O transporte aéreo e a indústria de sistemas de defesa foram setores pioneiros na utilização de sistemas computacionais críticos, incrementando os níveis de automação nas atividades de controle do espaço aéreo. Com o crescimento desses setores, verificado pela expansão dos números de vôos, volumes de cargas e usuários, assim como pela ampliação e diversidade das operações militares, os sistemas de controle têm assumido maior complexidade técnica, introduzindo novos recursos de automação ou facilidades adicionais de apoio para funções exercidas manualmente. Essa situação tem ampliado a dependência dos serviços prestados, relativamente à disponibilidade dos sistemas computacionais. Diretrizes de projeto e procedimentos operacionais são estabelecidos para manter os níveis de segurança nos casos de falha, no entanto a disponibilidade torna-se parâmetro crítico, na medida em que algumas falhas podem afetar a eficiência nominal da prestação dos serviços. Nesse cenário, este trabalho propõe um modelo para avaliação da disponibilidade de sistemas de controle do espaço aéreo, a partir de recursos de análises da teoria de filas. Inicialmente é citado um modelo geral para análise de disponibilidade de data centers. Em seguida, é apresentada uma extensão do modelo geral para análise da disponibilidade em sistemas de controle do espaço aéreo. Para isso, considerou-se a intervenção humana existente nessa atividade, cujas decisões de controle são exercidas por operadores qualificados (controladores), tanto nas atividades inerentes ao serviço de controle, quanto nos casos de degradação, nos quais os operadores ou técnicos de manutenção assumem alguma tarefa de reparo, decorrente da eventual indisponibilidade de funções do sistema. / Due to the growth in airspace utilization, which can be verified both in terms of the expansions in aerial movements, airports and volumes of transported passengers and cargo, as well as in terms of the expansion of military operations demands and diversity, airspace control activities have been increasing their technical complexity, introducing new features into the existent automation systems or creating additional resources for the automation of some functions previously performed by human operators. This situation has increased the dependence on the availability of the computer systems involved in the services provided by control centers. Project directives and operational procedures are established in order to maintain the safety integrity levels of the systems, in case any failure occurs. However, the availability becomes a critical parameter, once failure events can force an undesirable state of degraded operation, jeopardizing the nominal capacity of the services being performed through any controlled airspace. In this scenario, this work presents an availability model for the computer systems used in airspace control centers, based on analysis from queuing theory. A general model is first presented, referencing a case study that describes the use of queuing models to access the availability of generic data centers. Further considerations are introduced to extend this general model in order to propose its application for the specific computer systems used in airspace control centers, where operational control relies on human activities. In this case, system operation involves intensive use of human-machine interfaces (HMI), for the regular control services provided, and additional technical or operational maintenance activities, occasionally imposed to repair a momentary loss of any function of the system.

Markov processes have been widely studied and used for modeling problems. A Markov process has two main components (i.e., an evolution law and an initial distribution). Markov processes are not suitable for modeling some problems, for example, the problem of predicting a trajectory with a known destination. Such a problem has three main components: an origin, an evolution law, and a destination. The conditionally Markov (CM) process is a powerful mathematical tool for generalizing the Markov process. One class of CM processes, called $CM_L$, fits the above components of trajectories with a destination. The CM process combines the Markov property and conditioning. The CM process has various classes that are more general and powerful than the Markov process, are useful for modeling various problems, and possess many Markov-like attractive properties. Reciprocal processes were introduced in connection to a problem in quantum mechanics and have been studied for years. But the existing viewpoint for studying reciprocal processes is not revealing and may lead to complicated results which are not necessarily easy to apply. We define and study various classes of Gaussian CM sequences, obtain their models and characterizations, study their relationships, demonstrate their applications, and provide general guidelines for applying Gaussian CM sequences. We develop various results about Gaussian CM sequences to provide a foundation and tools for general application of Gaussian CM sequences including trajectory modeling and prediction. We initiate the CM viewpoint to study reciprocal processes, demonstrate its significance, obtain simple and easy to apply results for Gaussian reciprocal sequences, and recommend studying reciprocal processes from the CM viewpoint. For example, we present a relationship between CM and reciprocal processes that provides a foundation for studying reciprocal processes from the CM viewpoint. Then, we obtain a model for nonsingular Gaussian reciprocal sequences with white dynamic noise, which is easy to apply. Also, this model is extended to the case of singular sequences and its application is demonstrated. A model for singular sequences has not been possible for years based on the existing viewpoint for studying reciprocal processes. This demonstrates the significance of studying reciprocal processes from the CM viewpoint.

