Acoustic scattering echo characteristic analysis and synthesis method and system of underwater target substructure

Abstract

The invention provides an acoustic scattering echo characteristic analysis and synthesis method for an underwater target substructure, and the method comprises the steps: S1, dividing an underwater model into substructures according to a preset rule, and forming substructure grid data in a surface element and point element format; s2, according to the grid data and the sound source orientation, calculating the target strength of an unshielded substructure through a plate element method; s3, calculating the shielded angle range of the substructure according to the grid data and the sound source orientation; s4, according to the shielded angle range of the substructure, the synthetic target strength of the substructure is calculated; and S5, target strength corresponding to the substructures is selected through a preset rule, the target strength is synthesized, and the overall target strength is formed. According to the method, a calculation method of the target strength of each substructure of a rigid target during synthesis is discussed through a synthesis theory and a plate element theory of the target strength, so that the contribution degree of each substructure of the target to the target strength of the whole structure is revealed.

Description

Technical Field

[0001] The present invention relates to the field of underwater acoustics, and in particular to a method and system for analyzing and synthesizing acoustic scattering echo characteristics of an underwater target substructure. Background Art

[0002] Underwater active sonar acoustic information countermeasures generally adopt the method of reducing the target strength and using acoustic decoys to counter. Among them, acoustic decoys are soft-kill equipment widely used in underwater acoustic countermeasure systems of various countries. They have been used in torpedo interference and deception, and mine sweeping. Acoustic decoys can be divided into two modes: active and passive. Passive acoustic decoys simulate or suppress the scattered sound field of active sonar signals by generating false echoes, strong clutter echoes, etc. through passive interference bodies or simulation bodies to destroy the detection and identification capabilities of active sonar. They have the advantages of fast response time, not easy to be exposed, light weight, low cost, and good maneuverability. Target strength describes the strength of the target's echo capability, so a reasonable prediction of target strength is the basis for accurate detection, positioning and identification of targets. The theoretical basis for the development of passive acoustic decoys is the prediction of the target's scattered sound field. However, the existing single "particle structure" cannot fully meet the simulation and regulation of passive acoustic decoys for the scattering of complex targets in the water, such as intensity, wide-angle spatial distribution characteristics, etc. Therefore, the topological combination of "particle structures" 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 of the interaction synthesis.

[0003] In recent years, the total noise level of large underwater targets has been continuously reduced, and active sonar has become an indispensable equipment for target acoustic detection and identification. Using cluster topology combined "particle structure" passive acoustic bait to simulate target echoes requires analysis of its target intensity characteristics. In fact, the intensity characteristics of underwater targets are very complex, because there are many substructures with huge differences in target intensity characteristics, which influence and interfere with each other and finally superimpose into the echo of large targets. Therefore, the target intensity shows ups and downs at different incident azimuths. Therefore, it is necessary to understand the target intensity characteristics of each substructure, analyze the contribution of the substructure to the target characteristics and the mutual influence between the structures, and realize the reasonable prediction of the intensity of large underwater targets.

[0004] The Chinese patent document with the publication number CN201310714052.0 discloses a method for rapidly estimating the scattered sound field of an underwater circular corner reflector, measuring the parameters of the circular corner reflector and the sound source parameters; discretizing the arc of the circular corner reflector to obtain N first-division surface elements; calculating the scattered sound field of a first-division surface element after multiple scattering: calculating the first scattered sound field of the first-division surface element at the receiving point, judging whether the first reflected sound beam intersects with other surfaces of the circular corner reflector, obtaining a second-division surface element, calculating the second scattered sound field of the second-division surface element at the receiving point, judging whether the second reflected sound beam intersects with other surfaces of the circular corner reflector, obtaining a third-division surface element, calculating the third scattered sound field of the third-division surface element at the receiving point, superimposing and summing the first scattered sound field, the second scattered sound field, and the third scattered sound field; superimposing the scattered sound fields of N first-division surface elements after multiple scattering. The invention provides a theoretical calculation method for the use of corner reflectors, reduces calculation time, and improves work efficiency. However, the invention discretizes the target into surface elements for scattering superposition, but does not use the point coordinates corresponding to the surface elements for research, and is unable to solve the problem of substructure target intensity synthesis.

[0005] We take a rigid reference target model as an example for research. Existing research mainly calculates the target strength characteristics of rigid targets and their substructures based on the plate element method. Then, based on the target strength synthesis theory, a target strength synthesis formula is given that ignores the phase difference, directly adds the algebraic addition, and considers the mutual coupling of each substructure, but the calculation method of the phase difference between each substructure is not given. Based on this, the present invention calculates the target strength of each substructure and the combined structure of a rigid target as it changes with the azimuth angle through the plate element method, proposes a method for calculating the phase difference between substructures, and gives a target strength synthesis method in combination with the shielding effect between each substructure. The research results can provide a reference for the research on underwater target detection. Summary of the invention

[0006] In view of the defects in the prior art, the object of the present invention is to provide a method and system for analyzing and synthesizing the acoustic scattering echo characteristics of an underwater target substructure.

