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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.
41

Unmanned aerial vehicle-based non-destructive testing methods for concrete structures

Blaney, Sean 09 1900 (has links)
In this work, unmanned aerial vehicle-based non-destructive testing methods for concrete structures are evaluated and developed. There exists a need for improved infrastructure inspection techniques with increased expediency. Unmanned aerial vehicles (UAVs) are highly mobile and have shown promise towards achieving this directive, but more work is required to adapt traditional NDT methods to be UAV-compatible. To this end, concrete sounding techniques were evaluated with a quantitative acoustic frequency analysis procedure on a series of concrete slabs. One such method was adapted for use with a UAV and was used to detect subsurface voids in one of the concrete samples and offer a means of depth estimation. This work was complemented with experiments concerning UAV-based visual and infrared imaging techniques already in practice for UAV-based concrete inspection. Together, findings indicate the strengths and weaknesses of the NDTs tested and suggest further improvements for UAV-based NDTs and inspection strategies moving forward. Development of a novel sensor platform for UAV-based measurement, as well as results of an actual bridge inspection using infrared and optical methods demonstrate the present capabilities of the UAV-based instrumentation. / Graduate / 2019-07-03
42

Moving Obstacle Avoidance for Unmanned Aerial Vehicles

January 2015 (has links)
abstract: There has been a vast increase in applications of Unmanned Aerial Vehicles (UAVs) in civilian domains. To operate in the civilian airspace, a UAV must be able to sense and avoid both static and moving obstacles for flight safety. While indoor and low-altitude environments are mainly occupied by static obstacles, risks in space of higher altitude primarily come from moving obstacles such as other aircraft or flying vehicles in the airspace. Therefore, the ability to avoid moving obstacles becomes a necessity for Unmanned Aerial Vehicles. Towards enabling a UAV to autonomously sense and avoid moving obstacles, this thesis makes the following contributions. Initially, an image-based reactive motion planner is developed for a quadrotor to avoid a fast approaching obstacle. Furthermore, A Dubin’s curve based geometry method is developed as a global path planner for a fixed-wing UAV to avoid collisions with aircraft. The image-based method is unable to produce an optimal path and the geometry method uses a simplified UAV model. To compensate these two disadvantages, a series of algorithms built upon the Closed-Loop Rapid Exploratory Random Tree are developed as global path planners to generate collision avoidance paths in real time. The algorithms are validated in Software-In-the-Loop (SITL) and Hardware-In-the-Loop (HIL) simulations using a fixed-wing UAV model and in real flight experiments using quadrotors. It is observed that the algorithm enables a UAV to avoid moving obstacles approaching to it with different directions and speeds. / Dissertation/Thesis / Doctoral Dissertation Computer Science 2015
43

Uma plataforma orientada a agentes para o desenvolvimento de software em veículos aéreos não-tripulados / An agent-oriented platform for development and programming unmanned aerial vehicles

Hama, Marcelo Tomio January 2012 (has links)
Veículos aéreos não-tripulados (VANTs) são relativamente recentes no meio acadêmico, onde muitas tecnologias e algoritmos vêm sendo pesquisados e desenvolvidos. A engenharia de software apliacada a este âmbito possui poucas abordagens em relação a sistemas autônomos e inteligentes, enquanto que sistemas multi-agentes e a programação orientada a agentes vêm sendo cada vez mais utilizadas. Este trabalho foca na aplicação do paradigma da programação orientada a agentes para o controle de VANTs, de modo a conceber um framework e utilizar arquitetura, teoria e ferramentas orientados a agentes como forma de prover uma abstração mais sofisticada para a programação de comportamentos inteligentes em VANTs. Na pesquisa, propõem-se o modelo UAVAS – Unmanned Aerial Vehicles AgentSpeak que é um framework de programação de comportamentos para VANTs que possui um modelo de abstração de veículos aéreos tripulados para veículos aéreos não-tripulados. Ao final, a pesquisa foi avaliada e validada por meio de resultados obtidos em simulações com a infraestrutura implementada. Dois estudos de caso foram realizados, um com ênfase nas comunicações inter-VANTs e cooperação de time, e outro com ênfase nas verificações dos mapeamentos de sinais com o envio de dados da infraestrutura. Para cada um dos casos, simuladores específicos foram criados no intuito de observar as características pertinentes de cada estudo de caso. / Unmanned aerial vehicles (UAVs) are relatively new in civilian context, where many technologies and algorithms have been the focus at much research and development. Software engineering applied to this field has few approaches in relation to autonomous systems and intelligent behavior development, while multi-agent system and agent-oriented programming are being increasingly used. This work focuses on applying the paradigm of agent-oriented programming for the control of UAVs, in order to design a framework and use architecture, theory and agent oriented tools as a way to provide a more sophisticated abstraction for programming intelligent behaviors in UAVs . The main contribution of this work is an architecture that allows the use of the Jason platform to program multiagent system which can control teams of autonomous unmanned aerial vehicles. In this research, we propose the UAVAS - Unmanned Aerial Vehicles AgentSpeak model, which is a framework to program intelligent behaviors to UAVs and owns an abstraction model of manned aircraft to unmanned aerial vehicles. At the end, the survey was evaluated and validated by means of results from simulations in the implemented infrastructure. Two case studies were performed, with emphasis on inter-UAV communication and cooperation of team, and the another one focusing on mapping verifications of data signals sent to the infrastructure. For each case, specific simulators have been created in order to observe the relevant characteristics of each case study.
44