<p>When traffic in large cities increases, it becomes more vulnerable to disturbances such as accidents, stalled vehicles or construction; therefore, traffic jams are more likely to occur. For better control of the traffic at a disturbance the Swedish National Road Administration (SNRA) has traffic equipment which can be controlled from a command centre. This traffic equipment consists of gates and signs with variable messages. This report will discuss the system used for traffic control in Stockholm. It will present proposals designed to improve it. </p><p>These proposals were prepared based on interviews with people from SNRA and their contractors as well as on comparisons with existing systems. </p><p>The focus of this report is the handling of system alarms and graphical user interface. By implementing the proposals in this report, the following will be achieved:</p><p>· More efficient alarmcontrol - the errors are discovered immediately or soon after they occur </p><p>· Clearer information regarding alarms - the traffic operator receives better information about the error </p><p>· Better control of the traffic equipment - the control will be easier and more flexible.</p>

This dissertation presents a suite of design tools for multi-agent systems that address three main areas: network design, decentralized controller generation, and the synthesis of decentralized control strategies by combining individual decentralized controllers. First, a new metric for quantifying heterogeneity in multi-agent systems is presented based on combining different notions of entropy, and is shown to overcome the drawbacks associated with existing diversity metrics in various scientific fields. Moreover, a new method of controlling multi-agent networks through the single-leader network paradigm is presented where by directly exploiting the homogeneity of agent capabilities, a network which is not completely controllable can be driven closer to a desired target configuration than by using traditional control techniques. An algorithm is presented for generating decentralized control laws that allow for agents to best satisfy a desired global objective, while taking into account network topological constraints and limitations on how agents can compute their control signals. Then, a scripting tool is developed to aid in specifying sequences of decentralized controllers to be executed consecutively, while helping ensure that the required network topological requirements needed for each controller to execute properly are maintained throughout mode switches. Finally, the underlying concepts behind the developed tools are showcased in three example applications: distributed merging and spacing for heterogeneous aircraft during terminal approaches, collaborative multi-UAV convoy protection in dynamic environments, and an educational tool used to teach a graduate-level networked controls course at the Georgia Institute of Technology.

When traffic in large cities increases, it becomes more vulnerable to disturbances such as accidents, stalled vehicles or construction; therefore, traffic jams are more likely to occur. For better control of the traffic at a disturbance the Swedish National Road Administration (SNRA) has traffic equipment which can be controlled from a command centre. This traffic equipment consists of gates and signs with variable messages. This report will discuss the system used for traffic control in Stockholm. It will present proposals designed to improve it. These proposals were prepared based on interviews with people from SNRA and their contractors as well as on comparisons with existing systems. The focus of this report is the handling of system alarms and graphical user interface. By implementing the proposals in this report, the following will be achieved: · More efficient alarmcontrol - the errors are discovered immediately or soon after they occur · Clearer information regarding alarms - the traffic operator receives better information about the error · Better control of the traffic equipment - the control will be easier and more flexible.

In response to the unparalleled growth of demand for air traffic during the past few decades, the Federal Aviation Administration (FAA) launched the Next Generation Air Transportation (NextGen) program to restructure the National Airspace System (NAS). Among the research is the focus on direct, wind optimal routing using geodesic routes and flight operations that do not depend solely on ground based navigation aids (NAVAID) and a fixed airspace structure. While technologies, such as the Global Positioning System (GPS), exist to locate an aircraft at higher degrees of resolution with a larger coverage, the way in which this information is conveyed is long and cumbersome. Therefore, new ways to describe the airspace is desired. The thesis presents the results of an experimental investigation into three alternatives to fix/route and GPS methods. The first method is the Navigation Reference System (NRS) using an absolute grid based strategy that has been recently implemented in limited portions of the United States airspace. The second method, the Military Grid Reference System (MGRS), is also a grid based system, and it is used by NATO, but it has not been applied to the air traffic control context. The third alternative is Point Relation Navigation (PRN), which uses a single point of reference within each Air Route Traffic Center (ARTCC) airspace and acts as a hybrid of coordinate and radial fixes. 21 airline dispatchers from a single major U.S air carrier participated in an online assessment of the five methods above through specific tasks. Results indicate that most participants prefer the fix/route system over the others, followed closely by the PRN method. However, there were varying results across all of the methods in terms of speed and accuracy of completing the tasks. This study incites further interest in strategies to describe aircraft routes operating in a more flexible airspace.

