Product Assembly Sequence Planning Based On Intelligent Water Drops Algorithm

Assembly sequence planning(ASP)is an important part of assembly process planning.By sequencing the assembly parts under given constraints,the assembly scheme with lower production cost,higher assembly efficiency and better product quality was obtained.Therefore,the assembly sequence planning plays a very important role in the assembly work.Since assembly sequence planning is a typical combinatorial optimization problem,this thesis proposed an intelligent water drops(IWD)algorithm to solve this problem based on existing research results.This method is based on three aspects: assembly sequence modeling,evaluation system construction and optimal assembly sequence acquisition.The main research contents and conclusions are as follows:(1)Based on the analysis of the main components of the assembly sequence,the assembly is divided into assembly units,and the assembly sequence planning is realized by sorting the assembly units.Then the geometric interference relationship between the assembly units and the assembly priority constraint relationship are analyzed.The definition of the assembly constraint relationship is realized by constructing the non-orthogonal interference matrix and the assembly priority matrix.An example shows that the above method can guarantee the feasibility and rationality of assembly sequence planning.(2)The main evaluation indexes of assembly planning are determined by studying the geometric feasibility,the concentrative degree of tools,the transformation of the direction,and the operation stability.The experimental results show that the evaluation function can evaluate the advantages and disadvantages of the assembly sequence and select the better assembly sequence scheme.(3)Based on the iterative nature of the IWD algorithm,each assembly unit in the assembly sequence is combined with the nodes in the flow path of water-drop,and the complete assembly sequence can be obtained when the water-drop flows through all nodes.In addition,the similarity between assembly units is defined according to the similarity degree of assembly tool and assembly direction.The similarity between assembly units is matched with the amount of soil between nodes in the flow path.Through global search in the feasible solution space,the intelligent droplet algorithm can find the optimal assembly sequence.The experimental results show that different population numbers have different effects on the optimization results,and it is necessary to set a sufficient number of water-drops to avoid falling into local search.(4)Taking plunger pump and aircraft cabin door as examples,the assembly sequence planning of two assemblies is carried out by using IWD algorithm,and the results were compared with the ant colony algorithm and genetic algorithm.The results show that the proposed method can effectively obtain the optimal assembly sequence planning scheme and verify the effectiveness and correctness of the proposed method.