Evaluation environnementale de bétons de granulats recyclés de béton et de béton de granulats recyclés de terre cuite à partir d'analyses de cycle de vie

National audienceRecycled concrete aggregates from demolition constitute one of the largest waste streams within the developed countries. This paper aims to quantify the environmental impacts related to the mixing composition of concrete materials by implementing a life cycle assessment (LCA). The originality of this study is to evaluate the performances of three concrete samples (natural, recycled and mixed), formulated to reach the same mechanical strength regarding the functional unit. Three micro-concrete samples, formulated with natural or recycled aggregates (concrete or terracotta brick), were also studied and developed with the same volume composition regardless to the granular skeleton. The LCA results are presented using various impact assessment methods, according to both EN 15804 and NF P 01-010 standards.Les granulats recyclés de béton, issus de la démolition, constituent de nos jours l'un des plus grands flux de déchets dans les pays développés. Cet article propose de quantifier les impacts environnementaux associés à la formulation de différents bétons en utilisant une analyse de cycle de vie (ACV). L'originalité de cette étude est d'évaluer les performances de trois bétons (naturel, recyclé et mixte), dont les formulations ont été définies en recherchant la même classe de résistance C35/45 (dosage en ciment fixé à 350 kg/m 3) au regard de l'unité fonctionnelle. Trois autres échantillons – des micro-bétons (0/8 mm), formulés à partir de granulats naturels ou recyclés (béton ou terre cuite) – ont été élaborés avec comme critère de formulation une même composition volumique du squelette granulaire. Les résultats de l'ACV sont présentés selon différentes méthodes d'évaluation des impacts, en conformité avec les normes EN 15804 et NF P 01-010

Optic Flow Based Autopilots: Speed Control and Obstacle Avoidance

International audienceThe explicit control schemes presented here explain how insects may navigate on the sole basis of optic flow (OF) cues without requiring any distance or speed measurements: how they take off and land, follow the terrain, avoid the lateral walls in a corridor and control their forward speed automatically. The optic flow regulator, a feedback system controlling either the lift, the forward thrust or the lateral thrust, is described. Three OF regulators account for various insect flight patterns observed over the ground and over still water, under calm and windy conditions and in straight and tapered corridors. These control schemes were simulated experimentally and/or implemented onboard two types of aerial robots, a micro helicopter (MH) and a hovercraft (HO), which behaved much like insects when placed in similar environments. These robots were equipped with opto-electronic OF sensors inspired by our electrophysiological findings on houseflies' motion sensitive visual neurons. The simple, parsimonious control schemes described here require no conventional avionic devices such as range finders, groundspeed sensors or GPS receivers. They are consistent with the the neural repertoire of flying insects and meet the low avionic payload requirements of autonomous micro aerial and space vehicles

Biomimetic visual navigation in a corridor: to centre or not to centre?

International audienceAs a first step toward an Automatic Flight Control System (AFCS) for Micro-Air Vehicle (MAV) obstacle avoidance, we introduce a vision based autopilot (LORA: Lateral Optic flow Regulation Autopilot), which is able to make a hovercraft automatically follow a wall or centre between the two walls of a corridor. A hovercraft is endowed with natural stabilization in pitch and roll while keeping two translational degrees of freedom (X and Y) and one rotational degree of freedom (yaw Ψ). We show the feasibility of an OF regulator that maintains the lateral Optic Flow (OF) on one wall equal to an OF set-point. The OF sensors used are Elementary Motion Detectors (EMDs), whose working was directly inspired by the housefly motion detecting neurons. The properties of these neurons were previously analysed at our laboratory by performing electrophysiological recordings while applying optical microstimuli to single photoreceptor cells of the compound eye. The simulation results show that depending on the OF set-point, the hovercraft either centres along the midline of the corridor or follows one of the two walls, even with local lack of optical texture on one wall, such as caused, for instance, by an open door or a T-junction. All these navigational tasks are performed with one and the same feedback loop, which consists of a lateral OF regulation loop that permits relatively high-speed navigation (1m/s, i.e 3 body-lengths per second). The passive visual sensors and the simple processing system are suitable for use with MAVs with an avionic payload of only a few grams. The goal is to achieve MAV automatic guidance or to relieve a remote operator from guiding it in challenging environments such as urban canyons or indoor environments

