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Toutes les publications de l'ENAC en direct.
All ENAC publications.

[hal-02100897] The Fisher-Rao geometry of beta distributions applied to the study of canonical moments

Publications ENAC - Vendredi, 19 avril 2019 - 03:28:22
This paper studies the Fisher-Rao geometry on the parameter space of beta distributions. We derive the geodesic equations and the sectional curvature, and prove that it is negative. This leads to uniqueness for the Riemannian centroid in that space. We use this Riemannian structure to study canonical moments, an intrinsic representation of the moments of a probability distribution. Drawing on the fact that a uniform distribution in the regular moment space corresponds to a product of beta distributions in the canonical moment space, we propose a mapping from the space of canonical moments to the product beta manifold, allowing us to use the Fisher-Rao geometry of beta...

[hal-01711994] A Proposal for Ensuring the Quality of Aerospace Engineering Higher Education in Europe

Publications ENAC - Jeudi, 18 avril 2019 - 16:37:42
The paper presents a possible roadmap for the definition of a European quality label for aerospace related higher education degrees. The proposal is the result of a two-years long Horizon 2020 project that has involved a great portion of the European stakeholders in aerospace: Universities, research centres, industries (both small and large) networks, associations and accreditation agencies. The core concept established is that it is possible to establish a sector-specific, content based, quality system, that can complement the existing national or European accreditation systems, providing added value to the internal and/or external quality assurance processes that are...

[tel-02089324] Fonctions de navigation stochastiques : application à la planification robuste de trajectoires d'avions

Publications ENAC - Mercredi, 17 avril 2019 - 12:33:16
Contexte: Avec l'augmentation continue du trafic aérien, une refonte des méthodes de planification pour les trajectoires des avions est nécessaire. De nombreuses pistes, telles que les fonctions de navigation, ont été proposées, mais dans le domaine de la gestion du trafic aérien, toute nouvelle méthode doit démontrer sa fiabilité avant de pouvoir être déployée. Objectifs: Implémenter des outils permettant de démontrer la robustesse des trajectoires obtenues avec les fonctions de navigation harmoniques aux aléas liées au vent qui ont pour effet de déplacer longitudinalement les avions. Méthodes: La variation de Hadamard permet de déterminer la variation de la solution d'...

[hal-02090498] The coupling effect of Lipschitz regularization in deep neural networks

Publications ENAC - Mardi, 16 avril 2019 - 17:22:30
We investigate robustness of deep feed-forward neural networks when input data are subject to random uncertainties. More specifically, we consider regularization of the network by its Lipschitz constant and emphasize its role. We highlight the fact that this regularization is not only a way to control the magnitude of the weights but has also a coupling effect on the network weights accross the layers. We claim and show evidence on a dataset that this coupling effect brings a tradeoff between robustness and expressiveness of the network. This suggests that Lipschitz regularization should be carefully implemented so as to maintain coupling accross layers.

[hal-02096509] Multipath Mitigation for GNSS Positioning in an Urban Environment Using Sparse Estimation

Publications ENAC - Mardi, 16 avril 2019 - 03:24:35
Multipath (MP) remains the main source of error when using global navigation satellite systems (GNSS) in a constrained environment, leading to biased measurements and thus to inaccurate estimated positions. This paper formulates the GNSS navigation problem as the resolution of an overdetermined system whose unknowns are the receiver position and speed, clock bias and clock drift, and the potential biases affecting GNSS measurements. We assume that only a part of the satellites are affected by MP, i.e., that the unknown bias vector has several zero components, which allows sparse estimation theory to be exploited. The natural way of enforcing this sparsity is to introduce...

[hal-02082073] Multi-purpose TDM Component for GNSS

Publications ENAC - Lundi, 15 avril 2019 - 16:26:58
This article proposes a Time-Division-Multiplexing (TDM) technique applied at PRN code level as a signal design solution able to cope with the provision of several functionalities in one signal component: the allocation of the signal to the different functionalities is made at PRN code level. The functionalities targeted in this article are low-complexity acquisition, fast Time-ToFirst-Fix Data (TTFFD), Security Code Authentication (SCA) and, additionally, non-coherent signal processing. The interest of using a TDM component signal design lays on the introduction of just one new component to reduce the complexity to be added to the legacy GNSS satellite payload and to...

[hal-01403437] LDPC Channel Code Optimization for a GNSS CSK-Modulated Signal

Publications ENAC - Lundi, 15 avril 2019 - 13:29:36
In order to address the Global Navigation Satellite Systems (GNSS) signal data rate increase challenge, as well as the GNSS signal data availability in urban environments issue, this paper proposes a new designed GNSS signal. Code-Shift Keying (CSK) modulation has been chosen as an alternative to current Binary PhaseShift Keying (BPSK) since it allows increased data rates and non-coherent demodulation. In addition, the new CSK-modulated signal is protected by a Low-Density Parity-Check (LDPC) channel code, as in the latest GNSS designed signal, GPS III L1C. Firstly, an asymptotic analysis is done via EXtrinsic Information Transfer (EXIT) charts in an Additive White...

[hal-01403443] Data Integrity for GPS and Galileo Signals used by Civil Aviation

Publications ENAC - Lundi, 15 avril 2019 - 12:44:59
GNSS signals coupled with control mechanisms at the receiver end must guarantee that the information transmitted through the navigation message is provided unaltered to the final end user. From this premise the concept of Data Integrity is presented in this paper -measure of the trust that can be placed in the invariance of the received message information with respect to the transmitted information- and is quantified through 3 parameters, probability of erroneous message, probability of undetected error and Data Integrity Risk (DIR). The Data Integrity concept is special important in Civil Aviation where the provision of altered Clock offset correction and satellite...
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