Fuzzy Anti-Reset Windup for PID Controllers

Abstract In this paper anti windup schemes for PID controllers are proposed that consider not only actuator constraints but also process state constraints. The schemes are fuzzy generalizations and combinations of the traditional conditional integration anti-windup schemes. The proposed schemes are easy to implement and tune, since they are given explicitly which only one or two tuning parameters. It will be seen that the schemes decrease the rate of change of the integrator state in the controller when the actuator or process is saturated. Under an assumption of an upper bound on this rate, stability analysis is performed for an integrator process by means of Lyapunov theory. Simulations on a process with actuator constrains as well as state constraints are performed. It is seen that the new scheme outperforms the traditional anti-windup schemes considered.