No description available.

Dans ce travail, nous avons premièrement développé et caractérisé des capteurs de flux optique robustes aux changements de conditions lumineuses inspirés par le système visuel de la mouche et mesurant la vitesse angulaire à l'aide de l'algorithme appelé "time of travel". En particulier, nous avons comparé les performances de capteurs mesurant visuellement la vitesse angulaire en intérieur et en extérieur. Les résultats de nos capteurs bio-inspirés ont aussi été comparés avec des capteurs de souris optique. Enfin, une nouvelle implémentation de l'algorithme "time of travel" a été proposée réduisant la charge de calcul de l'unité de traitement.Dans le cadre du projet européen CurvACE (Curved Artificial Compound Eye), nous avons aussi participé au développement du premier oeil composé courbé artificiel capable de mesurer le flux optique à haute vitesse sur une large gamme de lumière ambiante. En particulier, nous avons caractérisé ce capteur et montré sa capacité à mesurer le flux optique à l'aide de plusieurs algorithmes.Finalement, nous avons aussi développé un robot aérien miniature attaché appelé BeeRotor équipé de capteurs et de stratégies de vol imitant les insectes volants et se déplaçant de manière autonome dans un tunnel contrasté. Ce robot peut expliquer comment les abeilles contrôlent leur vitesse et leur position à l'aide du flux optique, tout en démontrant que des solutions alternatives existent aux systèmes couramment utilisés en robotique. Basé seulement sur des boucles de contrôle réagissant à l'environnement, cet hélicoptère a démontré sa capacité à voler de manière autonome dans un environnement complexe et mobile. / In this thesis, we first developed and characterized optic flow sensors robust to illuminance changes inspired by the visual system of the fly and computing the angular speed thanks to the "time of travel" scheme. In particular, we have compared the performances of sensors processing the visual angular speed based on a standard retina or an aVLSI retina composed of pixels automatically adapting to the background illuminance in indoor and outdoor environments. The results of such bio-inspired sensors have also been compared with optic mouse sensors which are used nowadays on Micro Aerial Vehicles to process the optic flow but only in outdoor environments. Finally, a new implementation of the "time of travel" scheme has been proposed reducing the computational load of the processing unit.In the framework of the European project CurvACE, we also participated to the design and development of the first curved artificial compound eye including fast motion detection in a very large range of illuminations. In particular, we characterized such sensor showing its ability to extract optic flow using different algorithms.Finally, we also developed a tethered miniature aerial robot equipped with sensors and control strategies mimicking flying insects navigating in a high-roof tunnel. This robot may explain how honeybees control their speed and position thanks to optic flow, while demonstrating alternative solution to classical robotic approach relying on ground-truth and metric sensors. Based only on visuomotor control loops reacting suitably to the environment, this rotorcraft has shown its ability to fly autonomously in complex and unstationary tunnels.

M.Sc. / The grassland biome of South Africa harbours rich ecosystem diversity. Some of the distinctive features of grassland biodiversity in South Africa include globally significant centres of plant endemism, half of the country's endemic mammal species, a third of its endangered butterfly species and 10 of 14 of its globally threatened bird species. Grassland is one of the most inadequately maintained biomes in Southern Africa because 23% is under cultivation, 60% is irreversibly transformed and most of the remaining natural area is used as rangeland for livestock. Only 2% of the grassland biome is currently protected. Grasslands provide essential ecosystem services for economic development, but this biome also supports a large human population whose resource demands have serious environmental implications that threaten the grasslands‘ biodiversity. Urbanisation is possibly one of the major immediate threats to the grassland ecology in South Africa. This is also the case in the Cradle of Humankind World Heritage Site (COHWHS) and adjacent areas. New housing complexes and informal housing are encroaching on the COHWHS. Indigenous fauna and flora are being affected by ecologically insensitive urban development. This poses a major threat to the fauna of this region including the insects that occur in grassland habitats. The insects play a vital role as pollinators in grassland habitats and form an essential food source to a range of predators, including grass owls, shrews, bull frogs, lizards and bats. In order to conserve the insects and therefore the food web of which they form part, it is necessary to understand the diversity of the insects in the grassland in the dolomitic areas. The COHWHS is a world renowned heritage site devoted to the origin of humankind and is characterised by dolomitic caves. These caves are also the home of a large population of bats consisting of several species. The negative impact on the grasslands in the COHWHS and surroundings pose a threat to the survival of these bat populations if the food source they depend on is negatively affected. For this reason it is important to determine which flying nocturnal insect species are available in the grasslands surrounding bat roosts in the COHWHS and surroundings. 3 The choice of location for the primary trap site was made on the basis of its proximity to known bat roosts and the fact that it is situated in a nature reserve that, although the river is polluted, contains an otherwise relatively unspoilt grassland habitat. Sampling took place over a period of 14 months during which fluctuations in the insect population was observed. The fluctuations can be ascribed to seasonal climate changes and the three veld fires that occurred during this period. This fluctuation was most evident in the representatives of the Orders Lepidoptera and Coleoptera sampled.