| The study on ship's collision risk index (CRI) and decision-making of collision avoidance model has been seamen's most concerned problem. In this field, there are a lot of questions to be resolved urgently. How to avoid collision effectively, including the determinations of ship's CRI, the opportunity of avoiding collision and the magnitude of action taking? How to complete the automation and intelligence of collision avoidance system to lighten navigators' work and mental burden? So far has not any good method for seamen's satisfaction at large. And it is also a fever task now in seafaring fields.The purpose of studying ship's CRI is to provide scientific basis for decision making of collision avoidance. We make our judgments whether ship being in collision risk or not before, only through observing original data of target ship such as range and bearing and their changes. In fact, studying and dealing with these observing data thoroughly will give us unexpected and valuable information.First of all, based on the aid of AIS (Automatic Identification System), which can give us the target ship's accurate data and will implement in 2002, we study own ship's relative motion to target vessels, define DCPA and its sign, give mathematic model of collision avoidance, produce the optimal opportunity and action taking of collision avoidance, and obtain a graph of action-taking. The optimal opportunity of collision avoidance is not as a point but as a period of time.Then, after studying the threaten degree of target vessel towards own ship in the process of collision avoidance, we present the mathematic expression of CRI, define several distances concerning with CRI. We determine some critical factors in CRI model using fuzzy decision-making method and fuzzy neural network method, explain their physics meanings, and constitute ship's CRI model by decomposing model and curve fitting. This model will meet the following qualifications:(1) Accordance with practical case;(2) Easy to obtain, especially for navigators, the more simple, the better;(3) Can be used to guide ship's collision avoidance action.Then, based on ship's CRI, we give a new concept of ship's domain for starting to avoid collision using information provided by AIS. This domain will change according to threshold GRI, and will not exist while CRI equals to zero. Finally we explain its application with an example in the process of ship's collision avoidance.Finally, we put forward a method of distributing disposal trying to resolve decision-making problems of multi-ships using the messages provided by the aid of AIS and communication patterns among ships.The innovation points of this thesis are as follows:(I) Considering multi-factor affections besides DCPA and TCPA, determine some fuzzy critical coefficients using fuzzy decision-making method and fuzzy neural network method, based on these coefficients, put forward a new model of ship's CRI which accords with practical case:where, a is a weight which reflects DCPA's affection and determines the change of CRI curve along vertical axes; k is a coefficient that reflects other affections except DCPA and determines the change of CRI curve along horizontal axes; Dist is the distance to target ship; Dcollid is a collision distance.(2) Considering own ship's relative motion to target vessels, we define DCPA and its sign, and get a set of collision avoidance curves. For target vessels whose CRIs arc-greater than threshold, give an optimal opportunity of collision avoidance and action taking.(3) Based on ship's CRI, define a new concept of "domain for starting to avoid collision". Put forward a dynamic domain for starting to avoid collision, which contains ship's CRI and will change according to threshold CRI. This domain will not exist for such targets while their CRI equal to zero. Apply this model in the process of collision avoidance.(4) Based on a complete set of ship's communication patterns, try to resolve decision-making problem of multi-ships collision avoidance usin...
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