Abstract
According to International Regulations for Preventing Collision at Sea, collision avoidance started from assessing the collision risk. In particular, the radar was mentioned as suitable equipment for observation and analysis of the collision risk. Thus, many researches have been conducted by utilizing the radar. Fuzzy Inference System based on Type-1 Fuzzy Logic (T1FIS) using Distance to Closest Point of Approach ( D C P A ) and Time to Closest Point of Approach ( T C P A ) computed via the radar has been largely used for assessing the collision risk. However, the T1FIS had significant limitations on the membership function not including linguistic and numerical uncertainties. In order to solve the issue, we developed the Fuzzy Inference System based on Interval Type-2 Fuzzy Logic (IT2FIS) as follows: (i) the T1FIS was selected among proposed methods based on the type-1 fuzzy logic; (ii) we extended the T1FIS into the IT2FIS by gradually increasing the Footprint of Uncertainty (FOU) size taking into consideration symmetry, and (iii) numerical simulations were conducted for performance validation. As a result, the IT2FIS using the FOU size “±5%” (i.e., interval 10% between upper membership function and lower membership function) not only computed the appropriate and linear collision risk index smoothly until near-collision situation but also help to overcome uncertainties that exist in real navigation environments.
Highlights
The possibility of maritime collision accidents has been increasing due to the emergence of large ships, high speed, and the growth of maritime transportation and international trade
Sci. 2020, 10, x in Table 3, and Figure 13 shows the occurred area of near-collision, which the ship safety domains proposed by Fujii and Tanaka were overlapped
We developed the IT2FIS as an extension of the T1FIS-NC, and focused the Footprint of Uncertainty (FOU) size taking account of symmetry
Summary
The possibility of maritime collision accidents has been increasing due to the emergence of large ships, high speed, and the growth of maritime transportation and international trade. The scale of maritime accidents becomes larger and it causes serious marine pollution, huge economic losses, and loss of life at sea. According to statistic investigation presented by Korean Maritime Safety. Tribunal (KMST) [1] over the past five years, collision accidents among entire accidents at sea have reported approximately 13.5%. More than approximately 90% out of collision accidents was due to human errors. Most of these human errors were a “lack of recognition of collision risk”. According to “Rule 7: Risk of Collision” in the International Regulations for Preventing Collision at the Sea (COLREGs) [2], the collision risk must be assessed by all available means appropriate to the prevailing circumstance using predictive technology.
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