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

[hal-01429728] A Framework for Wind Sensitivity Analysis for Trajectory Tracking

Publications ENAC - Monday, 27 March 2017 - 13:26:58
In this paper a sensitivity analysis of trajectories w.r.t. wind effects is proposed. This analysis will allow to specify wind estimates properties as well as control reactiveness characteristics to ensure accurate guidance in real atmosphere. The mathematic model developed for flight dynamics is intended to take into account wind gust effects on AoA, sideslip angle and airspeed. A two layer Nonlinear Dynamic Inversion (NDI) structure has been considered to control fast and slow dynamics. In order to test the proposed approach, a full six degrees of freedom Matlab model with trained Neural Networks to emulate a Boeing 737-200 was developed.

[hal-01493782] Bayesian sparse estimation of migrating targets in autoregressive noise for wideband radar

Publications ENAC - Thursday, 23 March 2017 - 02:05:13
In recent work we showed the interest of using sparse representation techniques to estimate a target scene observed by wideband radar systems. However the principle was demonstrated in a white noise background only. In this paper, we present an extended version of our sparse estimation technique that attempts to take into account the (possible) presence of diffuse clutter. More specifically, an autoregressive model is considered for the noise vector. Performance of the technique is studied on synthetic and experimental data. Pertinence of the noise model is discussed.

[hal-01490632] Heads or tails in zero gravity: an example of a classical contextual "measurement

Publications ENAC - Thursday, 23 March 2017 - 02:00:55
Playing the game of heads or tails in zero gravity demonstrates that there exists a contextual "measurement" in classical mechanics. When the coin is flipped, its orientation is a continuous variable. However, the "measurement" that occurs when the coin is caught by clapping two hands together gives a discrete value (heads or tails) that depends on the context (orientation of the hands). It is then shown that there is a strong analogy with the spin measurement of the Stern-Gerlach experiment, and in particular with Stern and Gerlach’s sequential measurements. Finally, we clarify the analogy by recalling how the de Broglie-Bohm interpretation simply...

[hal-01492702] Formulation relaxée de la séparation équilibrée d’un graphe

Publications ENAC - Wednesday, 22 March 2017 - 16:18:43
Dans ce travail, nous nous intéressons à la formulation de variantes du problème du séparateur dans un graphe (VSP , pour Vertex Separator Problem), permettant de fournir des méthodes alternatives aux méthodes classiques de clustering

[hal-01491205] A maximum likelihood-based unscented Kalman filter for multipath mitigation in a multi-correlator based GNSS receiver

Publications ENAC - Tuesday, 21 March 2017 - 02:01:09
In complex environments, the presence or absence of multipath signals not only depends on the relative motion between the GNSS receiver and navigation satellites, but also on the environment where the receiver is located. Thus it is difficult to use a specific propagation model to accurately capture the dynamics of multipath signal parameters when the GNSS receiver is moving in urban canyons or other severe obstructions. This paper introduces a statistical model for the line-of-sight and multipath signals received by a GNSS receiver. A multi-correlator based GNSS receiver is also exploited with the advantage to fully characterizing the impact of multipath signals on the...

[hal-01490737] Introduction to the Issue on Stochastic Simulation and Optimization in Signal Processing

Publications ENAC - Saturday, 18 March 2017 - 02:09:22
The papers in this special issue seek to report cutting edge research on stochastic simulation and optimisation methodologies, and their application to challenging SP problems that are not well addressed by existing methodologies.

[hal-01486832] Convolutional Trees for Fast Transform Learning

Publications ENAC - Tuesday, 14 March 2017 - 02:09:42
—Dictionary learning is a powerful approach for sparse representation. However, the numerical complexity of classical dictionary learning methods restricts their use to atoms with small supports such as patches. In a previous work, we introduced a model based on a composition of convolutions with sparse kernels to build large dictionary atoms with a low computational cost. The subject of this work is to consider this model at the next level, i.e., to build a full dictionary of atoms from convolutions of sparse kernels. Moreover, we further reduce the size of the representation space by organizing the convolution kernels used to build atoms into a tree structure. The...

[hal-01486838] Learning a fast transform with a dictionary

Publications ENAC - Tuesday, 14 March 2017 - 02:09:42
— A powerful approach to sparse representation, dictionary learning consists in finding a redundant frame in which the representation of a particular class of images is sparse. In practice, all algorithms performing dictionary learning iteratively estimate the dictionary and a sparse representation of the images using this dictionary. However, the numerical complexity of dictionary learning restricts its use to atoms with a small support. A way to alleviate these issues is introduced in this paper, consisting in dictionary atoms obtained by translating the composition of K convolutions with S-sparse kernels of known support. The dictionary update step associated with...

[hal-01485015] Deep fusion of vector tracking GNSS receivers and a 3D city model for robust positioning in urban canyons with NLOS signals

Publications ENAC - Friday, 10 March 2017 - 02:06:04
In urban canyons, the GNSS satellite signals may travel an additional distance due to reflection and diffraction before reaching the receiver antenna. Where no direct path is available, this is called a non-line of- sight (NLOS) propagation and adds a positive bias to the geometric measured pseudorange. In this paper, we address the issue of GNSS positioning in harsh environments using constructively the NLOS signals. To exploit these biased signals, we compensate for the NLOS bias using a 3D GNSS simulation model of the environment. We use the 3D model as a priori information to characterize the additional NLOS bias. In this work, we propose a deep integration of the 3D...

[hal-01485021] Nonlinear regression using smooth Bayesian estimation

Publications ENAC - Friday, 10 March 2017 - 02:06:04
This paper proposes a new Bayesian strategy for the estimation of smooth parameters from nonlinear models. The observed signal is assumed to be corrupted by an independent and non identically (colored) Gaussian distribution. A prior enforcing a smooth temporal evolution of the model parameters is considered. The joint posterior distribution of the unknown parameter vector is then derived. A Gibbs sampler coupled with a Hamiltonian Monte Carlo algorithm is proposed which allows samples distributed according to the posterior of interest to be generated and to estimate the unknown model parameters/hyperparameters. Simulations conducted with synthetic and real satellite...
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