One way to design the control law of a mini-UAV.

International audienceThis paper deals with a method used to design the control law of the μDrone MAV. This vehicle uses six propellers to fly and the dynamic model approximation for the motion is a MIMO linear time-invariant system. As we want to design a linear regulator, it is necessary to build a robust feedback control law. The LQ state feedback regulator design is applied to a standard model, tacking into account some perturbations. This is why the model is augmented with a perturbation vector and an observable subsystem is extracted in order to build a state estimator whose gain is the solution of a LQ problem. The subsystem is then decomposed into a controllable set and an uncontrollable one. The use of an asymptotic rejection strategy of the influence of uncontrollable modes gives the possibility to find a state feedback applied only to the controllable ones. Here again feedback matrix is chosen as the solution of a LQ problem. To compute the weighting matrices of quadratic criterions we use a “partial observability gramian”. The great advantage of this method is due to the use of only three scalars to synthesize the control law

Inventaire des concepts info-documentaires mobilisés dans les activités de recherche d\u27informations en ligne

Travaux réalisés par un groupe d\u27enseignants-documentalistes de l\u27Académie de Nantes consacrés à la modélisation de l\u27activité de recherche d\u27informations en ligne et aux concepts info-documentaires

Les dysarthries acquises de l'enfant

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Latency Detection Threshold of Head-Tracking for Different Head Rotation Speeds in Binaural Rendering

International audienceWhen a head-tracking system is coupled with a binaural rendering, the latter becomes dynamic. Above all, a headtracking system allows consistency between the orientation of the head and the audio rendering. This dynamism has many advantages, such as improved externalization, localization accuracy, or realism. However, an excessive latency between the head-tracking system and the audio rendering leads to a feeling of incoherence and/or slewing, which is detrimental to the listening experience. In this paper, the detection threshold of head-tracking latency was estimated using an adaptive procedure. This task was performed using three head rotation speeds and a total of six different sound scenes : a pink noise, a male speech with and without reverberation, a pair of congas with and without reverberation, and a complex scene (a realistic coffee shop ambiance, containing six distinct sources with reverberation)

Seuil de détection de la latence des systèmes de head-tracking pour différentes vitesses de rotation de tête en écoute binaurale.

International audienceSeuil de détection de la latence des systèmes de head-tracking pour différentes vitesses de rotation de tête en écoute binaurale

Latency Detection Threshold of Head-Tracking with and without Individualized HRIRs in Binaural Rendering

International audienceBy coupling a head-tracking system with a binaural rendering, the latter becomes dynamic. This allows coherence between the orientation of a listener’s head and the virtual sound scene. Nevertheless, the head-tracking data has to be transmitted to the audio rendering, which must then compute the orientation of a new virtual audio scene. In this way, a latency between the head movement and the audio rendering is unavoidable. If this latency is too high, a feeling of elasticity, or even spatial incoherence, is felt, which is detrimental to the listening experience.In this study, a perceptual test was conducted in order to investigate the influence of HRIRs on a latency detection threshold task, using an adaptive procedure. The subjects listened to two excerpts (a male voice and a pink noise) with their own HRIRs or with non-individual HRIRs. Two head movements in azimuth, with different rotation speeds, were imposed. Results showed significant differences between slow and fast movements and between the pink noise and the male voice. No global difference was observed between non-individual and individual HRIRs

Flood hazard mitigation by actions in the hillslopes: does the context change the assessment of efficiency?

For sustainable and integrated flood management, small actions in the hillslopes and non-structural measures appear interesting, either to diminish the need for large flood mitigation infrastructures (whether sewerage networks or hydraulic structures in the river – which may have severe impact on the river ecosystems), or as complementary to these structures. However, the effect on flood mitigation of land-use modification and small storage or runoff control facilities is still debated in scientific literature. The effect of various structures spread over the catchment is difficult to assess, and hazardous to generalize from one studied catchment to another, which explains why the debate is still open. This study contributes to identify context features that could also explain constrasting results. Focusing on a West-Mediterranean Northern and Southern countries literature, we compare first traditionnal and modern hillslope actions against runoff in both countries. Then, we search in the physical contexts differences that might explain why actions in the hillslopes are more studied in Europe than in Maghreb. But the priorities of national or regional policies also explain differences in the perception of efficiency: the interest of hillslope actions is different if the aim is to limit erosion and pollutant transfer and/or to mitigate large floods. Pollution and how ecological status is taken into account in flood mitigation project assessment are also crucial points

Flood hazard mitigation by actions in the hillslopes: does the context change the assessment of efficiency?

For sustainable and integrated flood management, small actions in the hillslopes and non-structural measures appear interesting, either to diminish the need for large flood mitigation infrastructures (whether sewerage networks or hydraulic structures in the river – which may have severe impact on the river ecosystems), or as complementary to these structures. However, the effect on flood mitigation of land-use modification and small storage or runoff control facilities is still debated in scientific literature. The effect of various structures spread over the catchment is difficult to assess, and hazardous to generalize from one studied catchment to another, which explains why the debate is still open. This study contributes to identify context features that could also explain constrasting results. Focusing on a West-Mediterranean Northern and Southern countries literature, we compare first traditionnal and modern hillslope actions against runoff in both countries. Then, we search in the physical contexts differences that might explain why actions in the hillslopes are more studied in Europe than in Maghreb. But the priorities of national or regional policies also explain differences in the perception of efficiency: the interest of hillslope actions is different if the aim is to limit erosion and pollutant transfer and/or to mitigate large floods. Pollution and how ecological status is taken into account in flood mitigation project assessment are also crucial points

Bayeux Tapestry: First use of early synthetic dyes for the restoration of a masterpiece

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