| For the low-frequency and very low-frequency characteristic line spectrum of the target radiated noise in water,the passive detection of vector sensing can break through the oversize problem of the traditional array,and the vector hydrophone has received much attention because it can get the target position information by single one.However,the directional accuracy of the vector hydrophone is severely limited by the signal-to-noise ratio of the received signal,and it drops sharply as the target distance increases,which limits the operational coverage radius of the platform in the water,and it is difficult to adapt to the urgent needs of the current navy for long-range strikes.Since the filtering and noise reduction method under low SNR tends to affect the amplitude and phase of the signal,which affects its orientation accuracy and robustness,so the vector acoustic orientation with low SNR is still a scientific problem to be solved.It has been shown that the use of nonlinear stochastic resonance can convert noise energy into signal energy,which has significant enhancement ability for weak signals under strong background noise,but its amplitude nonlinear gain characteristics make it difficult to directly use in vector acoustic orientation.In this paper,the amplitude response characteristics of classical bistable stochastic resonance are analyzed and propose three stochastic resonance methods with linear response characteristics.The enhanced vector orientation performance and the effect of the vector orientation accuracy under low SNR condition are verified by simulation and marine experiment data.The main contributions and innovations of this paper are as follows:(1)The vector acoustic orientation model influenced by amplitude gain and phase offset is established.The influence of preprocessing methods such as vector acoustic signal denoising on directional performance is theoretically analyzed.It is clear that the vector sound signal preprocessing method should satisfy the signal amplitude linear gain and phase consistency,and the time domain resampling average sound intensity method and phase-aligned frequency domain resampling cross-spectrum sound intensity method are constructed,which effectively solves the problem of large orientation error caused by signal phase inconsistency between vector sound channels.(2)The amplitude gain characteristics of the classical bistable stochastic resonance system are analyzed.Based on the amplitude response theory,a vector parameter orientation method with single parameter tuning linear response stochastic resonance enhancement is proposed,which effectively improves the the orientation accuracy under low SNR condition,the simulation results show that the orientation error of no more than 2°can be guaranteed when the signalto-noise ratio is as low as-25 d B,which has a great performance improvement compared with the traditional method.(3)A piecewise linear stochastic resonance enhanced vector acoustic orientation method is proposed.In addition to the small signal linear gain region,there is a special large signal linear gain region.The simulation results verify the piecewise linear stochastic resonance enhanced vector acoustic orientation method.It shows that it can achieve better directional performance than traditional methods under low SNR conditions.(4)A smooth piecewise linear stochastic resonance enhanced vector sound orientation method is proposed,which broadens the linear gain interval and improves the stability of the linear gain coefficient.The simulation found that the orientation angle error does not exceed 0.5 degrees when SNR is not lower than-20 d B,which effectively improves the vector sound orientation accuracy.(5)The low-frequency vector acoustic orientation marine experiment based on single vector sensing is designed and implemented.The performance of the proposed methods is compared and analyzed.The feasibility and effectiveness of the application of stochastic resonance enhanced acoustic vector orientation method are verified. |
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