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The expansion of wind power comes with additional risks for bird populations, one of which is the collision with wind turbine components, mainly the rotating blades. In order to mitigate this risk, few systems on the market propose solutions with modules that deter the birds from the wind turbine or trigger the temporary shutdown of the turbines.The thesis seeks to obtain a common view from different stakeholders in order to create a list of requirements that the bird protection systems must have so as to be accepted by all the parties involved in the wind industry in Sweden. In order to meet this objective, interviews were conducted with interested stakeholders. Consequently, the interviews were summarized and common points were extracted to create a list of requirements and additional suggestions.Firstly, a comprehensive literature review was done that has pointed out issues like impacts of wind farms on bird species, especially raptors, causes of bird mortality, environmental legislation in European Union and Sweden, and current solutions on mitigating the risk of collisions with wind turbines onshore. Additionally, the author looked up into the most efficient ways to engage the stakeholders in constructive discussions and develop an easy framework for presenting the requirements.The primary data was collected through interviews with stakeholders representing 12 organizations. In the next steps, the data was analyzed by summarizing each interview and identifying the common and differentiating points in respondents’ views and suggestions over automated bird mitigation systems. The identified points laid the basis for a list of requirements considered important for safe and efficient bird mitigation systems in Sweden. Among others, stakeholders identified that the most crucial issues regarding bird mitigation systems are the response time to shutdown of the turbine, distance from the birds’ species living areas, need of species identification in bad weather conditions and night time and overall financial feasibility of such technologies.

O crescimento do interesse pelas possíveis aplicações civis de Veículos Aéreos Não Tripulados (VANT) vem resultando em pressões por diversos setores da sociedade para a regulamentação do uso desse tipo de veículo, sobretudo em espaço aéreo não segregado. No entanto, uma vez que a segurança crítica (safety) no sistema de tráfego aéreo é um item de extrema importância, faz-se necessário aprofundar o conhecimento a respeito do assunto. A fim de se criarem meios que permitam um maior entendimento dos riscos de segurança associados a esse tipo de aplicação, propõe-se nesse trabalho uma abordagem baseada em modelagem e simulação computacional para avaliação de risco de colisão de VANT com outras aeronaves. Os conceitos utilizados para modelagem, implementação e avaliação do VANT são apresentados junto aos resultados preliminares obtidos. Também são apresentados o estado da arte do tema abordado e as atividades futuras de pesquisa a serem realizadas. / The growing interest in possible civil applications of Unmanned Aerial Vehicles (UAV) has resulted in pressure from various sectors of society to regulate the use of this type of vehicle, especially in non-segregated airspace. However, since the critical safety in the air traffic system is an item of major importance, it is necessary to deepen the knowledge on the subject. In order to create means to permit a better understanding of the safety risks associated with this type of application, it is proposed herein an approach based on computer modeling and simulation for assessment of collision risk of an UAV and other aircraft. The concepts used for modeling, implementation and evaluation of UAVs are presented along with preliminary results. Additionally, the state of the art of the theme discussed and future research activities to be performed are presented as well.

O crescimento do interesse pelas possíveis aplicações civis de Veículos Aéreos Não Tripulados (VANT) vem resultando em pressões por diversos setores da sociedade para a regulamentação do uso desse tipo de veículo, sobretudo em espaço aéreo não segregado. No entanto, uma vez que a segurança crítica (safety) no sistema de tráfego aéreo é um item de extrema importância, faz-se necessário aprofundar o conhecimento a respeito do assunto. A fim de se criarem meios que permitam um maior entendimento dos riscos de segurança associados a esse tipo de aplicação, propõe-se nesse trabalho uma abordagem baseada em modelagem e simulação computacional para avaliação de risco de colisão de VANT com outras aeronaves. Os conceitos utilizados para modelagem, implementação e avaliação do VANT são apresentados junto aos resultados preliminares obtidos. Também são apresentados o estado da arte do tema abordado e as atividades futuras de pesquisa a serem realizadas. / The growing interest in possible civil applications of Unmanned Aerial Vehicles (UAV) has resulted in pressure from various sectors of society to regulate the use of this type of vehicle, especially in non-segregated airspace. However, since the critical safety in the air traffic system is an item of major importance, it is necessary to deepen the knowledge on the subject. In order to create means to permit a better understanding of the safety risks associated with this type of application, it is proposed herein an approach based on computer modeling and simulation for assessment of collision risk of an UAV and other aircraft. The concepts used for modeling, implementation and evaluation of UAVs are presented along with preliminary results. Additionally, the state of the art of the theme discussed and future research activities to be performed are presented as well.

