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 robotic 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 an ellipsoid. The solutions for inverse kinematics of manipulation which gives the finger joint displacements for a given displacement of the object is described briefly. Three types of contact motion, namely, 1) pure rolling, 2) twist-rolling, and 3) slide-twist-rolling are assumed in this analysis. The manipulation capability of the fingers is evaluated for each contact motion, and the finger joint configuration best suited for manipulation as determined by the size 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 motion of the object. Several kinds of useful finger joint configurations suited for manipulating objects by fingersurface are proposed.
