Research On The Technique Of The Cap On Steel Drum Cover Assembled By Robot Based On Machine Vision

In recent years,with the progress and development of science and technology,automatic assembly technology has been more and more widely used.In the production of steel drum,assembly of screw cap on steel drum cover is a very important process of the steel drum production line,and directly affects the overall closure of steel drum.In order to improve the automation of the steel drum production and solve the problems of low production efficiency and poor assembly quality in manual assembly of screw cap on steel drum cover,the automatic assembly technology of screw cap on steel drum cover was studied.A automatic assembly system of screw cap on steel drum based on machine vision was proposed,and a special end effector was designed.The system has been realized the automatic assembly of screw cap on steel drum cover.First of all,according to the actual production requirements,the overall scheme of automatic assembly system for screw cap on steel drum was determined.The Eye-to-Hand visual control scheme based on location and the thread assembly scheme based on torque control were determined by comparative analysis.At the same time,the hardware involved in the system was selected and the action flow of the automatic assembly system of screw cap on steel drum cover was defined.Secondly,the visual localization algorithm for screw cap on steel drum cover was studied,and a center localization algorithm for screw cap on steel drum cover was proposed.The outer contour curve of screw cap on steel drum cover was extracted based on corrosive morphological gradient by image preprocessing,Laplace linear sharpening filter and morphological hole filling of processed image,and the center location of screw cap on steel drum cover was realized.In addtion,the application of Hough transform in line feature extraction was studied and a line detection algorithm based on improved random Hough transform was proposed aiming at the problems of standsrd Hough transform in line feature extraction.The superiority of the improved algorithm in extracting straight line feature was verified through comparative experiments.The algorithm was applied to extracting straight line festures inside screw cap on steel drum cover,and the angle of screw cap on steel drum cover was determined according to the oblique angle of the extracted straight line.Thus the complete position and posture information of screw cap on steel drum cover were obtained.At the same time,the imaging geometric model of camera,the internal and external parameters and the commonly used hand-eye calibration in industry were studied,and the nine-point method was used to calibrate the parameters of hand-eye system.Then,the special end effector for automatic assembly of screw cap on steel drum cover was studied based on the general scheme and the internal structure characteristics of screw cap on steel drum cover.A special end effector with independent power source and built-in torque sensor was designed,which integrated vertical action and pick-up action,and realized pick-up and fixed torque assembly of screw cap on steel drum cover.At the same time,the calibration algorithm of robot tool parameters was studied.The robot tool parameters were calibrated by TCP multi-point calibration method.And the calibration accuracy of the algorithm was verified by 80 mm standard cusp’s TCP multi-point calibration experiment.Finally,the upper computer software of the automatic assembly system was compiled by using C# high-level programming language and modular programming method based on Visual Studio 2010 development platform.The upper computer of the system was divided into four parts: communication module,calibration module,image acquisition and image processing module.The robot motion control program and end effector control program were compiled.And the communiaction with two lower computers was realized.The system simulation experiment platform was built based on the related hardware according to the general scheme of automatic assembly system for screw cap on steel drum cover.The upper and lower computer programs were compiled,the relevant parameters obtained through hand-eye calibration and TCP calibration.Automatic assembly experiments for screw cap on steel drum cover were carried out based on the simulation experiment platform.The experimental results showed the automatic assembly system for screw cap on steel drum can replace manual operation to complete screw cap on steel drum cover’s automatic assembly,and the system was stable and reliable.The efficiency of steel drum production and the automation of enterprises were improved.