[0007] According to the present invention, a method for analyzing and synthesizing acoustic scattering echo characteristics of an underwater target substructure includes:

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

[0009] Step S2: Calculate the target intensity of the unobstructed substructure by using the plate element method according to the grid data and the orientation of the sound source;

[0010] Step S3: Calculate the angle range of the substructure being blocked according to the grid data and the orientation of the sound source;

[0011] Step S4: Calculate the synthetic target intensity of the substructure according to the angle range where the substructure is blocked;

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

[0013] Preferably, the step S1 comprises:

[0014] Step S1.1: Divide the first substructure and the second substructure by plane segmentation; wherein each substructure includes n branch structures, and 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 element and point element.

[0016] Preferably, the step S2 comprises:

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

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

[0019] Step S2.3: judging whether there is any obstructed part of the substructure within the irradiation range through the grid data, if there is obstruction, proceeding to step S3, if not, proceeding to step S2.4;

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

[0021] Preferably, step S3 comprises:

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

[0023] The geometric center coordinates of the first substructure are A(x 1 ,y 1 ,z 1 ), the end vertex coordinates are B(x 3 ,y 3 ,z 3 ), the incident point coordinates of the sound source at 0 degrees are C(R,0,0), then the angle calculation formula of the first substructure being blocked is:

[0024]

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

[0026] The geometric center coordinates of the second substructure are D(x 2 ,y 2 ,z 2 ), the end vertex coordinates are E(x 4 ,y 4 ,z 4 ), the incident point coordinates of the sound source at 0 degrees are F(-R,0,0), then the angle at which the second substructure is blocked is:

[0027]

[0028] Preferably, step S4 comprises:

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

[0030] Step S4.2: According to the coordinates of the geometric center of the first substructure and the coordinates of the geometric center of the second substructure, the distance between the incident point and the geometric center of the first substructure is obtained as r 1 , the distance between the incident point and the second substructure is r 2 ; Then the distance difference between the incident point of the sound source and the first substructure and the second substructure is:

[0031] Δx=|r 1 -r 2 |;

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

[0033]

[0034] Among them, Δx is the path difference between the two waves; λ is the wavelength;

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

[0036]

[0037] The incident sound pressure P of the sound source i , P 1 is the echo sound pressure of the first substructure, P 2 is the echo sound pressure of the second substructure.

[0038] Preferably, step S5 comprises:

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

[0040] Step S5.2: According to the angle range of the changed incident azimuth angle, the target intensity corresponding to the substructure and the synthetic target intensity are selected to form the overall target intensity;

[0041] Specifically, the incident azimuth is When the incident azimuth is within the range, the second substructure target intensity is selected according to the calculation result of step S2; range, using the synthetic target intensity of step S4; the incident azimuth is When the target strength of the first substructure is within the range, the target strength of the first substructure is selected according to the calculation result of step S2.

[0042] According to the present invention, a system for analyzing and synthesizing acoustic scattering echo characteristics of an underwater target substructure is provided, comprising:

[0043] Module M1: Divide the underwater model into multiple substructures according to preset rules, and form substructure grid data in the format of surface element and point element;

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

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

[0046] Module M4: Calculate the synthetic target intensity of the substructure according to the angle range where the substructure is blocked;

[0047] Module M5: Select the corresponding substructure target strength and synthetic target strength through preset rules, and combine them to form the overall target strength.

[0048] Preferably, the module M1 comprises:

[0049] Module M1.1: Divide the first substructure into the second substructure by plane segmentation; wherein each substructure includes n branch structures, where n is an integer greater than 0;

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

[0051] The module M2 comprises:

[0052] Module M2.1: Determine the incident azimuth and incident point coordinates of the sound source, and read the grid data of the substructure;

[0053] Module M2.2: Determine whether the coordinates of the point element corresponding to the grid data are within the radiation range of the sound wave at the incident point. If not, remove the corresponding point element; if within the radiation range, trigger module M2.3;

[0054] Module M2.3: Determine whether there is any obstructed part of the substructure within the irradiation range through the grid data. If there is obstruction, module M3 is triggered; if there is no obstruction, module M2.4 is triggered;

[0055] Module M2.4: Calculate the scattered sound field superimposed by the unobstructed part according to the plate element method, and obtain the unobstructed first substructure target intensity and the unobstructed second substructure target intensity respectively.

