This article presents a new system to control secondary cooling water sprays in continuous casting of thin steel slabs (CONONLINE). It uses real-time numerical simulation of heat transfer and solidification within the strand as a software sensor in place of unreliable temperature measurements. The one-dimensional finite-difference model, CON1D, is adapted to create the real-time predictor of the slab temperature and solidification state. During operation, the model is updated with data collected by the caster automation systems. A decentralized controller configuration based on a bank of proportional-integral controllers with antiwindup is developed to maintain the shell surface-temperature profile at a desired set point. A new method of set-point generation is proposed to account for measured mold heat flux variations. A userfriendly monitor visualizes the results and accepts set-point changes from the caster operator. Example simulations demonstrate how a significantly better shell surface-temperature control is achieved.

A control law is derived for full-state feedback control of the single-phase Stefan problem, used as a model of industrial casting processes. A conceptually novel controller design approach is proposed for this problem, with the control law chosen to ensure exponential stability of the average enthalpy, and proven to guarantee asymptotic convergence of both the temperature field and the solidification front position to a desired reference. A plausible output feedback control algorithm is also given that demonstrates good behavior in simulation.

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