# Development of Automatic Berthing Support Program for Autonomous Ships
## 4 Discussion  
A program was developed to calculate the required thruster output to maintain the desired berthing speed under varying environmental conditions such as wind and current  
Figure 8: Experimental results (Fore). Figure 9: Experimental results (Aft). by analyzing the forces and moments acting on the hull during berthing. Full-scale tests were conducted to validate this program. During the berthing process, wind pressure, current-induced pressure, and additional pressure due to lateral berthing speed all act on the ship. At the time of docking, wind pressure at the pier's front aligned with the stern direction, resulting in minimal lateral force. Additionally, the current pressure was near zero, making the primary force the current pressure pushing the ship laterally to align parallel with the pier. As shown in Figure 10, the berthing speed of a vessel is determined by factors such as the ship's size, load condition, mooring facilities, weather conditions such as wind, and the presence of tugs. Generally, at a distance of 2-4 times the ship's beam (B) from the pier, the berthing speed is maintained around 10-15 cm/s, and at 1B, it is kept below 5 cm/s [28]. However, as shown in Table 10, the berthing speed of the test ship during the experiment, calculated based on the time taken relative to the distance from the pier, was found to be 0.25-1.13 m/s, which is 3-7.5 times higher than the standard range (0.05-0.15 m/s). This indicates that the bow thruster and stern tug were used at a higher output than typical standards, resulting in an increased berthing speed. As the automatic berthing support program is configured to calculate tug power based on the standard berthing speed (0.05-0.15 m/s) according to the distance from the pier, a considerable difference--approximately five times--was observed between the actual thruster power used on the ship and the program's calculated thruster values. In this experiment, the wind speed was not strong, and the wind direction was nearly aligned with the ship's bow-stern axis, such that the required output for the tug and thrusters remained below 1000 hp. Additionally, because the actual berthing speed exceeded the program's intended speed, it was difficult to make a direct comparison with the automatic berthing support program. Furthermore, a limitation of this study is the lack of multiple full-scale tests under various external force conditions. Technology for automatic ship berthing requires systems to detect hulls or obstacles, track ships in real time to extract dynamic information, and control the hull for automatic berthing. In 2023, [PERSON] et al. [29] proposed a real-time tracking and anchoring system based on LiDAR, which is a commonly used technology for berthing detection. This system can accurately identify dynamic and static targets and efficiently reposition ships in complex berthing scenarios. They developed a real-time vessel tracking and dynamic berthing information extraction system using 2D LiDAR, which was effectively applied to various  
Figure 10: Comparison of berthing speeds according to ship size [28]. berthing scenarios and verified through experiments on the \"Yu Kun\" training ship at Dalian Port. [PERSON] et al. [30] introduced a method to improve the monitoring of berthing and unberthing conditions by integrating GIS spatial analysis technology. [PERSON] et al. [31] proposed a method for obtaining the ship's angle using LiDAR's 3D point cloud data, which has the advantage of accurately determining the ship's angle during docking, aiding in parallel docking. Cameras provide visual information about the vessel and dock during the berthing process, helping to identify signs and obstacles in the berthing environment. [PERSON] et al. [32] designed a new artificial intelligence-based vision monitoring system for ship berthing. This system uses high-resolution images to accurately assist ships in adjusting their direction and speed, ensuring safe berthing.