The Real-time Weldline Tracking Of A Grit-blasting Wall-climbing Robot Based On Double CCD

In the past,the derusting operations of the weld seam on the surface of the ship were carried out manually by the hand-held equipment.There are some obvious drawbacks in this operation,such as serious pollution to the surrounding environment,low recycling rate of the sand,high labor intensity,damage to the operator’s health and so on.With the incresing development of industrial automation and intelligent level,the development of a set of sandblasting derusting,sand recycling and other functions in a mobile robot system is in line with the current trend of building a modern industrial society.In order to promote the automation level of the mobile robot system and further enhance the autonomy of the wall-climbing robot,it is an inevitable trend to design and develop a weld seam tracking system based on mobile robots.In this paper,a real-time tracking system for mobile robot based on passive vision is studied.Firstly,a real-time tracking system of weld line is built based on double CCD,wall-climbing robot platform,LabVIEW software and MPE720 software,which is able to guide the wall-climbing robot to conduct sand blasting along the weld line.Then,a weldline image processing and feature extraction algorithm is proposed,including dynamic small window technique,median filter,local threshold segmentation(NIBLACK),area threshold filter,morphological operation,image thinning and deburring,edge line fitting of weld profile and extraction of weld centerline.Meanwhile,an effective recursive algorithm is proposed to remove the burr after weld image thinning.Based on the inherent parameters and historical information of the weld,some judging principles of the weldline are proposed,which ensures the accuracy of the weldline extraction.According to the camera parameters after calibration,the process of position deviation of mobile robot is discussed.In view of the particularity of vision system of double CCD,the corresponding processing strategies of weldline deviation are put forward.Finally,a Fuzzy-PID controller is designed.The Fuzzy-PID control simulating experiments of the straight weldline and the curve weldline shows that the control system has good response ability,high tracking performance and strong rectifying ability.And the real-time tracking process of the weldline is realized in a vertical ship wall weldline tracking experiment.The experimental results show that the weldline tracking precision is ±5mm.