一种用于逆向工程的对称平面重建方法

A simple and efficient method for reconstructing symmetry plane in reverse engineering

在对称实物测量造型中,基于对称面进行模型重建可以减少测量数据量、精确重建对称特征和保证实物的对称性.由此提出了一种用于实物测量造型的对称基准平面重建方法.首先选择一组对称特征,然后将测量数据点投影在一初始平面上并用折线连结,旋转初始平面使两条折线重合,可以得到一个与对称平面平行的平面.接着再移动平行平面,使对称特征到它的距离相等,这时的位置平面即为所求的对称平面.此方法已在逆向工程数据前处理系统中实现,并应用于摩托车外形塑件的逆向工程.

Presents a symmetry plane reconstruction method based on measured data points, because the majority of parts had been designed with symmetry geometric relationship; after the symmetry plane had been recovered and one with symmetry featuress has been modeled, other symmetry features can be reconstructed by mirror operation. The algorithm steps include: chosing a couple of features with symmetric relationship which usually are boundary contour curves; fitting the curves as Bspline or polyline segments, then project ing the curves on an initial plane, wthere the measured part of teh central plane is defined as an initial plane; subsequently calculating the areas surrounded by the projected curves or the distance between the projected curves, where there certainly exists one plane (defined as initial symmetry plane)which makes the areas or distance minimum; again mirroring two contours about the plane, translating the plane to make the distance of points to the contour minimum; and finally obtaining an approximate symmetry plane. The technique was proved valid by practically application and has been integrated with the current commercial CAD systems.