Research Of Rectangular Welding Seam Tracking By The Welding Robot Based On The Rotating Arc Sensor

In shipyard,steel structure workshop and crane manufacturing enterprises,a lot of rectangular fillet welds are needed to be welded.Because the size of the rectangular fillet weld changes and the working space is narrow,the stationary mechanical arm or the automatic welding car can not finish welding the complex welding seam automatically,so rectangular fillet welds are still welded by the manual welding.There are arc light,splash and poisonous gas,and the working environment is very bad,so those seriously affect the health of workers and the welding quality.Therefore,it is necessary to develop a small and light autonomous mobile welding robot to automatically realize the tracking and welding of rectangular fillet welds,and improve the welding quality and efficiency at last.The system and the kinematics model of the welding robot have been studied in this paper.The whole system contains the welding system and the tracking system,and they have been studied.Various sensors for the welding robot contain the hall current sensor,the arc speed sensor,the rotating arc sensor,the ultrasonic sensor and the anti-drop sensor.The mathematical model of the space attitude for the arc welding gun based on the rotating arc sensor has been studied,and this mathematical model can be determined by identifying the horizontal deviation that the arc welding gun deviates from the welding seam,wire extension,the inclination angle along the welding direction and the inclination angle in the vertical plane.The kinematics model of the welding robot has been analyzed,and the trajectory planning for the welding robot and the tracking for the welding seam have been studied.Filter,deviation identification and control algorithm have been studied.Because the welding arc is unstable,the feeding speed of the welding wire is not a constant and other disturbances,there are a lot of noises in signals collected by the rotating arc sensor,so the wavelet filtering and the threshold processing have been used to remove most of noises in the sampling currents.The method of the principal analysis has been studied,and the horizontal deviation and the inclination angle of the arc welding gun along the welding direction have been computed out after the decoupling.By using the principal analysis,recognition accuracy of the horizontal deviation and the inclination angle has been improved.At the same time,the deviations of wire extension and the height deviations of the arc welding gun have been identified by using the pattern recognition algorithm.By using the combination algorithm of the fuzzy control and the expert system,identification and tracking of space curved fillet weld have been realized based on the coordinated movement among the horizontal and vertical sliders,two wheels.The tracking algorithm of the circular fillet weld has been studied.When there are the posture deviations that the welding robot is relative to the welding seam,the posture deviations can be eliminated by rotation of the welding robot based on the differential motion of two wheels.When the posture of the robot is adjusted,it is also need to ensure the tracking accuracy of the welding seam,so it is necessary to study tracking and welding of circular fillet welds,this study can not only ensure the tracking precision of fillet weld,but also eliminate the posture deviations that the welding robot is relative to the welding seam,and the tracking algorithm of the circular fillet weld is conducive to the tracking of the rectangular fillet weld.The tracking algorithm of the circular fillet weld mainly contains path planning of the welding robot,implementation of the tracking and welding algorithm of circular fillet welds,and the tracking and welding experiment of circular fillet welds in the laboratory and the factory,and path planning of the welding robot mainly contains path planning of the circular trajectory and path planning of tracking circular fillet welds.The tracking algorithm of right-angle fillet welds has been studied.According to some constraint conditions including welding speed,position and posture of the welding robot,and welding trajectory,path planning of the welding robot for right-angle fillet welds tracking has been researched,and the motion velocities of two wheels,the horizontal slider and the vertical slider have been obtained.The recognition algorithm of the inclination angle along the welding direction has been studied,and the identification algorithm of the cross point of the right-angle fillet weld has been researched by using the pattern recognition.The realization algorithm of right-angle fillet welds tracking has been builted,the welding and tracking experiment of the right-angle fillet weld has been carried out by using the design algorithm.The tracking algorithm of rectangular fillet welds has been studied.The mathematical model of the rectangular fillet weld has been established,and one rectangular fillet weld is divided into four right-angle fillet welds and four linear fillet welds.The tracking algorithm of linear fillet welds has been studied,and this algorithm contains path planning,identification of inclination angles along the welding direction,the control algorithm of linear fillet welds tracking,and realization of linear fillet welds tracking.By combining the tracking algorithm of right-angle fillet welds and the tracking algorithm of linear fillet welds,the tracking algorithm of rectangular fillet welds has been designed by using the high-level planning of the expert system.Finally,the tracking experiment of rectangular fillet welds and the welding quality test experiment have been done.The tracking experiment of rectangular fillet welds contains the welding experiment and analysis of experimental data,and the welding quality test experiment contains tracking precision of fillet welds and mechanical properties of the welding specimen.At last,the welding experiment of the rectangular fillet weld has been carried out at the production site of Jiangzhou union shipbuilding company,and experimental results showed that the rotating arc sensing robot based on the proposed algorithm could track rectangular fillet welds steadily,accurately and rapidly.