Fault estimation and self-healing control for actuator fault in dissolved oxygen control of wastewater treatment

Abstract

Wastewater treatment processes (WWTPs) are inherently complex, characterized by various dynamic operations such as aerobic digestion, which critically depends on maintaining optimal dissolved oxygen (DO) levels. Actuator faults in WWTPs, particularly those affecting oxygen transfer systems, can disrupt this balance, leading to inefficiencies and safety hazards. This paper addresses the issue of fault estimation and self-healing control, specifically in the presence of additive actuator faults affecting the DO regulation. First, a low-order state-space model is introduced as a mechanistic alternative to the Benchmark Simulation Model No. 1 (BSM1) to model the dynamics of WWTPs. Second, the additive actuator fault is incorporated into the system state, and an adaptive proportional-integral observer (APIO) is designed to estimate these faults. Third, a self-healing controller based on sliding-mode control (SMC) is developed to restore the system’s performance and ensure stable DO levels. Finally, the performance of the proposed strategy is evaluated through simulations, which demonstrate its ability to accurately estimate faults and effectively restore system stability in the presence of actuator failures.