基于改进解释结构模型化方法的定位基准选择

Selection of location datum based on improved interpretative structural modeling method

针对由于零件图中几何要素间的尺寸关系和位置关系复杂导致定位基准选择困难的问题,采用解释结构模型化(ISM)方法对零件的定位基准选择进行研究。算法将零件图中几何要素间的尺寸链关系转化成要素间的邻接矩阵,实现了将抽象的几何模型向可运算的矩阵模型的转化。通过邻接矩阵运算得到可达矩阵,从而确定出零件图中各几何要素间的相互尺寸及位置关系。改进的算法通过判断可达矩阵中可达集及先行集数目来实现粗、精基准的选择,在算法中体现出基准重合原则及基准统一原则。通过具体实例验证了该方法对零件的定位基准选择的合理性。

To solve the selection problem of location datum for geometry element relation and position relation complication in the part picture, Interpretative Structural Modeling （ISM） method was used to study the localization datum of the part. The algorithm turned the size chain relation among the key geometry elements in the part picture into the matrix of the key elements, transformed abstract geometry model to computable matrix. Through calculating adjacency matrix, the reachable matrix was got, in order to identify the mutual size and position relation among geometry key elements in the part picture. The improved algorithm realized the precise and basic choice through judging the number of reachable set and attainable set in the reachable matrix, which embodies the principle of the datum coincidence and unification. The rationality of choosing localization datum of the part by the method was verified through a concrete instance.