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Laboratoire d’analyse et d’architecture des systèmes

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492documents trouvés

17447
01/04/2018

Differential flatness of quadrotor dynamics subject to rotor drag for accurate tracking of high-speed trajectories

M.FAESSLER, A.FRANCHI, D.SCARAMUZZA

Zurich, RIS

Revue Scientifique : IEEE Robotics and Automation Letters, Vol.3, N°2, pp.620-626, Avril 2018, DOI 10.1109/LRA.2017.2776353 , N° 17447

Lien : https://hal.laas.fr/hal-01658577

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Abstract

In this paper, we prove that the dynamical model of a quadrotor subject to linear rotor drag effects is differentially flat in its position and heading. We use this property to compute feed-forward control terms directly from a reference trajectory to be tracked. The obtained feed-forward terms are then used in a cascaded, nonlinear feedback control law that enables accurate agile flight with quadrotors. Compared to state-of-the-art control methods, which treat the rotor drag as an unknown disturbance, our method reduces the trajectory tracking error significantly. Finally, we present a method based on a gradient-free optimization to identify the rotor drag coefficients, which are required to compute the feed-forward control terms. The new theoretical results are thoroughly validated trough extensive comparative experiments.

141721
17270
14/12/2017

Viewing robot navigation in human environment as a cooperative activity

H.KHAMBHAITA, R.ALAMI

RIS

Manifestation avec acte : International Symposium on Robotics Research ( ISSR ) 2017 du 11 décembre au 14 décembre 2017, Puerto Varas (Chili), Décembre 2017, 18p. , N° 17270

Lien : https://hal.laas.fr/hal-01572555

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Abstract

We claim that navigation in human environments can be viewed as cooperative activity especially in constrained situations. Humans concurrently aid and comply with each other while moving in a shared space. Cooperation helps pedestrians to efficiently reach their own goals and respect conventions such as the personal space of others. To meet human comparable efficiency, a robot needs to predict the human trajectories and plan its own trajectory correspondingly in the same shared space. In this work, we present a navigation planner that is able to plan such cooperative trajectories, simultaneously enforcing the robot's kinematic constraints and avoiding other non-human dynamic obstacles. Using robust social constraints of projected time to a possible future collision, compatibility of human-robot motion direction, and proxemics, our planner is able to replicate human-like navigation behavior not only in open spaces but also in confined areas. Besides adapting the robot trajectory, the planner is also able to proactively propose co-navigation solutions by jointly computing human and robot trajectories within the same optimization framework. We demonstrate richness and performance of the cooperative planner with simulated and real world experiments on multiple interactive navigation scenarios.

141756
17450
05/12/2017

Multi-robot path planning with maintenance of generalized connectivity

Y.SOLANA, M.FURCI, J.CORTES, A.FRANCHI

RIS

Manifestation avec acte : International Symposium on Multi-Robot and Multi-Agent Systems ( MRS ) 2017 du 04 décembre au 05 décembre 2017, Los Angeles (USA), Décembre 2017, 8p. , N° 17450

Lien : https://hal.laas.fr/hal-01658557

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Abstract

This paper addresses the problem of generating a path for a fleet of robots navigating in a cluttered environment, while maintaining the so called generalized connectivity. The main challenge in the management of a group of robots is to ensure the coordination between them, taking into account limitations in communication range and sensors, possible obstacles, inter-robot avoidance and other constraints. The Generalized Connectivity Maintenance (GCM) theory already provides a way to represent and consider the aforementioned constraints, but previous works only find solutions via locally-steering functions that do not provide global and optimal solutions. In this work, we merge the GCM theory with randomized path-planning approaches, and local path optimization techniques to derive a tool that can provide global, good-quality paths. The proposed approach has been intensively tested and verified by mean of numerical simulations.

