Dexterous dynamic optimal grasping of a circular object with pose regulation using redundant robotic soft-fingertips

Dexterous object manipulation with robotic hands (subject to holonomic constraints) usually requires the capacity of fingertips to roll onto the object, which is very difficult to achieve with frictionless point contact model . As an alternative, deformable contact model has been considered based on hemispherical shape end-effector to yield rolling. However, it entails dexterity at the expense of dealing with normal and tangential forces, as well as more elaborated dynamic models. In this paper, a passivity-based controller is proposed for redundant robotic fingers with hemi-spherical deformable fingertips to manipulate dexterously a circular dynamic object. Redundancy and rolling are exploited to control normal and tangent contact forces to yield an optimal grasping. The optimal grasping is based on to align dynamically the normal forces applied to the object that allow its manipulation with minimum tangent forces. Stability conditions are presented to guarantee local asymptotic convergence. Finally, numerical simulations show the performance of the forces toward desired pose. This approach can be extended to objects with arbitrary shape that admit a local decomposition by a circular curvature.