Research On Magnetic Anomaly Detection And Positioning Technology Of Submarine Cable

The submarine cable carries more than 90% of the world’s trans ocean communication and trans ocean power transportation,and is an important hub of the "Maritime Silk Road".With the rapid development of offshore wind power,marine ranching and other industries,the submarine cable is gradually applied to more and more civil fields.The submarine environment is complex.In addition to marine engineering,anchor damage and other man-made activities will also damage submarine cables.Subsea geological activities and marine organisms are also the inducements for frequent submarine cable failures.Once multiple submarine cables fail at the same time,the losses caused by them will be incalculable.Therefore,it is a very important and far-reaching technical research to improve the detection capability of submarine cables and determine the azimuth of submarine cables.In this paper,firstly,considering the scale factor of submarine cable,the reason why the submarine cable cannot be regarded as a single magnetic dipole model in the near-field field is explained.From the perspective of the geometric characteristics of submarine cable,the submarine cable magnetic model based on the micro element model and the submarine cable magnetic model based on the chain magnetic dipole model are proposed;Secondly,the magnetic anomaly field around the submarine cable is simulated by the multi physical field coupling software,and the above three magnetic models are numerically calculated under the same conditions and compared with the simulation,which verifies that the single magnetic dipole in the near-field field is not suitable for the submarine cable equivalent model.According to the characteristics of submarine cable,this paper proposes a positioning algorithm based on submarine cable magnetic anomaly,deduces and calculates the relevant physical quantities in the linear algorithm,constructs the corresponding fitness function for the nonlinear algorithm,and finally selects APSO algorithm combined with chain magnetic dipole model as the nonlinear positioning algorithm.In this paper,a magnetic measurement array system based on AUV(Underwater Unmanned Underwater Vehicle)platform is built,and the relevant circuit hardware in the system and the relevant logic code in the lower computer software are described in detail.The error sources of the magnetic measurement array system are analyzed,and the fluxgate sensor and the array system are corrected separately.Finally,this paper introduces the positioning experiment of submarine cable,and verifies the reliability of the magnetic measurement array system by carrying the magnetic measurement array on the AUV motion platform and conducting the magnetic field scanning of the pool.An iron cylinder with a length of 200 cm and a diameter of 20 cm is used as a simulated submarine cable to carry out the inversion of its position coordinates.The results show that in the far field(3m～7m)of the submarine cable,the positioning result using the linear positioning algorithm is better,in which the effect of the vertical gradient positioning method is better than that of the horizontal gradient positioning method.In the near field(1m～2m)of the submarine cable,the effect of the linear positioning algorithm is poor,and the positioning effect using the nonlinear positioning algorithm is better.