基于聚焦深度法的刀具几何参数三维测量方法  

Three-dimensional measurement of geometrical parameters of cutting tools based on depth from focus method

作　　者：张沛东 刘巍[1] 王文琪 司立坤[1] 张洋[1] 周孟德 Zhang Peidong;Liu Wei;Wang Wenqi;Si Likun;Zhang Yang;Zhou Mengde(School of Mechanical Engineering,Dalian University of Technology,Dalian 116000,China)

机构地区：[1]大连理工大学机械工程学院,辽宁大连116000

出　　处：《红外与激光工程》2023年第4期244-253,共10页Infrared and Laser Engineering

基　　金：国家重点研发计划(2018YFA0703304);国家自然科学基金(92148301,52125504);中国博士后基金(2022M710591,2021TQ0056)。

摘　　要：刀具几何参数的精确测量是评估刀具性能的关键。针对复杂刀具几何参数难以测量的问题,基于聚焦深度法对其端面几何参数进行三维测量。首先,提出了一种适用于刀具端面序列图像的改进双阈值Tenengrad聚焦评价函数,通过局部像素分析确定了函数最佳计算窗口大小,在清晰度比率、陡峭度、清晰变化率、局部波动量评价指标下与常用聚焦函数进行了对比,验证了所提函数在计算刀具端面序列图像时更具有优势;其次,通过自适应sigmoid函数的图像增强算法实现了高对比度的刀具端面序列图像的获取,提升了三维测量效率,基于RANSCA算法对刀具后刀面点云表面进行平面拟合并提出了端面几何参数向量计算方法;最后,通过所构建的刀具测量系统对标准量块的阶梯深度进行了测量,误差为0.32%,并实现了刀具后刀面的三维形貌还原,进一步对主切削刃内、外刃顶角和直径参数进行测量。实验结果表明:顶角测量误差<0.3°,直径测量误差<3μm,优于Tenengrad函数对应角度(<1.9°)及直径(<13μm)测量结果,满足复杂刀具对角度(<0.5°)和直径(<10μm)的测量精度要求。Objective Cutting occupies a dominant position in mechanical manufacturing,which is the key factor in the development of aerospace,automotive,and electronic industries and other fields.As one of the most important terminals in manufacturing,cutting tool plays an outsized role in removal machining.It is proved that the geometrical parameters have a significant influence on the quality of the workpiece,the efficiency of cutting and the tool life.Given the importance of tool geometry parameters,it is essential to measure these parameters precisely before and during manufacturing.With the increasing requirements of different materials to process,the structures of the cutting tools used to machine become more complex than traditional cutting tools which brings a challenge for the precision measurement.Compared with the common method based on feature images and structured light sensors,the measurement method based on depth from focus presents the advantages of high precision and plenty of data.Hence,a geometry measurement method of cutting tools based on the depth from focus is proposed and the key technique is discussed.Methods Firstly,to solve the problem that the existing focusing function is not suitable for the sequence images of the measured cutting tools and improve the accuracy of the 3D reduction,an improved focus evaluation function based on the double-threshold Tenengrad function is proposed.Due to the surface irregularities of complex tools,the cutting edge is interrupted,resulting in sharp and diverse edge properties.In order to boost the gray gradient and calculate the edge information that the original convolution operator ignored,the function is improved by adjusting the convolution operator and expanding the direction angle of the edge gradient.Moreover,noise information is taken down using an image preprocessing algorithm and a double threshold constraint to generate a high-quality 3D point cloud.Specifically,Gaussian filtering and the Laplacian image enhancement algorithm are applied to remove the im

关 键 词：聚焦深度法 聚焦评价函数 三维形貌还原 刀具几何参数测量 

分 类 号：TN29[电子电信—物理电子学]