Embly Sequencing

This article considers the computational complexity of automatically deter mining assembly sequences for mechanical products Speci cally we address the partitioning problem given an assembly of rigid parts identify a proper subassembly that can be removed as a rigid object without disturbing the rest of the assembly We examine the complexity of the partitioning problem un der various types of relative motions allowed for the subassemblies We show that when arbitrary motions are allowed to separate the two subassemblies partitioning is NP complete We then describe a general framework for reasoning about assembly mo tions called the interference diagram In its most general form the interference diagram yields an exponential time algorithm to partition an assembly How ever two special cases of the interference diagram studied in this article yield polynomial time sequencing algorithms The rst case occurs when assembly motions are restricted to single translations The second case considers in nitesimal rigid motions in translation and rotation and yields a superset of all feasible partitionings These two algorithms have important practical applica tions in assembly planning Intelligent Systems and Robotics Center Sandia National Laboratories Albuquerque NM USA This work was performed while the author was at Stanford University Computer Science Robotics Laboratory Stanford University Stanford CA USA MIT Arti cial Intelligence Laboratory Technology Square Cambridge MA USA