Robustness enhancement study of augmented positive identification controller by a sigmoid function

The dissolved oxygen concentration in the wastewater treatment process (WWTP) must remain a specific range while factory operates. augmented positive identification (PID) controller with nonlinear element (sigmoid function) is proposed to assure stability and reduce uncertainties direct reuse/recycling model. gains (PID sigmoid for uncertain processes are tuned using particle swarm optimization (PSO) technique. robust method controlling has good robustness during model mismatching, reduces time compared traditional controllers by PSO, easy apply, performance, according simulation results.