Optimized trajectory tracking control of dynamic multistage metal-cooling processes with nonlinear disturbances

This paper investigates how a control structure tracks a trajectory of multistage dynamic processes optimally in the presence of exogenous linear or nonlinear unknown system disturbances. In accordance with our previous work, run out table (ROT) temperature control for hot strip cooling (a prime model of metal-cooling multistage process) serves as the basic system. We study optimal solutions in terms of disturbance attenuation of various characteristics with minimal degradation on the performance of the system. Optimal control using dynamic programming is instrumental in obtaining meaningful and tractable problem formulations and in determining the necessary and sufficient conditions, which lead to optimal and efficient solutions in relation to the presence of the disturbance. The effectiveness of this development is presented in terms of robust system performance and verified by way of simulation.