Simulation And Experimental Study Of Joint Recognition And Tracking System In Robotic Welding

Robotised welding,which has high flexibility and efficiency,is widely used and rapidly developed in industrial applications.However,there still are some constrains such as part tolerances,heat induced deformation and inevitable fixture errors,which can affect the laser beam positioning to deviate from joint centre and lead to poor welding quality.In order to ensure a high welding quality,a joint tracking system is needed to track the weld joint in real time to keep the focus of laser beam following the weld joint consistently.This paper presents a joint tracking system which based on CMOS vision camera,structure light sensor,industrial computer and ABB welding robot,the system has been used in joint tracking simulation and welding experiments,results show that the joint signal can be extracted and processed in real time,the joint center can be obtained clearly after processing;the time efficiency of each part of the algorithm can be got and the total time of the algorithm is 66.86 ms,the bottleneck of the algorithm is that the joint center detection part,the required time is 28.06 ms,accounting for 42% of the total time,this part can be optimized by reducing the scanning area;the coordinates data of detected joint center from the image stream has good stability and repeatability.The repeatability of robot motion control is simulated under three different paths straight line,fold line and curve.Through the evaluation of the simulation results,the error and precision of robot motion repeatability can be obtained,the error under three kinds of path of robot motion is very small,even in the curve path which has the maximum error,the error is only 0.04 mm which means that the robot has high precision and good repeatability;The welding workstation and welding production line are simulated according to the different welding path of welding based on Robotstudio,including path optimization,collision detection and cooperative motion,DES model of welding production line is simulated based on Plant simulation Simulation,the actual working conditions of the robot workstation with different functions are simulated in the model,there are certain guiding significance for actual production;the joint tracking system which based on linear structure light sensor is used for welding experiment,the welding experiment is under three different paths(straight line,fold line and curve),the deviation at different position under three kinds of path is evaluated and quantified,there are the minimum error under straight line path while there are the maximum error under curve path,the error amount is related to curvature under fold line and curve,the greater curvature,the greater the error,which is mainly due to robot motion error and the identification error caused by robot sensor..