Research Of Distributed Cetaceans Location Technology Based On TDOA

Underwater acoustic localization of cetaceans using cetacean sounds is an effective method to study the habits and activities of cetaceans,which is essential to the protection and behavioral research of cetaceans.The activity range of cetaceans is usually up to tens of kilometers,and long-baseline positioning system is an effective solution to achieve large-scale positioning of cetaceans.However,the positioning of cetaceans faces the following problems:(1)The calls of cetaceans are non-cooperative signals.(2)The sound signal is attenuated after long-distance propagation,resulting in a low signal to noise ratio of whale sound received by the acquisition node.(3)In the distributed long-baseline positioning system,high-precision synchronous sampling between acquisition nodes is needed to reduce the impact on positioning error.Aiming at the above key issues,the method and system of cetacean localization are studied in this paper.The main research work is as follows:1.Aiming at the large-scale and non-cooperative requirements of cetaceans positioning and the high autocorrelation characteristic of most click signal and whistle signal in cetacean sound,the positioning method based on time difference of arrival(TDOA)is designed based on the distributed long-baseline multi-node positioning system topology.Aiming at the characteristic that the traditional Chan algorithm is sensitive to noise and the repetition frequency of most click signals is high,the Kalman filter and Chan algorithm are combined to improve the anti-noise performance and positioning accuracy of the TDOA positioning method..2.Aiming at the low signal-to-noise ratio of cetaceans' sound signal after long-distance propagation,which affects the positioning accuracy,a signal acquisition node with high SNR and large dynamic range is designed.Aiming at the high output impedance of the hydrophone,high input impedance preamplifier circuit is designed by using the bootstrap circuit structure to achieve impedance matching between the hydrophone and the preamplifier circuit.In addition,low-noise signal conditioning circuit is designed based on the circuit noise model,which improves the signal-to-noise ratio and dynamic range of the signal acquisition node.3.Aiming at the problem of target positioning accuracy caused by synchronous sampling error between signal acquisition nodes,the high-precision synchronous sampling method based on the master-slave dual phase-locked loop is proposed.In this method,the pulse per second(PPS)provided by the satellite timing system is used as time reference,and the main phase-locked loop is designed based on the digital phase-locked loop technology to achieve high-precision synchronization between the PPS and the sampling reference signal;then the high-precision synchronization between the analog-to-digital converter(ADC)Data ready signal and the sampling reference signal is achieved by applying the ADC as a frequency divider in the phase-locked loop.Based on the master-slave dual phase-locked loop,high-precision synchronous sampling between the distributed signal acquisition nodes is realized.4.The prototype of the cetacean positioning system was built and the underwater target positioning verification experiment was completed.The experimental results show that compared with the traditional Chan algorithm,the target positioning error of the localization algorithm which combines Kalman filter and Chan algorithm is reduced by 34.9%,which verifies the effectiveness of the cetacean positioning method and system.