基于机器视觉的激光熔覆熔池形貌监测

Laser Cladding Pool Morphology Monitoring Based on Machine Vision

为了研究激光熔覆过程中熔池形貌的变化,搭建了激光熔覆熔池在线监测系统。采用COMS相机与激光设备同轴装配的方式获取熔池图像,在分析熔池灰度直方图分布的基础上,采用三角阈值分割的自适应阈值分割法对熔池图像进行二值化,通过Canny算子检索出熔池图像的边缘,利用最小外接矩形算法获取熔池区域的长和宽。以45钢为基体、420不锈钢为熔覆粉末进行9组单道熔覆正交实验。实验结果显示,在该监测系统下测得的熔池宽度与电子显微镜下测量的实际熔覆宽度平均误差为4.5%,验证了该视觉监测系统的有效性。对监测系统下得到的熔池宽度进行极差分析,结果表明:激光功率对熔池宽度的影响最大,其次是扫描速度,最后是送粉速率;熔池宽度随激光功率的增大而增大,随扫描速度和送粉速率增大而减小。利用该监测系统获取的熔池信息与变化规律可作为激光熔覆实时控制的参考变量,为激光熔覆实现闭环控制奠定基础。

In order to study the change of molten pool morphology during laser cladding,an on-line monitoring system of laser cladding molten pool is established.The molten pool image is obtained by coaxial assembly of COMS camera and laser equipment.On the basis of analyzing the gray histogram distribution of molten pool,the adaptive threshold segmentation method based on triangular threshold segmentation is used to binarize the molten pool image.The edge of the molten pool image is retrieved by Canny operator,and the length and width of the molten pool area are obtained by the minimum outer rectangle algorithm.Using 45 steel as matrix and 420 stainless steel as cladding powder,nine orthogonal single-pass cladding experiments are carried out.The experimental results show that the average error between the molten pool width measured by the monitoring system and the actual cladding width measured by the electron microscope is 4.5%,which verifies the effectiveness of the visual monitoring system.Through the range analysis of the molten pool width obtained by the monitoring system,the results show that the laser power has the greatest influence on the molten pool width,followed by the scanning speed,and finally the powder feeding rate.The width of molten pool increases with the increase of laser power,but decreases with the increase of scanning speed and powder feeding rate.The molten pool information and variation law obtained by the monitoring system can be used as the reference variables for the real-time control of laser cladding,which lays the foundation for the closed-loop control of laser cladding.