基于二维轮廓点云的螺纹中径计算

Abstract

The multi-parameter measurement of a thread based on profile points may show calculation errors for thread pitch diameters owing to the alignment deviations and inhomogeneous abrasion of thread work-pieces.Therefore,a new method for calculating the thread pitch diameters based on the2-dimensional profile point clouds was proposed.The cubic spline interpolation was used to increase the data point densification uniformly,and the robust Gauss regression filter was adopted to get the midline of contour.Then,an objective function was put forward to minimize the mean square error of the distance between two adjacent flank segments,and the complex simulated annealing algorithm was adopted to solve the function to get the pitch line.Finally,the pitch diameter parameters were calculated with the obtained pitch line.The experimental results show that the measurement error ofpitch diameter obtained by the proposed method is reduced by 17.23% and 96.93% respectively compared with the methods from FAN Y B and TONG Qet al,when the alignment deviation along axes directions of X,Y,Zis 1mm and the rotation deviation of each axis is 2°.The proposed method effectively reduces the influence of alignment deviations on the thread pitch diameters,and can be used for two dimensional point cloud data by both contact and non-contact 2-dimensional scannings.