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17038
29/05/2017

Control of statically hoverable multi-rotor aerial vehicles and application to rotor-failure robustness for hexarotors

G.MICHIELETTO, M.RYLL, A.FRANCHI

RIS

Manifestation avec acte : IEEE International Conference on Robotics and Automation ( ICRA ) 2017 du 29 mai au 03 juin 2017, Singapour (Singapour), Mai 2017, 6p. , N° 17038

Lien : https://hal.laas.fr/hal-01476816

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Abstract

Standard hexarotors are often mistakenly considered 'by definition' fail-safe multi-rotor platforms because of the two additional propellers when compared to quadrotors. However this is not true, in fact, a standard hexarotor cannot statically hover with 'only' five propellers. In this paper we provide a set of new general algebraic conditions to ensure static hover for any multi-rotor platform with any number of generically oriented rotors. These are elegantly formulated as the full-rankness of the control moment input matrix, and the non-orthogonality between its null-space and the row space of the control force input matrix. Input saturations and safety margins are also taken into account with an additional condition on the null-space of control moment input matrix. A deep analysis on the hoverability properties is then carried out focusing on the propeller loss in a hexarotor platform. Leveraging our general results we explain why a standard hexarotor is not robust and how it can be made robust thanks to a particular tilt of the rotors. We finally propose a novel cascaded controller based on a preferential direction in the null-space of the control moment input matrix for the large class of statically hoverable multi-rotors, which goes far beyond standard platforms, and we apply this controller to the case of failed tilted hexarotor.

139273
17036
29/05/2017

6D physical interaction with a fully actuated aerial robot

M.RYLL, G.MUSCIO, F.PIERRI, E.CATALDI, G.ANTONELLI, F.CACCAVALE, A.FRANCHI

RIS, University of Basilicata, UNICAS

Manifestation avec acte : IEEE International Conference on Robotics and Automation ( ICRA ) 2017 du 29 mai au 03 juin 2017, Singapour (Singapour), Mai 2017, 6p. , N° 17036

Lien : https://hal.laas.fr/hal-01476814

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This paper presents the design, control, and experimental validation of a novel fully–actuated aerial robot for physically interactive tasks, named Tilt-Hex. We show how the Tilt-Hex, a tilted-propeller hexarotor, is able to control the full pose (position and orientation independently) using a geometric control, and to exert a full-wrench (force and torque independently) with a rigidly attached end-effector using an admittance control paradigm. An outer loop control governs the desired admittance behavior and an inner loop based on geometric control ensures pose tracking. The interaction forces are estimated by a momentum based observer. Control and observation are made possible by a precise control and measurement of the speed of each propeller. An extensive experimental campaign shows that the Tilt-Hex is able to outperform the classical underactuated multi-rotors in terms of stability, accuracy and dexterity and represents one of the best choice at date for tasks requiring aerial physical interaction.

139259
17037
29/05/2017

Towards robotic MAGMaS: multiple aerial-ground manipulator systems

N.STAUB, M.MOHAMMADI, D.BICEGO, D.PRATTICHIZZO, A.FRANCHI

RIS, IIT, Genova

Manifestation avec acte : IEEE International Conference on Robotics and Automation ( ICRA ) 2017 du 29 mai au 03 juin 2017, Singapour (Singapour), Mai 2017, 6p. , N° 17037

Lien : https://hal.laas.fr/hal-01476813

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In this paper we lay the foundation of the first heterogeneous multi-robot system of the Multiple Aerial-Ground Manipulator System (MAGMaS) type. A MAGMaS consists of a ground manipulator and a team of aerial robots equipped with a simple gripper manipulator the same object. The idea is to benefit from the advantages of both kinds of platforms, i.e., physical strength versus large workspace. The dynamic model of such robotic systems is derived, and its characteristic structure exhibited. Based on the dynamical structure of the system a nonlinear control scheme, augmented with a disturbance observer is proposed to perform trajectory tracking tasks in presence of model inaccuracies and external disturbances. The system redundancy is exploited by solving an optimal force/torque allocation problem that takes into account the heterogeneous system constraints and maximizes the force manipulability ellipsoid. Simulation results validated the proposed control scheme for this novel heterogeneous robotic system. We finally present a prototypical mechanical design and preliminary experimental evaluation of a MAGMaS composed by a kuka LWR4 and quadrotor based aerial robot.

