Regrasp planning for polygonal, polyhedral and discrete objects

Abstract

This dissertation addresses the problems of planning a set of regrasp sequences for manipulating a polygon, a polygon with a large number of edges, a polyhedron and a discrete object. Assuming frictional point contact, we propose approaches for computing sequences of finger repositioning that allow the hand to switch from one grasping configuration to another while maintaining force closure during the entire process. The proposed approaches are based on exploring a structure called switching graph. For a polygon or a polyhedron, a vertex in a switching graph explicitely contains a set of force closure grasps. In constrast, for a discrete object, the input with a large number of discrete contact points is considered. In this setting, traditional methods of complete solution is not available. Based on wrench space information of the input, our proposed algorithm clusters the input into groups and chooses a representative from each group. A global graph structure for regrasp planning is then constructed using all force closure grasps that can be formed only by representatives. Also described are approaches for finding a regrasping sequence from an arbitrary grasp to a grasp in the global structure. The connectivity of a graph captures ability to switch from one grasp to another and allows regrasp planning to be formulated as a graph search. The proposed approaches have been implemented and computational results are presented.