Uma plataforma orientada a agentes para o desenvolvimento de software em veículos aéreos não-tripulados / An agent-oriented platform for development and programming unmanned aerial vehicles

Hama, Marcelo Tomio January 2012 (has links)
Veículos aéreos não-tripulados (VANTs) são relativamente recentes no meio acadêmico, onde muitas tecnologias e algoritmos vêm sendo pesquisados e desenvolvidos. A engenharia de software apliacada a este âmbito possui poucas abordagens em relação a sistemas autônomos e inteligentes, enquanto que sistemas multi-agentes e a programação orientada a agentes vêm sendo cada vez mais utilizadas. Este trabalho foca na aplicação do paradigma da programação orientada a agentes para o controle de VANTs, de modo a conceber um framework e utilizar arquitetura, teoria e ferramentas orientados a agentes como forma de prover uma abstração mais sofisticada para a programação de comportamentos inteligentes em VANTs. Na pesquisa, propõem-se o modelo UAVAS – Unmanned Aerial Vehicles AgentSpeak que é um framework de programação de comportamentos para VANTs que possui um modelo de abstração de veículos aéreos tripulados para veículos aéreos não-tripulados. Ao final, a pesquisa foi avaliada e validada por meio de resultados obtidos em simulações com a infraestrutura implementada. Dois estudos de caso foram realizados, um com ênfase nas comunicações inter-VANTs e cooperação de time, e outro com ênfase nas verificações dos mapeamentos de sinais com o envio de dados da infraestrutura. Para cada um dos casos, simuladores específicos foram criados no intuito de observar as características pertinentes de cada estudo de caso. / Unmanned aerial vehicles (UAVs) are relatively new in civilian context, where many technologies and algorithms have been the focus at much research and development. Software engineering applied to this field has few approaches in relation to autonomous systems and intelligent behavior development, while multi-agent system and agent-oriented programming are being increasingly used. This work focuses on applying the paradigm of agent-oriented programming for the control of UAVs, in order to design a framework and use architecture, theory and agent oriented tools as a way to provide a more sophisticated abstraction for programming intelligent behaviors in UAVs . The main contribution of this work is an architecture that allows the use of the Jason platform to program multiagent system which can control teams of autonomous unmanned aerial vehicles. In this research, we propose the UAVAS - Unmanned Aerial Vehicles AgentSpeak model, which is a framework to program intelligent behaviors to UAVs and owns an abstraction model of manned aircraft to unmanned aerial vehicles. At the end, the survey was evaluated and validated by means of results from simulations in the implemented infrastructure. Two case studies were performed, with emphasis on inter-UAV communication and cooperation of team, and the another one focusing on mapping verifications of data signals sent to the infrastructure. For each case, specific simulators have been created in order to observe the relevant characteristics of each case study.
45

Sécurité et fiabilité des communications dans les réseaux d’essaims / Secure and reliable communications in swarm networks

