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A Research on Techniques, Models and Methods Proposed for Ship Collision Avoidance Path Planning Problem
Abstract
The development of soft computing techniques in recent years has encouraged researchers to study on the path planning problem in ship collision avoidance. These techniques have widely been implemented in marine industry and technology-oriented novel solutions have been introduced. Various models, methods and techniques have been proposed to solve the mentioned path planning problem with the aim of preventing reoccurrence of the problem and thus strengthening marine safety as well as providing fuel consumption efficiency. The purpose of this study is to scrutinize the models, methods and technologies proposed to settle the path planning issue in ship collision avoidance. The study also aims to provide certain bibliometric information which develops a literature map of the related field. For this purpose, a thorough literature review has been carried out. The results of the study have pointedly showed that the artificial intelligence methods, fuzzy logic and heuristic algorithms have greatly been used by the researchers who are interested in the related field.
... It is possible to divide these studies into 4 groups according to approach types; deterministic, artificial intelligence (AI), hybrid systems and simulation. Fiskin et al. (2018) reviewed these approaches in detail with a systematic approach. ...
Collisions at sea are frequently caused by human-related factors, such as; manoeuvre timing mistakes, risk assessment failures and deficiencies in strategies for collision avoidance. These factors reveal the importance of the automation systems in providing safety of navigation. Thus, a decision support system was developed in this study that can be a reference to the ship operators in the implementation of the collision avoidance action, in case of an encounter situation involving risk of collision. Both qualitative and quantitative methods were conducted in the study. In the qualitative research process, the variable constraints in the mathematical model and the inputs of the scenarios implemented in experiments were determined based on the findings obtained from experts’ interviews. In the quantitative research process, the problem-solution was reached with the developed algorithm (ColAv_GA), which is formed based on the Genetic Algorithm and Fuzzy Logic. The developed algorithm was validated in a virtual environment using a bridge simulator, and in a real environment with an autonomous surface vehicle (ASV), with satisfactory results. The output of this research is expected to contribute to the safety of navigation. The developed algorithm can be used as a collision avoidance sub-module for autonomous ships and ASV.
... Wang et al. (2019) proposed an optimal weight distribution algorithm for collision avoidance by the dynamic path planning method. Tam et al. (2009) and Fişkin et al. (2018) also adopted this method. The problem of avoiding collision by path-following control has been widely studied (Xargay et al., 2013;Lu et al., 2018;Zhang et al., 2018aZhang et al., , 2018bQin et al., 2019;Xu et al., 2019). ...
A dynamic collision avoidance algorithm via layered artificial potential field with collision cone (LAPF-CC) is proposed to overcome the shortcomings of the traditional artificial potential field method in dynamic collision avoidance. In order to reduce invalid actions for collision avoidance, the potential field is divided into four layers, and a collision cone with risk detection function is introduced. Relative distance and relative velocity are used as variables to establish the risk of collision, and a torque named ‘speed torque’ is constructed. Speed torque, attractive force and repulsive force work together to change the speed and heading of the unmanned surface vehicle (USV). Driving force and torque are controlled separately, which makes it possible for the LAPF-CC algorithm to be used for real-time collision avoidance control of underactuated USVs. Simulation results show that the LAPF-CC algorithm performs well in dynamic collision avoidance.
... The latest shipʹs trajectory planning approaches proposed in the literature include: differential games (Lisowski 2016), fuzzy logic and game theory (Lisowski & Mohamed-Seghir 2019), the fast marching method (Liu et al. 2017), a Collision Threat Parameters Area (CTPA) technique (Szlapczynski & Szlapczynska 2017), a Voronoi diagram (Candeloro et al 2017) and Energy Efficient A* (EEA*) (Lee et al 2015). A recent comparison of different shipʹs trajectory planning methods in presented in Fişkin et al. (2018). ...
The paper presents results of ship's safe trajectory planning algorithms verification. Real navigational data registered from a radar with an Automatic Radar Plotting Aid on board the research and training ship Horyzont II were used as input data to the algorithms. The algorithms verified in the presented research include the Ant Colony Optimization algorithm (ACO), the Trajectory Base Algorithm (TBA), the Visibility Graph-search Algorithm (VGA) ant the Discrete Artificial Potential Field algorithm (DAPF). Details concerning data registration and exemplary results obtained with the use or real navigational data are introduced and summarized in the paper. Presented results prove the applicability of proposed algorithms for solving the ship's safe trajectory planning problem.
