Analysis and Synthesis Methods of Acoustic Scattering Echo Characteristics of Underwater Target Substructures

Abstract

This invention provides a method for analyzing and synthesizing the acoustic scattering echo characteristics of underwater target substructures, comprising: Step S1: Dividing the underwater model into substructures according to preset rules, and forming substructure mesh data in surface element and point element format; Step S2: Calculating the target intensity of the unobstructed substructures using the plate element method based on the mesh data and the sound source orientation; Step S3: Calculating the angular range of obstruction of the substructures based on the mesh data and the sound source orientation; Step S4: Calculating the synthesized target intensity of the substructures based on the angular range of obstruction; Step S5: Selecting the target intensity and synthesized target intensity corresponding to the substructures according to preset rules to form the overall target intensity. This invention discusses the calculation method of the target intensity of each substructure of a rigid target during synthesis using the synthesis theory of target intensity and the plate element theory, thereby revealing the contribution of each substructure to the overall structural target intensity.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustics, and more specifically, to a method and system for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure. Background Technology

[0002] Underwater active sonar countermeasures generally employ methods such as reducing target intensity and using acoustic decoys. Acoustic decoys are widely used soft-kill equipment in underwater acoustic countermeasures systems worldwide, and have been applied in torpedo jamming and deception, and mine sweeping. Acoustic decoys can be divided into active and passive modes. Passive acoustic decoys generate false echoes or strong cluttered echoes using passive jamming or simulation objects to simulate or suppress the scattered sound field of active sonar signals, thereby disrupting the active sonar's detection and identification capabilities. They offer advantages such as fast reaction time, low visibility, lightweight design, low cost, and good mobility. Target intensity describes the strength of a target's echo capability; therefore, accurate prediction of target intensity is fundamental for accurate target detection, location, and identification. The theoretical basis for the development of passive acoustic decoys is the prediction of the target scattering sound field. However, the existing single "particle structure" cannot fully meet the simulation and control of the scattering of complex targets in water by passive acoustic decoys, such as intensity and wide-angle spatial distribution characteristics. Therefore, the topological combination of "particle structure" will be an effective way to simulate large targets. It is necessary to analyze the target intensity of each substructure of the target and the target intensity synthesized by interaction.

[0003] In recent years, the overall noise level of large underwater targets has been continuously decreasing, making active sonar an indispensable tool for target acoustic detection and identification. Simulating target echoes using passive acoustic decoys with clustered topology combinations of "particle structures" requires analysis of their target intensity characteristics. In fact, underwater target intensity characteristics are highly complex due to the existence of many substructures with significantly different intensity characteristics. These substructures influence and interfere with each other, ultimately superimposing to form the echo of a large target. Therefore, target intensity exhibits fluctuating characteristics under different incident azimuth angles. It is necessary to understand the target intensity characteristics of each substructure, analyze the contribution of each substructure to the target characteristics, and examine the interactions between different structures to achieve a reasonable prediction of the intensity of large underwater targets.

[0004] Chinese patent document CN201310714052.0 discloses a method for rapidly estimating the scattered sound field of an underwater circular corner reflector. The method involves measuring the parameters of the circular corner reflector and the sound source parameters; discretizing the circular arc of the corner reflector into N first-order subdivision elements; calculating the scattered sound field after multiple scattering of a single first-order subdivision element; calculating the first scattered sound field at the receiving point of the first-order subdivision element; determining whether the first reflected sound beam intersects with other surfaces of the circular corner reflector to obtain a second-order subdivision element; calculating the second scattered sound field at the receiving point of the second-order subdivision element; determining whether the second reflected sound beam intersects with other surfaces of the circular corner reflector to obtain a third-order subdivision element; calculating the third scattered sound field at the receiving point of the third-order subdivision element; summing the first, second, and third scattered sound fields; and finally summing the scattered sound fields after multiple scattering of the N first-order subdivision elements. This invention provides a theoretical calculation method for corner reflectors, reducing calculation time and improving work efficiency. However, this invention discretizes the target into surface elements for scattering and superposition, without using the point coordinates corresponding to the surface elements for research, thus failing to solve the problem of substructure target intensity synthesis.

[0005] Taking a rigid benchmark target model as an example, existing research mainly calculates the target intensity characteristics of the rigid target and its substructures based on the plate element method. Subsequently, based on the target intensity synthesis theory, formulas are given for direct algebraic addition ignoring phase differences and for considering the coupling effects between substructures. However, a method for calculating the phase difference between substructures is not provided. Therefore, this invention calculates the target intensity of a rigid target's substructures and combined structures as a function of azimuth using the plate element method, proposes a method for calculating the phase difference between substructures, and, considering the octagonal shielding effect between substructures, presents a method for synthesizing target intensity. The results of this research can provide a reference for underwater target detection research. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for analyzing and synthesizing the acoustic scattering echo characteristics of underwater target substructures.

[0007] The present invention provides a method for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure, comprising:

[0008] Step S1: Divide the underwater model into multiple substructures according to preset rules, and form substructure mesh data in surface element and point element format;

[0009] Step S2: Based on the grid data and the location of the sound source, calculate the target intensity of the unobstructed substructure using the plate element method;

[0010] Step S3: Calculate the angular range of the substructure being blocked based on the grid data and the location of the sound source;

[0011] Step S4: Calculate the composite target intensity of the substructure based on the occlusion angle range of the substructure;

[0012] Step S5: Select the corresponding substructure target strength and composite target strength according to preset rules, and combine them to form the overall target strength.

[0013] Preferably, step S1 includes:

[0014] Step S1.1: Divide the structure into a first substructure and a second substructure using a planar partitioning method; each substructure includes n branch structures, where n is an integer greater than 0;

[0015] Step S1.2: Divide the two substructures into triangular meshes of a preset size, and form substructure mesh data in the format of face elements and point elements.

