基于约束解除的装配序列并行化优化

Concurrent optimization of assembly sequence based on constraint release strategy

为了提高产品装配的效率,提高装配序列的并行性,提出了基于约束解除和简化配合关联图的装配序列并行优化方法。给出了装配效率的评价指标—并行性评价因子的数学模型。将模糊逻辑用于装配约束的量化过程,通过约束归约方法将无约束条件下可自由运动零件的自身约束与零件间通过点、线、面之间几何约束关系所表达的装配约束进行求交,建立零件间的等价约束评价值即联接度,联接度概念的提出清晰地表达了配合关联图中的薄弱环节;在此基础上,建立装配体的赋权配合关联图,并根据联接度值的大小对零件间的虚联接进行简化,给出了一个基于阈值的追求装配最高并发度的配合关联图分解与重组策略,实现了装配序列并行优化,并通过实例说明了该算法的有效性。

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.