1,401 research outputs found

    Mathematical modeling and vertical flight control of a tilt-wing UAV

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    This paper presents a mathematical model and vertical flight control algorithms for a new tilt-wing unmanned aerial vehicle (UAV). The vehicle is capable of vertical take-off and landing (VTOL). Due to its tilt-wing structure, it can also fly horizontally. The mathematical model of the vehicle is obtained using Newton-Euler formulation. A gravity compensated PID controller is designed for altitude control, and three PID controllers are designed for attitude stabilization of the vehicle. Performances of these controllers are found to be quite satisfactory as demonstrated by indoor and outdoor flight experiments

    Pitch Dynamics of Unmanned Aerial Vehicles

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    Dynamic stability requirements for manned aircraft have been in place for many years. However, we cannot expect stability constraints for UAVs to match those for manned aircraft; and dynamic stability requirements specific to UAVs have not been developed. The boundaries of controllability for both remotely-piloted and auto-piloted aircraft must be established before UAV technology can reach its full potential. The development of dynamic stability requirements specific to UAVs could improve flying qualities and facilitate more efficient UAV designs to meet specific mission requirements. As a first step to developing UAV stability requirements in general, test techniques must be established that will allow the stability characteristics of current UAVs to be quantified. This paper consolidates analytical details associated with procedures that could be used to experimentally determine the pitch stability boundaries for good UAV flying qualities. The procedures require determining only the maneuver margin and pitch radius of gyration and are simple enough to be used in an educational setting where resources are limited. The premise is that these procedures could be applied to UAVs now in use, in order to characterize the longitudinal flying qualities of current aircraft. This is but a stepping stone to the evaluation of candidate metrics for establishing flying-quality constraints for unmanned aircraft

    Adaptive Airborne Separation to Enable UAM Autonomy in Mixed Airspace

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    The excitement and promise generated by Urban Air Mobility (UAM) concepts have inspired both new entrants and large aerospace companies throughout the world to invest hundreds of millions in research and development of air vehicles, both piloted and unpiloted, to fulfill these dreams. The management and separation of all these new aircraft have received much less attention, however, and even though NASAs lead is advancing some promising concepts for Unmanned Aircraft Systems (UAS) Traffic Management (UTM), most operations today are limited to line of sight with the vehicle, airspace reservation and geofencing of individual flights. Various schemes have been proposed to control this new traffic, some modeled after conventional air traffic control and some proposing fully automatic management, either from a ground-based entity or carried out on board among the vehicles themselves. Previous work has examined vehicle-based traffic management in the very low altitude airspace within a metroplex called UTM airspace in which piloted traffic is rare. A management scheme was proposed in that work that takes advantage of the homogeneous nature of the traffic operating in UTM airspace. This paper expands that concept to include a traffic management plan usable at all altitudes desired for electric Vertical Takeoff and Landing urban and short-distance, inter-city transportation. The interactions with piloted aircraft operating under both visual and instrument flight rules are analyzed, and the role of Air Traffic Control services in the postulated mixed traffic environment is covered. Separation values that adapt to each type of traffic encounter are proposed, and the relationship between required airborne surveillance range and closure speed is given. Finally, realistic scenarios are presented illustrating how this concept can reliably handle the density and traffic mix that fully implemented and successful UAM operations would entail

    IMPROVING THE ENDURANCE OF SMALL UNMANNED AERIAL VEHICLES UTILIZING FLEXIBLE SOLAR CELLS

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    Though studies and experimentation have been done regarding solar UAVs, it appears that these studies have been primarily focused on the development of futuristic prototypes or proof-of-concept vehicles used under very controlled conditions and without regard to extensive practical applications. On the other hand, in this research we seek to examine the flying endurance benefits that may be achieved by equipping the Nimbus Pro VTOL small unmanned aerial aircraft with commercially available thin film photovoltaic cells. Typical miniature and micro UAVs that run on battery power have an endurance of thirty minutes to two hours, after which time they need to be retrieved so that the batteries can be recharged, or so that another single-use battery can be installed. The retrieve-prepare-relaunch cycle can be greater than the on-station time for the UAV, and greatly reduces the utility of these systems to the intelligence gatherer or war fighter. The focus of this research is to determine the estimation of the power consumption of the Nimbus Pro VTOL and the power generated from an array of solar cells installed on the wing of the aircraft. With that information, we can approximate the additional flight time gained by the installation of the solar array.LTJG, Peruvian NavyApproved for public release. Distribution is unlimited

    Deep Reinforcement Learning Attitude Control of Fixed-Wing UAVs Using Proximal Policy Optimization

