On the Form-Closure of Polygonal Objects with Frictional and Frictionless Contact Models

This paper investigates the problem of " formclosure" for three-fingered grasps of polygonal objects under various combinations of contact models at the contact points. We show that equilibrium can be maintained even when some of the contacts between the fingers and the grasped object are frictionless and tangential contact forces do not exist. Feasible regions to place the fingers on and to safely manipulate the object under various combination of contact models are identified through our analysis.