Comparative Analysis of PID and Robust IMC Control in Cascaded Processes With Time-Delay

Abstract

Control of time-delay processes can be achieved by using industrial PID or implementing Internal Model based Controllers (IMC). During the last century, several methods have been proposed in the literature for tuning such controllers based on models obtained by open-loop tests. The model approximation is typically a first-order plus time-delay (FOPTD) or a delayed integration process (DIP). This paper presents a comparative analysis of popular methods used in PID, robust IMC control and Sliding Mode Control (SMC). The study includes, for each method, the analysis of the impact of model mismatch on performance, their ability to reject input and output disturbances, and their complexity. The paper provides results of numerical simulations and experiments in a cascade control loop of a pump-valve-tank system where the system is presented as two cascaded FOPTD models representing, respectively, the actuator and the tank.

Keywords

• Process control
• delay systems
• proportional-integral-derivative (PID) tuning
• internal model control
• sliding mode control
• robustness