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534documents trouvés

16242
01/01/2018

Joint position and velocity bounds in discrete-time acceleration/torque control of robot manipulators

A.DEL PRETE

GEPETTO

Revue Scientifique : IEEE Robotics and Automation Letters, Vol.3, N°1, pp.281-288, Janvier 2018, DOI: 10.1109/LRA.2017.2738321 , N° 16242

Lien : https://hal.archives-ouvertes.fr/hal-01356989

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Abstract

This letter deals with the problem of controlling a robotic system whose joints have bounded position, velocity, and acceleration/torque. Assuming a discrete-time acceleration control, we compute tight bounds on the current joint accelerations that ensure the existence of a feasible trajectory in the future. Despite the clear practical importance of this issue, no complete and exact solution has been proposed yet, and all existing control architectures rely on hand-tuned heuristics. We also extend this methodology to torque-controlled robots, for which joint accelerations are only indirectly bounded by the torque limits. Numerical simulations are presented to validate the proposed method, which is computationally efficient and hence suitable for high-frequency control.

140657
17095
28/09/2017

Online payload identification for quadruped robots

G.TOURNOIS, M.FIOCCHI, A.DEL PRETE, R.ORSOLINO, D.G.CALDWELL, C.SEMINI

IIT, Genova, GEPETTO

Manifestation avec acte : IEEE/RSJ International Conference on Intelligent Robots and Systems ( IROS ) 2017 du 24 septembre au 28 septembre 2017, Vancouver (Canada), Septembre 2017, 8p. , N° 17095

Lien : https://hal.laas.fr/hal-01575033

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Abstract

The identification of inertial parameters is crucial to achieve high-performance model-based control of legged robots. The inertial parameters of the legs are typically not altered during expeditions and therefore are best identified offline. On the other hand, the trunk parameters depend on the modules mounted on the robot, like a motor to provide the hydraulic power, or different sets of cameras for perception. This motivates the use of recursive approaches to identify online mass and the position of the Center of Mass (CoM) of the robot trunk, when a payload change occurs. We propose two such approaches and analyze their robustness in simulation. Furthermore, experimental trials on our 80-kg quadruped robot HyQ show the applicability of our strategies during locomotion to cope with large payload changes that would otherwise severely compromise the balance of the robot.

140693
17054
24/09/2017

A Kinodynamic steering-method for legged multi-contact locomotion

P.FERNBACH, S.TONNEAU, A.DEL PRETE, M.TAIX

GEPETTO

Manifestation avec acte : IEEE/RSJ International Conference on Intelligent Robots and Systems ( IROS ) 2017 du 24 septembre au 28 septembre 2017, Vancouver (Canada), Septembre 2017, 7p. , N° 17054

Lien : https://hal.laas.fr/hal-01486933

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Abstract

We present a novel method for synthesizing collision-free, dynamic locomotion behaviors for legged robots, including jumping, going down a very steep slope, or recovering from a push using the arms of the robot. The approach is automatic and generic: non-gaited motions, comprising arbitrary contact postures can be generated along any environment. At the core of our framework is a new steering method that generates trajectories connecting two states of the robot. These trajectories account for the state-dependent, centroidal dynamic constraints inherent to legged robots. The method, of low dimension, formulated as a Linear Program, is really efficient to compute, and can find an application in various problems related to legged locomotion. By incorporating this steering method into an existing sampling-based contact planner, we propose the first kinodynamic contact planner for legged robots.

140189
17313
21/09/2017

Modification of the spontaneous seat-to-stand transition in cycling with bodyweight and cadence variations

B.WATIER, A.COSTES, N.TURPIN

GEPETTO, Toulouse III, CRIR

Rapport LAAS N°17313, doi 10.1016/j.jbiomech.2017.08.003, Septembre 2017

Lien : https://hal.laas.fr/hal-01584024

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Abstract

When a high power output is required in cycling, a spontaneous transition by the cyclist from a seated to a standing position generally occurs. In this study, by varying the cadence and cyclist bodyweight, we tested whether the transition is better explained by the greater power economy of a standing position or by the emergence of mechanical constraints that force cyclists to stand. Ten males participated in five experimental sessions corresponding to different bodyweights (80%, 100%, or 120%) and cadences (50 RPM, 70 RPM, or 90 RPM). In each session, we first determined the seat-to-stand transition power (SSTP) in an incremental test. The participants then cycled at 20%, 40%, 60%, 80%, 100%, or 120% of the SSTP in the seated and standing positions, for which we recorded the saddle forces and electromyogram (EMG) signals of eight lower limb muscles. We estimated the cycling cost using an EMG cost function (ECF) and the minimal saddle forces in the seated position as an indicator of the mechanical constraints. Our results show the SSTP to vary with respect to both cadence and bodyweight. The ECF was lower in the standing position above the SSTP value (i.e., at 120%) in all experimental sessions. The minimal saddle forces varied significantly with respect to both cadence and bodyweight. These results suggest that optimization of the muscular cost function, rather than mechanical constraints, explain the seat-to-stand transition in cycling.

