Abstract:

This paper comes from a project of precision measurement and digital modeling of automobile engine and transmission system. The underlying constraint relationship among the features of mated parts was taken into account in reconstruction process, and a new optimization reconstruction method was presented based on geometric constraints,which were expressed by geometric constraint graphs.Adding constraints to constraint graphs by priority, considering degree of freedom to obtain a consistent constraint system and finally the complicated constraint problems were decomposed into sub-problems to be solved.The approach was demonstrated by the practical parts from an automobile transmission system.The obtained geometric models are conformed to original design intents in geometric features and ensure assembly precision.

Key words: model reconstruction, geometric constraint, constraint consistent, degree of freedom analysis

摘要：

结合汽车变速箱、发动机零部件的精密测量和数字建模，考虑零部件实物模型中的隐含约束关系，提出了基于几何约束的模型重建和优化求解方法。该方法把约束按照优先等级顺序添加到约束图中，应用自由度分析法建立协调的约束系统，把复杂约束问题分解为约束子问题进行求解。将该方法应用于变速箱零部件模型重建中，所得到的几何模型较好地反映了原始设计意图，满足产品装配精度要求。

关键词: 模型重建, 几何约束, 约束协调, 自由度分析法