| With the development of economic and social intellectualization,the demand for electronic products is growing,the renewal cycle of electronic and electronic products is gradually shortening.The number of electronic waste,such as discarded household appliances and mobile phones,is increasing,and it has become a problem of environmental protection in the world.At present,most of the discarded circuit boards are treated by crushing and recycling precious metals and plastics.In fact,many electronic components on the discarded circuit board are still in good performance,far from the scrapping years of electronic components,and can be used again.The reuse of dozens of grams of chips,on the one hand,is the reuse of electronic components,which is beneficial to environmental protection and conservation of resources.On the other hand,its economic benefits are far greater than the economic benefits produced by the crushing treatment of tons of waste,which is conducive to promoting the technological progress of the reuse of electronic waste.Therefore,the research of nondestructive disassembly and recycling of electronic components of waste printed circuit boards has become a hot issue in the field of electronic waste disposal at home and abroad.To ensure the appearance and performance of the disassembled chip is intact,precise positioning and disassembly is the key.The thesis deals with the automatic location of chips in disassembly of electronic components in waste printed circuit boards.Firstly,according to the positioning requirements of discarded PCB patch elements,a machine vision system combining software and hardware is designed.The hardware part is composed of industrial camera,lens,image acquisition and transmission cable,light source,computer and so on.The software is divided into image acquisition,image preprocessing,template making,positioning / coordinate measurement and result output.Secondly,as the image collected by the camera can not be directly applied to the image processing of various functions,the image gray transformation,noise filtering and image enhancement are the important parts of the image preprocessing.The dissertation studies the classical image preprocessing algorithms,and analyzes their respective advantages and shortcomings,and gives the corresponding results.The effect of the algorithm is realized by programming.Thirdly,in order to measure the coordinates of the post patch components and require high positioning accuracy,the dissertation takes into account the influence of lens radial distortion,and establishes a nonlinear system model before positioning the patch components on the abandoned circuit board,and uses a calibration method based on LabVIEW to calibrate the camera.According to the calibration,the transformation relationship between the computer image coordinate system and the world coordinate system is determined.The reliability of the calibration accuracy is proved by the calibration experiment analysis.After the image preprocessing and calibration information are obtained,the template matching location algorithm based on the gray level is selected according to the feature of the patch element.In order to ensure the template image can also be successfully matched after the image is rotated,an improved template matching location algorithm is proposed.In order to improve the positioning precision and accuracy,generating the template matching in different directions by rotating template image in the matching positioning process.Finally,the system software designed by the dissertation is used to study the location of the patch components.The experimental results show that the location time of the patch element is less than 0.5s,the positioning precision is high and the location accuracy is over 90%.At the same time,the control system of disassembly platform of the discarded PCB patch is designed.The reliability of the positioning precision is further verified by the disassembly experiment based on the vision location coordinate. |
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