Development Of An Arc Welding Robot System Based On Laser Vision Sensing

Machinery manufacturing industry is the basic industry of the national economy,and welding technology is one of the key technologies of the machinery manufacturing industry.A country's welding technology level has gradually become an important indicator of its industrial and technological modernization level.At present,most of the welding work is done manually in our country,and the welding automation level is still very low.High-strength continuous operation and poor welding site environment makes the workers facing many potential threats.Efficiency of manual welding is low,and the consistency of welding products is poor,which makes the development of a flexible,autonomous and strong automated welding robot very important.In this paper,a set of arc welding robot system based on laser and image sensing is developed for the automatic welding of T-type stainless steel.The system consists of industrial computer,PLC,6-degree-of-freedom robot,automatic welding power source,laser vision system and other components.A kinematic model is established for the 6-DOF robot used in this paper.The coordinate transformation matrix is solved and the inverse kinematics analytic expression is deduced.According to its kinematics model,a method of torch attitude retention is proposed.The laser vision sensor system shoot the welding image through the CMOS camera.After the grayscale conversion,ROI selection,Gaussian filtering,Canny edge detection,Hough transform and a series of other processing,coordinates of the welding feature points in the camera are extracted out.According to the calibration parameters of the camera in the robot TCP coordinate system,the coordinates of the welding feature points in the robot TCP coordinate system are calculated.Combined with the coordinate transformation matrix of the robot,the coordinates of the welding feature points in the base coordinate system of the robot are finally calculated.A system control architecture which takes the industrial computer and PLC as the control core is proposed.The robot moves to the welding points according to the position given from the industrial computer.This paper presents a method of controlling an automatic welding power by PLC,which controls the parameter adjustment and monitor condition of welding power.The network communication based on TCP / IP protocol between industrial computer and the robot,and the serial communication between industrial compute and PLC based on programming dedicated communication protocol of PLC is designed and implemented.Software architecture and the control interface of the system are designed.Thermal deformation analysis in the welding process of T joint has been done,and the measures to suppress the thermal deformation are put forward according to the size of the workpiece.The theoretical value of the binding force and the critical restraint length is calculated,and then welding tooling is designed based on these factors.The arc welding robot system based on laser and image sensing is installed and debugged,and the experimental is carried out.The experimental results show that the tracking error of the welding system based on laser and image sensing is less than 0.96 mm,which is much smaller than that of the teach mode.This system can achieve automatic welding of T joint 316 L stainless steel with welding speed up to 24 cm / min,and the appearance of weld is good.