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Paper details
Number 2 - June 2016
Volume 26 - 2016
Dynamic optimal grasping of a circular object with gravity using robotic soft-fingertips
Rodolfo García-Rodríguez, Victor Segovia-Palacios, Vicente Parra-Vega, Marco Villalva-Lucio
Abstract
Object manipulation usually requires dexterity, encoded as the ability to roll, which is very difficult to achieve with robotic
hands based on point contact models (subject to holonomic constraints). As an alternative for dexterous manipulation,
deformable contact with hemispherical shape fingertips has been proposed to yield naturally a rolling constraint. It entails
dexterity at the expense of dealing with normal and tangential forces, as well as more elaborated models and control
schemes. Furthermore, the essential feature of the quality of grasp can be addressed with this type of robot hands, but it
has been overlooked for deformable contact. In this paper, a passivity-based controller that considers an optimal grasping
measure is proposed for robotic hands with hemispherical deformable fingertips, to manipulate circular dynamic objects.
Optimal grasping that minimizes the contact wrenches is achieved through fingertip rolling until normal forces pass through
the center of mass of the object, aligning the relative angle between these normal forces. The case of a circular object is
developed in detail, though our proposal can be extended to objects with an arbitrary shape that admit a local decomposition
by a circular curvature. Simulation and experimental results show convergence under various conditions, wherein rolling
and tangent forces become instrumental to achieve such a quality of grasp.
Keywords
dynamic grasping, soft-fingertips, circular object