Laboratoire d’analyse et d’architecture des systèmes
Y.AOUSTIN, C.CHEVALLEREAU, J.P.LAUMOND
Ouvrage (contribution) : Humanoid Robotics: A Reference, Springer, N°ISBN 978-94-007-6045-5, Octobre 2018 , N° 18021
F.FORGET, K.GIRAUD ESCLASSE, R.GELIN, N.MANSARD, O.STASSE
Manifestation avec acte : International Conference on Informatics in Control, Automation and Robotics ( ICINCO ) 2018 du 29 juillet au 31 juillet 2018, Porto (Portugal), Juillet 2018, 8p. , N° 17069
Autonomous robots such as legged robots and mobile manipulators imply new challenges in the design and the control of their actuators. In particular, it is desirable that the actuators are back-drivable, efficient (low friction) and compact. In this paper, we report the complete implementation of an advanced actuator based on screw, nut and cable. This actuator has been chosen for the humanoid robot Romeo. A similar model of the actuator has been used to control the humanoid robot Valkyrie. We expose the design of this actuator and present its Lagrangian model. The actuator being flexible, we propose a two-layer optimal control solver based on Differential Dynamical Programming. The actuator design, model identification and control is validated on a full actuator mounted in a work bench. The results show that this type of actuation is very suitable for legged robots and is a good candidate to replace strain wave gears.
F.BAILLY, E.POUYDEBAT, B.WATIER, V.BELS, P.SOUERES
GEPETTO, MECADEV, ISYEB
Manifestation avec acte : International Conference on Biomimetic and Biohybrid Systems ( Living Machines ) 2018 du 17 juillet au 20 juillet 2018, Paris (France), Juillet 2018, 12p. , N° 18135
This paper presents an interdisciplinary study of the role of the head in multisensory integration and motor-control organization for the production of voluntary spatial actions. It combines elements from biology and engineering. First, morphological and behavioral characteristics of animals able to perform voluntary spatial actions through evolution are examined. The complexity of state-space representation and observation of multi-joint mobile robots is then described in the context of automatic control, and perception-related characteristics brought by the presence of a head are presented from the perspective of signal processing. Finally, the role of the head in locomotion and manipulation for animals and robots is discussed, paving the way for future robot design.
M.TOGNON, E.CATALDI, H.TELLO CHAVEZ, G.ANTONELLI, J.CORTES, A.FRANCHI
Revue Scientifique : IEEE Robotics and Automation Letters, Vol.3, N°3, pp.2478-2484, Juillet 2018, DOI 10.1109/LRA.2018.2803206 , N° 18033
This paper presents a new method to address the problem of task-constrained motion planning for aerial manipulators. We propose a control-aware planner based on the paradigm of tight coupling between planning and control. Such paradigm is especially useful in aerial manipulation, where the separation between planning and control is not advisable. The proposed sampling based motion planner uses a controller composed of a second-order inverse kinematics algorithm and a dynamic tracker, as a local planner, thus allowing a more natural consideration of the closed-loop system dynamics. For task constrained motions, this method lets to i) sample directly in the reduced and more relevant task space, ii) predict the behavior of the controller avoiding motions that bring to singularities or large tracking errors, and iii) guarantee the correct execution of the maneuver. The method is tested in simulation for a multidirectional-thrust vehicle endowed with a two-DoF manipulator. The proposed approach is very general, and could be applied to ground and underwater robotic systems to perform manipulation or inspection tasks.
M.TOGNON, C.GABELLIERI, L.PALLOTTINO, A.FRANCHI
Revue Scientifique : IEEE Robotics and Automation Letters, Vol.3, N°3, pp.2577-2583, Juillet 2018 , N° 17220
This paper considers the study of cooperative transportation of a cable-suspended load with two aerial robots and without explicit communication. The role of the internal force for the asymptotic stability of the beam-position/beam-attitude equilibria is analyzed in depth and explained thoroughly. Using a nonlinear Lyapunov-based approach, we prove that that if a non-zero internal force is chosen then asymptotic stabilization of any desired beam-position/beam-attitude configuration can be achieved by using a decentralized and communication-less master-slave admittance controller. If, conversely , a zero internal force is chosen, as done in the majority of the state-of-the-art algorithms, the attitude of the beam is not controllable without communication. Non-zero internal force can be interpreted then as a fundamental factor that enables the use of cables as implicit communication means between the two aerial vehicles in replacement of the explicit ones. The theoretical findings are validated through numerical simulations with added noise and realistic uncertainty.
