피드포워드제어와 안티와인드업 기법을 결합한 열교환기 시스템의 RCGA 기반 PID 제어

Abstract

In many industrial processes and operations, such as power plants, petrochemical industries and ships, shell and tube heat exchangers are widely used and probably applicable for a wide range of operating temperatures. The main purpose of a heat exchanger is to transfer heat between two or more medium with temperature differences. Heat exchangers are highly nonlinear, time-varying and time lag behavior during operation. The temperature control of such processes has been challenging to control engineers and a variety of forms of PID controllers have been proposed to guarantee better performance.

Over decades PID controller has proven to be a very useful instrument in industrial fields. The generality of PID controllers allows easier design and tuning compared to other complicated controllers in addition to excellent control performance, and enables field engineers to operate them relatively easily.

In this thesis, a scheme of controlling outlet temperature of a shell and tube heat exchanger system with non-linearity, time varying and dead time that combines the PID controller with filtering the derivative eliminating a measurement noise, a feedforward control improving a disturbance rejection and an anti-windup strategy preventing the integral terms from accumulated a significant error above or below pre-determined bounds is presented. A real-coded genetic algorithms(RCGAs) is used to tune the parameters of the PID controller with anti-windup technique and the feedforward controller by minimizing the integral of time-weighted absolute error(ITAE). Simulation works are performed to study the performance of the proposed method when applied to the process.