Design And Development Of Automatic Welding System For Pipe Fittings Intersecting Lines

In the machinery manufacturing industry,welding is a very important processing technology.With the development of robot technology and the increase of labor cost,more and more joint welding robots are applied to welding production.However,for the welding of space curve trajectory,it is difficult to calculate the pose of trajectory tracking and the accuracy is not high.In this paper,a design scheme of a four-degree-of-freedom welding robot for pipe fitting intersecting line was proposed,and a program for welding path data extraction,workpiece pose change and velocity calculation of each degree-of-freedom was developed based on the threedimensional model of welding parts.The mechanical system design and control system design were completed.The reliability and correctness of trajectory path tracking were verified through simulation and prototype testing.The expected design goal was achieved.The main research contents of this paper are as follows:(1)Put forward the overall scheme of the mechanical system in which the welding gun movement system composed of two degrees of freedom moving mechanism has no change in attitude and only changes in position,and the workpiece position and posture change system composed of two degrees of freedom rotating mechanism has cooperated with the movement.The overall control logic of the welding gun movement and the workpiece position and posture change has been drawn up.(2)The mathematical model of welding trajectory planning of intersecting lines was established,and the calculation method of welding gun movement and workpiece rotation and the calculation method of uniform welding speed were given.Using Grasshopper graphic algorithm editor provided by Rhinoceros,the program of extracting trajectory data,calculating X-direction and Z-direction displacement of welding gun,calculating rotation Angle of two degrees of freedom of workpiece,calculating velocity of each degree of freedom and motion simulation was compiled,and the corresponding data was output.(3)Taking linear module as moving unit,the mechanical structure of the welding gun moving system was designed.The double-frame structure with rotating axes directly driven by the motor was used as the workpiece position and pose conversion system,and the overall structure design of the mechanical system was completed.The control system architecture and hardware wiring diagram are designed,and the control system program is written according to PID control algorithm.(4)A small size test prototype was built,the trajectory tracking simulation of the prototype was completed,and the speed curve and theoretical welding speed curve of each motor were output,which verified the correctness of the mechanical system,control system and program designed in this paper.The research of this paper shows that the automatic welding of the intersecting line of pipe fitting can be carried out with the mechanical system of two movements and two rotations.The control system and software designed in this paper can accurately track the weld and maintain the required welding position.The speed of each degree of freedom can cooperate with each other to ensure the uniformity of the actual welding speed.