Fuzzy control system for three-dimensional towing trajectory of trawl gear

In trawling, the trawl gear is connected to a trawler through a warp and towed by the trawler propulsion. The depth of the trawl gear, determined by the warp length, and the trawler direction are the most essential factors for successful trawling. In fact, the position and swimming depth of target fish school should be accurately determined to enable the trawl gear to reach the depth of the fish school by controlling the trawler velocity and direction. Automating this process requires three-dimensional simultaneous control of the trawler direction and trawl gear depth. In this study, we applied fuzzy logic rules generated from language instructions used by skilled captains, master fishermen, and officers to control the trawl gear depth and trawler direction. We verified the accurate enclosing of a target fish school at the center of the trawl gear through simulations. When applying the proposed three-dimensional position control of the trawl gear, its depth was adjusted with an error up to 7%. Thus, the depth of a trawl gear can be automatically controlled by adjusting the trawler direction and warp length during trawling.