The theory of Lagrangian Coherent Structures (LCS) enables prediction of material transport by turbulent winds, such as those observed in the Earth's Atmospheric Boundary Layer. In this dissertation, both theory and experimental methods are developed for utilizing small fixed-wing unmanned aircraft systems (UAS) in detecting these atmospheric coherent structures. The dissertation begins by presenting relevant literature on both LCS and airborne wind estimation. Because model-based wind estimation inherently depends on high quality models, a Flight Dynamic Model (FDM) suitable for a small fixed-wing aircraft in turbulent wind is derived in detail. In this presentation, some new theoretical concepts are introduced concerning the proper treatment of spatial wind gradients, and a critical review of existing theories is presented. To enable model-based wind estimation experiments, an experimental approach is detailed for identifying a FDM for a small UAS by combining existing computational aerodynamic and data-driven approaches. Additionally, a methodology for determining wind estimation error directly resulting from dynamic modeling choices is presented and demonstrated. Next, some model-based wind estimation results are presented utilizing the experimentally identified FDM, accompanied by a discussion of model fidelity concerns and other experimental issues. Finally, an algorithm for detecting LCS from a single circling fixed-wing UAS is developed and demonstrated in an Observing System Simulation Experiment. The dissertation concludes by summarizing these contributions and recommending future paths for continuing research. / Doctor of Philosophy / In a natural or man-made disaster, first responders depend on accurate predictions of where the wind might carry hazardous material. A mathematical theory of Lagrangian Coherent Structures (LCS) has shown promise in ocean environments to improve these predictions, and the theory is also applicable to atmospheric flows near the Earth’s surface. This dissertation presents both theoretical and experimental research efforts towards employing small fixed-wing unmanned aircraft systems (UAS) to detect coherent structures in the Atmospheric Boundary Layer (ABL). These UAS fit several “gaps” in available sensing technology: a small aircraft responds significantly to wind gusts, can be steered to regions of interest, and can be flown in dangerous environments without risking the pilot’s safety. A key focus of this dissertation is to improve the quality of airborne wind measurements provided by inexpensive UAS, specifically by leveraging mathematical models of the aircraft. The dissertation opens by presenting the motivation for this research and existing literature on the topics. Next, a detailed derivation of a suitable Flight Dynamic Model (FDM) for a fixed-wing aircraft in a turbulent wind field is presented. Special attention is paid to the theories for including aerodynamic effects of flying in non-uniform winds. In preparation for wind measurement experiments, a practical method for obtaining better quality FDMs is presented which combines theoretically based and data-driven approaches. A study into the wind-measurement error incurred solely by mathematical modeling is presented, focusing on simplified forms of the FDM which are common in aerospace engineering. Wind estimates which utilize our best available model are presented, accompanied by discussions of the model accuracy and additional wind measurement concerns. A method is developed to detect coherent structures from a circling UAS which is providing wind information, presumably via accurate model based estimation. The dissertation concludes by discussing these conclusions and directions for future research which have been identified during these pursuits.

The focus of this dissertation is on developing novel methods and extending existing ones to improve the security and reliability of fixed-wing unmanned aircraft systems (UAS). Specifically, we focus on three strands of work: i) designing UAS controllers with performance guarantees using the robust control framework, ii) developing tools for detection and mitigation of physical-layer security threats in UAS, and iii) extending tools from compositional verification to design and verify complex systems such as UAS. Under the first category, we use the robust H-infinity control approach to design a linear parameter-varying (LPV) path-following controller for a fixed-wing UAS that enables the aircraft to follow any arbitrary planar curvature-bounded path under significant environmental disturbances. Three other typical path-following controllers, namely, a linear time-invariant H-infinity controller, a nonlinear rate-tracking controller, and a PID controller, are also designed. We study the relative merits and limitations of each approach and demonstrate through extensive simulations and flight tests that the LPV controller has the most consistent position tracking performance for a wide array of geometric paths. Next, convex synthesis conditions are developed for control of distributed systems with uncertain initial conditions, whereby independent norm constraints are placed on the disturbance input and the uncertain initial state. Using this approach, we design a distributed controller for a network of three fixed-wing UAS and demonstrate the improvement in the transient response of the network when switching between different trajectories. Pertaining to the second strand of this dissertation, we develop tools for detection and mitigation of security threats to the sensors and actuators of UAS. First, a probabilistic framework that employs