The design of FOPI and FO[pi] controllers for large time-delay system based on Smith Predictor

Smith Predictor is the main control method for large time-delay system. It theoretically solves the control problem of the large time-delay system. But it requires that the object has a precise mathematical mode, and it is also poor in disturbance rejection capability. In this paper, based on the Smith Predictor control system, Fractional Order Proportional Integral(FOPI) and Fractional Order [Proportional Integral] (FO[PI]) controllers are designed to enhance the robustness of the system. The main contents include the design of controllers and the simulation of large time-delay system. Simulation results show that according to the proposed systematic design schemes, the designed controllers can not only make the system stable, but also improve the robustness of Smith Predictor control system. Furthermore, under the same tuning rules, the designed FOPI and FO[PI] controllers can work effectively and show better controller performance than the PID controller.