Navigational channels and approaches to ports may have bends that constitute the specific sailing conditions for ships. A vessel’s entrance into a bend and its safe passing depends on the ship’s position accuracy, turn angle, and internal and external forces influencing the ships, as well as the captain’s or pilot’s experience. In order to assure a ship’s safe navigation under specific conditions, the possibility to measure individual ship movement parameters with the use of special sensors is needed to accurately calculate the ship’s trajectory considering the specific dimensions of ships. Moreover, hydro-meteorological and hydrological limitations for ships with different parameters and maneuverability should be evaluated in advance. The article aims to develop the methodology for calculating ships’ route trajectory in channel bends and approaches to ports under special navigational conditions. The mathematical model that may be used to calculate wind velocity limitations and distance crossed by a ship during maneuvers, depending on the ship’s maneuverability, hydro-metrological, and hydrological conditions, was elaborated. The methodology was verified by the example of a few ships entering specific channel bends. Wind velocity limitations depending on wind direction for the SUEZMAX tanker and other selected types of ships during crossing navigational channel bend near Klaipeda port were calculated. The presented theoretical basis may be used by ships’ captains and pilots who plan and perform operations of vessels’ crossing the approaches to ports and navigational channel bends, as well as by navigational channels designers who plan the channel’s parameters in difficult geographical and navigational conditions. Its application may influence the safety increase of maritime transport in limited or specific areas.
This paper explores the state of the art on to methods to verify and validate navigation algorithms for autonomous surface ships. We perform a systematic mapping study to find research works published in the last 10 years proposing new algorithms for autonomous navigation and collision avoidance and we have extracted what verification and validation approaches have been applied on these algorithms. We observe that most research works use simulations to validate their algorithms. However, these simulations often involve just a few scenarios designed manually. This raises the question if the algorithms have been validated properly. To remedy this, we propose the use of a systematic scenario-based testing approach to validate navigation algorithms extensively.
This paper explores the state of the art on to methods
to verify and validate navigation algorithms for autonomous surface ships. We perform a systematic mapping study to find research works published in the last 10 years proposing new algorithms for autonomous navigation and collision avoidance and we have extracted what verification and validation approaches have been applied on these algorithms. We observe that most research works use simulations to validate their algorithms. However, these simulations often involve just a few scenarios designed manually. This raises the question if the algorithms have been validated properly. To remedy this, we propose the use of a systematic scenario-based testing approach to validate navigation algorithms extensively.
The supply chain is currently taking on a very important role in organizations seeking to improve the competitiveness and profitability of the company. Its transversal character mainly places it in an unbeatable position to achieve this role. This article, through a study of each of the key enabling technologies of Industry 4.0, aims to obtain a general overview of the current state of the art in shipbuilding adapted to these technologies. To do so, a systematic review of what the scientific community says is carried out, dividing each of the technologies into different categories. In addition, the global vision of countries interested in each of the enabling technologies is also studied. Both studies present a general vision to the companies of the concerns of the scientific community, thus encouraging research on the subject that is focused on the sustainability of the shipbuilding supply chain.
Ship collision avoidance involves helping ships find routes that will best enable them to avoid a collision. When more than two ships encounter each other, the procedure becomes more complex since a slight change in course by one ship might affect the future decisions of the other ships. Two distributed algorithms have been developed in response to this problem: Distributed Local Search Algorithm (DLSA) and Distributed Tabu Search Algorithm (DTSA). Their common drawback is that it takes a relatively large number of messages for the ships to coordinate their actions. This could be fatal, especially in cases of emergency, where quick decisions should be made. In this paper, we introduce Distributed Stochastic Search Algorithm (DSSA), which allows each ship to change her intention in a stochastic manner immediately after receiving all of the intentions from the target ships. We also suggest a new cost function that considers both safety and efficiency in these distributed algorithms. We empirically show that DSSA requires many fewer messages for the benchmarks with four and 12 ships, and works properly for real data from the Automatic Identification System (AIS) in the Strait of Dover.
TAs the rapid development of the ship equipments and navigation technology, vessel intelligent collision avoidance theory was researched world widely. Meantime, more and more ship intelligent collision avoidance products are put into use. It not only makes the ship much safer, but also lighten the officers work intensity and improve the ship’s economy. The paper based on the International Regulation for Preventing Collision at sea and ship domain theories, with the ship proceeding distance when collision avoidance as the objective function, through the artificial fish swarm algorithm to optimize the collision avoidance path, and finally simulates overtaking situation, crossing situation and head-on situation three classic meeting situation of ships on the sea by VC
the paper presents a synthesis of multistage ship's optimal control by the application of dynamic programming with neural network.
This paper presents an application of selected methods of optimal and game control theory to determine the own ship safe trajectory when passing other ships encountered in good and restricted visibility at sea. The five algorithms for determining the safe trajectory of the own ship in a collision risk situation: non-cooperative positional game, non-cooperative matrix game, cooperative positional game, dynamic optimization and kinematic optimization were compared. The considerations have been illustrated with examples of computer simulation of the algorithms to determine safe and optimal own ship trajectories in a real navigational situations at sea.
