Concurrent optimization of assembly sequence based on constraint release strategy

To improve the efficiency of product assembly and the concurrency of assembly sequence, an approach to realize concurrent optimization of assembly sequence was proposed based on constraint release and simplified liaison graph. To quantify the measurement of assembly efficiency, a mathematical model of concurrency evaluation index was put forward, and then a technology to quantify assembly constraints was developed by the application of some fuzzy logic algorithms. In the process of concurrent optimization of assembly sequence, two kinds of constraints were involved. One was self-constraints of components, which was used to evaluate the assemble capability of components under the condition of full-freedom. Another was assembly constraint between components represented by geometric constraints between points, lines and planes under physical restrictions Concept of connection strength degree (CSD) was introduced as one efficient indicator and the value of it was evaluated by the intersection of the two constraints mentioned above. The equivalent constraints describing the connection weights between components were realized by a well-designed constraints reduction, and then the connection weights-based complete assembly liaison graph was applied to release virtual connections between components. Under given threshold value, a decomposition and reconstituting strategy for the graph with the focus on high assembly concurrency was used to realize optimized assembly concurrency evaluation index. Finally, the availability of the approach was illustrated by an example of the assembly of shift pump.