1996 Volume 14 Issue 1 Pages 99-107
A nonlinear model has been developed to describe the relationships between the output (welding current and voltage) and the input (torch height) of through-the-arc sensor (simply called arc sensor) in DC MIG/MAG welding in open arc mode, and it is expressed by following five equations:
Ut=uao+(Ra+Re)I+(Eai+aiI)(Lt-Le)
LwdI/dt+(Ks+Rc)I+Ut=Us
dLe/dt=Vf-AI/(1-BJe)
Je=∫t t-ΔtI2(τ)dτ
Re=∫Le o r(Jz)dZ
All values of the parameters in the model were identified in the case of welding with both mild and stainless steel wires (1.2 mm diameter) and the shielding gas of 100%Ar. The simulated results based on the model have shown quite good agreements with the experimental.
On ther other hand, a linearized model of the arc sensor has also been drived from the nonlinear model under the hypothesis of any variable only showing a smaller variation around a given operating point, and it's form is shown as follows:
dUt/dt-Kw1dI/dt-Kw2dLe/dt=Kw3dLT/dt
Lwd2I/dt2+Kw4dI/dt+Kw2dLE/dt=-Kw3dI/dt
d2Le/dt2+Ke1dLe/dt=-Ke2dI/dt
Of course, some other features, for instance, the dynamic characteristics of electrode wire melting in GMA welding have also been made clear by the present work.