The paper describes the process of the safe ship control in a collision situation using a differential game model with j participants. As an approximated model of the manoeuvring process, a model of a multi-step matrix game has been adopted here. RISKTRAJ computer program has been designed in the Matlab language in order to determine the ship's trajectory as a certain sequence of manoeuvres executed by altering course and speed, in on-line navigator decision support system. These considerations have been illustrated with examples of a computer simulation of the safe ship's trajectories in real situation at sea when passing twelve of the encountered objects.
High accuracy navigation and surveillance systems are pivotal to ensure efficient ship route planning and marine safety. Based on existing ship navigation and maritime collision prevention rules, an improved approach for collision avoidance route planning using a differential evolution algorithm was developed. Simulation results show that the algorithm is capable of significantly enhancing the optimized route over current methods. It has the potential to be used as a tool to generate optimal vessel routing in the presence of conflicts.
Dünya denizyolu taşımacılığında konteyner taşımacılığı önemli bir paya sahiptir. Konteyner
gemileri genel olarak köprüüstünde yeni teknolojilerin kullanıldığı donanımlara sahip,
özel inşa edilmiş gemiler olmalarına rağmen deniz kazaları sıklıkla bu tip gemilerde de
yaşanmaya devam etmektedir. Konteyner gemilerinde en sık görülen kaza türlerinden biri
karaya oturmadır. Çalışmanın temel amacı konteyner gemileri karaya oturma kazalarında
insan hatası kaynaklı kaza nedenlerini belirlemek ve çözüm önerileri getirmektir. Çalışma
kapsamında Uluslararası Denizcilik Örgütü (IMO), Bütünleşik Küresel Deniz Taşımacılığı
Bilgi Sistemi (GISIS) verileri ile kaza araştırması yapan MAIB, ATSB, TSB gibi kuruluşlarının
hazırladığı 1993-2011 yıllarına ait kaza raporları incelenmiştir. Çalışmada kaza nedenleri
soruşturma raporlarından derlenmiş ve toplamda 46 adet karaya oturma kazası
incelenmiştir. Kaza nedenleri ve çözüm önerilerinin analizinde Analitik Hiyerarşi Prosesi
(AHP) kullanılmıştır. Sonuç olarak konteyner gemilerinde karaya oturma kazalarının
önlenmesinde en önemli etmenlerin sırasıyla güverte vardiya zabiti sayısının artırımı,
gemi öncesi ve gemide eğitim, köprüüstü kaynak yönetimi, gemi içi uygulamaları, gözcü
kullanılması ve son olarak ECDIS cihazı olduğu belirlenmiştir.
The paper describes the application of selected methods of optimal control theory, game theory and artificial neural networks with the aim of computer support for safe ship steering. It shows the structure of the control system and defines the task of safe steering. Also presented are methodologies and models for collision avoidance strategies. Using Matlab/Simulink language - positional game, risk game and dynamic optimal trajectory programs have been developed to provide decision support for collision avoidance at sea. A computer simulation showing safe trajectory through twelve objects at sea illustrates this.
Marine navigation consists in continuous observation of the situation at sea, determination the anti-collision manoeuvre. So it necessary to determine ship safe trajectory as a sequence of ship course changing manoeuvres. Each manoeuvre is undertaken on the basis of information obtained from the anti-collision system ARPA. This paper describes a method of safe ship control in the collision situation in a fuzzy environment based on a branch and bound method and a genetic algorithm. The optimal safe ship trajectory in a collision situation is presented as multistage decision-making process.
The paper introduces application of selected methods of a game theory for automation of the processes of moving marine objects, the game control processes in marine navigation and the base mathematical model of game ship control. State equations, control and state constraints have been defined first and then control goal function in the form of payments - the integral payment and the final one. Multi-stage positional and multi-step matrix, non-cooperative and cooperative, game and optimal control algorithms in a collision situation has been presented. The considerations have been illustrated as an examples of a computer simulations mspg.12 and msmg.12 algorithms to determine a safe own ship's trajectory in the process of passing ships encountered in Kattegat Strait.
When power driven vessels encounter at sea, they need to avoid collision. The definition of right vessel may mislead ships officers think his or her direct navigating has absolute power with this special ship. This paper will define DCPA symbols; give the cause and the method of double collision avoidance mechanism of ships at sea.
