Research On Underwater Differential Positioning System Based On Sound Velocity Correction

Mariculture plays a very important role in China's fishery economy.It is an important strategic choice for the development of China's marine fishery to focus on the development of intelligent equipment for marine pastures.AUV used for monitoring mariculture environment has high requirements for underwater high-precision positioning,so the positioning technology based on underwater sound plays an important role in mariculture environment.However,due to the complex marine environment,the sound transmission line in the water will bend,which will reduce the positioning accuracy,so the sound velocity correction must be carried out in the positioning process.Under this background,this paper studies the existing AUV underwater acoustic positioning technology and sound velocity correction algorithm and their advantages and disadvantages,and proposes a sound velocity correction algorithm based on the equal gradient sound line tracking to improve the accuracy of AUV underwater differential positioning.The main research work is as follows:On the basis of summarizing the development of underwater acoustic positioning technology,this paper studies the AUV underwater positioning technology and its solution method;on the basis of comparing the advantages and disadvantages of underwater acoustic positioning technology,this paper makes an in-depth study on the surface buoy positioning technology for AUV.On the basis of summarizing the current development of sound velocity correction algorithm,the weighted average sound velocity method,equivalent sound velocity method and sound line tracking method are studied according to the propagation characteristics of sound waves.On the basis of comparing the simulation results of three sound velocity correction algorithms,the sound line tracking method is deeply studied,and the improved algorithm based on equal gradient sound line tracking is proposed.At the same time,a group of Argo data is used to study the sound line tracking method The improved algorithm is verified.The underwater differential positioning system based on sound velocity correction proposed in this paper is mainly studied from two aspects:reducing the calculation amount and avoiding the influence of system error on the accuracy.The sound velocity profile is divided into equal gradient layer and equal velocity layer by using the sound line tracking method.The calculation efficiency is improved by comparing the sound velocity profile with the threshold value.The system error is added to the positioning system to determine whether the system error has an impact on the positioning accuracy.The experiment is divided into two parts:the differential positioning system and the non differential positioning system.The simulation results show that the non differential positioning accuracy based on sound velocity correction is better than that based on differential positioning when the system error is not added into the navigation and buoy positioning systems;the differential positioning accuracy based on sound velocity correction is better than that based on non differential positioning when the system error is added into the system;the difference between the positioning accuracy of the differential positioning system based on equal gradient sound line tracking method and that of other sound velocity correction algorithms Compared with the differential positioning system,it not only improves the calculation efficiency,but also improves the positioning accuracy better than the differential positioning system of other sound velocity correction algorithms,meeting the needs of high-precision AUV positioning.