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

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.

Introductory Chapter: PID-Based Industrial Process Control

“…However, unity feedback schemes are not suitable for plants having large time delays (LTD) and disturbances [4]. Hence, attempts have been made to design double-degree-of-freedom (DDOF) control schemes by adding additional controllers [4][5][6][7][8][9][10][11][12].…”

Introductory Chapter: Introduction to Disturbance Rejection Control

“…The classic strategy of feedback control compares the system's output continually to the intended reference signal and modifies the control action to minimize error. Feedback control aids in making up for disturbances that cannot be precisely predicted or measured in advance [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Repositioned Internal Model Control Strategy on Time-Delayed Industrial Processes With Inverse Behavior Using Equilibrium Optimizer

“…The IMC-based DCLs have attracted good research attention in recent times. Aryan and Raja [2] used the IMC-PD DCL scheme for controlling UIPs in which the controller settings were determined using the equilibrium optimizer (EO). Kumari et al [5] replaced the IMC with fractionalorder IMC (FOIMC) in their DCL structure alongside the P/PD ILS scheme for controlling the unstable continuous stirred tank reactor (CSTR).…”

“…Meanwhile, the dynamics of distillation columns, liquid storage with an attached pump, drier cans of the paper industry etc. are of integrating nature [2], [3]. Unstable and integrating processes (UIPs) are nonself-regulating in nature due to which they fail to stabilize after the introduction of any arbitrary disturbance.…”