Typical deep sea sound velocity profile active inversion method based on reliable sound path

Abstract

The invention discloses an active inversion method of a typical deep sea sound velocity profile based on a reliable sound path, and relates to acoustic inversion of marine environment parameters. The method comprises the steps that based on ocean mode data or measured data, a sound propagation model is combined, and a sea surface scattering echo arrival pitch angle and arrival time two-dimensional curve under different deep sea sound velocity profiles is obtained through simulation; a vertical receiving array carrying an active sound source is arranged at the bottom of a deep sea, and sea surface scattering echoes obtained by active emission are subjected to beam forming to obtain actually measured sea surface scattering echo arrival pitch angle and arrival time two-dimensional curves; comparing the two curves to obtain sound velocity profile expression parameters under the optimal matching of the two-dimensional curve, and obtaining deep sea sound velocity profile estimation by using the expression parameters. And a full-water-depth sound velocity profile can be obtained without covering a measurement system of a whole water body. A traditional receiving and transmitting split double-subsurface buoy system does not need to be used for obtaining a deep sea water sound velocity profile between receiving and transmitting, and deep sea sound velocity profile estimation can be achieved by placing a single receiving and transmitting assembly on a system on the seabed.

Description

Technical Field

[0001] This invention relates to an acoustic inversion method for deep-sea acoustic velocity profiles based on reliable acoustic paths, and particularly to an inversion method for obtaining the arrival pitch angle and arrival time curves of sea surface scattered echoes using a combined transceiver seabed platform and its vertical receiving array, obtaining copy fields of the arrival pitch angle and arrival time of sea surface scattered echoes under different deep-sea acoustic velocity profiles using marine environmental data, and obtaining deep-sea acoustic velocity profile estimation by matching the two-dimensional curves of the arrival pitch angle and arrival time of sea surface scattered echoes. Background Technology

[0002] For active and passive sound detection systems based on reliable acoustic paths, they are often deployed on the deep seabed, utilizing the low propagation loss within the direct sound range to achieve long-range detection. Ideally, the detection system is located near the seabed year-round, and the changes in the deep-sea sound velocity profile are unknown. However, the targets of the detection system are mainly located in the deep-sea surface, and the surface sound velocity profile changes significantly over time. These changes affect the grazing angle and propagation time of sound rays, thus impacting the accuracy of the detection system's target distance and depth estimation. Therefore, there is an urgent need to develop a deep-sea sound velocity profile inversion method based on the reliable acoustic path model.

[0003] Previous methods for deep-sea sound velocity profile inversion primarily relied on long-distance horizontal sound propagation signals. These methods estimated the deep-sea sound velocity profile using the propagation characteristics and parameters of sound rays or normal modes through matching, generally yielding only large-scale horizontal average results. To improve the accuracy of deep-sea sound velocity profile inversion in smaller areas, this patent proposes an active detection mode utilizing reliable sound paths. This involves emitting sound rays at different angles to the sea surface, which are then scattered back to the seabed and received by a vertical array. This yields two-dimensional curves of the arrival pitch angle and arrival time of the scattered echoes from the sea surface, thus obtaining the propagation time of sound rays traversing the entire deep-sea body at different angles. Matching these two-dimensional curves yields a deep-sea sound velocity profile estimate, similar to medical CT scans. This method offers a more direct local detection effect compared to previous deep-sea sound velocity profile inversion methods, thus providing better results for smaller areas. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems of high cost and difficult deployment of separate launch and reception moorings in existing technologies, and to provide a local, small-scale deep-sea sound velocity profile inversion method that utilizes reliable acoustic paths and is applicable to deep-sea seabed platforms. This method can obtain a deep-sea sound velocity profile covering a reliable acoustic path area using a single launch and deployment system with simple single-node platform systems.

[0005] This invention includes the following steps:

[0006] 1) For the mid-latitude deep-sea area of ​​the experiment, based on ocean model or measured sound speed profile data, analyze the variation law of deep-sea sound speed profile, extract the parameter variation range of deep-sea sound speed profile, including isohypersonic layer thickness, isohypersonic layer sound speed and quadratic function coefficient of the strata change, and use the ray sound propagation model, based on the preset system platform working depth and sea depth of the test area, calculate the sea surface echo arrival pitch angle and arrival time of different deep-sea sound speed profiles under different parameters, and use it as a copy field for matching and estimating deep-sea sound speed profile;

[0007] 2) Conduct deep-sea sound speed profile inversion experiments in the test sea area. First, deploy a vertical receiving array carrying an active sound source on the seabed of the test sea area. Use the active sound source to generate sound signals and use the vertical receiving array to collect the sea surface scattered echo signals. Use the synchronous vertical array to obtain the measured data of the arrival pitch angle and arrival time of the sea surface scattered echo after beamforming. At the same time, collect the deep-sea sound speed profile of the test sea area during the experiment.

