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基于三维点云的栅极间距测量方法
杨蕴杰,方宇,杨皓,张伯强,黄子健,李皓宇
上海工程技术大学 机械与汽车工程学院,上海 201620
摘要:
栅极组件间距决定了离子推力器的工作性能和可靠性,栅极间距自动化检测对提高栅极装配效率和装配质量具有十分重要意义。为了解决栅极间距自动化检测问题,采用线激光扫描技术,建立了双层拱面栅极件的三维点云模型,使用点云密度算子区分了点云模型中边缘点和非边缘点,通过DBSCAN算法将边缘点根据数据连续性聚类;针对点云边缘数据存在的噪点和密度分布不均问题,提出了边缘数据的中心计算方法,通过边缘点集合到中心距离的离散程度判断形状是否为圆孔,最后计算圆心坐标到栅极下表面距离作为栅极间距。通过试验对本文提出的算法进行鲁棒性和精度验证,结果显示:在添加标准差为0.05mm和0.1mm的高斯噪声模拟环境干扰下,算法鲁棒性良好;将本文方法计算得出的栅极间距与传统人工方法进行比较,测量值最大误差为36μm,误差均值为17μm。研究结果表明,本方法有望代替现有人工测量手段,实现栅极间距非接触式自动化测量。
关键词:  离子推力器  栅极间距  三维点云  圆孔提取  圆心计算  自动化测量
DOI:10.13675/j.cnki.tjjs.210600
分类号:TN206
基金项目:上海市松江区科技攻关项目(20SJKJGG08C);上海市高水平应用技术大学创新平台建设项目。
Grid Gap Measurement Method Based on Three-Dimensional Point Cloud
YANG Yun-jie, FANG Yu, YANG Hao, ZHANG Bo-qiang, HUANG Zi-jian, LI Hao-yu
School of Mechanical and Automotive Engineering,Shanghai University of Engineering Science, Shanghai 201620,China
Abstract:
The grid gap determines the working performance and reliability of the ion thruster. Automatic detection of grid gap is of great significance to improve grid assembly efficiency and quality. In order to solve the problem of automatic detection of grid gap, a three-dimensional point cloud model of double-layer arched grid was established by using line laser scanning technology. The point cloud density operator was used to distinguish the edge points and non-edge points in the point cloud model, and then the edge points were clustered according to the continuity of the data through the DBSCAN algorithm. Aiming at the problems of noise and uneven density distribution in point cloud edge data, a center calculation method of edge data was proposed and whether the shape was a circular hole was judged by the dispersion of the distance from the edge point set to the center. Finally, the distance from the center coordinate to the lower surface of the grid was calculated as the grid gap. The robustness and accuracy of the proposed algorithm were verified by experiments. The results show that the algorithm had good robustness when Gaussian noises with standard deviation of 0.05mm and 0.1mm were added to simulate the environmental interference. Comparing the calculated value of the algorithm with the traditional manual method, the maximum error was 36μm and the average error was 17μm. The research shows that this method is expected to replace manual measurement and realize non-contact and automatic detection.
Key words:  Ion thruster  Grid gap  Three-dimensional point cloud  Circle extraction  Center calculation  Automatic detection