CN114460644A - Method for distinguishing near-far field of seismic waves induced by navigation of underwater target - Google Patents

Abstract

The invention relates to a method for distinguishing near and far fields of seismic waves induced by navigation of an underwater target, which comprises the following steps: acquiring shallow sea seismic wave field original data; including sound pressure time domain waveform and sound pressure cloud chart; processing the sound pressure cloud picture into a sound pressure wave field snapshot set; processing the sound pressure time domain waveform into a sound pressure-distance relative change curve; performing low-precision dividing operation of the far and near fields of the seismic waves to obtain a low-precision first boundary point position and a low-precision second boundary point position; performing high-precision division operation on the near and far fields of the seismic waves to obtain a high-precision first boundary point position and a high-precision second boundary point position; and (5) carrying out boundary point checking operation to obtain a boundary point consistency evaluation result and a boundary point range. The method effectively discriminates the far field, the transition field and the near field in the seismic waves; the underwater navigation target positioning device is suitable for passively and remotely positioning an underwater navigation target; and further based on the method, a proper array arrangement topological structure of the underwater sensor can be obtained according to different measurement requirements.

Description

Method for Discriminating Far and Near Fields of Seismic Waves Induced by Navigation of Underwater Targets

technical field

The invention relates to the technical field of underwater target detection, in particular to a method for judging the far and near fields of seismic waves induced by the navigation of underwater targets.

Background technique

The use of seismic waves to detect underwater targets has considerable value, because the seismic waves are generated by the disturbance of the underwater targets when they are sailing; the very low frequency radiation noise field of the underwater targets will induce seabed seismic waves on the seabed near them, and the seabed seismic wave signals include geoacoustic signals. And the underwater acoustic signal, which is located in the area near the target, the so-called near field, is the source area of its energy, and then gradually transitions and propagates to the far field along the seawater-seabed interface and the seabed; this is an unavoidable wave propagation. Furthermore, the very low-frequency signal in the radiated noise generated by underwater targets during navigation has the characteristics of long propagation distance and weak attenuation, and is easy to be detected; therefore, as long as the sensor array is properly arranged, and the collected seismic wave signals With reasonable processing, the underwater target using the existing concealed navigation technology can be effectively detected, and the application prospect is very broad;

However, due to the complex composition of submarine seismic waves, including longitudinal waves, shear waves, surface waves, side waves and other wave components, the propagation paths and expansion modes of different wave components are also different, so the original signals collected by the receiving point are mixed and cannot be Direct use; especially the far field, transition field, and near field signals are mixed together, and they need to be screened before they can be further used;

The disadvantages of the prior art are:

1. The research on underwater acoustic signals is currently limited to the method of discriminating the far and near fields of the acoustic radiation and acoustic scattering signals of underwater targets, and is not suitable for the discrimination of the far and near fields of submarine seismic waves induced by the navigation of underwater targets;

2. There is no effective method for judging the far-field and near-field of seismic waves;

To sum up, the distinction between far field, transition field, and near field of seismic waves has become a very valuable technology that has not yet been realized.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, the present invention provides a method for judging the far and near fields of submarine seismic waves induced by the navigation of underwater targets. Based on this, according to different measurement requirements, a suitable deployment topology of the submarine seismic wave sensor array is obtained.

In order to solve the above-mentioned problems, the technical scheme provided by the present invention is:

The method for judging the far and near fields of seismic waves induced by the navigation of underwater targets includes the following steps:

S100. Collect the original data of the shallow sea seismic wave field; the original data of the shallow sea seismic wave field include the sound pressure time-domain waveform and the sound pressure cloud map taken at the interface between the seawater and the seabed; then process the sound pressure cloud map into a set of sound pressure wave field snapshots Then, the sound pressure time domain waveform is processed into a sound pressure-distance relative change curve; the sound pressure wave field snapshot set includes the sound pressure wave field snapshots arranged in increasing time order;

S200. According to the sound pressure wave field snapshot collection, perform a low-precision division operation of the far and near fields of the seismic wave, and obtain a low-precision first demarcation point position and a low-precision second demarcation point position;

S300. According to the sound pressure-distance relative change curve, perform a high-precision division operation of the far and near fields of the seismic wave, and obtain a high-precision first demarcation point position and a high-precision second demarcation point position;

S400. Perform a boundary point verification operation according to the low-precision first boundary point position, the low-precision second boundary point position, the high-precision first boundary point position, and the high-precision second boundary point position, The demarcation point consistency evaluation result and the demarcation point range are obtained; the demarcation point consistency evaluation result and the demarcation point range are the final results of the present invention.

Preferably, in S100, the sound pressure time-domain waveform is collected by a plurality of receiving points arranged on the central axis of the seabed surface in the built shallow seabed seismic wave model; the receiving points are arranged in a grid form, and are mutually equal distances.

Preferably, the sound pressure time-domain waveform is a time-domain waveform in a two-dimensional rectangular coordinate system, wherein: the origin of the sound pressure time-domain waveform is the sound pressure intensity received by the receiving point at time 0, and the horizontal axis is time, and the vertical axis is the sound pressure intensity.

Preferably, in S100, the sound pressure cloud map is airspace data under three-dimensional coordinates, wherein: the origin is manually preset, the position is where the projected distance of the geometric center of the underwater target on the seabed surface is two grids, and the horizontal axis is The abscissa of the sound pressure signal from the artificially preset origin, the vertical axis is the ordinate of the sound pressure signal from the origin, and the vertical axis represents the energy of the sound pressure signal.

Preferably, in S100, the processing of the sound pressure nephogram into a set of sound pressure wave field snapshots specifically includes the following steps:

S110. Intercept the sound pressure nephogram within an artificially preset time range at an artificially preset interception frequency, and obtain a snapshot of the sound pressure wave field for each interception;

S111. Arrange each of the sound pressure wavefield snapshots in an increasing order of time, and then pack them to obtain the sound pressure wavefield snapshot set.

Preferably, processing the sound pressure time-domain waveform into a sound pressure-distance relative change curve as described in S100 specifically includes the following steps:

S120. From all the collected sound pressure time-domain waveforms, select a manually preset number, and the waveforms fluctuate up and down in the fluctuation range with the peak as the core and on both sides of the peak after excitation for the excitation duration. the sound pressure time-domain waveform; the excitation duration is manually preset; the fluctuation range is manually preset;

S121. For each of the sound pressure time-domain waveforms selected from S120, extract sound pressure peaks one by one;

S122. Take the logarithm of each of the sound pressure peaks, and then arrange the corresponding receiving points in order to obtain the sound pressure-distance relative change curve.

Preferably, in S200, the low-precision division operation of the far and near fields of the seismic wave specifically includes the following steps:

S210. Perform corresponding calibration operations on each grid on each of the sound pressure wave field snapshots in the sound pressure wave field snapshot set according to the following standards:

If the number of grids occupied by the central energy ring in the area where the grid is located is the largest among all time points, and the outer waveform contains only one color, the grid is demarcated as the low-precision first dividing point;

If the outer waveform of the area where the grid is located is restored to a color, and the wave field appears as a regular circular ring, the grid is demarcated as the low-precision second dividing point;

S220. Count the number of grids continuously arranged between the origin under the three-dimensional coordinates of the sound pressure nephogram and each of the low-precision first demarcation points; then count each of the low-precision first demarcation points Multiply the number of grids between the origin of the coordinate system and the side length of the grid to obtain the position of the low-precision first dividing point; then perform the following operations according to the position of the low-precision first dividing point:

If the position of the low-precision first demarcation point does not straddle the middle of a grid, confirm that the position of the low-precision first demarcation point is correct, and then output the position of the low-precision first demarcation point;

If the position of the low-precision first dividing point straddles the middle of a grid, a circle is drawn with the position of the low-precision first dividing point as the center and the length of the grid side as the radius; The range covered by the circle is used as the position of the new low-precision first dividing point, and then the new low-precision first dividing point position is output;

S230. Count the number of grids between the origin of the coordinate system and each of the low-precision second dividing points; then calculate the number of grids between each of the second low-precision dividing points and the origin of the coordinate system with the grid Multiply the side lengths to obtain the position of the low-precision second dividing point; and then perform the following operations according to the position of the low-precision second dividing point:

If the position of the low-precision second demarcation point does not straddle the middle of a grid, confirm that the position of the low-precision second demarcation point is correct, and then output the position of the low-precision second demarcation point;

If the position of the low-precision second dividing point straddles the middle of a grid, draw a circle with the position of the low-precision second dividing point as the center and the length of the grid side as the radius; The range covered by the circle is used as the new low-precision second dividing point position, and then the new low-precision second dividing point position is output.

