Contact manipulation and geometric reasoning

Abstract

In assembly tasks, part-mating involves contact between parts with size tolerances and for some assembly strategies, jamming results. A way to avoid such problems is to explicitly use the contact during motion with an active compliant procedure. This paper deals with contact manipulation.

The first part models the assembly task taking into acount the contact relationship, and provides a solution to program active compliance. An assembly strategy is a set of motions constrained by the contact. The second part models the kinematics of contact relationships between polyhedral parts. The motion is made in space where the degrees of freedom are limited.

An assembly strategy is then a sequence of contact relationships. The papers describes a method to generate such strategies via the concept of a contact graph describing the changes in contact relationship when a new constraint is obtained along a trajectory. Thus motion occurs in a space with one degree of freedom. When a zero degree of freedom contact is obtained, a new connexe contact relationship with one degree of freedom is chosen.