Research On Distributed Localization Based On Underwater Communication Networks

With the completion of the Beidou Navigation Satellite System,the ground wireless positioning system has been improved.Due to the particularity and complexity of underwater acoustic channel,as well as the limitation of signal bandwidth and propagation speed,it is difficult for underwater positioning system to directly apply ground positioning technology,and it is still in the development stage.Distributed location technology based on underwater acoustic sensor network is an effective underwater cooperative target location technology at present.At present,the development direction of underwater distributed positioning technology is to increase the service life of the network,improve the communication efficiency,improve the target positioning accuracy and expand the positioning coverage area.Therefore,this paper takes the underwater distributed positioning technology as the research subject,centering on the target positioning in shallow sea cooperation as the background,aiming at several key problems of the current underwater acoustic positioning technology,carries out the research on the distributed underwater acoustic positioning method,and improves the performance of the underwater distributed positioning technology.The main research contents of this paper are as follows:Firstly,in order to get rid of the dependence of sensor nodes in distributed communication network on high precision clock in the localization process,this paper proposes an asynchronous distributed localization method based on underwater acoustic signal propagation loss ranging.The target receives the acoustic signals sent by the sensor nodes,calculates the distance between the target and each sensor node according to the signal propagation loss model,and then estimates the target position by using the least square algorithm according to the spherical intersection model.This method can use the communication signal in the transmission process by measuring the signal strength to complete the positioning,without the need for the target and node time synchronization calibration,simplify the node equipment and synchronization process.At the same time,in order to solve the problem that the ranging error of using the signal propagation loss is too large,this paper combined with the centroid optimization algorithm,and proposed a signal propagation loss location method using the weighted centroid algorithm,thus improving the positioning accuracy of the central region of the distributed network and the coverage rate of the effective location region.In addition,the feasibility of the proposed method and the specific positioning effect are verified through the design of simulation experiment and physical experiment.Durning the lastast decades,Into twenty-first Century,underwater positioning technology is more and more important in the people's increasing demand.With the development of all kinds of underwater vehicles,equipments,detectors and other techniques,the problem of multi-user underwater positioning needs to be solved as soon as possible.This paper discusses the distributed remote underwater acoustic positioning technology,which provides larger coverage and accommodates more positioning equipments.Secondly,in practical engineering applications,the sensor nodes in the distributed network are affected by the specific environment and appear irregular distribution,which leads to the impact on the positioning effect of weighted centroid algorithm.This paper proposes a distributed positioning algorithm based on two-stage node optimization.The proposed algorithm estimates the initial location region of the target through the azimuth angle and azimuth line,and calculates the optimal location region of each node combination by setting the error threshold and the optimal location region function.By comparing the overlap coefficient between the initial location region of the target and the optimal location region of each node combination,the optimal location node combination is determined.Based on the weighted centroid location algorithm,the two-stage node optimization location algorithm effectively selects the optimal location nodes,so that the target only communicates with the nodes in the optimal node combination in the long-term location process of the distributed network,which effectively improves the communication efficiency of the complex distributed network.The simulation results show that the positioning algorithm based on two-stage node selection can effectively improve the positioning accuracy and the positioning performance of distributed sensor network.Thirdly,in practical engineering applications,the fixed nodes in distributed sensor network are usually arranged on the sea bottom or seabed in the form of latent beacon nodes.Due to the influence of ocean current and tide,the node will have its own position drift in the long-term positioning process.Conventional methods,such as retrieving and relocating the nodes,or calibrating the location of the nodes through an ultra-short baseline positioning system,are complex and costly.To solve this problem,this paper proposes a modified positioning method based on a single real-time buoy sensor node.Buoy nodes can determine their position coordinates through the Beidou positioning system.In this method,the position correction function is determined by the distance relationship between the buoy node and its own position coordinates and the submersible mark.The target determines the distance relationship by receiving the communication signal of the subsurface beacon node,and corrects the location by the position correction function sent by the receiving buoy.The simulation experiment and physical experiment verify that the modified positioning algorithm based on the single buoy sensor can effectively reduce the influence of the drift of the submersible beacon node position on the target positioning and improve the positioning accuracy.Finally,in the aspect of cooperative target determination in large area underwater distributed network,a multi-AUV target location method based on mobile sensor network is proposed in this paper,which takes advantage of the problems such as limited positioning movement path and divergent positioning accuracy existing in the target location of a single underwater autonomous vehicle(AUV).When the number of AUVs in the network is two,a dual AUV localization method based on orthogonal motion is proposed.The mobile AUV is used to send the location signal to the target,and the signal arrival delay difference(TDOA)between the target and the AUV is calculated to locate the target.Compared with single AUV localization,the proposed method reduces the restriction of the AUV movement path during the localization process.The simulation results show that the proposed method can effectively reduce the influence of AUV navigation error on target positioning,and in the process of large area positioning,the proposed method has higher positioning accuracy and positioning coverage.