tools from statistical analysis to detect sensor attacks on UAS is proposed. By incorporating knowledge about the physical system and using a Bayesian network, the proposed approach minimizes the false alarm rates, which is a major challenge for UAS that operate in dynamic and uncertain environments. Next, the security vulnerabilities of existing UAS actuators are identified and three different methods of differing complexity and effectiveness are proposed to detect and mitigate the security threats. While two of these methods involve developing algorithms and do not require any hardware modification, the third method entails hardware modifications to the actuators to make them resilient to malicious attacks. The three methods are compared in terms of different attributes such as computational demand and detection latency. As for the third strand of this dissertation, tools from formal methods such as compositional verification are used to design an unmanned multi-aircraft system that is deployed in a geofencing application, where the design objective is to guarantee a critical global system property. Verifying such a property for the multi-aircraft system using monolithic (system-level) verification techniques is a challenging task due to the complexity of the components and the interactions among them. To overcome these challenges, we design the components of the multi-aircraft system to have a modular architecture, thereby enabling the use of component-based reasoning to simplify the task of verifying the global system property. For component properties that can be formally verified, we employ results from Euclidean geometry and formal methods to prove those properties. For properties that are difficult to be formally verified, we rely on Monte Carlo simulations. We demonstrate how compositional reasoning is effective in reducing the use of simulations/tests needed in the verification process, thereby increasing the reliability of the unmanned multi-aircraft system. / Doctor of Philosophy / Given the safety-critical nature of many unmanned aircraft systems (UAS), it is crucial for stake holders to ensure that UAS when deployed behave as intended despite atmospheric disturbances, system uncertainties, and malicious adversaries. To this end, this dissertation deals with developing novel methods and extending existing ones to improve the security and reliability of fixed-wing UAS. Specifically, we focus on three key areas: i) designing UAS controllers with performance guarantees, ii) developing tools for detection and mitigation of security threats to sensors and actuators of UAS, and iii) extending tools from compositional verification to design and verify complex systems such as UAS. Pertaining to the first area, we design controllers for UAS that would enable the aircraft to follow any arbitrary planar curvature-bounded path under significant atmospheric disturbances. Four different controllers of differing complexity and effectiveness are designed, and their relative merits and limitations are demonstrated through extensive simulations and flight tests. Next, we develop control design tools to improve the transient response of multi-mission UAS networks. Using these tools, we design a controller for a network of three fixed-wing UAS and demonstrate the improvement in the transient response of the network when switching between different trajectories. As for the contributions in the second area, we develop tools for detection and mitigation of security threats to the sensors and actuators of UAS. First, we propose a framework for detecting sensor attacks on UAS. By judiciously using knowledge about the physical system and techniques from statistical analysis, the framework minimizes the false alarm rates, which is a major challenge in designing attack detection systems for UAS. Then, we focus on another important attack surface of the UAS, namely, the actuators. Here, we identify the security vulnerabilities of existing UAS actuators and propose three different methods to detect and mitigate the security threats. The three methods are compared in terms of different attributes such as computational demand, detection latency, need for hardware modifications, etc. In regard to the contributions in the third area, tools from compositional verification are used to design an unmanned multi-aircraft system that is tasked to track and compromise an aerial encroacher, wherein the multi-aircraft system is required to satisfy a global system property pertaining to collision avoidance and close tracking. A common approach to verifying global properties of systems is monolithic verification where the whole system is analyzed. However, such an approach becomes intractable for complex systems like the multi-aircraft system considered in this work. We overcome this difficulty by employing the compositional verification approach, whereby the problem of verifying the global system property is reduced to a problem of reasoning about the system’s components. That being said, even formally verifying some component properties can be a formidable task; in such cases, one has to rely on Monte Carlo simulations. By suitably designing the components of the multi-aircraft system to have a modular architecture, we show how one can perform focused component-level simulations rather than conduct simulations on the whole system, thereby limiting the use of simulations during the verification process and, as a result, increasing the reliability of the system.

