Design of Fuzzy Logic-Based pH Controller for High-Pressure-Rated Modified CSTR System

In this paper, control of pH in the high-pressure-rated environmental continuous stirred tank reactor (CSTR) where deep sea conditions are mimicked is considered. Since the pressure in deep sea is higher, the pressure inside the environmental CSTR is also kept at an elevated value. Temperature inside the system is considered to be constant. Control of pH inside such a high-pressure-rated environmental CSTR system is a tedious task. First-order plus dead time (FOPDT) model is derived from the real-time system open-loop pH curve. Conventional PI controller and fuzzy logic controller are developed for the control of pH and their performance indices also compared. MATLAB Simulink block is used for controller simulation and result comparison. PI controller is tuned using minimum ISE Zhuang and Atherton method tuning protocols. Simulation result of PI controller and fuzzy logic controller are presented for comparing their efficiency; also various performance indices are calculated, and the best control action is identified. Fuzzy logic controller gives better servo and regulatory response than PI controller.