Wiener model-based CDM-PI controller for pH neutralisation process

Abstract

This work focuses on the design and implementation of Wiener model-based PI controller for a pH neutralisation system using coefficient diagram method (CDM). The dynamic model of a pH system is developed based on conservation balance principle by considering sodium hydroxide (NaOH, 0.1N) and hydrochloric acid (HCl, 0.1N) as reactants and it is modelled in MATLAB-Simulink platform. The pH system is approximated as first order plus time delay (FOPTD) model using step test method for computing the controller parameters. The curve fitting technique and inverse Lagrangian interpolation method are used to develop the nonlinear static element and inverse nonlinear static element of Wiener model. The performance of Wiener model-based CDM-PI controller (WMCDM-PI) is analysed and compared with conventional Wiener model-based Ziegler-Nichols (ZN) and internal model control (IMC) PI controllers at the critical operating points of pH 6 and 8. The simulation results prove the superiority of WMCDM-PI over conventional controllers.