A structure-oriented approach to assembly sequence planning

An assembly sequence planner is a system which, given a description of an assembly to be manufactured, identifies subassemblies and generates high-level plans for the construction of the each subassembly, including the final assembly. Previous research has shown that feasible plans can be efficiently produced for large assemblies, but the generation of good plans has met with less success. Not only are there difficulties in defining "good plans," but all published methods for finding good plans have computational complexities that make them unlikely to be practical for large assemblies. This paper shows that representing an assembly as a hierarchy of assembly structures can overcome many of these difficulties. A planner is described which uses the structure hierarchy both as a framework for structure-dependent definitions of a good plan, and as a tool for finding good plans more rapidly by using high-level expert advice, by reusing subplans for repeated substructures, and by not fully optimizing the plan. Analytical and experimental results are presented to demonstrate the effectiveness of the approach.