Communication on Optimal Grip Points for Contact Stability

The identification of contact points is a priority in planning grasps. This paper proposes a criterion for the determination of optimal grip points to secure contact stability. The criterion is generally valid, that is, it applies to grasps with any number of contact points on objects having a generic shape (polygonal or curved), and does not require that the external force acting on the object be known. A grasp-quality index, fmin, obtained by minimizing the friction coefficient needed to ensure contact stability in the presence of a generic disturbing external action, has been introduced. The criterion leads to the formulation of an optimization problem with nonlinear constraints that is easy to implement. Finally, some examples are provided which compare the results reported in the literature with the results obtained by applying the criterion proposed in this paper.