Geometric computation based assembly sequencing and evaluating in terms of assembly angle, direction, reorientation, and stability

摘要

Assembly sequence matters much to the performance in assembly production. Focusing on the spatial assembly sequencing and evaluating, a set of geometric computation methods and algorithms are studied systematically. A method entitled 3D geometric constraint analysis (3D-GCA) is proposed based on the planar GCA method combined with the techniques of oriental bounding boxes and the separation axis theorem. With 3D-GCA, the assembly precedence relations and the spatial geometric feasible assembly sequences can be reasoned out correctly and automatically. Furthermore, four evaluation criteria, viz. assembly angle, assembly direction, reorientation, and stability, and related algorithms are defined for evaluating the assembly's complexity. For selecting the optimal sequence, a comprehensive evaluation function is constructed by integrating the four criteria and the weights are quantitatively allocated referring to fuzzy set theory, clustering analysis, and entropy theory. In addition, a software prototype system is developed and two case assemblies are studied. The analysis results and findings demonstrate that the proposed approaches and algorithms can provide significant assistance in the spatial assembly sequencing and the optimal sequence selection.