[0016] Preferably, step S2 includes:

[0017] Step S2.1: Determine the incident azimuth angle and incident point coordinates of the sound source, and read the mesh data of the substructure;

[0018] Step S2.2: Determine whether the coordinates of the point element corresponding to the grid data are within the incident point acoustic radiation range. If they are not within the radiation range, remove the corresponding point element; if they are within the radiation range, proceed to step S2.3.

[0019] Step S2.3: Using grid data, determine whether there are any occluded parts in the substructure within the illumination range. If there is occlusion, proceed to step S3; otherwise, proceed to step S2.4.

[0020] Step S2.4: Calculate the scattered sound field superimposed on the unobstructed part according to the plate element method, and obtain the target intensity of the first substructure and the target intensity of the unobstructed substructure respectively.

[0021] Preferably, step S3 includes:

[0022] Step S3.1: Calculate the occlusion angle range of the first substructure, which is...

[0023] Let the geometric center coordinates of the first substructure be A(x1,y1,z1), the vertex coordinates of its end face be B(x3,y3,z3), and the incident point of the sound source at 0 degrees be C(R,0,0). Then, the formula for calculating the included angle by which the first substructure is blocked is:

[0024]

[0025] Step S3.2: Calculate the occlusion angle range of the second substructure, which is...

[0026] The geometric center coordinates of the second substructure are D(x2,y2,z2), the vertex coordinates of its end face are E(x4,y4,z4), and the incident point of the sound source at 0 degrees is F(-R,0,0). Then, the angle at which the second substructure is blocked is:

[0027]

[0028] Preferably, step S4 includes:

[0029] Step S4.1: The incident azimuth angle of the sound wave is θ, and the coordinates of the incident point are (Rcos(θ),Rsin(θ),0), where R is the distance between the incident point of the sound source and the target;

[0030] Step S4.2: Based on the geometric center coordinates of the first substructure and the second substructure, the distance from the incident point to the geometric center of the first substructure is r1, and the distance from the incident point to the second substructure is r2; therefore, the path difference between the incident point of the sound source and the first and second substructures is:

[0031] Δx = |r1 - r2|;

[0032] Step S4.3: Calculate the phase difference

[0033]

[0034] Where Δx is the path difference between the two waves; λ is the wavelength;

[0035] Step S4.4: The synthesized target intensity is:

[0036]

[0037] The incident sound pressure P of the sound source i P1 is the echo sound pressure of the first substructure, and P2 is the echo sound pressure of the second substructure.

[0038] Preferably, step S5 includes:

[0039] Step S5.1: Increase the incident azimuth angle from 0 degrees to 180 degrees by increments according to a preset angle.

[0040] Step S5.2: Based on the angular range of the changing incident azimuth, select the target intensity corresponding to the substructure and the composite target intensity, and combine them to form the overall target intensity;

[0041] Specifically, the incident azimuth angle is When the range is defined, the target intensity of the second substructure is selected based on the calculation results of step S2; the incident azimuth angle is within... The range is determined by the synthetic target intensity obtained in step S4; the incident azimuth angle is within... When determining the range, the target strength of the first substructure is selected based on the calculation results of step S2.

[0042] A system for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure according to the present invention includes:

[0043] Module M1: Divides the underwater model into multiple substructures according to preset rules, and forms substructure mesh data in surface element and point element formats;

[0044] Module M2: Calculates the target intensity of the unobstructed substructure using the plate element method based on grid data and the location of the sound source;

[0045] Module M3: Calculates the angular range of the substructure being blocked based on the grid data and the location of the sound source;

[0046] Module M4: Calculates the composite target intensity of the substructure based on the occlusion angle range of the substructure;

[0047] Module M5: Selects the corresponding substructure target strength and composite target strength according to preset rules, and combines them to form the overall target strength.

[0048] Preferably, the module M1 includes:

[0049] Module M1.1: It uses a planar partitioning method to divide the structure into a first substructure and a second substructure; each substructure includes n branch structures, where n is an integer greater than 0.

[0050] Module M1.2: Divides the two substructures into triangular meshes of a preset size and forms substructure mesh data in face and point element formats;

[0051] The module M2 includes:

[0052] Module M2.1: Determines the incident azimuth angle and incident point coordinates of the sound source, and reads the mesh data of the substructure;

[0053] Module M2.2: Determines whether the coordinates of the point element corresponding to the grid data are within the incident point's acoustic radiation range. If not within the radiation range, the corresponding point element is removed; if within the radiation range, module M2.3 is triggered.

[0054] Module M2.3: Based on grid data, determine whether there are any obscured parts in the substructure within the illumination range. If obscuration exists, module M3 is triggered; otherwise, module M2.4 is triggered.

[0055] Module M2.4: Calculates the scattered sound field superimposed on the unobstructed part according to the plate element method, and obtains the target intensity of the first substructure and the target intensity of the unobstructed substructure respectively.

[0056] Preferably, the module M3 includes:

[0057] Module M3.1: Calculates the occlusion angle range of the first substructure.

[0058] Let the geometric center coordinates of the first substructure be A(x1,y1,z1), the vertex coordinates of its end face be B(x3,y3,z3), and the incident point of the sound source at 0 degrees be C(R,0,0). Then, the formula for calculating the included angle by which the first substructure is blocked is:

[0059]

[0060] Module M3.2: Calculates the occlusion angle range of the second substructure.