[0008] 3) The measured two-dimensional curves of arrival time and arrival pitch angle of the sea surface scattered echo are matched and compared with the simulated two-dimensional curves of arrival time and arrival pitch angle of the sea surface scattered echo under different deep-sea sound speed profiles. When the sum of the differences in arrival time at different angles reaches the minimum, the best match is achieved. The deep-sea sound speed profile parameters under the best match are calculated. The estimated deep-sea sound speed profile is calculated based on the parameters and compared with the measured deep-sea sound speed profile to analyze the error. This method uses an active sound source located on the seabed to obtain the sea surface scattered echo signal within the reliable sound path range. The array processing of the integrated passive vertical array obtains the arrival pitch angle and arrival time information of the sea surface scattered echo signal at different angles passing through the water body. Since this information is sensitive to the deep-sea sound speed profile within the reliable sound path range, the deep-sea sound speed profile is inverted using this information.

[0009] This invention includes an inversion method for estimating deep-sea sound velocity profiles by acquiring two-dimensional curves of arrival pitch angle and arrival time of sea surface scattered echoes using a deep-sea seabed transceiver platform; obtaining copy fields of these two-dimensional curves using marine environmental data and ray models for different deep-sea sound velocity profiles; and matching these two-dimensional curves to obtain deep-sea sound velocity profile estimates. Compared with existing methods, this invention has the following advantages:

[0010] 1) For deep-sea sound velocity profiles, especially active and passive detection systems located on the seabed, this invention can obtain the full-depth deep-sea sound velocity profile of the platform's working area without contact. This eliminates the need to deploy deep-sea marine environmental parameter observation moorings that cover the entire depth, which is beneficial for quickly obtaining the marine environmental parameters required for the detection process. For example, in the 4,000-meter deep sea, conventional full-depth marine environmental observation moorings require a 4,000-meter-long anchoring system, while this invention only requires a 200-300-meter-long seabed anchoring platform to achieve full-depth estimation.

[0011] 2) For deep-sea sound velocity profiles, compared with conventional deep-sea sound velocity profile inversion methods, this invention can achieve rapid inversion of deep-sea sound velocity profiles because this method utilizes the sea surface scattering echo time over a large angle range from small grazing angles to large grazing angles. Conventional inversion requires several hours of calculation time, while this invention only requires a few minutes of calculation time.

[0012] 3) For deep-sea sound velocity profiles, compared with conventional deep-sea sound velocity profile inversion methods, this invention does not require the deployment of large sound source moorings and receiving moorings. Therefore, the test cost is low and the test deployment difficulty is low, which is conducive to large-scale deployment in deep-sea areas. Taking a 4,000-meter deep sea area as an example, conventional inversion requires two 4,000-meter moorings carrying dozens of self-contained receiving systems to complete the process. This invention only requires one 200-300-meter mooring to carry one system platform to complete the process. Attached Figure Description

[0013] Figure 1 In this invention, an active and passive platform located on the seabed is used. The seabed platform transmits signals and receives the sea surface scattered echoes. The sea surface scattered echoes include scattered echoes at different grazing angles, which serve as information for the inversion of the sound velocity profile in this invention.

[0014] Figure 2 This is a schematic diagram of the core logic of the inversion method in this invention, which includes obtaining two-dimensional curves of the arrival pitch angle and arrival time of the sea surface scattered echo using experiments, obtaining two-dimensional curves of the arrival pitch angle and arrival time under different sound speed profiles using marine environmental data, and obtaining the deep-sea sound speed profile inversion estimate by using the best match between the two.

[0015] Figure 3 This is a schematic diagram of the deployment platform for the deep-sea sound velocity profile inversion sea test in this invention. It mainly includes an active and passive platform located near the seabed, a buoy system for providing buoyancy, a weight system for fixing the position, and a beacon system for positioning.