The majority of the road infrastructure in developing countries consists oftwo-lane highways with one lane in each travel direction. Operational efficiency of these highways is derived fromintermittent passing zones where fast vehicles are permitted by design to pass slow vehicles using the opposite traffic lane. Passing zonescontributeto reduction oftravel delay and queuing of fast vehiclesbehind slow vehicles. Thishoweverincreases crash risks between passing and opposite vehiclesespecially at high traffic volumesdue to reduction of passing opportunities.Reduction of passing-related crash risks is therefore a primary concern ofpolicy makers, planners, and highway design engineers. Despite the wide application of passing zones on two-lane highways, there is limited knowledge on the underlying causal mechanisms that exacerbate crash risks, and the essential tools to assess safety of the passing zones. This thesis presentsa methodology to appraisesafety of two-lane rural highways based on observed operation of passing zones.Theproposed methodology takes into accountthe impact of traffic and geometric factors onthe rate passing maneuvers end insidepassing zonesand in the no-passing zones, adequacy ofthe designpassing sight distance,and time-to-collision at the end of passing maneuvers.Thethesis is comprised offive papers addressing capacity and safety aspectsof passing zoneson two-lane rural highways. Paper Ipresents a review of the literature on capacity and safety of passing zones. Paper IIdiscusses adequacy of the design passing sight distance based on the sight distance required to complete a passing maneuverusing observed data. Paper IIIdiscusses formulation, estimation, and application of a model to predict the passing rate using geometric and traffic factors, and applications. Paper IVdiscusses risk appraisal of the passing process based on the probability to complete passing maneuvers with time-to-collision less than 3.0 seconds taking into account the accepted gap in the opposite direction and the passing duration. Paper Vdiscusses formulation and estimation of models to predict the probability and the rate at which passing maneuvers end in a no-passing zone, and applications. Resultsshow that passing zones of lengths between 1.30and 2.50km aregood for both operational efficiency and safety.Passing zones of lengths between 0.50and 1.30km exhibitincreasing crash risks resulting from delayed passing maneuvers thatend in the no-passing zone where the sight distance is limited to evadepotential collisions. Safety of these passing zones could be enhanced with additional signage to indicate the farthestpoint along a passing zone that maneuvers can be initiated so as not to end in a no-passing zone. Passing zones less than 0.50km compel drivers to commence passing maneuvers close to the beginning of the passing zone,and should be avoided during design for safety reasons. The results further show that the passing rate depends on the length of the passing zone, absolute vertical grade, traffic volume in two travel directions, directional split, 85thpercentile speed of free flow vehicles,and percent of heavy vehicles in the subject direction. The peak-passing rate also known as the passing capacity occurs at 200, 220, and 240vph in the subject direction for 50/50, 55/45, and 60/40directional splits, respectively. The rate at which passing maneuvers end in a no-passing zone increaseswith traffic volume and unequal distribution of traffic in two directions, absolute vertical grade, and percent of heavy vehiclesin the subject direction. The thesis furtherdiscusses practical applications of the study findings in highway planning and design to enhancesafety and improve operational efficiency of two-lane rural highways. / <p>QC 20151106</p>

Le développement des véhicules autonomes a reçu une attention croissant ces dernières années, notamment les secteurs de la défense et de l'industrie automobile. L'intérêt pour l'industrie automobile est motivé par la conception de véhicules sûrs et confortables. Une raison commune derrière la plupart des accidents de la circulation est due au manque de vigilance du conducteur sur la route. Cette thèse se trouve dans le problématique de l'estimation des risques de collision pour un véhicule dans les secondes qui suivent en condition de circulation urbaines. Les systèmes actuellement disponibles dans le commerce sont pour la plupart conçus pour prévenir les collisions avant, arrières, ou