Submarine enclosure structure acoustic tomography image rapid generation method, electronic equipment and program product

Abstract

The invention discloses a submarine enclosure structure acoustic tomography image generation method, which comprises the following steps: preprocessing: establishing a geometric model and a reflection / transmission coefficient model of a submarine enclosure structure; calculating a scattering sound field of the submarine enclosure; and generating an acoustic tomography image of the submarine enclosure structure. The method comprises the following steps: establishing a three-dimensional model of the submarine enclosure structure, including a grid model of the enclosure structure, and establishing a geometric model and a reflection / transmission coefficient model of the enclosure structure; and calculating a scattering sound field of the enclosure structure by adopting a sound transmission iteration physical acoustic solving method based on multiple times of reflection / transmission. And obtaining an omnidirectional echo signal frequency-angle spectrum of the enclosure structure, obtaining a two-dimensional spatial spectrum of the enclosure structure, and generating a sound tomography image of the enclosure structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater acoustic engineering, and in particular relates to a method for quickly generating an acoustic tomography image of a shell structure, an electronic device, a storage medium and a program product. Background Art

[0002] The hull structure is one of the iconic structures of submarines. It is the core part of the command room of modern submarines to perform tasks such as navigation and observation. Unlike other pressure-resistant shells filled with air inside the submarine, the hull is a sound-permeable structure filled with water. When the active sonar acts on the hull, the sound waves can penetrate into the structure and undergo multiple reflections and transmissions. Accurately grasping the acoustic scattering characteristics of the hull structure is of great strategic significance for improving the detection and identification capabilities of active sonar systems for submarines. From the perspective of target identification, acoustic tomography images can provide more intuitive target information, including not only the distance and azimuth information of the detected target, but also the geometric scale, structural characteristics and material information of the target. However, there is currently little research on the fine features of acoustic tomography images caused by multiple reflections and transmissions of underwater transmission structures, and there is a lack of efficient methods for generating acoustic tomography images of hull structures, which cannot meet the anti-submarine needs of future underwater battlefields. Summary of the invention

[0003] One of the embodiments of the present disclosure is a method for quickly generating an acoustic tomography image of a shell structure based on sound-through iterative physical acoustics, the method comprising the following steps:

[0004] Step 1: preprocessing, establishing a geometric model and reflection / transmission coefficient model of the submarine hull structure;

[0005] Step 2, calculating the scattered sound field of the submarine hull;

[0006] Step three, generating an acoustic tomography image of the submarine hull structure.

[0007] The preprocessing process of step one includes: constructing a three-dimensional model of the submarine hull structure, including a grid model of the hull structure, and establishing a geometric model and a reflection / transmission coefficient model of the hull structure.

[0008] The second step is to calculate the scattered sound field of the enclosure structure by using a physical acoustic solution method based on multiple reflection / transmission sound transmission iterations.

[0009] The sound-transmitting iterative physical acoustic solution method includes: iteratively calculating the qth order outer and inner surface potential functions through the first order outer and inner surface potential functions of the enclosure structure, and calculating the scattering potential function at the field point.

[0010] The acoustic tomography image generation process of step three includes: obtaining a frequency-angle spectrum of an omnidirectional echo signal of the enclosure structure, obtaining a two-dimensional spatial spectrum of the enclosure structure, and generating the acoustic tomography image of the enclosure structure.

[0011] The disclosed embodiment provides a method for quickly generating an acoustic tomography image of an underwater hull structure, by establishing a geometric model and a reflection / transmission coefficient model, using an acoustic transmission iterative physical acoustic method to calculate the scattered sound field, and combining the acoustic tomography principle to generate an image. The method can effectively characterize the multiple reflection / transmission effects of sound waves inside the hull structure, and improve the detection and identification capabilities of submarines. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, in which:

[0013] Figure 1 A flow chart of a method for generating an acoustic tomography image of a shell structure according to one embodiment of the present disclosure.

[0014] Figure 2 Schematic diagram of a standard submarine model hull structure model according to one of the embodiments of the present disclosure.

[0015] Among them, 2-a is a schematic diagram of the three-dimensional model, and 2-b is a schematic diagram of the grid model.

[0016] Figure 3 Schematic diagram of a local reflection / transmission model of a shell structure according to one of the embodiments of the present disclosure.

[0017] Figure 4 An example diagram of the reflection / transmission coefficient of the enclosure structure according to one of the embodiments of the present disclosure.

[0018] Among them, 4-a is the reflection coefficient modulus, 4-b is the reflection coefficient phase angle, 4-c is the transmission coefficient modulus, and 4-d is the transmission coefficient phase angle.