139261
17039
29/05/2017

Dynamic decentralized control for protocentric aerial manipulators

M.TOGNON, B.YUKSEL, G.BUONDONNO, A.FRANCHI

RIS, MPI, Rome

Manifestation avec acte : IEEE International Conference on Robotics and Automation ( ICRA ) 2017 du 29 mai au 03 juin 2017, Singapour (Singapour), Mai 2017, 6p. , N° 17039

Lien : https://hal.laas.fr/hal-01476817

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We present a control methodology for underactuated aerial manipulators that is both easy to implement on real systems and able to achieve highly dynamic behaviors. The method is composed by two parts: i) a nominal input/state trajectory generator that takes into account the full-body dynamics of the system exploiting its differential flatness property; ii) a decentralized feedback controller acting on the actuated degrees of freedom that confers the needed robustness to the closed-loop system. We demonstrate that the proposed controller is able to precisely track dynamic trajectories when implemented on a standard hardware. Comparative experiments clearly show the benefit of using the nominal input/state generator.

139275
17052
01/05/2017

Adaptive synthesis of dynamically feasible full-body movements for the humanoid robot HRP-2 by flexible combination of learned dynamic movement primitives

A.MUKOVSKIY, C.VASSALLO, M.NAVEAU, O.STASSE, P.SOUERES, M.GIESE

Tubingen, GEPETTO

Revue Scientifique : Robotics and Autonomous Systems, Vol.91, pp.270-283, Mai 2017 , N° 17052

Lien : https://hal.archives-ouvertes.fr/hal-01484935

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Abstract

Skilled human full-body movements are often planned in a highly predictive manner. For example, during walking while reaching towards a goal object results in steps and body postures are adapted to the goal position already multiple steps before the goal contact. The realization of such highly predictive behaviors for humanoid robots is a challenge because standard approaches, such as optimal control, result in computation times that are prohibitive for the predictive control of complex coordinated full-body movements over multiple steps. We devised a new architecture that combines the online-planning of complex coordinated full-body movements, based on the flexible combination of learned dynamic movement primitives, with a Walking Pattern Generator (WPG), based on Model Predictive Control (MPC), which generates dynamically feasible locomotion of the humanoid robot HRP-2. A dynamic filter corrects the Zero Moment Point (ZMP) trajectories in order to guarantee the dynamic feasibility of the executed behavior taking into account the upper-body movements, at the same time ensuring an accurate approximation of the planned motion trajectories. We demonstrate the high flexibility of the chosen movement planning approach, and the accuracy and feasibility of the generated motion. In addition, we show that a na¨ıvena¨ıve approach, which generates adaptive motion by using machine learning methods by the interpolation between feasible training motion examples fails to guarantee the stability and dynamic feasibility of the generated behaviors.

139327
17055
22/03/2017

TALOS: A new humanoid research platform targeted for industrial applications

O.STASSE, T.FLAYOLS, R.BUDHIRAJA, K.GIRAUD ESCLASSE, J.CARPENTIER, A.DEL PRETE, P.SOUERES, N.MANSARD, F.LAMIRAUX, J.P.LAUMOND, L.MARCHIONNI, H.TOME, F.FERRO

GEPETTO, Pal Robotics

Rapport LAAS N°17055, Mars 2017, 8p.

