design Optimisation of Unmanned Aerial Vehicle Systems using Hierarchical Asynchronous Parallel Multi-Objective Evolutionary Algorithms

Damp, Lloyd Hollis January 2007 (has links)
Master of Engineering (Research) / The overall objective of this research was to realise the practical application of Hierarchical Asynchronous Parallel Evolutionary Algorithms for Multi-objective and Multidisciplinary Design Optimisation (MDO) of UAV Systems using high fidelity analysis tools. The research looked at the assumed aerodynamics and structures of two production UAV wings and attempted to optimise these wings in isolation to the rest of the vehicle. The project was sponsored by the Asian Office of the Air Force Office of Scientific Research under contract number AOARD-044078. The two vehicles wings which were optimised were based upon assumptions made on the Northrop Grumman Global Hawk (GH), a High Altitude Long Endurance (HALE) vehicle, and the General Atomics Altair (Altair), Medium Altitude Long Endurance (MALE) vehicle. The optimisations for both vehicles were performed at cruise altitude with MTOW minus 5% fuel and a 2.5g load case. The GH was assumed to use NASA LRN 1015 aerofoil at the root, crank and tip locations with five spars and ten ribs. The Altair was assumed to use the NACA4415 aerofoil at all three locations with two internal spars and ten ribs. Both models used a parabolic variation of spar, rib and wing skin thickness as a function of span, and in the case of the wing skin thickness, also chord. The work was carried out by integrating the current University of Sydney designed Evolutionary Optimiser (HAPMOEA) with Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) tools. The variable values computed by HAPMOEA were subjected to structural and aerodynamic analysis. The aerodynamic analysis computed the pressure loads using a Boeing developed Morino class panel method code named PANAIR. These aerodynamic results were coupled to a FEA code, MSC.Nastran® and the strain and displacement of the wings computed. The fitness of each wing was computed from the outputs of each program. In total, 48 design variables were defined to describe both the structural and aerodynamic properties of the wings subject to several constraints. These variables allowed for the alteration of the three aerofoil sections describing the root, crank and tip sections. They also described the internal structure of the wings allowing for variable flexibility within the wing box structure. These design variables were manipulated by the optimiser such that two fitness functions were minimised. The fitness functions were the overall mass of the simulated wing box structure and the inverse of the lift to drag ratio. Furthermore, six penalty functions were added to further penalise genetically inferior wings and force the optimiser to not pass on their genetic material. The results indicate that given the initial assumptions made on all the aerodynamic and structural properties of the HALE and MALE wings, a reduction in mass and drag is possible through the use of the HAPMOEA code. The code was terminated after 300 evaluations of each hierarchical level due to plateau effects. These evolutionary optimisation results could be further refined through a gradient based optimiser if required. Even though a reduced number of evaluations were performed, weight and drag reductions of between 10 and 20 percent were easy to achieve and indicate that the wings of both vehicles can be optimised.
139

Support System for Landing with an Autonomous Unmanned Aerial Vehicle

Östman, Christian, Forsberg, Anna January 2009 (has links)
<p>There are a number of ongoing projects developing autonomous vehicles, both helicopters and airplanes. The purpose of this thesis is to study a concept for calculating the height and attitude of a helicopter. The system will be active during landing. This thesis includes building an experimental setup and to develop algorithms and software.</p><p>The basic idea is to illuminate the ground with a certain pattern and in our case we used laser pointers to create this pattern. The ground is then filmed and the images are processed to extract the pattern. This provides us with information about the height and attitude of the helicopter. Furthermore, the concept implies that no equipment on the ground is needed. With further development the sensor should be able to calculate the movement of the underlying surface relative to the helicopter. This is very important when landing on a moving surface, e.g. a ship at sea.</p><p>To study the concept empirically an experimental setup was constructed. The setup provides us with the necessary information to evaluate how well the system could perform in reality. The setup is built with simple and cheap materials. In the setup an ordinary web camera and laser pointers that are avaliable for everyone have been used.</p> / <p>Det finns flera pågående projekt inom autonomflygande farkoster, både för helikoptrar och flygplan. Syftet med vårt examensarbetet är att undersöka ett koncept för en landningssensor för autonom landning med helikopter. Examensarbetet innebär att bygga en fysisk modell för test av konceptet samt att utveckla mjukvara.</p><p>Konceptet för sensorn består av att belysa marken med ett speciellt mönster, i vårt fall skapas mönstret av laserpekare, som därefter fotograferas och bildbehandlas. Detta mönster ger sedan information om helikopterns höjd och attityd i luften. Vidare innebär konceptet också att ingen markutrustning krävs för att sensorn ska fungera. I förlängningen ska man med detta koncept kunna beräkna hur underlaget rör sig relativt helikoptern, vilket är väldigt viktigt vid landning på objekt som rör sig, till exempel ett fartyg.</p><p>För att undersöka hur bra sensorn presterar i verkligheten så har en rigg byggts. Riggen är byggd med enkla och billiga material. I det här fallet används en webbkamera och laserpekare som går att köpa i vanliga elektronikaffärer.</p>
140

Positionsindikering i bilder och video för WITAS dialogsystem / Position specification in images and video for the WITAS dialog system

Lindblom, Hannes January 2004 (has links)
<p>Denna rapport beskriver arbetet med en utökning av ett dialogsystem till en UAV (Unmanned Aerial Vehicle, obemannad flygande farkost). Arbetet är utfört i WITAS-projektet (Wallenberg laboratory for research on Information Technology and Autonomous Systems), ett projekt som har som mål att utveckla en helikopter som ska kunna verka autonomt i t.ex. en trafikmiljö. Syftet med dialogsystemet är att en operatör med talspråk ska kunna ge kommandon till och få information från helikoptern. Detta examensarbete har som mål att utöka dialogen till att bli multimodal, dvs. att även innefatta pekningar och rörelser med musen. Operatören ska alltså kunna peka ut platser och objekt i en karta för att komplettera ett talat kommando eller få data utritat i kartan som svar på en förfrågan.</p>

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