摘要
螺纹中轴线的精确测定是决定螺纹三维测量结果是否准确的重要因素之一。中轴线的倾斜、偏移会对工件坐标系的建立、螺纹的三维重构、参数检验等测量操作引入误差。基于三维点云的最小二乘拟合算法,开展了螺纹中轴线的拟合方法研究。根据螺纹表面点云数据,利用螺纹表面与中轴线的特征关系建立最小二乘数学模型,通过计算点云数据的三维凸包滤除螺纹自身三维结构带来的拟合误差,使螺纹中轴线的测定更精准。通过仿真实验,基于三维点云的最小二乘拟合算法拟合的直线与三维点云的距离方差为0.34,在旋合长度范围内与投影法确定的直线两端最大距离为0.15μm,符合三维测量高精度标准,基于三维点云的最小二乘拟合算法可以快速、准确地拟合螺纹中轴线。
The accurate determination of the central axis of the thread is one of the important factors that determine whether the three-dimensional measurement result of the thread is accurate.The inclination and offset of the central axis will introduce errors in the measurement operations,such as setting up the workpiece coordinate system,reconstructing the three-dimensional thread,and inspecting the parameters.Based on three-dimensional point cloud,the least squares fitting algorithm is proposed to develop the fitting method of the central axis of the thread.According to the point cloud data of the thread surface,the least square mathematical model is established by using the characteristic relationship between the thread surface and the central axis,and the three-dimensional convex hull of the point cloud data is calculated to filter out the fitting error brought by the three-dimensional structure of the thread itself,so the measurement is more accurate.Through simulation experiments,the distance between the straight line fitted by the least square fitting algorithm based on the three-dimensional point cloud and the three-dimensional point cloud has a variance of 0.34,the maximum distance between the two ends of the straight line determined by the projection method within the twist length is 0.15μm,which meets the high-precision standard for three-dimensional measurement.It shows that the least squares fitting algorithm based on the three-dimensional point cloud is a fast and accurate fitting method of the thread central axis.
作者
谢张宁
姜志华
朱惠臣
李智玮
雷李华
孔明
王道档
张波
XIE Zhang-ning;JIANG Zhi-hua;ZHU Hui-chen;LI Zhi-wei;LEI Li-hua;KONG Ming;WANG Dao-dang;ZHANG Bo(College of Metrology and Measurement Engineering,China Jiliang University,Hangzhou,Zhejiang 310018,China;Shanghai Institute of Measurement and Testing Technology,Shanghai 201203,China)
出处
《计量学报》
CSCD
北大核心
2020年第8期918-925,共8页
Acta Metrologica Sinica
基金
国家重大仪器科学设备开发(2018YFF01013104)
航空科学基金(201856Y5001)
国家市场监管总局科技项目(2019MK016)。
关键词
计量学
螺纹中轴线
三维点云
最小二乘法
凸包
metrology
thread central axis
3D point cloud
least squares
convex hull
