Planification et commande d'une plate-forme aéroportée stationnaire autonome dédiée à la surveillance des ouvrages d'art

Today, the inspection of structures is carried out through visual assessments effectedby qualified inspectors. This procedure is very expensive and can put the personal indangerous situations. Consequently, the development of an unmanned aerial vehicleequipped with on-board vision systems is privileged nowadays in order to facilitate theaccess to unreachable zones.In this context, the main focus in the thesis is developing original methods to deal withplanning, reference trajectories generation and tracking issues by a hovering airborneplatform. These methods should allow an automation of the flight in the presence of airdisturbances and obstacles. Within this framework, we are interested in two kinds ofaerial vehicles with hovering capacity: airship and quad-rotors.Aujourd'hui, l'inspection des ouvrages d'art est réalisée de façon visuelle par des contrôleurs sur l'ensemble de la structure. Cette procédure est coûteuse et peut être particulièrement dangereuse pour les intervenants. Pour cela, le développement du système de vision embarquée sur des drones est privilégié ces jours-ci afin de faciliter l'accès aux zones dangereuses.Dans ce contexte, le travail de cette thèse porte sur l'obtention des méthodes originales permettant la planification, la génération des trajectoires de référence, et le suivi de ces trajectoires par une plate-forme aéroportée stationnaire autonome. Ces méthodes devront habiliter une automatisation du vol en présence de perturbations aérologiques ainsi que des obstacles. Dans ce cadre, nous nous sommes intéressés à deux types de véhicules aériens capable de vol stationnaire : le dirigeable et le quadri-rotors.Premièrement, la représentation mathématique du véhicule volant en présence du vent a été réalisée en se basant sur la deuxième loi de Newton. Deuxièmement, la problématique de génération de trajectoire en présence de vent a été étudiée : le problème de temps minimal est formulé, analysé analytiquement et résolu numériquement. Ensuite, une stratégie de planification de trajectoire basée sur les approches de recherche opérationnelle a été développée.Troisièmement, le problème de suivi de trajectoire a été abordé. Une loi de commande non-linéaire robuste basée sur l'analyse de Lyapunov a été proposée. En outre, un pilote automatique basée sur les fonctions de saturations pour un quadri-rotors a été développée.Les méthodes et algorithmes proposés dans cette thèse ont été validés par des simulations

Impact of missing participant data for dichotomous outcomes on pooled effect estimates in systematic reviews : a protocol for a methodological study

Abstract Background There is no consensus on how authors conducting meta-analysis should deal with trial participants with missing outcome data. The objectives of this study are to assess in Cochrane and non-Cochrane systematic reviews: (1) which categories of trial participants the systematic review authors consider as having missing participant data (MPD), (2) how trialists reported on participants with missing outcome data in trials, (3) whether systematic reviewer authors actually dealt with MPD in their meta-analyses of dichotomous outcomes consistently with their reported methods, and (4) the impact of different methods of dealing with MPD on pooled effect estimates in meta-analyses of dichotomous outcomes. Methods/Design We will conduct a methodological study of Cochrane and non-Cochrane systematic reviews. Eligible systematic reviews will include a group-level meta-analysis of a patient-important dichotomous efficacy outcome, with a statistically significant effect estimate. Teams of two reviewers will determine eligibility and subsequently extract information from each eligible systematic review in duplicate and independently, using standardized, pre-piloted forms. The teams will then use a similar process to extract information from the trials included in the meta-analyses of interest. We will assess first which categories of trial participants the systematic reviewers consider as having MPD. Second, we will assess how trialists reported on participants with missing outcome data in trials. Third, we will compare what systematic reviewers report having done, and what they actually did, in dealing with MPD in their meta-analysis. Fourth, we will conduct imputation studies to assess the effects of different methods of dealing with MPD on the pooled effect estimates of meta-analyses. We will specifically calculate for each method (1) the percentage of systematic reviews that lose statistical significance and (2) the mean change of effect estimates across systematic reviews. Discussion The impact of different methods of dealing with MPD on pooled effect estimates will help judge the associated risk of bias in systematic reviews. Our findings will inform recommendations regarding what assumptions for MPD should be used to test the robustness of meta-analytical results

Planning and control of an autonomous hovering airborne dedicated for the monitoring of structures

