• Journal of the Society of Naval Architects of Korea
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• v.56 no.1
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• pp.58-65
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• 2019

The stability, reliability and efficiency of a smart ship are important issues as the interest in an autonomous ship has recently been high. An automatic collision avoidance system is an essential function of an autonomous ship. This system detects the possibility of collision and automatically takes avoidance actions in consideration of economy and safety. In order to construct an automatic collision avoidance system using reinforcement learning, in this work, the sequential decision problem of ship collision is mathematically formulated through a Markov Decision Process (MDP). A reinforcement learning environment is constructed based on the ship maneuvering equations, and then the three key components (state, action, and reward) of MDP are defined. The state uses parameters of the relationship between own-ship and target-ship, the action is the vertical distance away from the target course, and the reward is defined as a function considering safety and economics. In order to solve the sequential decision problem, the Deep Deterministic Policy Gradient (DDPG) algorithm which can express continuous action space and search an optimal action policy is utilized. The collision avoidance system is then tested assuming the $90^{\circ}$intersection encounter situation and yields a satisfactory result.

• Journal of Korea Ship Safrty Technology Authority
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• s.38
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• pp.69-77
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• 2015

If we don't know the intention of altering course of a target ship when being in a head-on or a crossing situation, we may be confused about our decision making to change our course for collision avoidance and be in a danger of collision. In order to solve these problems, we need to develop an automatic detection system on altering course of a target ship for efficient collision avoidance. In this paper, we proposed an early detection system on altering course of a target ship using the steering wheel signal. This system will contribute to the reduction of collision accidents and also be used to the VTS system and the analysis of marine accidents.

• Journal of Korea Ship Safrty Technology Authority
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• s.36
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• pp.71-78
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• 2014

If we don't know the intention of altering course of a target ship when being in a head-on or a crossing situation, we may be confused about our decision making to change our course for collision avoidance and be in a danger of collision. In order to solve these problems, we need to develop an automatic detection system on altering course of a target ship for efficient collision avoidance. In this paper, we proposed an early detection system on altering course of a target ship using the steering wheel signal. This system will contribute to the reduction of collision accidents and also be used to the VTS system and the analysis of marine accidents.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.79-80
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• 2007

An expert system of collision avoidance developed by CLIPS and Visual C++ is continuously introduced in this paper. Further, a simulation function of collision avoidance is added to the expert system, the function can simulate the avoidance actions of own ship and a specific target of a period of future time. This function can help navigators to estimate collision risk and make proper collision avoidance actions in dangerous situations for navigational safety of ships. Furthermore, navigational rules can also be evaluated during the process of simulation.

• Journal of Navigation and Port Research
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• v.31 no.4
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• pp.309-315
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• 2007

We've investigated the characteristics on mariner's behavior in the collision situation through a full-mission ship handling simulator and considered that it's necessary to model the standard avoiding behavior of mariners in order to apply the obtained results more widely and effectively. Thus we described the contents of standard avoiding behavior taken by mariners in the collision situation and established the concept of the standard model based on human factors for collision avoidance in a previous study. As a following study, this paper is to propose the method of modeling on mariners' standard behavior for collision avoidance by analyzing the contents of mariner's information processing and the related factors using regression analysis. As a result, we confirmed the influence of relating factors to avoiding behavior in mariner's deciding decisions and proposed the modeling method of mariners' standard behavior for collision avoidance with a example of recognition model.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.113-118
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• 2017

Various studies on the method of ship collision risk assessment for alarm have been reported constantly, and the result of the studies is applied to navigation devices. However, it is known that navigators ignore or turn off frequent alarms from the devices of predicting collision risk, because they may avoid collisions in the most of situations. In oder to make the prediction of ship collision risk more useful, it is necessary to consider the customary actions of ship collision avoidance. This paper proposes a system of analyzing collision avoidance measures of ships according to the types of encounter and managing the avoidance history of each ship. The core module of the system is designed as a neuro-fuzzy based inference system, and the test of the module validates the proposed system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.181-190
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• 2007

This paper presents a collision avoidance system for intelligent ship. Unlike collision avoidance system of other unmanned vehicles, the collision avoidance system for intelligent ship aims at not only deriving a reasonable and safe path to the goal but also keeping COLRECs(International Regulations for Preventing Collisions at Sea). The heuristic search based on the BK-products is adopted to achieve the general purpose of collision avoidance system; deriving a reasonable and safe path. The rule of action to avoid collision is adopted for the other necessary and sufficient condition; keeping the COLREGs. The verification of proposed collision avoidance system is performed with scenarios that represent encounter situations classified in the COLREGs, then it is compared with $A^{\ast}$ search method in view of optimality and safety. The analysis of simulation result revels that the proposed collision avoidance system is practical and effective candidate for real-time collision avoidance system of intelligent ship.

• Journal of the Korean Institute of Navigation
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• v.15 no.2
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• pp.13-38
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• 1991

This paper intends to develop a Prototype Expert Collision Avoidance System by introducing expert system techniques into the decision block of anti-collision loop. The problem domain of this study is characterized and specified by combining the concepts of anti-collision loop and knowledge -based system for collision avoidance. Domain in knowledge which may originates from the appropriate sources such as the International Regulations for Preventing Collision at Sea 1972, Marine Traffic Laws, and many texts on the subject of anticollision navigation and good seamanship is acquired and formalized into the knowledge-base system using production rule. Finally, a Prototype Expert Collision Avoidance System is built by using the CLIPS, developed by AIS NASA written in and fully integrated with the C language, and some test-and-run results of the system are demonstrated and examined. The author considers the proposed system which is named PECAS to be meaningful as a test bed for a further refined Expert Collision Avoidance System on board the Automated Ship.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.6
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• pp.406-415
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• 2023

In this study, we focused on developing and verifying ship collision avoidance algorithms using Unity simulator and ROS(Robot Operating System). ROS is used to establish an environment where communication between different operating systems is possible, and a dynamic model of a ship is constructed within Unity simulator. The Lidar data collected in Unity environment is passed to the system based on python through ROS. In the system based on python, control command values were created through the logic of the collision avoidance algorithm using data, and the values were transferred back to Unity to control the movement of the virtual ship. Through the developed simulation system, the reliability of the collision avoidance algorithm of ships with two different forms in an environment similar to the actual physical world was confirmed. As a result, it was confirmed on the simulator that it could be avoided without collision even in an environment with various types of obstacles, and that the avoidance characteristics according to the dynamics of the ship could be analyzed.

• Journal of Navigation and Port Research
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• v.28 no.6
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• pp.475-480
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• 2004

Author presented some study with regard to “automatic control for ship collision avoidance system” before. Those papers are to deal with unsolved problem,; in the previous study. In this paper, two issues relating to ship collision avoidance were investigated. One is to suggest a new algorithm of avoidance of a group ship. This algorithm is useful when a ship takes avoiding action for a group fish boats and a group of merchant vessels. In the stage of taking avoidance action, newly-developed algorithm was used. the other is to develop a unified model of collision risk. Generally collision risk changes according to various type of encounters. The new model is to take into account of these situations. The above-mentioned algorithm and model were verified through simulation under various encounters between ships.