Overcoming Dead Time in Thermal Processes: A Comparative Evaluation of PID-SP and PID-IMC Control Strategies

Abstract

Dead time is a critical factor that often causes instability in process systems, so appropriate control strategies are needed to address it. This study focuses on the outlet temperature control of a stirred-tank heater that exhibits dead time. A 10 L laboratory-scale tank equipped with an electric heater was constructed, and the long outlet pipeline introduces a measurable delay in the temperature response. The outlet temperature is maintained by adjusting the electrical heating input, while PID parameters are tuned using the Process Reaction Curve (PRC) method. Two control strategies are examined: PID with Smith Predictor (PID-SP) and PID with Internal Model Control (PID-IMC). System models were implemented and tested using XCOS/Scilab. Closed-loop simulation results indicate that PID-IMC performs better than PID-SP, as indicated by a lower integral absolute error (IAE). These results provide evidence of the practical advantages of PID-IMC in compensating for dead time in thermal process systems and offer useful guidance for improving process control design in industrial applications.