Preferably, in S300, the high-precision division operation of the far and near fields of the seismic wave specifically includes the following steps:

S310. Fit the sound pressure-distance relative change curve to obtain a fitting curve; then divide the sound pressure-distance relative change curve into different stages; the stages include a first stage, a second stage and a Phase III; where:

The first stage is the sound pressure-distance relative change curve covered by the range from the origin to the first turning point; the first turning point is starting from the origin and extending the sound pressure-distance relative change curve The first turning point encountered in the forward direction of ;

The second stage is the relative change curve of sound pressure-distance covered by the range from the first turning point to the second turning point; the second turning point is the relative change of sound pressure-distance along the line The second turning point encountered by the forward travel of the curve;

The third stage is the relative change curve of sound pressure-distance covered by the range from the second turning point to the third turning point; the third turning point is the relative change of sound pressure-distance along the line The third turning point encountered by the forward travel of the curve;

S320. According to the attenuation degree of the sound pressure value in each of the stages one by one, determine the expansion mode of the seismic wave in the stage; the expansion mode includes a partial spherical wave expansion mode and a partial cylindrical wave expansion mode;

Then, the corresponding stage is marked with far and near fields according to the expansion mode; wherein:

If the expansion mode is the deviatoric surface wave expansion mode, marking the corresponding stage as a near field;

If the expansion mode is the deviated cylindrical wave expansion mode, marking the corresponding stage as far field;

S330. According to the interference effect between the different fluctuation components corresponding to the waveform of the sound pressure-distance relative change curve in each of the stages, confirm the far and near fields for each of the stages; wherein:

If the degree of coincidence between the sound pressure-distance relative change curve and the fitting curve in this stage is not lower than the artificially preset minimum coincidence degree threshold, and the sound pressure-distance relative change in this stage is If the fluctuation degree of the curve is lower than the artificially preset lowest threshold of the fluctuation index, and is marked as a near field in S320, it is confirmed that the said stage is a near field;

If the coincidence degree of the relative change curve of sound pressure-distance and the fitting curve in this stage is not lower than the minimum coincidence degree threshold, and is marked as far field in S320, the stage is confirmed for the far field;

If the degree of fluctuation of the relative change curve of sound pressure-distance in the stage is lower than the lowest threshold of the fluctuation index, and the relative change curve of sound pressure-distance in the stage is the fitting curve The degree of coincidence is lower than the minimum threshold of the degree of coincidence, and the relative change curve of the sound pressure-distance of the stage fluctuates up and down around the fitting curve, then confirm that the stage is a transition zone;

S340. Obtain the high-precision first demarcation point position and the high-precision second demarcation point position according to the confirmed relationship between the stages; specifically:

In the range between the near field and the transition zone, the first turning point encountered from the near field is the position of the high-precision first demarcation point;

In the range between the transition zone and the far field, the second turning point encountered from the transition zone is the position of the high-precision second demarcation point;

Then pack all the high-precision first demarcation point positions, and pack all the high-precision second demarcation point positions, as the result output of this step;

Preferably, in S400, the obtaining of the demarcation point consistency evaluation result and the demarcation point range specifically includes the following steps:

Sa410. Compare the position of the high-precision first demarcation point with the position of the low-precision first demarcation point one by one, and perform the following operations according to the comparison result:

If the position of the high-precision first demarcation point is exactly the same as the position of the low-accuracy first demarcation point, or the position of the high-precision first demarcation point is covered by the circle used as the position of the low-accuracy first demarcation point Within the range of , then add the character string "the first demarcation point was obtained successfully" in the demarcation point consistency evaluation result; at the same time, assign the position of the high-precision first demarcation point to the first demarcation point; then execute Sa430;

If the position of the high-precision first demarcation point does not overlap with the position of the low-precision first demarcation point, add the character string "Failed to obtain the first demarcation point" in the demarcation point consistency evaluation result; then execute Sa430;

Sa420. Compare the position of the high-precision second demarcation point with the position of the low-precision second demarcation point one by one, and perform the following operations according to the comparison result:

If the position of the high-accuracy second demarcation point is exactly the same as the position of the low-accuracy second demarcation point, or the position of the high-accuracy second demarcation point is covered by the circle used as the position of the low-accuracy second demarcation point Within the range of , then add the character string "Second demarcation point is obtained successfully" in the demarcation point consistency evaluation result; at the same time, assign the position of the high-precision second demarcation point to the second demarcation point; then execute Sa430;

If the position of the high-precision second demarcation point does not overlap with the position of the low-precision second demarcation point, add the character string "Failed to obtain the second demarcation point" in the demarcation point consistency evaluation result; then execute Sa430;

Sa430. The demarcation point consistency evaluation result after strings are added by Sa410 and Sa420 is the demarcation point consistency evaluation result; meanwhile, the first demarcation point and the second demarcation point are packaged as the demarcation point point range.

Compared with the prior art, the present invention has the following advantages:

1. Since the present invention is based on the sound pressure-distance relative change curve and the sound pressure nephogram, the boundary points of the far field-transition area and the boundary points of the transition area-near field are divided into low-precision and high-precision at the same time, and then the comparative evaluation is carried out. Divide the results, so that the far field, transition field and near field in the seismic wave can be effectively distinguished;

2. Because the present invention can effectively discriminate the far field, transition field and near field in the submarine seismic wave induced by the navigation of the underwater target, it is very suitable for passive and long-distance detection of the underwater navigation target;

3. Since the present invention can effectively discriminate the far field, transition field and near field in the seismic wave, it can further be based on this, and according to different measurement requirements, a suitable array layout topology of underwater sensors can be obtained.

Description of drawings

1 is a schematic top view of a simulation model according to a specific embodiment of the present invention;

2 is a schematic front view of a simulation model of a specific embodiment of the present invention;

Fig. 3 is the step flow schematic diagram of the specific embodiment of the present invention;

Figures 4a to 4f are the sound pressure-distance relative curve curves of the seabed along the y-direction under different vibration source frequencies in a 20m×20m grid at a non-fixed frequency according to a specific embodiment of the present invention, wherein the corresponding frequency of Figure 4a is 5Hz, and Figure 4b is corresponding to the frequency Figure 4c corresponds to 20Hz, Figure 4d corresponds to 30Hz, Figure 4e corresponds to 40Hz, and Figure 4f corresponds to 50Hz;

Fig. 5a is a sound pressure-distance relative change curve when f=50Hz under a 5m×5m grid at a non-fixed frequency according to a specific embodiment of the present invention;

5b is a schematic diagram of the comparison of the relative change curves of sound pressure-distance when f=50Hz under a 20m×20m grid and a 5m×5m grid under a non-fixed frequency according to a specific embodiment of the present invention;

6a to 6c are schematic diagrams of snapshots of the sound pressure wave field when f=50Hz at a non-fixed frequency according to a specific embodiment of the present invention, wherein the corresponding time of FIG. 6a is 0.07s, the corresponding time of FIG. 6b is 0.20s, and the corresponding time of FIG. 6c is 1.10 s;

7a is a schematic diagram of a first demarcation point under a non-fixed frequency according to a specific embodiment of the present invention;

7b is a schematic diagram of a second demarcation point at a non-fixed frequency according to a specific embodiment of the present invention;