[0019] Figure 5 Schematic diagram of sound scattering of a closed water-filled thin shell structure according to one embodiment of the present disclosure.

[0020] Figure 6 Schematic diagram of an acoustic tomography model of an underwater enclosure structure according to one embodiment of the present disclosure.

[0021] Figure 7 Schematic diagram of the time-angle spectrum of the scattered echo of a 1:20 scale model of the enclosure structure according to one of the embodiments of the present disclosure.

[0022] Among them, 7-a is the simulation result, and 7-b is the experimental result.

[0023] Figure 8 An example diagram of an acoustic tomography image of a shell structure according to one of the embodiments of the present disclosure. DETAILED DESCRIPTION

[0024] Underwater acoustic tomography images usually refer to images acquired in underwater environments using sonar technology. It is a technology that uses the characteristics of sound waves propagating underwater to detect and image underwater objects. The steps for acquiring this image generally include: using one or more sound sources (such as sonar transmitters) to emit sound waves underwater. When sound waves propagate in water and encounter objects of different densities or elasticity, they are reflected, refracted or scattered. An array composed of multiple hydrophones (underwater microphones) receives the reflected or scattered sound waves. By analyzing the time, intensity, phase and other information of the received sound waves, algorithms are used to reconstruct the image of the underwater object.

[0025] As for the acquisition of acoustic tomography images of underwater hull structures, existing solutions generally rely on the Circular Synthetic Aperture Sonar (CSAS) system for field test measurements. This system is a side-scan sonar system that uses synthetic aperture technology to improve the resolution of underwater imaging. It is usually installed on a mobile platform, such as a ship, submarine or remotely operated vehicle (ROV), and scans the underwater environment as the platform moves in a circular motion. Here, field test measurements usually refer to testing and measurement work performed in an actual natural environment or operating environment, as opposed to in-field tests under laboratory conditions. The purpose of field tests is to verify the performance of the system in an actual application environment, including its stability, reliability and accuracy. Although this solution can provide detailed acoustic tomography images, its high requirements for test sites, professional equipment, specific models to be tested, and experienced test personnel greatly increase the economic cost and extend the test cycle.

[0026] In addition, although the traditional energy superposition model introduces the equivalent transmission coefficient of the outer shell to take into account the scattering effect of the inner surface of the sound-transmitting structure and realizes the rapid generation of acoustic tomography images of the sound-transmitting structure, it ignores the limitation of phase information, resulting in the inability to accurately restore the coherent spot information of the image. Here, the sound-transmitting structure refers to a structure that has little effect on the propagation of sound waves and allows sound waves to pass through with almost no loss. The energy superposition model refers to a mathematical model used to simulate and calculate the effect of sound-transmitting structures (such as the outer shell of sonar equipment or other sound wave propagation media) on sound wave propagation in acoustic imaging. This model is mainly used to predict the energy distribution and phase change of sound waves when passing through sound-transmitting structures, thereby generating acoustic tomography images.

[0027] In view of the above problems existing in the existing solutions, constructing an efficient and accurate method for generating acoustic tomography images of underwater hull structures is of great significance for improving submarine acoustic stealth technology. Therefore, the present invention proposes a method for generating acoustic tomography images of underwater hull structures, which combines the sound transmission iterative physical acoustic method with the principle of acoustic tomography to accurately characterize the multiple reflection / transmission effects of incident sound waves inside the structure in the image domain.

[0028] According to one or more embodiments, a method for quickly generating acoustic tomography images of a shell structure based on sound-through iterative physical acoustics is generally divided into three parts:

[0029] The first part is the preprocessing process, which is to establish the geometric model of the enclosure structure and the reflection / transmission coefficient model;

[0030] The second part is to establish a sound transmission iterative physical acoustic method that takes into account multiple reflection / transmission effects, and use this method to calculate the scattered sound field of the enclosure;

[0031] The third part is to combine the acoustic tomography principle to generate the acoustic tomography image of the enclosure structure.

[0032] Combining the above schemes, a method for generating acoustic tomography images of enclosure structures based on sound-transmitting iterative physical acoustics can be constructed. The technical route of this method is as follows: Figure 1 shown.