Zaouche, Lotfi 08 February 2017 (has links)
L’émergence de véhicules aériens sans pilote, généralement appelés drones, petits et bon marché favorise leur utilisation dans le domaine des applications civiles. Ces drones sont équipés de différents capteurs et ont la capacité de communiquer via des liaisons sans fil et ont la particularité de se déplacer librement dans l’espace, révolutionnant la gestion des applications de surveillance. Un réseau ad hoc de drones, Flying Ad hoc Networks (FANET) en anglais, est composé d’une flotte de drones autonomes et est utilisé lors de missions dans des environnements hostiles pour la surveillance ou l’inspection de sites dangereux ou inconnus. Les FANETs peuvent être également utilisés pour suivre et filmer des événements spéciaux comme une course de vélos ou un match de football, dans ce cas les liaisons doivent garantir un minimum de qualité. Les FANETs nécessitent une attention particulière en ce qui concerne l’économie d’énergie des UAV dont les ressources en énergie sont limitées, mais aussi d’être immunisés contre des attaques malveillantes. Au cours de cette thèse, nous nous sommes concentrés sur le problème de suivi d’une cible mobile utilisant une flotte de drones pour la filmer. Étant donné que la cible se déplace, les drones doivent la suivre en continu, et une liaison vers la station terrestre doit être disponible. Dans ce contexte, nous proposons une solution qui permet la coordination d’un ensemble de drones afin de maintenir un chemin optimal entre la cible et la station terrestre. Notre solution se révèle efficace en matière de gain en temps et en énergie. Nous avons également proposé une solution basée sur des protocoles hiérarchiques pour économiser plus d’énergie dans le processus de communication avec la station terrestre. Nous avons également développé une autre solution qui permet d’économiser plus d’énergie en forçant les nœuds égoïstes à participer dans le réseau et d’assurer le relais de paquets lorsqu’ils sont sollicités. En effet, si un nœud égoïste refuse de router des paquets d’autres nœuds, cela induit une charge supplémentaire pour le reste des nœuds du réseau. Nous avons validé l’apport de l’ensemble de nos solutions par évaluation de performances à l’aide de simulations. / The emergence of small and inexpensive Unmanned Aerial Vehicles (UAVs) promotes their use in several applications. UAVs are usually equipped with different sensors and have the ability to communicate via wireless connections. Their capability to fly freely in the space offers new opportunities to monitoring and tracking applications. A Flying Ad hoc Network (FANET) is composed of a fleet of autonomous UAVs and is used for monitoring applications in hostile environments, surveillance or site inspection. FANETs could also be used for filming special events such as bike races or soccer matches, so, the connections must guarantee a minimum of quality of service. In FANETs, saving energy of UAVs that have limited battery is very challenging and protecting the network from malicious attacks is even more difficult. In this thesis, we focus on tracking and filming a moving target using a fleet of UAVs. Since the target is moving, the UAVs have to follow it continuously, and a path to the ground station must be available. In this context, we propose an efficient solution that allows the coordination of the UAVs to maintain an optimal path between the target and the ground station. The proposed solution is time and energy efficient. We also propose a solution based on hierarchical protocols to save more energy in the communication process with the ground station. Another solution that allows energy saving is to force selfish nodes to participate in the network to route received packets towards their destination. Indeed, a selfish node is concerned only about its own welfare, refusing to route packets of other node, causing an extra charge for the rest of nodes in the network. We validate our solutions through simulation campaigns.
46

Data collection of mobile sensor networks by drones

Ma, Xiaoyan 06 November 2017 (has links) (PDF)
Data collection by autonomous mobile sensor arrays can be coupled with the use of drones which provide a low-cost, easily deployable backhauling solution. These means of collection can be used to organize temporary events (sporting or cultural) or to carry out operations in difficult or hostile terrain. The aim of this thesis is to propose effective solutions for communication between both mobile sensors on the ground and on the edge-to-ground link. For this purpose, we are interested in scheduling communications, routing and access control on the sensor / drone link, the mobile collector. We propose an architecture that meets the constraints of the network. The main ones are the intermittence of the links and therefore the lack of connectivity for which solutions adapted to the networks tolerant to the deadlines are adopted. Given the limited opportunities for communication with the drone and the significant variation in the physical data rate, we proposed scheduling solutions that take account of both the contact time and the physical flow rate. Opportunistic routing is also based on these two criteria both for the selection of relay nodes and for the management of queues. We wanted to limit the overhead and propose efficient and fair solutions between mobile sensors on the ground. The proposed solutions have proved superior to conventional scheduling and routing solutions. Finally, we proposed a method of access combining a random access with contention as well as an access with reservation taking into account the aforementioned criteria. This flexible solution allows a network of dense mobile sensors to get closer to the performance obtained in an oracle mode. The proposed solutions can be implemented and applied in different application contexts for which the ground nodes are mobile or easily adapted to the case where the nodes are static.
47

Design and analysis of a practical large-force piezoelectric inchworm motor with a novel force duplicator

Williams, Edward Francis January 2014 (has links)
The work presented in this dissertation on piezoelectric inchworm motors (IWM) is part of a process to gain an understanding of the design, analysis and testing of this smart actuator technology. This work will form the foundation of what will hopefully lead to the realisation of a production-ready IWM design to be used in energy-scarce, battery-operated Unmanned Aerial Vehicles (UAVs), and forms part of a larger national drive to expand the UAV industry in South Africa. Although the principles used in the design of IWMs are well known, a new innovation is employed. A novel way to increase the force capacity of IWMs without compromising on the speed or displacement when compared to conventional methods is shown to be effective, and was used for the first time on IWMs. The use of a simple design equation is demonstrated to be useful in predicting the load limits and step displacements. Challenges of finding a correlation between predicted and measured performance values are discussed and solutions are presented. The history of IWMs and some background on piezoelectricity are given for the reader not familiar with these. The use of micro ridges on the clamp mechanisms is explored. The effects of the control signals on the mechanism of the motor are discussed in detail and some important comments on electrical controllers are made. The emphasis is on designing a strong motor that capitalises on the high-force density of piezoelectric material. / Dissertation (MEng)--University of Pretoria, 2014. / gm2014 / Mechanical and Aeronautical Engineering / unrestricted
48

