Research On Active Passive Cooperative Target Detection In Deep Sea

With the strategic transfer of marine technology from shallow sea to deep sea,target detection technology in deep-sea background has attracted extensive attention.The active sonar carried by mobile UUV has the advantages of flexibility and ranging,but the concealment is poor;As a passive sonar,fixed long linear array has high concealment and robustness,and can realize long-range detection,but the target characteristics have a great impact on the detection and positioning performance.Therefore,this paper uses the active passive cooperative mode of the combination of movable UUV and fixed horizontal array for target detection.Firstly,using the reliable sound path propagation mode of the deep sea,the horizontal array is arranged on the seabed as a passive sonar to detect the presence or absence of the target.When a suspected target is found,it enters the active detection mode,and the UUV carries the sound source to cooperate with the seabed array to detect the target.Firstly,the characteristics of sound velocity distribution in deep-sea channel are combed and the modeling method is given;The typical sound propagation modes of deep sea and their application in underwater acoustic system are analyzed,and the reliable sound path of deep sea is emphatically studied: starting from the performance,the detection distance under different deep-sea environments is analyzed;Starting from the physical characteristics,the propagation loss of reliable sound path is analyzed and compared with other sound channels.The simulation results show that the blind area detection can be realized in a certain range by using the shadowless characteristics of the reliable acoustic path.Therefore,the horizontal array is placed on the seabed and the direct wave between the seabed array and the target is used for target detection.Secondly,the azimuth estimation algorithm under low signal-to-noise ratio and the underwater target detection method of passive sonar are studied.Aiming at the situation of low signal-to-noise ratio,the azimuth estimation algorithm based on seabed fixed horizontal array is studied.The simulation is compared with the conventional algorithm in terms of spatial spectrum,root mean square error and average background level,and the performance of the algorithm is verified by experimental data processing.Aiming at the problem of high probability of false alarm and missing alarm in single frame detection under low signal-to-noise ratio,using the long-term observation of seabed fixed horizontal array,the spatial spectrum obtained from each frame is superimposed to obtain the time azimuth history map.Based on the time azimuth history map,the target detection algorithm is used for processing,and an optimization method of parameter setting in the algorithm is proposed.The simulation results show that the target detection algorithm can stably detect the target in the image under low signal-to-noise ratio,reduce the false alarm and improve the target detection probability at the same time.When the target is detected,enter the active detection mode.In this mode,the active sonar carried by the movable UUV transmits signals,and the seabed fixed array receives the target echo.In order to obtain the real-time position information of UUV at the receiving end,the transmitting waveform of active sonar is designed,and the detection and communication integrated signal based on differential pattern delay difference coding is transmitted.At the receiving end,the communication is realized by decoding the delay difference between adjacent codes,and the pattern code is used for detection at the same time.In order to obtain the distance information,the time delay estimation algorithm is studied,including basic cross-correlation and generalized correlation time delay estimation.The performance is compared and analyzed from the aspects of correlation peak and main sidelobe ratio.In order to obtain the target position,using the obtained target azimuth and distance information,the traditional twodimensional ellipse angle hybrid positioning method is studied under the condition of constant sound velocity.Aiming at the problem of large span of sound line in the depth direction in the deep-sea background,the positioning is extended to three-dimensional,the three-dimensional ellipsoid angle hybrid positioning method is studied,and the effects of time measurement error,angle measurement error and the layout of UUV borne sound source on three-dimensional positioning accuracy are analyzed.Aiming at the situation of variable sound velocity,the sound line tracking method is studied.Based on the principle of monostatic sound line tracking,the bistatic sound line tracking method is proposed,and the results of bistatic sound line tracking are verified combined with ray model.Aiming at the problems of multiple solutions and too much calculation in bistatic acoustic line tracking,a grid matching location algorithm based on time delay information is proposed.The feasibility of the algorithm is verified by simulation based on ray model,and the effects of time measurement error and time delay error detection threshold on the performance of the location algorithm are analyzed.