为解决传统视觉式刀具测量仪采用的分段拟合方法在测量严重磨损刀刃时误差较大的问题,提出一种基于单一函数表达式的刀刃轮廓散点的整体拟合方法。首先采用改进的k-余弦曲率算法提取刀刃轮廓曲线角点,并使用最小二乘法进行分段拟合;然后确定刀刃轮廓曲线拟合目标函数的单一表达式,并在分段拟合结果的基础上,通过Levenberg-Marquardt迭代法进行非线性整体拟合。实验结果表明,整体拟合方法对严重磨损刀具测量时,能在保证目标函数曲线连续性的基础上,提高拟合精度达20%以上,这大幅度提高了刀具的测量精度及算法的稳健性。

A single expression based overall fitting method for scattered points of blade contours is proposed to address the large measurement errors of the existing tool measurement instruments when measuring severely worn tools based on machine vision and piecewise fitting. An algorithm of k-cosine curvature is used to extract the corners of the blade contour and the least square method is used for piecewise fitting. Based on this, a single expression of the blade contour used for object function fitting is determined and the nonlinear overall fitting is performed using Levenberg-Marquardt iteration. Finally, experimental results indicate that the overall fitting method can ensure the continuity of the fitting curve and improve the accuracy by more than 20% when measuring severely worn tools, drastically improving the measurement accuracy and robustness of the algorithm.