Study of an Automatic Control and Management System for Air Intake and Exhaust in Submersible Net Cages

To mitigate the challenges of excessive tilting angles and the risk of overturning during the submersion and ascent of the net cage, this study developed an automatic control and management system for submersible net cages. The system employs proportional–integral–derivative (PID) control technology, optimizing PID parameters through tilt signals and control algorithms to adjust actuators, thereby enabling automatic regulation of the net cage tilt angle. The accompanying management system integrates several functionalities, including submersion and elevation control, suspension control, water level monitoring, pressure data monitoring, current velocity measurement, water quality monitoring, GPS positioning, and underwater camera surveillance. Through a series of experiments, the most suitable buoyancy-to-gravity ratio for the net cage was determined to be 1.2. Experimental results identified optimal PID parameters for submersion (P = 100, I = 1000, D = 0) and ascent (P = 50, I = 800, D = 0), and suspension control was achieved using a compressed air pressure of 0.40 kPa. By integrating modular control systems and data modules into a unified framework, this study addresses key limitations in the automatic systems for deep-sea submersible net cages, achieving a tilting angle of less than 15° during submersion and less than 5° during ascent. The proposed automatic control system represents a critical technological advancement for the industrialization of deep-sea aquaculture and provides essential data and theoretical foundations for the future development and application of deep-sea submersible net cages.