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Coordinated Sequencing of Traffic on Multiple En-Route Constraint Points.
No full textInternational audienceAir transportation traffic is progressively increasing over the years and dealing with it is an essential task to guarantee fluid flights in the future. Several works already indexed multiple aspects of aviation, among them, the E-MAN system. It introduced the sequencing of arriving traffic, starting from early stages of the En-route phase. This change facilitated the work for the approach controllers but also increased the workload of the En-route controllers. To handle that workload, controllers are now assisted by tools that consider the new constraints introduced by the arrival management system and propose advisories. From that same perspective, our project focuses on an algorithm for a helper tool that will combine both aspects of traffic sequencing in the En-route phase and conflict resolution. With this novel approach, we automatically generate near-to- optimal flight decisions, given that we can modify the speed and the flight level to respect the sequencing constraints and cut down potential conflicts. We categorize the problem as a mathematical optimization case. Thus, we describe a detailed mathematical model which covers all the aspects of the problem. This model gives a basis for the implementation of the flight optimizer. Later, we propose a solution based on a sliding window simulated annealing algorithm which reduces the complexity and takes into account uncertainties. Finally, we successfully test an implementation of the solution with real-life traffic data. It corresponds to flights within France going towards Paris CDG airport over a period of 24 h. The results demonstrate a total conflicts resolution with satisfying compliance with sequencing constraints
3D split-step wavelet method for the propagation over impedance ground condition
No full textInternational audienceThe long-range propagation of electromagnetic waves over the ground is a major topic for many applications in communication, navigation, and surveillance. In this article, we propose a wavelet-based split-step method in 3D to compute the propagation in this context. Also, using the discrete-mixed Fourier transform (DMFT), transverse invariant impedance ground conditions are taken into account, for which the ground wave propagation is accurately computed. Numerical tests show that the method is fast, accurate, and memory efficient. Finally, we show that the widely used DMFT is not valid for transverse variant ground compositions
Probabilistic swarms guidance within the Gama-platform
No full textInternational audienceProviding means to address the controlling of a large-scale swarm as a whole is a challenging problem. In this context, B. Açikmese et al. [1] introduced a probabilistic guidance approach, to guide a large-scale swarm of autonomous agents into a desired formation shape. The mission is accomplished in a decentralized manner. Thus, the swarm asymptotically achieves the desired distribution without any communication between agents. A variety of swarm coordination and control methods appeared in the literature, but there is not a multitude of solutions to visualize and control the swarm in real-time.Therefore we proposed to interface probabilistic swarms guidance into the Gama platform, since it supports great number of agents and offers a flexible interface. For now, we focused on the Markov-chain swarm guidance approach, presented in [1]. The method can be divided in three main steps. First, the desired physical space is divided into m bins (subregions), and the desired probability density is prescribed for each bin in v 2 Rm. Note that the number of bin is directly determined by the spatial resolution of the desired formation shape. In order to restrict allowable agent motion, an adjacency matrix A is build, such that A[i; j] = 1 when the transition from bin i to bin j is authorized, and is zero otherwise. Given adjacency matrix A and desired density v, the Markov matrix M 2 Rm m is constructed. The entries of matrix M are defined as transition probabilities. In practice, an agent in bin j transitions to bin i between two consecutive stages with probability M[i; j].In order to set up the simulation environment in Gama, we have developed a plugin which add the required functionalities to Gama-platform and a gaml model to build the Graphical User Interface (GUI). The GUI allows the user to select the resolution of the grid or volume as a set of bins, then to choose the desired shape. The shape are computed from images which are rasterized to generate the desired distribution. Adjacency matrix is also specified as the distance between bins that can be reached within one transition. Once this step is done, the user can choose the initial number of agents and run the simulation. During the simulation, the user can interact with the swarm (kill or add agents). Most importantly, one can change the target distribution, updating the Markov matrix to all agents, and guiding the transition to the selected shape.Given the encouraging results, future work will focus on implementing: motion characteristics for agents, conflict avoidance techniques [2] and three dimensional simulations
