Assembly Sequence Unconventionality Planning Method Based on Genetic Algorithms and Gray Theory for Complex Products

Aim at the problem that the variation of constraint leads to variation of assembly sequence, this paper presents a method based on the gray theory associated with genetic algorithm (GA). The variation of constraint on assembly site for complex products includes absence of parts, fixtures, resource and so on. Firstly, a seven-cell coding format is built based on multiple genes. The fitness function is built taking the constraint relation into account, and synthesizing the parallelism, stabilization, repeated directional and aggregation of the sub-assembly. The choice gather of assembly sequence is generated from the variation node after implementing GA operation. Secondly, the gray associated model is built considering the choice gather of assembly sequence as the gray decision-making gather. The reference sequence is generated from original assembly sequence. By analyzing the gray associated value, an optimal or near-optimal assembly sequence is created. This method is tested on a practical case and the result shows its feasibility and superiority.