REAL-TIME PREDICTION OF ELECTRODE EXTENSION IN GMAW

摘要

This paper details the development of an electrode extension model for the gas metal arcrnwelding process based on the process voltage. The full dynamic model for the electrode extensionrnis derived by combining a dynamic resistivity model with the voltage model. The electrodernextension model was found to be represented mathematically by a nonlinear, time-varying, secondrnorder ordinary differential equation. This model can be used in through-the-arc sensing and arcrnlength control systems. To experimentally verify the model, the process dynamics were excited byrna continuous sinusoidal variation of arc current. Using a constant current power source withrnelectrode positive, sinusoidal perturbations, of variable amplitude, were superimposed on therncurrent to allow direct measurement of changes in electrode extension, arc length, and total voltage.rnA high-speed video system was used in capturing the experimental electrode extension dynamics.rnThe model was verified by comparing frequency response of the model to frequency response ofrnthe real process. Agreement between simulations and experimental results was found to be veryrngood. The accuracy of this model was found to be approximately ± 0.6 mm which is consideredrnsuitable for process control applications.