Figures 8a to 8e are the relative change curves of sound pressure-distance along the y-direction of the seabed under different vibration source frequencies under a 20m×20m grid at a fixed frequency according to a specific embodiment of the present invention, wherein the corresponding frequency of Figure 8a is 5.607 Hz, and Figure 8b corresponds to the frequency is 15.415Hz, the corresponding frequency in Figure 8c is 25.897Hz, the corresponding frequency in Figure 8d is 35.530Hz, and the corresponding frequency in Figure 8e is 45.851Hz;

9a is a schematic diagram of a first demarcation point under different fixed frequencies according to a specific embodiment of the present invention;

9b is a schematic diagram of a second demarcation point under different fixed frequencies according to a specific embodiment of the present invention;

10a is a schematic diagram of a first demarcation point at each fixed frequency according to a specific embodiment of the present invention;

FIG. 10b is a schematic diagram of a second demarcation point at each fixed frequency according to a specific embodiment of the present invention;

11 is a schematic diagram of a fitting curved surface of the transfer relationship under different vibration source frequencies considering the transfer relationship according to a specific embodiment of the present invention;

Fig. 12 is the sound pressure-distance relative change curve when f=50Hz under consideration of the transfer relationship according to the specific embodiment of the present invention;

FIG. 13 is a schematic diagram of excitation of underwater target surface sound source according to a specific embodiment of the present invention;

14 is a schematic diagram of a coordinate system of a receiving point on a seabed surface according to a specific embodiment of the present invention;

15 is a schematic diagram of a time-domain waveform of seabed surface sound pressure according to a specific embodiment of the present invention;

Figures 16a to 16f are the relative change curves of sound pressure-distance along the y-direction of the seabed under different vibration source frequencies under the sound source frequency according to a specific embodiment of the present invention, wherein the corresponding frequency of Figure 16a is 5Hz, the corresponding frequency of Figure 16b is 10Hz, and Figure 16c The corresponding frequency is 20Hz, the corresponding frequency in Figure 16d is 30Hz, the corresponding frequency in Figure 16e is 40Hz, and the corresponding frequency in Figure 16f is 50Hz;

Figures 17a to 17c are schematic diagrams of snapshots of the sound pressure wave field at f=30Hz at a sound source frequency according to a specific embodiment of the present invention, wherein the corresponding time of Figure 17a is 0.07s, the corresponding time of Figure 17b is 0.20s, and the corresponding time of Figure 17c is 1.10 s;

18a is a schematic diagram of a first demarcation point under different sound source frequencies according to a specific embodiment of the present invention;

18b is a schematic diagram of a second demarcation point under different sound source frequencies according to a specific embodiment of the present invention;

19 is a fitting surface under different sound source frequencies according to a specific embodiment of the present invention;

FIG. 20 is a sound pressure change curve when f=47 Hz under different sound source frequencies according to a specific embodiment of the present invention.

Detailed ways

Below in conjunction with specific embodiments, the present invention will be further illustrated, and it should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The modifications all fall within the scope defined by the appended claims of this application.

It should be noted in advance that since the vibration frequencies generated by different devices in the water are different, the influence of the frequency change of the vibration source needs to be considered; and because this technology is mainly aimed at very low frequency signals of 5Hz-50Hz, this specific embodiment The non-natural frequencies 5Hz, 10Hz, 20Hz, 30Hz, 40Hz, 50Hz are selected as the main vibration sources for simulation, and 5.607Hz, 15.415Hz, 25.897Hz, 35.530Hz, 45.851Hz at natural frequencies are also selected as the main vibration sources for simulation , and the case of using the least squares method to fit the waveform of the sound pressure under the ship at different frequencies under the consideration of the transfer relationship, and selecting the same 5Hz, 10Hz, 20Hz, 30Hz, 40Hz, 50Hz as the main vibration source and the sound source frequency The simulation situation under the influence of the far and near fields of the seismic wave describes the technical means and corresponding technical effects of the present invention in detail.

It should be noted in advance that although the specific embodiment takes a very low frequency signal as an example, the application of the technical solution of the present invention in other frequency domains also falls within the protection scope of the present invention.

It should be noted that the simulation model of this specific embodiment is set as shown in Figures 1-2, wherein the red dots in Figure 2 are receiving points arranged on the sea surface.

As shown in Figure 3, the method for judging the far and near fields of seismic waves induced by the navigation of underwater targets includes the following steps:

S100. Collect the original data of the shallow sea seismic wave field; the original data of the shallow sea seismic wave field includes the sound pressure time domain waveform and the sound pressure cloud map; then process the sound pressure cloud map into a set of sound pressure wave field snapshots.

It should be noted that when the underwater target sails in the shallow sea, shallow sea seismic waves will be induced; and these shallow sea seismic waves carry the position information of the underwater target; therefore, the first step is to collect the raw data of the shallow sea seismic wave field, and then preprocess it. , become the sound pressure time-domain waveform and sound pressure nephogram for use in subsequent steps.

In this specific embodiment, processing the sound pressure nephogram into a set of sound pressure wavefield snapshots specifically includes the following steps:

S110. Intercept the sound pressure nephogram within an artificially preset time range at an artificially preset interception frequency, and obtain a snapshot of the sound pressure wave field for each interception.

S111. Arrange each sound pressure wave field snapshot in an increasing order of time, and then pack them to obtain a set of sound pressure wave field snapshots.

Then, the sound pressure time-domain waveform is processed into a sound pressure-distance relative change curve; the sound pressure wavefield snapshot collection contains the sound pressure wavefield snapshots arranged in increasing time order.

It needs to be further explained that due to the different boundary values of the far and near fields under different vibration source frequencies, the boundary point between the near field and the transition zone, namely the first boundary point, is relatively concentrated and has a small variation range, which is easily affected by the grid accuracy; However, the boundary point between the transition zone and the far field, that is, the second boundary point, is relatively scattered and varies greatly, so the influence of grid accuracy can be ignored.

In this specific embodiment, the sound pressure time-domain waveform is collected by a plurality of receiving points arranged on the central axis of the seabed surface in the built shallow seabed seismic wave model, wherein the seabed model is a cube, the seabed surface is a square, and the symmetry axis is To make the square an axisymmetric line; the receiving points are arranged in a grid and are equidistant from each other.

It should be noted that the sound pressure time-domain waveform is a time-domain waveform in a two-dimensional rectangular coordinate system, wherein: the origin of the sound pressure time-domain waveform is the sound pressure intensity received by the receiving point at time 0, and the horizontal axis is time, The vertical axis is the sound pressure intensity.

It should be noted that the sound pressure cloud map is the airspace data under three-dimensional coordinates, in which: the origin is preset manually, and the position is the first grid projected from the right (left) end of the underwater target on the seabed surface. Set it on the right to select the right end, and if the receiving point is preset to the left, select the left end. If the endpoint projection is just on the grid boundary line, the intersection of the grid boundary line and the symmetry axis is taken as the origin; if the endpoint projection spans a grid, the intersection of the grid boundary line and the symmetry axis with the closest distance is selected As the origin, similarly, if the receiving point is preset to the right, select the right boundary line of the grid, and if the receiving point is preset to the left, select the left boundary line of the grid.

The horizontal axis is the abscissa of the sound pressure signal from the artificially preset origin, the vertical axis is the ordinate of the sound pressure signal from the origin, and the vertical axis represents the energy of the sound pressure signal.

In this specific embodiment, the sound pressure time-domain waveform is processed into a sound pressure-distance relative change curve, which specifically includes the following steps:

S120. From all the collected sound pressure time-domain waveforms, select the number of artificial presets, and after the waveform is excited for the excitation time, the sound pressure fluctuates up and down in the fluctuation range with the peak as the core and on both sides of the peak Time domain waveform; excitation duration is manually preset; fluctuation range is manually preset.

S121. For each sound pressure time-domain waveform selected from S120, extract the sound pressure peaks one by one.

S122. Take the logarithm of each sound pressure peak value, and then arrange the corresponding receiving points in order to obtain a sound pressure-distance relative change curve.

S200. According to the sound pressure wave field snapshot collection, perform a low-precision division operation of the far and near fields of the seismic wave, and obtain the low-precision first demarcation point position and the low-precision second demarcation point position.

