Parametric system identification and robust controller design for liquid–liquid heat exchanger system

Abstract

This study provides a step-by-step analysis of a parametric system identification procedure which provides a singleinput single-output, linear time invariant time-delay model of a liquid-liquid heat exchanger system. Different linear and blockoriented models are used to develop a control relevant identification model. The prediction error method is used to estimate the model parameters. From the simulation results, it can be found that the output error model (linear model) and Hammerstain- Wiener model (block-oriented model) provide the best model validation for a heat exchanger system at 72.23% and 81.5 % goodness-of-FIT, respectively. To achieve the control objectives of the system, the classical proportional-integral-derivative (PID) controller is used. For controller design, the linear model is considered. An industrial process is prone to encounter different uncertainties. Considering the time delay of the estimated linear model as the uncertainty, a ℋ ∞ criterion is used to find out the robust parameters of the PID controller. The developed controller satisfies the sensitivity constraints. Stability boundary locus of (K p ,K i ), (K p ,K d ) and (K d ,K i ) of the PID controller have been plotted to illustrate the robust parameters of the PID controller.