# Automated Docking System for LNG Loading Arm Based on Machine Vision and Multi-Sensor Fusion
## 4 Performance Verification of Automatic Docking System for LNG Loading Boom  
This section verifies the performance of the self-developed automatic LNG loading-arm docking system. The experimental scenario is shown in Figure 17. The test bench is set  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{ \begin{tabular}{c} **Experimental Environment** \\ \end{tabular}  } & \multicolumn{2}{c}{**X-Axis**} & \multicolumn{2}{c}{**Y-Axis**} & \multicolumn{2}{c}{**Z-Axis**} \\  & **Measured** & **Relative** & **Error** & **Measured** & **Relative** & **Error** & **Measured** & **Relative** & **Measured** & **Relative** \\  & **cm** & **cm** & **\%** & **cm** & **cm** & **\%** & **cm** & **cm** & **\%** & **cm** & **\%** \\ \hline
1 & \(-\)15.0 & \(-\)15.20 & 1.33\% & \(-\)5.00 & \(-\)5.03 & 0.60\% & 20.00 & 20.19 & 0.95 \\
2 & \(-\)13.00 & \(-\)13.16 & 1.23 & \(-\)4.00 & \(-\)4.02 & 0.50 &up at the dock, which can simulate the operation of the loading arm in the actual operating environment. In order to closely resemble the real ship-to-shore docking scenario, the experiment takes into account as many external factors of the dock environment as possible, such as the effect of wind on the operation of the loading arm. Specifically, experiments were performed during overcast and rainy weather to assess the system's performance under varying environmental conditions. The experimental results demonstrated that the system operated stably under these conditions. However, due to the limitations of the experimental conditions, the dynamic effect of waves cannot be completely simulated. Although the experiment cannot fully replicate the effect of waves on the hull, the wind's influence on the unloading arm was observed. The wind-induced disturbances led to oscillations in the horizontal direction of the unloading arm, causing relative displacement between the arm's end and the flange. This effect is similar to the disturbances caused by waves, as both introduce lateral movement that can disrupt the precise alignment necessary for docking. By conducting the experiment in a dock environment, the reliability and adaptability of the system in actual application can still be effectively evaluated, and the results provide useful insights into its performance under challenging conditions. The experiment includes two stages: coarse docking and fine docking. The relevant information is displayed in real time through the software interface, as shown in Figure 18. Figure 18 shows the interface for the coarse docking stage at the top, which displays the target position coordinates of the loading arm, real-time path planning, and pose information fed back by the angle sensor; the interface for the fine docking stage is shown at the bottom, which displays the 3D coordinates of the flange, real-time distance, and position correction data. These two interfaces can comprehensively display the operating status and real-time feedback information of the system during different docking stages, providing intuitive support for the analysis of experimental results. During the experiment, the loading arm first moved from its initial position to near the target flange to complete the coarse docking phase. This phase mainly examines the system's path planning capabilities and rapid response performance, and relies on information from the angle sensor to determine whether it has entered the predetermined range. Since precise positioning is not required during the coarse d  
Figure 17: LNG loading-arm dock-to-port test scenario. robust to environmental factors such as wind interference. The experiment showed that the loading arm can operate stably and successfully complete the initial approach. After entering the fine docking stage, the system mainly relies on the monocular camera and ultrasonic sensor for precise positioning and attitude adjustment.