基于STEP AP242的MBD模型表达研究与实现

针对产品协同研制过程中存在的软硬件异构、MBD模型信息表达不规范以及机器不可识别等问题，提出一种基于STEP AP242的MBD模型信息表达方法.以CATIA系统构建的MBD模型为研究对象，通过CATIA CAA二次开发技术，提取MBD模型相关信息并按照STEP AP242标准生成STEP标准中性文件.介绍STEP AP242标准的发展历史和几何尺寸公差的格式表达方式--展现与表达，再基于几何元素种类为面和边的情况分别给出MBD模型标注信息、标注信息与几何信息关联关系的表达与提取方法，通过EXPRESS语言实现MBD模型信息的STEP AP242标准化表达与转换，并通过STEP File Analyzer和STEP-NC Machine进行验证，实现了MBD模型的语义化几何尺寸与公差表达.

Research and development of MBD model definition based on STEP AP242

A MBD information expression method based on STEP AP242 was proposed for several problems, such as the collaborative problem between heterogeneous hardware and software in product development process, the non-standardized and non-machine-readable problem of MBD model. Take the MBD model constructed by CATIA system as research object; the relevant information in MBD model was extracted using CATIA CAA (component application architecture) customized development technology, and the STEP standard neutral files were generated according to STEP AP242 standard. Firstly, introduce the development history of STEP AP242 standard and the expression mode of geometric dimension & tolerance (GD&T), namely Presentation mode and Representation mode. Then, give the expressions and extraction methods of MBD model annotation information, the association between annotation information and geometric information based on geometric element categories, such as faces and edges. Finally, the expression and conversion with STEP AP242 standard about MBD model information are realized by EXPRESS language, and the feasibility and effectiveness of the method was verified by two tools, STEP File Analyzer and STEP-NC Machine. As results, sematic Geometric Dimension & Tolerance of MBD model is achieved.