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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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Abstract

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
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
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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Abstract

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
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
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
17111
27/04/2017

Nonlinear control of multi-rotor aerial vehicles based on the zero-moment direction

G.MICHIELETTO, A.CENEDESE, L.ZACCARIAN, A.FRANCHI

RIS, University of Padova, MAC

Rapport LAAS N°17111, Avril 2017, 6p.

Lien : https://hal.laas.fr/hal-01513229

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Abstract

A quaternion-based nonlinear control strategy is here presented to steer and keep a generic multi-rotor platform in a given reference position. Exploiting a state feedback structure, the proposed solution ensures the stabilization of the aerial vehicle so that its linear and angular velocity are zero and its attitude is constant. The main feature of the designed controller is the identification of a zero-moment direction in the feasible force space, i.e., a direction along which the control force intensity can be assigned independently of the control moment. The asymptotic convergence of the error dynamics is confirmed by simulation results on a hexarotor with tilted propellers.

139666
17107
26/04/2017

Position tracking control for an aerial robot passively tethered to an independently moving platform

M.TOGNON, A.FRANCHI

RIS

Rapport LAAS N°17107, Avril 2017, 7p.

Lien : https://hal.laas.fr/hal-01501919

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Abstract

We study the control problem of an aerial vehicle moving in the 3D space and connected to an independently moving platform through a physical link (e.g., a cable, a chain or a rope). The link is attached to the moving platform by means of a passive winch. The latter differs from an active winch by producing only a constant uncontrollable torque. We solve the problem of exact tracking of the 3D position of the aerial vehicle, either absolute or with respect to the moving platform, while the platform is independently moving. We prove two intrinsic properties of the system, namely, the dynamic feedback linearizability and the differential flatness with respect to the output of interest. Exploiting this properties we design a nonlinear controller able to exponentially steer the position of the aerial robot along any sufficiently smooth time-varying trajectory. The proposed method is tested through numerical simulations in several non-ideal cases.

139632
17106
25/04/2017

Visual Marker based Multi-Sensor Fusion State Estimation

J.L.SANCHEZ LOPEZ, V.ARELLANO, M.TOGNON, P.CAMPOY

UPM, RIS

Rapport LAAS N°17106, Avril 2017, 6p.

Lien : https://hal.laas.fr/hal-01501980

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This paper presents the description and experimental results of a versatile Visual Marker based Multi-Sensor Fusion State Estimation that allows to combine a variable optional number of sensors and positioning algorithms in a loosely-coupling fashion, incorporating visual markers to increase its performances. This technique allows an aerial robot to navigate in different environments and carrying out different missions with the same state estimation architecture, exploiting the best from every sensor. The state estimation algorithm has been successfully tested controlling a quadrotor equipped with an extra IMU and a RGB camera used only to detect visual markers. The entire framework runs on an onboard computer, including the controllers and the proposed state estimator. The whole software is made publicly available to the scientific community through an open source implementation.

139624
17069
03/04/2017

Differential dynamical programming to control a cable driven actuator for the humanoid robot Romeo

F.FORGET, K.GIRAUD ESCLASSE, R.GELIN, N.MANSARD, O.STASSE

GEPETTO, Aldebaran

Rapport LAAS N°17069, Avril 2017, 8p.

Lien : https://hal.archives-ouvertes.fr/hal-01494676

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Abstract

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.

139418
17070
03/04/2017

Regulation of the distance between the center of mass and the minimum moment axis for stabilized locomotion in humans

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

GEPETTO

Rapport LAAS N°17070, Avril 2017, 15p.

Lien : https://hal.laas.fr/hal-01494117

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Abstract

This study aims at showing that, to ensure stability, humans tend to minimize the distance between their center of mass and the minimal moment axis of contact forces. This work is based on a theoretical reasoning in mechanics and on experiments in human walking movement. A destabilizing setup was built on which five different experiments were carried out by 15 volunteers. We computed the distance between the minimal moment axis of the contact forces and the center of mass of the participants. This distance significantly increased (p < 0.001, ranging from 55.1 mm to 150.9 mm) as subjects balance was perturbed through the five different conditions (walking on a destabilizing setup, increasing walking speed, grasping or not a fixed element). Furthermore, the analysis of each segment's position with regard to the studied axis shows that heaviest segments are kept close to it, while lightest segments are less constrained around it (p < 0.001, from 145.7 mm to 493.1 mm). This might reveal a strategy used to obtain a fine control of the center of mass distance from the axis and thus a good regulation of the variation of whole body angular momentum. Tracking this distance could be used for different purposes, such as fall detection, prosthesis studies and trajectory generation in humanoid robotics.

139419
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