Dynamic Stable Pinching by a Pair of Robot Fingers

Abstract

This paper is concerned with a stability problem of pinching motion by a pair of robot fingers with hemispherical ends maintaining a grasp of a rigid object with two parallel flat surfaces and at the same time regulating its orientation. It is then shown that there exists a sensory feedback from measurement of finger joint angles and the rotational angle of the object to control inputs to joint actuators and this feedback connection from sensing to action realizes simultaneous grasp and orientation control of the object, provided that motion of the fingers-object system is confined to a plane. To discuss the stability of grasping together with orientation control in a rigorous sense, a new concept called “stability on a manifold” is intorduced and the convergence of a solution trajectory to a lower dimensional manifold subject to a prescribed grasping force together with a prescribed orientation of the object is proved.