In this specific embodiment, the low-precision division operation of the far and near fields of the seismic wave specifically includes the following steps:

S210. Perform corresponding calibration operations on each grid on each sound pressure wave field snapshot in the sound pressure wave field snapshot set one by one according to the following standards:

If the central energy ring of the area where the grid is located has the largest number of grids among all time points, and the outer waveform contains only one color, the grid is demarcated as the low-precision first demarcation point.

If the outer waveform of the area where the grid is located reverts to a color and the wavefield appears as a regular annular ring, the grid is marked as the low-precision second demarcation point.

S220. Count the number of consecutive grids between the origin under the three-dimensional coordinates of the sound pressure cloud map and each low-precision first dividing point; then calculate the distance between each low-precision first dividing point and the origin of the coordinate system The number of grids is multiplied by the grid side length to obtain the position of the low-precision first dividing point; then the following operations are performed according to the position of the low-precision first dividing point:

If the position of the low-precision first dividing point does not straddle the middle of a grid, confirm that the low-precision first dividing point is in the correct position, and then output the position of the low-precision first dividing point.

If the position of the low-precision first dividing point straddles the middle of a grid, draw a circle with the position of the low-precision first dividing point as the center and a grid side length as the radius; then use the range covered by the drawn circle as The new low-precision first demarcation point position, and then output the new low-precision first demarcation point position.

S230. Count the number of grids between the origin of the coordinate system and each low-precision second dividing point; then multiply the number of grids between each low-precision second dividing point and the origin of the coordinate system by the grid side length , to obtain the low-precision second demarcation point position; then perform the following operations according to the low-precision second demarcation point position:

If the position of the low-precision second demarcation point does not straddle the middle of a grid, confirm that the position of the low-precision second demarcation point is correct, and then output the position of the low-precision second demarcation point.

If the position of the low-precision second dividing point straddles the middle of a grid, draw a circle with the position of the low-precision second dividing point as the center and a grid side length as the radius; then use the range covered by the drawn circle as The new low-precision second demarcation point position, and then output the new low-precision second demarcation point position.

It should be noted that when the low-precision division operation of the far and near fields of seismic waves is performed, due to the complicated model operation, in order to improve the calculation efficiency, a 20m×20m grid is used; The model is reconstructed in the near-field area that is easily affected by the grid accuracy, the model area is reduced to 200m, and the grid size is reset to 5m×5m.

S300. According to the relative change curve of sound pressure-distance, perform high-precision division of the far and near fields of the seismic wave, and obtain a high-precision first demarcation point position and a high-precision second demarcation point position.

In this specific embodiment, the high-precision division operation of the far and near fields of the seismic wave specifically includes the following steps:

S310. Fit the sound pressure-distance relative change curve to obtain the fitting curve; then divide the sound pressure-distance relative change curve into different stages; the stages include the first stage, the second stage and the third stage; wherein:

The first stage is the relative change curve of sound pressure-distance covered by the range from the origin to the first turning point; The first turning point.

The second stage is the relative change curve of sound pressure-distance covered by the range from the first turning point to the second turning point; Two turning points.

The third stage is the sound pressure-distance relative change curve covered by the range from the second turning point to the end of the curve; the end is the last point encountered when traveling in the positive direction of the sound pressure-distance relative change curve.

It should be noted that the main basis for dividing the curve into different stages is the difference in the slope of the fitting curve or its tangent. If the fitting curve is exactly one straight line, its own slope is calculated. If the fitting curve is not a straight line, its tangent is taken. and calculate the corresponding slope. A turning point refers to the intersection of two fitted curves with different slopes.

It should be further explained that the fitting curve or its tangent slope in stage 1 is the largest; the fitting curve or its tangent slope in stage 2 is smaller than that in stage 1; the fitting curve or its tangent slope in stage 3 is the smallest.

S320. According to the attenuation degree of the sound pressure value in each stage, determine the expansion mode of the submarine seismic wave in different stages; the expansion mode includes the partial spherical wave expansion mode, the partial cylindrical wave expansion mode and the intermediate Spread patterns between waves;

It should be noted that the spherical wave expansion mode and the cylindrical wave expansion mode are in the prior art, which can be described in detail with reference to "The Principle of Underwater Acoustics" written by Ulrich, and will not be repeated in the present invention.

Then, the corresponding stages are marked in the far and near fields according to the expansion mode; where:

If the expansion mode is a deviatoric surface wave expansion mode, the corresponding stage is marked as the near field.

If the expansion mode is a partial cylindrical wave expansion mode, the corresponding stage is marked as far field.

It needs to be further explained that there is a transition area between the spherical wave expansion mode and the cylindrical wave expansion mode. Specifically: when the distance is doubled and the sound pressure is 3.0dB, it is exactly spherical wave, and when the distance is doubled, the sound pressure is 3.0dB. Doubled, when the sound pressure is 6.0dB, it is exactly the cylindrical wave; therefore, for the interval (3.0dB, 6.0dB), in this specific embodiment, the midpoint of the defined interval, that is, 4.5dB is the spherical wave and the cylindrical wave. The demarcation point of the wave; such an even division of the transition interval has been proven to be very suitable in practice; therefore, the basis for judging the expansion mode is as follows:

If the variation range of sound pressure is [3.0dB, 4.5dB) when the distance is doubled, it is determined that the expansion mode is the spherical wave expansion mode;

It should be noted that 3.0dB at the left end is a theoretical value. In practical applications, due to the existence of various errors, including but not limited to instrument error, measurement degree error, and environmental noise, this value will be within 3.0dB according to the actual environment. oscillates around the left and right, so this value should not be completely 3.0dB in the actual application process, but may be less than 3.0dB, such as 2.6dB;

If the variation range of sound pressure is [4.5dB, 6.0dB] when the distance is doubled, it is determined that the expansion mode is the cylindrical wave expansion mode;

It should be noted that the 6.0dB at the right end is a theoretical value. In practical applications, due to the existence of various errors, including but not limited to instrument error, measurement error, and environmental noise, this value will be based on the actual environment, at 6.0dB oscillates around the left and right, so this value should not be completely 6.0dB in the actual application process, but may be greater than 6.0dB, such as 7.5dB;

S330. According to the interference effect corresponding to the waveform of the sound pressure-distance relative change curve in each stage, confirm the far and near fields of each stage; wherein:

If the coincidence degree between the sound pressure-distance relative change curve and the fitting curve at this stage is not lower than the preset minimum coincidence threshold, and the fluctuation degree of the sound pressure-distance relative change curve at this stage is lower than the manually preset threshold If the fluctuation index has the lowest threshold value and is marked as near field in S320, it is confirmed that this stage is near field.

If the coincidence degree of the sound pressure-distance relative change curve and the fitting curve in this stage is not lower than the minimum coincidence degree threshold, and is marked as far field in S320, it is confirmed that this stage is far field.

If the fluctuation degree of the relative change curve of sound pressure-distance in this stage is lower than the minimum threshold of fluctuation index, and the degree of coincidence between the relative change curve of sound pressure-distance in this stage and the fitting curve is lower than the minimum threshold of coincidence degree, and the If the relative change curve of sound pressure-distance fluctuates around the fitting curve, it is confirmed that this stage is a transition zone.

S340. Obtain the high-precision first demarcation point position and the high-precision second demarcation point position according to the relationship between the confirmed stages; specifically:

In the range between the near field and the transition zone, the first turning point encountered from the near field is the position of the high-precision first demarcation point.

In the range between the transition zone and the far field, the second turning point encountered from the transition zone is the position of the high-precision second demarcation point.

Then, all high-precision first demarcation point positions are packaged, and all high-precision second demarcation point positions are packaged, and are output as the result of this step.

S400. Perform the boundary point verification operation according to the low-precision first boundary point position, the low-precision second boundary point position, the high-precision first boundary point position, and the high-precision second boundary point position, and obtain the boundary point consistency evaluation result and The boundary point range; the boundary point consistency evaluation result and the boundary point range are the final results of the present invention.

