| Pulsed gas metal arc welding (GMAW) process has a wide range of current adjustment,suitable for all position welding, weld forming excellent characteristics. It is widely applied inthe manufacture of industrial production. However the performance of arc welding powersupply has put forward higher requirements. Soft switching arc welding power source is inaccord with the demand of pulsed GMAW welding. Now, the full-bridge soft switching arcwelding inverter modeling research is not system. In order to obtain optimal parameters ofsoft switch arc welding power supply in the design process, so it is very necessary to researchthe mode of arc welding power supply system. Based on full bridge soft-switching inverterarc welding power source model simplification, the equivalent small signal model is set up.The peak current control technology and phase-shifted full-bridge soft switching technologyis mutual integration, stability problem of phase inverter with soft switching is researched onthe peak current controlled mode. The analysis shows that slope compensation is necessaryconditions for inverter stability in the case of PWM duty ratio greater than50%. Above all,influence factors of dynamic characteristics for power supply are analyzed, and the boundarycurves of output characteristics for arc welding power supply is analyzed. This provides atheoretical guidance for welding supply development and optimization design of the controlparameters.The existing design problems of pulsed GMAW welding machine are analyzed, controlcircuit based on the DSP+ARM topology architecture is proposed. It realized functionanalysis and design of circuit by using modular methods, and the realization of software forcontroller is designed in detail. So a reliable platform for pulsed GMAW welding powersupply is established. It provides a basic hardware foundation for welding process research.Test results of power characteristic performances show that the designed pulsed GMAWwelding power supply can meet the practical needs.Through the model analysis of the pulsed GMAW welding system, main circuit andcontrol system simulation model are established based on the Matlab/simulink simulationenvironment and its extension S function establishes for pulsed GMAW welding power supply.The simulation model can effectively simulate the dynamic characteristics of special process for the actual arc welding inverter-dynamic arc load system. Control strategy can simulatethe real process of arc length dynamic adjustment based on simulation model of pulsedGMAW welding inverter and arc load system using S function. By introducing interferencecondition, simulation system can quantitative analysis the physical parameters variationmechanism and influence factors in pulsed GMAW welding process. It provides a new way tooptimize parameters of controller for pulsed GMAW welding inverter, verify new arc lengthcontrol algorithm and strategy.It has an important effect for welding technological properties, weld forming andwelding quality with different droplet transfer mode of pulsed GMAW welding. Droplettransition of ’One drop per pulse’ is the best choice to achieve effective, precise control ofdroplet transfer behavior. It comes to realize that I/I control method is best method to get ’onedrop per pulse’ based on analysis parameters selection of pulsed GMAW welding. Outputcharacteristics of constant current power supply are used during both peak period and baseperiod. Arc has not self regulation with output characteristics of constant current, so arc lengthmust be controlled in the process of arc welding. Double loop control strategy of cycle loopconstant current control and outer loop arc voltage control in one pulse period is proposed.Through average current-voltage model of a single pulse period, it is found that the controlstrategy based on double closed-loop arc length of the pulse period of the cycle average of theoutput characteristics has self-regulation role. Step up and down tests of arc length regulationshow that the theoretical analysis is correct through periodic average output characteristics.This provides a theoretical basis for pulsed GMAW welding robotic automation. |
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