特征设计的定位约束参数化技术

 提出一种三维参数化的系统模式，将参数化工作分为二维变量几何、扫描方向参数化及特征定位约束参数化3个相对独立的部分。针对反映三维参数化特点的定位约束参数化技术，提出用坐标系方式表示特征之间的定位约束关系，定义了所需的几种坐标系，分析了可能存在的约束关系类型，并从一般位置约束关系的分析入手，推导出相应的约束变换矩阵，拓宽了约束表示的覆盖域。还针对特征模型约束情况分析、判断和处理的需要，分析了各种约束类型的自由度亏损情况。

POSITION CONSTRAINT PARAMETERIZATION IN FEATURE BASED DESIGN

A systematized module of three dimensional parameterization, including variational geometry, sweeping orientation parameterization and feature position constraint parameterization, is proposed. For the last one with main characters of three dimensional parameterization, first the coordinate representing approach of constraints between features is presented and the coordinate systems needed are defined, then the existing constrained elements are analyzed and their constraint relations classified and the transform matrices of general position constraint relations deduced with more generality than late works. In addition, the loss of freedom (abbrev. lf) of all the cases are analysed for the needs of analysis, judgement and process of the constraint condition (redundant, under , over or equal constraints).