[0061] The geometric center coordinates of the second substructure are D(x2,y2,z2), the vertex coordinates of its end face are E(x4,y4,z4), and the incident point of the sound source at 0 degrees is F(-R,0,0). Then, the angle at which the second substructure is blocked is:

[0062]

[0063] The module M4 includes:

[0064] Module M4.1: The azimuth angle of the sound wave incident is θ, and the coordinates of the incident point are (Rcos(θ),Rsin(θ),0), where R is the distance between the sound source incident point and the target;

[0065] Module M4.2: Based on the geometric center coordinates of the first and second substructures, the distance from the incident point to the geometric center of the first substructure is r1, and the distance from the incident point to the second substructure is r2; therefore, the path difference between the incident point of the sound source and the first and second substructures is:

[0066] Δx = |r1 - r2|;

[0067] Module M4.3: Calculate phase difference

[0068]

[0069] Where Δx is the path difference between the two waves; λ is the wavelength;

[0070] Module M4.4: The synthetic target strength is:

[0071]

[0072] The incident sound pressure P of the sound source i P1 is the echo sound pressure of the first substructure, and P2 is the echo sound pressure of the second substructure.

[0073] Preferably, the module M5 includes:

[0074] Module M5.1: Sets the incident azimuth angle to increase gradually from 0 degrees according to preset angles until it reaches 180°;

[0075] Module M5.2: Based on the angular range of the changing incident azimuth, select the target intensity corresponding to the substructure and the composite target intensity, and combine them to form the overall target intensity;

[0076] Specifically, the incident azimuth angle is When the range is defined, the target intensity of the second substructure is selected based on the calculation results of module M2; the incident azimuth angle is within... The range is determined by the synthetic target intensity in module M4; the incident azimuth is within... When determining the range, the target strength of the first substructure is selected based on the calculation results of module M2.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] 1. This invention discusses the calculation method of the target strength of each substructure of a rigid target during the synthesis process through the synthesis theory of target strength and the plate element theory. This reveals the contribution of each substructure of the target to the overall structural target strength. On the one hand, it improves the accuracy of target strength calculation. On the other hand, it can clearly analyze the influence of each substructure on the overall structural target strength.

[0079] 2. This invention decomposes a large underwater target into several substructures and calculates the target intensity of each substructure under different incident azimuth angles, which can more accurately simulate the scattering characteristics of large underwater targets; it also takes into account the interaction between the substructures (such as phase difference and occlusion effect) and obtains the overall target intensity through a synthesis method, which improves the accuracy and practicality of the simulation.

[0080] 3. By accurately calculating the phase difference and occlusion range, this invention can more accurately assess the contribution of each substructure to the overall target intensity, thereby optimizing the target intensity synthesis process;

[0081] 4. This invention uses the plate element method to calculate the target intensity of each substructure, transforming integral operations into algebraic operations, thereby improving calculation speed and efficiency. The application of the plate element method also makes it possible to analyze the scattering characteristics of underwater targets with complex shapes and structures. Attached Figure Description

[0082] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0083] Figure 1 This is a flowchart of an acoustic scattering echo characteristic analysis and synthesis method for an underwater target substructure according to the present invention;

[0084] Figure 2 This is a flowchart of the method in Embodiment 1 of the present invention;

[0085] Figure 3 This is the mesh partitioning diagram of the target described in Embodiment 1 of the present invention;

[0086] Figure 4 This is a schematic diagram of the target substructure and azimuth angle described in Embodiment 1 of the present invention;

[0087] Figure 5 This is a schematic diagram of the occlusion range between the target substructures described in Embodiment 1 of the present invention;

[0088] Figure 6 This is a diagram showing the variation of the target intensity of each substructure as a function of azimuth angle in Embodiment 2 of the present invention.

[0089] Figure 7 This is a comparison diagram of the target strength of the substructure and the synthesis result described in Embodiment 2 of the present invention;

[0090] Figure 8 This is a comparison diagram of the target strength of the substructure and the assembly described in Embodiment 2 of the present invention;

[0091] Figure 9 This is a comparison diagram of the target strength of the modified substructure and the assembly as described in Embodiment 2 of the present invention. Detailed Implementation

[0092] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0093] This invention discusses the calculation method for the target strength of each substructure of a rigid target during synthesis, using the synthesis theory and plate element theory. This reveals the contribution of each substructure to the overall target strength. Finally, simulation experiments verify the correctness of the method. This invention provides a theoretical basis for the practical engineering application of passive acoustic decoys. The research results are consistent with the physical structural characteristics of the target and have certain reference value for the research and testing of underwater weapons.

[0094] According to the present invention, an acoustic scattering echo characteristic analysis and synthesis method for an underwater target substructure includes: Step S1: Dividing the underwater model into multiple substructures according to preset rules, and forming substructure mesh data in surface element and point element format; wherein, point elements and surface elements include, but are not limited to, the coordinates of points and surfaces; Step S2: Calculating the target intensity of the unobstructed substructure using the plate element method based on the mesh data and the orientation of the sound source; Step S3: Calculating the angular range of the obstructed substructure based on the mesh data and the orientation of the sound source; Step S4: Calculating the synthesized target intensity of the substructure based on the angular range of the obstructed substructure; Step S5: Selecting the corresponding substructure target intensity and synthesized target intensity according to preset rules, and combining them to form the overall target intensity.

[0095] Specifically, step S1 includes: step S1.1: dividing the first substructure and the second substructure using a planar segmentation method; wherein each substructure includes n branch structures, where n is an integer greater than 0; step S1.2: dividing the two substructures into triangular meshes of a preset size, and forming substructure mesh data in the format of face elements and point elements.

[0096] Specifically, step S2 includes: Step S2.1: Determine the incident azimuth angle and incident point coordinates of the sound source, and read the grid data of the substructure; Step S2.2: Determine whether the coordinates of the corresponding point element in the grid data are within the radiation range of the incident point sound wave. If they are not within the radiation range, remove the corresponding point element; if they are within the radiation range, proceed to step S2.3; Step S2.3: Determine whether there is an obstructed part in the substructure within the radiation range using the grid data. If there is obstruction, proceed to step S3; if there is no obstruction, proceed to step S2.4; Step S2.4: Calculate the scattered sound field superimposed on the unobstructed part according to the plate element method, and obtain the target intensity of the first substructure and the target intensity of the second substructure without obstruction.