Revue Scientifique : IEEE Robotics and Automation Letters, Vol.3, N°3, pp.2277-2282, Juillet 2018, doi 10.1109/LRA.2018.2802544 , N° 18034
This paper presents a theoretical study on omni-directional aerial vehicles with body-frame fixed unidirectional thrusters. Omniplus multi-rotor designs are defined as the ones that allow to exert a total wrench in any direction using positive-only lift force and drag moment (i.e., positive rotational speed) for each rotor blade. Algebraic conditions for a design to be omniplus are derived, a simple necessary condition being the fact that at least seven propellers have to be used. An energy optimal design strategy is then defined as the one minimizing the maximum norm of the input set needed to span a certain wrench ellipsoid for the adopted input allocation strategy. Two corresponding major design criteria are then introduced: firstly, a minimum allocation-matrix condition number aims at an equal sharing of the effort needed to generate wrenches in any direction; secondly, imposing a balanced design guarantees an equal sharing of the extra effort needed to keep the input in the non-negative orthant. We propose a numerical algorithm to solve such optimal design problem and a control algorithm to control any omnidirectional platform. The work is concluded with informative simulation results in non-ideal conditions.
A.BIT-MONNOT, R.BAILON-RUIZ, S.LACROIX
Manifestation avec acte : International Conference on Automated Planning and Scheduling ( ICAPS ) 2018 du 24 juin au 29 juin 2018, Delft (Pays-Bas), Juin 2018, 9p. , N° 18084
Observation planning for Unmanned Aerial Vehicles (UAVs) is a challenging task as it requires planning trajectories over a large continuous space and with motion models that can not be directly encoded into current planners. Furthermore, realistic problems often require complex objective functions that complicate problem decomposition. In this paper, we propose a local search approach to plan the trajectories of a fleet of UAVs on an observation mission. The strength of the approach lies in its loose coupling with domain specific requirements such as the UAV model or the objective function that are both used as black boxes. Furthermore, the Variable Neighborhood Search (VNS) procedure considered facilitates the adaptation of the algorithm to specific requirements through the addition of new neighborhoods. We demonstrate the feasibility and convenience of the method on a large joint observation task in which a fleet of fixed-wing UAVs maps wildfires over areas of a hundred square kilometers. The approach allows generating plans over tens of minutes for a handful of UAVs in matter of seconds, even when considering very short primitive maneuvers.
Manifestation avec acte : Robotics Science and Systems ( RSS ) 2018 du 26 juin au 30 juin 2018, Pittsburg (USA), Juin 2018, 9p. , N° 18138
This paper deals with manipulation planning. The problem consists in automatically computing paths for a system composed of one or several robots, with one or several grippers and one or several objects that can be grasped and moved by the robots. The problem gives rise to constraints that can be either explicit – an object is in a gripper – or implicit – an object is hold by two different grippers. This paper proposes an algorithm that handles such sets of constraints and solves them in an explicit way as much as possible. When all constraints cannot be made explicit, substitution is operated between variables to make the resulting implicit constraint with as few variables as possible. The manipulation planning problem is modelled as a constraint graph that stores all the constraints of the problem.
Ouvrage (contribution) : Humanoid Robotics: A Reference, Springer, N°ISBN 978-94-007-6047-9, Juin 2018, 22p. , N° 18003
G.MICHIELETTO, M.RYLL, A.FRANCHI
Revue Scientifique : IEEE Transactions on Robotics, Vol.34, N°3, pp.702-715, Juin 2018 , N° 17370
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.