A passive ranging method based on deep sea angle of arrival structure

Abstract

The application discloses a kind of passive ranging methods based on deep sea angle of arrival structure, belong to underwater acoustic positioning and identification technical field.A kind of passive ranging methods based on deep sea angle of arrival structure, method includes: first step: N vertical linear array is placed in deep sea and respectively collects vertical array data and environmental parameter;Second step: two kinds of parameters collected are respectively carried out vertical dimension conventional beam forming and the angle of arrival θ (R) of bottom reflection acoustic ray is calculated using sound field calculation software;Third step: by calculating, respectively, the angle of arrival estimation value θ0 of bottom reflection is obtained, and it is combined with measured hydrological parameter and bottom parameter using fitting estimation parameter, first, the angle of arrival of acoustic ray corresponding to different distances is predicted using sound field calculation software, then the parameters a and b of mapping formula are estimated, and finally, passive is realized by vertical array estimation acoustic ray angle of arrival.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustic positioning and identification technology, specifically a passive ranging method based on deep-sea angle of arrival structure. Background Technology

[0002] Deep-sea sound source localization has always been a hot topic in marine acoustics research, and many experts and scholars at home and abroad have studied it over the past few decades.

[0003] Compared to shallow seas, the deep sea has a unique sound velocity profile structure and seabed topography. In a typical deep-sea environment, influenced by factors such as the sound velocity profile and boundary conditions, sound source signals reach the receiving point through multiple sound propagation modes, exhibiting different propagation characteristics and performance. In ray acoustics theory, the deep-sea shadow region refers to the area inaccessible to direct and inverted sound rays, where the sound field energy is mainly contributed by seabed reflected sound, which suffers significant reflection loss. In the first shadow zone, the contribution of secondary and higher seabed reflections to the sound field is negligible due to large energy attenuation. Primary seabed reflections make the main contribution to the sound field, mainly including four paths: seabed reflection path (BR), sea surface-seabed reflection path (SBR), seabed-sea surface reflection path (BSR), and sea surface-seabed-sea surface reflection path (SBSR). The angles of arrival of these four sound paths to the receiving point are very similar. Moreover, in the first shadow zone of the deep sea, the angle of arrival of the sound rays changes monotonically with distance. Environmental parameters such as sea depth, transmission and reception depth, and seabed composition have little impact on the angle of arrival. Therefore, the angle of arrival of the sound rays in the first shadow zone of the deep sea has the characteristics of environmental tolerance and distance sensitivity. Summary of the Invention

[0004] The purpose of this invention is to provide a passive ranging method based on deep-sea angle of arrival (AHA) structures. This method estimates the AHA of reflected sound rays from the seabed and combines this with a linear mapping relationship between the AHA and the logarithm of the distance obtained through sound field modeling to achieve passive ranging of targets within the first shadow zone. The advantages of this method are that the AHA is easily estimated using conventional beamforming in the vertical dimension, and it is applicable to both surface and underwater targets.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a passive ranging method based on a deep-sea angle of arrival structure, the method comprising:

[0006] Step 1: Deploy the N-element vertical receiving array in the deep sea and collect vertical array data and environmental parameters respectively;

[0007] Step 2: The two types of data collected are used for vertical conventional beamforming and the sound field calculation software is used to calculate the angle of arrival θ(R) of the reflected sound rays on the seabed.

[0008] Step 3: Calculate and obtain the estimated value of the seabed reflection angle θ0, and then use... Fitting and estimating parameters and

[0009] Step 4: Substitute the parameters obtained in Step 3 into the formula. The estimated distance is obtained.

[0010] Preferably, the vertical array data includes the sampling rate F of an N-element vertical receiving array deployed in the deep sea. s Array element spacing d and time-domain sound pressure signal p n (k);

[0011] Time-domain sound pressure signal p n The processing formula for (k) is p n (k)(k=1,2,L,T·F s (n = 1, 2, ..., N);

[0012] Environmental parameters include measured hydrological parameters and seabed parameters, with the seabed parameters obtained by querying historical databases.

[0013] Preferably, the vertical dimension conventional beamforming processing formula is as follows:

[0014]

[0015] Time-domain sound pressure signal p n (k) Perform a Fourier transform to obtain the frequency domain signal P. n (f), frequency domain signal P n (f) selects the upper and lower limits of the processing frequency band, denoted as f. h and f l That is, f∈[f l f h ];

[0016] P n (f) and f∈[f] l f h Substituting into the conventional beamforming processing formula in the vertical dimension, with θ in the range of 0°-90°, the θ corresponding to the maximum value of B is the estimated value of the seabed reflection angle of arrival θ0.

