Path Following Control of Large Ship Towing Based on Hierarchical Anti-Disturbance Control Strategy

Objectives Safely towing large ships to target sea areas is crucial for maritime navigation safety. In order to enhance the disturbance rejection performance of underactuated autonomous tugboats during the towing process of large ships, a hierarchical disturbance rejection control strategy based on Active Disturbance Rejection Sliding Mode Control is proposed. Methods Firstly, a coupled motion mathematical model of the towing system under disturbances is established based on the ship MMG model. Subsequently, a towed line-of-sight guidance method applicable to towed navigation is proposed, converting the path tracking problem into a speed and heading control problem. A hierarchical anti-disturbance control strategy (HAD-CS) is designed. For the control layer of the towed vessel, a top-level disturbance rejection control based on a combination of active disturbance rejection control and sliding mode control is structured to ensure the towing system achieves the control objective of path tracking. Real-time allocation is made to the lower-level tow winch control task. In the tow winch control layer, a bottom-level anti-disturbance control based on active disturbance rejection sliding mode control is designed, with the output of the top-level disturbance rejection control serving as its own control input. Hierarchical control and hierarchical anti-disturbance are achieved based on considerations of the constraints of the tow cable and thrusters. a towing line-of-sight guidance method suitable for towing navigation is proposed, which transforms the path tracking problem into a speed and heading control problem. A hierarchical anti-disturbance control strategy (HAD-CS) is designed based on the manipulation model of the towing system. In the disturbance rejection layer of the towed vessel, a top-level virtual controller combining self-disturbance rejection control and sliding mode control is designed. The output information of the virtual controller is used as the input to the lower-level tug controller. For the tug's disturbance rejection layer, a sliding mode controller based on an extended state observer is designed, taking into account the constraints of the towline and propeller. Finally, the anti-disturbance performance of the towing system under complex disturbances is compared and evaluated in a simulation environment. Results By utilizing a hierarchical active disturbance rejection sliding mode control strategy for towing control, the path tracking performance of the towed large vessel is enhanced by 16.9%. The heading and speed keeping performances are improved by 34.6% and 67.5% respectively. Additionally, the heading and speed keeping performances of the tugboat are increased by 51.9% and 52.2% respectively Conclusions The proposed control strategy can effectively resist external