Trans RINA, Vol 161, Part A4, Intl J Maritime Eng, Oct-Dec 2019
Figure 8. Dynamic simulation of collision avoidance route in true motion for case 1
As shown in the figures, the OS can pass safely regarding the requirements of the sea navigation rules (COLREGs). As a result, in this scenario, the developed method has revealed that the OS should alter her course to 028.96o and proceed on this course until the course alteration, which is -042.68o, to return the original route. The length of the optimal trajectory is measured 15.77 Nm and the extra distance navigated by the OS is 0.77 Nm. The execution time to reach the solution is only 0.02 s.
4.2 CASE 2: OVERTAKING SITUATION
In Case 2, the OS is approaching to TS from its stern and the current motion of the ships cause collision, so the OS as an overtaking ship should take action to eliminate the risk. The initial course of the OS is 000o, the course of the TS is 340o, the speeds of the OS and the TS are set at 17 knots and 9 knots respectively, the relative bearing of the TS is 020o, the distance between the ships is 6 Nm, the return distance to original route of the OS is 23 Nm and ship domain radius is set at 2 Nm.
Figure 9 and Figure 10 show the time passed (T1, T2, T3, T4) of dynamic simulation of 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 COLREGs. As a result, in this scenario, the developed method has revealed that the OS should alter her course to 012.34o and proceed on this course until the course alteration, which is -022.83o, to return the original route.
The length of the optimal trajectory is measured 23.34 Nm and the extra distance navigated by the OS is 0.34 Nm. The execution time to reach the solution is only 0.02 s.
Figure 9. Dynamic simulation of collision avoidance route in relative motion for case 2
Figure 10. Dynamic simulation of collision avoidance route in true motion for case 2
4.3 CASE 3: HEAD-ON SITUATION
In Case 3, to illustrate a real encounter situation, the navigational data of ships are obtained from
www.marinetraffic.com which keeps a real time data of ships provided from AIS. The situation which is shown in Figure 11 takes place close to the Gulf of Antalya. In this case, the ships are approaching each other head-to- head and the current motion of the ships leads to collision, so the collision avoidance action should be taken to eliminate the risk. The initial course of the OS is 088o, the course of the TS is 263o, the speeds of the OS and the TS are set at 14 knots and 12 knots respectively, the relative bearing of the TS is 357o, the distance between the ships is 25.4 Nm, the return distance to original route of the OS is 22 Nm and ship domain radius is set at 2 Nm. Figure 12 and Figure 13 show the time passed (T1, T2, T3, T4) of dynamic simulation of
A-352 ©2019: The Royal Institution of Naval Architects
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