[0033] The preprocessing process includes: constructing a three-dimensional model of the shell structure, dividing the shell structure grid model, and establishing a shell structure reflection / transmission coefficient model;

[0034] The sound-transmitting iterative physical acoustics method is a numerical iterative method used to solve acoustic problems. It realizes the separation of time and space variables by expanding the acoustic field into a Fourier series. The solution of this method has a clear physical meaning and is a combination of all harmonics. It is suitable for studying the propagation characteristics of nonlinear sound waves in liquids. Here, the solution process of the sound-transmitting iterative physical acoustics method includes: the first-order external and internal surface potential function of the shell structure, the iterative calculation of the q-order external and internal surface potential function, and the calculation of the scattering potential function at the field point;

[0035] The process of generating an acoustic tomography image includes: frequency-angle spectrum of omnidirectional echo signal of enclosure structure, two-dimensional spatial spectrum of enclosure structure, and generation of acoustic tomography image of enclosure structure.

[0036] In the first part, during the preprocessing process, a three-dimensional model of the shell structure is constructed using modeling software, and then the surface of the structure is meshed, wherein the mesh size is no larger than one sixth of the wavelength corresponding to the maximum calculation frequency, thereby realizing geometric modeling of the shell structure.

[0037] Figure 2 It is a three-dimensional model and mesh model of the standard submarine model hull structure. Figure 3 It is a local reflection / transmission model of the shell-shell structure. The external medium and internal medium of the shell are both fluids, with sound speed and density ρ0 and c0 respectively; the middle structure is the shell structure with a thickness of h. The reflection coefficient of the shell structure is

[0038]

[0039] and the transmission coefficient is

[0040]

[0041] in, and are the mechanical impedance of the structure and the acoustic impedance of the fluid, respectively.

[0042] This example calculates the reflection coefficient of a 3 mm thick steel plate. and transmission coefficient With the incident angle of the sound wave θ i The cloud diagram of the change of sound wave frequency f is as follows Figure 4 shown.

[0043] The second part, the sound-transmitting iterative physical acoustics method, includes: Figure 5 Taking the horizontal cross section of the enclosure shown in the figure as an example, consider the closed water-filled thin shell sound scattering problem, where O is the origin of the coordinates, which is generally taken as the geometric center. Assume that the outer boundary of the shell is S + , the internal boundary is S - , S + The outer area is Ω + , S - The inner area is Ω - A sound source A is located in the outer area Ω + The sound wave is emitted, and the field point B is located in the outer area Ω + Receive echoes, their position vectors are r A and r B . n is the surface S + The external normal vector of the surface S - The external normal vector of the shell is r, and m = -n. The position vector of any point on the shell surface is r s .

[0044] In acoustics, the Helmholtz integral formula is used to calculate the sound field generated by the sound source distribution. This formula shows that the sound pressure at a point is obtained by integrating the contributions of all sound source points to the normal derivative of the sound source density. According to the Helmholtz integral formula satisfied by the water-filled thin shell structure, the field point r B The potential function of the scattered sound field at is

[0045]

[0046] Among them, Q is the total scattering order, G(r B |r s ) is the free space Green’s function, φ +(q) (r s ) is the position vector r s The q-th order external surface potential function, φ -(q) (rs ) is the position vector r s The qth order internal surface potential function.

[0047] For the first-order external and internal surface potential function, the difference is

[0048]

[0049] in, and denote the reflection coefficient and transmission coefficient respectively, φ i (r s |r A ) is the incident wave potential function.

[0050] For the qth (q≥2) order, the difference between the external and internal surface potential functions is

[0051]

[0052] Among them, φ +(q-1) (r′ s ) is the position vector r s The (q-1)th order external surface potential function, φ -(q-1) (r′ s ) is the position vector r s The (q-1)th order internal surface potential function is at .

[0053] The third part is the acoustic tomography image model of the enclosure structure. Figure 6 The acoustic tomography problem of underwater shell structure shown in the figure is based on the center of the imaging area O. s Establish a Cartesian coordinate system xO for the origin s y, the distances from the source point and the field point to the target center are R i and R, the angles between the incident and outgoing directions of the sound wave and the x-axis are θ T and θ R The source point is the position coordinate of the transmitting transducer, and the field point is the position coordinate of the receiving transducer.

[0054] Calculation of the frequency-angle spectrum φ of the omnidirectional echo signal of the enclosure structure using the sound-transmitting iterative physical acoustic method s (k,θ T ,θ R ), according to the relation k x = k(cosθ T +cosθ R ) and k y = k(sinθ T +sinθ R ), the echo frequency-angle spectrum is mapped to the two-dimensional spatial spectrum plane, and we have

[0055] φ s(k x ,k y )=φ s (k,θ T ,θ R ), (6)

[0056] Where k is the wave number, k x and k y are the x- and y-components of wave number k respectively.

