PLC-based PID controller for real-time pH neutralization process using Palm Oil Mill Effluent

Abstract

The pH neutralization process is a highly non-linear process and time delay system that is difficult to control and to accurately model mathematically. Therefore, the empirical method, which needs reliable experimental data to represent the process dynamics, is often used. In this paper, the performance of the PLC-based PID controller was studied using a different adjustment of the acid dosing pump stroke rate in the pH neutralization process. The pH neutralization process is a single-input, single-output system where the manipulated variable is the alkali dosing pump stroke rate, the controlled variable is pH, and the acid dosing pump stroke rate is set as a constant. The acid dosing pump stroke rate was adjusted to 10%, 15% and 25%. The results showed that the best performance of the PID controller was based on setpoint tracking when the setting of the acid dosing pump stroke rate was set at 10%, which could be used as experimental data in the empirical method. In addition, the real-time control system was integrated between PLC and MATLAB using National Instruments OPC server to access the experimental data in real-time, conduct simulation, and to develop the advanced control in the future.

ABSTRAK: Peneutralan pH adalah proses tidak linear yang sukar dikawal dan sukar mendapat model matematik yang tepat. Oleh itu, kaedah empirikal memerlukan data eksperimen masa nyata bagi mewakili proses dinamik untuk mengatasi masalah ini. Kajian ini adalah berkaitan kajian prestasi pengawal PLC-berdasarkan PID menggunakan pelbagai perubahan kadar strok pam dos asid dalam proses peneutralan pH. Proses peneutralan pH ini adalah sistem satu input/output, di mana pemboleh ubah yang dimanipulasi adalah kadar peratusan strok pam dos alkali menggunakan pam peristaltik, pemboleh ubah kawalan ialah pH dan pemboleh ubah malar ialah peratusan dos asid.Kadar strok pam dos asid dilaraskan pada 10%, 15% dan 25%. Dapatan kajian menunjukkan prestasi terbaik kawalan PID adalah berdasarkan pengesan titik-set apabila kadar strok pam dos asid dilaraskan pada 10%, di mana ianya berkesan apabila digunakan sebagai data eksperimen dalam kaedah empirikal. Tambahan, kajian ini telah berjaya membentuk sistem kawalan masa nyata bagi proses penutralan pH menggunakan PLC dan MATLAB melalui pelayan National Instruments OPC bagi membolehkan pertukaran data eksperimen secara masa nyata yang cekap, menjalankan simulasi dan pembangunan kawalan termaju pada masa hadapan.