Dexterous manipulation of unknown objects using virtual contact points

The manipulation of unknown objects is a problem of special interest in robotics since it is not always possible to have exact models of the objects with which the robot interacts. This paper presents a simple strategy to manipulate unknown objects using a robotic hand equipped with tactile sensors. The hand configurations that allow the rotation of an unknown object are computed using only tactile and kinematic information, obtained during the manipulation process and reasoning about the desired and real positions of the fingertips during the manipulation. This is done taking into account that the desired positions of the fingertips are not physically reachable since they are located in the interior of the manipulated object and therefore they are virtual positions with associated virtual contact points. The proposed approach was satisfactorily validated using three fingers of an anthropomorphic robotic hand (Allegro Hand), with the original fingertips replaced by tactile sensors (WTS-FT). In the experimental validation, several everyday objects with different shapes were successfully manipulated, rotating them without the need of knowing their shape or any other physical property.Peer ReviewedPostprint (author's final draft

Improving grasping forces during the manipulation of unknown objects

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksMany of the solutions proposed for the object manipulation problem are based on the knowledge of the object features. The approach proposed in this paper intends to provide a simple geometrical approach to securely manipulate an unknown object based only on tactile and kinematic information. The tactile and kinematic data obtained during the manipulation is used to recognize the object shape (at least the local object curvature), allowing to improve the grasping forces when this information is added to the manipulation strategy. The approach has been fully implemented and tested using the Schunk Dexterous Hand (SDH2). Experimental results are shown to illustrate the efficiency of the approach.Peer ReviewedPostprint (author's final draft

Coordination of several robots based on temporal synchronization

© 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/This paper proposes an approach to deal with the problem of coordinating multi-robot systems, in which each robot executes individually planned tasks in a shared workspace. The approach is a decoupled method that can coordinate the participating robots in on-line mode. The coordination is achieved through the adjustment of the time evolution of each robot along its original planned geometric path according to the movements of the other robots to assure a collision-free execution of their respective tasks. To assess the proposed approach different tests were performed in graphical simulations and real experiments.Postprint (published version

Restrictive, split and unital quasi-Jordan algebras

AbstractIt is well known that by means of the right and left products of an associative dialgebra we can build a new product over the same vector space with respect to which it becomes a right version of a Jordan algebra (in fact, this new product is right commutative) called quasi-Jordan algebra. Recently, Kolesnikov and Bremner independently have discovered an interesting property of this new product. As the results of this paper indicate, when the said property is incorporated as an axiom in the definition of quasi-Jordan algebra then in a natural way one can introduce and study concepts in this new structure such as derivations (in particular inner derivations), quadratic representations, and the structure groups of a quasi-Jordan algebra

Planning manipulation movements of a dual-arm system considering obstacle removing

The paper deals with the problem of planning movements of two hand-arm robotic systems, considering the possibility of using the robot hands to remove potential obstacles in order to obtain a free access to grasp a desired object. The approach is based on a variation of a Probabilistic Road Map that does not rule out the samples implying collisions with removable objects but instead classifies them according to the collided obstacle(s), and allows the search of free paths with the indication of which objects must be removed from the work-space to make the path actually valid; we call it Probabilistic Road Map with Obstacles (PRMwO). The proposed system includes a task assignment system that distributes the task among the robots, using for that purpose a precedence graph built from the results of the PRMwO. The approach has been implemented for a real dual-arm robotic system, and some simulated and real running examples are presented in the paper. (C) 2014 Elsevier B.V. All rights reserved.Postprint (published version

Finite-volume matrix elements of two-body states

In this talk, we present a framework for studying structural information of resonances and bound states coupling to two-hadron scattering states. This makes use of a recently proposed finite-volume formalism to determine a class of observables that are experimentally inaccessible but can be accessed via lattice QCD. In particular, we shown that finite-volume two-body matrix elements with one current insertion can be directly related to scattering amplitudes coupling to the external current. For two-hadron systems with resonances or bound states, one can extract the corresponding form factors of these from the energy-dependence of the amplitudes.Comment: 7 pages, 2 figures, Proceedings of Lattice 201

Robust dexterous telemanipulation following object-orientation commands

This paper aims to present a procedure to change the orientation of a grasped object using dexterous manipulation. The manipulation is controlled by teleoperation in a very simple way, with the commands introduced by an operator using a keyboard. Design/methodology/approach - The paper shows a teleoperation scheme, hand kinematics and a manipulation strategy to manipulate different objects using the Schunk Dexterous Hand (SDH2). A state machine is used to model the teleoperation actions and the system states. A virtual link is used to include the contact point on the hand kinematics of the SDH2. Findings - Experiments were conducted to evaluate the proposed approach with different objects, varying the initial grasp configuration and the sequence of actions commanded by the operator. Originality/value - The proposed approach uses a shared telemanipulation schema to perform dexterous manipulation; in this schema, the operator sends high-level commands and a local system uses this information, jointly with tactile measurements and the current status of the system, to generate proper setpoints for the low-level control of the fingers, which may be a commercial close one. The main contribution of this work is the mentioned local system, simple enough for practical applications and robust enough to avoid object falls.Postprint (author's final draft

Manipulación diestra de objetos desconocidos usando puntos de contacto virtuales

En este trabajo se presenta una estrategia de manipulación que permite rotar objetos desconocidos usando una mano robótica equipada con sensores táctiles. Las configuraciones de la mano que permiten cambiar la posición del objeto se calculan usando la información táctil y cinemática que se obtiene mientras se manipula el objeto, y razonando en base a las posiciones deseadas y reales de las yemas de los dedos durante la manipulación, teniendo en cuenta que las primeras no son físicamente alcanzables al estar situadas en el interior del objeto y son por lo tanto posiciones virtuales que tienen asociados puntos de contacto virtuales. El enfoque propuesto fue probado exitosamente usando tres dedos de una mano robótica antropomorfa (Allegro Hand), cuyas puntas de los dedos han sido modificadas para incluir los sensores táctiles (WTS-FT). En la validación experimental se manipularon exitosamente varios objetos de uso cotidiano de diferentes formas, rotándolos satisfactoriamente sin necesidad de conocer su forma.Postprint (author's final draft

Herramienta para visualización gráfica de fuerzas de contacto y de movimientos de una mano robótica con sensores táctiles

En este trabajo se presenta una herramienta de software que permite la visualización gráfica de fuerzas de contacto de especial utilidad en prensiones usando manos robóticas. Las fuerzas visualizadas se generan debido al contacto entre las yemas de los dedos y el objeto manipulado, o debido a los pares aplicados en las articulaciones de los dedos. La herramienta también permite mover la mano real, ya sea especificando configuraciones de la mano o mediante instrucciones individuales para cada una de las articulaciones, el movimiento es ejecutado al mismo tiempo que se visualiza en la simulación gráfica. Como ejemplo práctico, se presenta una aplicación usando la mano Allegro con sensores táctiles WTS-FT y se muestran diferentes ejemplos de prensión de objetos con la información táctil registrada en los sensores táctiles y las fuerzas calculadas usando los pares aplicados por los motoresPostprint (author's final draft