A lot of attentions are being paid to ship’s intelligent anti-collision by researchers. Several solutions have been introduced to find an optimum trajectory for ship, such as Game Theory, Genetic or Evolutionary Algorithms and so on. However, ship’s maneuverability should be taken into consideration before their real applications. This paper focuses on ship’s trajectory control problem in anti-collision maneuvering. At first, a simple linear ship maneuverability model is introduced to simulate its movement under different speed and rudder angle. After that, ship’s trajectory control is studied by considering the duration of rudder, operation distance to turning points, and maximum angular velocity. The details for algorithm design are also introduced. By giving some restrictions according to the requirements from COLREGs, the intervals for rudder angle in different circumstances can be determined by the curves. The results can give very meaningful guidance for seafarers when making decisions.
Automatic route design will help to develop electronic chart intelligence, hence to improve safety, economy and reliability of the route. In the paper rasterizing charts are used to expressed the navigation environment of the ship and the modified A* algorithm is used to compute the near optimum trajectory of a ship in given environment based on electronic chart dispiay and information system (ECDIS). By tracing Safety contours, computing obstacle areas and taking into account certain boundaries of the manoeuvring region, the problem of avoiding collisions at sea was reduced to optimization task with static constrains. Simulation using MATLAB is conducted to verify the proposed ship path planning method. The good results show the promise of this method for ship at sea.
The paper introduces a new numerical deterministic method of finding the necessary course alteration manoeuvre in a multi-target encounter situation for a given ship domain model. Its simplicity, flexibility and low computational complexity make this algorithm a useful com-ponent for real-time systems, where processing time is of importance. The algorithm is pre-sented explicitly, so that it could be directly applied in any on-board collision avoidance system or VTS system. Example results of its use are also provided.
The paper investigates the sensitivity of safe ship control to inaccurate data from the ARPA anti-collision radar system and to changes in the process control parameters. The system structure of safe ship control in collision situations and computer support programmes exploring information from the ARPA anti-collision radar are presented. Sensitivity characteristics of the multistage positional non-cooperative and cooperative game and kinematics optimization control algorithms are determined through examples of navigational situations with restricted visibility at sea.
The paper describes methods based on the branch-and-bound method, dynamic programming and genetic algorithm to determine a safe ship trajectories in the collision situation in fuzzy environment. Optimal safe ship trajectory in collision situation is presented as multistage decision-making in a fuzzy environment. The maneuverability parameters of the ship and the navigator's subjective assessment in making a decision are taken under consideration in the process model.
This article proposes a new collision avoidance decision method for ships, allowing ships at risk of collision to take timely collision avoidance measures to ensure safe passage. Through vessel traffic service (VTS) collision alert system, an analysis can be made for the probability of a ship collision and an early warning can be issued. For ships in potential collision danger, the proposed method will use Microsoft Visual Studio to establish a knowledge base of international regulations for preventing collisions at sea. Thus, based on an analysis of the situation when encountering other ships, the knowledge base will suggest an appropriate avoidance technique and use a fuzzy monitoring system, propose a novel collision danger domain that forbids entering for give-way ship. Considering the required advance for ship turning, the fuzzy monitoring system will suggest the optimal rudder steering procedure for the give-way ship, allow the ship to avoid collision and ensure navigation safety. The avoidance action taken by the ship does not consider reducing speed, instead focuses only on rudder steering. The system also integrates VTS/automatic identifica-tion system (AIS)/marine geographic information system (MGIS) by using MGIS as an AIS imaging system to facilitate the optimal decision for ship collision avoidance and deter-mine the input linguistic variables for the fuzzy logic theory via an analytical hierarchy process. The proposed method can enhance the VTS operator's decision-making abilities for colli-sion avoidance by providing a fuzzy monitoring system.
In constructing a collision avoidance system, it is important to determine the time for starting collision avoidance maneuver. Many researchers have attempted to formulate various indices by applying a range of techniques. Among these indices, collision risk obtained by combining Distance to the Closest Point of Approach (DCPA) and Time to the Closest Point of Approach (TCPA) information with fuzzy theory is mostly used. However, the collision risk has a limit, in that membership functions of DCPA and TCPA are empirically determined. In addition, the collision risk is not able to consider several critical collision conditions where the target ship fails to take appropriate actions. It is therefore necessary to design a new concept based on logical approaches. In this paper, a collision ratio is proposed, which is the expected ratio of unavoidable paths to total paths under suitably characterized operation conditions. Total paths are determined by considering categories such as action space and methodology of avoidance. The International Regulations for Preventing Collisions at Sea (1972) and collision avoidance rules (2001) are considered to solve the slower ship's dilemma. Different methods which are based on a constant speed model and simulated speed model are used to calculate the relative positions between own ship and target ship. In the simulated speed model, fuzzy control is applied to determination of command rudder angle. At various encounter situations, the time histories of the collision ratio based on the simulated speed model are compared with those based on the constant speed model.
