Abstract: Robot assembly states can be described by contact states between two assembly objects. In the motion direction, the minimum distances and angles between three basic kinds of contact pairs with boundary components of convex polyhedron are obtained. Some formulas are usable. The method can be used to judge contact states in the next moment. The example of a triple peg-in-hole verifies the analyses.

Key words: Assembly, Boundary components, Contact states, Convex polyhedron