Tuning of PID controllers for unstable first-order plus dead time systems

Abstract

Abstract In this paper, proportional-integral-derivative (PID) controllers are tuned for unstable first-order plus dead time (UFOPDT) systems. Genetic algorithm (GA) is used to find the parameters of the PID controller for UFOPDT systems under the constraint of robustness measure. By curve fitting, the controller parameters are expressed as the functions of the UFOPDT model parameters. Two tuning formulas which consider robustness and the tradeoff between disturbance rejection and robustness of the closed-loop system are proposed. The proposed tuning formulas extend the application range of the existing methods and simulation results show that the tuned PID controllers can achieve good performance for UFOPDT systems.