latérales. Ces systèmes sont généralement équipés d'un capteur de type radar, à l'arrière, à l'avant ou sur les côtés pour mesurer la vitesse et la distance aux obstacles. Les algorithmes pour déterminer le risque de collision sont fondés sur des variantes du TTC (time-to-collision en anglais). Cependant, un véhicule peut se trouver dans des situations où les routes ne sont pas droites et l'hypothèse que le mouvement est linéaire ne tient pas pour le calcul du TTC. Dans ces situations, le risque est souvent sous-estimé. De plus, les instances où les routes ne sont pas tout droit se trouve assez souvent dans les environnement urbain ; par exemple, les rond point ou les intersections. Un argument de cette thèse est que, savoir simplement qu'il y ait un objet à une certaine position et à une instance spécifique dans le temps ne suffit pas à évaluer sa sécurité dans le futur. Un système capable de comprendre les comportements de déplacement du véhicule est indispensable. En plus, les contraintes environnementales doivent être prises en considération. Le cas le plus simple du mouvement « libre » est d'abord traité. Dans cette situation il n'ya pas de contraintes environnementales ou de comportement explicite. Ensuite, les contraintes environnementales des routes sur trafic urbain et le comportement des conducteurs des véhicules sont introduits et pris en compte explicitement. Cette thèse propose un modèle probabiliste pour les trajectoires des véhicules fondé sur le processus gaussien (GP). Son avantage est le pouvoir d'exprimer le mouvement dans le futur indépendamment de la discrétisation d'espace et d'état. Les comportements des conducteurs sont modélisés avec une variante du modèle de Markov caché. La combinaison de ces deux modèles donne un modèle probabiliste de l'évolution complète du véhicule dans le temps. En plus, une méthode générale pour l'évaluation probabiliste des risques de collision est présentée, où différentes valeurs de risque, chacun avec sa propre sémantique.

Vikram Sarabhai Space Centre,Trivandrum / In the space surrounding the earth there are two major regions where orbital debris causes concern. They are the Low Earth Orbits (LEO) up to about 2000 km, and Geosynchronous Orbits (GEO) at an altitude of around 36000 km. The impact of the debris accumulations are in principle the same in the two regions; nevertheless they require different approaches and solutions, due to the fact that the perturbations in the orbital decay due to atmospheric drag effects predominates in LEO, gravitational forces including earth’s oblateness and luni solar effects dominating in GEO are different in these two regions. In LEO it is generally known that the debris population dominates even the natural meteoroid population for object sizes 1 mm and larger. This thesis focuses the study mainly in the LEO region. Since the first satellite breakup in 1961 up to 01 January 2003 more than 180 spacecraft and rocket bodies have been known to fragment in orbit. The resulting debris fragments constitute nearly 40% of the 9000 or more of the presently tracked and catalogued objects by USSPACECOM. The catalogued fragment count does not include the much more numerous fragments, which are too small to be detected from ground. Hence in order to describe the trackable orbital debris environment, it is important to develop mathematical models to simulate the trackable fragments and later expand it to untrackable objects. Apart from the need to better characterize the orbital debris environment down to sub millimeter particles, there is also a pressing necessity of simulation tools able to model in a realistic way the long term evolution of space debris, to highlight areas, which require further investigations, and to study the actual mitigation effects of space policy measures. The present thesis has provided newer perspectives for five major issues in space debris modeling studies. The issues are (i) breakup modeling, (ii) environment modeling, (iii) evolution of the debris environment, (iv) collision probability analysis and (v) reentry prediction. The Chapter 1 briefly describes an overview of space debris environment and the issues associated with the growing space debris populations. A literature survey of important earlier work carried out regarding the above mentioned five issues are provided in the Chapter 2. The new contributions of the thesis commence from Chapter 3. The Chapter 3 proposes a new breakup model to simulate the