A method for simulating and optimizing the echo signal intensity of a moving ship

Abstract

The application discloses a kind of moving warship sound scattering echo signal intensity simulation optimization methods, steps are: according to the waterline of ship model, establish three-dimensional warship model below water surface and section triangular surface grid, combined with fluctuating sea surface to the amplitude and period of three degrees of freedom motion of warship roll, pitch, yaw, obtain three-dimensional warship model motion posture, establish warship "multi-path" sound scattering echo model, according to moving warship "multi-path" sound scattering echo signal model, the echo signal intensity of each path is superposed, the echo signal intensity of moving warship is simulated.The method of the application has the significant advantages of high speed and high accuracy in simulating the echo signal intensity of moving warship, while simplifying the simulation process, and can simulate the echo signal intensity of moving warship sound scattering.

Description

Technical Field

[0001] This invention belongs to the field of underwater target acoustic scattering technology. It relates to a method for simulating and optimizing the intensity of acoustic scattering echo signals from moving ships. Background Technology

[0002] In recent years, given the significant role of research on the combined scattering of moving and complex targets in target stealth technology, marine remote sensing, and radar detection, related issues have attracted widespread attention from scholars both domestically and internationally. Currently, methods for simulating the echo signal intensity of moving ships are all based on a static state in a free field, failing to consider the time-varying motion attitude of the ship with waves and the scattering problem from the sea surface, as well as the multiple scattering problem caused by the coupling between the moving ship and motion. Furthermore, the simulation speed and accuracy do not meet the requirements of realistic simulation. Summary of the Invention

[0003] The purpose of this invention is to address the problems and shortcomings of the existing technology and to provide a method for simulating and optimizing the intensity of acoustic scattering echo signals from moving ships.

[0004] This invention, from an engineering application perspective, considers the influence of sea surface scattering and changes in the ship's motion attitude. By using a method based on six-degree-of-freedom motion decomposition and synthesis, a "multi-path" acoustic scattering echo model for ships is established. In simulating the echo signal intensity of moving ships, it is faster than the slice theory, saves 9-10 hours compared to the potential flow theory, and has an average error of less than 2dB between the theoretically simulated amplitude and the measured results. At the same time, it simplifies the simulation process and enables accurate and rapid simulation of the echo signal intensity of moving ships.

[0005] To achieve the above objectives, the present invention employs the following technical solution.

[0006] A method for simulating and optimizing the intensity of acoustic scattering echo signals from moving ships includes the following steps:

[0007] S1: Based on the ship model's hull lines, use the 3D modeling software UG (Unigraphics) to create a 3D hull model below the waterline;

[0008] S2: The established 3D hull model is meshed into triangular face meshes in the underwater part using the mesh generation software COMSOL, and the topological information of the nodes and elements of the mesh is exported.

[0009] S3: Import the results of S2 into the simulation software MATLAB. Based on the method of six-degree-of-freedom motion decomposition and synthesis, input the empirical statistical values ​​of the amplitude and period of the three-degree-of-freedom motion of the ship's roll, pitch, and yaw on the undulating sea surface. Through the simulation software MATLAB, realize the coordinate transformation of each vertex of the three-dimensional hull model in continuous motion state, obtain the motion attitude of the three-dimensional hull model changing with time under different sea state parameters, and derive the nodal motion coordinates of each motion attitude.

[0010] S4: Based on the results of S3, establish a "multi-path" acoustic scattering echo model of a moving ship. Solve for the echo signal intensity of the moving ship using the plate element algorithm. Then, according to the "multi-path" acoustic scattering echo model of the moving ship, superimpose the echo signal intensity of each path to simulate the echo signal intensity of the moving ship.

[0011] S5: Compare the echo signal strength of the moving ship obtained from S4 simulation with the echo signal strength obtained from experimental data processing. If the results are consistent, then the echo signal strength of the moving ship is taken as the signal strength.

[0012] Further preferably, the size of each triangular face mesh in step S2 should satisfy R. min >D 2 The / λ condition ensures that the calculation point is in the far field, where R... min λ is the minimum distance that can be calculated from the radius vector of the scattering point, D is the maximum size of each plate, and λ is the wavelength of the incident wave.