[0097] Specifically, step S3 includes: Step S3.1: Calculate the occlusion angle range of the first substructure, as follows:

[0098] Let the geometric center coordinates of the first substructure be A(x1,y1,z1), the vertex coordinates of its end face be B(x3,y3,z3), and the incident point of the sound source at 0 degrees be C(R,0,0). Then, the formula for calculating the included angle by which the first substructure is blocked is:

[0099]

[0100] Step S3.2: Calculate the occlusion angle range of the second substructure, which is...

[0101] The geometric center coordinates of the second substructure are D(x2,y2,z2), the vertex coordinates of its end face are E(x4,y4,z4), and the incident point of the sound source at 0 degrees is F(-R,0,0). Then, the angle at which the second substructure is blocked is:

[0102]

[0103] Specifically, step S4 includes: Step S4.1: The incident azimuth angle of the sound wave is θ, and the coordinates of the incident point are (Rcos(θ),Rsin(θ),0), where R is the distance from the incident point of the sound source to the target; Step S4.2: Based on the geometric center coordinates of the first substructure and the second substructure, the distance from the incident point to the geometric center of the first substructure is r1, and the distance from the incident point to the second substructure is r2; then the path difference between the incident point of the sound source and the first and second substructures is:

[0104] Δx = |r1 - r2|;

[0105] Step S4.3: Calculate the phase difference

[0106]

[0107] Where Δx is the path difference between the two waves; λ is the wavelength;

[0108] Step S4.4: The synthesized target intensity is:

[0109]

[0110] The incident sound pressure P of the sound source i P1 is the echo sound pressure of the first substructure, and P2 is the echo sound pressure of the second substructure.

[0111] Specifically, step S5 includes: Step S5.1: Increasing the incident azimuth angle from 0 degrees to 180 degrees in preset increments; Step S5.2: Selecting the target intensity corresponding to the substructure and the composite target intensity based on the angle range of the changing incident azimuth angle, and combining them to form the overall target intensity; specifically, the incident azimuth angle is in... When the range is defined, the target intensity of the second substructure is selected based on the calculation results of step S2; the incident azimuth angle is within... The range is determined by the synthetic target intensity obtained in step S4; the incident azimuth angle is within... When determining the range, the target strength of the first substructure is selected based on the calculation results of step S2.

[0112] Example 1

[0113] To study the target intensity synthesis method of a rigid target's substructures in the aforementioned background technology, this invention provides a method and system for analyzing and synthesizing the acoustic scattering echo characteristics of substructures. The aim is to calculate the target intensity of each substructure and the overall target as a function of azimuth using the plate element method. By estimating the phase difference between substructures and considering the shading effect between them, a method for synthesizing target intensity is provided. The flowchart of the method is shown below. Figure 2 This method provides a phase difference estimation method between two substructures based on the coordinates of plate elements, surface elements, and points. At the same time, it determines the occlusion range of each substructure from the incident azimuth of the sound wave, thereby removing some occlusion effects and end face effects. The target intensity synthesized by this method is closer to the target intensity of the combined structure and can more accurately reflect the change of target intensity with azimuth angle.

[0114] To achieve the above objectives, the present invention adopts the following technical solution:

[0115] Step 1: Target intensity synthesis method and scattering characteristics of each substructure of the target;

[0116] Simulating the echo of a large target using a passive acoustic decoy's "particle structure" topological combination requires analyzing the strength of each substructure and the combined strength of their interactions. This invention focuses on a rigid target, first introducing the model parameters, then calculating and analyzing the variation of the strength of each substructure with azimuth angle, and finally presenting a method for synthesizing the target strength.

[0117] (1) Underwater target model

[0118] Currently, a rigid model proposed by research institutions in Germany, the United States, and other countries is an internationally accepted model used to study the characteristics of large targets. The main parameters of the model are: a cylindrical hull, 62m long and 7.5m in diameter; a hemispherical bow with a radius of 3.5m; a conical stern; and a semi-ellipsoidal fore-and-aft section of the conning tower and stern wheel, with the aft section also being a conical shape. This invention uses the Benchmark submarine model from the COMSOL case library for research, setting the wavelength as λ, and dividing the plate element mesh according to λ / 6. The results are as follows. Figure 3 .

[0119] As shown in the diagram, the rigid target model can be divided into four substructures: bow, hull, stern, and conning tower. Assume that the azimuth angle is 0° when the sound wave is incident from the stern and 90° in the transverse direction, and 180° when incident from the bow, and so on. A schematic diagram of the substructure division and azimuth angles is shown below. Figure 4The following steps use the plate element method to calculate the target intensity of each substructure. The main steps are: 1) Extract the required substructures using planar segmentation in COMSOL software; 2) Divide the substructures into triangular meshes and export them as face elements + point elements; 3) Import the mesh data into the plate element algorithm for calculation, thereby obtaining the target intensity variation diagram of each substructure with azimuth angle, and analyzing it. Specifically, step 1: Input the point source location, determine the incident angle, and read the point coordinates corresponding to the substructure mesh data; step 2: Determine whether the plate corresponding to the mesh data is within the illumination range of the point source, and then remove the plates outside the illumination range; step 3: Among the illuminated plates, determine whether there are any obstructed plates. This requires providing their relative positions through the corresponding mesh data to determine if the plates are obstructed; step 4: Calculate the scattered sound field superimposed by the unobstructed plates according to the Kirchhoff approximation principle, thereby obtaining the target intensity of the corresponding substructure.

