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This paper presents the development of a control oriented boiler model carried out on the basis of fundamental physical laws, previous efforts in boiler modeling, known physical constants, plant data, and heuristic adjustments. The resulting fairly accurate model is nonlinear, fourth order, and includes inverse response (shrink and swell effects), time delays, measurement noise models, and a load disturbance component. The model obtained can be directly used for the synthesis of model-based control algorithms as well as setting up a real-time simulator for testing of new boiler control systems and operator training.

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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.

This paper develops the theory of vibrational control Of "lhJear time Systems with arbitrarily large but bounded delay. theory for fast Oscillating, differential delay equations is presented and then applied to vibrational control. conditions B1p given which ensure the e*ne ot parametric vibrations that stabilize nonlinear time lag systems. Transient behavior is also discussed. Illustrative examples are given which Show 1) the f-bfiv Ofthe theory to hP0-t aPPfiatiOm and 2, the differences in the presented and the eKisw known theory for vibrational control of ordinary differential equations. the vibrations depended only on time (and not on the value of the state), there no longer was a need to take measurements of concentration, thus reducing the cost of the reaction even more. For similar reasons, the vibrational control described by [61 has many benefits. A number of practical, important systems, however, are best described by including time delays in their states. In particular, if the exothermic reaction vibrationally controlled in [5] includes a recycle stream, as in [7], the model must

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