Research On TDOA Localization Method Based On Underwater Wireless Sensor Network

As one of the most focused technologies,underwater sound source localization(USSL)technology is applied to underwater source detection and underwater information processing.Compared to Time of Arrival(TOA)localization technology requires accurate time synchronization between the sensor and the source to be located,Time Difference of Arrival(TDOA)localization technology only needs to keep time synchronization between the sensors.Regardless of the initial time of sound wave emitted by the source,it is more suitable for underwater complex localization scenes.This thesis mainly focuses on the research of underwater sound source location method and its derivative algorithm based on TDOA.The main work is concluded as follows:1.This thesis proposes a TDOA localization method based on improved Two-Stage Weighted Least Squares(TSWLS)algorithm.Considering that the existing TSWLS algorithm will be faced with the problem of declining localization accuracy under the condition of large noise,it is because the algorithm abandons the noise square term in the calculation process.In this thesis,the time difference equation is introduced on the basis of the TSWLS algorithm,and the original position equation is reduced to avoid the introduction of the noise square term.After obtaining the initial estimation of the sound source position with high accuracy,the Taylor expansion method is used to process the intermediate variable,and the positioning equation is constructed according to the nonlinear relationship between the intermediate variable and the sound source position error.After the initial estimation is corrected,a higher precision is obtained.The simulation results show that the proposed algorithm has more significant localization advantages under the condition of high noise.2.This thesis presents a joint localization method of TDOA and Frequency Difference of Arrival(FDOA)under the influence of sensor disturbance error.Considering the problem of sensor error disturbance in underwater moving source location,based on the existing twostep weighted least squares algorithm,the sensor disturbance error is introduced to estimate the position and velocity of the sound source,and then the Taylor expansion of sensor position variable and velocity variable is derived.It is substituted into the first step of the algorithm to correct the initial estimate of the source position and velocity and obtain more accurate estimate of the sound source.Simulation results show that the proposed algorithm can achieve Cramer-Rao Lower Bound(CRLB)accuracy.3.In this thesis,a joint localization method of TDOA and Angle of Arrival(AOA)based on underwater scatterer information in Non-Line of Sight(NLOS)environment is proposed.Due to the large bias of existing algorithms in estimating the information of underwater scatterers,a new method based on Weighted Least Squares Circle Fitting(WLS-CF)algorithm is proposed in this thesis.The multiplicative noise of the measurement error in CF algorithm is suppressed by WLS algorithm,and the scatterer information with high precision is obtained.Then,the scatterer is regarded as a virtual sensor to participate in source localization.Considering that the scatterer position information is arranged as a Uniform Circular Array(UCA)special localization scenario,an improved Constrained Weighted Least Squares(CWLS)source estimation algorithm for underwater sound source is proposed,and the optimal solution of source location is given by constraint iteration.Finally,simulation results show that the proposed algorithm is superior to the existing algorithms.