# Research on Collision Warning Method for Ship-Bridge Based on Safety Potential Field
## 5 Simulation Experiments
### Bridge Area Safety Potential Field Experiment  
According to the experimental setup, based on the superimposed field model, the instantaneous navigation risk generated by each type of element within the bridge area can be calculated and the distribution of the navigational risk in the channel can be represented by a potential field. The study area is gridded and the lateral navigation risk is compared by means of a cross-section perpendicular to the navigation direction in order to determine the location of the risk magnitude in the following cross section. Next, the safety potential fields at the grid points of each longitudinal section of the navigation channel are compared  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline \(k_{i}\) & 2.5 \\ \(\tau\) & 0.18 \\ \(\beta\) & 2.2 \\ \(u_{i}\) & 20 \\ \(H_{r}\) & 0.1 \\ \hline \hline \end{tabular}
\end{table}
Table 3: The parameters for the safety potential field model used in the case study.  
Figure 13: Simulated waterway environment diagram.  
to obtain the distribution of the potential field size of the overall safety field to determine the magnitude of the risk.  
Some AIS ship data of Baijusi bridge area on 2 May 2024 are selected, and the relationship between ships and bridge area is shown in Figure (a)a. Where TS1, TS2, TS3, TS4 and TS5 represent the ships navigating in the waters of the bridge area, and the ship parameters are shown in Table 4. Where the black solid line represents the channel boundary, the dotted line represents the upstream and downstream channel demarcation line, the circle and triangular markers represent the navigation markers, the green rectangle represents the bridge abutment, and the purple arrow represents the direction of traffic flow. According to Chapter 2, the corresponding safety potential field of the bridge area elements established is shown in Figure (b)b.  
As shown in Figure (a)a, TS1 and TS2 are travelling in the channel with the same dimensions, but the risk of TS2 is significantly greater than that of TS1 (as shown in Figure (b)b) because TS2 is closer to the edge of the channel, in line with the nautical practice. The distances from the same side of the channel to the navigational markers are the same for both TS1 and TS3, but the risk for TS2 is significantly greater than that for TS3 in Figure (b)b because of the larger dimensions of TS2. TS3 and TS4 are the same size in Figure (a)a; however, in Figure (b)b, TS4 is closer to the bridge abutment, so the risk value for TS4 is significantly greater than that for TS3. In Figure (a)a, TS1 and TS5 are the same size and both are upstream sailing vessels; however, in Figure (b)b, the risk for TS5 is  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ship Number** & **1** & **2** & **3** & **4** & **5** \\ \hline Length of ship & 110 & 110 & 85 & 85 & 110 \\ \hline Width of ship & 16 & 16 & 11 & 11 & 16 \\ \hline Speed & 8 & 8 & 8 & 8 & 12 \\ \hline Course & 330 & 150 & 130 & 320 & 320 \\ \hline Distance to \(\mathrm{pi}/\mathrm{m}\) & 1100 & 950 & 450 & 150 & 1000 \\ \hline Distance to \(\mathrm{ipsilateral}\) & \multirow{2}{*}{115} & \multirow{2}{*}{35} & \multirow{2}{*}{35} & \multirow{2}{*}{35} & \multirow{2}{*}{115} \\ navigational markers/m & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Instantaneous channel vessel information.  
Figure 14: Distribution of instantaneous navigational hazards in the bridge area for static scenarios.  
significantly greater than that for TS1 because the speed of TS5 is significantly faster than that of TS1. The faster the speed, the higher the field strength value.  
In summary, different types of ships, or the same type of ship, produce different transient navigation risks due to their different distances from beacons, bridge abutments and piers, or different speeds.