[0017] Preferably, the seabed parameters are obtained by combining measured hydrological parameters and historical database queries, and the seabed reflected sound ray arrival angle θ(R) at different distances from the center depth of the array is calculated using sound field calculation software.

[0018] Preferably, the linear mapping formula between the angle of arrival θ(R) of the reflected sound rays from the seabed and the logarithm of the distance is used. The fitting yielded the estimated values ​​of parameters a and b as follows: and

[0019] Preferred, p n (k)(k=1,2,L,T·F s (n = 1, 2, L, N) represents the time-domain sound pressure signal received by the nth array element for T seconds, where n and T represent the nth array element and the time of reception for T seconds, respectively.

[0020] Preferred, Let c represent the speed of sound, J represent the number of beams, and let θ1 = -90° be the direction perpendicular to the sea surface upwards, and θ be the direction perpendicular to the sea surface downwards. J = 90° direction.

[0021] Preferably, R in θ(R) takes values ​​within the first shadow region.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] A linear mapping relationship is proposed between the angle of arrival θ of the reflected sound rays on the seabed and the logarithm of the distance lg(R), with the formula θ≈alg(R)+b;

[0024] Combining measured hydrological parameters and seabed parameters, the acoustic field calculation software is first used to predict the ray arrival angle corresponding to different distances. Then, the mapping formula parameters a and b are estimated. Finally, the ray arrival angle is estimated through a vertical array to achieve passive ranging.

[0025] This method is applicable to passive ranging of surface / underwater targets within the first shadow zone of the deep sea and has strong environmental tolerance. Attached Figure Description

[0026] Figure 1 These are the two stretching lines of this invention when measuring 130° and 310°;

[0027] Figure 2 This is the CTD measured sound velocity profile of the sea area according to the present invention;

[0028] Figure 3 This invention provides the deep-sea acoustic ray arrival angle-distance relationship curve predicted by the acoustic field calculation software of this invention, which combines measured hydrological parameters and historical sediment parameters.

[0029] Figure 4 This is the result of curve fitting parameter estimation in this invention;

[0030] Figure 5 The present invention provides the results of angle of arrival estimation and distance estimation for a 130° survey line.

[0031] Figure 6 This invention presents a comparison of actual and estimated distances during 130° surveying, along with statistical data on distance measurement errors.

[0032] Figure 7The present invention provides the estimated angle of arrival and distance for a 310° survey line.

[0033] Figure 8 This invention provides statistics on distance measurement errors when measuring a 310° line.

[0034] Figure 9 This is a flowchart of the passive ranging algorithm based on the deep-sea angle of arrival structure of the present invention. Detailed Implementation

[0035] Example 1:

[0036] Please see Figure 1-9 This invention provides a technical solution: a passive ranging method based on deep-sea arrival angle structure, the specific implementation of which is as follows:

[0037] (1) For an N-element vertical receiving array deployed in the deep sea, the sampling rate F s The element spacing is d, and the time-domain sound pressure signal received by the nth element for T seconds is denoted as p. n (k)(k=1,2,L,T·F s (n = 1, 2, ..., N).

[0038] (2) For the time domain signal p n (k) Perform a Fourier transform to obtain the frequency domain signal P. n (f) The upper and lower limits of the selected processing frequency band are denoted as f. h and f l That is, f∈[f l f h After performing conventional beamforming processing in the vertical dimension, the following is obtained:

[0039]

[0040] Where c represents the speed of sound, J represents the number of beams, and the direction perpendicular to the sea surface upwards is defined as θ1 = -90°, and the direction perpendicular to the sea surface downwards is defined as θ. J = 90° direction.

[0041] (3) Take the arrival angle θ in the range of 0°-90°. The θ corresponding to the maximum value of B is the estimated value of the seabed reflection arrival angle, denoted as θ0.