140919
17277
06/09/2017

Experimental evaluation of simple estimators for humanoid robots

T.FLAYOLS, A.DEL PRETE, P.WENSING, A.MIFSUD, M.BENALLEGUE, O.STASSE

GEPETTO, UND, AIST

Rapport LAAS N°17277, Septembre 2017, 7p.

Lien : https://hal.archives-ouvertes.fr/hal-01574819

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Abstract

This paper introduces and evaluates a family of new simple estimators to reconstruct the pose and velocity of the floating base. The estimation of the floating-base state is a critical challenge to whole-body control methods that rely on full-state information in high-rate feedback. Although the kinematics of grounded limbs may be used to estimate the pose and velocity of the body, modelling errors from ground irregularity, foot slip, and structural flexibilities limit the utility of estimation from kinematics alone. These difficulties have motivated the development of sensor fusion methods to augment body-mounted IMUs with kinematic measurements. Existing methods often rely on extended Kalman filtering, which lack convergence guarantees and may present difficulties in tuning. This paper proposes two new simplifications to the floating-base state estimation problem that make use of robust off-the-shelf orientation estimators to bootstrap development. Experiments for in-place balance and walking with the HRP-2 show that the simplifications yield results on par with the accuracy reported in the literature for other methods. As further benefits, the structure of the proposed estimators prevents divergence of the estimates, simplifies tuning, and admits efficient computation. These benefits are envisioned to help accelerate the development of baseline estimators in future humanoids.

140663
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.

140732
17270
06/09/2017

Viewing robot navigation in human environment as a cooperative activity

H.KHAMBHAITA, R.ALAMI

RIS

Rapport LAAS N°17270, Septembre 2017, 18p.

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.

140650
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
17249
04/09/2017

A human-inspired mechanical criterion for multi-contact locomotion in humanoids

F.BAILLY, J.CARPENTIER, B.PINET, P.SOUERES, B.WATIER

GEPETTO

Rapport LAAS N°17249, Septembre 2017, 7p.

Lien : https://hal.laas.fr/hal-01569252

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Abstract

This work aims at experimentally identifying a mechanical principle of locomotion stability in humans and demonstrating that this principle can be used for generating stable multi-contact motions for humanoids. For this purpose, a destabilizing setup was built on which five different experiments were carried out by 15 human volunteers. We first show experimentally that when humans balance is perturbed (walking on a destabilizing setup, increasing walking speed, grasping or not a fixed element), the distance between the center of mass (CoM) and the central axis of the external contact wrench significantly increases. This result is coupled with a theoretical reasoning in mechanics in order to exhibit how lowering this distance amounts to lower the body's angular acceleration and thus constitutes a good strategy against falling. Finally, we illustrate the interest of this result for humanoid robot motion generation by embedding the minimization of the distance between the CoM and the central axis of the external contact wrench in an optimal control formulation in order generate multi-contact locomotion.

140582
17253
01/09/2017

Assessing the social criteria for human-robot collaborative navigation: A comparison of human-aware navigation planners

H.KHAMBHAITA, R.ALAMI

RIS

Manifestation avec acte : IEEE International Symposium on Robot and Human Interactive Communication ( Ro-MAN ) 2017 du 28 août au 01 septembre 2017, Lisbonne (Portugal), Septembre 2017, 6p. , N° 17253

Lien : https://hal.laas.fr/hal-01568841

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Abstract

This paper focuses on requirements for effective human robot collaboration in interactive navigation scenarios. We designed several use-cases where humans and robot had to move in the same environment that resemble canonical path-crossing situations. These use-cases include open as well as constrained spaces. Three different state-of-the-art human-aware navigation planners were used for planning the robot paths during all selected use-cases. We compare results of simulation experiments with these human-aware planners in terms of quality of generated trajectories together with discussion on capabilities and limitations of the planners. The results show that the human-robot collaborative planner performs better in everyday path-crossing configurations. This suggests that the criteria used by the human-robot collaborative planner (safety, time-to-collision, directional-costs) are possible good measures for designing acceptable human-aware navigation planners. Consequently, we analyze the effects of these social criteria and draw perspectives on future evolution of human-aware navigation planning methods.

140601
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