The sliding of robot fingers under combined torsion and shear loading

The authors are concerned with finding the magnitudes of applied moment and force which will cause a robot finger to slip on the surface of a grasped object. Friction and contact models used in previous grasp analyses are reviewed, and an improved model which includes torsion-shear interaction is described. Experimental measurements of the initiation of sliding as a function of loading are reported. These measurements suggest that a simple linear function of torsion and shear magnitudes will adequately predict the onset of the slip in many tasks. The use of this function is illustrated in two measures of slip susceptibility for grasp planning