Comparison of non-linear, linearized 2nd order and reduced to FOPDT models of CSTR using different tuning methods

Abstract

Process modelling and design of controller based on the process model is an important step in the process control. In the present study three different mathematical models i.e. non-linear process model, linearized 2nd order model and first order with dead time (FOPDT) model of a CSTR with the concentration of output of product as controlled parameter were developed. Proportional Integral (PI) controllers were designed based on 2nd order and FOPDT models of a CSTR using SIMC (Skogestad internal model control), Hagglund and Astrom, and a computational method with 5% overshoot. In all the three tuning methods, the nonlinear model provided better results in terms of various time parameters (Tr, Ty, Ts) and in error analysis (IAE, ITAE and ISE).