Enhanced control of double integrating plus time delay systems using a two-degree-of-freedom Smith predictor

This article presents a novel control approach using a two-degree-of-freedom (2-DOF) Smith predictor structure for double integrating plus time delay plants. The PD and PID controllers, integral components of the Smith predictor scheme, serve distinct roles in the control process. The PD controller is responsible for set-point tracking, while both PD and PID controllers contribute to the rejection of load disturbances. Each controller is designed using the pole placement technique, with an appropriate tuning parameter established to balance performance and robustness effectively. A low-pass filter is incorporated to improve the response of the set-point signal by attenuating high-frequency noise. The proposed method's effectiveness is compared with Skogestad internal model control, a well-known PID tuning method, to benchmark performance improvements and demonstrate the advantages of the 2-DOF Smith predictor approach. Simulation and comparison analysis demonstrates that the proposed controller setting is suitable for industrial applications due to its quick set-point tracking, effective load disturbance rejection, and smooth control signal. The study highlights the practical benefits of the 2-DOF Smith predictor in enhancing industrial control system performance and suggests directions for future research, including experimental validation and robustness analysis under varying system parameters.