Research On Visual Inspection System For Inner Surface Defects Of Tubular Parts

The defect on the inner surface of a tubular object is one of its quality points.Due to its limited internal space and insufficient light,conventional surface inspection equipment and methods are not applicable.At present,the manual visual inspection method with endoscope as the main tool is often used.There are also defects such as low detection efficiency and no quantitative detection standards.Therefore,it is meaningful to explore the detection methods of defects on the inner surface of tubular objects.The thesis has carried out the research on the opto-electromechanical detection system for the inner surface defects of the tubular objects based on machine vision technology for the slender tubular parts with inner diameter 15 mm ～ 29 mm,outer diameter 17mm～40mm,length 5mm～115mm and weight not more than 5kg.Key technologies such as uniformity of illumination,adaptability of materials with different diameters,and seamless stitching of circular inner wall images.The main tasks of the thesis are:1)The overall scheme of the inspection system for internal surface defects of tubular parts is given,the rotating module and the linear module are designed,the determination of key parameters and the selection of related hardware equipment are determined;2)A high-uniformity light source is designed,a set of equations are solved to design a free-form surface through equation solving method,theoretical analysis,and then the surface shape of the free-form surface is calculated through the software Matlab,and the combination of the quadratic lens is obtained,so that the light passes through the lens The group obtains a uniform circular and convergent light spot,which improves the uniformity of the light spot,thereby meeting the system lighting requirements;3)A liquid telecentric lens with a variable working distance is designed.First,the P/W method is used to determine the initial structure of the telecentric optical system,and then the telecentric system is optimized to obtain a telecentric lens that meets the requirements of the paper,and then integrate the liquid The lens is optimized for optical design to obtain a liquid telecentric lens,which can zoom in milliseconds and shoot images at different distances,which is different from conventional mechanical moving lenses up and down to shoot images at different distances;4)A seamless splicing method of circular inner wall images is proposed.The SURF-related image matching method is used to fuse multiple small field of view sequential images to obtain a complete circular binary morphology of the inner surface of the pipe;then according to the characteristic pixels of the defect Quantity,calculate the actual size of the defect.Finally,according to the set defect size threshold,the classification of defects and the statistics of the number can be realized.5)An opto-electromechanical inspection system for internal surface defects of tubular objects based on machine vision technology was built.The mechanical movement error of the system was analyzed,and experimental verification studies were carried out.The maximum radial error of the system was 0.265 mm,which satisfies the depth of field error of less than 0.5mm.Claim.