Research On Surface Measurement System Of Complex Parts

The function of modern industrial products is becoming more and more abundant,which brings the miniaturization and complexity of the parts stucture.With the progress of production technology,the ability of enterprises to inspection also need to be improved.The quality of parts is the guarantee of product quality.Therefore,enterprises put forward rapid,accurate and automatic measurement requirements.In order to measure the geometric accuracy of parts,it is necessary to reconstruct the parts,and then the dimension data and shape and position data of parts are obtained.At present,the existing research is mainly focused on the acquisition of three-dimensional data,and there is little work on the evaluation of the acquired point cloud data and the actual product quality.Based on related projects of Luxshare Precision Industry Co.,Ltd.,and based on noncontact optical measurement,combined with mechatronics technology,a set of measuring devices for complex parts is designed in this paper.The research contents of this paper are as follows:First of all,this paper analyzes the research status of 3d measurement at home and abroad as well as the background of the project is put forward,and the experimental comparative analysis of all kinds of 3 d measurement way,demonstrates the feasibility of combining of 3 d measurement and automation,on the basis of the project cost,the need of measuring requirements and to beat eventually choose the combination of 2d and 3d optical measurement data acquisition mode.Then,studied the methods of the image filtering and edge extraction;the least square method based on RANSAC is used to fit the ellipse and extract the coordinates of the calibration plate;the initial value of linear transformation is obtained by Zhang Zhenyou calibration method,and then the nonlinear optimization is carried out.The average error of reprojection is 0.04 mm.Phase unwrapping is performed by four-step phase shift and Gray code;Finally,carryied out the calibration experiment of the system model.Secondly,in order to realize automatic detection.In terms of structure,according to the material characteristics and shape characteristics of the parts,the loading fixture and reclaiming mechanism are designed;In terms of hardware,the selection of camera and optical machine is completed;In terms of software,the upper computer interface and algorithm are completed.Finally,the data collected by the camera is processed,and a sub-pixel fitting circular hole calculation method is proposed for 2D images;For the data collected by 3D camera,due to the outliers on the edge of the point cloud,the traditional algorithm of calculating the size,flatness and coplanarity of the point cloud can not meet the requirements of measurement accuracy.By analyzing the causes of data errors,an optimized algorithm of calculating the size,flatness and coplanarity is proposed.Finally,the paper takes complex parts as the measurement object to verify the accuracy of the system.In many measurements,the number of holes on the surface of the parts is consistent with the actual situation,the maximum fluctuation value of dimension and caliper measurement value is 0.02 mm,the maximum fluctuation value of flatness measurement is 0.007 mm,and the maximum fluctuation value of Coplanarity Measurement is 0.013 mm.The system has high measurement repeatability and meets the needs of the part measurement.