A novel equilibrium optimized double-loop control scheme for unstable and integrating chemical processes involving dead time

Abstract

Abstract Integrating and unstable chemical processes showcase instability in open-loop configuration due to the existence of poles at the origin and right-half of the s-plane. They present challenging control requirements due to their non-self-regulating nature. The presence of dead time demands more sophisticated control requirements for the above-mentioned processes. So double-loop control strategies are preferred over PID controllers in single-loop configuration. In this work, a novel IMC-PD double-loop control strategy is proposed for unstable and integrating plants with dead time. The inner-loop consists of PD controller whose initial settings are derived using Routh–Hurwitz stability conditions. The outer-loop consists of an IMC controller whose parameter along with that of the PD controller is optimized using the metaheuristic algorithm called equilibrium optimizer algorithm (EOA). EOA utilizes the range of controller settings from RH criteria for stable operation and provides the optimal settings by minimizing the integral square error (ISE). Merits of the suggested strategy is illustrated with the help of benchmark plant models of unstable/integrating chemical processes and that of a bioreactor. By computing quantitative performance measures, the dynamic responses resulting from the proposed control scheme is found to be more effective than the reported works.