Stable "blind grasping" of a 3-D object under non-holonomic constraints

Abstract

A mathematical model expressing motion of a pair of multi-DOF robot fingers with hemi-spherical ends grasping a 3-D rigid object with parallel flat surfaces is derived together with non-holonomic constraints. By referring to the fact that human grasp an object in the form of precision prehension dynamically and stably by opposable forces between the thumb and another finger (index or middle finger), a simple control signal constructed from finger-thumb opposition is proposed and shown to realize stable grasping in a dynamic sense without using object information or external sensing (this is called "blind grasp" in this paper). Stability of grasping with force/torque balance under non-holonomic constraints is analyzed on the basis of the concept called "stability on a manifold". A few of preliminary simulation results is shown to verify the validity of theoretical results