This paper focuses on a study of the sequential action execution module for a collision avoidance system in ocean navigation. The overall decision-action process of collision avoidance consists on a Fuzzy logic based parallel decision making module and those decisions are formulated into collision avoidance actions by a Bayesian network based sequential action execution module. The presented collision avoidance system is capable of making multiple sequential actions to avoid complicated collision situations involving multiple vessels in ocean navigation while still respecting the COLREGs rules and regulations.
This paper focuses on a Fuzzy-logic based parallel decision formulation that aims to improve the safety of marine vessels by avoiding collision situations in ocean navigation. The collision avoidance of the Target vessel with respect to the vessel domain of the Own vessel has been analyzed and input and output Fuzzy Membership Functions are derived in this study. The If-Then rule based decision making process and the integrated novel Fuzzy Inference System are formulated and implemented on MATLAB software platform. Simulations are presented regarding several collision avoidance situations. Furthermore, the decision rules are formulated in accordance with the International Maritime Organization Convention on the International Regulations for Preventing Collisions at Sea (COLREGs) and expert knowledge in navigation, to avoid conflict that might occur during the ocean navigation.
Autonomous Guidance and Navigation (AGN) is meant to be an important part of the future
ocean navigation due to the associated navigational cost reduction and maritime safety. Furthermore intelligent decision making capabilities should be an integrated part of the future AGN system in order to improve autonomous ocean navigational facilities. This paper is focused on an overview of the AGN systems with respect to the collision avoidance in ocean navigation. In addition, a case study of a fuzzy logic based decision making process accordance with the International Maritime Organization (IMO) Convention on the International Regulations for Preventing Collisions at Sea (COLREGs) has been illustrated.
This study provides both a spherical understanding about autonomous ship navigation for collision avoidance (CA) and a theoretical background of the reviewed work. Additionally, the human cognitive abilities and the collision avoidance regulations (COLREGs) for ship navigation are examined together with water based collision avoidance algorithms. The requirements for autonomous ship navigation are addressed in conjunction with the factors influencing ship collision avoidance. Humans are able to appreciate these factors and also perform ship navigation at a satisfactory level, but their critical decisions are highly subjective and can lead to error and potentially, to ship collision. The research for autonomous ship navigation may be grouped into the classical and soft computing based categories. Classical techniques are based on mathematical models and algorithms while soft-computing techniques are based on Artificial Intelligence (AI). The areas of AI for autonomous ship collision avoidance are examined in this paper are evolutionary algorithms, fuzzy logic, expert systems, and neural networks (NN), as well as a combination of them (hybrid system).
When an officer of the watch (OOW) faces complicated marine traffic, a suitable decision support tool could be employed in support of collision avoidance decisions, to reduce the burden and greatly improve the safety of marine traffic. Decisions on routes to avoid collisions could also consider economy as well as safety. Through simulating the biological evolution model, this research adopts the genetic algorithm used in artificial intelligence to find a theoretically safety-critical recommendation for the shortest route of collision avoidance from an economic viewpoint, combining the international regulations for preventing collisions at sea (COLREGS) and the safety domain of a ship. Based on this recommendation, an optimal safe avoidance turning angle, navigation restoration time and navigational restoration angle will also be provided. A Geographic Information System (GIS) will be used as the platform for display and operation. In order to achieve advance notice of alerts and due preparation for collision avoidance, a Vessel Traffic Services (VTS) operator and the OOW can use this system as a reference to assess collision avoidance at present location.
The paper introduces a new method of solving multi-ship encounter situations for both open waters and restricted water regions. The method, called evolutionary sets of safe trajectories, combines some of the assumptions of game theory with evolutionary programming and aims to find optimal sets of safe trajectories of all ships involved in an encounter situation. In a two-ship encounter situation it enables the operator of an onboard collision-avoidance system to predict the most probable behaviour of a target and to plan the own manoeuvres in advance. In a multi-ship encounter the method may be used to help an operator of a VTS system to coordinate the manoeuvres of all ships. The paper contains a detailed description of collision-avoidance operators used by the evolutionary method and simulation examples of the method's results for digital maps.
A ship moving from a point A to a point B detects a moving small obstacle at close range. Hence, the ship has to perform a maneuver to avoid collision with the moving obstacle. Using a realistic model of a tanker ship, a method is proposed for computing feasible rudder command strategies for performing the collision-avoidance maneuver.
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.
