Fine - Motion Planning in the Contact Space of Narrow - Clearance

A ne-motion planning technique is described for assemblies with narrow insertion clearances. A ne-motion planner receives as input a nominal assembly motion plan, computed from kinematic constraints alone. As described in a companion paper [4], the planner constructs an adjacency graph for each local contact space surrounding a problematic con guration in the nominal trajectory. A heuristic search of the adjacency graph produces a sequence of contact states that can be traversed in the presence of pose uncertainty, thus maneuvering the assembly past the problematic con guration. The rapid synthesis of a ne-motion trajectory through the selected contact states is facilitated by the nearly hyperpolyhedral nature of local contact space. The trajectory's distance to contact space facets representing undesired contact state transitions is maximized, and the resulting ne-motion plan is expressed as a sequence of hybrid control strategy speci cations. Fine-motion trajectories produced by this technique have been successfully executed by a Zebra-0 robot. 1 With the exception of section 4 and related appendices, this paper appeared in the Proceedings of the 1993 IASTED International Conference on Robotics and Manufacturing, pp. 206-8. 2 Preparation of this paper was supported by grants IRI-9208920 and CDA-8922572 from the National Science Foundation.