Robust mould level control

In the first years of production since 2000, the caster of the Direct Sheet Plant in Umuiden experienced unstable oscillations in the control of the mould level. This paper reports on the research that was conducted to find the cause of and solution for this problem. For that purpose, a 1:1 scale water model was used. From this scale model, it appeared that the oscillations were due to surface waves induced by stopper movements. To model the effect of the surface waves, a simple standard simulation mould level model was extended by a heuristic wave model. Using this model, a robust stable mould level controller was designed. This new controller has proven to be successful since its implementation in 2002.