Effect of Dead-time Approximation on Controller Performance/Robustness Designed for a First Order plus Dead-time Model

Abstract

PID controller is considered as the most generally used feedback controller design in process control industries with the longest history and most vital development. It is well-known that the performance of a PID controller is inadequate for processes with long dead-time. Smith Predictor is a kind of predictive control scheme that is effective for processes with long dead-time. PID controllers can be derived from predictive control schemes by approximating the dead-time for FOPDT process models. In this work, the predictive control scheme and dead-time approximated PID controller have been designed with various values of desirable closed loop time constants. A comparative study has been performed for closed loop performance/robustness for the actual and the dead time approximated controllers.