In the past few years, there has been a growth in Unmanned Aircraft Systems (UAS) numbers in segregated airspace. However, although there is an interest in integrating large UAS into non-segregated airspace, the safety challenges on its integration arise from the inclusion of new ways of reaching unsafe states into the airspace. Furthermore, Air Traffic Controllers (ATCo) aim to o?er appropriate levels of safety and efficiency and to solve issues present in complex situations. Although the UAS technology may be used in di?erent situations and brings several advantages to the airspace (e.g. efficiency), it may bring uncertainties due to the fact that ATCos may not be familiar with them. Throughout the years, this impact may be lower then it is nowadays due to the fact that the present lack of familiarity in the relationship between UAS and ATCo contributes to higher workload levels. Furthermore, Terminal Maneuvering Area (TMA), which composes the controlled airspace and in which the final sector in contained, is a critical control area normally established at the confluence of Air Traffic Service (ATS) routes in which the aircraft tend to be closer to each other. Thus, operations in this particular area are conducted carefully and, in order to achieve desirable levels of safety and efficiency, standard procedures are established. In some cases, however, standard procedures cannot be followed and the sequencing of the aircraft during the approach, which is a highly challenging task due to complex maneuvers constraints, must be performed by the ATCo in a manner to respect the minimum separation of aircraft and to avoid flights through cumulonimbus (CB). Finally, the main goal of defining a final arrival segment is to deliver the set of aircraft from the final sector of the TMA to the final phase of its landing procedure, i.e., the final approach, considering the operation efficiency and safety. The main objective of this research is to propose a parallel swarm-based method for optimizing final aircraft arrival segments design, i.e., routes that connects the final sector to the Initial Approach Fix (IAF), considering the UAS presence. This is conducted from two perspectives: ATCo workload, which is related to safety, and sequencing duration, which is related to efficiency. Furthermore, di?erent phases of UAS integration are considered, i.e., from early stages of its integration to a mature stage of its operation by means of the Technology Maturity Level (TML) usage, which is a scale that measure the familiarity between the ATCo with the aircraft. Finally, the solutions consider airspace restrictions such as minimum separation between aircraft and bad weather conditions, i.e., the presence of cumulonimbus (CB). The experiments conducted show that this approach is able to build safe and efficient solution even in situations with a high number of aircraft. / Nos últimos anos, houve um crescimento, no espaço aéreo segregado, nos números do Veículos Aéreos Não-Tripulados (VANT). No entanto, embora exista interesse em integrar grandes VANT em espaço aéreo não-segregado, os desafios de segurança decorrem da inclusão de novas formas de alcançar estados inseguros no espaço aéreo (ATCo) tem como objetivo oferecer níveis adequados de segurança e eficiência e resolver problemas presentes em situações complexas. Embora VANTs possam ser usados em diferentes situações e trazem várias vantagens para o espaço aéreo (por exemplo, eficiência), podem trazer incertezas devido ao fato de que os ATCos não estão familiarizados com essa tecnologia. Ao longo dos anos, esse impacto pode ser menor, e atualmente a falta de familiaridade na relação entre VANT e ATCo contribui para níveis mais altos de carga de trabalho. Além disso, a Área Terminal (TMA), que compõe o espaço aéreo controlado, é uma área de controle crítico normalmente estabelecida na confluência de rotas do Servi¸co de Tráfego Aéreo (ATS), nas quais as aeronaves tendem a estar mais próximas umas das outras. Assim, as operações nesta área particular são realizadas com cuidado e, para alcançar níveis desejáveis de segurança e eficiência, os procedimentos padrão são estabelecidos. Em alguns casos, no entanto, procedimentos padrão não podem ser seguidos e o sequenciamento da aeronave durante a aproximação, que é uma tarefa desafiadora por conta das restrições de manobras complexas, deve ser realizada pelo ATCo de forma a garantir separação mínima entre aeronaves e evitar voos através de cumulonimbus (CB). Finalmente, o principal objetivo de definir um segmento de chegada final ´e entregar o conjunto de aeronaves do setor final, da TMA, para a fase final do seu procedimento de pouso, ou seja, a aproximação final, considerando a eficiência e a segurança da operação. O objetivo desta pesquisa é propor um método paralelo baseado em enxame para otimizar o projeto final de segmentos de chegada de aeronaves, ou seja, rotas que conectem o setor final com o Fixo de Aproximação Inicial (IAF), considerando a presença de VANTs. Esse processo ´e conduzido a partir de duas perspectivas: a carga de trabalho do ATCo, que est´a relacionada à segurança, e a duração da sequenciamento, que está relacionado à eficiência. Além disso, são consideradas diferentes fases da integração de VANTs, ou seja, desde os primeiros estágios de sua integra¸c~ao at´e um estágio maduro de sua operação por meio do uso do Nível de Maturidade Tecnológica (TML), que é uma escala que mede a familiaridade entre o ATCo e a aeronave. Finalmente, as soluções consideram as restrições do espaço aéreo, como a separação mínima entre aeronaves e condições climáticas adversas, isto é, a presença de cumulonimbus (CB). Os experimentos realizados mostram que essa abordagem é capaz de criar soluções seguras e eficientes mesmo em situações com um grande número de aeronaves.

