Synthesis of robust PID controllers via stability methods for a wastewater treatment

This paper proposes a novel method to synthesize robust PID (proportional integral derivative) controller via Kharitonov´s theorem and genetic algorithm for wastewater treatment. The H∞ specifications and Kharitonov´s theorem result to solve a non-convex optimal problem subjected to several inequality constraints. The genetic algorithm is used to search the robust PID controller parameters wihout solving the steady-state Riccati equations. The novel robust PID is applicated for simplified Activated Sludge Model No.1 (ASM1) to keep the concentration of the biomass proportional to the influent flow rate with model uncertainties. Simulation shows that the algorithm is simple and effective for uncertain wastewater treatment.