Close-quarter Situation Research Articles

Marine Collision Avoidance Route Planning Model for MASS Based on Domain-Based Predicted Area of Danger

When the own ship encounters target ships in a close-quarter situation, an officer on watch needs to safely and timely alter the course of the vessel to avoid a collision. If ECDIS can automatically collect the navigation parameters and plot areas of collision as quasi-static obstruction areas, it will be much easier for seafarers to implement effective route planning. Hence, this study focuses on developing the MCARP model as a theoretical concept based on the DPAD model and LCD model. By operating the MCARP using ArcGIS, DPADs and several effective collision avoidance routes can be generated and imported into ECDIS based on AIS information at large scales and ample time. The graphic overlay of DPADs and effective routes on ECDIS can serve as a collision avoidance strategy reference for the personnel controlling maritime autonomous surface ships. Finally, different ships encountering situations were input into a Transas navigational simulator. The simulation results showed that own ship could avoid collisions with multiple target ships at distances larger than the preset collision avoidance distances, which also indicated that MCARP is practically feasible.

A real-time ship encounter collision risk detection approach in close-quarters situation

In order to identify ship collision risk for the security of maritime transportation in a close-quarters situation, a novel real-time ship collision risk awareness approach is proposed by developing a novel non-linear velocity obstacle set, QSD-NLVO. More specifically, the Quaternion Ship Domain model was introduced into the non-linear velocity obstacle algorithm, and the conflict position was reasonably defined. By replacing the conflict position with ship domain, the proposed method can more reasonably assess the safety radius of the conflict in different ship encounter scenarios. The presented model enhanced the accuracy of collision risk identification by replacing the collision position in non-linear velocity obstacle algorithm with quaternion ship domain. Finally, case studies were implemented to illustrate the effectiveness of the QSD-NLVO approach. The developed model may be utilized as a guide for investigating port traffic safety as well as a tool for maritime surveillance operators to monitor port traffic collision risks and increase traffic safety.

МАНЕВР ПОВЕРНЕННЯ СУДНА НА ЗАДАНУ ТРАЄКТОРІЮ РУХУ ПІСЛЯ РОЗХОДЖЕННЯ З ЦІЛЛЮ

This paper proposes a method of decomposing a set of initial bearings into subsets, each of which corresponds to a type of vessel passing strategy based on their initial parameters and the nature of the close-quarters situation. The method aims to perform a vessel evasive action and return it to the programmed (given) course. The paper investigates the problem of collision avoidance between vessels during their passing using methods of the theory of optimal discrete processes. The paper determines the most hazardous initial vessel bearing in a situation of approaching a target (another vessel, hereafter referred to as the target vessel or TV) by decomposing the set of initial bearings into subsets based on vessel movement and distance between them in the case of a close-quarters situation. The paper examines in detail the process of vessel evasive action in a close-quarters situation with a target vessel using computer simulation models in various initial conditions to choose the most optimal safe vessel passing strategy. The paper discusses the peculiarity of choosing possible safe vessel passing strategies. The paper examines different types of vessel return courses to the programmed course, depending on the situation of close-quarters situation with a target vessel, using computer simulation models. The paper determines possible risks and hazards that arise when returning the vessel to the given course during the safe vessel passing process with a target vessel. The paper presents examples of typical vessel passing situations with a target vessel at short distances using computer simulation models, including the circling maneuver of a vessel during passing with another vessel and overtaking maneuver of one vessel by another. Keywords: safety of navigation, prevention of collision of vessels, passing of vessels by evasion, the maneuver of returning the vessel to the programmed track.

