Evaluation of robotic fingers based on kinematic analysis

Abstract

This paper presents an evaluation of joint configurations of a robotic finger based on kinematic analysis. The evaluation is based. on an assumption that the current control methods for the fingers require that the contact state specified by the motion planner be maintained during manipulation. Various finger-joint configurations have been evaluated for different contact motions. In the kinematic analysis, the surface of the manipulated object was represented by B-spline surface and the surface of the finger was represented by cylinders and a half ellipsoid. Three types of contact motion, namely, 1) pure rolling, 2) twist-rolling, and 3) slide-twist-rolling are assumed in this analysis. The finger-joint configuration best suited for manipulative motion is determined by the dimension of manipulation workspace. The evaluation has shown that the human-like fingers are suitable, for maintaining twist-rolling and slide-twist-rolling but not for pure rolling. A finger with roll joint at its fingertip link, which is different from human fingers, proved to be better for pure rolling motion because it can accommodate sideway motions of the object. Several kinds of useful finger-joint configurations suited for manipulating objects by fingertip surface are proposed.