Research On Theory And Key Technologies Of Ship Navigation Safet Guarantee Based On AIS

Economic globalization and the increase in world trade have spurred the rapid development of the international shipping industry.The number of vessels,the tonnage of vessels,and the density of waterborne traffic are also continually increasing,leading to an increased possibility of marine accidents which is a significant threat to maritime safety and the marine environment.Nowadays,with the development and application of advanced technologies in the shipping industry,more and more new equipment is equipped on the vessels.The features and performance of the marine equipment is also constantly improving and increasing.AIS is an acronym for Automatic Identification System which consisting of shore stations and shipborne equipment.The AIS is mandatory equipped as required by the International Convention for Safety of Life at Sea(SOLAS).It operates in the Very High Frequency(VHF)band and uses the self-organized time division multiple access(SOTDMA)modulation.The positioning information of the vessel is obtained from the embedded GNSS chip inside.The AIS can effectively improve the maritime safety and provide effective technical supports for navigation,collision avoidance,maritime rescue,communication,and ship management.This paper deeply explores the AIS data and studies the theory and technology of ship collision avoidance and maritime security protection based on the AIS.The theory and key technology of collision avoidance and early warning was studied according to the recommendations of the Intermational Maritime Organization(IMO)based on the existing AIS technology.On the basis of theoretical research,the technical realization of actual system was carried out.Considering the offshore vessels that exceed the coverage of AIS shore stations,research on the positioning enhancement technology of the corresponding sea area has been carried out to improve the accuracy of positioning and to ensure the safety of navigation.The following research work is carried out in this paper.Firstly,for the problem that in the areas with large waves,disturbances,large ship intensive and navigation channels,the ships should obtain AIS information in a timely and continuous manner to improve the safety of maritime navigation,establishing a mathematical model of the probability of a transmitted signal in the presence of radio interference by using the probability of the AIS signal in the parameters of the communication channel system.At the same time,by evaluating the AIS reporting interval specified by ITU-R,a reasonable channel protection value corresponding to the probability of receiving the AIS signal is proposed.The research results have important scientific and practical value for the calculation of the probability of maritime signal transmission in the AIS communication channel.Based on this research,a maritime security early warning probability algorithm based on AIS signal sensing is proposed.According to the characteristics of marine accidents and the experience of maritime navigation,through the analysis of the ship collision avoidance process,principle and collision avoidance rules,effective maritime navigation safety warning information can be given.The research results presented in this paper can assist the crew on board to achieve the purpose of collision avoidance by using the AIS system combining with the navigation experience.Secondly,for the collision problem caused by human operation,a detection and collision prevention system is established.The collision assessment is used to detect and immediately issue a collision risk warning to ensure safety at sea and avoid casualties.In the study of this paper,the collision risk index(CRI)is the core of the system.CRI is affected by many factors,including the nearest point arrival time(TCPA),the nearest point arrival distance(DCPA),the distance from the target ship and the relative orientation.The calculation of DCPA and TCPA uses the shipborne AIS equipment weighting method,and the CRI calculation uses neural network and fuzzy theory.Based on the research of this paper,the ship collision avoidance algorithm based on AIS information is proposed.Based on the detailed analysis of the action strategy of the ship collision avoidance,the range of action and the encounter situation of the target ship,the mathematical model of risk assessment is established.The simulation experiments of collision assessment and early warning using AIS information verify the effectiveness of the algorithm.Thirdly,based on the mathematical model of collision avoidance,a new system using AIS information is designed.This analyzes the format of AIS message which is a basis for receiving data from the AIS system to the system.The system software is designed by using C#language,and the software structure is divided into component modules.The system hardware is implemented with industrial standards.The operation results show that the system can respond to the user's inquiry,which provides the dynamic and static information of the ship,target ships in real time and warning when a high probability of collisions is detected.Finally,the GNSS augmentation system based on the AIS is researched to improve the positioning accuracy of the GNSS system.Two solutions for GNSS augmentation system based on AIS are proposed,namely,shipborne AIS forwarding the AIS shore station enhanced signal and augmentation system based on the AIS shipborne station.The solutions can improve the positioning accuracy of the ship and enhance the safety of the maritime navigation in the ship-intensive sea area where the AIS shore station differential enhanced signal cannot be covered.The experimental results show the availability of the system.Therefore,this thesis has important theoretical and practical significance for effectively preventing collision of ships and ensuring the safety of navigation of ships at sea.This thesis was supported by the key project of National Natural Science Foundation of China(61231006).