Framework for Process Analysis of Maritime Accidents Caused by the Unsafe Acts of Seafarers: A Case Study of Ship Collision

Accurately describing and evaluating the effects of unsafe acts on maritime accidents is critical to establishing practical accident prevention and control options. This paper proposes a framework for the probabilistic analysis of maritime accidents caused by seafarers’ unsafe acts by incorporating a navigation simulation and dynamic Bayesian network (DBN) modeling. First, the unsafe acts of seafarers are identified according to an in-depth analysis of global maritime investigation reports. Then, a navigation simulation experiment is designed to collect the ship-handling data of seafarers during hazardous accident scenarios. Consequently, a dynamic probabilistic model is proposed using a DBN to describe the phases of maritime accidents based on the navigation simulation experiment data. Furthermore, an evolution analysis of maritime accidents is conducted to explore the causal chain of such accidents through sensitivity analysis. The typical navigational accident-collision is chosen as the case to interpret the proposed framework, considering the formation process of ship collision risks, from the occurrence of ship collision risk (phase 1) to the close-quarters situation (phase 2) and to immediate danger (phase 3). This framework is applied to explore the causal chain of collision accidents caused by the unsafe acts of seafarers.

Ship Collision Avoidance Utilizing the Cross-Entropy Method for Collision Risk Assessment

In this article, a new approach for ship-ship collision probability estimation based on the Cross-Entropy (CE) method is introduced, which can be treated as an adaptive importance sampler. It has the advantage of attaining low variance estimates of small collision probabilities, which will most often be the case in realistic scenarios. Furthermore, a risk-based Collision Avoidance (COLAV) system being able to take obstacle kinematic uncertainty and intention uncertainty into account is presented, namely the Probabilistic Scenario-Based Model Predictive Control (PSB-MPC). The collision probability estimator (CPE) is used in the risk assessment of the PSB-MPC, and tested in a simulation study, where the total system is validated. Simulation results show that the MPC is able to utilize the CPE for better risk assessment than the original version, in order to make safer decisions in close quarter situations and cases where nearby obstacles make unexpected maneuvers. It is also shown that when all vessels involved use the PSB-MPC, situations are resolved according to the traffic rules in a safe manner.

Intelligent Ship Collision Avoidance Algorithm Based on DDQN with Prioritized Experience Replay under COLREGs

Ship collisions often result in huge losses of life, cargo and ships, as well as serious pollution of the water environment. Meanwhile, it is estimated that between 75% and 86% of maritime accidents are related to human factors. Thus, it is necessary to enhance the intelligence of ships to partially or fully replace the traditional piloting mode and eventually achieve autonomous collision avoidance to reduce the influence of human factors. In this paper, we propose a multi-ship automatic collision avoidance method based on a double deep Q network (DDQN) with prioritized experience replay. Firstly, we vectorize the predicted hazardous areas as the observation states of the agent so that similar ship encounter scenarios can be clustered and the input dimension of the neural network can be fixed. The reward function is designed based on the International Regulations for Preventing Collision at Sea (COLREGs) and human experience. Different from the architecture of previous collision avoidance methods based on deep reinforcement learning (DRL), in this paper, the interaction between the agent and the environment occurs only in the collision avoidance decision-making phase, which greatly reduces the number of state transitions in the Markov decision process (MDP). The prioritized experience replay method is also used to make the model converge more quickly. Finally, 19 single-vessel collision avoidance scenarios were constructed based on the encounter situations classified by the COLREGs, which were arranged and combined as the training set for the agent. The effectiveness of the proposed method in close-quarters situation was verified using the Imazu problem. The simulation results show that the method can achieve multi-ship collision avoidance in crowded waters, and the decisions generated by this method conform to the COLREGs and are close to the level of human ship handling.

SWOT ANALYSIS OF LEADING SAFETY INDICATORS FOR COLLISION AVOIDANCE OF MARITIME AUTONOMOUS SURFACE SHIPS

Timely and reliably detecting a close-quarters situation at sea is vital to the safety of navigation. With the development of Maritime Autonomous Surface Ships (MASS), successful collision avoidance will depend to a lesser extent on humans, but rather on computers and implemented algorithms. However, the risk of collision is nowadays evaluated by humans, based on their experience, training, within a context of relevant collision regulations, adopting various safety indicators, being often subjective. The latter include: Bow Crossing Range (BCR) and Closest Point of Approach (CPA) - commonly used in seagoing practice - and recently proposed Last Time to Take Action (LTTA) or Minimum Distance To Collision (MDTC). However, for the indicators to be applicable for MASS ensuring its safe and efficient navigation, the following generic SMART requirements appropriate for leading safety indicators shall be met: Specific, Measurable, Attainable, Relevant, and Time-based. This study aims to define and analyse a set of SMART-type leading safety indicators suitable for MASS, along with their feasibility, benefits, and disadvantages, as well as reference values. To this end a comprehensive literature study has been performed, including scientific literature, as well as reports, working papers, government documents, white papers and evaluations. Finally, the obtained findings are collated using SWOT analysis and the results are formulated. These can allow for a better managerial insight into the subject of MASS collision avoidance and safety of navigation in general.