Experimental And Numerical Studies On Flame Stability And Optimization Of A Compact Trapped Vortex Combustor

Agarwal, Krishna Kant 12 1900 (has links) (PDF)
A new Trapped Vortex Combustor (TVC) concept has been studied for applications such as those in Unmanned Aerial Vehicles (UAVs) as it offers potential for superior flame stability and low pressure loss. Flame stability is ensured by a strong vortex in a physical cavity attached to the combustor wall, and low pressure loss is due to the absence of swirl. Earlier studies on a compact combustor concept showed that there are issues with ensuring stable combustion over a range of operating conditions. The present work focuses on experimental studies and numerical simulations to study the stability issues and performance optimization in this compact single-cavity TVC configuration. For performing numerical simulations, an accurate and yet computationally affordable Modified Eddy Dissipation Concept combustion model is built upon the KIVA-3V platform to account for turbulence-chemistry interactions. Detailed validation with a turbulent non-premixed CH4/H2/N2 flame from literature showed that the model is sufficiently accurate and the effect of various simulation strategies is assessed. Transient flame simulation capabilities are assessed by comparison with experimental data from an acoustically excited oscillatory H2-air diffusion flame reported in literature. Subsequent to successful validation of the model, studies on basic TVC flow oscillations are performed. Frequencies of flow oscillations are found to be independent of flow velocities and cavity length, but dependent on the cavity depth. Cavity injection and combustion individually affect the magnitude of flow oscillations but do not significantly alter the resonant frequencies. Reacting flow experiments and flow visualization studies in an existing experimental TVC rig with optical access and variable cavity L/D ratio show that TVC flame stability depends strongly on the cavity air velocity. A detailed set of numerical simulations also confirms this and helps to identify three basic modes of TVC flame stabilization. A clockwise cavity vortex stabilized flame is formed at low cavity air velocities relative to the mainstream, while a strong anticlockwise cavity vortex is formed at high cavity air velocities and low L/Ds. At intermediate conditions, the cavity vortex structure is found to be in a transition state which leads to large scale flame instabilities and flame blow-out. For solving the flame instability problem, a novel strategy of incorporating a flow guide vane is proposed to establish the advantageous anticlockwise vortex without the use of cavity air. Experimental results with the modified configuration are quite encouraging for TVC flame stability at laboratory conditions, while numerical results show good stability even at extreme operating conditions. Further design optimization studies are performed in a multi-parameter space using detailed simulations. From the results, a strategy of using inclined struts in the main flow path along with the flow guide vane seems most promising. This configuration is tested experimentally and results pertaining to pressure drop, pattern factor and flame stability are found to be satisfactory.
49

Bezpilotní letadla jako nástroj americké zahraniční politiky v boji proti terorismu / The military unmanned aerial vehicles as an instrument of American foreign policy in the fight against terrorism

Frumar, Josef January 2014 (has links)
This diploma thesis deals with the use of military unmanned aerial vehicles as a instrument of American foreign policy in the fight against terrorism. It covers their potential impact on terrorist organizations, for instance their change in behavior and warfare. It addresses the efficiency of unmanned aerial vehicles as a warfare from various perspectives, for instance in terms of number of civilian casualties or killed senior terrorist leaders. It also compares the military unmanned aerial vehicles with other alternatives of fight against terrorism and analyzes their use from strategic and tactical point of view. The last chapter indicates the potential scenarios resulting from their use for the United States, international system and security and for world itself.
50

OBJECT-BASED LAND COVER CLASSIFICATION OF UAV TRUE COLOR IMAGERY

Unknown Date (has links)
Land cover classification is necessary for understanding the state of the surface of the Earth at varying regions of interest. Knowledge of the Earth’s surface is critical in land-use planning, especially for the project study area Jupiter Inlet Lighthouse Outstanding Natural Area, where various vegetation, wild-life, and cultural components rely on adequate land-cover knowledge. The purpose of this research is to demonstrate the capability of UAV true color imagery for land cover classification. In addition to the objective of land cover classification, comparison of varying spatial resolutions of the imagery will be analyzed in the accuracy assessment of the output thematic maps. These resolutions will also be compared at varying training sample sizes to see which configuration performed best. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

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