Stable Grasping and Posture Control for a Pair of Robot Fingers with Soft Tips

This paper derives and analyzes non-linear dynamics of grasping a rigid object by a pair of robot, fingers with soft and deformable tips. A method of synthesizing a feedback control signal for stable grasping and posture control of the object is presented, which is based on passivity analysis of the dynamics including extra terms of Lagrange's multipliers arising from holonomic constraints of tight area contacts between soft finger-tips and surfaces of the object. Finally, usefulness of the proposed control method is discussed from the practical viewpoint. Simulation results suggest that a linear superposition of feedback signals realizes stable grasping and posture control of the object at, the same time. Nevertheless, challenging a design problem of sensory feedback for realizing dexterous motions of multi-fingered hands is quite important, because even at the present stage only open-loop control schemes are used for controlling dexterous hands.