[0056] Preferably, the module M3 includes:

[0057] Module M3.1: Calculate the angle range of the first substructure being blocked, which is

[0058] The geometric center coordinates of the first substructure are A(x 1 ,y 1 ,z 1 ), the end vertex coordinates are B(x 3 ,y 3 ,z 3 ), the incident point coordinates of the sound source at 0 degrees are C(R,0,0), then the angle calculation formula of the first substructure being blocked is:

[0059]

[0060] Module M3.2: Calculate the angle range of the second substructure being blocked, which is

[0061] The geometric center coordinates of the second substructure are D(x 2 ,y 2 ,z 2 ), the end vertex coordinates are E(x 4 ,y 4 ,z 4 ), the incident point coordinates of the sound source at 0 degrees are F(-R,0,0), then the angle at which the second substructure is blocked is:

[0062]

[0063] The module M4 comprises:

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

[0065] Module M4.2: According to the coordinates of the geometric center of the first substructure and the coordinates of the geometric center of the second substructure, the distance between the incident point and the geometric center of the first substructure is r 1 , the distance between the incident point and the second substructure is r 2 ; Then the distance difference between the incident point of the sound source and the first substructure and the second substructure is:

[0066] Δx=|r 1 -r 2 |;

[0067] Module M4.3: Calculating Phase Difference

[0068]

[0069] Among them, 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 , P 1 is the echo sound pressure of the first substructure, P 2 is the echo sound pressure of the second substructure.

[0073] Preferably, the module M5 comprises:

[0074] Module M5.1: The incident azimuth angle increases from 0 degrees to 180 degrees according to the preset angle;

[0075] Module M5.2: According to the angle range of the changing incident azimuth, select the target intensity corresponding to the substructure and the synthetic target intensity, and combine them to form the overall target intensity;

[0076] Specifically, the incident azimuth is When the range is , the second substructure target intensity is selected according to the calculation result of module M2; the incident azimuth is range, using the synthetic target intensity in module M4; the incident azimuth is When the range is within the range, the target strength of the first substructure is selected according to the calculation result of module M2.

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

[0078] 1. The present invention discusses the calculation method of the target strength of each substructure of a rigid target during synthesis through the target strength synthesis theory and plate element theory, thereby revealing the contribution of each substructure of the target to the target strength of the overall structure. On the one hand, the accuracy of the target strength calculation is improved, and on the other hand, the influence of each substructure on the target strength of the overall structure can be clearly analyzed;

[0079] 2. The present invention can more accurately simulate the scattering characteristics of large underwater targets by decomposing them into several substructures and calculating the target intensity of each substructure at different incident azimuths. 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, thereby improving the accuracy and practicality of the simulation.

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

[0081] 4. The present invention uses the plate element method to calculate the target strength of each substructure, converting the integral operation into an algebraic operation, thereby improving the 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0083] Figure 1 It is a flow chart of a method for analyzing and synthesizing acoustic scattering echo characteristics of an underwater target substructure of the present invention;

[0084] Figure 2 is a flow chart of the method of embodiment 1 of the present invention;

[0085] Figure 3 is a grid division diagram of the target described in Example 1 of the present invention;

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

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

[0088] Figure 6 is a graph showing the variation of target strength of each substructure of the target with azimuth angle according to Embodiment 2 of the present invention;

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

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

[0091] Fig. 9 This is a comparison diagram of the target strength of the modified substructure and the assembly described in Example 2 of the present invention. DETAILED DESCRIPTION

[0092] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0093] The present invention discusses the calculation method of the target strength of each substructure of a rigid target during synthesis through the target strength synthesis theory and plate element theory, thereby revealing the contribution of each substructure of the target to the target strength of the combined structure, and finally verifies the correctness of the method through simulation experiments. The present invention provides a theoretical basis for the practical engineering application of constructing passive acoustic bait. The research results are consistent with the physical structural characteristics of the target and have certain reference value for the scientific research and testing of underwater weapons.

[0094] According to the present invention, a method for analyzing and synthesizing acoustic scattering echo characteristics of an underwater target substructure includes: step S1: dividing an underwater model into multiple substructures according to a preset rule, and forming substructure grid data in the format of face elements and point elements; wherein the point elements and face elements include but are not limited to the coordinates of points and faces; step S2: calculating the target strength of unobstructed substructures by a plate element method according to the grid data and the orientation of the sound source; step S3: calculating the angle range of the substructure being obstructed according to the grid data and the orientation of the sound source; step S4: calculating the synthesized target strength of the substructure according to the angle range of the substructure being obstructed; step S5: selecting the corresponding substructure target strength and synthesized target strength according to preset rules, and combining them to form the overall target strength.

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

[0096] Specifically, the step S2 includes: step S2.1: determine the incident azimuth and the coordinates of the incident point of the sound source, and read the grid data of the substructure; step S2.2: determine whether the coordinates of the point element corresponding to the grid data are within the radiation range of the sound wave of the incident point. If not, remove the corresponding point element; if within the irradiation range, enter step S2.3; step S2.3: through the grid data, determine whether there is an obstructed part of the substructure within the irradiation range. If there is an obstruction, enter step S3; if not, enter step S2.4; step S2.4: calculate the scattered sound field superimposed by the unobstructed part according to the plate element method, and obtain the unobstructed first substructure target intensity and the second substructure target intensity respectively.

