Modeling and control of dissolved oxygen in recirculating aquaculture systems: A circadian rhythm analysis approach and GSMPC controller

Abstract

Precise control of dissolved oxygen (DO) concentration is significant for the growth and development of aquatic products. This study focused on modeling and control DO concentration in a recirculating aquaculture system (RAS). Firstly, a DO dynamic model was established based on the oxygen mass transfer equation and circadian rhythm of fish oxygen consumption rate. The fitting R² of simulation data and measured data of DO response were both above 0.96 and the significance of circadian rhythm in DO dynamic model was confirmed. Subsequently, Gain-scheduling model predictive control (GSMPC) suitable for circadian rhythm was proposed and applied to regulate the DO concentration in fish tank under various operating points, and its performance was compared with that of traditional model predictive control (MPC). In terms of set value tracking, Integral of Absolute Error of GSMPC controller dropped by 23.46% compared to MPC controller, and Integral Squared Error dropped by 11.27%, while for energy consumption, the Integral of Absolute Control dropped by 11.28%. These results demonstrated GSMPC controller not only reduced the error but also shrank the energy consumption. The findings highlighted the notable advantages of GSMPC over traditional MPC, emphasizing its effectiveness in precisely regulating DO concentration in a RAS based on circadian rhythm.