Investigation on maritime accidents is a very important tool in identifying human factor-related problems. This study examines the causes of accidents, which are one of the grounding reasons of container ships, for categorization and evaluation according to the contribution rate using the Monte Carlo simulation. The OpenFTA program is used to run the simulation. The study data are obtained from 46 accident reports from 1993 to 2011. The data were prepared by the International Maritime Organization (IMO) Global Integrated Shipping Information System (GISIS). The GISIS is one of the organizations that investigate reported accidents in an international framework and in national shipping companies. The Monte Carlo simulation determined a total of 23.96% human error mental problems, 26.04% physical problems, 38.58% voyage management errors, and 11.42% team management error causes. Consequently, 50% of the human error is attributable to human performance disorders, while 50% team failure has been found.
The universality of the automatic identification system (AIS) as well as the electronic chart display and information system (ECDIS) installations will provide revolutionary solution schemes for the e-navigation era of informatization, intellectualization, and integration. Based on this concept, this study adopted ECDIS as an information platform for navigational decision support and used the real-time navigation information received by the AIS to construct predicted areas of danger (PAD) for target ships. The advantages of direct viewing via the PAD in the collision avoidance give PAD a new application. Subsequently, spatial data from an electronic navigation chart (ENC) was employed as a basis for generating geographical obstacles. Through the integration of a geographic information system (GIS) module, specially designed evolutionary computation, and collision prevention regulations (COLREGS) knowledge as well as by comprehensively considering overall navigation situations, this system conducted obstacle avoidance processing and selection of a route. The system could generate a route that could simultaneously achieve multi-ship encounter collision avoidance and geographical obstacle avoidance. This is expected to provide mariners with greater convenience when working at sea, reducing their workload. This system can also be used as a reference for collision avoidance decision making.
Vessel collision avoidance automation is a hot research area and various technologies and systems have been proposed. Verification and test of the technologies and systems, however, still remains as an open problem. Sea tests on real ships involve very high risks and tremendous costs, and are also proved to be intractable and time-consuming. Single-station simulation tests, which are adopted by most of the previous researchers, show the limitations to create the complicated navigational situations at sea. A novel approach was proposed for verification and test of vessel automatic collision avoidance systems. Multiple navigational simulators and multi-agent system technology were employed to construct the simulation platform. Experimental tests demonstrate that, with the proposed platform, effects similar to sea test on real ship, can be obtained, and the defects and limitations of sea test and single-station simulation test can be successfully diminished.
Safe ship driving depends on continue observation of the situation at sea, determinates anticollision manoeuvre, the realization of it and safe travel to the aim point. So it is important to determinate safety trajectory of ship as sequence of a single manoeuvres of ship course changing. Every manoeuvre is done on the bases of information from the anticollision system. In this paper it has been presented safe ship control taking in to account passing with many motional objects in a collision situation as multistage decision-making in a fuzzy environment. To determinate optimal safety trajectory of the ship, according to the International Rules of the Road at Sea, it is used a branch and bound method.
An automatic manoeuvring simulation is a cost-effective tool for minimising accidents and assisting design and operational planning which does not involve a human steersman but realistically emulates his/her performance. Automatic simulation of ship manoeuvring has to be able to con the ship automatically to reach a destination point whilst avoiding other ships and navigational hazards, keeping well clear of non-navigable areas, such as shallow water and shore line. One of the key problems in this task is automatic route planning and collision avoidance. This paper concentrates on developing a simple and practical method of automatic trajectory planning and collision avoidance based on an artificial potential field. The potential field method first applied in robotic research is used for ship trajectory planning and collision avoidance. The method has been adopted successfully for automatic navigation in busy, dynamic and confined seaways. In this work, 3 DOF ship manoeuvring model is used. The PID controller is designed to control the ship. An "extreme" case-the Strait of Istanbul-was chosen to investigate the performance of the system. The developed algorithm is fairly straightforward and simple to implement, and has been shown to be effective in decision support and automatic ship handling in the test case.
The ship navigation characteristics in restricted waters are considered and the current problems and deficiencies in this field are analyzed. the ship automatic collision avoidance system which can help ship maneuvering is studied. On the foundation of ship collision avoidance factors, the plan of ship path and the solution to the ship collision avoidance problems in restricted waters are introduced with artificial potential field method. The limitations of artificial potential field method are optimized though providing the concept of turning points. The reasons and principles of setting them are proposed to improve algorithm of ship avoidance path planning in confined waters. The cases of ship auto-navigation in Yangtze River entrance are conducted with Matlab program, on the foundation of mathematical model of ship movement. The differences between the navigation path before and after setting turning point are compared in restricted waters, and results of the experiments after adding the turning point are analyzed. Simulation results indicate that ships can avoid all the obstacles in restricted waters safely without crash, and find optimal path.