[0016] Figure 4This is a two-dimensional curve of echo delay and pitch angle calculated by the model based on the measured sound speed profile and experimental setup in this invention. This is a two-dimensional curve of the arrival pitch angle and arrival time of the sea surface scattered echo obtained by beamforming the signal beam received from the sea surface using a deep-sea platform. This is used as measured information to carry out inversion.

[0017] Figure 5 It is a two-dimensional cost function of the surface sound velocity and thickness inverted in this invention. It is the deep-sea sound velocity profile parameter under the condition of the best-matched two-dimensional curve of the arrival pitch angle and arrival time of the sea surface scattered echo, including the thickness and sound velocity of the surface isotropic layer.

[0018] Figure 6 These are the variation coefficients of the surface isotropic layer and the strata of the deep-sea sound velocity profile retrieved in this invention. They are the two-dimensional function coefficients of the cost function as a function of sound velocity under optimal surface sound velocity and thickness conditions, thereby obtaining the sound velocity profile of the strata.

[0019] Figure 7 The comparison between the deep-sea sound velocity profile inverted in this invention and the measured deep-sea sound velocity profile shows that the two are quite consistent.

[0020] Figure 8 This is a flowchart illustrating the method of the present invention. Detailed Implementation

[0021] The following embodiments will further illustrate the present invention with reference to the accompanying drawings.

[0022] This invention provides an active inversion method for typical deep-sea sound velocity profiles based on reliable acoustic paths. The basic principle of this method is as follows:

[0023] When the sound source is located on the seabed, it emits a sound signal upwards. After the signal is reflected from the sea surface, it closely follows the scattered signal. Using a vertical array, the arrival pitch angle of the scattered signal at different times can be obtained. Combining these two measurements yields a two-dimensional curve of the arrival pitch angle and arrival time of the scattered signal. This curve represents the time required for sound waves at different angles to travel through the entire deep sea along different sound paths. Figure 1 As shown, this represents sampling of deep-sea water from different angles, carrying information about the deep-sea water at different angles. The deep-sea sound velocity profile directly affects the propagation time through the water at different angles. Therefore, this information can be used to invert the deep-sea sound velocity profile, and this is achieved through the operation of active and passive platforms located on the seabed.

[0024] Based on the above principles, the core logic diagram of the technology for inverting deep-sea sound velocity profiles is as follows: Figure 2 As shown. Figure 8 This invention provides an active inversion method for typical deep-sea sound velocity profiles based on reliable acoustic paths, which is implemented according to the following steps:

[0025] Step 1: For the mid-latitude deep-sea area of ​​the experiment, based on ocean model or measured sound speed profile data, analyze the variation law of deep-sea sound speed profile, extract the parameter variation range of the parameterized expression of deep-sea sound speed profile, and use the Gaussian ray sound propagation model, based on the preset system platform working depth and sea depth of the test area, calculate the sea surface echo arrival pitch angle and arrival time of different deep-sea sound speed profiles under different parameters, and use it as a copy field for matching and estimating deep-sea sound speed profile;

[0026] Step Two: Conduct deep-sea sound velocity profile inversion experiments in the test area, such as... Figure 3 As shown, firstly, a vertical receiving array carrying an active sound source is deployed on the seabed in the test area. The active sound source generates an acoustic signal, and the vertical receiving array collects the sea surface scattered echo signal. Further, the synchronous vertical array, after beamforming, obtains measured data on the elevation angle and arrival time of the sea surface scattered echo, as shown in the figure. Figure 4 The two-dimensional curves of the sea surface scattering echo time and the angle of arrival are shown. The sound source uses a high-frequency signal from 1k to 10kHz, with more than 32 array elements. The signal form is a linear frequency modulated or single-frequency signal, and the array element spacing meets the frequency correspondence requirements. At the same time, the deep-sea sound velocity profile of the test sea area is collected during the test.

[0027] Step 3: Match and compare the measured two-dimensional curves of arrival time and arrival pitch angle of the sea surface scattered echo with the simulated two-dimensional curves of arrival time and arrival pitch angle of the sea surface scattered echo under different deep-sea sound speed profiles. Calculate the deep-sea sound speed profile parameters under the optimal match between the two, such as... Figure 5 The best-matched isohypersonic layer thickness and sound velocity were obtained. Figure 6 The obtained coefficients of the quadratic function of the stratification change are used to calculate the estimated deep-sea sound velocity profile, which is then compared with the measured deep-sea sound velocity profile to analyze the error. Figure 7 The comparison showed an error of 1.1 m / s, which is smaller than the estimation error of 3 m / s obtained by other methods.

