Closed-loop operation of a simulated recirculating aquaculture system with an integrated application of nonlinear model predictive control and moving horizon estimation

Abstract

High water recirculation combined with a low rate of water exchange can deteriorate water quality and affect fish welfare in recirculating aquaculture systems (RAS). A nonlinear model predictive controller (NMPC) integrated with moving horizon estimation (MHE) was implemented in this work to maintain water quality parameters (e.g., oxygen, ammonia, and nitrate concentration) in RAS. The performance of the proposed control scheme was then evaluated in the presence of process uncertainty and measurement noise with full and partial accessibility to the system’s states under several common scenarios that can arise during the operation of RAS. In all scenarios, the proposed framework showed acceptable performance in keeping the water quality parameters close to their setpoints, demonstrating the high potential of this strategy in closed-loop operation of RAS.