A tendência da indústria aeronáutica comercial é o desenvolvimento de aviões mais eficientes em termos de consumo de combustível e custos operacionais diretos. No que diz respeito ao consumo de combustível, algumas estratégias da indústria aeronáutica são o uso de uma aerodinâmica mais eficiente, materiais mais leves e motores e sistemas mais eficientes. O motor turbo jato convencional fornece potência elétrica para os sistemas de cabine (luzes, entretenimento, cozinha) e aviônicos, potência hidráulica para os sistemas de controle de vôo e potência pneumática para proteção contra formação de gelo e unidade de controle ambiental. Motores mais eficientes e diferentes tipos de arquiteturas de sistemas, como os sistemas mais elétricos, são promessas para reduzir o consumo de combustível. A fim de comparar os processos energéticos das arquiteturas de sistemas e motor numa mesma base, a exergia é o verdadeiro valor termodinâmico que deve ser utilizada como ferramenta de decisão para projeto de sistemas, motores e aeronaves, assim como parâmetro de otimização. Trabalhos de outros autores focaram apenas em redução da exergia destruída e nenhum trabalho apresentou um método harmonizador que consolide os parâmetros já existentes e crie outros parâmetros comparativos entre sistemas. Este trabalho propõe um método baseado em análise exergética para concepção e avaliação de sistemas aeronáuticos, que pode ser aplicado ao projeto de uma nova aeronave desde as fases de estudos conceituais e ante projeto até a fase de definição. O método pode suportar o projeto completo de uma aeronave como um único sistema, pois integra todos os subsistemas numa mesma estrutura. Os principais índices propostos neste trabalho são: exergia destruída, rendimento exergético, consumo específico de exergia, exergia destruída na missão e eficiência exergética da missão. Este trabalho também apresenta resultados comparativos ao aplicar o método exergético entre versões de uma mesma aeronave comercial regional, considerando sistemas de gerenciamento de ar (sistema de extração pneumática, unidade de controle ambiental e sistema de proteção contra formação de gelo) convencionais e mais elétricos. Para tanto, quantificam-se os requisitos de dimensionamento e faz-se a modelagem termodinâmica dos sistemas convencionais e mais elétricos, assim como a modelagem do motor para ambas as versões da aeronave. Os resultados da aplicação do método exergético evidenciam que os sistemas convencionais de gerenciamento de ar são os maiores consumidores de exergia de uma aeronave e que a substituição por sistemas mais elétricos é uma boa alternativa para melhorar a eficiência termodinâmica da mesma. Considerando os mesmos requisitos exergéticos de tração entre as duas versões de aeronaves, a abordagem mais elétrica apresenta maiores rendimentos exergéticos de missão em torno de 0,5%. Entretanto, a análise completa também leva em conta as diferenças de peso e arrasto entre as duas versões de aeronaves, a qual evidencia que a escolha por sistemas mais elétricos deve ser guiada pela variação dos requisitos de tração que esta aeronave possui com relação ao avião com sistemas convencionais. / A tendency of the commercial aeronautical industry is to develop more efficient aircraft in terms of fuel consumption and direct operational costs. Regarding fuel consumption, some strategies of the aeronautical industry are to use more efficient aerodynamics, lightweight materials and more efficient engines and systems. The conventional turbo fan engine mainly provides electric power for cabin systems (lights, entertainment, galleys) and avionics, hydraulic power for flight control systems and bleed air for ice protection and environmental control systems. More efficient engines and different types of systems architectures, such as more electric systems, are a promise to reduce fuel consumption. In order to compare the energy processes of systems and engine architectures at the same basis, exergy is the true thermodynamic value that shall be used as a decision tool to aircraft systems and engine design, and also as an optimization tool. Other works have focused only on reduction of exergy destruction and none have presented a method that harmonizes and consolidates the existing comparative parameters and creates new parameters among systems. This work proposes a method based on exergy analysis for conception and assessment of aircraft systems, that can be applied to an aircraft project from the conceptual and preliminary designs to the detail design. The method can support the design of the complete vehicle as a system and all of its subsystems in a common framework. The main proposed parameters in this work are: exergy destruction, exergy efficiency, specific exergy consumption, mission exergy destruction and mission exergy efficiency. This work also presents comparative results by applying the method to conventional and more electric version of the same regional commercial aircraft, considering conventional and electric air management systems (bleed system, environmental control system and ice protection system). In order to, sizing requirements are evaluated and thermodynamic models are performed for both conventional and more electric air management systems, and also engine models are performed for both aircraft. Results show that conventional air management systems are the higher exergy consumers among aircraft systems and the substitution for more electric systems is a good alternative to improve the aircraft thermodynamic efficiency. Considering the same thrust exergy requirements for both aircraft, the more electric version presents higher mission exergy efficiency around 0.5%. However, a complete trade-off also takes into account weight and drag differences of both versions, which makes evident that the selection for more electric systems must be driven by the variation of thrust requirements between more electric and conventional aircraft.

