为解决磁流变抛光中回转对称非球面工件的高效率精确自定位问题, 提出了基于迭代最近点的改进两级定位方法。根据磁流变抛光特性和恒浸深控制要求, 确定了磁流变抛光工件非调平自定位原理。针对经典迭代最近点算法应用于回转对称非球面工件定位存在解不唯一及计算效率低的问题, 构建初始迭代矩阵实现了位姿唯一的指定性匹配, 并提出了空间垂直映射方法, 减小匹配点云的规模, 提高了计算效率。以此为基础, 提出了改进后的两级迭代最近点精确定位方法。最后, 以Φ100 mm凹形抛物面熔石英工件为对象进行了抛光实验。实验结果表明: 改进两级精确定位方法满足磁流变抛光的定位要求, 定位精度在多次实验中均优于9 μm, 平均定位时间为7.3 min, 在保证定位精度的同时提高了工件的定位效率。

To enhance the precise localization of rotary symmetric aspheric workpiece in magnetorheological polishing, an improved two-level positioning method (ITLICP) based on iterative closest point (ICP) was proposed in this study. The magnetorheological polishing characteristics and requirements revealed that the constant immersion depth control determines the principle of workpiece non-leveling positioning. The classical ICP algorithm was applied to overcome the drawbacks of rotationally symmetric aspheric workpiece positioning of non-uniqueness and low computational efficiency. In this study, an initial iterative matrix was constructed to realize the unique specified matching of the workpiece position and a vertical mapping method was proposed to reduce the matching point cloud size, thus improving the computational efficiency. Then, an improved two-level ICP precise positioning method was proposed. The positioning and verification experiments use a Φ100 mm concave parabolic fused silica workpiece. The results show that the precise positioning method ITLICP satisfied the requirements of magnetorheological polishing positioning. The positioning error is less than 9 μm and the average positioning time is 7.3 min. This demonstrates that both the positioning accuracy and efficiency are improved.