creation of debris objects by explosion in LEO named “A Semi Stochastic Environment Modeling for Breakup in LEO” (ASSEMBLE). This model is based on a study of the characteristics of the fragments from on orbit breakups as provided in the TLE sets for the INDIAN PSLV-TES mission spent upper stage breakup. It turned out that based on the physical mechanisms in the breakup process the apogee, perigee heights (limited by the breakup altitude) closely fit suitable Laplace distributions and the eccentricity follows a lognormal distribution. The location parameters of these depend on the orbit of the parent body at the time of breakup and their scale parameters on the intensity of explosion. The distribution of the ballistic coefficient in the catalogue was also found to follow a lognormal distribution. These observations were used to arrive at the proper physical, aerodynamic, and orbital characteristics of the fragments. Subsequently it has been applied as an inverse problem to simulate and further validate it based on some more typical well known historical on orbit fragmentation events. All the simulated results compare quite well with the observations both at the time of breakup and at a later epoch. This model is called semi stochastic in nature since the size and mass characteristics have to be obtained from empirical relations and is capable of simulating the complete scenario of the breakup. A new stochastic environment model of the debris scenario in LEO that is simple and impressionistic in nature named SIMPLE is proposed in Chapter 4. Firstly among the orbital debris, the distribution of the orbital elements namely altitude, perigee height, eccentricity and the ballistic coefficient values for TLE sets of data in each of the years were analyzed to arrive at their characteristic probability distributions. It is observed that the altitude distribution for the number of fragments exhibits peaks and it turned out that such a feature can be best modeled with a tertiary mixture of Laplace distributions with eight parameters. It was noticed that no statistically significant variations could be observed for the parameters across the years. Hence it is concluded that the probability density function of the altitude distribution of the debris objects has some kind of equilibrium and it follows a three component mixture of Laplace distributions. For the eccentricity ‘e’ and the ballistic parameter ‘B’ values the present analysis showed that they could be acceptably quite well fitted by Lognormal distributions with two parameters. In the case of eccentricity also the describing parameter values do not vary much across the years. But for the parameters of the B distribution there is some trend across the years which perhaps may be attributed to causes such as decay effect, miniaturization of space systems and even the uncertainty in the measurement data of B. However in the absence of definitive cause that can be attributed for the variation across the years, it turns out to be best to have the most recent value as the model value. Lastly the same kind of analysis has also been carried out with respect to the various inclination bands. Here the orbital parameters are analyzed with respect to the inclination bands as is done in ORDEM (Kessler et al 1997, Liou et al 2001) for near circular orbits in LEO. The five inclination bands considered here are 0-36 deg (in ORDEM they consider 19-36 deg, and did not consider 0-19 deg), 36-61 deg, 61-73 deg, 73-91 deg and 91- 180 deg, and corresponding to each band, the altitude, eccentricity and B values were modeled. It is found that the third band shows the models with single Laplace distribution for altitude and Lognormal for eccentricity and B fit quite well. The altitude of other bands is modeled using tertiary mixture of Laplace distributions, with the ‘e’ and ‘B’ following once again a Lognormal distribution. The number of parameter values in SIMPLE is, in general, just 8 for each description of altitude or perigee distributions whereas in ORDEM96 it is more. The present SIMPLE model captures closely all the peak densities without losing the accuracy at other altitudes. The Chapter 5 treats the evolution of the debris objects generated by on orbit breakup. A novel innovative approach based on the propagation of an equivalent fragment in a three dimensional bin of semi major axis, eccentricity, and the ballistic coefficient (a, e, B) together with a constant gain Kalman filter