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    Contemporary autopilot systems for unmanned aerial vehicles (UAVs) are far more limited in their flight envelope as compared to experienced human pilots, thereby restricting the conditions UAVs can operate in and the types of missions they can accomplish autonomously. This paper proposes a deep reinforcement learning (DRL) controller to handle the nonlinear attitude control problem, enabling extended flight envelopes for fixed-wing UAVs. A proof-of-concept controller using the proximal policy optimization (PPO) algorithm is developed, and is shown to be capable of stabilizing a fixed-wing UAV from a large set of initial conditions to reference roll, pitch and airspeed values. The training process is outlined and key factors for its progression rate are considered, with the most important factor found to be limiting the number of variables in the observation vector, and including values for several previous time steps for these variables. The trained reinforcement learning (RL) controller is compared to a proportional-integral-derivative (PID) controller, and is found to converge in more cases than the PID controller, with comparable performance. Furthermore, the RL controller is shown to generalize well to unseen disturbances in the form of wind and turbulence, even in severe disturbance conditions.Comment: 11 pages, 3 figures, 2019 International Conference on Unmanned Aircraft Systems (ICUAS

    Gateway Positioning in Flying Networks

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    Nos últimos anos, o uso de Veículos Aéreos Não Tripulados (UAVs) para uma infinidade de aplicações, tanto civis como militares, tem aumentado. Como eles apresentam capacidade de operarem praticamente qualquer lugar, a capacidade de pairar sobre o solo e sua crescente capacidade de transportar carga tornaram-os plataformas perfeitas para o transporte de nós de comunicação abordo. Existe um interesse crescente em UAVs no contexto de Redes Voadoras (FNs), tanto para estabelecer novas redes de comunicações ou reforçar conexões existentes, quanto para permitir o acesso de banda larga à internet em Eventos Temporários Lotados (TCEs). No entanto, a alta mobilidade inerente aos UAVs leva a frequentes alterações na topologia da rede, o que, por sua vez, pode causar quebra das ligações entre os UAVs, aumentando a dificuldade em garantir a Qualidade de Serviço (QoS) esperada pelos utilizadores da rede.Um problema que surge com a implementação de FNs é a quantidade total de tempo que os UAVs podem permanecer operacionais, pois os UAVs possuem baterias com capacidade limitada,cuja energia pode ser consumida rapidamente, pois é necessária para comunicações e movimento.Para ligar a FN à Internet, é necessário uma Gateway (GW), que pode ser implementada numUAV. Assim, é importante garantir o posicionamento óptimo do GW UAV para obter o desempenho máximo da rede. Na literatura, algumas soluções foram propostas para o posicionamento dos UAVs que atuam como Pontos de Acesso (APs); no entanto, o problema do posicionamento do GW UAV ainda não foi estudada com profundidade. Como o desempenho global da rede pode ser aprimorado se o GW UAV puder permanecer operacional pelo máximo tempo possível, o desenvolvimento de uma solução de posicionamento do GW UAV, por forma a garantir o desempenho máximo da rede e sensível à eficiência energética constitui o foco desta dissertação. Esta dissertação terá como foco o problema de um posicionamento eficiente do GW UAV do ponto de vista energético, mas, mantendo a cobertura aos restantes nós da rede. De forma a abordar este problema, será desenvolvido um algoritmo para o posicionamento não estacionário do GW UAV.Over the past few years the usage of Unmanned Aerial Vehicles (UAVs) for a myriad of applications, both civil and military, has increased. As they present capability to operate in virtually anywhere, the ability to hover over the ground, and their increasing capacity to carry cargo, has made them perfect platforms for the transport of on board communications nodes.There has been an increasing interest in UAVs in the context of Flying Networks (FNs), either to establish communication networks or reinforce telecommunications infrastructures and enable the broadband access to the Internet in Temporary Crowded Events (TCEs). However, the high mobility inherent to UAVs leads to frequent changes in the network topology, which in turn may cause connection disruptions between the UAVs, increasing the difficulty of meeting the Quality of Service (QoS) expected by the network's users.An additional problem that raises with the implementation of FNs is the total amount of time that UAVs can remain operational, as they have batteries with limited capacity, whose energy can be drained quite quickly, as it is required for both communications and movement.To connect the FN to the Internet a Gateway (GW) is required, and it can be implemented in a UAV. Thus, it is important to ensure the optimal placement of the GW UAV in order to achieve maximum network performance. In the literature, some solutions have been proposed for the placement of the UAVs that act as Access Points (APs); however, the issue of the GW UAV placement has not been studied with the desired depth. As the overall network performance can be improved if the GW UAV remains operational for the maximum amount of time, the development of an energy efficiency-aware a placement solution of the GW UAV, in order to maximize the network performance is the scope dissertation.This dissertation will focus on the issue of an energy-efficient placement of the GW UAV while maintaining coverage for the remaining nodes of the network. To tackle this issue an algorithm to the non-stationary placement of the GW UAV will be developed
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