Research On The Measurement Method Of Shaft Parts Based On Laser Scanning Technolog

As rotary parts,shaft parts account for a large proportion in machinery manufacturing.In order to ensure the reliability of mechanical equipment,it is hoped to realize the rapid full inspection of the geometric size of shaft parts.Taking shaft parts as the research object,this paper adopts laser scanning technology to carry out measurement research on the typical characteristics of geometric size and cylindricity error.The specific contents are as follows:Firstly,according to the typical characteristics of shaft parts,the parts to be tested are designed.By analyzing the measuring demand and measuring index of the parts to be measured,a non contact measuring scheme based on laser 3D scanning technology is developed.According to the measuring scheme,a measuring system for shaft parts based on laser measuring instrument is designed and built,and the measuring system is calibrated.According to whether the part to be measured has shaft shoulder or not,the measurement of shaft segment length is divided into two types: the measurement based on plane fitting and the measurement based on geometric contour segmentation.For the measurement based on plane fitting,the algorithm of Least Median of Squares(LMed S)combined with Principal Component Analysis(PCA)was proposed to fit the shoulder point cloud plane.LMed S can obtain the ideal plane model in the point cloud data set containing noise and outlier interference,and PCA can fit the plane model to get the plane equation.In the actual measurement of parts,the fitting time of target plane is less than 0.06 s,and the average fitting time is 0.036 s,which realizes the rapid measurement of shaft length.The maximum error and average error between the measurement result and the standard value measured by the special measuring tool are 9μm and 8μm.The measurement accuracy is high and meets the requirement of measuring accuracy within 10μm.Aiming at the measurement based on geometric contour segmentation,a geometric contour segmentation method based on point cloud normal projection was proposed.In the actual measurement of parts,the error between the measurement result and the standard value measured by the special measuring tool was not more than 9 μm,and the measurement accuracy was also satisfied within 10 μm.The above experimental results indicate that the two measurement methods can achieve accurate and fast measurement of shaft segment length with and without shoulder.According to the characteristics of space cylinder,a cylindrical fitting algorithm based on the relationship between point and axis position was proposed for measuring the axial diameter of parts.The error range between the axial diameter measurement results based on this method and the standard values measured by micrometer outside diameter micrometer is 7μm 10μm,and the measurement accuracy is high,meeting the requirement of measuring accuracy within10μm.The measurement requirements of(blind)hole and(key)slot size are analyzed and converted into the position relationship between different geometric features on the shaft to achieve measurement.The cylindrical features of the inner wall of the hole and the plane features of the bottom surface were extracted and fitted by the point cloud minimum containment box.The error between the measurement results of the hole spacing of the(blind)hole and the length of the(key)slot and the standard value measured by the hole spacing caliper is no more than 0.04 mm,which meets the requirement of measuring accuracy within 0.05 mm.The error between the measurement results of(blind)hole spacing and(key)groove depth and the standard value measured by the depth micrometer is less than 8 μm,and the measurement accuracy is high,meeting the requirement of measuring accuracy within 10 μm.Aiming at the cylindricity error of shaft parts,the multi dimensional optimization function of cylindricity error was obtained according to the minimum region method,and the mixed particle swarm optimization and simulated annealing algorithm were proposed to solve the objective function.Two typical cylindrical data sets are simulated and compared with the results of hybrid particle swarm optimization,differential evolution algorithm and improved harmonic search algorithm.By comparing the algorithms,it can be seen that the hybrid particle swarm optimization algorithm and simulated annealing algorithm are stable and have higher accuracy than the other two algorithms.In the actual measurement of parts,the error between the cylindricity error and the standard value measured by the three coordinate machine is less than1.8μm,and the measurement accuracy is high,meeting the requirement of measuring accuracy within 2μm.In the actual measurement of conical Angle of parts,the estimated results of mixed particle swarm optimization and simulated annealing algorithm are between those of the CMM and the least square method.Compared with the least square method,it has good stability and high accuracy,and the error between it and the standard value measured by the CMM is less than 0.3°,which meets the requirement of measuring accuracy within 0.5°.The experimental results show that the hybrid particle swarm optimization and simulated annealing algorithm improve the accuracy of cylindricity error evaluation and cone angle estimation,and can effectively evaluate the cylindricity error and cone angle of shaft parts.The above experimental results verify the feasibility and effectiveness of the measurement method in this paper,which can provide certain theoretical basis and method support for the full size rapid measurement of shaft parts.