Lien : https://hal.archives-ouvertes.fr/hal-01485519

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Abstract

The upcoming generation of humanoid robots will have to be equipped with state-of-the-art technical features along with high industrial quality, but they should also offer the prospect of effective physical human interaction. In this paper we introduce a new humanoid robot capable of interacting with a human environment and targeting a whole range of industrial applications. This robot is able to handle weights of 6 Kg with an outstretched arm, and has powerful motors to carry out movements unavailable in previous generations of humanoid robots. Its kinematics has been specially designed for screwing and drilling motions. In order to make interaction possible with human operators, this robot is equipped with torque sensors to measure joint effort and high resolution encoders to measure both motor and joint positions. The humanoid robotics field has reached a stage where robustness and repeatibility is the next watershed. We believe that, this robot has the potential to become a powerful tool for the research community to successfully navigate this turning point, as the humanoid robot HRP-2 was in its own time.

139336
17054
22/03/2017

A Kinodynamic steering-method for legged multi-contact locomotion

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

GEPETTO

Rapport LAAS N°17054, Mars 2017, 7p.

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

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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.

139335
17049
21/03/2017

Optimal design of compliant walkers

G.BUONDONNO, J.CARPENTIER, G.SAUREL, N.MANSARD, A.DE LUCA, J.P.LAUMOND

Rome, GEPETTO, Univ of Cambridge

Rapport LAAS N°17049, Mars 2017, 7p.

Lien : https://hal.archives-ouvertes.fr/hal-01483567

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We present an optimization framework for the design and analysis of underactuated biped walkers, characterized by passive or actuated joints with rigid or non-negligible elastic actuation/transmission elements. The framework is based on optimal control, dealing with geometric constraints and various dynamic objective functions, as well as boundary conditions, which helps in selecting optimal values both for the actuation and the transmission parameters. Solutions of the formulated problems are shown for different kinds of bipedal architectures, and comparisons drawn between traditional rigid robots and compliant ones show the energy-efficiency of compliant actuators in the context of locomotion.

139321
17048
21/03/2017

Explicit computations, simulations and additional results for the dynamic decentralized control for protocentric aerial manipulators

M.TOGNON, B.YUKSEL, G.BUONDONNO, A.FRANCHI

RIS, MPI, Rome

Rapport LAAS N°17048, Mars 2017, 5p.

Lien : https://hal.archives-ouvertes.fr/hal-01474695

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This document is a technical attachment to ”Dynamic Decentralized Control for Protocentric Aerial Manipulators” for explicit computations of the nominal states and the inputs of a Pro- tocentric Aerial Manipulator (PAM) in 2D, using differential flatness property. In ”Dynamic Decentralized Control for Protocentric Aerial Manipulators” these values are used to control a PAM in 3D. Furthermore, considering the aerial manipulator design used for the experiments in that paper, here we inves- tigate the case when the system is non-protocentric; i.e., the manipulating arm is not exactly attached to the CoM of the flying robot, P0 . We show the effect of the distance between this attachment point and P0 on the performance tracking a composite trajectory. Finally some additional plots related to the experimental results are provided.

139312
17050
21/03/2017

Dynamics, control, and estimation for aerial robots tethered by cables or bars

M.TOGNON, A.FRANCHI

RIS

Rapport LAAS N°17050, Mars 2017, 12p.

Lien : https://hal.archives-ouvertes.fr/hal-01483524

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Abstract

We consider the problem of controlling an aerial robot connected to the ground by a passive cable or a passive rigid link. We provide a thorough characterization of this nonlinear dynamical robotic system in terms of fundamental properties such as differential flatness, controllability, and observability. We prove that the robotic system is differentially flat with respect to two output pairs: elevation of the link and attitude of the vehicle; elevation of the link and longitudinal link force (e.g., cable tension, or bar compression). We show the design of an almost globally convergent nonlinear observer of the full state that resorts only to an onboard accelerometer and a gyroscope. We also design two almost globally convergent nonlinear controllers to track any sufficiently smooth time-varying trajectory of the two output pairs. Finally we numerically test the robustness of the proposed method in several far-from-nominal conditions: nonlinear cross-coupling effects, parameter deviations, measurements noise and non ideal actuators.

139322
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