[0097] Specifically, the step S3 includes: step S3.1: calculating the angle range of the first substructure being blocked, which is

[0098] The geometric center coordinates of the first substructure are A(x 1 ,y 1 ,z 1 ), the end vertex coordinates are B(x 3 ,y 3 ,z 3 ), the incident point coordinates of the sound source at 0 degrees are C(R,0,0), then the angle calculation formula of the first substructure being blocked is:

[0099]

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

[0101] The geometric center coordinates of the second substructure are D(x 2 ,y 2 ,z 2 ), the end vertex coordinates are E(x 4 ,y 4 ,z 4 ), the incident point coordinates of the sound source at 0 degrees are 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 of the sound wave is θ, the coordinates of the incident point are (Rcos(θ), Rsin(θ), 0), and R is the distance between the incident point of the sound source and the target; step S4.2: according to the coordinates of the geometric center of the first substructure and the coordinates of the geometric center of the second substructure, the distance between the incident point and the geometric center position of the first substructure is obtained as r 1 , the distance between the incident point and the second substructure is r2 ; Then the distance difference between the incident point of the sound source and the first substructure and the second substructure is:

[0104] Δx=|r 1 -r 2 |;

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

[0106]

[0107] Among them, Δx is the path difference between the two waves; λ is the wavelength;

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

[0109]

[0110] The incident sound pressure P of the sound source i , P 1 is the echo sound pressure of the first substructure, P 2 is the echo sound pressure of the second substructure.

[0111] Specifically, the step S5 includes: step S5.1: starting from 0 degrees, the incident azimuth angle increases step by step according to a preset angle until it reaches 180 degrees; step S5.2: selecting the target intensity and the synthetic target intensity corresponding to the substructure according to the angle range of the changing incident azimuth angle, and combining them to form the overall target intensity; specifically, the incident azimuth angle is When the incident azimuth is within the range, the second substructure target intensity is selected according to the calculation result of step S2; range, using the synthetic target intensity of step S4; the incident azimuth is When the target strength of the first substructure is within the range, the target strength of the first substructure is selected according to the calculation result of step S2.

[0112] Example 1

[0113] In order to study the target strength synthesis method of each substructure of a rigid target in the above background technology, the present invention provides a substructure acoustic scattering echo characteristic analysis and synthesis method and system, aiming to calculate the target strength of each substructure of the target and the overall target strength changing with azimuth according to the plate element method, and to provide a target strength synthesis method by estimating the phase difference between substructures and combining the shielding effect between substructures. The method flow chart is shown in Figure 2 This method provides a phase difference estimation method between two substructures based on plate element, surface element and point coordinates, and at the same time determines the shielding range of each substructure from the incident azimuth of the sound wave, thereby removing some shielding effects and end surface 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.

[0114] In order to achieve the above object, the present invention adopts the following technical solutions:

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

[0116] To simulate the echo of a large target using the topological combination of passive acoustic decoy "particle structure", it is necessary to analyze the target strength of each substructure of the target and the target strength of the interaction synthesis. The present invention studies a certain rigid target, first introduces the model parameters, calculates and analyzes the change of the target strength of each substructure with the azimuth, and finally gives a synthesis method of the target strength.

[0117] (1) Underwater target model

[0118] At present, a rigid model proposed by scientific research institutions in Germany, the United States and other countries is a common model used internationally to study the characteristics of a large target. The main parameters of the model are: the hull is a cylindrical structure, 62m long and 7.5m in diameter, the bow is a hemisphere with a radius of 3.5m, the stern is a cone, the conning tower shell and the front half of the stern rudder end are semi-ellipsoids, and the back half are cones. The present invention uses the Benchmark submarine model in the COMSOL case library for research, assuming that the wavelength is λ, and the plate element grid is divided according to λ / 6. The results are as follows Figure 3 .

[0119] It can be seen from the figure that the rigid target model can be divided into four substructures: bow, hull, stern, and command platform enclosure. Assume that when the sound wave is incident from the stern, the azimuth angle is 0°, the transverse direction is 90°, and when the sound wave is incident from the bow, the azimuth angle is 180°, and so on. The substructure division and azimuth diagram are shown in Figure 4 . The target intensity of each substructure of the target is calculated using the plate element method. The main steps are: 1) Use plane segmentation in COMSOL software to extract the required substructure; 2) Divide the substructure into a triangular grid and export it into a plane element + point element format; 3) Import the grid data into the plate element algorithm for calculation, thereby obtaining the target intensity of each substructure with the azimuth change diagram, and analyze it. Specifically, step 1: input the point source position, determine the incident angle, and read the point coordinates corresponding to the substructure grid data; step 2: determine whether the plate corresponding to the grid data is within the irradiation range of the point source, and then remove the plates that are not within the irradiation range; step 3: among the irradiated plates, determine whether there are blocked plates. It is necessary to give their relative positions through the grid data corresponding to the plates to determine whether the plates are blocked; step 4: Calculate the scattered sound field superimposed by the unblocked plates according to the Kirchhoff approximation principle, so as to obtain the target intensity of the corresponding substructure.