Représentation de programmes SMALA grâce à la théorie des bigraphes
No full textInternational audienceDans le but de certifier le compilateur du langage réactif-interactif SMALA, nous cherchons à représenter sa sémantique en instanciant la théorie des bigraphes. En nous limitant dans un premier temps à un sous-ensemble de ce langage, nous avons pu représenter ses différents acteurs comme des entités distribuées dans l'espace. Des règles de réaction sur les bigraphes permettent de mettre ces entités en mouvement et en relation les unes avec les autres afin de représenter l'exécution du programme en plus de sa structure
A Phase Correction for Long Distance Propagation Using Split-Step Methods in Non-Rectangular Domains
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Classifying histograms of medical data using information geometry of beta distributions
No full textInternational audienceIn this paper, we use tools of information geometry to compare, average and classify histograms. Beta distributions are fitted to the histograms and the corresponding Fisher information geometry is used for comparison. We show that this geometry is negatively curved, which guarantees uniqueness of the notion of mean, and makes it suitable to classify histograms through the popular K-means algorithm. We illustrate the use of these geometric tools in supervised and unsupervised classification procedures of two medical data-sets, cardiac shape deformations for the detection of pulmonary hypertension and brain cortical thickness for the diagnosis of Alzheimer's disease
Attitude Determination and RTK Positioning Using Multiple Low-Cost Receivers with Known Geometry
No full textInternational audienceIn this article, we have presented a method that includes an array of receivers with known geometry to enable vehicle attitude determination and enhanced RTK performance in different environments. Taking advantage of the attitude information and the known geometry of the array of receivers, we are able to improve some of the steps of precise position computation. We demonstrated through real data processing results that our multi-receiver RTK system is more robust to degraded satellite geometry, in terms of ambiguity fixing rate, and obtains a better position accuracy under the same conditions when compared with the single-receiver system
Bounding Fixed Points of Set-based Bellman Operator and Nash Equilibria of Stochastic Games
No full textInternational audienceMotivated by uncertain parameters encountered in Markov decision processes (MDPs) and stochastic games, we study the effect of parameter uncertainty on Bellman operator-based algorithms under a set-based framework. Specifically, we first consider a family of MDPs where the cost parameters are in a given compact set; we then define a Bellman operator acting on a set of value functions to produce a new set of value functions as the output under all possible variations in the cost parameter. We prove the existence of a fixed point of this set-based Bellman operator by showing that it is contractive on a complete metric space, and explore its relationship with the corresponding family of MDPs and stochastic games. Additionally, we show that given interval set-bounded cost parameters, we can form exact bounds on the set of optimal value functions. Finally, we utilize our results to bound the value function trajectory of a player in a stochastic game
Computing State Invariants Using Point-Wise Integral Quadratic Constraints and the S-procedure
No full textInternational audienceThis paper deals with the problem of computing ellipsoidal state invariant sets for uncertain systems that consist of a nominal part and an uncertainty feedback operator. The set of allowable uncertainty operators is characterized using point-wise integral quadratic constraints (IQCs). The proposed solution methodology combines the S-procedure and the notion of point-wise IQCs in a novel way. The approach allows for a point-wise characterization of the disturbance inputs and involves solvinga grid of convex optimization problems. An illustrative example is provided to show how to apply the proposed results
A Variational Adjoint Approach on Wide-Angle Parabolic Equation for Refractivity Inversion
No full textInternational audienceRadar systems performance under anomalous propagation conditions can be predicted if the atmosphere is properly known. This paper introduces a tomographic approach to estimate refractivity in the troposphere with an adjoint-based inversion method. A new adjoint model is developed for the two-dimensional wide-angle parabolic equation using variational adjoint approach, to invert refractivity from phaseless data measured with an array of radio receivers in open-sea environment. The obtained adjoint model is validated considering propagation through range-independent medium over flat perfectly-electric-conducting surface at horizontal polarization. The ill-posedness of the regarded inverse problem is shown with the optimization landscapes. The parametric study indicates the potential use of this method as a refractivity gradient retrieval system under certain circumstances