[0120] (2) Target Intensity Synthesis Method

[0121] Target intensity refers to the intensity of the echo reflected from an underwater target, defined as the reflected sound intensity I at a distance of 1m from the acoustic center of the target. r The incident sound intensity I from a distant sound source i The logarithm of the ratio, in dB, is given by the formula:

[0122] TS = 10lg|I r / I i | (1)

[0123] When the sound intensity I is proportional to the square of the sound pressure P, the target intensity can be written as:

[0124] TS=20lg|P r / P i | (2)

[0125] When multiple substructure targets are coupled, the echoes interfere and superimpose, undergoing complex changes before forming the actual echo of the entire target. Assuming the echo sound pressure of a substructure is P, and the time delay and phase jump during scattering are represented by the echo phase angle φ, where the time delay and phase changes are related to the incident angle and the structure's location, then the sound pressure P in the case of echo coupling between two substructures... 12 for:

[0126]

[0127] in, The corresponding synthetic target intensity is:

[0128]

[0129] The intensity of the synthesized target is related to the phase difference, which changes continuously with the incident angle, resulting in rich fluctuations in the overall target intensity. When the phase difference between the echoes of two substructures is 0, it is considered coherent superposition in the same direction. At this point, the intensity of each substructure target can be algebraically added, as shown in the following formula:

[0130]

[0131] Among them, TS i Let n be the target strength of the i-th substructure, and n be the number of substructures.

[0132] Step 2: Phase difference estimation method between two substructures;

[0133] As can be seen from the target intensity synthesis method, the echo phase difference between the two substructures is a necessary factor in calculating the synthesized target intensity. In fact, for two waves with the same period, the formula for calculating the phase difference is as follows:

[0134]

[0135] Where Δx is the path difference between the two waves.

[0136] Therefore, it is necessary to construct a method for calculating the phase difference between two substructures under the condition of known surface elements and point coordinates. The main steps are: 1) sum up the coordinates (x, y, z) of all points of the substructure and take the average as the geometric center position coordinates of the substructure; 2) for any incident azimuth angle θ of the sound wave, calculate the coordinates of its incident point as (Rcos(θ), Rsin(θ), 0), where R is the distance between the sound source and the target; 3) calculate the distance between the incident point and the geometric center positions of the two substructures respectively, and then take the difference as the path difference between the two waves; 4) substitute the path difference and wavelength into formula (6) to obtain the phase difference.

[0137] Step 3: Calculation of the obstruction range of each substructure; For substructures other than the command platform, during target intensity synthesis, it can be observed that the contributions of the two substructures to the synthesized target intensity differ when the sound wave is incident from different azimuth angles. This is because there is obstruction between different substructure panels. Therefore, it is necessary to analyze the obstruction range between each substructure to determine the selection of the main contributing substructure when synthesizing the target intensity. A schematic diagram of the analysis of the obstruction range between each substructure is given below. Figure 5 As shown, the main steps are: Let the geometric center of substructure 1 be (x1, y1, z). 21Substructure 2 is (x2, y2, z2). When the sound source is incident from an azimuth angle of 0 degrees, it can only illuminate (x2, y2, z2), while substructure 1 is blocked by the end face between the two structures. As the azimuth angle changes to θ1, the sound wave can cross the end face but cannot illuminate (x1, y1, z1). When it changes to θ2, the sound wave just illuminates (x1, y1, z1), indicating that in the range of 0-θ2, substructure 2 makes the main contribution to the synthesized target intensity. Subsequently, in the range of θ2-θ3, the sound wave can illuminate both substructures simultaneously, so the synthesis should be a target intensity synthesis method combining the phase difference of the two substructures. At θ3, the sound wave just illuminates (x2, y2, z2), and then as the azimuth angle increases, the sound wave cannot illuminate (x2, y2, z2), indicating that in the range of θ3-180°, substructure 1 makes the main contribution to the synthesized target intensity. Let the geometric center of substructure 1 be A(x1,y1,z1), the coordinates of the end face vertex be B(x3,y3,z3), and the coordinates of the incident point of the sound source at 0 degrees be C(R,0,0). Then the formula for calculating the included angle that determines whether substructure 1 is blocked is:

[0138] The formula for calculating the occlusion range of substructure 2 is similar, except that the sound source position needs to be changed to (-R, 0, 0). Furthermore, after calculating the included angle, the corresponding supplementary angle needs to be taken as the occlusion range of substructure 2. In summary, in actual implementation, the occlusion range of each substructure can be calculated by obtaining the sound source position, the coordinates of the vertices of the end faces between the two substructures, and the geometric center positions of the two substructures.

[0139] Step 4: Target intensity synthesis and contribution analysis; The target intensity of the substructure is synthesized below. The main steps are: 1) Calculate the target intensity and phase difference of each substructure under different incident azimuth angles based on steps 1 and 2; 2) Calculate the occlusion range of each substructure based on the point element information of the plate element method in step 3; 3) Select substructure 2 for target intensity in the range of 0-θ2, calculate it using formula (4) in the target intensity synthesis method in the range of θ2-θ3, and select substructure 1 for target intensity in the range of θ3-180°; 4) Compare the synthesized target intensity with the target intensity of the combined structure and analyze the contribution of each substructure to the synthesized target intensity.

[0140] The theoretical basis and working principle of this invention are as follows:

[0141] (1) Theory of target intensity synthesis: When calculating the target intensity, the echoes of each substructure have mutual influence. Following the idea of ​​the "bright spot model", each substructure is regarded as a bright spot, and the time delay and phase jump in the echo process are converted into the echo phase angle φ, which is related to the incident angle. Then, the target intensity value of the synthesized structure is calculated based on the echo amplitude and phase difference.

[0142] (2) Plate element theory: When applying physical acoustics to solve the underwater target scattered sound field, this method uses a set of planar plate elements to approximate the target surface, and superimposes the scattered sound fields of all plate elements to obtain an approximate value of the total scattered sound field. This method transforms integral operations into algebraic operations, which improves the calculation speed.