[0120] (2) Target intensity synthesis method

[0121] Target intensity refers to the echo intensity reflected by the underwater target, which is 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:

[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 in intensity, the echoes will interfere and overlap, and only after complex changes can the actual echo of the target as a whole be formed. Assuming that the echo sound pressure of the substructure is P, the time delay and phase jump generated during the scattering process are the echo phase angle φ, and the changes in time delay and phase are related to the incident angle and the location of the structure, then the sound pressure P of the two substructure echo coupling is 12 for:

[0126]

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

[0128]

[0129] The synthetic target intensity is related to the phase difference, which changes continuously with the incident angle, resulting in a rich fluctuation of the overall target intensity. When the phase difference of the two substructure echoes is 0, it is coherent superposition in the same direction. At this time, the target intensity of each substructure can be algebraically added, and the formula is as follows:

[0130]

[0131] Among them, TS i is the target strength of the ith substructure, and n is the number of substructures.

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

[0133] It can be seen from the target intensity synthesis method that the echo phase difference between the two substructures is a necessary item for calculating the synthetic target intensity. In fact, for two waves with the same period, the calculation formula of the phase difference is as follows:

[0134]

[0135] Here, 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 element + point coordinates. The main steps are: 1) Sum all the point coordinates (x, y, z) of the substructure and take the average as the coordinates of the geometric center position of the substructure; 2) For any sound wave incident azimuth θ, calculate its incident point coordinates as (Rcos(θ), Rsin(θ), 0), where R is the distance from the sound source to the target. 3) Calculate the distance between the incident point and the geometric center position 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: Calculate the shielding range of each substructure; for substructures other than the command tower, when synthesizing the target intensity, it can be found that when the sound waves are incident from different azimuths, the contributions of the two substructures to the synthesized target intensity are different. This is because different substructures will block each other, so it is necessary to analyze the shielding range between each substructure and determine the selection of the main contributing substructure when synthesizing the target intensity. First, a schematic diagram of analyzing the shielding range between each substructure is given as follows Figure 5 As shown, the main steps are: Let the geometric center of substructure 1 be (x 1 ,y 1 ,z 21 ), substructure 2 is (x 2 ,y 2 ,z 2 ), when the sound source is incident from an azimuth angle of 0 degrees, it can only illuminate (x 2 ,y 2 ,z 2 ), substructure 1 is blocked by the end face between the two structures; as the azimuth angle changes to θ 1 , although the sound wave can pass through the end face, it cannot illuminate (x 1 ,y 1 ,z 1 ), when it changes to θ 2 When the sound wave hits (x 1 ,y 1 ,z 1 ), indicating that in 0-θ 2 In the range of θ, substructure 2 makes the main contribution to the synthetic target strength. 2 -θ 3 The sound wave can irradiate the two substructures at the same time, so the synthesis should be the target intensity synthesis method of the two substructures combined with the phase difference. 3 The sound wave just hits (x 2 ,y 2 ,z 2 ), then as the azimuth increases, the sound wave cannot reach (x2 ,y 2 ,z 2 ), indicating that 3 In the -180° range, substructure 1 makes the main contribution to the synthetic target strength. Let the geometric center of substructure 1 be A(x 1 ,y 1 ,z 1 ), the end vertex coordinates are B(x 3 ,y 3 ,z 3 ), the incident point coordinates of the sound source at 0 degrees are C(R,0,0), then the angle calculation formula for determining whether substructure 1 is blocked is:

[0138] The calculation formula for determining the occlusion range of substructure 2 is similar, except that the sound source position needs to be changed to (-R, 0, 0). In addition, 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 end face vertices between the two substructures, and the geometric center positions of the two substructures.

[0139] Step 4: Target intensity synthesis and contribution analysis: The substructure target intensity is synthesized below. The main steps are: 1) Based on steps 1 and 2, the target intensity and phase difference of each substructure at different incident azimuths are calculated; 2) Based on step 3, the point element information of the plate element method is used to calculate the occlusion range of each substructure; 3) In the 0-θ 2 When the target strength is in the range, substructure 2 is selected, and in θ 2 -θ 3 The range is calculated using the formula (4) in the target intensity synthesis method. 3 When the angle is within the range of -180°, substructure 1 is selected as the target strength; 4) the synthesized target strength is compared with the target strength of the combined structure, and the contribution of each substructure to the synthesized target strength is analyzed.

[0140] The theoretical basis and working principle of the present invention are:

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

[0142] (2) Plate element theory: This method uses physical acoustic methods to solve the scattered sound field of underwater targets. It uses a group 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 converts integral operations into algebraic operations, thereby improving the calculation speed.

[0143] Example 2

[0144] The present invention conducts theoretical research on the target strength of target substructures based on the underwater target strength synthesis theory and plate element theory. First, the target is decomposed into simple substructures, such as the bow, hull, stern, and command platform enclosure; then, each substructure is divided into triangular meshes, and the plate element method is used to calculate the target strength of each substructure and the combined structure; then, the substructure is approximated by the geometric center, and the phase difference and occlusion range between the 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 the present invention is 1.5kHz, and the distance between the transmitting and receiving points and the target center is 2000m, which meets the far field condition. The incident wave is approximately a plane wave. The target intensity of each substructure of the target is calculated with the plate element method. A target value is given every 1° to obtain the target intensity. Figure 6 , where the horizontal axis is the incident azimuth of the sound wave, and the vertical axis is the corresponding target intensity. The four figures are the target intensity of the bow, hull, stern, and command platform enclosure.