A quasi-reflection based SC-PSO for ship path planning with grounding avoidance

To improve the performance of particle swarm optimization (PSO), PSO is further improved by being combined with the sine cosine algorithm (SCA), which maintains a balance in exploration and exploitation. Furthermore, to speed up searching for the optimal path with grounding avoidance, a quasi-reflection-based sine cosine particle swarm optimization (SC-PSO) is designed. Its convergence is then proven. In the early stage, it can roam around the whole space and enhance the global search ability. In the later stage of the optimization process, the convergence ability of global optimization is strengthened. The quasi-reflection operation is introduced into the algorithm to improve the diversity of solutions. A new fitness function is developed to transform the path planning into an optimization problem, combined with the optimization standards and constraints of path length, grounding threat, collision avoidance with water targets and path smoothness, so as to realize the safe and efficient operation of ships. For grounding avoidance, the distance of the closest point of pass (DCPP), the distance of close-quarters situation of ground (DCQG), the time of close-quarters situation of ground (TCQG) and the distance from the ship to the shallows (DIS) are considered. To verify the shallow and collision avoidance of the actual ship operation, the terrain fluctuation data with the highest resolution built from global and regional data sets is used. EETOPO1 is a 1 arc-minute global relief model of Earth's surface that integrates land topography and ocean bathymetry. 3D seabed terrain and 3D collision avoidance are used for grounding avoidance in ship track planning. The results show that, compared with SCA and PSO, the new algorithm has the fastest convergence speed and the highest calculation accuracy.

A concept of critical safety area applicable for an obstacle-avoidance process for manned and autonomous ships

In times of increased automation of maritime transportation, ship collision with a stationary obstacle (allision) remains a significant problem. There are many existing solutions rooted primarily in the concept of ship domain and path-planning algorithms. However, among these, a geometrical approach to the determination of a required maneuvering area considering the dynamic nature of ship operations in close-quarters situations is still missing. Therefore, an improved concept of the CADCA (Collision Avoidance Dynamic Critical Area) is introduced for the case of ship allision. The CADCA is a deterministic zone that geometrically delimits required maneuvering space of a vessel. Its shape changes depending on the operational parameters of a ship, such as the magnitude of rudder angle, initial forward speed, or planned alteration of the course. In contrast to ship domain, the CADCA is determined using the critical distance between two objects called MDTC (Minimum Distance to Collision). Therefore, the CADCA concept can be used to appoint a position of no-return in a close-quarters situation, so as to determine the time and distance of the last-minute maneuver. An improved method of CADCA determination is introduced, along with an investigation of operational factors influencing the ship's critical area in allision scenarios. The simulations have been conducted for large passenger and container ship in encounters with various stationary obstacles differing in size and shape. The results indicate that from the operational point of view, a deflection of the rudder is the most influencing factor on the size of the CADCA, while the impact of ship speed is negligible for the investigated vessels. Besides, various applications of the CADCA are proposed and discussed for both manned and prospective autonomous vessels.

