Modified Smith predictor scheme for periodic disturbances reduction in the continuous casting process

In the continuous casting process, various control strategies are used to reduce the mold level fluctuations which cause surface defects in the final product. This paper proposes a control structure able to improve the reduction of the bulging effect on the mold level. It is based on the Astroumlm´s modified Smith predictor scheme which presents the advantage that the setpoint response is decoupled from the disturbance rejection transfer function. H_infin control theory is utilized to develop the controller of this second loop. Both the disturbances rejection and the robust stabilization are considered in this design. Effective tuning rules are also given. Simulation results confirm that the proposed design is more effective than the one based on the PFC control law currently implemented in several real plants.