Collision avoidance manoeuvring has been subject to studies for many years, especially since the introduction of radar and automated data handling. Most of these studies were done on a rather practical basis, meaning that practical maritime habits in this field were adopted without much criticism. This paper presents a somewhat unconventional solution to collision avoidance problems, in which a quantitative knowledge of the own ship's dynamics can be fruitfully applied. As a slight premise, we only consider situations in which two ships are involved. Moreover the evading ship is assumed to have full navigational freedom, meaning that there are no positional restrictions, caused by shoals or bounds of depth channels. The resulting evading manoeuvre is a loop with continuously changing course and speed. It is less time consuming than former designs with piecewise constant courses. Thus the evader's intentions become more clear to the other vessel, which is initially obliged to maintain course and speed. In order to avoid “last-moment-hazardous” situations, the evading manoeuvre is proposed to be started at the earliest possible time.
Autonomous collision avoidance research for ships has been one of important research topics in the field of transportation. Artificial potential field (APF) method is widely used for path planning of mobile robots, due to its elegant mathematical analysis and simplicity. This method is especially suitable for 2-D low-speed systems. This paper proposes an improved APF method to realize the autonomous collision avoidance for ships. A novel APF model for ship collision avoidance is defined, and the velocity and maneuvering behavior of ship are introduced to the corresponding virtual force functions. The problem of local minima is addressed and solutions are presented.
A new algorithm is developed to solve the collision avoidance problem for a host ship subject to kinematic, dynamic, and moment equations and steered via rudder under the assumptions that the rudder angle and rudder angle time rate are subject to upper and lower bounds. The objective of the collision avoidance maneuver is to maximize with respect to the state and control history the timewise minimum distance between a host ship and an intruder ship. Two limiting cases are considered: (i) the intruder ship is uncooperative and keeps its course unchanged during the encounter; (ii) the intruder ship is cooperative. In both cases, a differential game formulation is avoided and the collision avoidance problem is formulated as a maximin problem of optimal control.
Four problems are investigated and their solutions compared: Problems P1 and P2 deal with uncooperative collision avoidance, while Problems P3 and P4 deal with cooperative collision avoidance.
Numerical results show that the optimal control histories always involve multiple subarcs along which either the rudder angle is kept at one of the extreme positions or the rudder angle time rate is held at one of the extreme values.
Marine collision accidents cause a great loss of lives and property. As a possible solution, the danger immune algorithm is used to achieve ship collision avoidance strategy optimization, which is a multi-objective problem concerning safety and economy. Collision avoidance operations are encoded as the individuals of optimization algorithm. In the system, ship domain and ship arena, among others, are used for collision risk evaluation to assess the fitness of individuals. Through the optimization, the navigator will obtain the optimal collision avoidance strategy to achieve safe and efficient collision avoidance. The simulations indicate that the optimization algorithm is valid.
Maritime traffic is becoming more complex every day. At present, due to technological advances and to new maritime regulations, there is increasing demand for new nautical ma-rine instruments to be installed into the bridge, and the breadth of navigational information complicates on-duty officers' de-cisions. Therefore, if decision support tools can be used to help deal with navigational decision-making, human errors arising from subjective judgments can be reduced, and sea transport safety improved. This research uses the concept of e-navigation as a framework, positioning collision avoidance path planning as the main theme, and applies an Ant Colony Algorithm (ACA) in the field of artificial intelligence to con-struct a collision avoidance model that imitates optimization behaviors in real-life applications. This model combines navi-gational practices, a maritime laws/regulations knowledge base and real-time navigation information from the AIS to plan a safe and economical collision avoidance path. Through using such planning, recommendations can be made for colli-sion avoidance and return to course. Lastly, a Geographic Information System (GIS) was used as the platform for a navi-gation decision support system, combining related navigation information, collision avoidance models and electronic charts. This is a source of reference for VTS (Vessel Traffic Service) operators and on-duty officers to assess collisions in territorial waters, achieving objectives such as warning and pre-collision preparations.
Maritime training facilities have recently introduced practical training that involves maneuvering simulators. The simulator helps the trainees realize so-called gSeamanshiph which cannot be obtained only by the classroom lectures. However, it is very difficult to judge the trainees' skills through their maneuvering on the simulator because the simulators cannot clearly demonstrate the existence of the potential collision risks. If instructors could present the cause of the risks concretely and visually, the trainees would then be able to acquire the ability to maneuver to avoid collision more effectively. Therefore, in this study, it is considered to use OZT when analyze the results of simulation. OZT is an abbreviation for gobstacle zone by targeth. This paper shows the details of this consideration.