[0042] (4) By combining measured hydrological parameters and historical database queries to obtain seabed parameters, the seabed reflected sound ray arrival angle θ(R) at different distances from the center depth of the array is calculated using sound field calculation software (R is taken within the first shadow zone). The linear mapping formula between the seabed reflected sound ray arrival angle and the logarithm of the distance is then used. The fitting yielded the estimated values ​​of parameters a and b as follows: and

[0043] (5) Substitute the actual estimated angle of arrival of the seabed reflected sound rays into the equation. The formula yields the target distance estimate.

[0044] Figure 1 The test vessel was positioned along two distance measurement lines at 130° and 310°. The experiment was conducted in the deep waters of the South China Sea in March 2021, at a depth of approximately 3600m. Figure 2 This is a CTD-measured sound velocity profile of the sea area.

[0045] The experiment used a buoy (vertical array) for receiving signals; the sound source was a self-made towed sound source, in which the 130° survey line (going) transmitted a 1.5kHz to 2kHz LFM signal, and the 310° survey line (returning) transmitted a 2kHz to 3kHz LFM signal, with a transmission depth of about 40m. A TD was attached to the towed fish to monitor the transmission depth.

[0046] Figure 3 The arrival angle-distance relationship curves of deep-sea acoustic rays predicted by acoustic field calculation software combined with measured hydrological parameters and historical sediment parameters are presented. Figure 4 The results are the parameter estimation results for curve fitting. The estimated values ​​of a and b are -55.89 and 90.24, respectively.

[0047] Figure 5 The estimated angle of arrival and distance measurement results for sound ray of survey line 1 are given. Figure 6 The results show that the ranging performance is stable for 153 minutes of simulated noisy targets, with an average ranging error of 6.5%.

[0048] Figure 7 The estimated angle of arrival and distance measurement results for sound ray of survey line 2 are given. Figure 8 The results show the comparison between the actual distance and the estimated distance, as well as the statistics of the ranging error.

[0049] The results show that the ranging performance for 133 minutes of simulated noisy targets is stable, with an average ranging error of 4.4%.

Claims

1. A passive ranging method based on a deep-sea angle of arrival structure, the method comprising: a first step of placing an N-element vertical array in a deep sea and collecting vertical array data and environmental parameters respectively; a second step of performing vertical dimension conventional beamforming on the collected data and calculating the angle of arrival θ(R) of the seabed reflected sound line by using sound field calculation software; Third step: the arrival angle estimate value θ0 of the seabed reflection and the arrival angle estimate value θ0 of the direct path reflection are obtained respectively by calculation Fitting the estimate parameters and ; Step 4: Substitute the parameters from Step 3 into the formula Obtain the estimated distance; Vertical array data includes the sampling rate F of an N-element vertical receiver array deployed in the deep sea. s Array element spacing d and time-domain sound pressure signal p n (k); Time-domain sound pressure signal p n The processing formula of (k) is p n (k) (k = 1, 2, …, T·F s n = 1, 2, …, N); the environmental parameters include measured hydrological parameters and seabed parameters, and the seabed parameters are obtained by querying a historical database; combined with the measured hydrological parameters and the seabed parameters obtained by querying the historical database, the angle of arrival θ(R) of the seabed reflected sound line corresponding to different distances at the center depth of the array is calculated by using the sound field calculation software, and R in θ(R) takes a value within a first shadow zone range; Using the linear mapping formula between the bottom reflected sound ray angle of arrival θ(R) and the logarithm of the distance Fitting, the parameter a and b estimates are obtained as and .

2. The method of claim 1, wherein: a vertical dimension conventional beamforming processing formula is ； Time-domain sound pressure signal p n (k) Fourier transform to obtain frequency-domain signal P n (f), frequency-domain signal P n (f) to select the upper and lower limits of the processing frequency band, respectively, f h and f l , that is, f ∈ [f l ,f h ] P n (f) and f ∈ [f l ,f h ] are substituted into the vertical dimension conventional beamforming processing formula, θ is in the range of 0°-90°, and the θ corresponding to the B maximum value is the seabed reflection arrival angle estimation value θ0.

3. The method of claim 1, wherein: p n (k) = (k = 1, 2, …, T · F s , n = 1, 2, …, N) represents the time-domain sound pressure signal received by the nth array element for T seconds, wherein n and T represent the nth array element and the reception of T seconds, respectively.

4. The method of claim 2, wherein: where c denotes the sound speed, J denotes the number of beams, and the upward direction from the sea surface is taken as θ1= -90° and the downward direction from the sea surface is taken as θ J = 90°.

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