Research On Underwater Unknown Source Positioning Based On Wireless Sensor Networks And Sound Propagation Loss

Ocean is a place of great importance for the existence and development of mankind. As a treasure trove of marine resources, ocean is the biggest field that hasn't yet been fully exploited on the earth, which ensures that it plays as a more and more important role in addressing tough issues as human population, resource and environment. Therefore, since 1960s and 1970s, many countries have started to march into the sea, which turned into today's huge progress in ocean development and utilization. A notable feature of modern exploitation in marine is the rapid expansion in scale and area, the fast growing of marine industry, and especially the deep-sea technology as well as the marine disaster monitoring skills.Whether in deep-sea development or marine disaster monitoring, acoustic detection and localization is extremely important. The seabed exploration requires positioning system which can be used to locate the n position of the underwater target. Underwater positioning system has a lot of kinds, such as short baseline system, ultra-short baseline system, long baseline system, inertial navigation system and combinations of navigation system, etc. However, Current underwater positioning system equipment has many short comings: high cost, complex data processing, limited Positioning range, bad real-time identification and big influence by the obstacles. In addition, the current underwater positioning development application still needs positioning system that can realize marine monitoring and support the underwater detection and localization of unknown object. First of all, marine development application background and need of high technology was summarized. Then, the technical characters, application future and research situation of underwater positioning system in detail is illustrated. The paper introduces the current research and the application background of WSN and SPL, and expounds the purpose and significance of the research. At last the paper's structure is also introduced briefly.Secondly, the new method, based on sensor networks and sound propagation loss, is applied to underwater unknown source localization. By using of this method, real-time ranging without carrier and precisely-measuring time is realized which thus greatly reduce the equipment cost and power consumption of nodes. Briefly the whole system structure and positioning process are described. Then, the paper made a brief analysis of different hydrophone arrays and known source positioning. On that basis, the paper emphatically introduces the complexity of the data processing in unknown source localization, proposes FFT frequency spectrum analysis for data processing, And then the mathematical model and localization algorithm has been put forward.Afterwards, the research performs the experimental study and the numerical simulation to the different hydrophone arrays .Numerical results and analysis validate the proposed indices and models. The influence of the multipath reflection and the hydrophone array on the location precision is analyzed. The averaged correction method based on multiple characteristic frequency is proposed and the corrected results analysis are described.In the end of paper,we has finished the tests in deep-sea tank of Shanghai Jiao tong university .In these tests, sound propagation loss principle has been applied to unknown sound source positioning to verify its feasibility and practicability. Moreover, correction method we gave is adopted to modify the data. The results show that the new method is well.In this paper, we put up forward a new method based on SPL to estimate the position of unknown acoustic source, and we carry on the research, using theoretical analysis and computer simulation, to analyze the acoustic pressure of underwater sound signal which is interfered by water background noise and multipath reflection. According to the results, we got functional relation between acoustic pressure attenuation of the unknown source and the propagation distance. Then we have done preliminary calculation and analysis in the accuracy of the unknown acoustic source localization, which provides theoretical basis for large scale and low cost acoustic positioning technology and offers a new approach for tracking the movement of complicated underwater source, such as the unknown sailing noise, underwater construction noise, biological noise, natural disasters noise.