[0057] The theoretical basis of acoustic tomography is Fourier's central slice theorem, which is essentially to obtain the target image through the two-dimensional spatial spectrum φ s (k x ,k y ) and the target two-dimensional space image function v(x,y) are two-dimensional Fourier transform pairs to realize image simulation. s (k x ,k y ) performs a two-dimensional Fourier transform to obtain the two-dimensional spatial image function of the shell structure

[0058]

[0059] In order to further verify the effect of the embodiment of the present disclosure, Figure 2 The 1:20 scale model of the standard submarine model hull structure shown in the figure was used for 0-360 degree horizontal omnidirectional time domain echo simulation. A 0.2ms short pulse and a 60kHz-80kHz linear frequency modulation signal were used as the transmitting signal. The sound wave transmitting point and receiving point were 10.9m and 7.6m away from the model sound center, respectively. Figure 7 (a) and (b) respectively give the simulation and experimental results of the time-angle distribution of the received echo pulse sequences in each azimuth direction, where the horizontal axis represents the incident azimuth angle, the vertical axis represents the echo pulse time, and the color represents the echo amplitude. i =0° corresponds to the bow incident, θ i = ±90° corresponds to normal transverse incidence, θ i = ±180° corresponds to the stern incident. Figure 7 It can be seen that the echo structures of the experiment and the simulation are relatively consistent, and the high-order scattered echo highlights of the water-filled sound-permeable enclosure structure can be clearly observed in the echo, which shows that the patented method can accurately predict the distribution of multiple reflection / transmission echo highlights of the underwater enclosure structure, providing identifiable fine features for underwater submarine target identification.

[0060] Furthermore, using Figure 7 The echo time-angle spectrum of the 1:20 scale model of the quasi-submarine model hull structure shown in (a) is combined with the acoustic tomography principle to generate an acoustic tomography image of the hull structure, as shown in Figure 2. Figure 8 As shown. Figure 8It can be seen that the first-order scattering bright spots accurately restore the outer contour characteristics of the enclosure structure, and other high-order scattering features reflect the water-filled sound-permeable characteristics of the enclosure structure.

[0061] In summary, the beneficial effects of the present disclosure include: the method can be used to accurately and efficiently generate acoustic tomography images of underwater water-filled sound-permeable hull structures, accurately characterize the multiple reflections and transmissions of incident sound waves inside the hull structure, and provide data support for improving the detection and identification capabilities of active sonar systems for submarines.

[0062] It should be understood that in the embodiments of the present invention, the term "and / or" is only a description of the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0063] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0064] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0065] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for generating an acoustic tomography image of a submarine hull structure, characterized in that: The method comprises the following steps: Step 1: preprocessing, establishing a geometric model and reflection / transmission coefficient model of the submarine hull structure; Step 2, calculating the scattered sound field of the submarine hull; Step three, generating an acoustic tomography image of the submarine hull structure.

2. The method according to claim 1, characterized in that The preprocessing process of step one includes: constructing a three-dimensional model of the submarine hull structure, including a grid model of the hull structure, and establishing a geometric model and a reflection / transmission coefficient model of the hull structure.

3. The method according to claim 1, characterized in that The second step is to calculate the scattered sound field of the enclosure structure by using a physical acoustic solution method based on multiple reflection / transmission sound transmission iterations. The sound-transmitting iterative physical acoustic solution method includes: iteratively calculating the qth order outer and inner surface potential functions through the first order outer and inner surface potential functions of the enclosure structure, and calculating the scattering potential function at the field point.

4. The method according to claim 1, characterized in that: The acoustic tomography image generation process of step three includes: obtaining a frequency-angle spectrum of an omnidirectional echo signal of the enclosure structure, obtaining a two-dimensional spatial spectrum of the enclosure structure, and generating the acoustic tomography image of the enclosure structure.

5. The method according to claim 2, characterized in that: Assuming the speed of sound is ρ0, the density is c0, and the thickness of the shell structure is h, the reflection coefficient of the shell structure is The transmission coefficient is in, is the mechanical impedance of the enclosure structure, is the fluid acoustic impedance of the shell structure.

6. The method according to claim 3, characterized in that: The enclosure structure is a closed water-filled thin shell structure.

7. The method according to claim 6, characterized in that The scattering sound field potential function of the enclosure structure satisfies the Helmholtz integral formula.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: The processor runs the computer program to implement the method according to any one of claims 1 to 7.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

10. A computer program product, comprising a computer program, characterized in that The computer program is executed by a processor to implement the method according to any one of claims 1 to 7.

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