<p></p><p>Visual inspection is the primary means of ensuring the safety and functionality of in-service bridges in the United States and owners spend considerable resources on such inspections. While the Federal Highway Administration (FHWA) and many state departments of transportation have guidelines related to inspector qualification, training, and certification, an inspector’s actual capability to identify defects in the field under these guidelines is unknown. This research aimed to address the knowledge gap surrounding visual inspection performance for steel bridges in order to support future advances in inspection and design procedures. Focusing primarily on fatigue crack detection, this research also considered the ability of inspectors to accurately and consistently estimate section loss in steel bridge members. </p> <p> </p> <p>Inspection performance was evaluated through a series of simulated bridge inspections performed in representative in-situ conditions. First, this research describes the results from 30 hands-on, visual inspections performed on full size bridge specimens with known fatigue cracks. Probability of Detection (POD) curves were fit to the inspection results and the 50% and 90% detection rate crack lengths were determined. The variability in performance was large, and only a small amount of the variance could be explained by individual characteristics or environmental conditions. Based on the results, recommendations for improved training methods, inspection procedures, and equipment were developed. Above all, establishment of a performance based qualification system for bridge inspectors is recommended to confirm that a satisfactory level of performance is consistently achieved in the field. </p> <p> </p> <p>Long term, managing agencies may eschew traditional hands-on bridge inspection methods in favor of emerging technologies imagined to provide improved results and fewer logistical challenges. This research investigated the potential for unmanned aircraft system (UAS) assistance during visual inspection of steel bridges. Using the same specimens as in the hands-on inspections, four UAS-assisted field inspections and 19 UAS-assisted desk inspections were performed. A direct comparison was made between performance in the hands-on and UAS-assisted inspections, as well as between performance in the two types of UAS-assisted inspections. Again, significant variability was present in the results suggesting that human factors continue to have a substantial influence on inspection performance, regardless of inspection method. </p> <p> </p> <p>Finally, to expand the findings from the crack detection inspections, the lower chord from a deck truss was used to investigate variability in the inspection of severely corroded steel tension members. Five inspectors performed a hands-on inspection of the specimen and four engineers calculated the load rating for the same specimen. Significant variability was observed in how inspectors recorded thickness measurements during the inspections and engineers interpreted the inspection reports and applied the code requirements. </p><br><p></p>

In the past few years, there has been a growth in Unmanned Aircraft Systems (UAS) numbers in segregated airspace. However, although there is an interest in integrating large UAS into non-segregated airspace, the safety challenges on its integration arise from the inclusion of new ways of reaching unsafe states into the airspace. Furthermore, Air Traffic Controllers (ATCo) aim to o?er appropriate levels of safety and efficiency and to solve issues present in complex situations. Although the UAS technology may be used in di?erent situations and brings several advantages to the airspace (e.g. efficiency), it may bring uncertainties due to the fact that ATCos may not be familiar with them. Throughout the years, this impact may be lower then it is nowadays due to the fact that the present lack of familiarity in the relationship between UAS and ATCo contributes to higher workload levels. Furthermore, Terminal Maneuvering Area (TMA), which composes the controlled airspace and in which the final sector in contained, is a critical control area normally established at the confluence of Air Traffic Service (ATS) routes in which the aircraft tend to be closer to each other. Thus, operations in this particular area are conducted carefully and, in order to achieve desirable levels of safety and efficiency, standard procedures are established. In some cases, however, standard procedures cannot be followed and the sequencing of the aircraft during the approach, which is a highly challenging task due to complex maneuvers constraints, must be performed by the ATCo in a manner to respect the minimum separation of aircraft and to avoid flights through cumulonimbus (CB). Finally, the main goal of defining a final arrival segment is to deliver the set of aircraft from the final sector of the TMA to the final phase of its landing procedure, i.e., the final approach, considering the operation efficiency and safety. The main objective of this research is to propose a parallel swarm-based method for optimizing final aircraft arrival segments design, i.e., routes that connects the final sector to the Initial Approach Fix (IAF), considering the UAS presence. This is conducted from two perspectives: ATCo workload, which is related to safety, and sequencing duration, which is related to efficiency. Furthermore, di?erent phases of UAS integration are considered, i.e., from early stages of its integration to a mature stage of its operation by means of the Technology Maturity Level (TML) usage, which is a scale that measure the familiarity between the ATCo with the aircraft. Finally, the solutions consider airspace restrictions such as minimum separation between aircraft and bad weather conditions, i.e., the presence of cumulonimbus (CB). The experiments conducted show that this approach is able to build safe and efficient solution even in situations with a high number of aircraft. / Nos últimos anos, houve um crescimento, no espaço aéreo segregado, nos números do Veículos Aéreos Não-Tripulados (VANT). No entanto, embora exista interesse em integrar grandes VANT em espaço aéreo não-segregado, os desafios de segurança decorrem da inclusão de novas formas de alcançar estados inseguros no espaço aéreo (ATCo) tem como objetivo oferecer níveis adequados de segurança e eficiência e resolver problemas presentes em situações complexas. Embora VANTs possam ser usados em diferentes situações e trazem várias vantagens para o espaço aéreo (por exemplo, eficiência), podem trazer incertezas devido ao fato de que os ATCos não estão familiarizados com essa tecnologia. Ao longo dos anos, esse impacto pode ser menor, e atualmente a falta de familiaridade na relação entre VANT e ATCo contribui para níveis mais altos de carga de trabalho. Além disso, a Área Terminal (TMA), que compõe o espaço aéreo controlado, é uma área de controle crítico normalmente estabelecida na confluência de rotas do Servi¸co de Tráfego Aéreo (ATS), nas quais as aeronaves tendem a estar mais próximas umas das outras. Assim, as operações nesta área particular são realizadas com cuidado e, para alcançar níveis desejáveis de segurança e eficiência, os procedimentos padrão são estabelecidos. Em alguns casos, no entanto, procedimentos padrão não podem ser seguidos e o sequenciamento da aeronave durante a aproximação, que é uma tarefa desafiadora por conta das restrições de manobras complexas, deve ser realizada pelo ATCo de forma a garantir separação mínima entre aeronaves e evitar voos através de cumulonimbus (CB). Finalmente, o principal objetivo de definir um segmento de chegada final ´e entregar o conjunto de aeronaves do setor final, da TMA, para a fase final do seu procedimento de pouso, ou seja, a aproximação final, considerando a eficiência e a segurança da operação. O objetivo desta pesquisa é propor um método paralelo baseado em enxame para otimizar o projeto final de segmentos de chegada de aeronaves, ou seja, rotas que conectem o setor final com o Fixo de Aproximação Inicial (IAF), considerando a presença de VANTs. Esse processo ´e conduzido a partir de duas perspectivas: a carga de trabalho do ATCo, que est´a relacionada à segurança, e a duração da sequenciamento, que está relacionado à eficiência. Além disso, são consideradas diferentes fases da integração de VANTs, ou seja, desde os primeiros estágios de sua integra¸c~ao at´e um estágio maduro de sua operação por meio do uso do Nível de Maturidade Tecnológica (TML), que é uma escala que mede a familiaridade entre o ATCo e a aeronave. Finalmente, as soluções consideram as restrições do espaço aéreo, como a separação mínima entre aeronaves e condições climáticas adversas, isto é, a presença de cumulonimbus (CB). Os experimentos realizados mostram que essa abordagem é capaz de criar soluções seguras e eficientes mesmo em situações com um grande número de aeronaves.