[0013] Further optimization, the specific method for obtaining the motion attitude of the three-dimensional ship model under the action of waves using the six-degree-of-freedom motion decomposition and synthesis method described in step S3 is as follows: among the six degrees of freedom of the ship, the main functions are roll, pitch, yaw, and heave. Therefore, the motion of the three degrees of freedom of roll, pitch, and yaw is considered as the following simple harmonic motion:

[0014]

[0015] In the formula, A1, A2, and A3 are the rotation matrices caused by the three degrees of freedom rotation of the ship's hull: roll, pitch, and yaw. M i (i = 1, 2, 3) represents the amplitude, T i (i = 1, 2, 3) is a period and α i (i = 1, 2, 3) represents the phase. For continuous three-dimensional rotation of the hull, the rotation matrix at time t is expressed as:

[0016] Further optimization reveals that the basic theoretical basis of the plate meta-algorithm described in step S4 is the Kirchhoff formula, ignoring the time factor e. -jωtThe scattered wave potential functions for the combined transmit and receive setup and the separate transmit and receive setup are expressed as follows:

[0017]

[0018]

[0019] Equation (1) is a special case of equation (2). In the equation, S is the surface of the scattering body; r1 and r2 are the incident point and the scattering point radius vectors, respectively, and are r when they are the same; α1 and α2 are the angles between the surface outward normal direction and the incident point and the scattering point radius vectors, respectively, and are α when they are the same; V(α) is the surface reflection coefficient.

[0020] Further optimization, in step S4, the moving ship's "multipath" acoustic scattering echo model has the following echo signal strength: In the formula, p 0i (t)(i=1,2,4) represents the scattered acoustic field in the target body coordinate system; L 0i (t)(i=1,2,4) represents the path difference; k represents the wave number; ρ(t) represents the mirror reflection coefficient of the sea surface.

[0021] Compared with the prior art, the advantages and beneficial effects of this invention are as follows:

[0022] The present invention provides a method for simulating and optimizing the echo signal intensity of moving ships. Based on a six-degree-of-freedom dynamic model of a randomly moving ship target and a method of six-degree-of-freedom motion decomposition and synthesis, it establishes a "multi-path" acoustic scattering echo model of the moving ship, achieving accurate and rapid simulation. This patent surpasses the speed of slicing theory in simulating the echo signal intensity of moving ships, saves 9-10 hours compared to potential flow theory, and has an average error of less than 2dB between the theoretically simulated amplitude and the measured results. It also simplifies the simulation process, enabling accurate and rapid simulation of the echo signal intensity of moving ships. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process for simulating and optimizing the echo signal strength of moving ships;

[0024] Figure 2 This is a schematic diagram of six motion postures of a moving ship;

[0025] Figure 3 It is a "multipath" acoustic scattering echo model of moving ships;

[0026] Figure 4 It is a time-varying curve of the echo signal strength of a moving ship as a function of the horizontal azimuth angle;

[0027] Figure 5(a) is a time-varying curve of the echo signal intensity of the moving ship hull when the wave frequency is 0.8 Hz and the incident wave frequency is f = 140 kHz;

[0028] Figure 5 (b) is a comparison chart of the statistical patterns of echo signal intensity of moving ship hull when the wave frequency is 0.8Hz and the incident wave frequency is f=140kHz. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] like Figure 1 As shown, the present invention provides a method for simulating and optimizing the intensity of acoustic scattering echo signals from moving ships, comprising the following steps:

[0031] S1: Based on the hull lines of the moving ship model, use the 3D modeling software UG (Unigraphics) to create a 3D geometric model of the ship below the waterline. The ship is 3.7m long, 0.46m wide, and has a draft of 0.16m.

[0032] S2: The established 3D hull model is meshed into triangular face meshes in the underwater part using the meshing software COMSOL. To ensure high quality of the mesh size and to meet the far-field conditions, the maximum element size of the mesh is 0.025, and a total of 10349 triangular face meshes are created. The topological information of the nodes and elements of the mesh is then exported.

[0033] S3: Import the results of S2 into the simulation software MATLAB. Based on the six-degree-of-freedom motion decomposition and synthesis method, input the empirical statistical values ​​of the amplitude and period of the ship's roll, pitch, and yaw motion under undulating sea conditions (under sea state 2, roll: M1 = 3.5°, T1 = 8.6s, α1 = 0°; pitch: M2 = 0.31°, T2 = 4.7s, α2 = 0°; yaw: M3 = 0.35°, T3 = 10s, α3 = 0°). Through simulation in MATLAB, the coordinate transformation of each vertex of the 3D hull model under continuous motion is realized, obtaining the time-varying motion attitude of the 3D hull model under sea state 2 parameters, such as... Figure 2 As shown, derive the node motion coordinates for each motion posture;

[0034] S4: Based on the results of S3, establish a "multipath" acoustic scattering echo model for moving ships. Using the plate element method, solve for the echo signal intensity of the moving ship. Then, according to the "multipath" acoustic scattering echo model for moving ships, as follows... Figure 3The images shown are the direct wave echo signals. Echo signal of either the incident wave or the scattered wave after passing over the water surface And the echo signals after both the incident wave and the scattered wave have passed the water surface. The signal strengths of the echoes from each path are superimposed, considering the effects of motion: (L 0i (t)(i=1,2,4) are all set to 10000m; ρ(t) is set to 1) to simulate the echo signal strength of moving ships;