The job of an air traffic controller is stressful by nature. Conditions like aircraft congestion in the skies, an outdated air traffic system and understaffing at control centers can add to the daily stresses of controllers and often cause fatigue. These conditions describe the current status of Air Traffic Services (ATS) in the United States. If left unaddressed, they could compromise safety, the primary objective of air traffic control. The purpose of this thesis is to assess the regulatory framework surrounding ATS specifically in the area of Safety Management Systems (SMS) and Human Factors and determine the course of action to be taken to improve safety in air traffic control. / This thesis begins with a description of what air traffic controllers do and the issues that ATS face in the U.S. It then examines the regulatory framework of the International Civil Aviation Organization (ICAO) and the U.S. regarding ATS, specifically SMS and Human Factors. A comparison is made between the privatized air traffic system of Canada and the government owned air traffic system of the U.S. and how privatization makes a difference economically, politically and legally when implementing standards and regulations and enforcing them. Finally, suggestions are made in order to improve the legal framework of air traffic services in the U.S.

Today, many small aerodromes have a hard time surviving economically, and amongst the largest cost is air traffic control. Airlines are cutting costs where they can, and many times this affects the aerodromes as well, e.g. when airlines decide to park remotely instead of at the gate. The project called Remotely Operated Towers, initiated by SESAR and run by Saab and LFV, is aiming to address this problem. The project revolves around remotely providing ATS to aerodromes where it is deemed suitable. A big challenge in this project is how to assign aerodromes to remote tower modules in the remote control centre. There are many ways to do this, but there is only a few ways to do it to achieve the least amount of modules. This thesis aims to find an optimal solution to the challenge mentioned above. The thesis resulted in a model where the user can provide the input of choice, i.e. aerodromes with associated ATS operating hours and movements, for a specific period – and receive the assignment schedule for the modules, saying exactly which aerodrome are to be controlled by which module at what time.

Train traffic control is a complex task in a dynamic environment. Different actors have to cooperate to meet strong requirements regarding safety, punctuality, capacity utilization, energy consumption, and more. The GMOC model has been developed and utilized in a number of studies in several different areas. This thesis describes GMOC and uses train traffic control as the application area for evaluating its utility. The GMOC model has its origin in control theory and relates to concepts of dynamic decision making. Human operators in complex, dynamic control environments must have clear goals, reflecting states to reach or to keep a system in. Mental models contain the operator’s knowledge about the task, the process, and the control environment. Systems have to provide observability, means for the operator to observe the system’s states and dynamics, and controllability, allowing the operators to influence the system’s states. GMOC allows us to constructively describe complex environments, focusing on all relevant parts. It can be utilized in user-centred system design to analyse existing systems, and design and evaluate future control systems. Our application of GMOC shows that automation providing clear observability and sufficient controllability is seen as transparent and most helpful. GMOC also helps us to argue for visualization that rather displays the whole complexity of a process than tries to hide it. Our studies in train traffic control show that GMOC is useful to analyse complex work situations. We identified the need to introduce a new control strategy improving the traffic plan by supporting planning ahead. Using GMOC, we designed STEG, an interface implementing this strategy. Improvements that have been done to observability helped the operators to develop more adequate mental models, reducing use of cognitive capacity but increasing precision of the operative traffic plans. In order to improve the traffic controllers’ controllability, one needs to introduce and share a real-time traffic plan, and provide the train drivers with up-to-date information on the surrounding traffic. Our studies indicate that driver advisory systems, including such information, reduce the need for traffic re-planning, improve energy consumption, and increase quality and capacity of train traffic. / KAJT / FTTS

At the international level, standards and recommended practices adopted by the ICAO have settled the general framework followed by States in the provision of ATC services. However, as those international instruments have no binding effect, liability of air traffic controllers is governed by national regulations. Therefore, if in both the United States and France the liability regime is based on fault, nevertheless the nature of the fault and the one of the duties of air traffic controllers, as determined by the courts of each States, differ. This lack of uniformity is also obvious regarding the comparison between controllers' and pilots' liabilities. To mitigate the consequences of the deficiency of harmonisation, taking into account technical improvements inherent to the field of ATC and, broadly, to air navigation, two solutions have been suggested. The first one, Free flight, is still under study whereby the second one, privatisation, has already been successfully implemented in several countries and, while being strongly considered by the French government, has by now been initiated by the American one. However, we will have no option but to ascertain that such solutions will not solve the problem pertaining to disparities of regulations and holding of the courts on the matter of air traffic controllers' liability.