Trans RINA, Vol 161, Part A4, Intl J Maritime Eng, Oct-Dec 2019
collision avoidance route in relative motion and true motion, respectively since the beginning of the simulation. As seen in the figures, the OS can pass safely regarding the requirements of the sea navigation rules. As a result, in this scenario, the developed method has revealed that the OS should alter her course to 095.1o and proceed on this course until the course alteration, which is -018.37o, to return original route. The length of the optimal trajectory is measured 22.36 Nm and the extra distance navigated by the OS is 0.36 Nm. The execution time to reach the solution is the same as the above cases.
Figure 12. Dynamic simulation of collision avoidance route in relative motion for case 3
Figure 11. Real encounter situation. Source:
www.marinetraffic.com
4.4
IMPLEMENTATION FOR COMPARISON AND DISCUSSION
The proposed method has been compared to other methods and systems. In order to demonstrate the advantage of the approach, Case 4 and Case 5 have been implemented. For this purpose, the results received from heuristic-based method, the Genetic Algorithm (GA) (introduced by Tsou et al., 2010), has been used to make a comparison. The initial navigational data of ships for these cases are listed in Table 2. Comparison results of the cases are shown in Table 4 in detail.
Figure 13. Dynamic simulation of collision avoidance route in true motion for Case 3
Table 4. Comparison results. Method
Length of Trajectory [Nm]
4WBDA 20.02 GA
5WBDA 4.53 GA
21.18 5.55
Extra
Navigating Distance [Nm]
0.57 1.73 0.71 1.73
Optimum Anti-
Collision Course [o]
Course
Alteration to Return Original Route [o]
005.12 -051.44 046.00 -093.00 043.20 -071.11 046.00 -093.00
4.4 (a) Case 4: Crossing Situation
A comparison of the OS trajectories determined by the WBDA and the GA-based algorithm is shown in Figure 14. Numerical results are compared in Table 4. The solution generated by the WBDA considerably outperforms GA-based algorithm. The difference with regard to the length of the trajectory is 1.16 Nm. On the other hand, with respect to execution time, the
Computational Time [s]
≈ 0.02 14-26 ≈ 0.02 14-26
©2019: The Royal Institution of Naval Architects
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