A correct and complete algorithm for the generation of mechanical assembly sequences

Abstract

This paper presents an algorithm for the generation of mechanical assembly sequences and a proof of its correctness and completeness. The algorithm employs a relational model which describes the geometry of the assembly and the attachments that bind one part to another. The problem of generating the assembly sequences is transformed into the problem of generating disassembly sequences in which the disassembly tasks are the reverse of feasible assembly tasks. This transformation leads to a decomposition approach in which the problem of disussemhling one assembly is decomposed into distinct subproblen~s, each being to disassemble one subassembly. It is assumed that at each assembly task exactly two subassemblies are mated and that all contacts between the parts in the two subassemblies are established. The algorithm returns the AND/OR graph representation of assembly sequences. The correctness of the algorithm is based on the assumption that it is always possible to decide correctly whether two subassemblies can be joined, based on geometrical and physical criteria. This paper presents an approach to conipute this decision. Bounds for the amount of computation required are presented. 56

Toward an object-oriented and automated approach for achieving robotic assembly

“…The proposed architecture includes the concept of feature and shape identification of the objects to be assembled by the robot. Homem de MeUo and Sanderson (1989) introduced an algorithm employing a relational model which described the geometry of assembly and the attachments that bind one part to another. Lee and Fu (1983) have also presented a systematic method based on an approach that integrates the constructive solid geometry (CSG) scheme with a relational database management system (DBMS) for CAD/CAM.…”

Automated generation of assembly sequence based on geometric and functional reasoning

“…Boneschanscher and Heemskerk (1990) have described a partgrouping methodology, in which parts having common assembly features are grouped together, thus generating subassemblies. An algorithm for generation of all assembly sequences and the proof of i.ts correctness and completeness is presented in Homem de Mello and Sanderson (1989). This uses a relational model which describes geometry of the assembly and attachments which bind one part to another.…”

Assembly Coplanner: co-operative assembly planner based on subassembly extraction

“…An HPOG is a unified representation scheme for temporal and spatial relationships among assembly operations. In comparison with previous approaches (De Fazio and Whitney, 1987;Baldwin et al, 1991;Homem de Mello and Sanderson, 1991b), the proposed approach presents a unique method for enhancing the planning efficiency through the merging process, and evaluating subassemblies based on the criteria associated with the assembly cost.…”

“…A representation of all the possible assembly sequences by an AND/OR graph has been proposed by Homem de Mello and Sanderson (1991a). Methods for generating such an AND/OR graph based on the feasible cut-set of a liaison graph (Homem de Mello and Sanderson, 1991b) or based on the sequence of merging of components defined by the face-to-face composition model (DeFloriani and Nagy, 1989) have been suggested. It should be noted, however, that the number of cut-sets to be tested for feasibility can grow exponentially with the number of parts, resulting in a superfluously complicated, voluminous AND/OR graph.…”