中文摘要：

大型水轮机叶片曲面翘曲，双面加工，笨重不易翻动，给其找正定位带来极大不便。长期以来，加工现场通常采用人工找正定位，其缺点是找正困难、效率低、精度差。本文通过反求工程方法将测量得到的大量离散毛坯表面数据，依据CAD模型的拓扑特征，重构毛坯表面，然后利用重构曲面与CAD模型曲面对应节点距离平方和构造目标函数，采用最小二乘法（LSQ）求解欧氏变换矩阵，从而达到毛坯加工余量均匀，实现计算机辅助定位的目的。实算证明：该方法能快速辅助找正；且对于表面质量高、边界规范的毛坯，定位比较准确。最后给出了一辅助定位实例。

英文摘要：

It is difficult for the localization of the large blade NC machining, which used to be measured by the probe of machine and adjusted manually. It is arduous and time - consuming, and even allowance can＇t be ensured for every measured point. The method of surface reconstruction was adopted to calculate the distance of the measured point to the designed surface, and the least - squares method was used to search the optimal location of surface matching. Transforming by the location matrix, even allowance can be ensured, this method can realize computer aided localization （CAL）, which enhances the precision of localization, saves much time, and greatly accelerates machining cycles while reduce machining cost. The practice shows the method is practical and useful.