Free Surface Reconstruction Based On Machine Measurement System Combining Line Structured Light With Probe

With the development of advanced manufacturing technology and the three dimensional scanning and reverse engineering technology are widely used in China.The technical connection between digital manufacturing and digital measurement is more closely.At present,the measurement includes contact measurement,non-contact measurement and multi-sensor integrated measurement.Among them,the measurement accuracy of contact measurement is high,but the efficiency is low;the measurement efficiency of non-contact measurement is high,but the precision is low.The composite measurement is often used to locate or plan the contact measurement path by the surface of non-contact measurement data,but there is repeated measurement,and it can not truly realize the interaction of multi-source data.In view of the above problems,a kind of compound machine measurement based on five axis machining center combining vision measurement with contact measurement is presented.It can make full use of the high efficiency of the line structure optical vision measurement and the high precision of the contact measurement of the probe.The linear structured light vision data is used as the initial surface data,and the high precision point of the machine contact measurement is constrained by the initial surface value point.The two kinds of data are fused based on the energy optimization method,and then the free curve is reconstructed.The main contents of the paper are as follows:(1)Extract the two-dimensional coordinates of the light stripe center of structured light.The characteristics of the traditional image segmentation algorithm are analyzed.The image segmentation algorithm based on the genetic algorithm and the two-dimensional best histogram entropy method is used to separate the light stripe image from the background and noise in order to facilitate the extraction of the center of the light.The optical strip center is obtained by continuous etching of the light bar image based on the morphological thinning algorithm.The morphological thinning algorithm and the center extraction algorithm of the fitting resampling light bar are used to solve the problems of broken lines and branches in the process of the center extraction of light bars,and re-sampling to obtain the complete two-dimensional coordinate data of the center of the light strip.(2)Create the initial surface based on line structured light.First,the image center two-dimensional data obtained by the obtained visual measurement system is converted to the world coordinate system to get the three-dimensional coordinate point cloud of the cross section of the measured object.Secondly,the reverse engineering software Imageware is applied to the point cloud data alignment,the data reduction and so on.Finally,B spline surface is used to realize initial surface modeling based on pre processed point cloud data.(3)The reconstruction of free form surface based on energy optimization is realized.The energy model of the elastic deformation of the thin plate is taken as the objective function,the energy function mathematical model is constructed with the contact type point as the type value point constraint,and the energy function of the B spline surface and the constraint of the type value point are dealt with.The grid method is proposed to solve the large integral in the energy model to help the subsequent energy model.The energy function optimization algorithm based on genetic algorithm and nonlinear programming is used to solve the energy model,and then the free form surface reconstruction is realized.(4)Based on the above-mentioned theoretical achievement,taking the five axis machining center as the experimental platform,combining the line structured light vision sensor with the probe to build a compound machine measurement system,and taking the free form surface as the experimental object,the experiment is carried out in the machine contact measurement and the line structure optical vision measurement and calibration experiment of visual measurement system.The experimental data are processed on the basis of the algorithm of the thesis,and the fitting error of the reconstructed surface before and after the deformation of the free surface is analyzed and compared to verify the validity of the proposed algorithm.