Geometric reasoning about assembly tools

AbstractPlanning for assembly requires reasoning about various tools used by humans, robots, or other automation to manipulate, attach, and test parts and subassemblies. This paper presents a general framework to represent and reason about geometric accessibility issues for a wide variety of such assembly tools.Central to the framework is a use volume encoding a minimum space that must be free in an assembly state to apply a given tool, and placement constraints on where that volume must be placed relative to the parts on which the tool acts. Determining whether a tool can be applied in a given assembly state is then reduced to an instance of the FINDPLACE problem (Lozano-Pérez, 1983). In addition, we present more efficient methods to integrate the framework into assembly planning. For tools that are applied either before or after their target parts are mated, one method preprocesses a single tool application for all possible states of assembly of a product in polynomial time, reducing all later state-tool queries to evaluations of a simple expression. For tools applied after their target parts are mated, a complementary method guarantees polynomial-time assembly planning.We present a wide variety of tools that can be described adequately using the approach, and survey tool catalogs to determine coverage of standard tools. Finally, we describe an implementation of the approach in an assembly planning system and experiments with a library of over one hundred manual and robotic tools and several complex assemblies