On Computing the Friction Forces Associated With Three-Fingered Grasp

Computation of friction forces between ngers and object for a given external force is important in grasp planning. Based on the required friction forces, the magnitudes of the grasping forces can be adjusted in order to avoid slippage of the object between ngers. A new method is presented for computing the friction forces between the ngertips of a dexterous mechanical hand and the object. Finger-tips are modelled so they are able to exert normal forces and are making point contact with friction with the object. The method of this paper utilizes the geometrical information on the grasp con guration, screw geometry and biorthogonal system. Unlike the method proposed by (Holzmann and McCarthy 85), the method of this paper does not involve matrix inversion and the assumptions under which the computations are valid have a simple geometrical meaning. The method is demonstrated through detailed solutions of two examples.