Abstract: Accurately identifying the error transfor path of the meta-action unit was the premise of error analysis. A new method was proposed to judge the error transmission path of the meta-action units based on the concept of DOF constraints in mechanical systems. Firstly， the DOF constraint requirements of the precision output parts and the initial error transfer path were determined by analyzing the functions and the structures of the meta-action units. Secondly， the constraint properties of the joint surfaces were analyzed， and the DOF constraint properties of the precision output parts were calculated along the error transfer path. The error transfer path was determined by comparing the obtained constraint property with the designed constraint property. Compared with traditional methods， the proposed method improves the efficiency of the analysis and identification of the error transfer paths greatly. 

Key words: meta-action unit, assembly error, error transfer path, degree of freedom（DOF）

摘要： 准确识别元动作单元的误差传递路径是误差分析的前提。基于机械系统中自由度约束的概念，提出了一种利用自由度约束判断误差传递路径的新方法。首先，通过分析元动作单元功能和结构，确定精度输出件自由度约束要求并初步确定误差传递路径；然后，分析路径中零件结合面的约束属性，并沿误差传递路径计算精度输出件的自由度约束属性。将得到的自由度约束属性与自由度约束要求进行对比，确定误差传递路径。与传统方法相比，所提方法极大提高了误差传递路径分析和识别的效率。

关键词: 元动作单元, 装配误差, 误差传递路径, 自由度