The Study For The Marine Pipe Physical Dimension Measurement System Based On Machine Vision

Bent pipes are widely used in aerospace, shipbuilding, automobile and other industrial areas, served as connection, control, turn, shunt, support, and other important roles.Due to the pipe rebound in NC machining, analytic method and numerical method were useless to correct errors.Currently,The best compensation method is to measure directly in the processing site,then,compare the measurement results with the design drawing data,feedback the error to the pipe bender,modify the NC codes, allow subsequent processing parts in accordance with the drawings as soon as possible to meet the precision requirement, reduce the processing cost.Based on the requirements of the subject, we design a machine vision based non-contact measurement systems.Considering the bending space structure,we uses three-dimensional binocular stereo vision measurement technology:first,build a set of image acquisition hardware system based on binocular stereo vision measurement principle, including the selection of camera, lens, image acquisition card and lighting system design, etc.; and then combined with the specific environmental problem, by learning a system camera calibration,determine the selection of calibration method based on binocular stereo Open CV image processing system, the method is simple and high precision; in the image processing section, first of all to get high quality filter pretreatment bend image, then take advantage of the edge detection canny operator to locate coarsely after the space moment method combining unit circle edge of the image sub-pixel positioning, then extract center axis of the edges,finally by using polar constraints on the image based on the center axis of the stereo matching,combined with the principle of binocular stereo vision calculate the three-dimensional coordinates of matching points, so as to realize the measurement of geometric parameters of pipe bending.According to the topics given range of diameter ?89mm-?219.1mm,maximum bending angle of 195 °, the bending radius R=3D bend large metal,selecting three groups of different parameters pipes to test, pipe diameter,bend angle and bending radius results were achieved the accuracy within0.02 mm, 0.2 ° and 0.15 mm, to prove that the measuring system meets the requirements of the subject. Finally, analyze the influence factors of the measur-easurement system, and give some corresponding solutions.