In this specific embodiment, obtaining the demarcation point consistency evaluation result and the demarcation point range specifically includes the following steps:

Sa410. Compare the position of the high-precision first dividing point with the low-precision first dividing point one by one, and perform the following operations according to the comparison result:

If the position of the high-precision first demarcation point is exactly the same as the position of the low-accuracy first demarcation point, or the position of the high-precision first demarcation point is within the range covered by the circle used as the position of the low-accuracy first demarcation point, then at the demarcation point Add the string "the first demarcation point is successful" in the consistency evaluation result; at the same time, assign the position of the high-precision first demarcation point to the first demarcation point; and then execute Sa430.

If the position of the high-precision first demarcation point does not overlap with the position of the low-precision first demarcation point, add the character string "Failed to obtain the first demarcation point" in the demarcation point consistency evaluation result; then execute Sa430.

It should be noted that if a failure occurs, the model must be rechecked and recalculated; there are many reasons for failure, mainly from objective data noise, such as collection objects, collection equipment, etc.; therefore, multiple collections, calculations, and verifications are necessary.

Sa420. Compare the position of the high-precision second dividing point with the low-precision second dividing point one by one, and perform the following operations according to the comparison result:

If the position of the high-precision second demarcation point is exactly the same as the position of the low-accuracy second demarcation point, or the position of the high-precision second demarcation point is within the range covered by the circle used as the position of the low-accuracy second demarcation point, then at the demarcation point Add the character string "Second demarcation point obtained successfully" to the consistency evaluation result; at the same time, assign the position of the high-precision second demarcation point to the second demarcation point; and then execute Sa430.

If the position of the high-precision second boundary point does not overlap with the position of the low-precision second boundary point, add the character string "Failed to obtain the second boundary point" in the boundary point consistency evaluation result; then execute Sa430.

It should be noted that, if a failure occurs here, the model needs to be checked again and recalculated, and will not be repeated here.

Sa430. Output the consistency evaluation result of the demarcation point after adding strings by Sa410 and Sa420; at the same time, pack the first demarcation point and the second demarcation point as the demarcation point range and output.

In order to verify the reliability of the method of the present invention, this specific embodiment further provides the following three steps, considering the non-fixed frequency of the underwater target, the natural frequency of the underwater target, and the influence of the sound source frequency on the far and near fields of the seismic wave. The simulation results and corresponding descriptions of the low-precision division operation of the far and near fields of the seismic wave in this case;

It will be explained in detail as follows:

Consider the underwater target with non-fixed frequency:

As shown in Figures 4a-4f, it is the relative change curve of sound pressure-distance along the y-direction of the seabed under the excitation of vibration sources with frequencies of 5Hz, 10Hz, 20Hz, 30Hz, 40Hz, and 50Hz.

It can be seen from Figures 4a to 4f that each sound pressure-distance relative curve varies with distance and can be divided into three regions. The boundary between two adjacent regions is the first boundary; the one that is closer to the origin is the first boundary The point farther from the origin is the second demarcation point; among which: the first demarcation point is mainly concentrated around 102m, and the second demarcation point is mainly concentrated after 103m; the relative change curve of sound pressure-distance is from the origin to the first demarcation point In the first region between , that is, the concept "first stage" mentioned above, it can be seen from the curve that the sound pressure decays rapidly; the relative change curve of sound pressure-distance is from the first dividing point to the second dividing point. In the second region in between, namely the concept "second stage" mentioned above, the attenuation speed of the sound pressure amplitude slows down and fluctuates up and down; the sound pressure-distance relative change curve is the third after the second dividing point In the region, that is, the concept "third stage" mentioned above, the waveform gradually tends to be flat, showing a linear trend.

It should be noted that, regarding the three stages, under the non-natural frequency, further explanation is required as follows:

For the first stage, it can be seen from the variation law of sound pressure under different vibration source frequencies that when the receiving distance doubles, the sound pressure attenuation range of the relative change curve of sound pressure-distance in the first stage is between 4.0dB and 6.5dB. At this time, the direct wave plays a major role in the seismic wave field, and the interference effect of each wave component in the seismic wave field Relatively weak; and because the frequency of the vibration source is very low, its wavelength is much larger than the geometric scale of the target, and the near-field interference effect is relatively weak; Near-field effects also play a role.

For the second stage, the relative change curve of sound pressure-distance. In the second stage, when the sound pressure doubles the receiving distance, the attenuation range is between 3.3dB and 5.0dB, and its propagation law is also between the attenuation law of spherical waves and the columnar wave. Compared with the curve in the first stage, it is slightly biased towards the cylindrical wave; the reason for this phenomenon is that with the increase of the receiving distance, the reflected wave, Scholte wave and other components in the wave component The influence on the seismic wave field increases gradually, the complexity of the interference of the seismic wave field increases, and the fluctuation of the waveform is accelerated. Due to the complicated propagation law in this stage, it mainly presents the state of oscillating propagation, which cannot be judged as far field or near field, so this area is judged as the transition area between far and near fields of seismic waves.

For the third stage, the relative change curve of sound pressure-distance in the third stage, when the receiving distance is doubled, the sound pressure attenuation range is 2.8dB ~ 3.4dB, and the propagation law is very close to the propagation law of cylindrical waves; this When the propagation distance is longer, the influence of underwater acoustic waves on the seismic wave field is reduced, and the main component is the Scholte wave. At this time, the interference is relatively stable and the waveform is relatively smooth; based on this, it is determined that this stage is the far field of seismic waves.

It should be noted that the above description of the three stages is the theoretical basis for the determination of the near field, the transition field and the far field in the present invention.

As shown in Figures 5a-5b, it is the relative change curve of sound pressure-distance calculated when f=50Hz; the near-field region can be judged more accurately through this figure; because the waveform of the transition region is incomplete, it is impossible to pass Human observation can directly and specifically read out the difference in the variation law of the near field and the transition zone, which is also one of the technical problems to be solved by the present invention; There is a relatively obvious demarcation point; in addition, it can be seen that there is indeed wave field fluctuation caused by interference in the near-field region; therefore, Figures 5a-5b prove that the method of the present invention is effective.

It should be further explained that the physical meaning of the above waveform changes is detailed as follows: still take the relative change curve of sound pressure-distance when f=50Hz as an example, for the convenience of description, the sound pressure wave shown in Figures 6a to 6c is specially derived. Field snapshots are taken as an example. In this specific embodiment, the snapshots of the sound pressure wavefield at three moments of 0.07s, 0.20s, and 1.10s are captured and displayed. This is because these three snapshots of the sound pressure wavefield are very typical and have Representative; a 20m×20m grid is used here; when the time is 0.07s, the range of the red area is the largest, and its peripheral waveform does not appear to diffuse significantly; since the coordinate origin is taken at 40m from the center of the circle, the sound pressure waveform is in the distance The center of the circle is 160m, that is, 120m from the origin of the coordinates, and a near field is formed near it; then with the continuous excitation of the continuous vibration source, when the time is 0.2s, uneven color blocks have appeared in the waveform near the center of the circle 340m, that is, light blue and At the intersection of the dark blue blocks, this is the transition between the far and near fields; and when the sound pressure propagates to 1.1s, the far field with uniform color blocks has appeared, and the overall waveform has stabilized at this time, which is the range of the far field; compared to Figure 6a It can be seen from the three figures of ~6c that the range of the red central area gradually decreases during the sound pressure diffusion process, and then increases due to the continuous superposition of the vibration sources. Fluctuations correspond to, further verifying the effectiveness of the method of the present invention.

As shown in Table 1, through the low-precision division operation of the far and near fields of the seismic wave of the S200, the boundary points of the far and near fields under different vibration source frequencies can be obtained:

Table 1. Low-precision division list of far and near field demarcation points under different vibration source frequencies (non-natural frequencies)

Frequency (Hz) First dividing point (m) Second dividing point (m) 5 70 1660 10 80 1620 20 90 1580 30 95 1660 40 100 1720 50 110 1640

It should be further explained that the boundary values of the far and near fields under different vibration source frequencies shown in Table 1 are drawn into a curve, and Figures 7a-7b can be obtained. It can be seen that with the increase of the vibration source frequency, the near-field critical values are all Gradually increases, the overall linear trend, and the far-field threshold fluctuates, but the overall remains unchanged.

