Disassembly sequencing and assembly sequence verification using force flow networks

The design of an assembly line for a mechanical assembly has to satisfy all the geometrical and the physical constraints presented in the assembly such as blocking relation and contact forces. Given a desired final assembly, determining an appropriate assembly sequence which satisfies not only the blocking constraints but also the force constraints needs a proper model to directly provide the information needed to reason about assembly. We introduce a representation, the directional force graph, which explicitly describes how parts interact in the assembly. This representation is used to determine disassemblable parts that are naturally broken apart from an assembly by a decomposition force. A decomposition force is an external force applied to a held part(s) against a fixture part(s). The proposed approach provides a mechanism to explicitly incorporate the real-world constraints of assembly directions, fixturing, and tooling requirements into planning. We describe a complete planning algorithm and report the results.