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Garcia M.,Center for Advanced Aerospace Technologies | Viguria A.,Center for Advanced Aerospace Technologies | Ollero A.,Center for Advanced Aerospace Technologies | Ollero A.,University of Seville
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2013

This paper discusses several alternatives, based on graph search, to calculate UAV trajectories that avoid regions with dangerous weather effects and with the least deviation from the shortest trajectory. It is also explained how to adapt graph search algorithms to be used for 3D trajectories with UAVs, and which design considerations should be taken into account (for example the discretization of the airspace). Also, an extension of the Lazy Theta * algorithm is presented; a dynamic algorithm that calculates the trajectory while the weather hazards information is updated. The paper includes simulations and experimental results in the CATEC testbed with multiple UAVs. © Springer Science+Business Media Dordrecht 2012. Source

Maza I.,University of Seville | Caballero F.,University of Seville | Capitan J.,University of Seville | Martinez-De-Dios J.R.,University of Seville | And 2 more authors.
Journal of Field Robotics | Year: 2011

This paper presents the architecture developed in the framework of the AWARE project for the autonomous distributed cooperation between unmanned aerial vehicles (UAVs), wireless sensor/actuator networks, and ground camera networks. One of the main goals was the demonstration of useful actuation capabilities involving multiple ground and aerial robots in the context of civil applications. A novel characteristic is the demonstration in field experiments of the transportation and deployment of the same load with single/multiple autonomous aerial vehicles. The architecture is endowed with different modules that solve the usual problems that arise during the execution of multipurpose missions, such as task allocation, conflict resolution, task decomposition, and sensor data fusion. The approach had to satisfy two main requirements: robustness for operation in disaster management scenarios and easy integration of different autonomous vehicles. The former specification led to a distributed design, and the latter was tackled by imposing several requirements on the execution capabilities of the vehicles to be integrated in the platform. The full approach was validated in field experiments with different autonomous helicopters equipped with heterogeneous devices onboard, such as visual/infrared cameras and instruments to transport loads and to deploy sensors. Four different missions are presented in this paper: sensor deployment and fire confirmation with UAVs, surveillance with multiple UAVs, tracking of firemen with ground and aerial sensors/cameras, and load transportation with multiple UAVs. Copyright © 2011 Wiley Periodicals, Inc. Source

Viguria A.,Center for Advanced Aerospace Technologies | Howard A.M.,Georgia Institute of Technology
International Journal of Robotics Research | Year: 2010

In this paper, we present a probabilistic analysis approach for analyzing market-based algorithms applied to the initial formation problem. These algorithms determine an assignment scheme for associating individual robots with goal positions necessary to achieve a desired formation while minimizing an objective function. The main contribution of this paper is a method that calculates the expected value of the objective function, which allows us to estimate and compare theoretically the performance of two task allocation algorithms. This probabilistic analysis is applied in different runtime scenarios. We validate our approach through both simulations and experiments with real robots. © 2010 The Author(s). Source

Sandino L.A.,University of Seville | Bejar M.,Pablo De Olavide University | Ollero A.,University of Seville | Ollero A.,Center for Advanced Aerospace Technologies
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2013

RED-UAS 2011 paper. When designing new control techniques for unmanned helicopters, the development of mathematical models that reproduce the dynamics of the real platform is a matter of importance. This allows the usage of model-based approaches that achieve better adaptation of the control laws to the real system. In these cases, the objective is not to obtain complex equations like those required for high-fidelity simulations. Instead, the aim is to derive simple and manageable models that ease the derivation of the control laws, maintaining at the same time their capability to reproduce the main behavior of the real system. The dynamics of a small-size helicopter with a stiff main rotor are mainly described by its mechanical model. Accordingly, this paper analyzes in detail three representative methods for elaborated modeling of the mechanics of small-size helicopters: Newton-Euler, Lagrange and Kane. For that purpose, the most general case is considered: two rigid bodies, fuselage and main rotor. As a consequence, the resulting models account for most significant modeling issues in the mechanical behavior of a small-size helicopter, such as the gyroscopic effect. Although the equations obtained using the three approaches are equivalent in the sense that they generate the same numerical results in simulation, Kane's method holds some unique advantages. © 2013 Springer Science+Business Media Dordrecht. Source

Sandino L.A.,University of Seville | Bejar M.,Pablo De Olavide University | Kondak K.,German Aerospace Center | Ollero A.,University of Seville | Ollero A.,Center for Advanced Aerospace Technologies
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2013

Helicopters are well-known by their hovering capabilities. However, the performance of this valuable feature can be seriously affected by external disturbances such as wind effects. The latter could be even more significant when dealing with small-size helicopters, which are commonly adopted as base platforms for developing unmanned aerial vehicles. Motivated by this context, this work proposes an augmented configuration for performing more stable hovering maneuvers that consists of the unmanned helicopter itself, a tether connecting the helicopter to the ground, and a device on ground adjusting the tether tension. A modeling analysis on the inherent benefits to the proposed configuration as well as the control guidelines to exploit such potentialities are presented in this paper. As a proof a concept, a first basic implementation of the control structure for the entire system is also included. Finally, several demonstrating simulations under artificially generated wind influences are presented to endorse the validity of the proposed approach. © 2012 Springer Science+Business Media B.V. Source

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