technique is described in this chapter. This new approach propagates the number density in a bin of ‘a’ and ‘e’ rapidly and accurately without propagating each and every of the space debris objects in the above bin. It is able to assimilate the information from other breakups as well with the passage of time. Further this approach expands the scenario to provide suitable equivalent ballistic coefficient values for the conglomeration of the fragments in the various bins. The heart of the technique is to use a constant Kalman gain filter, which is optimal to track the dynamically evolving fragment scenario and further expand the scenario to provide time varying equivalent ballistic coefficients for the various bins. In the next chapter 6 a new approach for the collision probability assessment utilizing the closed form solution of Wiesel (1989) by the way of a three dimensional look up table, which takes only air drag effect and an exponential model of the atmosphere, is presented. This approach can serve as a reference collision probability assessment tool for LEO debris cloud environment. This approach takes into account the dynamical behavior of the debris objects propagation and the model utilizes a simple propagation for quick assessment of collision probability. This chapter also brings out a comparison of presently available collision probability assessment algorithms based on their complexities, application areas and sample space on which they operate. Further the quantitative assessment of the collision probability estimates between different presently available methods is carried out and the obtained collision probabilities are match qualitatively. The Chapter 7 utilizes once again the efficient and robust constant Kalman gain filter approach that is able to handle the many uncertain, variable, and complex features existing in the scenario to predict the reentry time of the risk objects. The constant gain obtained by using only a simple orbit propagator by considering drag alone is capable of handling the other modeling errors in a real life situation. A detailed validation of the approach was carried out based on a few recently reentered objects and comparison of the results with the predictions of other agencies during IADC reentry campaigns are also presented. The final Chapter 8 provides the conclusions based on the present work carried together with suggestions for future efforts needed in the study of space debris. Also the application of the techniques evolved in the present work to other areas such as atmospheric data assimilation and forecasting have also been suggested.

We develop a detailed, large-scale, airspace planning and collaborative decision-making model (APCDM), that is part of an $11.5B, 10-year, Federal Aviation Administration (FAA)-sponsored effort to increase U.S. National Airspace (NAS) capacity by 30 percent. Given a set of flights that must be scheduled during some planning horizon, we use a mixed-integer programming formulation to select a set of flight plans from among alternatives subject to flight safety, air traffic control workload, and airline equity constraints. Novel contributions of this research include three-dimensional probabilistic conflict analyses, the derivation of valid inequalities to tighten the conflict safety representation constraints, the development of workload metrics based on average (and its variance from) peak load measures, and the consideration of equity among airline carriers in absorbing the costs related to re-routing, delays, and cancellations. We also propose an improved set of flight plan cost factors for representing system costs and investigating fairness issues by addressing flight dependencies occurring in hubbed operations, as well as market factors such as schedule convenience, reliability, and the timeliness of connections. The APCDM model has potential use for both tactical and strategic applications, such as air traffic control in response to severe weather phenomenon or spacecraft launches, FAA policy evaluation, Homeland Defense contingency planning, and military air campaign planning. The model is tested to consider various airspace restriction scenarios imposed by dynamic severe weather systems and space launch Special Use Airspace (SUA) impositions. The results from this model can also serve to augment the FAA's National Playbook of standardized flight profiles in different disruption-prone regions of the National Airspace. / Ph. D.