Excessive erosion and fine sediment delivery to river corridors and receiving waters degrade aquatic habitat, add to nutrient loading, and impact infrastructure. Understanding the sources and movement of sediment within watersheds is critical for assessing ecosystem health and developing management plans to protect natural and human systems. As our changing climate continues to cause shifts in hydrological regimes (e.g., increased precipitation and streamflow in the northeast U.S.), the development of tools to better understand sediment dynamics takes on even greater importance. In this research, advanced geomatics and machine learning are applied to improve the (1) monitoring of streambank erosion, (2) understanding of event sediment dynamics, and (3) prediction of sediment loading using meteorological data as inputs. Streambank movement is an integral part of geomorphic changes along river corridors and also a significant source of fine sediment to receiving waters. Advances in unmanned aircraft systems (UAS) and photogrammetry provide opportunities for rapid and economical quantification of streambank erosion and deposition at variable scales. We assess the performance of UAS-based photogrammetry to capture streambank topography and quantify bank movement. UAS data were compared to terrestrial laser scanner (TLS) and GPS surveying from Vermont streambank sites that featured a variety of bank conditions and vegetation. Cross-sectional analysis of UAS and TLS data revealed that the UAS reliably captured the bank surface and was able to quantify the net change in bank area where movement occurred. Although it was necessary to consider overhanging bank profiles and vegetation, UAS-based photogrammetry showed significant promise for capturing bank topography and movement at fine resolutions in a flexible and efficient manner. This study also used a new machine-learning tool to improve the analysis of sediment dynamics using three years of high-resolution suspended sediment data collected in the Mad River watershed. A restricted Boltzmann machine (RBM), a type of artificial neural network (ANN), was used to classify individual storm events based on the visual hysteresis patterns present in the suspended sediment-discharge data. The work expanded the classification scheme typically used for hysteresis analysis. The results provided insights into the connectivity and sources of sediment within the Mad River watershed and its tributaries. A recurrent counterpropagation network (rCPN) was also developed to predict suspended sediment discharge at ungauged locations using only local meteorological data as inputs. The rCPN captured the nonlinear relationships between meteorological data and suspended sediment discharge, and outperformed the traditional sediment rating curve approach. The combination of machine-learning tools for analyzing storm-event dynamics and estimating loading at ungauged locations in a river network provides a robust method for estimating sediment production from catchments that informs watershed management.