Figures 7a-7b should be understood as follows: when the frequency of the vibration source decreases, the wavelength increases, and the size of the underwater target becomes smaller relative to the wavelength. Since the direct wave plays the main role in the near-field region, the size of the underwater target has a significant effect on the near-field effect. Therefore, the lower the frequency is, the smaller the target size is in comparison, and the closer it is to a point source, the weaker the interference generated by the various fluctuation components in the induced submarine seismic waves, so it is difficult to form a near field, and the near field is demarcated. In the far field, the propagation distance is relatively long, and the main component is the Scholte wave. The influence of the size of the underwater target on the interference is reduced, and the interference is relatively stable, so the far-field boundary value generally remains unchanged.

Consider the case of the natural frequency of an underwater target:

Under the natural frequency, 5.607Hz, 15.415Hz, 25.897Hz, 35.530Hz, 45.851Hz are selected as the main vibration sources for simulation.

In the simulation process, considering the natural frequency of the mode of the underwater target, the changes in the far and near fields of the seismic wave are shown in Figures 8a-8e.

Obviously, compared with the ordinary case, the overall amplitude of the excitation sound pressure considering the natural frequency is slightly larger than the non-natural frequency; the fundamental reason for this difference is caused by the resonance of the underwater target; for comparison, the relative change of sound pressure-distance The curve is still divided into the first stage, the second stage and the third stage, as follows:

For the first stage, it can be seen from the variation law of sound pressure under different vibration source frequencies that when the receiving distance is doubled, the sound pressure attenuation range of the relative change curve of sound pressure-distance in the first stage is between 3.9-6.6dB. , its propagation law is between the attenuation law of spherical wave and cylindrical wave, but it is closer to spherical wave; at this time, the direct wave plays the main role in the seismic wave field, and the interference effect of each wave component in the seismic wave field is relatively weaker.

For the second stage, the relative change curve of sound pressure-distance. In the second stage, when the sound pressure doubles the receiving distance, the attenuation range is between 3.3dB and 5.1dB, and the propagation law is also between the attenuation law of spherical waves and the columnar wave. Between the surface wave attenuation laws, but the curve in the first stage is slightly biased towards the cylindrical wave, the complexity of the seismic wave field interference increases, which accelerates the fluctuation of the waveform. Due to the complicated propagation law in this stage, it mainly presents the state of oscillating propagation, which cannot be judged as far field or near field, so this area is judged as the transition area between far and near fields of seismic waves.

For the third stage, the sound pressure-distance relative change curve in the third stage, when the receiving distance doubles, the sound pressure attenuation range is 2.7dB ~ 3.4dB, and the propagation law is very close to the propagation law of cylindrical waves; this When the propagation distance is longer, the influence of underwater acoustic waves on the seismic wave field is reduced, and the main component is the Scholte wave. At this time, the interference is relatively stable and the waveform is relatively smooth; based on this, it is determined that this stage is the far field of seismic waves.

After considering the fixed frequency, in order to improve the accuracy of the near-field characteristic analysis, the model is reconstructed for the near-field area that is easily affected by the grid accuracy, the model area is reduced to 200m, and the grid size is reset to 5m×5m; The relative change curves of sound pressure and distance excited by the natural frequencies of different modes are processed again according to the method of S200, and the boundary points of the far and near fields at the natural frequencies of each mode can be obtained, as shown in Table 2:

Table 2. Low-precision division list of far and near field demarcation points under different vibration source frequencies (at natural frequencies)

Frequency (Hz) First dividing point (m) Second dividing point (m) 5.6071 70 1640 15.415 85 1580 25.897 95 1540 35.530 100 1600 45.851 110 1640

As shown in Figures 9a-9b, also according to the method of S200, the boundary values of the far and near fields under the natural frequencies of different modes are drawn into a curve; it is obvious that with the increase of the natural frequency, the critical value of the near field gradually increases, and the overall linearity trend, while the far-field threshold fluctuates up and down but generally remains constant; this is consistent with the results at extrinsic frequencies.

As shown in Figures 10a to 10b, and then also according to the method of S200, the boundary values of the far and near fields of all frequencies are drawn into curves; With the increase of frequency, there is no obvious sudden change in the change trend of the critical value of the far and near fields; this shows that in the very low frequency range, the natural frequency has limited influence on the boundary between the far and near fields of submarine seismic waves.

It can then be concluded that the method of the present invention is effective even when natural frequencies are taken into account.

It should be noted that transitive relationships should also be taken into account:

The transfer relationship here refers to using the frequency of the vibration source as the input and the sound pressure as the output to test the transfer relationship between the input and the output.

As shown in Figure 11, the least squares method is used to fit the sound pressure waveforms at different frequencies to obtain a fitting surface.

From Figure 12, the relative curve of sound pressure-distance at different frequencies can be intercepted; here, taking f=18Hz as an example, it can be read out: when f=18Hz, the near-field-transition zone boundary point, that is, the first boundary point, About 90m; the transition zone-far-field demarcation point, that is, the second demarcation point, is about 1580m.

Considering the influence of sound source frequency on the far and near fields of seismic waves

Considering the different navigation speeds of underwater targets, different propeller speeds, and different radiated noise frequencies, it is also necessary to consider the influence of the frequency of the sound source on the far and near fields. Therefore, a sediment-free simulation model is used, and a For a single-frequency sound source, set the load type to concentrated force, the magnitude is 10 ⁶ N, and its position is shown in Figure 13.

In this specific embodiment, 5Hz, 10Hz, 20Hz, 30Hz, 40Hz, and 50Hz are still selected as the sound source frequencies here; the underwater target is fixed at a distance of 50m from the seabed, and the sound source frequency of the propeller tail is changed to verify that the present invention can analyze the sound source. It is still effective under the influence of source frequency changes on the far and near fields of submarine seismic waves.

As shown in Figure 14, since the sound source is loaded on the central axis of the underwater target, there is no need to consider the influence of different directions, so it is only necessary to verify the length direction of the underwater target, that is, the y direction, and the construction method of the coordinate system is the same as the previous one. , only the sound source position has changed.

In order to improve the calculation efficiency, the interval of each receiving point is firstly set to 20m. Since the target is placed in the center of the model, the receiving distance is set to L/2, which is 4000m, and the stable sound pressure time domain waveform is obtained after running; f=40Hz For example, after normalizing the stable sound pressure time-domain waveforms received by the receiving points at the target distances of 200m, 400m, 600m, 800m, and 1000m at the sound source frequency, Figure 15 can be obtained.

It can be clearly seen from Figure 15 that the sound pressure time-domain waveform under the sound source condition also produces a certain interference phenomenon.

Then, according to the method of S200 again, the changes of the far and near fields of the seismic waves of 5 Hz, 10 Hz, 20 Hz, 30 Hz, 40 Hz, and 50 Hz are shown in Figs. 16a-16f.

Obviously, the relative change curve of sound pressure-distance is still divided into the first stage, the second stage and the third stage, as follows:

For the first stage, it can be seen from the variation law of sound pressure under different vibration source frequencies that when the receiving distance is doubled, the sound pressure attenuation range of the relative change curve of sound pressure-distance in the first stage is between 5.6dB and 6.4dB. During the period, the interference effect of each wave component in the seismic wave field is relatively weak, and it is still in the near field.

For the second stage, the relative change curve of sound pressure-distance. In the second stage, when the sound pressure doubles the receiving distance, the attenuation range is between 3.7dB and 5.5dB. The complexity of the seismic wave field interference increases, which speeds up the waveform ups and downs. Still a transition zone.

For the third stage, the relative change curve of sound pressure-distance in the third stage, when the receiving distance doubles, the sound pressure attenuation range is 2.7dB ~ 3.5dB, basically no interference occurs, and the waveform is relatively smooth; This stage is the far field of seismic waves.

