Time delay compensation for the secondary processes in a multivariable carbon isotope separation unit

Abstract

Time delays occur frequently in process control systems and uncertainties regarding modeling of such phenomena limit the degree of freedom of the designed controllers. The problem is even more acute when dealing with multivariable systems. To overcome the difficulties in the controller design, Smith predictor control schemes are frequently used. The paper proposes a simple, yet efficient, novel control strategy for solving the delay time compensation problem for the secondary processes in a pilot plant cryogenic carbon isotope separation column. The authors show that compared to an exiting control strategy, the proposed method can be generally applied to any type of system. To illustrate the robustness of the proposed closed loop control scheme a more advanced control strategy is designed consisting in an EPSAC model based predictive controller. Comparative simulations, considering ±50% uncertainty in the multivariable time delays, show that the novel control strategy proposed in this paper offers good results both in terms of reference tracking and robustness, similar to those of the predictive controller. Additionally, the proposed control strategy has a wide area of applicability, to a general class of chemical units.