A ship domain-based model of collision risk for near-miss detection and Collision Alert Systems

The paper presents a new model of ship collision risk, which utilises a ship domain concept and the related domain-based collision risk parameters. An encounter is here described by five variables representing: degree of domain violation (DDV), relative speed of the two vessels, combination of the vessels’ courses, arena violations and encounter complexity. As for the first three variables, their values can be directly computed based on positions, courses and speeds of two vessels. The last two variables require decomposing a close quarters situation into phases. For this purpose the method utilizes a number of auxiliary parameters derived from the concept of ship domain: time of domain violation (TDV), time of domain exit (TDE), timespan of close quarters situation and vessels’ proximity, which is quantified based on the ship arena. The formulas and algorithms for determining all variables’ values are provided in detail. Once all the values are computed, the final collision risk assessment is made. Possible applications of the presented model include: AIS-based near-miss detection, Collision Alert Systems (CAS) and collision avoidance decision support systems (DSS). Case studies for those applications are provided, including examples of encounter classification and quantification of collision risk.

Reducing the risk of collision between ships in a close-quarters situation by simulating collision avoidance actions

Abstract‘Close-quarters situation’ is a term used in the International Regulations for Preventing Collisions at Sea. As the term is not precisely defined, this paper analyses the interpretations and definitions of the term by various authors or courts, based on judicial processes and judgments. In the end, the authors suggest their own definition of the term ‘close-quarters situation’. Knowing the minimum distance from another ship and the time to the closest point of approach at which collision may still be avoided by one's own manoeuvre is information that every ship's officer needs to know. In accordance with the proposed definition of the term ‘close-quarters situation’, minimum distances between ships and time to the closest point of approach in which the ship can still take action to avoid a collision by its own manoeuvring are determined by means of simulations on a navigational simulator. A total of 168 simulations were performed with three fine-form vessel sizes and three full-form vessel sizes. Due to the extensive amount of data, the paper presents the results for one vessel only.

Investigating collision risk factors perceived by navigation officers in a close-quarters situation using a ship bridge simulator

Ship collisions caused by navigation officer error significantly threaten the safety of marine navigation. An increased fear of collision for navigation officers in a close-quarters situation (CQS) may lead to failure to perform the prescribed collision-avoidance measures. This study measured the perceived collision risk (PCR) for 30 coast guard navigation officers according to their heart-rate variability in CQSs, then identified the key factors influencing measured PCR values. The PCR was measured in four types of simulated CQS, with two ships approaching each other from 2.5 nautical miles to the point of collision. The maximum PCR bearing was identified at a relative bearing of 135° based on the “own ship.” Multiple regression analysis showed that the navigator's personality factors, i.e., their onboard career and license rating, negatively (−) influenced the 95% confidence level. However, navigator age did not have significant effects on PCR. This investigation of PCR factors can help novice navigators avoid collisions due to fear or panic in a CQS with a target ship.

A Study on the Influence of the Navigator's Personal Characteristics on the Perceived Collision Risk in Close-quarter Situations

A Study on the Influence of the Navigator's Personal Characteristics on the Perceived Collision Risk in Close-quarter Situations

The ship maneuverability based collision avoidance dynamic support system in close-quarters situation

In this article, a ship maneuverability based collision avoidance dynamic support system in close-quarters situation is presented. The dynamic calculation model of collision avoidance parameter is employed to calculate the dynamic DCPA and TCPA in real-time when ship is maneuvering. Then the collision avoidance dynamic support system is developed by combining the mathematical model of ship maneuvering motion, the control mechanism of ship maneuvering motion and the dynamic calculation model of collision avoidance parameter. Following this approach, the proposed system is able to eliminate the insufficiency of neglect of ship maneuverability in the process of avoiding collision. Moreover, by incorporating the close-quarters situation into the proposed collision avoidance dynamic support system, simulation examples consisting three encounter scenarios of two ships in close-quarters situation are applied to demonstrate the significance and necessity of ship maneuverability in the process of collision avoidance and illustrate the merits and effectiveness of the proposed system. The simulation results show that the proposed dynamic support system is a reasonable, effective and practicable system for collision avoidance, particularly in close-quarters situation.

Система оцінки надмірного наближення рухомих об’єктів

Виконано синтез системи оцінки надмірного зближення суден та підтримки прийняття рішення по маневруванню для попередження аварійної події. Запропоновано спосіб зменшення завантаження обчислювачів навігаційних пристроїв шляхом зняття з обробки суден, які віддаляються від власного судна. Показано, що цей спосіб створює передумови для зменшення інформаційного завантаження оператора, керуючого процесом руху. Відзначено, що отримання даних у вигляді, готовому для прийняття рішення, дозволяє оператору віддавати команди безпосередньо під час керування, що зменшує ймовірність виникнення аварійних подій.

