Penetration Closed-loop Control Of TIG Welding With Filler Wire For Thin Stainless Steel Plate Based On Visual Sensing

In the wire-filling TIG welding process with a reserved gap,in order to obtain a weld with good frontside and backside forming quality,it is often necessary to form a fusion hole.The existence of the fusion hole can ensure that the welding arc passes through the gap to transfer the arc heat to the backside of the workpiece,realizes single-sided welding and double-sided formation with lower heat input.In manual welding,the welder can control the forming quality and penetration of the weld by controlling the dynamic characteristics of the fusion hole.Therefore,the research on the stable control of the fusion hole has important theoretical and practical application value for the welding production of oil pipelines,pressure vessels and other welding production that require single-sided welding and double-sided formation process.In this paper,the TIG welding with filler wire for thin stainless steel plate is taken as the research object,and the TIG welding experimental platform with TIG welding system,motion control system and information sensing system as the core is built.The information sensing system includes an electrical signal acquisition system and a visual sensing system,which are respectively responsible for the acquisition of electrical signals during the welding process and the acquisition of images of the frontside and backside fusion holes.According to the grayscale characteristics of the frontside and backside fusion hole images,the corresponding image processing programs were designed based on MATLAB software,and a relatively accurate fusion hole edge was obtained,and the characteristic parameters of the fusion hole were defined and extracted.Then the visual sensing system is combined with the image processing algorithm to realize the real-time acquisition and processing of the fusion hole image.Based on the electrical signal of the welding process and the image of the fusion hole,the thermodynamic analysis of the formation process of the fusion hole was carried out.The influence of different process parameters(welding current,welding speed,wire feeding speed)on the dynamic behavior of the fusion hole was explored.It is found that the size of the fusion hole always increases with the increase of welding heat input,and decreases with the increase of the amount of filler metal;when the process parameters are stepped,the width of the frontside fusion hole has the fastest response to the wire feeding speed,the welding current is the second,and the welding speed is the slowest.Based on this,this paper establishes a control strategy that takes the width of the frontside fusion hole as the output of the control system and the wire feeding speed as the input of the control system.The manual control of wire feeding speed is used as the excitation signal.While controlling the stable existence of the fusion hole,the width of the frontside fusion hole can be changed as much as possible,the dynamic change data of the wire feeding speed and the width of the frontside fusion hole can be obtained.Using the NARMAX model as the system identification model,the recursive extended least squares method is used for system identification,and a more accurate system model is obtained.A first-order linear active disturbance rejection controller(LADRC)was designed with the first-order system as the controlled object,the controller and the system model were imported into Simulink to simulate the welding process and adjust the parameters of the controller.Appropriate controller parameters are obtained through simulation,and the performance of the controller is also verified.The variable gap control experiment was further designed,and it was verified by the experiment that the size of the fusion hole during the welding process was relatively stable,a better weld formation was obtained,and the penetration control of the TIG welding process of the fusion hole type filler wire is realized.