[0148] (2) Estimation of the phase difference between two substructures

[0149] The present invention takes the bow and the hull + command tower enclosure as examples for calculation, where the bow geometric center is (4.4079, 0.0036, 0.3416) and the hull + command tower enclosure is (26.7358, 0.0286, 1.3890). For an incident azimuth of 0°, the coordinates of the sound source position are (2000cos(0), 2000sin(0), 0), then the distances from the sound source to the two geometric centers are: r 2 =1.9733e3. The corresponding path difference is 0.0223e3, wavelength λ = 1500 / 1500 = 1m, and the phase difference is 140.2876 when substituted into formula (6). The phase difference at other angles can be calculated in the same way.

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

[0151] From the target model, it can be determined that the coordinate point of the end face between the bow and the hull + command tower enclosure is (7, 3.5, 0). Then, from formula (7), it can be obtained that the angle range of the bow being blocked is:

[0152]

[0153] In summary, when the angle is about 0-54 degrees, the hull + conning tower enclosure makes the main contribution to the strength of the combined target. Similarly, it can be calculated that the angle range of the hull + conning tower enclosure being blocked is 10.7138, and the range after taking the supplementary angle is about 170-180 degrees, that is, in this range, the bow of the boat makes the main contribution to the strength of the combined target.

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

[0155] In the range of 0-54 degrees, the target strength is selected as the hull + the command platform shell. In the range of 54-170 degrees, the target strength synthesis method is calculated using formula (4). In the range of 170-180 degrees, the target strength is selected as the bow. The synthetic target strength is obtained as follows: Figure 7 shown.

[0156] Depend on Figure 7 It is found that the synthetic target intensity trend is consistent with the trend of the hull + conning tower enclosure. This is because the scale of the hull + conning tower enclosure is much larger than the bow, so the main contribution of the echo comes from this substructure. When the azimuth angle is 0-10 degrees, the bow target intensity is larger due to the end surface effect. Subsequently, due to the phase difference and the change of the bow structure, the target intensity fluctuates dramatically with the azimuth angle; at 80-100 degrees, the sound wave is incident on the bow spherical shell surface. As the incident surface gradually increases, the target intensity slowly increases. At 100-180 degrees, the sound wave gradually moves to the bow apex, the scattering surface continues to decrease, and the target intensity decreases. Similarly, the target main body + conning tower shell has a higher target intensity at 0-10 and 170-180 degrees due to end mirror reflection. At 10-90 degrees, due to phase difference and structural changes, the target intensity fluctuates dramatically with the azimuth, and the target intensity reaches the maximum in the transverse position; then the target intensity gradually decreases, but because the conning tower shell and horizontal wings are concentrated in the front half of the hull, the overall target intensity is greater than that of the rear half of the hull.

[0157] The target strength of the synthetic structure and the target strength of the actual combined structure are as follows Figure 8As shown in the figure, the trend of the synthetic target intensity is consistent with that of the combined structure, and the amplitude range is close, which shows the applicability of this method. At 100-170 degrees, because a 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, but 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 synthetic target intensity is quite different from the combined structure intensity. This is because the sound wave just hits the geometric center of the bow at around 54 degrees. The change in target intensity may be caused by structural changes. At 170-180 degrees, the combined structure target intensity is relatively large. This is because at this time, the scattering part includes the conning tower shell in addition to the bow. When the target intensity is synthesized, due to the influence of the end face, the echo of the conning tower shell is annihilated in the mirror reflection and cannot be extracted during synthesis. For this reason, we ignore the phase difference and use formula (5) to directly superimpose the target intensity of the bow and the conning tower shell to obtain the target intensity result. Fig. 9 As shown in the results, it can be seen that the larger target strength is caused by the command platform enclosure, and the large difference at 170 degrees may also be caused by structural changes.

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

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

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

[0161] According to the present invention, a sound scattering echo characteristic analysis and synthesis system for underwater target substructures includes: module M1: dividing an underwater model into multiple substructures according to preset rules, and forming substructure grid data in face element and point element format; module M2: calculating the target strength of unobstructed substructures by plate element method according to grid data and the orientation of sound source; module M3: calculating the angle range of obstructed substructures according to grid data and the orientation of sound source; module M4: calculating the synthetic target strength of substructures according to the angle range of obstructed substructures; module M5: selecting corresponding substructure target strengths and synthetic target strengths according to preset rules, and combining them to form the overall target strength.