141753
17485
01/12/2017

Smooth cubic polynomial trajectories for human-robot interactions

D.SIDOBRE, K.DESORMEAUX

RIS

Rapport LAAS N°17485, Décembre 2017

Lien : https://hal.laas.fr/hal-01672043

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Abstract

Avec l'importance croissante de l'interaction humain-robot (HRI), le mouvement des robots nécessite de plus en plus d'attention pour résoudre les problèmes liés à la sécurité, l'efficacité et l'ergonomie. Les trajectoires définissent une excellente solution pour la réalisation de mouvements destinés à des robots collaboratifs, car ils permettent de décrire simplement et précisément les mouvements. Malgré la grande quantité de travaux disponibles sur la génération de trajectoires en ligne (OTG), il n'y avait pas, à notre connaissance, de solution complète capable de répondre simultanément à toutes les exigences de ces nouvelles applications. Dans cet article, nous présentons le premier algorithme complet de génération de trajectoire qui construit des trajectoires à partir de conditions initiales et finales arbitraires, soumises à des limites asymétriques générales sur le jerk, l'accélération et la vitesse. Une revue de l'état de l'art expose les limites des travaux OTG précédents et révèle le problème difficile de la non-linéarité liée aux mouvements courts. Nous expliquons comment ces non-linéarités introduisent des discontinuités et proposons une solution basée sur des séquences de segments de fonctions polynomiales du troisième degré.

142076
17475
01/12/2017

Structural characterization of highly flexible proteins by small-angle scattering.

T.CORDEIRO, F.HERRANZ TRILLO, A.URBANEK, A.ESTANA, J.CORTES, N.SIBILLE, P.BERNADO

CBS, RIS

Revue Scientifique : Advances in Experimental Medicine and Biology, pp.107-129, Décembre 2017 , N° 17475

Lien : https://hal.laas.fr/hal-01664316

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Abstract

Intrinsically Disordered Proteins (IDPs) are fundamental actors of biological processes. Their inherent plasticity facilitates very specialized tasks in cell regulation and signalling, and their malfunction is linked to severe pathologies. Understanding the functional role of disorder requires the structural characterization of IDPs and the complexes they form. Small-angle Scattering of X-rays (SAXS) and Neutrons (SANS) have notably contributed to this structural understanding. In this review we summarize the most relevant developments in the field of SAS studies of disordered proteins. Emphasis is given to ensemble methods and how SAS data can be combined with computational approaches or other biophysical information such as NMR. The unique capabilities of SAS enable its application to extremely challenging disordered systems such as low-complexity regions, amyloidogenic proteins and transient biomolecular complexes. This reinforces the fundamental role of SAS in the structural and dynamic characterization of this elusive family of proteins.

141980
17370
16/10/2017

Fundamental actuation properties of multi-rotors: force-moment decoupling and fail-safe robustness

G.MICHIELETTO, M.RYLL, A.FRANCHI

RIS

Rapport LAAS N°17370, Octobre 2017, 14p.

Lien : https://hal.laas.fr/hal-01612602

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Abstract

In this paper we shed light on the fundamental actuation capabilities of multi-rotors, such as force-moment decoupling and ability to robustly fly still in place after the loss of propellers. These two actuation properties are formalized through the definition of some necessary algebraic conditions on the control force and control moment input matrices of generically tilted multi-rotors. Standard quadrotors are not able to robustly fly still at a constant spot after the loss of a propeller. The increased number of actuators of a hexarotor does not always help to overcome this limitation. To deeply understand this counterintuitive result, we apply the developed theory on the analysis of fail-safe robustness of hexarotor platforms, and clarify the role of the tilt angles and locations of the propellers in the vehicle. We show that standard star-shaped hexarotors are unable of robust static hovering after a propeller failure, while both the tilted star-shaped hexarotor and the Y-shaped hexarotor possess this important property. The analysis is validated with both simulation and experimental results testing the control of six-rotor vehicles subject to rotor loss.

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17482
21/09/2017

Landing and Take-off on/from Sloped and Non-planar Surfaces with more than 50 Degrees of Inclination

M.TOGNON, A.FRANCHI

RIS

Manifestation avec acte : International Micro Air Vehicle Conference and Flight Competition ( IMAV ) 2017 du 18 septembre au 21 septembre 2017, Toulouse (France), Septembre 2017, 6p. , N° 17482

Lien : https://hal.laas.fr/hal-01673466

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Abstract

This technical paper summarizes the recent experimental results concerning the challenging problem of landing and takeoff on/from a sloped surface with an aerial vehicle exploiting the force provided by an anchored taut tether. A special regard is given to the practical aspects concerning the experimental part. In this manuscript we show extreme landing and takeoff maneuvers on slopes with at least 50deg inclination and non flat surfaces, such as, e.g., on industrial pipes.

