Capturing pyramidal-like objects

This paper discusses a grasp scheme for a pyramidal-like object placed on a table under the gravitational field. We assume that the contact friction is small enough to ensure that any direct grasp fails in achieving an equilibrium grasp. For an idealized 2D triangle object placed vertically on a table, we first show that a planar two-fingered hand can always achieve an equilibrium grasp under frictional contact. We also extend the basic idea to a polyhedron whose face is triangle and show two possible procedures leading to equilibrium grasps. Finally, we verify our idea experimentally for the polyhedra.