[0162] Specifically, the module M1 includes: module M1.1: using a plane segmentation method to divide the first substructure and the second substructure; wherein each substructure includes n branch structures, and n is an integer greater than 0; module M1.2: dividing the two substructures into triangular grids of a preset size, and forming substructure grid data in the format of face element and point element; the module M2 includes: module M2.1: determining the incident azimuth and the coordinates of the incident point of the sound source, and reading the grid data of the substructure; module M2.2: judging whether the point element coordinates corresponding to the grid data are within the radiation range of the sound wave of the incident point, if not within the irradiation range, removing the corresponding point element; if within the irradiation range, triggering module M2.3; module M2.3: judging whether there is an obstructed part of the substructure within the irradiation range through the grid data, if there is an obstruction, triggering module M3, and if not, triggering module M2.4; module M2.4: calculating the scattered sound field superimposed by the unobstructed part according to the plate element method, and obtaining the unobstructed target intensity of the first substructure and the target intensity of the second substructure respectively.

[0163] Specifically, the module M3 includes: Module M3.1: Calculate the angle range of the first substructure being blocked, which is

[0164] The geometric center coordinates of the first substructure are A(x 1 ,y 1 ,z 1 ), the end vertex coordinates are B(x 3 ,y 3 ,z 3 ), the incident point coordinates of the sound source at 0 degrees are C(R,0,0), then the angle calculation formula of the first substructure being blocked is:

[0165]

[0166]

[0167] Module M3.2: Calculate the angle range of the second substructure being blocked, which is

[0168] The geometric center coordinates of the second substructure are D(x 2 ,y 2 ,z 2 ), the end vertex coordinates are E(x 4 ,y 4 ,z 4 ), the incident point coordinates of the sound source at 0 degrees are F(-R,0,0), then the angle at which the second substructure is blocked is:

[0169]

[0170] The module M4 includes: module M4.1: the incident azimuth of the sound wave is θ, the coordinates of the incident point are (Rcos(θ), Rsin(θ), 0), and R is the distance between the incident point of the sound source and the target; module M4.2: according to the coordinates of the geometric center of the first substructure and the coordinates of the geometric center of the second substructure, the distance between the incident point and the geometric center of the first substructure is r 1 , the distance between the incident point and the second substructure is r 2 ; Then the distance difference between the incident point of the sound source and the first substructure and the second substructure is:

[0171] Δx=|r 1 -r 2 |;

[0172] Module M4.3: Calculating Phase Difference

[0173]

[0174] Among them, 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 , P 1 is the echo sound pressure of the first substructure, P 2 is the echo sound pressure of the second substructure.

[0178] Specifically, the module M5 includes: module M5.1: starting from 0 degrees, the incident azimuth angle increases step by step according to a preset angle until it reaches 180 degrees; module M5.2: selecting the target intensity and the synthetic target intensity corresponding to the substructure according to the angle range of the changing incident azimuth angle, and combining them to form the overall target intensity; specifically, the incident azimuth angle is When the range is , the second substructure target intensity is selected according to the calculation result of module M2; the incident azimuth is range, using the synthetic target intensity in module M4; the incident azimuth is When the range is within the range, the target strength of the first substructure is selected according to the calculation result of module M2.

[0179] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0180] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

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

2. The method for analyzing and synthesizing acoustic scattering echo characteristics of underwater target substructures according to claim 1, characterized in that: The step S1 comprises: Step S1.1: Divide the first substructure and the second substructure by plane segmentation; wherein each substructure includes n branch structures, and 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 element and point element.

3. The method for analyzing and synthesizing acoustic scattering echo characteristics of underwater target substructures according to claim 1, characterized in that: The step S2 comprises: Step S2.1: determine the incident azimuth 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 point element corresponding to the grid data are within the radiation range of the incident point sound wave. If not, remove the corresponding point element; if within the radiation range, proceed to step S2.3; Step S2.3: judging whether there is any obstructed part of the substructure within the irradiation range through the grid data, if there is obstruction, proceeding to step S3, if not, proceeding to step S2.4; Step S2.4: Calculate the scattered sound field superimposed by the unblocked part according to the plate element method, and obtain the unblocked first substructure target intensity and the unblocked second substructure target intensity respectively.

4. The method for analyzing and synthesizing acoustic scattering echo characteristics of underwater target substructures according to claim 1, characterized in that: The step S3 comprises: Step S3.1: Calculate the angle range of the first substructure being blocked, which is The geometric center coordinates of the first substructure are A(x1,y1,z1), the end vertex coordinates are B(x3,y3,z3), and the incident point coordinates of the sound source at 0 degrees are C(R,0,0). The calculation formula for the angle of the first substructure being blocked is: Step S3.2: Calculate the angle range of the second substructure being blocked, which is The geometric center coordinates of the second substructure are D(x2,y2,z2), the end vertex coordinates are E(x4,y4,z4), and the incident point coordinates of the sound source at 0 degrees are F(-R,0,0). Then the angle at which the second substructure is blocked is:

5. The method for analyzing and synthesizing acoustic scattering echo characteristics of underwater target substructures according to claim 4, characterized in that: The step S4 comprises: Step S4.1: The incident azimuth of the sound wave is θ, the coordinates of the incident point are (rcos(θ), Rsin(θ), 0), and R is the distance between the incident point of the sound source and the target; Step S4.2: According to the coordinates of the geometric center of the first substructure and the coordinates of the geometric center of the second substructure, the distance between the incident point and the geometric center of the first substructure is r1, and the distance between the incident point and the second substructure is r2; then the distance difference between the incident point of the sound source and the first substructure and the second substructure is: Δx = |r1-r2|; Step S4.3: Calculate the phase difference Among them, Δx is the path difference between the two waves; λ is the wavelength; Step S4.4: The synthetic target intensity is: 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.