[0028] Simulation experiment: with, for example Figure 3 The layout shown is simulated in a water depth of 3,000 meters. The simulation yielded the following results: Figure 4 The two-dimensional curves of sea surface scattered echo time and arrival pitch angle can be obtained by matching them, as shown below. Figure 5 and Figure 6 The results show that the optimal parameters and the simulation settings are completely consistent.

[0029] Actual test: such as Figure 7 As shown, in the actual inversion experiment at a water depth of 4,000 meters, the estimation error of the sound velocity at full depth was 1.1 m / s, which is less than the estimation error of 3 m / s by other methods.

[0030] This implementation obtains the sea surface scattered echo signal by actively transmitting acoustic signals from a deep-sea seabed platform. Beamforming is then performed on the sea surface scattered echo signal to obtain a two-dimensional curve of the arrival pitch angle and arrival time of the sea surface scattered echo signal. Since different deep-sea sound speed profiles have different two-dimensional curves of arrival pitch angle and arrival time of the sea surface scattered echo, the deep-sea sound speed profile can be rapidly inverted and estimated by matching these two-dimensional curves. It is not necessary to use a deep-sea mooring covering the entire water depth to obtain the full-depth sound speed profile measurement results. The deep-sea sound speed profile of this sea area can be obtained using a single transceiver platform.

[0031] This invention utilizes a single transceiver platform located on the seabed to obtain the deep-sea sound velocity profile of the area, eliminating the need for the traditional method of using a transmitting and receiving mooring to estimate the average deep-sea sound velocity profile between transmission and reception. The deployment equipment of this invention is relatively simple, and the deployment process is easy to operate.

[0032] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An active inversion method for typical deep-sea sound velocity profiles based on reliable acoustic paths, characterized in that... The method includes obtaining two-dimensional curves of the arrival pitch angle and arrival time of sea surface scattered echoes using a combination of active and passive deep-sea vertical array platforms; deriving two-dimensional curves of the arrival pitch angle and arrival time of sea surface scattered echoes under different deep-sea sound speed profiles through simulation calculations using ocean models or measured data; and estimating the deep-sea sound speed profile by matching the measured and simulated two-dimensional curves of the arrival pitch angle and arrival time of sea surface scattered echoes. The method specifically includes the following steps: 1) For the mid-latitude deep-sea area of ​​the experiment, based on ocean model or measured sound speed profile data, analyze the variation law of deep-sea sound speed profile, extract the parameter variation range of deep-sea sound speed profile, including isohypersonic layer thickness, isohypersonic layer sound speed and quadratic function coefficient of the strata change, and use the ray sound propagation model, based on the preset system platform working depth and sea depth of the test area, calculate the sea surface echo arrival pitch angle and arrival time of different deep-sea sound speed profiles under different parameters, and use it as a copy field for matching and estimating deep-sea sound speed profile; 2) Conduct deep-sea sound speed profile inversion experiments in the test sea area. First, deploy a vertical receiving array carrying an active sound source on the seabed of the test sea area. Use the active sound source to generate sound signals and use the vertical receiving array to collect the sea surface scattered echo signals. Use the synchronous vertical array to obtain the measured data of the arrival pitch angle and arrival time of the sea surface scattered echo after beamforming. At the same time, collect the deep-sea sound speed profile of the test sea area during the experiment. 3) The measured two-dimensional curves of arrival time and arrival pitch angle of the sea surface scattered echo are matched and compared with the simulated two-dimensional curves of arrival time and arrival pitch angle of the sea surface scattered echo under different deep-sea sound speed profiles. When the sum of the differences in arrival time at different angles reaches the minimum, the best match is achieved. The deep-sea sound speed profile parameters under the best match are calculated. The estimated deep-sea sound speed profile is calculated based on the parameters and compared with the measured deep-sea sound speed profile to analyze the error. This method uses an active sound source located on the seabed to obtain the sea surface scattered echo signal within the reliable sound path range. The array processing of the integrated passive vertical array obtains the arrival pitch angle and arrival time information of the sea surface scattered echo signal at different angles passing through the water body. Since this information is sensitive to the deep-sea sound speed profile within the reliable sound path range, the deep-sea sound speed profile is inverted using this information.

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