Auto-Tuning Method for Alternating Aeration Control in Activated Sludge Processes

The paper presents an auto-tuning method for PID controllers based on a relay feedback experiment with application to a Wastewater Treatment Plants process. By performing a single test based on an asymmetric relay feedback experiment two points on the Nyquist plot are identified and a second order linear model of the process is obtained. This model is further used to tune the PID controller parameters. The asymmetric relay feedback system analysis and the tuning rules development are accompanied by an illustrative example related to the aeration control in activated sludge wastewater treatment processes. The auto tuning procedure and the PID controller performances are illustrated by simulation results. Both the setpoint tracking and the regulatory capability have been analyzed.