[0143] Example 2

[0144] This invention conducts a theoretical study on the target strength of substructures based on underwater target strength synthesis theory and plate element theory. First, the target is decomposed into simple substructures, such as the bow, hull, stern, and conning tower. Then, each substructure is divided into triangular meshes, and the target strength of each substructure and the combined structure is calculated using the plate element method. Next, the substructures are approximated using their geometric centers, and the phase difference and obstruction range between two substructures are analyzed. Finally, the overall target strength is obtained according to the target strength synthesis theory, thereby analyzing the contribution of each substructure to the target strength of the combined structure.

[0145] Example 2

[0146] (1) Calculation of scattering characteristics of each substructure of the target

[0147] The signal frequency used in this invention is 1.5kHz, and the distance between the transceiver point and the target center is 2000m, which meets the far-field condition, and the incident wave is approximately a plane wave. The plate element method is used to calculate the variation of the target intensity of each substructure with azimuth angle, providing a target value every 1°. The target intensity is shown in [the figure]. Figure 6 The graph shows the target intensity at the bow, hull, stern, and conning tower, with the horizontal axis representing the azimuth of the sound wave incident.

[0148] (2) Phase difference estimation between two substructures

[0149] This invention uses the bow and hull + conning tower as examples for calculations, where the geometric center of the bow is (4.4079, 0.0036, 0.3416), and the hull + conning tower is (26.7358, 0.0286, 1.3890). For an incident azimuth of 0°, the sound source coordinates are (2000cos(0), 2000sin(0), 0), then the distances from the sound source to the two geometric centers are respectively: r2 = 1.9733e3. The corresponding path difference is 0.0223e3, and the wavelength λ = 1500 / 1500 = 1m. Substituting into formula (6), the phase difference is 140.2876. Similarly, the phase difference at other angles can be calculated.

[0150] (3) Calculation of the shading range of each substructure

[0151] Based on the target model, the coordinates of the end face between the bow and the hull + conning tower are (7, 3.5, 0). Therefore, formula (7) yields the range of angles where the bow is obstructed:

[0152]

[0153] In summary, within the range of approximately 0-54 degrees, the hull and conning tower contribute significantly to the strength of the composite target. Similarly, the angle range where the hull and conning tower are obscured can be calculated to be 10.7138 degrees, which, after taking the supplementary angle, is approximately 170-180 degrees. This means that within this range, the bow contributes significantly to the strength of the composite target.

[0154] (4) Target intensity synthesis and contribution analysis

[0155] Within the 0-54 degree range, the target strength is selected from the hull plus the conning tower. Within the 54-170 degree range, it is calculated using formula (4) in the target strength synthesis method. Within the 170-180 degree range, the target strength is selected from the bow. Thus, the synthesized target strength is obtained as follows: Figure 7 As shown.

[0156] Depend on Figure 7 The trend of the composite target intensity is consistent with that of the hull + conning tower. This is because the hull + conning tower is much larger than the bow, so the main contribution of the echo comes from this substructure. The higher target intensity at the bow (0-10 degrees) is due to the end face effect. Subsequently, due to phase difference and changes in the bow structure, the target intensity fluctuates drastically with the azimuth. At 80-100 degrees, the sound wave is incident on the bow spherical shell surface; as the incident surface gradually increases, the target intensity increases slowly. At 100-180 degrees, the sound wave gradually moves towards the bow apex, the scattering surface continuously decreases, and the target intensity decreases. Similarly, the high target intensity of the main body and conning tower at 0-10 and 170-180 degrees is caused by mirror reflection from the end face. At 10-90 degrees, due to phase difference and structural changes, the target intensity fluctuates drastically with the azimuth angle, reaching its maximum at the transverse position. Subsequently, the target intensity gradually decreases, but because the conning tower and horizontal wings are concentrated in the forward half of the hull, the overall target intensity is greater than that in the aft half of the hull.

[0157] The target strength of the synthesized structure and the target strength of the actual combined structure are as follows: Figure 8As shown in the figure, the trend of the synthesized target intensity is consistent with that of the combined structure, and the amplitude range is similar, indicating the applicability of this method. In the 100-170 degree range, because a single point element is used to replace the substructure and the interaction between multiple scattering points is ignored, there will be a certain deviation when calculating the phase difference. However, except for a few points, most of the errors are within the acceptable range. At some special angles such as 54 degrees and 170-180 degrees, the synthesized target intensity differs significantly from the combined structure intensity. This is because around 54 degrees is exactly where the sound wave just hits the geometric center of the bow. It is possible that the structural change causes a change in the target intensity. At 170-180 degrees, the combined structure target intensity is relatively larger. This is because at this time, the scattering part includes not only the bow but also the conning tower. When synthesizing the target intensity, due to the influence of the end face, the echo of the conning tower is buried in the mirror reflection and cannot be extracted during synthesis. Therefore, we ignore the phase difference and use formula (5) to directly superimpose the target intensity of the bow and the conning tower to calculate the target intensity. The result is shown in the figure. Figure 9 As shown in the results, the larger target strength is caused by the conning tower shell. The larger difference at 170 degrees is also likely due to structural changes.

[0158] Similarly, the target strength synthesis of other substructures can be calculated, but due to differences in structure scale and construction, the position of the geometric center of the substructure needs to be corrected.

[0159] For those skilled in the art, equivalent substitutions or modifications can be made to the technical solution and concept of the present invention, and all such modifications or substitutions should fall within the protection scope of the appended claims.