Then still follow the steps of S200 to obtain a snapshot of the sound pressure wave field.

As shown in Figures 17a to 17c, taking the snapshot of the sound pressure wave field at f=30 Hz as an example, a 20m×20m grid is used.

We still select the snapshots of the sound pressure wave field at the time of 0.07s, 0.20s and 1.10s. Since the coordinate origin is taken at 40m from the center of the circle, the sound pressure at 0.07s is at 140m from the center of the circle, that is, 100m from the coordinate origin. The near field is formed nearby; then with the continuous excitation of the continuous sound source, it can be seen that at 0.20s, the waveform has a yellow and green uneven color block near the center of the circle 340m, and the transition area between the far and near fields is initially formed; and when the sound pressure propagates At 1.10s, the far-field with uniform color blocks has appeared, and the overall waveform has become stable at this time.

In order to improve the accuracy of verification, model reconstruction was performed on the near-field area susceptible to grid accuracy, the model area was reduced to 200m, and the grid size was reset to 5m×5m. Then, using the steps of S200 again, the demarcation point of the far and near fields considering the transitivity can be obtained, as shown in Table 3:

Table 3. Low-precision division of far and near field demarcation points at different source frequencies (considering transmissibility)

As shown in Figures 18a-18b, also according to the method of S200, the boundary values of the far and near fields under different modal natural frequencies are drawn into a curve; it is obvious that with the increase of the natural frequency, the critical value of the near field gradually increases, and the overall linearity trend, while the far-field threshold fluctuates up and down but remains the same overall; this is consistent with the results at extrinsic frequencies and at natural frequencies.

As shown in Figure 19, the sound pressure waveforms at different sound source frequencies are summarized, the sound source frequency is used as the input, and the sound pressure is used as the output, and the transfer relationship between the input and output is analyzed. The sound pressure waveform is fitted to obtain a fitting surface.

As shown in Figure 20, taking f=47Hz as an example, the corresponding curve is intercepted in the propagation distance-sound pressure plane; it is obvious that the first demarcation point is about 110m and the second demarcation point is about 1720m when f=47Hz.

The above simulation results prove once again that the method of the present invention is still effective when considering the influence of the frequency of the sound source on the far and near fields of the seismic wave.

In the foregoing Detailed Description, various features are grouped together in a single embodiment for the purpose of simplifying the disclosure. This method of disclosure should not be interpreted as reflecting an intention that embodiments of the claimed subject matter require more features than are expressly recited in each claim. Rather, as the following claims reflect, present invention lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby expressly incorporated into the Detailed Description, with each claim standing on its own as a separate preferred embodiment of this invention.

The disclosed embodiments are described above to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit and scope of this disclosure. Thus, the present disclosure is not intended to be limited to the embodiments set forth herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods in order to describe the above embodiments, but one of ordinary skill in the art will recognize that further combinations and permutations of the various embodiments are possible. Accordingly, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of the appended claims. Furthermore, with respect to the term "comprising," as used in the specification or claims, the word is encompassed in a manner similar to the term "comprising," as if "comprising," were construed when used as a conjunction in the claims. Furthermore, any use of the term "or" in the specification of the claims is intended to mean a "non-exclusive or."

The specific embodiments described above further describe the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the present invention is not limited to the above-mentioned embodiments, and many modifications are possible. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention shall be considered to belong to the protection scope of the present invention.

Here, it should be noted that the descriptions of the above technical solutions are exemplary, and this specification may be embodied in different forms, and should not be construed as being limited to the technical solutions set forth herein. Rather, these descriptions are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art. Furthermore, the technical solutions of the present invention are limited only by the scope of the claims.

The disclosed shapes, dimensions, ratios, angles and numbers used to describe various aspects of the specification and claims are merely examples and, therefore, the specification and claims are not limited to the details shown. In the following description, when a detailed description of a related known function or configuration is determined to unnecessarily obscure the gist of the specification and claims, the detailed description will be omitted.

Where "including", "having" and "comprising" are used as described in this specification, unless otherwise used, there may be another part or other parts, and the terms used may generally be singular but may also refer to the plural.

It should be noted that although the terms "first", "second", "top", "bottom", "one side", "the other side", "one end", "the other end", etc. may appear and be used in this specification to describe various components, but these components and parts should not be limited by these terms. These terms are only used to distinguish one component and part from another. For example, a first component could be termed a second component, and, similarly, a second component could be termed a first component, without departing from the scope of this specification, and the top and bottom components would also be They can be reversed or converted to each other; components on one end and the other can perform the same or different from each other.

In addition, in the construction of components, although there is no explicit description thereof, it is understood that certain error regions are necessarily included.

When describing a positional relationship, for example, when the positional sequence is described as "on," "above," "below," and "next," unless "exactly" or "next" is used Words or terms such as "directly" may also include situations in which they are not in contact or in contact with each other. If it is mentioned that a first element is "on" a second element, it does not mean that the first element must be on the second element in the figures. The upper and lower parts of the components will change depending on the viewing angle and orientation. Thus, in the drawings or in actual construction, references to a first element being "on" a second element may include that the first element is "below" the second element as well as the first element being "on" the second element above". When describing a temporal relationship, unless "just" or "directly" is used, when describing "after", "subsequent", "subsequently" and "before", discontinuities between steps may be included. The features of the various embodiments of the present invention may be combined or spliced with each other, in part or in whole, and may be implemented in various configurations as will be well understood by those skilled in the art. Embodiments of the present invention may be performed independently of each other or may be performed together in an interdependent relationship.

Claims (9)

