A theory on grasping objects using effectors with curved contact surfaces and its application to whole-arm grasping

This paper develops a theoretical framework for grasping objects using customized effectors that have curved contact surfaces, and presents its application to the problem of robotic whole-arm grasping. We present a collection of immobilizing grasps and cages that can effectively restrain the mobility of a wide range of object shapes including polyhedra. Each of the grasps or cages is formed by at most three effectors with appropriate contact surfaces in contrast to customary point fingertips. We also discuss the morphology of the curved contact surfaces that can realize the grasps and cages; the surfaces can simply be planar, cylindrical, or spherical. Stable grasps are obtained by simple motion planning and control. Our theory is based on a conservative assumption that all contacts are frictionless, rigid, unilateral. Finally, we present a robotic system, comprised of a software suite and a modular reconfigurable manipulator outfitted with exchangeable end-effectors and arm links, demonstrating the theory and our approach to whole-arm grasping.