[0160] The present invention also provides an acoustic scattering echo characteristic analysis and synthesis system for an underwater target substructure. The acoustic scattering echo characteristic analysis and synthesis system for an underwater target substructure can be implemented by executing the process steps of the acoustic scattering echo characteristic analysis and synthesis method for an underwater target substructure. That is, those skilled in the art can understand the acoustic scattering echo characteristic analysis and synthesis method for an underwater target substructure as a preferred embodiment of the acoustic scattering echo characteristic analysis and synthesis system for an underwater target substructure.

[0161] According to the present invention, an underwater target substructure acoustic scattering echo characteristic analysis and synthesis system includes: module M1: dividing the underwater model into multiple substructures according to preset rules, and forming substructure mesh data in surface element and point element format; module M2: calculating the target intensity of the unobstructed substructure using the plate element method based on the mesh data and the orientation of the sound source; module M3: calculating the angular range of the obstructed substructure based on the mesh data and the orientation of the sound source; module M4: calculating the synthesized target intensity of the substructure based on the angular range of the obstructed substructure; and module M5: selecting the corresponding substructure target intensity and synthesized target intensity according to preset rules, and combining them to form the overall target intensity.

[0162] Specifically, module M1 includes: module M1.1: dividing the first substructure and the second substructure using a planar segmentation method; wherein each substructure includes n branch structures, where n is an integer greater than 0; module M1.2: dividing the two substructures into triangular meshes of a preset size, and forming substructure mesh data in surface element and point element format; module M2 includes: module M2.1: determining the incident azimuth angle and incident point coordinates of the sound source, and reading the mesh data of the substructure; module M2.2: determining whether the coordinates of the point elements corresponding to the mesh data are within the sound wave radiation range of the incident point. If they are not within the illumination range, the corresponding point elements are removed; if they are within the illumination range, module M2.3 is triggered; module M2.3: using the mesh data, determining whether there is an obstructed part in the substructure within the illumination range. If there is obstruction, module M3 is triggered; if there is no obstruction, module M2.4 is triggered; module M2.4: calculating the scattered sound field superimposed on the unobstructed part according to the plate element method, and obtaining the target intensity of the unobstructed first substructure and the target intensity of the second substructure respectively.

[0163] Specifically, module M3 includes: module M3.1: calculating the occlusion angle range of the first substructure, for...

[0164] Let the geometric center coordinates of the first substructure be A(x1,y1,z1), the vertex coordinates of its end face be B(x3,y3,z3), and the incident point of the sound source at 0 degrees be C(R,0,0). Then, the formula for calculating the included angle by which the first substructure is blocked is:

[0165]

[0166]

[0167] Module M3.2: Calculates the occlusion angle range of the second substructure.

[0168] The geometric center coordinates of the second substructure are D(x2,y2,z2), the vertex coordinates of its end face are E(x4,y4,z4), and the incident point of the sound source at 0 degrees is F(-R,0,0). Then, the angle at which the second substructure is blocked is:

[0169]

[0170] Module M4 includes: Module M4.1: The incident azimuth angle of the sound wave is θ, and the coordinates of the incident point are (Rcos(θ),Rsin(θ),0), where R is the distance from the incident point of the sound source to the target; Module M4.2: Based on the geometric center coordinates of the first substructure and the second substructure, the distance from the incident point to the geometric center of the first substructure is r1, and the distance from the incident point to the second substructure is r2; then the path difference between the incident point of the sound source and the first and second substructures is:

[0171] Δx = |r1 - r2|;

[0172] Module M4.3: Calculate phase difference

[0173]

[0174] Where Δx is the path difference between the two waves; λ is the wavelength;

[0175] Module M4.4: The synthetic target strength is:

[0176]

[0177] The incident sound pressure P of the sound source i P1 is the echo sound pressure of the first substructure, and P2 is the echo sound pressure of the second substructure.

[0178] Specifically, module M5 includes: module M5.1: increasing the incident azimuth angle from 0 degrees to 180 degrees in preset increments; module M5.2: selecting the target intensity corresponding to the substructure and the composite target intensity based on the angle range of the changing incident azimuth angle, and combining them to form the overall target intensity; specifically, the incident azimuth angle is in... When the range is defined, the target intensity of the second substructure is selected based on the calculation results of module M2; the incident azimuth angle is within... The range is determined by the synthetic target intensity in module M4; the incident azimuth is within... When determining the range, the target strength of the first substructure is selected based on the calculation results of module M2.

[0179] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0180] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure, characterized in that, include: Step S1: Divide the underwater model into multiple substructures according to preset rules, and form substructure mesh data in surface element and point element format; Step S2: Based on the grid data and the location of the sound source, calculate the target intensity of the unobstructed substructure using the plate element method; Step S3: Calculate the angular range of the substructure being blocked based on the grid data and the location of the sound source; Step S4: Calculate the composite target intensity of the substructure based on the occlusion angle range of the substructure; Step S5: Select the corresponding substructure target strength and composite target strength according to preset rules, and combine them to form the overall target strength.

2. The method for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure according to claim 1, characterized in that, Step S1 includes: Step S1.1: Divide the structure into a first substructure and a second substructure using a planar partitioning method; each substructure includes n branch structures, where n is an integer greater than 0; Step S1.2: Divide the two substructures into triangular meshes of a preset size, and form substructure mesh data in the format of face elements and point elements.

3. The method for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure according to claim 2, characterized in that, Step S2 includes: Step S2.1: Determine the incident azimuth angle and incident point coordinates of the sound source, and read the mesh data of the substructure; Step S2.2: Determine whether the coordinates of the point element corresponding to the grid data are within the incident point acoustic radiation range. If they are not within the radiation range, remove the corresponding point element; if they are within the radiation range, proceed to step S2.

3. Step S2.3: Using grid data, determine whether there are any occluded parts in the substructure within the illumination range. If there is occlusion, proceed to step S3; otherwise, proceed to step S2.

4. Step S2.4: Calculate the scattered sound field superimposed on the unobstructed part according to the plate element method, and obtain the target intensity of the first substructure and the target intensity of the unobstructed substructure respectively.

