Research On Comprehensive Inspection Technology Of Dimensional And Form Error Based On Line Laser Vision

With the increasing degree of automation and modernization in society,the accuracy requirements of dimensional errors and form tolerances of workpieces in various industries are becoming higher and higher,and the measurement methods are becoming various.In the traditional contact measurement,CMM can not meet the demand of online measurement due to its expensive,relatively harsh environment and long measurement time.Non-contact measurement,on the other hand,has advantages such as small size of the measurement system and fast measurement speed.Therefore,this paper designs and builds a line laser rotational measurement system based on laser triangulation,writes the system program,and verifies the feasibility and practicality of the system by measuring different workpieces experimentally.The main structure of this paper is as follows:(1)The non-contact measurement techniques is investigated,and line laser vision measurement was selected as the measurement method in this paper.Two laser irradiation methods were compared,and the oblique irradiation type was selected as the irradiation method in this paper.The transformation of the 3D coordinates of a point in space from pixel coordinate system to world coordinates was derived,the form error calculation formula was theoretically derived,and a line laser rotary scanning measurement system was designed.(2)The internal and external parameters of the industrial camera were calibrated by using Zhang’s method and MATLAB camera calibration toolbox,and the images were preprocessed by using different filtering algorithms,and the weighted average method was selected for noise reduction of the acquired images.Several image segmentation algorithms were compared,and finally the image was selected to be segmented directly using global thresholding.(3)Several laser centerline extraction algorithms were compared according to the laser characteristics,and the Steger algorithm was selected to extract the laser stripe centerline for this paper.Based on the line laser measurement model derived and calibrated using the calibration plate for the line laser light knife plane and rotation platform,the light plane and rotation plane parameters were determined.(4)The measurement system platform was built,and the point cloud images of the workpiece to be measured were scanned and acquired.The main point cloud was determined by point cloud filtering and segmentation,and the dimensional and form errors of several workpieces of different sizes and materials were calculated based on the point cloud data using the least squares method combined with RANSAC algorithm and genetic algorithm.The error analysis of the data results is carried out to verify the rationality and practicality of the measurement system.