6. The method for analyzing and synthesizing acoustic scattering echo characteristics of underwater target substructures according to claim 1, characterized in that: The step S5 comprises: Step S5.1: increasing the incident azimuth angle from 0 degrees to 180 degrees according to a preset angle; Step S5.2: According to the angle range of the changed incident azimuth angle, the target intensity corresponding to the substructure and the synthetic target intensity are selected to form the overall target intensity; Specifically, the incident azimuth is When the incident azimuth is within the range, the second substructure target intensity is selected according to the calculation result of step S2; range, using the synthetic target intensity of step S4; the incident azimuth is When the target strength of the first substructure is within the range, the target strength of the first substructure is selected according to the calculation result of step S2.

7. A system for analyzing and synthesizing acoustic scattering echo characteristics of underwater target substructures, characterized in that: include: Module M1: Divide the underwater model into multiple substructures according to preset rules, and form substructure grid data in the format of surface element and point element; Module M2: Calculate the target intensity of the unobstructed substructure using the plate element method based on the grid data and the orientation of the sound source; Module M3: Calculate the angular range of the substructure being blocked based on the grid data and the orientation of the sound source; Module M4: Calculate the synthetic target intensity of the substructure according to the angle range where the substructure is blocked; Module M5: Select the corresponding substructure target strength and synthetic target strength through preset rules, and combine them to form the overall target strength.

8. The acoustic scattering echo characteristic analysis and synthesis system of underwater target substructure according to claim 7, characterized in that: The module M1 comprises: Module M1.1: Divide the first substructure into the second substructure by plane segmentation; wherein each substructure includes n branch structures, where n is an integer greater than 0; Module M1.2: Divide the two substructures into triangular meshes of a preset size and form substructure mesh data in the format of face element and point element; The module M2 comprises: Module M2.1: Determine the incident azimuth and incident point coordinates of the sound source, and read the grid data of the substructure; Module M2.2: Determine whether the coordinates of the point element corresponding to the grid data are within the radiation range of the sound wave at the incident point. If not, remove the corresponding point element; if within the radiation range, trigger module M2.3; Module M2.3: Determine whether there is any obstructed part of the substructure within the irradiation range through the grid data. If there is obstruction, module M3 is triggered; if there is no obstruction, module M2.4 is triggered; Module M2.4: Calculate the scattered sound field superimposed by the unobstructed part according to the plate element method, and obtain the unobstructed first substructure target intensity and the unobstructed second substructure target intensity respectively.

9. The acoustic scattering echo characteristic analysis and synthesis system of underwater target substructure according to claim 7, characterized in that: The module M3 comprises: Module M3.1: Calculate the angle range of the first substructure being blocked, which is The geometric center coordinates of the first substructure are A(x1,y1,z1), the end vertex coordinates are B(x3,y3,z3), and the incident point coordinates of the sound source at 0 degrees are C(R,0,0). The calculation formula for the angle of the first substructure being blocked is: Module M3.2: Calculate the angle range of the second substructure being blocked, which is The geometric center coordinates of the second substructure are D(x2,y2,z2), the end vertex coordinates are E(x4,y4,z4), and the incident point coordinates of the sound source at 0 degrees are F(-R,0,0). Then the angle at which the second substructure is blocked is: The module M4 comprises: Module M4.1: The incident azimuth of the sound wave is θ, the coordinates of the incident point are (Rcos(θ), Rsin(θ), 0), and R is the distance between the incident point of the sound source and the target; Module M4.2: According to the coordinates of the geometric center of the first substructure and the coordinates of the geometric center of the second substructure, the distance between the incident point and the geometric center of the first substructure is r1, and the distance between the incident point and the second substructure is r2; then the distance difference between the incident point of the sound source and the first substructure and the second substructure is: Δx = |r1-r2|; Module M4.3: Calculating Phase Difference Among them, Δx is the path difference between the two waves; λ is the wavelength; Module M4.4: The synthetic target strength is: 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.

10. The acoustic scattering echo characteristic analysis and synthesis system of underwater target substructure according to claim 9, characterized in that: The module M5 comprises: Module M5.1: The incident azimuth angle increases from 0 degrees to 180 degrees according to the preset angle; Module M5.2: According to the angle range of the changing incident azimuth, select the target intensity corresponding to the substructure and the synthetic target intensity, and combine them to form the overall target intensity; Specifically, the incident azimuth is When the range is , the second substructure target intensity is selected according to the calculation result of module M2; the incident azimuth is range, using the synthetic target intensity in module M4; the incident azimuth is When the range is within the range, the target strength of the first substructure is selected according to the calculation result of module M2.

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