Grasp Stability Analysis of Three-finger Hand in Three Dimensions.

The relation between internal grasp forces and the stability of the three-dimensional grasp problem by a three-finger hand is studied. It is shown that internal grasp forces affect the angular stiffness of the grasp system. We propose a method stabilizing the grasp system by setting the fingertip stiffness in two directions which are at a right angle with fingertip internal forces, and show sufficient conditions and algorithm for the fingertip stiffness to stabilize the grasp system. Finally, several numerical examples whitch illustrate the algorithm proposed in this paper are presented.