HARD AND SOFT FINGERED ROBOT GRIPPERS - THE LINEAR COMPLEMENTARITY APPROACH

This paper deals with the problem of grasping work pieces with frictional multifingered grippers. The two types of frictional fingers "hard finger" and "soft finger" are treated. Hard fingers have the ability to constraint the object displacements on the normal and tangential directions to the object boundary, whereas soft fingers have in addition the ability to constraint the rotation of the object about the normal axis through the point of contact. The unilateral contact problem and the frictional problem are formulated in a compact form as a nonsymmetric Linear Complementarity Problem (LCP). Necessary and sufficient conditions which guarantee the solvability of the problem are derived. Also numerical examples computing the normal and tangential reactions, the slip Lagrange multiplier and the rigid body displacements and rotations are given.