In-Hand Manipulation with Soft Fingertips

This paper introduces an approach for solving the in-hand manipulation problem, that is, the change of a grasped object pose from an initial configuration to a final one without breaking contact, with robot fingers having out-of-plane motion, redundancy, and equipped with soft fingertips. The proposed technique is based on keeping the initial grasp equilibrium condition as a constraint to resolve finger redundancy. Two important aspects of in-hand manipulation with soft fingertips are then studied; namely: i) the modeling of soft fingertip contacts between fingers and 3D objects, and ii) an efficient method for computing joint angles to move a grasped object between different poses without losing grasp equilibrium. Numerical and empirical experiments using soft fingertips with different shore hardnesses with a two-fingered robot hand, composed of four-degree-of-freedom fingers with out-of-plane motion, are conducted. Results successfully validate the introduced strategy and its components.