Study Of Disk Slitting Clearance Detection Based On Machine Vision

Machine vision is the combination of image processing technology, automatic control technology and artificial intelligence technology, with the continuous development, machine vision technology is more widely used in industrial automation production system, which makes industrial automation a further improvement of level. Measurement is an important industrial application of machine vision technology, that uses optical non-contact detection method instead of the traditional contact detection method, which not only solve the environment where human can not work, but also greatly improve the working efficiency and make products on-line detection, automatic controlling be possible.Disc slitting is a pair of upper and lower arrangement shear blade which used to cut sheet metal, and disc slitting axial clearance is the key process parameters for determining sheet metal’s section morphology and size shape accuracy when cutting sheet metal, so it should be controlled strictly. At present factories still use the traditional tools such as micrometer or feeler to detect disc slitting axial clearance, which leads to not only low working efficiency and detection precision is difficult to guarantee, So the paper uses machine vision technology to research on disc slitting axial clearance of non-contact detection. Main research contents include:Firstly, according to the detection requirements in this paper, determine the main optical hardware of machine vision system, and set up disc slitting axial clearance detection test bench; Secondly, lens have a certain degree of distortion because of itself physical properties, which leads to image distortion and affects industrial detection, So An algorithm that using elasticity and finite element deformation for image distortion correction is put forward; Thirdly, in order to reflect the disc slitting’s actual structure situation, do design disc slitting simulation structure and disc slitting axial clearance adjustment structure, and at last finish disc slitting clearance work through machine vision system that be set up.First of all, according to disc slitting structure, ordinary industrial camera can not be guaranteed to obtain consistent magnification object image, but telecentric lens can make detection target have a consistent image magnification within a certain distance due to its parallel optical path design, so telecentric lens is selected in this paper; and at the same time, the detection work in this paper is for small field, and target image should have obvious edge features, so the paper selects 1/2" CMOS IDS industrial camera and parallel light source, and the work field for this paper is 8mm × 6mm. Then set up disc slitting axial clearance detection test bench with the selected optical hardware.Secondly, when using machine vision system for image acquisition, Lens has a certain distortion because of itself physical properties, which leads to image distortion and do harm to detection precision, so image distortion must be corrected. An algorithm that using elasticity and finite element deformation for image distortion correction, which uses planar chessboard as calibration template, is put forward, according to the Mathematics thought that using finite element nodes displacement for calculating any other point’s displacement within the element, Then regarding checkerboards in the chessboard template as finite element quadrilateral units and checkerboard corners as quadrilateral unit nodes, Thus do correct the checkerboard distortion image point by point through the method that using checkerboard corners’displacement for calculating the another points’displacement within the checkerboard, and at last correct the chessboard template distortion image.At last, use optical method to detect the disc slitting target image clearance, and according to the disc slitting target image that has been obtained, use vertex scanning method to extract disc slitting edge points, so as to realize the calculation of disc slitting clearance in the image coordinate system, and then finish camera calibration by using chessboard, so the image coordinate and word coordinate corresponding relation is established, and in this way the calculation of disc slitting clearance physical size can be done, and in the end the detection work in this paper is finished.