Comparative Analysis of PI / PID Controller for a Thermal Process Using PLC

Abstract

This paper presents the comparative analysis of a versatile PID controller and PI controller to control a thermal process using the PLC ladder functions and hardware interface in a closed loop system. The Cohen-Coon’s PRC method is used for setting the PID and PI control Parameters. The proposed control algorithm is experimentally implemented on the heater-furnaceblower method also the results are presented. The ladder functions of GE Fanuc Versamax PLC is used to develop the control algorithms namely, position-form and velocity-form algorithm. The performance of the complete algorithm for the PID and PI using PLC on the heater-furnace-blower system are tested at different sampling instants and the experimental results are compared with the response of the same system with the position-form algorithm developed using the same PLC and the developed PID and PI function block in the PLC. It is observed that the velocity-form PID and PI control algorithm is capable to follow the factor variation rapidly and perform better in load disturbances. This approach helped in maximize consumption of the PLC ladder function and provides more flexibility by those PLCs, which do not maintain prepared PID loops.