Decision Support System Based On Multi-agent Ship Collision Avoidance

Vessel collision avoidance automation is a hot research area. Since 1950s, the specialists and scholars in domestic and abroad have made broad and in-depth researches on vessel automatic collision avoidance from quantitative analysis to qualitative analysis, from mathematic models to systematic models, from expert systems to neural networks, Genetic Algorithm and fuzzy reasoning, and have also upbuilt some intelligent decision-making systems for vessel anti-collision. However, most of these systems are short of information interaction and can not simulate the negotiating abilities of navigator during the process of solving problem. And the whole schemes for anti-collision put forward by these syetems sometimes will conflict. Therefore, it is necessary to develop a kind of distributed decision-making system for vessel automatic anti-collision, which will make each vessel present a more harmonious and optimized action to avoid collisions in the whole situation.The Multi-agent system is a computing system to fulfill certain tasks by the collaboration of some independent Agents. It emphasizes the study particularly on how to harmonize the knowledge, goal, strategy and plan of a group of Agents, when they join up to take actions or solve problems. This dissertation introduced the technology and theory of Multi-agent into the study on decision-making for vessel collision avoidance, and completed some innovative work on the description of Agent for vessel, updating model for the believe of Ship-agent, promising models for the mentality of Ship-agent, decision-making algorithms for Ship-agent anti-collision and the development of Vessel Automatic Collision Avoidance Simulation Platform (VACASP for short). Then a Decision-making Support System for Multi-ship-agent Anti-Collision(DSMAC for short) was constructed based on the Multi-agent system, which means a new method was used to study the problem of vessel collision avoidance. The major contributions of the dissertation are as follows.(1) The description of Agent for vessel and construction of DSMAC. The idea was proposed to construct the DSMAC based on the technology and theory of Multi-agent. The description of Agent for vessel was made. A Hybrid Ship-agent model was proposed based on the Class Frame of VC++. According to the feature of information disposing in the collaboration of vessels for collision avoidance, a communication model based on the BDI framework and AIS information was proposed. It realized the information interaction among Ship-agents, which made it possible to simulate the negotiated ability of navigator and solve the difficult problem of vessel's understanding one another's intention of action. Finally, the working mechanism of DSMAC was established.(2)The study on the method of obtaining anti-collision information for Ship-agent. The believe of Ship-agent includes the information of own-ship, target-ship and environment. The calculating model for anti-collision parameters of dynamic target-ship and the decision model for approaching situation were proposed, which made Ship-agent possess the ability to calculate the interactional parameters with target-ship. The Electronic Chart Display and Information System(ECDIS for short) can supply DSMAC with effective and credible static information. So 'Dynamic Grid' was adopted to reorganize the S-57 standard data of ECDIS. When the DSMAC is running, Ship-agent will only dynamically load and search segmental data files instead of the whole data file of Chart, which will greatly improve the searching speed.(3)The study on Evaluation Model of Collision Risk(EMCR for short) for Ship-agent. The EMCR is one of the promising models for the mentality of Ship-agent. The idea of grade modeling was proposed to model the EMCR of dynamic target-ship. The method of sub-fuzzy qualitative judgement was adopted in the EMCR of single target-ship. The method of first-qualitative-second-quantitative judgement was adopted in the EMCR of multiple target-ship to decide the key vessel for initial decision-making. A kind of applied and simple calculating model for Minimum Safe Distance of Approaching(MSDA for short) was proposed based on the diversified approaching situations. A three-dimensional cuboid model of ship domain, which was constructed by Rectangular Searching Area and Determining Threshold of Dangerous Water Depth, was proposed for the EMCR of static obstruction.(4)The study on decision-making algorithms for Ship-agent anti-collision. The Relative Distance Between Vessels is used to denote the time for implementing the anti-collision scheme. Then the generating algorithm of decision-making for Ship-agent's avoiding single target-ship was presented. Therefore, the anti-collision scheme for head-on situation is generated based on negotiation. Using the capability of negotiation and collaboration of Multi-agent, the layered generating and optimizing algorithms of decision-making for Ship-agent's avoiding mutiple target-ships were presented, which are composed of the layers of initial scheme, optimizing and negotiation. The decision-making algorithm for Anti-grounding and Anti-reef was also presented for the existence of dangerous obstructions in the cuboid of Ship-agent. Some studies were made on the situation of single dynamic ship and some static obstructions, and the layered generating and optimizing algorithms of decision-making for Ship-agent's synthetic avoiding ship and obstruction were presented according as the Ship-agent encounters firstly the dangerous target-ship or the static dangerous obstructions, which are also composed of the layers of initial scheme, optimizing and negotiation.(5)The construction and achievement of VACASP. Adopting the program platform of Microsoft Visual C++, the VACASP was developed based on the technologies of Multi-agent and Ship Handling Simulator. A framework of communication network was proposed, which combines the IOCP based the TCP/IP protocol and the broadcast port based on the UDP protocol. A special simulation protocol based on the UDP and TCP/IP protocols and its communication mechanism were also proposed in the layer of application. The VACASP supplies users with an interface for their designing and developing decision-making algorithms for vessel automatic anti-collision. Using the platform of Visual C++ and the technology of Object Oriented Programming, the user can compile their decision-making algorithms into a DLL, and integrate the DLL into VACASP. Then simulated validation of decision-making algorithms for vessel anti-collision can be implemented by dint of the functions of VACASP.The research and application of decision-making support system for vessel automatic collsion avoidance will reduce step by step the navigators' participation in the process of vessel collision avoidance, and radically solve the influence on vessels' navigation safety caused by human factors. This application researching topic is valuable and basal, because it has hard significance to guarantee vessels' navigation safety, to avoid the occurrence of collision, grounding and reefing, to reduce the loss of life and wealth, to protect the environment of ocean.