Nonlinear bounded feedback control of mold level for high speed slab casters

A serious challenge for modern casters is to satisfy demands of high production rates with high quality standards at profitable levels. This is specifically the case of thin slab casters where very high casting speeds are usually employed. However, due to the non self-regulatory nature of the mold filling operations there are difficulties to stabilize the liquid steel level in the mold. This is particularly important if we take into consideration that liquid steel level fluctuations lead to surface defects in slabs and frequently to dramatic breakouts that hinder the continuity of the operations of a some given plant. Consequently with this situation, in this paper we have developed a nonlinear and a three input-three output feedback bounded control algorithm to simulate and to control liquid steel flow in conventional slab casters and thin slab casters. The term bounded is related to the size of the nozzles of ladle and tundish so that the algorithm fixes its own boundaries. The existence of bounds may originate saturation problems. Nevertheless, the present algorithm has the capability of making the levels to converge to their set point values.