A tendência da indústria aeronáutica comercial é o desenvolvimento de aviões mais eficientes em termos de consumo de combustível e custos operacionais diretos. No que diz respeito ao consumo de combustível, algumas estratégias da indústria aeronáutica são o uso de uma aerodinâmica mais eficiente, materiais mais leves e motores e sistemas mais eficientes. O motor turbo jato convencional fornece potência elétrica para os sistemas de cabine (luzes, entretenimento, cozinha) e aviônicos, potência hidráulica para os sistemas de controle de vôo e potência pneumática para proteção contra formação de gelo e unidade de controle ambiental. Motores mais eficientes e diferentes tipos de arquiteturas de sistemas, como os sistemas mais elétricos, são promessas para reduzir o consumo de combustível. A fim de comparar os processos energéticos das arquiteturas de sistemas e motor numa mesma base, a exergia é o verdadeiro valor termodinâmico que deve ser utilizada como ferramenta de decisão para projeto de sistemas, motores e aeronaves, assim como parâmetro de otimização. Trabalhos de outros autores focaram apenas em redução da exergia destruída e nenhum trabalho apresentou um método harmonizador que consolide os parâmetros já existentes e crie outros parâmetros comparativos entre sistemas. Este trabalho propõe um método baseado em análise exergética para concepção e avaliação de sistemas aeronáuticos, que pode ser aplicado ao projeto de uma nova aeronave desde as fases de estudos conceituais e ante projeto até a fase de definição. O método pode suportar o projeto completo de uma aeronave como um único sistema, pois integra todos os subsistemas numa mesma estrutura. Os principais índices propostos neste trabalho são: exergia destruída, rendimento exergético, consumo específico de exergia, exergia destruída na missão e eficiência exergética da missão. Este trabalho também apresenta resultados comparativos ao aplicar o método exergético entre versões de uma mesma aeronave comercial regional, considerando sistemas de gerenciamento de ar (sistema de extração pneumática, unidade de controle ambiental e sistema de proteção contra formação de gelo) convencionais e mais elétricos. Para tanto, quantificam-se os requisitos de dimensionamento e faz-se a modelagem termodinâmica dos sistemas convencionais e mais elétricos, assim como a modelagem do motor para ambas as versões da aeronave. Os resultados da aplicação do método exergético evidenciam que os sistemas convencionais de gerenciamento de ar são os maiores consumidores de exergia de uma aeronave e que a substituição por sistemas mais elétricos é uma boa alternativa para melhorar a eficiência termodinâmica da mesma. Considerando os mesmos requisitos exergéticos de tração entre as duas versões de aeronaves, a abordagem mais elétrica apresenta maiores rendimentos exergéticos de missão em torno de 0,5%. Entretanto, a análise completa também leva em conta as diferenças de peso e arrasto entre as duas versões de aeronaves, a qual evidencia que a escolha por sistemas mais elétricos deve ser guiada pela variação dos requisitos de tração que esta aeronave possui com relação ao avião com sistemas convencionais. / A tendency of the commercial aeronautical industry is to develop more efficient aircraft in terms of fuel consumption and direct operational costs. Regarding fuel consumption, some strategies of the aeronautical industry are to use more efficient aerodynamics, lightweight materials and more efficient engines and systems. The conventional turbo fan engine mainly provides electric power for cabin systems (lights, entertainment, galleys) and avionics, hydraulic power for flight control systems and bleed air for ice protection and environmental control systems. More efficient engines and different types of systems architectures, such as more electric systems, are a promise to reduce fuel consumption. In order to compare the energy processes of systems and engine architectures at the same basis, exergy is the true thermodynamic value that shall be used as a decision tool to aircraft systems and engine design, and also as an optimization tool. Other works have focused only on reduction of exergy destruction and none have presented a method that harmonizes and consolidates the existing comparative parameters and creates new parameters among systems. This work proposes a method based on exergy analysis for conception and assessment of aircraft systems, that can be applied to an aircraft project from the conceptual and preliminary designs to the detail design. The method can support the design of the complete vehicle as a system and all of its subsystems in a common framework. The main proposed parameters in this work are: exergy destruction, exergy efficiency, specific exergy consumption, mission exergy destruction and mission exergy efficiency. This work also presents comparative results by applying the method to conventional and more electric version of the same regional commercial aircraft, considering conventional and electric air management systems (bleed system, environmental control system and ice protection system). In order to, sizing requirements are evaluated and thermodynamic models are performed for both conventional and more electric air management systems, and also engine models are performed for both aircraft. Results show that conventional air management systems are the higher exergy consumers among aircraft systems and the substitution for more electric systems is a good alternative to improve the aircraft thermodynamic efficiency. Considering the same thrust exergy requirements for both aircraft, the more electric version presents higher mission exergy efficiency around 0.5%. However, a complete trade-off also takes into account weight and drag differences of both versions, which makes evident that the selection for more electric systems must be driven by the variation of thrust requirements between more electric and conventional aircraft.

Small unmanned aircraft systems (UAS) are rapidly gaining popularity. As the excitement surrounding small UAS has grown, the Federal Aviation Administration (FAA) has repeatedly stated that UAS must be capable of detecting and avoiding manned and unmanned aircraft. In developing detect-and-avoid (DAA) technology, one of the key challenges is identifying a suitable sensor. Automatic Dependent Surveillance-Broadcast (ADS-B) has gained much attention in both the research and consumer sectors as a promising solution. While ADS-B has many positive characteristics, further analysis is necessary to determine if it is suitable as a DAA sensor in environments with high-density small UAS operations. To further the understanding of ADS-B, we present a characterization of ADS-B measurement error that is derived from FAA regulations. Additionally, we analyze ADS-B by examining its strengths and weaknesses from the perspective of DAA on small UAS. To demonstrate the need and method for estimation of ADS-B measurements, we compare four dynamic filters for accuracy and computational speed. The result of the comparison is a recommendation for the best filter for ADS-B estimation. We then demonstrate this filter by estimating ADS-B measurements that have been recorded from the National Airspace System (NAS). We also present a novel long-range, convex optimization-based path planner for ADS-B-equipped small UAS in the presence of intruder aircraft. This optimizer is tested using a twelve-state simulation of the ownship and intruders.We also consider the effectiveness of ADS-B in high-density airspace. To do this we present a novel derivation of the probability of interference for ADS-B based on the number of transmitting aircraft. We then use this probability to document the need for limited transmit range for ADS-B on small UAS. We further leverage the probability of interference for ADS-B, by creating a tool that can be used to analyze self-separation threshold (SST) and well clear (WC) definitions based on ADS-B bandwidth limitations. This tool is then demonstrated by evaluating current SST and WC definitions and making regulations recommendations based on the analysis. Coupling this tool with minimum detection range equations, we make a recommendation for well clear for small UAS in ADS-B congested airspace. Overall these contributions expand the understanding of ADS-B as a DAA sensor, provide viable solutions for known and previously unknown ADS-B challenges, and advance the state of the art for small UAS.

