Event-triggered PID control for wastewater treatment plants

This paper is concerned with the dissolved oxygen control problem in the wastewater treatment plants (WWTPs) based on a dynamic event-triggered PID control strategy (D-EPID). The aim of the paper is to develop a simple event-triggered PID strategy for practical application. The developed strategy differs from existing PID controllers in that, it updates the control input only when certain triggering conditions are satisfied, while existing controllers update the control input at each sampling instant. The latter controller may consume extra energy even there is no need to update the control input. The triggering condition is designed based on the deviation of tracking error and an auxiliary variable. The stability analysis is conducted theoretically via designing an appropriate Lyapunov function, which cannot be provided by existing PID control methods. The controller is designed for improving the control performance of WWTPs by regulating one significant variable, i.e., oxygen concentration at some set points. Simulations based on the BSM1 platform are conducted to verify the effectiveness of the proposed control strategy. Simulation results show that for our proposed control method, the updating number of the control input can be decreased greatly while maintaining the desired tracking performance.