Aujourd'hui, l'inspection des ouvrages d'art est réalisée de façon visuelle par des contrôleurs sur l'ensemble de la structure. Cette procédure est couteuse et peut être particulièrement dangereuse pour les intervenants. Pour cela, le développement du système de vision embarquée sur des drones est privilégié ces jours-ci afin de faciliter l'accès aux zones dangereuses.Dans ce contexte, le travail de cette thèse porte sur l'obtention des méthodes originales permettant la planification, la génération des trajectoires de référence, et le suivi de ces trajectoires par une plate-forme aéroportée stationnaire autonome. Ces méthodes devront habiliter une automatisation du vol en présence de perturbations aérologiques ainsi que des obstacles. Dans ce cadre, nous nous sommes intéressés à deux types de véhicules aériens capable de vol stationnaire : le dirigeable et le quadri-rotors.Premièrement, la représentation mathématique du véhicule volant en présence du vent a été réalisée en se basant sur la deuxième loi de Newton. Deuxièmement, la problématique de génération de trajectoire en présence de vent a été étudiée : le problème de temps minimal est formulé, analysé analytiquement et résolu numériquement. Ensuite, une stratégie de planification de trajectoire basée sur les approches de recherche opérationnelle a été développée.Troisièmement, le problème de suivi de trajectoire a été abordé. Une loi de commande non-linéaire robuste basée sur l'analyse de Lyapunov a été proposée. En outre, un pilote automatique basée sur les fonctions de saturations pour un quadri-rotors a été développée.Les méthodes et algorithmes proposés dans cette thèse ont été validés par des simulations.Today, the inspection of structures is carried out through visual assessments effected by qualified inspectors. This procedure is very expensive and can put the personal in dangerous situations. Consequently, the development of an unmanned aerial vehicle equipped with on-board vision systems is privileged nowadays in order to facilitate the access to unreachable zones.In this context, the main focus in the thesis is developing original methods to deal with planning, reference trajectories generation and tracking issues by a hovering airborne platform. These methods should allow an automation of the flight in the presence of air disturbances and obstacles. Within this framework, we are interested in two kinds of aerial vehicles with hovering capacity: airship and quad-rotors.Firstly, the mathematical representation of an aerial vehicle in the presence of wind has been realized using the second law of newton.Secondly, the question of trajectory generation in the presence of wind has been studied: the problem of minimal time was formulated, analyzed analytically and solved numerically. Then, a strategy of trajectory planning based on operational research approaches has been developed.Thirdly, the problem of trajectory tracking was carried out. A nonlinear robust control law based on Lyapunov analysis has been proposed. In addition, an autopilot based on saturation functions for quad-rotor crafts has been developed.All methods and algorithms proposed in this thesis have been validated through simulations

Analysis of Time Optimal 3D Paths for an Autonomous Aircraft with a Piecewise Constant Acceleration

International audienceTrajectory generation is a fundamental part of planning for an autonomous aerial vehicle. For the purpose of flight path generation, it is usually sufficient to treat only the translational motion. One component of the weather that greatly affects an aircraft trajectory is the wind. Study of the accessibility of this nonlinear affine system with drift makes use of the Lie algebra rank condition. The second part of this paper presents 3D time optimal translational trajectories characterization for an aircraft in steady wind. If unaccounted for, winds can substantially degrade the performance of an autonomous aircraft guidance system. We consider finding a time optimal trajectory for an airplane from some starting point and orientation to some final point and orientation, assuming that the system has independent bounded control over the acceleration as well as the turning rates for the flight path and heading angles. Through the use of the Pontryagin maximum principle, we characterize the time optimal trajectories for the system

Generation of time optimal trajectories of an autonomous airship

International audienceThe natural wind proved itself to be a major parameter to successful flights of airships. It mostly affects a trajectory through its speed. In general, the wind speed can be modeled as a sum of two components: a nominal deterministic component (available through meteorological forecasts or measured with a Doppler radar) and a stochastic component, representing deviations from the nominal one [1, 2]. The closed loop controller takes care of the stochastic part considered as perturbations, while the deterministic component is introduced into the motion planner. In general, the optimality of a trajectory can be defined according to several objectives, like minimizing the transfer time or the energy. Traditionally, trajectories are optimized by the application of numerical optimal control methods that are based on the calculus of variations

Time-optimal trajectories of a lighter-than-air robot in a steady wind

International audienceTrajectory generation is a fundamental part of planning for lighter-than-air robots. In the first part of this paper, the accessibility of this nonlinear affine system with drift is studied using the Lie algebra rank condition. The second one presents 3D time-optimal translational trajectories characterization for a lighter-than-air robot in steady wind. If unaccounted for, winds can substantially degrade the performance of an autonomous airship guidance system. The minimum time problem is considered using the optimal control theory to establish the 3D path between two different configurations (position and orientation), assuming that the system has independent bounded control over the acceleration as well as the turning rates for the flight path and heading angles. The contribution of the work is to do the planning in 3D with varying velocity, heading angle, and path angle, taking into account a piecewise constant wind, with a periodic update

Path tracking of a small autonomous airplane in wind gusts

International audienceIn this paper, we study the trajectory tracking problem of autonomous small airplanes in presence of unknown wind gusts. The vehicle is represented by its center of gravity, and the mathematical translational model is derived using Newton's second law. The controller is designed using Robust Control Lyapunov Function and Sontag's feedback stabilizing universal. The proposed control laws guarantees, by structure, the robustness of the system with respect to different uncertain- ties due to model and unknown external parameters. Numerical simulations are performed to demonstrate the performance of proposed control strategy

Minimum Time Reference Trajectory Generation for an Autonomous Quadrotor

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