Study on automatic berthing of large under-actuated vessel with multi-tug collaboration

Large under-actuated vessels often require the assistance of multiple tugboats to aid in the berthing. In this paper, a novel control strategy based on model predictive control is proposed for safely and effectively assisting large under-actuated ships to safely complete berthing operations under complex environmental disturbances. First, a ship dynamic model was developed that incorporates external environmental disturbances and mechanical constraints of tugboats to enhance model accuracy. Second, the cost function was optimized based on the characteristics of berthing by a berth coordinate system. Decompose the speed in the cost function to improve speed control during berthing. Finally, an event-triggered mechanism was integrated into the control system to address the challenge of speed convergence. This approach is particularly effective for tug-assisted large under-actuated ships operating under harsh environmental conditions. The results of berthing simulation experiments under both low-intensity and harsh environmental disturbances demonstrate that the proposed methods enable the berthing system to achieve safe positioning. This study proposes a novel approach that improves the stability and robustness of autonomous tugs in assisting large vessels during berthing operations across diverse environments.