Unmanned Aerial Vehicle (UAV) är en benämning på en obemannad flygande farkost. UAV är en benämning för själva farkosten och därför har Unmanned Aircraft System (UAS) tagit över eftersom det är ett begrepp som rör hela systemet som förutom flygfarkost innefattar start, landning, markstation och kommunikationslänk. Inom mätningsteknik är UAS ett relativt nytt begrepp och tekniken har sin historia mestadels inom det militära området. Syftet med denna studie är att analysera samt utvärdera två programvaror och en molntjänst för bearbetning och framtagning av ortofoto från UAS-data. De frågor som ställts inför arbetet är: kan en molntjänst ersätta ett avancerat datorprogram vid generering av ortofoton? Kan dessa datorprogram ge ett bra resultat utan hjälp av andra GIS-program? Vilket program är enklast att förstå och använda samt vilka är skillnaderna mellan programmen? Dessa frågor har besvarats genom användning av insamlat data och för att få utvärderingen rättvis har därför tre olika dataset skapats. Programtjänsterna som har utvärderats är Agisoft PhotoScan 0.9.0 och Pix4UAV Desktop/Cloud 2.1.2. Insamling av data har skett genom en flygning med en oktokopter över Fågelmyratippen i Dalarna. Resultaten visar att priset snabbt blir högt om endast Pix4UAV Cloud används och att överlag är PhotoScan billigare än Pix4UAV Desktop. Kvalitetsrapporten som följer med varje projekt är överskådlig i PhotoScan och mer ingående i Pix4UAV Desktop/Cloud. Trots samma indata blir utdatat olika vid bearbetning av de olika programmen, till exempel skiljer sig markupplösningen åt mellan programmen. Generellt är PhotoScan tydligare på att visa hur arbetsprocessen går till. Supporten hos båda företagen är bra, tips och tricks finns på respektive hemsida. Till PhotoScan finns även en manual för nedladdning samt en YouTube-kanal med instruktionsvideor. De enda slutsatserna vi drar är att Pix4UAV Cloud inte klarar av att ersätta ett avancerat bildbehandlingsprogram och att för tillfället bör ytterligare ett GIS-program användas som komplement för att få bästa resultat. I övrigt har vi endast skrapat på ytan av programmen och rekommenderar att läsaren tar till sig det vi skrivit under resultat och diskussion för att sedan bilda sig en egen uppfattning med hjälp av respektive programs prövotid. Till sist presenteras förslag på vidare studier inom ämnet. / Unmanned Aerial Vehicle (UAV) is a term for a remote controlled airbornevehicle. Since UAV is an acronym for the vehicle itself, Unmanned Aircraft Systems(UAS) has therefore replaced UAV, as it is a concept related to the wholesystem, beside the vehicle it also includes landing, ground station andcommunications link. Within land surveying UAS is a relatively new concept asthe technology has its history mainly associated to the military. The purposeof this study is to analyze and evaluate two software and a cloud service for processingand preparation of orthophotos from data collected with a UAS. The questions tobe answered in this thesis are: Can a cloud service replace an advancedcomputer software for generating orthophotos? Can these produce good resultswithout the help of other GIS software? Which software is the easiest tounderstand and to use and what are the main differences. These questions wereanswered by using collected data, and to get the evaluation fair three datasetshave been created. The software being evaluated are Agisoft PhotoScan andPix4UAV desktop/cloud. The data collection was done by a flight with an octokopterover Fågelmyratippen in Dalarna. The results show that the price quicklybecomes high if only Pix4UAV Cloud is used and that generally PhotoScan ischeaper than Pix4UAV Desktop. The quality report that comes with each projectis easy to understand in PhotoScan but more detailed in Pix4UAV Desktop/Cloud. Despitethe use of same data the results vary when processed, for example the groundresolution. Generally PhotoScan is better at showing the work process. Eachcompany’s support is good and they both have tips and tricks at their websites.On the Agisoft webpage there is a manual available for download and they alsohave a YouTube-channel with instruction videos. The conclusion is that thecloud service is not capable of replacing an advance image processing software.Another conclusion is that for the moment another GIS-program should be used toget the best results. We like to point out that we only scratched the surfaceof the software and we recommend that the reader embrace what we write inresults and discussion to then form their own opinion by using the softwareevaluation period. I the last part we present subjects of further study.