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

[hal-01935746] What is it like for a middle manager to take safety into account? Practices and challenges

Publications ENAC - Friday, 7 December 2018 - 15:17:59
Aviation today is seen as a very safe industry, yet recent accidents have shown that vulnerabilities still exist. The literature has often drawn attention to the role played by top managers/CEO in running their businesses profitably, and at the same time keeping them safe from threats. Research has also investigated the way people at the sharp-end of organisations are ‘mindful’ of the possible threats that can occur in their day-to-day activities, and how they can anticipate (most of) them. But what about the role played by middle managers in ensuring safety in every organisational operation? Even if researchers now agree that middle managers’ actions are a valuable...

[hal-01767939] Individualized Visits to Foster the Engagement and the re-visit in Museums

Publications ENAC - Thursday, 6 December 2018 - 16:41:03
Museums have become places that, besides conserving and storing artefacts, provide visitors with education and amusement. They now have to compete with the entertainment industry to attract visitors and expand their audience. The use of digital technology is emerging as a solution. While many studies focus on the visitor side, we are interested in tools for museum staff. To understand their needs and processes, we adopted a participatory and iterative design process, involving museum professionals as end-users at each step (i.e. user observation, design, prototyping, users tests). We conducted 7 meetings, 4 interviews studies and 2 experimental observations with 12...

[hal-01886335] Vizir: A Domain-Specific Graphical Language for Authoring and Operating Airport Automations

Publications ENAC - Thursday, 6 December 2018 - 16:39:27
Automation is one of the key solutions proposed and adopted by international Air Transport research programs to meet the challenges of increasing air traffic. For automation to be safe and usable, it needs to be suitable to the activity it supports, both when authoring it and when operating it. Here we present Vizir, a Domain-Specific Graphical Language and an Environment for authoring and operating airport automations. We used a participatory-design process with Air Traffic Controllers to gather requirements for Vizir and to design its features. Vizir combines visual interactionoriented programming constructs with activity-related geographic areas and events. Vizir...

[hal-01936955] Precision Landing for Fixed-wing UAV using Ultra-Wide-Band Ranging

Publications ENAC - Wednesday, 5 December 2018 - 16:17:11
Fixed-wing mini UAVs usually require a large area in order to safely land, eventually directly using the fuselage body as a landing skid. In some cases, the ground surface is not suitable for this type of operation and may damage the aircraft. A common option is to use a net to capture the plane, but the GPS accuracy may not be sufficient to allow a reliable landing in full autonomy. In this paper, we are investigating the use of Ultra-Wide-Band communication modules, used as ranging systems, in order to determine the position of the UAV during its final approach. This information is then used to adjust the trajectory towards the landing net. The focus is made to the...

[hal-01936964] Accurate control law for low-cost UAV

Publications ENAC - Wednesday, 5 December 2018 - 16:16:50
Present article proposes a method to design a control law and the associated observer to stabilize a UAV. The design is only based on the UAV geometry, mass and propulsion system characteristics which do not require any expensive facilities or software to be obtained. The control inputs are the longitudinal airspeed, the roll angle and the slope angle to ease the guidance control whether manual or automatic. The resulting control only relies on the information provided by a 6 Degrees of Freedom (DoF) Iner-tial measurement unit (IMU) that makes it suitable for implementation on very basic autopilot board (cf. Paparazzi Chimera, Pixhawk XRacer, ArduPilot APM...). The...

[hal-01936330] Path Word: A Multimodal Password Entry Method for Ad-hoc Authentication Based on Digits' Shape and Smooth Pursuit Eye Movements

Publications ENAC - Wednesday, 5 December 2018 - 16:16:09
We present PathWord (PATH passWORD), a multimodal digit entry method for ad-hoc authentication based on known digits shape and user relative eye movements. PathWord is a touch-free, gaze-based input modality, which attempts to decrease shoulder surfing attacks when unlocking a system using PINs. The system uses a modified web camera to detect the user's eye. This enables suppressing direct touch, making it difficult for passer-bys to be aware of the input digits, thus reducing shoulder surfing and smudge attacks. In addition to showing high accuracy rates (Study 1: 87.1% successful entries) and strong confidentiality through detailed evaluations with 42 participants (...

[hal-01932372] On the convergence of a stochastic approximation method for structured bi-level optimization

Publications ENAC - Tuesday, 4 December 2018 - 16:02:29
We analyze the convergence of stochastic gradient methods for well structured bi-level optimization problems. We address two specific cases: first when the outer objective function can be expressed as a finite sum of independent terms, and next when both the outer and inner objective functions can be expressed as finite sums of independent terms. We assume Lipschitz continuity and differentiability of both objectives as well as convexity of the inner objective and consider diminishing steps sizes. We show that, under these conditions and some other assumptions on the implicit function and the variance of the gradient errors, both methods converge in expectation to a...

[tel-01929593] Modeling the Atmospheric Propagation of Electromagnetic Waves in 2D and 3D Using Fourier and Wavelet Transforms

Publications ENAC - Saturday, 1 December 2018 - 00:03:54
The long-range propagation is a major issue in telecommunication, navigation, and surveillance. For simulating the electromagnetic wave propagation in a 2D atmosphere, the split-step Fourier method (SSF) is widely used. The computation is performed marching on in distances taking into account a variable refractivity, an irregular relief, and the electric characteristics of the ground. The objective of this Ph.D. thesis was to develop fast and accurate modeling methods for the tropospheric propagation in 2D and 3D. In this work, three main contributions towards this objective have been achieved. A self-consistent method, i.e. based on the discrete electromagnetic theory,...

[hal-01925466] Smooth Bias Estimation for Multipath Mitigation Using Sparse Estimation

Publications ENAC - Friday, 23 November 2018 - 12:33:27
Multipath remains the main source of error when using lobal navigation satellite systems (GNSS) in 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, which depends nonlinearly on the receiver position and linearly on the clock bias and drift, and possible biases affecting GNSS measurements. The extended Kalman filter is used to linearize the navigation problem whereas sparse estimation is considered to estimate multipath biases. We assume that only a part of the satellites are affected by multipath, i.e., that the unknown bias...

[hal-01925385] Robust DoA estimation in case of multipath environment for a sense and avoid airborne radar

Publications ENAC - Friday, 23 November 2018 - 12:32:57
This paper deals with the sense and avoid problem for an helicopter. The objective of such a system is to early detect collision targets (typically high voltage wires). The Direction of Arrival (DoA) of the target is then a crucial information. In severe multipath environments (flight over a river, for instance) classical DoA estimation schemes dramatically degrade. In this paper, we make use of a method based on the Maximum Likelihood (ML) principle that can resolve two highly correlated and close targets. The major drawback of ML algorithms, namely the computational burden, is removed using an approximation for closely space targets. The contribution of this paper is...
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