The increasing demand to integrate unmanned aircraft systems (UAS) into the national airspace is motivated by the rapid growth of the UAS industry, especially small UAS weighing less than 55 pounds. Their use however has been limited by the Federal Aviation Administration regulations due to collision risk they pose, safety and regulatory concerns. Therefore, before civil aviation authorities can approve routine UAS flight operations, UAS must be equipped with sense-and-avoid technology comparable to the see-and-avoid requirements for manned aircraft. The sense-and-avoid problem includes several important aspects including regulatory and system-level requirements, design specifications and performance standards, intruder detecting and tracking, collision risk assessment, and finally path planning and collision avoidance. In this dissertation, our primary focus is on developing an collision detection, risk assessment and avoidance framework that is computationally affordable and suitable to run on-board small UAS. To begin with, we address the minimum sensing range for the sense-and-avoid (SAA) system. We present an approximate close form analytical solution to compute the minimum sensing range to safely avoid an imminent collision. The approach is then demonstrated using a radar sensor prototype that achieves the required minimum sensing range. In the area of collision risk assessment and collision prediction, we present two approaches to estimate the collision risk of an encounter scenario. The first is a deterministic approach similar to those been developed for Traffic Alert and Collision Avoidance (TCAS) in manned aviation. We extend the approach to account for uncertainties of state estimates by deriving an analytic expression to propagate the error variance using Taylor series approximation. To address unanticipated intruders maneuvers, we propose an innovative probabilistic approach to quantify likely intruder trajectories and estimate the probability of collision risk using the uncorrelated encounter model (UEM) developed by MIT Lincoln Laboratory. We evaluate the proposed approach using Monte Carlo simulations and compare the performance with linearly extrapolated collision detection logic. For the path planning and collision avoidance part, we present multiple reactive path planning algorithms. We first propose a collision avoidance algorithm based on a simulated chain that responds to a virtual force field produced by encountering intruders. The key feature of the proposed approach is to model the future motion of both the intruder and the ownship using a chain of waypoints that are equally spaced in time. This timing information is used to continuously re-plan paths that minimize the probability of collision. Second, we present an innovative collision avoidance logic using an ownship centered coordinate system. The technique builds a graph in the local-level frame and uses the Dijkstra's algorithm to find the least cost path. An advantage of this approach is that collision avoidance is inherently a local phenomenon and can be more naturally represented in the local coordinates than the global coordinates. Finally, we propose a two step path planner for ground-based SAA systems. In the first step, an initial suboptimal path is generated using A* search. In the second step, using the A* solution as an initial condition, a chain of unit masses connected by springs and dampers evolves in a simulated force field. The chain is described by a set of ordinary differential equations that is driven by virtual forces to find the steady-state equilibrium. The simulation results show that the proposed approach produces collision-free plans while minimizing the path length. To move towards a deployable system, we apply collision detection and avoidance techniques to a variety of simulation and sensor modalities including camera, radar and ADS-B along with suitable tracking schemes.

There has been almost fifteen years of political controversy surrounding changes to the rules and procedures by which aircraft conduct their flight within regional Australia. Decisions based on a predominately heuristic (rule of thumb) approach to design have had many adverse consequences for the integrity of the proximity warning function. A sound mathematical model is required to establish this function on a mature engineering foundation. To achieve this, the proximity warning function has been investigated as a hybrid-system. This approach recognises the dual nature of the design: that aircraft dynamics give rise to continuous mathematical models while the communication protocols controlling proximity require discrete mathematical approaches. The blending of each aspect has yielded a deeper insight into the operational limitations and failure modes of this function. The presentation of the thesis follows a design thread through the function. It begins with a description of existing standards and implementations. Risk models are then developed. The pilot interface is recognised as a primary design constraint. Mathematical models are then developed to describe the topology of flow, proximity dynamics, and the scheduling constraints associated with visual, voice, and data-link communications required by the proximity warning function. These analyses show that many aspects of design can be bounded by analytical formulae that bring new robustness to the design and resolve some of the misconceptions arising from the often inaccurate perceptions of present airspace operations. Failure modes, unaccounted for in existing designs are found to actually aggravate failure in the very situations in which the airspace design should be robust and should act to prevent collisions. In particular, there are divergences of performance between the demands required by the system design and the ability of the pilot to deliver such performances. In some cases, these failures may be traced to policy decisions such as service between Instrument Flight Rule and Visual Flight Rule category aircraft. On the basis of the conclusions of this research, a formal engineering review of the proximity warning function is required to assure the containment of the likelihood of mid-air collision for all future operations.