A significant body of literature has been dedicated to research studies on construction labor productivity (CLP) and related issues, and many underlying theories and industrial practices on CLP application have been reported. However, research topics about CLP are highly diversified and there is a lack of systematic analysis in CLP-related issues. Through a systematic review of selected papers from well-known academic journals in construction management, major research areas are identified, such as factors affecting CLP, modeling and evaluation of CLP, methods and technology for CLP improvement, trends and comparisons of CLP, effects of change/variation on CLP, and baseline/benchmarking CLP. Critical reviews on these areas are presented by focusing on industry, project, and activity levels to investigate the state of the art and trends in CLP research. Gaps in research and practices are discussed and future research directions are proposed. The outcome of this paper may provide a platform for both researchers and industrial practitioners to appreciate the latest developments and trends in productivity research.
In this paper, the fuzzy inference system combined with an expert system is applied to collision avoidance system. Especially, calculation method of the collision risk by using neural network is proposed. At first, the membership functions of DCPA and TCPA are determined on the basis of simulation results using the KT equations. And then, the inference table is redesigned by using the ANFIS (Adaptive Network-based Fuzzy Inference System) algorithm. Secondly, additional factors, the ship domain, topological characteristics and restricted visibility, which can affect navigator's reasoning of the collision risk besides DCPA and TCPA are considered. Finally, MLP (Multilayer Perceptron) neural network to the collision avoidance system is applied to make up for fuzzy logic.
In this paper the author introduces a new method of collision avoidance for multi-target encounters. The method combines the qualities of a sequence of necessary manoeuvres with some optimisation elements and supports any given ship domain. First the problem of determining the optimal course alteration manoeuvre for given ship domain model and multi-target encounter situation is solved. The solution consists of analytical formulas and numerical algorithms combined to achieve low computational complexity. Then this solution is further used to construct a method of planning ship trajectories, which are safe, economic and intuitive for navigators. Example scenarios and the resulting trajectories are also provided. All of the algorithms, formulas and their derivations in the text are presented explicitly, so that they could be directly applied in any collision avoidance system.
Automatic simulation programs of ship navigation can be a powerful tool for operational planning and design studies of waterways. In such a simulation system the key tasks of autonomous route-finding and collision-avoidance are performed by the simulation program itself with no or minimum intervention of a human navigator. This is in many ways similar to automatic navigation systems in that they are designed to carry out autonomous navigation safely and efficiently without the need for human intervention or to offer advice to the navigator regarding the best course of action to take in certain situations. There are two key tasks of automatic ship navigation systems: route finding and collision avoidance. This paper presents an effective and practical method for finding safe passage for ships in possible collision situations, based on the potential field method. The general steps of implementing the potential field method applied to automatic ship navigation are described. The algorithm is fairly straightforward to implement, and is shown to be effective in automatic ship handling for ships involved in complex navigation situations.
This study conducted a series of content analyses of the articles published by International Journal of Science Education, Science Education, and Journal of Research in Science Teaching from 1998 to 2002. A total of 802 research papers were analyzed in terms of the authors’ nationality, research types and topics. It was found that researchers in four major English‐speaking countries, including the US, the UK, Australia, and Canada, contributed to a majority of the publications, but the researchers from other non‐English countries may have, to a certain extent, gradually played a valuable role on the published work. This probably implies that science education research may have progressively become an important field recognized by the international academic community. This study also found that most of the published articles were categorized as empirical studies, while position, theoretical and review papers were rarely presented in the journals. Although the research topic of students’ conceptions and conceptual change was the most frequently investigated one in these five years, a declining trend was observed when analyzed by year. Moreover, in 1998–2002, the research topics related to student learning contexts, and social, cultural and gender issues were also received relatively more attention among science educators.
This paper is based on two articles by the authors that were published in the March and September 2002 issues of the Journal of Japan Institute of Navigation.
The collision risk to multiple targets and identification of feasible evasive manoeuvres can be assessed simultaneously in true motion by judging the tip of own ship's velocity vector in relation to the display of cone-shaped collision danger regions to acquired targets. Simulator test programmes composed of scenarios with various traffic densities and different speed ranges of own ship have been carried out in order to evaluate the performance of this collision avoidance display versus ARPA (true and relative motion) displays. Experienced navigators and maritime university students with license participated as test subjects. It is shown that the proposed display is capable to facilitate more homogeneous, precise and safe evasive manoeuvres than utilising conventional judgement techniques. The superiority increases with the excess speed of own ship, traffic density and complexity.
Efficient marine navigation through obstructions is still one of the many problems faced by the mariner. Many accidents can be traced to human error, recently increased traffic densities and the average cruise speed of ships impedes the collision avoidance decision making process further in the sense that decisions have to be made in reduced time. It seems logical that the decision making process be computerised and automated as a step forward to reduce the risk of collision. This article reviews the development of collision avoidance techniques and path planning for ships, particularly when engaged in close range encounters. In addition, previously published works have been categorised and their shortcomings highlighted in order to identify the ‘state of the art’ and issues in close range marine navigation.