| Punching is an important part of stamping technology.In actual production,due to the impact of punch wear,workpiece material and other factors,there will be problems such as low size accuracy of punching,location deviation and so on.At present,in the automatic production line,the method of manual sampling inspection is often used to inspect the punching quality.The efficiency of this method is low,and the inspection accuracy is greatly affected by humen factors.To solve this problem,an on-line inspection method based on vision for punching quality of large-size plate is proposed,which can replace manual sampling inspection and realize on-line inspection for punching quality of all products.The main research contents are as follows:Taking the " robotic flexible production system of lift car enclosure " of a company as the research object,the production process is analyzed,and the punching technology is studied.The workflow and the overall solution for the on-line inspection system of punching quality of plate are designed.In order to solve the problem that the view of camera is limited when the large-size plate is inspected,a two-dimensional motion inspection platform with dual vision is designed: a location device for plate is added to the original conveyor to ensure the reliable location of the plate in the inspection process;the mechanical structure of the inspection platform is designed,and the camera,lens and light source are selected according to the accuracy requirements of inspection of punching quality;the static analysis is carried out on the inspection platform to ensure that the deformation of the platform structure will not affect the inspection accuracy.A method of fast location for camera based on drawing information of product is proposed: the system uses the feature information such as arc,circle,line and point in DXF file of the plate to quickly extract the size information and location information of each processed hole on the plate;both are used to evaluate the inspection results,and the location information is also used for the location of camera;the motion path of camera and the fast and stable location of camera are very important to the inspection efficiency and accuracy,the inspection path of camera is planned by quintic polynomial,and simulated by MATLAB to achieve the goal of fast and stable location of camera.The inspection algorithm is studied: the camera is calibrated,and the flow of image processing is designed,including median filtering,linear gray-scale transformation,binary segmentation and Canny edge extraction;a model of coordinate conversion is designed,by which the location coordinates of all inspeced holes are based on coordinate origin of the plate,to inspect the hole location;a compensation algorithm of inspection error is proposed to reduce the influence of the installation error of camera motion platform,the deformation of the plate and the location error on the inspection accuracy of the system and further improve the inspection accuracy of the system.The experimental platform of inspection system of punching quality of plate is built to conduct the experimental verification of the inspection system: the true value of the feature to be inspected is obtained by the method of calculating the arithmetic mean value through multiple measurements;the error of the inspection data is obtained by comparing the visual inspection data with the true value,and the data error is analyzed to verify the feasibility and accuracy of the inspection system.The error compensation algorithm is verified by simulating,and the results show that the algorithm can improve the inspection accuracy of the system. |
