Object handling by three-fingered hands using slip motion

In this paper, a quasi-static object manipulation by an articulated three-fingered robot hand with slip motion of grasping is discussed. This kind of manipulation achieves more dexterous manipulation by robot hands. The equilibrium relations of fingertip forces for grasping an object are solved in three dimensions. It is assumed that a slip happens when the fingertip forces go beyond the bound of the cone of maximum static friction. Possible directions of slip within a grasp are determined from the analysis. The fingertip force which achieves a desired slip motion is determined uniquely. Finally the set of fingertip forces is obtained, and the planning method of slip motion is discussed