Stability index and contact configuration planning for multifingered grasp

Abstract

It is necessary to plan the contact configuration to guarantee a stable grasp. This article discusses the grasping stability of multifingered robot hands. The fingers are assumed to be point contacts with friction. A stability index for evaluating a grasp, which is proportional to the ellipsoidal volume in the grasping task space, is proposed. The invariance of the index is proved under an object linear coordinate transformation and under a change of the torque origin. The similar invariance of the index is also proved under a change of the dimensional unit. The optimal grasping of an object by a multifingered robot hand can be obtained using the stability index to plan the grasp configurations. The index is applicable to plan adaptable fixtures as well. A nonlinear programming method to plan configurations is addressed. Several examples are given using the index to evaluate a grasp, in which the obtained optimal grasping is consistent with what human beings expect. The sensibility of the optimal grasping is analyzed in these examples. © 1998 John Wiley & Sons, Inc.