[0035] S5: Compare the echo signal strength of the moving ship obtained from S4 simulation with the echo signal strength obtained from experimental data processing, such as... Figure 4 The figure shows the time-varying curve of the echo signal strength of a moving ship as a function of the horizontal azimuth angle. It conforms to the general pattern of ship echo signal strength: transverse direction > stern direction > bow direction; at a wave frequency of 0.8 Hz and an incident sound wave frequency of 140 kHz, such as... Figure 5 As shown, based on the results obtained from the processing of experimental data and simulation results of the moving hull, the echo signal intensity of the moving hull under wave action conforms to the χ² value over time. 2 The statistical distribution patterns show that the overall trends of the two are basically consistent, and the values ​​are close, with an average error of less than 2dB, thus yielding the intensity of the echo signal from a moving ship.

Claims

1. A method for simulating and optimizing the strength of acoustic scattering echo signals from a moving ship, characterized in that, It comprises the following steps: S1: according to the lines of the ship model, using three-dimensional modeling software, to establish the three-dimensional ship model below the water surface; S2: the established three-dimensional ship model, using mesh division software will be divided into triangular surface mesh; S3: the triangular surface mesh is imported into the simulation software, according to the six degrees of freedom motion decomposition and synthesis method, input fluctuating sea surface to the ship roll, pitch, yaw three degrees of freedom motion amplitude and period of empirical statistical value, through the simulation software simulation, realize the coordinate transformation of each vertex of three-dimensional ship model in continuous motion state, get the motion posture of three-dimensional ship model under different sea state parameters with time variation; S4: according to the results of S3, the establishment of the motion of the ship "multi-path” acoustic scattering echo model, through the plate element algorithm, the solution of the ship's each path echo signal strength, then according to the motion of the ship "multi-path” acoustic scattering echo signal model, superposition of each path echo signal strength, the echo signal strength of the moving ship is simulated; S5: the echo signal strength of the moving ship simulated by S4 is compared with the echo signal strength obtained by experimental data processing, when the results are consistent, the echo signal strength of the moving ship is obtained.

2. The method of claim 1, wherein, The triangular surface mesh in step S2 has a size of each triangular surface mesh satisfying R min D 2 / λ, which ensures that the calculation field point is a far field, wherein R min is the minimum distance that can be calculated by the scattering point vector, D is the maximum size of each plate, and λ is the wavelength of the incident wave.

3. The method of claim 1, wherein, The specific method of the six degrees of freedom motion decomposition and synthesis method in step S3 to solve the motion posture of the three-dimensional ship model under the action of sea waves is that in the 6 degrees of freedom of the ship, the roll, pitch, yaw and heave play a major role, then the motion of the three degrees of freedom of roll, pitch and yaw is considered as the following simple harmonic motion: In the formula, A1, A2, A3 are respectively rotation matrixes caused by three degrees of freedom rotation of ship target roll, pitch and yaw; M i (i=1, 2, 3) are amplitudes, T i (i=1, 2, 3) are periods and α i (i=1, 2, 3) are phases, for continuous three-dimensional rotation of the ship, the rotation matrix at time t is expressed as 4. The method of claim 1, wherein, The plate element algorithm described in step S4 has the most basic theoretical basis of Kirchhoff formula, ignoring the time factor e -jωt The scattering wave potential functions in the case of transceiver combination and transceiver separation are represented as Wherein, formula (1) is a special case of formula (2); in the formula, S is the surface of the scatterer; r1 and r2 are the incident point and scattering point vector respectively, the same as r; alpha1 and alpha2 are the angles between the surface normal direction and the incident point and scattering point vector respectively, the same as alpha; V(alpha) is the surface reflection coefficient.

5. The method of claim 1, wherein, The model of the "multi-path" acoustic scattering echo of the moving ship in step S4 is respectively the direct wave echo signal The echo signal after one of the incident wave or the scattered wave passes through the water surface And the echo signal after both the incident wave and the scattered wave pass through the water surface The four kinds of echo signals, wherein, p 0i (t)(i=1, 2, 4) is the scattered acoustic field under the target body coordinate system; L 0i (t)(i=1, 2, 4) is the acoustic path difference; k is the acoustic wave number; and p(t) is the mirror reflection coefficient of the sea surface.

6. The method of claim 1, wherein, The moving ship echo signal strength in step S4: where p 0i (t)(i = 1, 2, 3, 4) is the scattering sound field in the target body coordinate system; L 0i (t)(i = 1, 2, 3, 4) is the sound path difference; k is the sound wave number; and p(t) is the mirror reflection coefficient of the sea surface.

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