Optic Flow Based Visual Guidance: From Flying Insects to Miniature Aerial Vehicles

International audienc

3D Navigation With An Insect-Inspired Autopilot

ISBN : 978-2-9532965-0-1Using computer-simulation experiments, we developed a vision-based autopilot that enables a ‘simulated bee' to travel along a tunnel by controlling both its speed and its clearance from the right wall, the left wall, the ground, and the ceiling. The flying agent can translate along three directions (surge, sway, and heave): the agent is therefore fully actuated. The visuo-motor control system, called ALIS (AutopiLot using an Insect based vision System), is a dual OF regulator consisting of two interdependent feedback loops, each of which has its own OF set-point. The experiments show that the simulated bee navigates safely along a straight tunnel, while reacting sensibly to the major OF perturbation caused by the presence of a tapered tunnel. The visual system is minimalistic (only eight pixels) and it suffices to control the clearance from the four walls and the forward speed jointly, without the need to measure any speeds and distances. The OF sensors and the simple visuo-motor control system developed here are suitable for use on MAVs with avionic payloads as small as a few grams. Besides, the ALIS autopilot accounts remarkably for the quantitative results of ethological experiments performed on honeybees flying freely in straight or tapered corridors

A bee in the corridor: centering and wall-following

International audienceIn an attempt to better understand the mechanism underlying lateral collision avoidance in 7 flying insects, we trained honeybees (Apis mellifera) to fly through a large (95cm-wide) flight 8 tunnel. We found that depending on the entrance and feeder positions, honeybees would 9 either center along the corridor midline or fly along one wall. Bees kept following one wall 10 even when a major (150cm-long) part of the opposite wall was removed. These findings 11 cannot be accounted for by the 'optic flow balance' hypothesis that has been put forward to 12 explain the typical bees' 'centering response' observed in narrower corridors. Both centering 13 and wall-following behaviours are well accounted for, however, by a mechanism called the 14 lateral optic flow regulator, i.e., a feedback system that strives to maintain the unilateral optic 15 flow constant. The power of this mechanism is that it would allow the bee to guide itself 16 visually in a corridor without having to measure its speed or distance from the walls

A 3D insect-inspired visual autopilot for corridor-following

International audienceMotivated by the results of behavioral studies performed on bees over the last two decades, we have attempted to decipher the logics behind the bee's autopilot, with specific reference to their use of optic flow (OF). Using computer-simulation experiments, we developed a vision-based autopilot that enables a 'simulated bee' to travel along a tunnel by controlling both its speed and its clearance from the walls, the ground, and the ceiling. The flying agent is fully actuated and can translate along three directions: surge, sway, and heave. The visuo-motor control system, called ALIS (AutopiLot using an Insect based vision System), is a dual OF regulator consisting of intertwined feedback loops, each of which has its own OF set-point. The experiments show that the simulated bee navigates safely along a straight or tapered tunnel and reacts sensibly to major OF perturbations caused, e.g., by the lack of texture on one wall or by the presence of a tapered tunnel. The agent is equipped with a minimalistic visual system (comprised of only eight pixels) that suffices to control the clearance from the four walls and the forward speed jointly, without the need to measure any speeds and distances. The OF sensors and the simple visuo-motor control system developed here are suitable for use on MAVs with avionic payloads as small as a few grams. Besides, the ALIS autopilot accounts remarkably for the quantitative results of ethological experiments performed on honeybees flying freely in straight or tapered corridors