4. The method for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure according to claim 3, characterized in that, Step S3 includes: Step S3.1: Calculate the occlusion angle range of the first substructure, which is... ; The coordinates of the geometric center of the first substructure are: The coordinates of the end face vertex are The coordinates of the incident point of the sound source at 0 degrees are: The formula for calculating the included angle where the first substructure is occluded is: Step S3.2: Calculate the occlusion angle range of the second substructure, which is... ; The geometric center coordinates of the second substructure are D. The coordinates of the end face vertex are E The coordinates of the incident point of the sound source at 0 degrees are F. Then the included angle at which the second substructure is occluded is: 。 5. The method for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure according to claim 4, characterized in that, Step S4 includes: Step S4.1: The azimuth angle of the sound wave incident is The coordinates of the incident point are , This is the distance between the sound source incident point and the target; Step S4.2: Based on the coordinates of the geometric center of the first substructure and the geometric center of the second substructure, the distance from the incident point to the geometric center of the first substructure is obtained. The distance from the incident point to the second substructure is The distance between the sound source incident point and the first substructure and the second substructure is: ； Step S4.3: Calculate the phase difference : in, This represents the path difference between the two waves; Wavelength; Step S4.4: The synthesized target intensity is: Incident sound pressure of the sound source , The echo sound pressure of the first substructure, The echo sound pressure of the second substructure.

6. The method for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure according to claim 3 or 5, characterized in that, Step S5 includes: Step S5.1: Increase the incident azimuth angle from 0 degrees to 180 degrees by increments according to a preset angle. Step S5.2: Based on the angular range of the changing incident azimuth, select the target intensity corresponding to the substructure and the composite target intensity, and combine them to form the overall target intensity; Specifically, the incident azimuth angle is When the range is defined, the target intensity of the second substructure is selected based on the calculation results of step S2; the incident azimuth angle is within... The range is determined by the synthetic target intensity obtained in step S4; the incident azimuth angle is within... When determining the range, the target strength of the first substructure is selected based on the calculation results of step S2.

7. A system for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure, characterized in that, include: Module M1: Divides the underwater model into multiple substructures according to preset rules, and forms substructure mesh data in surface element and point element formats; Module M2: Calculates the target intensity of the unobstructed substructure using the plate element method based on grid data and the location of the sound source; Module M3: Calculates the angular range of the substructure being blocked based on the grid data and the location of the sound source; Module M4: Calculates the composite target intensity of the substructure based on the occlusion angle range of the substructure; Module M5: Selects the corresponding substructure target strength and composite target strength according to preset rules, and combines them to form the overall target strength.

8. The acoustic scattering echo characteristic analysis and synthesis system for underwater target substructures according to claim 7, characterized in that, The module M1 includes: Module M1.1: It uses a planar partitioning method to divide the structure into a first substructure and a second substructure; each substructure includes n branch structures, where n is an integer greater than 0. Module M1.2: Divides the two substructures into triangular meshes of a preset size and forms substructure mesh data in face and point element formats; The module M2 includes: Module M2.1: Determines the incident azimuth angle and incident point coordinates of the sound source, and reads the mesh data of the substructure; Module M2.2: Determines whether the coordinates of the point element corresponding to the grid data are within the incident point's acoustic radiation range. If not within the radiation range, the corresponding point element is removed; if within the radiation range, module M2.3 is triggered. Module M2.3: Based on grid data, determine whether there are any obscured parts in the substructure within the illumination range. If obscuration exists, module M3 is triggered; otherwise, module M2.4 is triggered. Module M2.4: Calculates the scattered sound field superimposed on the unobstructed part according to the plate element method, and obtains the target intensity of the first substructure and the target intensity of the unobstructed substructure respectively.

9. The acoustic scattering echo characteristic analysis and synthesis system for underwater target substructures according to claim 8, characterized in that, The module M3 includes: Module M3.1: Calculates the occlusion angle range of the first substructure. ; The coordinates of the geometric center of the first substructure are: The coordinates of the end face vertex are The coordinates of the incident point of the sound source at 0 degrees are: The formula for calculating the included angle where the first substructure is occluded is: Module M3.2: Calculates the occlusion angle range of the second substructure. ; The geometric center coordinates of the second substructure are D. The coordinates of the end face vertex are E The coordinates of the incident point of the sound source at 0 degrees are F. Then the included angle at which the second substructure is occluded is: The module M4 includes: Module M4.1: The azimuth angle of the sound wave incident is The coordinates of the incident point are , This is the distance between the sound source incident point and the target; Module M4.2: Based on the coordinates of the geometric center of the first substructure and the geometric center of the second substructure, the distance from the incident point to the geometric center of the first substructure is... The distance from the incident point to the second substructure is The distance between the sound source incident point and the first substructure and the second substructure is: ； Module M4.3: Calculate phase difference : in, This represents the path difference between the two waves; Wavelength; Module M4.4: The synthetic target strength is: Incident sound pressure of the sound source , The echo sound pressure of the first substructure, The echo sound pressure of the second substructure.

10. The acoustic scattering echo characteristic analysis and synthesis system for underwater target substructures according to claim 9, characterized in that, The module M5 includes: Module M5.1: Sets the incident azimuth angle to increase gradually from 0 degrees according to preset angles until it reaches 180°; Module M5.2: Based on the angular range of the changing incident azimuth, select the target intensity corresponding to the substructure and the composite target intensity, and combine them to form the overall target intensity; Specifically, the incident azimuth angle is When the range is defined, the target intensity of the second substructure is selected based on the calculation results of module M2; the incident azimuth angle is within... The range is determined by the synthetic target intensity in module M4; the incident azimuth is within... When determining the range, the target strength of the first substructure is selected based on the calculation results of module M2.

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