Study On Key Technologies Of Welding Seam Tracking Applied In Thick Plates Based On Weaving Arc Sensing

Multi-pass welding has been becoming increasingly applied to welding thick plateswith the rising demand of large welded structure in the fields of shipbuilding, waterconservancy, thermal power, building, pressure vessel, the petroleum chemicalindustry, engineering machinery, etc. At present, few welding robots applied in thickplates welding while manual and semi-automatic arc welding are still widely used inChina. A main reason for this is that the domestic welding robots is hard tocompensate in real time the deformation of base metal and welding seam、the error ofworkpiece machining and the interference effects in multi-pass welding process.One of critical factors for ensuring welding robots acquire good wielding quality andexcellent technological adaptability is to develop accurate seam tracking technology.Therefore, the further study of accurate seam tracking technology for thick plates willbring positive and profound influence for the application of automation weldingtechnology in the field of large steel structure.Weaving arc technology was applied to seam tracking for multi-pass welding in thickplates in this dissertation. First, direct at two typical form of bead in multi-passwelding in V-groove, the thesis respectively built mathematic models of arc length fortwo types of welding bead, then modeled and simulated the weaving arc sensing partin MATLAB/SIMULINK. Through the simulation analysis of welding current signalsas well as analysis of the results of welding experiments, the paper illustrated theeffects of some main parameters such as welding deviation，dip angle of weldingtorch，and swing to the welding current at last. The simulation calculation results areconsistent with the experiment data, which proves the feasibility and validity of thismodel.A welding oscillator satisfactory for seam tracking in multi-pass welding has beendevised. In addition, a new approach of weaving-arc position detection has beenproposed in this paper and the relevant appliances and hardware circuits have alsobeen designed. Then, the Proteus circuit simulation software has been used tosimulation analysis、debugging and optimizing before selecting the parameters of the hardware circuits. Experiment demonstrates that the new approach has favorableperformance of producing stable and precise positioning pulse which can satisfies thedemands of system.Aimed at the model of arc weaving sensing, a new method, specially designed for twotype of representative bead in multi-pass welding, has been successfully developed.The experiment proved that this method is easy for programming, that it caneffectively resolve the dilemma of seam tracking for multi-pass welding in thickplates with V-groove and that it provides for welding robots the theory basis ofachieving expected target for seam tracking in multi-pass welding.A welding tracking system platform which use V-groove thick plates as subject hasbeen built. The experimental evidence obtained has indicated that the system couldaccurately recognize the welding deviation with stable operating in the multi-passwelding of thick plate, and that the precision of welding tracking can satisfy therequirements of multi-pass welding.