Control Design for a Nonlinear Reactors-Separator Plant

This paper analyses the control performance of the complex nonlinear reactors-separator plant that represents a challenging control task. The controlled system consists of three units, two continuous stirred tank reactors (CSTRs) connected in the series, followed by a separator. Two control strategies were evaluated and analyzed. The first control method is based on four separate control loops utilizing conventional PI controllers. The control performance of these PI controllers serves as a reference for closed-loop system behavior. Next, the model predictive control was designed to consider the multivariable nature of the controlled system. In both cases, the reference tracking, as well as a regulatory problem, were solved. To compare the control performance of the designed methods, the settling time, maximal overshoot, and integral of the absolute value of control error were evaluated. The numerical results demonstrate that MPC significantly outperforms the conventional PID controllers.