1. a method for discriminating the far and near fields of seismic waves induced by target navigation in water, is characterized in that: comprise the following steps: S100. Collect the original data of the shallow sea seismic wave field; the original data of the shallow sea seismic wave field include the sound pressure time-domain waveform and the sound pressure cloud image taken at the interface between the seawater and the seabed; then process the sound pressure cloud image into a sound pressure wave field snapshot collection Then, the sound pressure time domain waveform is processed into a sound pressure-distance relative change curve; the sound pressure wave field snapshot set includes the sound pressure wave field snapshots arranged in increasing time order; S200. According to the sound pressure wave field snapshot collection, perform a low-precision division operation of the far and near fields of the seismic wave, and obtain a low-precision first demarcation point position and a low-precision second demarcation point position; S300. According to the sound pressure-distance relative change curve, perform a high-precision division operation of the far and near fields of the seismic wave, and obtain a high-precision first demarcation point position and a high-precision second demarcation point position; S400. Perform a boundary point verification operation according to the low-precision first boundary point position, the low-precision second boundary point position, the high-precision first boundary point position, and the high-precision second boundary point position, The demarcation point consistency evaluation result and the demarcation point range are obtained; the demarcation point consistency evaluation result and the demarcation point range are the final results of the present invention. 2. the far-near-field method of distinguishing the seismic wave induced by underwater target navigation according to claim 1, it is characterized in that: in S100, described sound pressure time-domain waveform by being arranged on the central axis of the seabed surface in the built shallow sea seabed seismic wave model A plurality of receiving points are collected and obtained; the receiving points are arranged in a grid form, and the distances between them are equal. 3. The method according to claim 1, characterized in that: the sound pressure time domain waveform is the time domain waveform under the two-dimensional rectangular coordinate system, wherein: the sound pressure time domain waveform The origin of is the sound pressure intensity received by the receiving point at time 0, the horizontal axis is time, and the vertical axis is the sound pressure intensity. 4. The method according to claim 1, characterized in that: in S100, the sound pressure cloud map is airspace data under three-dimensional coordinates, wherein: the origin is manually preset, and the position is Where the projected distance of the geometric center of the underwater target on the seabed surface is two grids, the horizontal axis is the abscissa of the sound pressure signal from the artificially preset origin, the vertical axis is the ordinate of the sound pressure signal from the origin, and the vertical axis represents the The energy of the sound pressure signal. 5. The method according to claim 1, characterized in that: in S100, the sound pressure nephogram is processed into a collection of sound pressure wave field snapshots, which specifically comprises the following steps: S110. Intercept the sound pressure nephogram within an artificially preset time range at an artificially preset interception frequency, and obtain a snapshot of the sound pressure wave field for each interception; S111. Arrange each of the sound pressure wavefield snapshots in an increasing order of time, and then pack them to obtain the sound pressure wavefield snapshot set. 6. The method for judging the far and near fields of seismic waves induced by underwater target navigation according to claim 1, characterized in that: the sound pressure time-domain waveform is processed into a sound pressure-distance relative change curve as described in S100, specifically comprising the following steps : S120. From all the collected sound pressure time-domain waveforms, select a manually preset number, and the waveforms fluctuate up and down in the fluctuation range with the peak as the core and on both sides of the peak after excitation for the excitation duration. the sound pressure time-domain waveform; the excitation duration is manually preset; the fluctuation range is manually preset; S121. For each of the sound pressure time-domain waveforms selected from S120, extract sound pressure peaks one by one; S122. Take the logarithm of each of the sound pressure peaks, and then arrange the corresponding receiving points in order to obtain the sound pressure-distance relative change curve. 7. The method according to claim 1, characterized in that: in S200, the low-precision division operation of the far and near fields of the seismic wave specifically comprises the following steps: S210. Perform corresponding calibration operations on each grid on each of the sound pressure wave field snapshots in the sound pressure wave field snapshot set according to the following standards: If the number of grids occupied by the central energy ring in the area where the grid is located is the largest among all time points, and the outer waveform contains only one color, the grid is demarcated as the low-precision first dividing point; If the outer waveform of the area where the grid is located is restored to a color, and the wave field appears as a regular circular ring, the grid is demarcated as the low-precision second dividing point; S220. Count the number of grids continuously arranged between the origin under the three-dimensional coordinates of the sound pressure nephogram and each of the low-precision first demarcation points; then count each of the low-precision first demarcation points Multiply the number of grids between the origin of the coordinate system and the side length of the grid to obtain the position of the low-precision first dividing point; then perform the following operations according to the position of the low-precision first dividing point: If the position of the low-precision first demarcation point does not straddle the middle of a grid, confirm that the position of the low-precision first demarcation point is correct, and then output the position of the low-precision first demarcation point; If the position of the low-precision first dividing point straddles the middle of a grid, a circle is drawn with the position of the low-precision first dividing point as the center and the length of the grid side as the radius; The range covered by the circle is used as the position of the new low-precision first dividing point, and then the new low-precision first dividing point position is output; S230. Count the number of grids between the origin of the coordinate system and each of the low-precision second dividing points; then calculate the number of grids between each of the second low-precision dividing points and the origin of the coordinate system with the grid Multiply the side lengths to obtain the position of the low-precision second dividing point; and then perform the following operations according to the position of the low-precision second dividing point: If the position of the low-precision second demarcation point does not straddle the middle of a grid, confirm that the position of the low-precision second demarcation point is correct, and then output the position of the low-precision second demarcation point; If the position of the low-precision second dividing point straddles the middle of a grid, draw a circle with the position of the low-precision second dividing point as the center and the length of the grid side as the radius; The range covered by the circle is used as the new low-precision second dividing point position, and then the new low-precision second dividing point position is output. 8. The method according to claim 1, characterized in that: in S300, the high-precision division operation of the far and near fields of the seismic wave specifically comprises the following steps: S310. Fit the sound pressure-distance relative change curve to obtain a fitting curve; then divide the sound pressure-distance relative change curve into different stages; the stages include a first stage, a second stage and a Phase III; where: The first stage is the sound pressure-distance relative change curve covered by the range from the origin to the first turning point; the first turning point is starting from the origin and extending the sound pressure-distance relative change curve The first turning point encountered in the positive direction of travel; The second stage is the relative change curve of sound pressure-distance covered by the range from the first turning point to the second turning point; the second turning point is the relative change of sound pressure-distance along the line The second turning point encountered by the forward travel of the curve; The third stage is the relative change curve of sound pressure-distance covered by the range from the second turning point to the third turning point; the third turning point is the relative change of sound pressure-distance along the line The third turning point encountered by the forward travel of the curve; S320. According to the attenuation degree of the sound pressure value in each of the stages one by one, determine the expansion mode of the seismic wave in the stage; the expansion mode includes a partial spherical wave expansion mode and a partial cylindrical wave expansion mode; Then, the corresponding stage is marked with far and near fields according to the expansion mode; wherein: If the expansion mode is the deviatoric surface wave expansion mode, marking the corresponding stage as a near field; If the expansion mode is the deviated cylindrical wave expansion mode, marking the corresponding stage as far field; S330. According to the interference effect corresponding to the waveform of the sound pressure-distance relative change curve in each of the stages, confirm the far and near fields for each of the stages; wherein: If the degree of coincidence between the sound pressure-distance relative change curve and the fitting curve in this stage is not lower than the artificially preset minimum coincidence degree threshold, and the sound pressure-distance relative change in this stage is If the fluctuation degree of the curve is lower than the artificially preset lowest threshold of the fluctuation index, and is marked as a near field in S320, it is confirmed that the said stage is a near field; If the coincidence degree of the relative change curve of sound pressure-distance and the fitting curve in this stage is not lower than the minimum coincidence degree threshold, and is marked as far field in S320, the stage is confirmed for the far field; If the degree of fluctuation of the relative change curve of sound pressure-distance in the stage is lower than the lowest threshold of the fluctuation index, and the relative change curve of sound pressure-distance in the stage is the fitting curve The degree of coincidence is lower than the minimum threshold of the degree of coincidence, and the relative change curve of the sound pressure-distance of the stage fluctuates up and down around the fitting curve, then confirm that the stage is a transition zone; S340. Obtain the high-precision first demarcation point position and the high-precision second demarcation point position according to the confirmed relationship between the stages; specifically: In the range between the near field and the transition zone, the first turning point encountered from the near field is the position of the high-precision first demarcation point; In the range between the transition zone and the far field, the second turning point encountered from the transition zone is the position of the high-precision second demarcation point; Then, all the high-precision first demarcation point positions are packaged, and all the high-precision second demarcation point positions are packaged, and output as a result of this step. 9. The method according to claim 8, characterized in that: in S400, the obtained demarcation point consistency evaluation result and demarcation point range specifically comprise the following steps: Sa410. Compare the position of the high-precision first demarcation point with the position of the low-precision first demarcation point one by one, and perform the following operations according to the comparison result: If the position of the high-precision first demarcation point is exactly the same as the position of the low-accuracy first demarcation point, or the position of the high-precision first demarcation point is covered by the circle used as the position of the low-accuracy first demarcation point Within the range of , then add the character string "the first demarcation point was obtained successfully" in the demarcation point consistency evaluation result; at the same time, assign the position of the high-precision first demarcation point to the first demarcation point; then execute Sa430; If the position of the high-precision first demarcation point does not overlap with the position of the low-precision first demarcation point, add the character string "Failed to obtain the first demarcation point" in the demarcation point consistency evaluation result; then execute Sa430; Sa420. Compare the position of the high-precision second demarcation point with the position of the low-precision second demarcation point one by one, and perform the following operations according to the comparison result: If the position of the high-accuracy second demarcation point is exactly the same as the position of the low-accuracy second demarcation point, or the position of the high-accuracy second demarcation point is covered by the circle used as the position of the low-accuracy second demarcation point Within the range of , then add the character string "Second demarcation point is obtained successfully" in the demarcation point consistency evaluation result; at the same time, assign the position of the high-precision second demarcation point to the second demarcation point; then execute Sa430; If the position of the high-precision second demarcation point does not overlap with the position of the low-precision second demarcation point, add the character string "Failed to obtain the second demarcation point" in the demarcation point consistency evaluation result; then execute Sa430; Sa430. The demarcation point consistency evaluation result after strings are added by Sa410 and Sa420 is the demarcation point consistency evaluation result; meanwhile, the first demarcation point and the second demarcation point are packaged as the demarcation point point range.

Images