The Positioning Technology Of Underwater Mobile Nodes Based On Multiple Surface Beacon Network

With humans' more effort to explore the ocean,various kinds of underwater facilities are developed.Autonomous underwater vehicles(AUV),underwater gliders(UG)and other unmanned underwater platforms are hot topics in the oceanic research fields.In the long-term underwater mission,the underwater unmanned platforms carrying various kinds of sensor equipment need to obtain their location information continuously.At the same time,the underwater sensor data will not be valuable unless they are associated with location information.Therefore,accurate underwater mobile node positioning technology is meaningful for underwater navigation,obstacle avoidance,underwater data collection,marine environment monitoring and other applications.However,the harsh underwater environment takes more challenges to underwater communication and localization.we study the positioning technology of underwater mobile nodes,focusing on the positioning technology based on multiple surface beacon network.In the localization algorithm based on time difference of arrival(TDOA),upon receiving the positioning message,the underwater mobile nodes record the arrival time and then calculate its own position through time difference of arrival of the positioning messages which are sent synchronously.Considering the harshness of the underwater environment,the positioning messages sent by surface beacons may not be received by the underwater mobile nodes reliably.To accomplish localization when some positioning messages are missing,we propose a virtual beacon enhanced underwater mobile nodes TDOA positioning algorithm and carry out the error analysis and simulation analysis.In addition,to improve the positioning performance at the edge of the positioning topology,a virtual beacon search strategy with edge correction is proposed.The results show that the virtual beacon enhanced TDOA positioning algorithm can provide more positioning opportunities than the TDOA method with little loss on positioning accuracy.In multiple surface beacon network,there is a sending order for the positioning message.the underwater mobile nodes will face the error accumulation problem caused by long positioning interval.Aiming to improve the positioning performance,we study the underwater mobile node positioning algorithm based on filtering methods.The underwater mobile nodes build the state equation and measurement equation based on the motion information and the time difference of arrival.The extended Kalman filter and the unscented Kalman filter algorithm are used to realize the position tracking of the underwater mobile node.Considering the influence of fixed weight on the filtering performance,we propose an adaptive filtering algorithm with optimized weights.The simulation analysis results show that proposed method can achieve good positioning performance.To verify the feasibility and performance of the proposed positioning method,a sea trial in the South China Sea is carried out.We analyze the localization performance of the ship-based mobile node in minimum localization system,fixed topology and cross-topology situations.The results show that the localization error is low.In addition,the localization results of the underwater glider during the dive-and-rise mission show the good performance.This paper studies the positioning technology of underwater mobile nodes based on multiple surface beacon network,which can achieve accurate and stable passive localization of underwater mobile nodes.It contributes to building the underwater Bei-Dou system.