Model based Tuning of PID Controller

Abstract

In this paper PID controller with Internal Model Control tuning method (IMC-PID) is presented for robust operation. The implementation of IMC is simplified in large class of industrial applications as the process dynamics can be adequately characterized by a First Order plus Delay Time (FOPDT) model. Tuning of the controller is easily done by adjusting the filter time constant which provides improved performance and robustness of the closed loop system. The closed loop performance results of the IMC tuning have been compared with Cohen – Coon open loop and Chein, Hrones and Reswiclc (CHR)   tuning methods in terms of integral error criteria’s; Integral Absolute Error (IAE), Integral Squared Error  (ISE) and Integral Time-weighted Absolute Error (ITAE). The robustness analysis is done by incorporating uncertainty in the process model. To evaluate the performance and robustness of IMC-PID, the superheated Steam Temperature System (SHS) of 500 MW boiler is considered as case study. The results indicate that PID controller tuned with IMC provides better performance and robustness compared to other tuning techniques considered.     

Keywords:  internal model control (IMC), PID, robustness, FOPDT, tuning