Ecole Nationale de l'Aviation Civile
Toutes les publications de l'ENAC en direct.
All ENAC publications.
Over the past few years, the need for positioning, and thus the number of positioning services in general, has been in constant growth. This need for positioning has been increasingly focused on constrained environments, such as urban or indoor environments, where GNSS (Global Navigation Satellite System) is known to have significant limitations: multipath as well as the lack of Line-of-Sight (LOS) satellite visibility degrades the GNSS positioning solution and makes it unsuitable for some urban or indoor applications. In order to improve the GNSS positioning performance in constrained environments, many solutions are already available: hybridization with additional...
In recent years, many aircraft manufacturers have proposed inno-vative cockpit concepts based on touchscreens. Although having alarge number of advantages, this type of solution suffers from severelimitations in operational use, in particular, eyes-free interactionis nearly impossible and touchscreens are extremely complex touse during turbulent conditions. We examined the contribution ofphysicality to overcome these weaknesses by introducing a shape-changing touchscreen that offers folds on which the user hand canrest. This surface has been assessed in simulator during pilotingconditions that varied in terms of turbulences and mental workload.Results showed that the...
Motivated 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...
A Dielectric Resonator Antenna operating in circular polarization is presented. The proposed antenna is formed by a uniaxial anisotropic dielectric and a ground plane. The optimization of the permittivity tensor and antenna dimensions is performed both theoretically and numerically using an Eigen mode analysis in Ansys HFSS. A good agreement is obtained for the resonant frequencies and quality factors of the different modes. The uniaxial anisotropic DRA radiates two degenerate orthogonal modes, TE111 x and TE111 y , with equal amplitudes and 90° phase difference in order to achieve circular polarization. An impedance bandwidth of 9.8% is accomplished and a broadside...
In this paper, an antenna made of two dielectric resonators is proposed to realize a Huygens source in linear polarization. The goal is to design an antenna with a radiationpattern oriented in one half-space without the use of ground plane. The principle relies on the combination of two collocated electric and magnetic dipoles at the center frequency of 2.42 GHz.The optimization of the antenna dimensions is performed with numerical analysis using far-field simulations in ANSYS HFSS. As a result, the antenna achieves a front-to-back ratio of 41 dB
In this article, we test a horizontal detect and avoid algorithm for Unmanned Aerial Vehicules (UAVs) flying in the lower airspace (under FL180). We use recorded commercial traffic trajectories and randomly build 3000 conflicts scenarios with UAVs to check the ability of such an algorithm to ensure the separation with commercial aviation. We consider two different types of UAVs, the first type flying at 80 kn and the second type flying at 160 kn with six different missions: flying straight or turning and leveled, climbing or descending. We only focus on horizontal maneuvers in order not to interfere with aircraft Traffic Collision Avoidance System (TCAS). The article...
Les scientifiques de l’atmosphère cherchent constamment à acquérir de nouvelles données pouvant améliorer leurs modèles des phénomènes atmosphériques, et notamment des nuages. Les méthodes actuelles sont insuffisantes pour collecter des mesures adéquates de la dynamique des nuages et des paramètres microphysiques liés à leur formation générant de grandes incertitudes dans la formulation des modèles. Ce manque de données in-situ pousse les météorologues à trouver de nouvelles méthodes de collecte.L’utilisation des drones est maintenant largement répandue et de nombreuses applications voient le jour dans différents contextes. Bien que l’utilisation d’un drone unique soit...
This paper presents an adapted trust-region method for solving computationally expensive black-box optimization problems with mixed binary variables that involve a cyclic symmetry property. Mixed binary problems occur in several practical optimal design problems, e.g., aircraft engine turbines, mooring lines of offshore wind turbines, electric engine stators and rotors. The motivating application for this study is the optimal design of helicopter bladed disk turbo-machines. The necklace concept is introduced to deal with the cyclic symmetry property, and to avoid costly black-box objective function evaluations at equivalent solutions. An adapted distance is proposed for...