Applied Nonlinear Control of Unmanned Vehicles with Uncertain Dynamics

The presented research concerns the control of unmanned vehicles. The results introduced in this dissertation provide a solid control framework for a wide class of nonlinear uncertain systems, with a special emphasis on issues related to implementation, such as control input amplitude and rate saturation, or partial state measurements availability. More specifically, an adaptive control framework, allowing to enforce amplitude and rate saturation of the command, is developed. The motion control component of this framework, which works in conjunction with a saturation algorithm, is then specialized to different types of vehicles. Vertical take-off and landing aerial vehicles and a general class of autonomous marine ve-hicles are considered. A nonlinear control algorithm addressing the tracking problem for a class of underactuated, non-minimum phase marine vehicles is then introduced. This motion controller is extended, using direct and indirect adaptive techniques, to handle parametric uncertainties in the system model. Numerical simulations are used to illustrate the efficacy of the algorithms. Next, the output feedback control problem is treated, for a large class of nonlinear and uncertain systems. The proposed solution relies on a novel nonlinear observe

Estimation of relative position and coordination of mobile underwater robotic platforms through electric sensing.

International audienceIn the context of underwater robotics, positioning and coordination of mobile agents can prove a challenging problem. To address this issue, we propose the use of electric sensing, with a technique inspired by weakly electric fishes. In particular, the approach relies on one or several of the agents applying an electric field to their environment. Using electric measures, others agents are able to reconstruct their relative position with respect to the emitter, over a range that is function of the geometry of the emitting agent and of the power applied to the environment. Efficacy of the technique is illustrated using a number of numerical examples. The approach is shown to allow coordination of unmanned underwater vehicles, including that of bio-inspired swimming robotic platforms

Action-Perception Trade-Offs for Anguilliform Swimming Robotic Platforms with an Electric Sense

International audienceThe work presented addresses the combination of anguilliform swimming-based propulsion with the use of an electric sensing modality for a class of unmanned underwater vehicles, and in particular investigates the relative influence of adjustments to the swimming gait on the platform's displacement speed and on sensing performance. This influence is quantified, for a relevant range of swimming gaits, using experimental data recordings of displacement speeds, and a boundary element method-based numerical simulation tool allowing to reconstruct electric measures. Results show that swimming gaits providing greater movement speeds tend to degrade sensing performance. Conversely, gaits yielding accurate sensing tend to prove slower. To reconcile opposing tendencies, a simple action-perception cost function is designed, with the purpose of adjusting an anguilliform swimmer's gait shape, in accordance with respective importance afforded to action (i.e. movement speed) and perception

ProcNet: Deep Predictive Coding Model for Robust-to-occlusion Visual Segmentation and Pose Estimation

Systems involving human-robot collaboration necessarily require that steps be taken to ensure safety of the participating human. This is usually achievable if accurate, reliable estimates of the human's pose are available. In this paper, we present a deep Predictive Coding (PC) model supporting visual segmentation, which we extend to pursue pose estimation. The model is designed to offer robustness to the type of transient occlusion naturally occurring when human and robot are operating in close proximity to one another. Impact on performance of relevant model parameters is assessed, and comparison to an alternate pose estimation model (NVIDIA's PoseCNN) illustrates efficacy of the proposed approach.Comment: 7 pages, 9 figure

Perspectives de la distribution des produits issus de l’agriculture biologique dans les Pays de la Loire

La distribution représente un levier important de développement de la filière biologique régionale. Si cette idée est admise par les professionnels de l’agriculture biologique, ils demeurent souvent réticents à l’égard de la logique des distributeurs. Les résultats de l’étude mettent en évidence l’importance de leurs attentes. Pour informer les consommateurs sur le bio, la relation avec les chefs de rayon des GMS joue un rôle particulièrement déterminant dans la largeur des gammes de produits offerts aux consommateurs. A cet effet, dans les GMS comme dans les magasins spécialisés, les professionnels doivent envisager de communiquer plus clairement sur le bio en tant que mode de production respectueux de l’environnement, car ce signe n’est pas seulement (pas d’abord ?) porteur d’une qualité alimentaire moins risquée. Ce qui implique que les producteurs et les distributeurs s’accordent, comme c’est le cas chez Auchan plusieurs fois par an, pour ajuster le message à tenir auprès du public client

Dopexamine and norepinephrine versus epinephrine on gastric perfusion in patients with septic shock: a randomized study [NCT00134212]

INTRODUCTION: Microcirculatory blood flow, and notably gut perfusion, is important in the development of multiple organ failure in septic shock. We compared the effects of dopexamine and norepinephrine (noradrenaline) with those of epinephrine (adrenaline) on gastric mucosal blood flow (GMBF) in patients with septic shock. The effects of these drugs on oxidative stress were also assessed. METHODS: This was a prospective randomized study performed in a surgical intensive care unit among adults fulfilling usual criteria for septic shock. Systemic and pulmonary hemodynamics, GMBF (laser-Doppler) and malondialdehyde were assessed just before catecholamine infusion (T(0)), as soon as mean arterial pressure (MAP) reached 70 to 80 mmHg (T(1)), and 2 hours (T(2)) and 6 hours (T(3)) after T(1). Drugs were titrated from 0.2 μg kg(-1 )min(-1 )with 0.2 μg kg(-1 )min(-1 )increments every 3 minutes for epinephrine and norepinephrine, and from 0.5 μg kg(-1 )min(-1 )with 0.5 μg kg(-1 )min(-1 )increments every 3 minutes for dopexamine. RESULTS: Twenty-two patients were included (10 receiving epinephrine, 12 receiving dopexamine–norepinephrine). There was no significant difference between groups on MAP at T(0), T(1), T(2), and T(3). Heart rate and cardiac output increased significantly more with epinephrine than with dopexamine–norepinephrine, whereas. GMBF increased significantly more with dopexamine–norepinephrine than with epinephrine between T(1 )and T(3 )(median values 106, 137, 133, and 165 versus 76, 91, 90, and 125 units of relative flux at T(0), T(1), T(2 )and T(3), respectively). Malondialdehyde similarly increased in both groups between T(1 )and T(3). CONCLUSION: In septic shock, at doses that induced the same effect on MAP, dopexamine–norepinephrine enhanced GMBF more than epinephrine did. No difference was observed on oxidative stress

Numerical modelling of microorganisms dispersion in urban area : application to legionella

International audienceDispersion modelling is often used to estimate potentially contaminated areas in case of accidental release of microorganisms in the atmosphere. In the specific case of Legionella, accidental spread in the atmosphere due to contaminated cooling towers system may occur over distance larger than 10km. In addition, most cooling towers are located in urban areas where dispersion due to obstacles is complex. In this case, dispersion models have to take into account complex flows and microphysical processes that occur within the plume and may have an impact on the survival of the microorganisms. To estimate the concentration of microorganisms in these areas, a specific module has been developed within the lagrangian dispersion model Micro Swift Spray (MSS, Aria technologies). This module takes into account microorganisms outside or inside water liquid droplets and microphysical interaction inside the plume. A simple biological module governing the survival of airborne microorganisms has also been implemented in the dispersion model