Neural network prediction of the shunt current in resistance spot welding

An error back propagation(BP) neural network prediction model was established for the shunt current compensation in series resistance spot welding.The input variables for the neural network consist of the resistivity of the material,the thickness of workpiece and the spot spacing,and the shunt rate is outputted.A simplified calculation for the shunt rate was presented based on the feature of the constant-current resistance spot welding and the variation of the resistance in resistance spot welding process,and then the data generated by simplified calculation were used to train and adjust the neural network model.The neural network model proposed was used to predict the shunt rate in the spot welding of 20# mlid steel(in Chinese classification)(in 2.0 mm thickness) and 10# mild steel(in 1.5 mm and 1.0 mm thickness).The maximum relative prediction errors are,respectively,2.83%,1.77%and 3.67%.Shunt current compensation experiments were performed based on the neural network prediction model proposed to check the diameter difference of nuggets.Experimental results show that maximum nugget diameter deviation is less than 4%for both 10# and 20# mlid steels with spot spacing of 30 mm and 50 mm.