ON COMPUTING 2-FINGER FORCE-CLOSURE GRASPS OF CURVED 2D OBJECTS

This article presents an algorithm for computing force-closure grasps of piecewise-smooth, curved, two-dimensional objects. We consider the case of a gripper equipped with two hard fingers and assume point contact with friction. Object boundaries are represented by collections of polynomial parametric curves, and force-closure grasps are characterized by systems of polynomial constraints in the parameters of these curves. All configuration space regions satisfying these constraints are found by a parallel numerical cell-decomposition algorithm based on curve tracing and continuation techniques. Maximal curve segments where fingers can be positioned independently are found by optimization within the grasp regions. The algorithm has been implemented on a distributed architecture, and experiments using a PUMA robot equipped with a pneumatic two-finger gripper and a vision system are presented.