Neuromimetic Robots inspired by Insect Vision

International audienceEquipped with a less-than-one-milligram brain, insects fly autonomously in complex environments without resorting to any Radars, Ladars, Sonars or GPS. The knowledge gained during the last decades on insects' sensory-motor abilities and the neuronal substrates involved provides us with a rich source of inspiration for designing tomorrow's self-guided vehicles and micro-vehicles, which are to cope with unforeseen events on the ground, in the air, under water or in space. Insects have been in the business of sensory-motor integration for several 100 millions years and can therefore teach us useful tricks for designing agile autonomous vehicles at various scales. Constructing a "biorobot" first requires exactly formulating the signal processing principles at work in the animal. It gives us, in return, a unique opportunity of checking the soundness and robustness of those principles by bringing them face to face with the real physical world. Here we describe some of the visually-guided terrestrial and aerial robots we have developed on the basis of our biological findings. These robots (Robot Fly, SCANIA, FANIA, OSCAR, OCTAVE and LORA) all react to the optic flow (i.e., the angular speed of the retinal image). Optic flow is sensed onboard the robots by miniature vision sensors called Elementary Motion Detectors (EMDs). The principle of these electro-optical velocity sensors was derived from optical/electrophysiological studies where we recorded the responses of single neurons to optical microstimulation of single photoreceptor cells in a model visual system: the fly's compound eye. Optic flow based sensors rely solely on contrast provided by reflected (or scattered) sunlight from any kind of celestial bodies in a given spectral range. These nonemissive, powerlean sensors offer potential applications to manned or unmanned aircraft. Applications can also be envisaged to spacecraft, from robotic landers and rovers to asteroid explorers or space station dockers, with interesting prospects as regards reduction in weight and consumption

A bee in the corridor: regulating the optic flow on one side

International audienceTo work out the information flow underlying the honeybee's anti-collision system, we performed a frame-by-frame analysis of the trajectories of individual bees (Apis Mellifera) flying in a wide outdoor flight tunnel. Forward speed Vx and distance D to one of the two walls happen to be proportional to each other, attesting that the angular velocity Vx/D (Optic Flow, OF) of the image of that same wall is held constant. Like the landing bee holding the downward OF constant (Srinivasan et al. 1996), the bee holds either the left or right OF constant. The bee's behaviour is well accounted for by a lateral optic flow regulator scheme. Simulations showed that this scheme can make a (fully actuated) hovercraft automatically adjust its distance to a wall by regulating the OF on one side (Serres et al., IEEE Biorob 2006)

Influence d'un bio-adjuvant sur les propriétés mécaniques et la porosité de mortiers

National audienceABSTRACT: the purpose of this paper is to examine the influence of a bio-admixture on compressive strength, flexion strength, as well as porosity of mortars at constant water on cement ratio (W/C = 0.5). The results showed that, for a long curing period (120 days), the addition of bioadmixture (2 and 2.5%) leads to an improvement of compressive strength of mortars. The porosity of mortars is not significantly affected by the addition of bioadmixture. However, increasing of curing period caused a decrease of the kinetics of capillary imbibition.RESUME: l'objectif de cette étude est d'évaluer l'effet d'un nouveau bio-adjuvant sur les propriétés mécaniques et la porosité de mortiers. Différentes concentrations de bio-adjuvant (0 ; 0,5 ; 1 ; 1,5 ; 2 et 2,5%) ont été ajoutées à des mortiers contenant du ciment CEM I (E/C = 0,5). La résistance en compression, la résistance en flexion, la porosité totale à l'eau et l'imbibition capillaire des mortiers ont été évaluées. Après 120 jours de cure dans l'eau, les mortiers avec 2 et 2,5% de bio-adjuvant présentent des résistances à la compression supérieures à celle des mortiers sans bio-adjuvant. Les essais de porosité totale à l'eau et d'imbibition capillaire des mortiers montrent une faible influence du bio-adjuvant utilisé sur la structure poreuse des mortiers. Cependant, le temps de cure à partir de 30 jours et jusqu'à 120 jours a entraîné une diminution de la cinétique d'imbibition capillaire