High-power AC Square-wave Submerged Arc Welding Arc Voltage Stability Control

AC square wave SAW has the advantages of zero crossing fast, no magnetic blowand high weld deposition rate, but the high-current high-speed arc welding process isinstability,the current and voltage output waveform are deformed, this phenomenon,can affect weld quality. the more likely the arc instability,.the more prone to a varietyof weld defects such as undercut and hump, especially in high current (1000A abovegrade) AC square wave welding applications.The application research abouthigh-power AC square wave SAW arc stability control has important theoretical andpractical engineering significance,which can solve the problems of high power ACsquare wave SAW arc instability and poor weld,at the same time maximizing theadvantages of AC square wave SAW.Based on the analysis of relationships between the electrical parameters of arcsystem during the submerged arc welding process and mechanical motion, the papersestablished a mathematical model of arc length of SAW process which with constantcurrent characteristic, and on this proposed high-speed high-power AC square waveSAW stable arc process control strategies, and designed speed wire arc length controlsystem based on arc voltage feedback, fixed and improved function and performanceof speed wire arc length control system which is based on arc voltage feedback byexperiment. The main contents are as follows.Firstly, to establish mathematical model of arc length of SAW process whichwith constant current characteristic; dynamic equilibrium relationship between heatmechanism and wire feed under different specifications,wire high-current and arcwaveform is researched; and disclosed the influence of positive and negative halfwave amplitude value, the conduction time ratio, frequency and arc voltage.Secondly, the paper has leaded into fuzzy control strategy according to the arcvoltage characteristics of AC square wave SAW, studied high-power AC square wavehigh speed submerged arc process arc stability controller based on fuzzy control. Thepaper also has gave out a fuzzy controller design steps and selected parameters offuzzy controller combined with the variation of AC square wave arc voltage.Thirdly, the paper has researched a digital control system of arc length which isbased on arc voltage feedback and wire speed. It has designed a arc voltage digitalcontrol system which is based on ARM processor as the core, the control system includes hardware and software two parts, hardware module is made up ofSTM32RB10processor, the main circuit of wire feed speed, driver circuit, arc voltagesignal acquisition circuit, protection circuit and other components, Software modulesis made up of the main program, subroutines arc and ending arc subroutine, samplingsubroutine, PWM generation subroutines. The paper has found out way to achieve arcfuzzy control algorithm in the ARM processor.Fourthly, the paper has established a simulation model of AC square wave arcvoltage feedback loop wire feed speed control performance by using SIMULINK ofMATLAB, designed solp weld test, respectively comparative studied the effect of arcvoltage control under the PID control and fuzzy control. The simulation andexperimental results show that the fuzzy control system designed played a good rolein the control of arc length and its performance is better than PID control wire feedingsystem, with more flexibility.