142063
17339
13/09/2017

A model-checking approach to analyse temporal failure propagation with AltaRica

A.ALBORE, S.DAL ZILIO, G.INFANTES, C.SEGUIN, P.VIRELIZIER

VERTICS, RIS, ONERA, IRT

Manifestation avec acte : International Symposium on Model-Based Safety and Assessment ( IMBSA ) 2017 du 11 septembre au 13 septembre 2017, Trento (Italie), Septembre 2017, 15p. , N° 17339

Lien : https://hal.archives-ouvertes.fr/hal-01590416

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Abstract

The design of complex safety critical systems raises new technical challenges for the industry. As systems become more complex—and include more and more interacting functions—it becomes harder to evaluate the safety implications of local failures and their possible propagation through a whole system. That is all the more true when we add time to the problem, that is when we consider the impact of computation times and delays on the propagation of failures. We describe an approach that extends models developed for Safety Analysis with timing information and provide tools to reason on the correctness of temporal safety conditions. Our approach is based on an extension of the AltaRica language where we can associate timing constraints with events and relies on a translation into a realtime model-checking toolset. We illustrate our method with an example that is representative of safety architectures found in critical systems.

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17257
06/09/2017

Reactive Dubins traveling salesman problem for replanning of information gathering by UAVs

R.PENICKA, M.SASKA, C.REYMANN, S.LACROIX

CTU, RIS

Manifestation avec acte : European Conference on Mobile Robots ( ECMR ) 2017 du 06 septembre au 08 septembre 2017, Paris (France), Septembre 2017, 6p. , N° 17257

Lien : https://hal.archives-ouvertes.fr/hal-01562527

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Abstract

We introduce a novel online replanning method for robotic information gathering by Unmanned Aerial Vehicles (UAVs) called Reactive Dubins Traveling Salesman Problem (RDTSP). The considered task is the following: a set of target locations are to be visited by the robot. From an initial information gathering plan, obtained as an offline solution of either the Dubins Traveling Salesman Problem (DTSP) or the Coverage Path Planning (CPP), the proposed RDTSP ensures robust information gathering in each given target location by replanning over possible missed target locations. Furthermore, a simple decision making is a part of the proposed RDTSP to determine which target locations are marked as missed and also to control the appropriate time instant at which the repair plan is inserted into the initial path. The proposed method for replanning is based on the Variable Neighborhood Search metaheuristic which ensures visiting of all possibly missed target locations by minimizing the length of the repair plan and by utilizing the preplanned offline solution of the particular information gathering task. The novel method is evaluated in a realistic outdoor robotic information gathering experiment with UAV for both the Dubins Traveling Salesman Problem and the Coverage Path Planning scenarios.

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17225
05/09/2017

Reconstruction d'images hyperspectrales à faible coût pour un imageur pilotable à double dispersion

I.ARDI, H.CARFANTAN, S.LACROIX, A.MONMAYRANT

PHOTO, IRAP, RIS

Manifestation avec acte : Colloque GRETSI sur le traitement du signal et des images ( GRETSI ) 2017 du 05 septembre au 08 septembre 2017, Juan les pins (France), Septembre 2017, 4p. , N° 17225

Lien : https://hal.archives-ouvertes.fr/hal-01562530

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Résumé

Nous nous intéressons à la reconstruction d'images hyperspectrales (HS) à partir d'un nouveau dispositif d'imagerie pilotable. La reconstruction de l'image à partir d'un faible nombre d'acquisitions pour des configurations différentes de l'imageur permet d'éviter l'acquisition de toute l'image HS par balayage. Notre objectif à terme est de rendre ce dispositif adaptatif en fonction de l'objet observé, ce qui nécessite de disposer de méthodes de reconstruction à faible coût calculatoire. Nous nous focalisons ici sur la reconstruction à l'aide de méthodes de pénalisation quadratique, permettant une résolution directe à faible coût, grâce au caractère très creux des matrices. Abstract – We consisder the problem of hyperspectral image reconstruction with a new controlable imaging system. The reconstruction with a small number of images acquired with different configurations of the imager avoids a complete scanning of the hyperspectral cube. Our objective is to exploit this imager along an adaptive scheme, which requires the ability to reconstruct images in near real-time. We focus here on a quadratic penalty reconstruction approach, which provides a fast direct resolution thanks to the high sparsity of the involved matrices.

140495
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