The Marine Safety Simulation based Electronic Chart Display and Information System

Navigation safety has a huge impact on the world economy and our everyday lives. One navigation safety simulation model in ECDIS based on international standard format (S‐57) is put forward, which is mainly involved in route plan and route monitoring. The universal kriging interpolation is used in the route planning and to compute the water depth of any place in the sea bottom. The man‐machine conversation method is taken to amend planned route to obtain autodeciding of feasibility according to ECDIS information, and the route monitoring algorithm is improved by enhancing its precision caused by screen coordinate conversion. The DCQA (distance close quarters situation of approach) model and TCQA (time close quarters situation of approach) model are adopted to judge if the close quarters situation or the risk of collision between own ship and target ship is emerging. All these methods are proven to be reliable through the navigation simulator made by Dalian Maritime University which is certified by DNV to class A.

The Probability of Collision During Vessel Overtaking

The Probability of Collision During Vessel Overtaking There are many close quarter situations at sea, especially in narrow channels. The problem of overtaking on fairways is a complex issue. Navigation, when carried out in such areas causes reduce of a vessel's safety level, it is necessary to consider limits: ship's particulars, fairway's parameters, human factor, vessel traffic. If these factors are not considered during overtaking, it will cause ship out of fairway or collision. The paper contains the probability of collision during overtaking.

Modeling perceived collision risk in port water navigation

An increase in the likelihood of navigational collisions in port waters has put focus on the collision avoidance process in port traffic safety. The most widely used on-board collision-avoidance system is the automatic radar plotting aid which is a passive warning system that triggers an alert based on the pilot’s pre-defined indicators of distance and time proximities at the closest point of approaches in encounters with nearby vessels. To better help pilot in decision making in close quarter situations, collision risk should be considered as a continuous monotonic function of the proximities and risk perception should be considered probabilistically. This paper derives an ordered probit regression model to study perceived collision risks. To illustrate the procedure, the risks perceived by Singapore port pilots were obtained to calibrate the regression model. The results demonstrate that a framework based on the probabilistic risk assessment model can be used to give a better understanding of collision risk and to define a more appropriate level of evasive actions.

The Overtaking of Ships in Restricted Areas

The Overtaking of Ships in Restricted AreasThere are many close quarter situations at sea, especially in narrow channels. The problem of overtaking on fairways is a complex issue. Navigation, when carried out in such areas causes reduce of a vessel's safety level, it is necessary to consider limits: ship's particulars, fairway's parameters, human factor, vessel traffic. If these factors are not considered during overtaking, it will cause ship out of fairway or collision. The article will contain the results of researches for overtaking manoeuvre on a traffic lane. These research was performed on training models to appoint safe distance for commence overtaking.

근접상황 선박충돌회피지원모델에 관한 연구(II)

본 연구는 근접상황 선박충돌회피지원시스템 개발을 위한 기초연구로써, 근거리 조우상황에서 항해사의 부적절한 조선으로 발생하는 선박충돌사고를 감소시키기 위한 선박충돌회피지원모델을 제시한다. 이 모델은 선박의 다양한 조우상황을 비교하고, 자선의 선회특성을 이용하여 상대선박의 침로, 속도 유지에 대한 충돌회피 가능영역과 방법을 나타냄으로써 근접상황에서도 신속한 피항동작 검토 및 결정을 가능케 하며 효과적인 충돌회피 조선을 지원할 것이다. In this paper, as a fundamental study of ship collision avoidance supporting system in close quarters situation, we propose ship collision avoidance support model for decreasing ship collision accidents those have occurred due to navigator's unsuitable maneuvering in close encounter. This model will effectively support maneuvering for collision avoidance through displaying the feasible area and the method of collision avoidance using own ship's turning characteristic about action of target ship's keeping course and velocity.