基于特征表面和空间关系的公差表示模型

Tolerance Representation Model Based on Feature Surfaces and Spatial Relations

现有的基于多色集合的公差表示模型的主要优点是能处理的特征种类较多。但由于多色集合无法处理自由度信息,模型生成的可选装配公差类型的数目较多,且不能直接用于公差分析与公差综合。针对该问题,在其原有的从特征表面到装配公差类型的映射的基础上,增加从空间关系到装配公差类型的映射,构建出基于特征表面和空间关系的公差表示模型。模型通过空间关系与装配公差类型之间的映射,对原来由特征表面之间的约束关系生成的可选装配公差类型进行筛选,进一步减少其数目。在由空间关系推理生成可选装配公差类型时,公差分析与公差综合所需的自由度信息亦随之生成,从而使得模型可直接用于公差分析与公差综合。通过装配公差类型的自动生成算法及工程实例验证了模型的有效性。

The main advantage of polychromatic sets based tolerance representation model is that the number of feature types to be processed is larger. Because polychromatic sets cannot deal with the information of degrees of freedom, the number of recommended assembly tolerance types generated by the model is somewhat large. The model cannot be directly applied to tolerance analysis and synthesis. Aiming at this problem, a tolerance representation model based on feature surfaces and spatial relations is constructed by adding the mappings from spatial relations to assembly tolerance types to the mappings from feature surfaces to assembly tolerance types. Through the mappings from spatial relations to assembly tolerance types, the number of the recommended assembly tolerance types generated by the constraint relations between feature surfaces is further reduced. The information of degrees of freedom needed in tolerance analysis and synthesis is generated when the recommended assembly tolerance types are generated by spatial relations. Thus the constructed model can be directly applied to tolerance analysis and synthesis. The effectiveness of the constructed model is demonstrated through an automatic generation algorithm of assembly tolerance types and a practical example.