CN114757241A - Doppler parameter coupling line extraction method - Google Patents

Doppler parameter coupling line extraction method Download PDF

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CN114757241A
CN114757241A CN202210677659.5A CN202210677659A CN114757241A CN 114757241 A CN114757241 A CN 114757241A CN 202210677659 A CN202210677659 A CN 202210677659A CN 114757241 A CN114757241 A CN 114757241A
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grid
parameter coupling
doppler
parameter
cost function
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CN114757241B (en
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高大治
高伟
宋文华
李小雷
孙凯
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Ocean University of China
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    • G06F2218/02—Preprocessing
    • G06F2218/04—Denoising
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/50—Systems of measurement, based on relative movement of the target
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
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    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract

The application belongs to the technical field of underwater acoustic signal processing and underwater acoustic positioning, and provides a Doppler parameter coupling line extraction method, which comprises the following steps: extracting a line spectrum with Doppler frequency shift from a time spectrum of the underwater sound target radiation noise; constructing a search grid based on the motion parameters of the underwater sound target; traversing the search grid to obtain a cost function grid; determining a parameter coupling band from a cost function grid; sequentially generating a parameter coupling line corresponding to each motion parameter combination in the parameter coupling band; and sequentially bringing each generated parameter coupling line into a cost function grid, integrating along the direction of each parameter coupling line, and determining the parameter coupling line with the minimum integral value as a theoretical value of the Doppler parameter coupling line. The Doppler parameter coupling line extraction method can accurately obtain the theoretical value of the Doppler parameter coupling line of the underwater sound target.

Description

Doppler parameter coupling line extraction method
Technical Field
The application belongs to the technical field of underwater acoustic signal processing and underwater acoustic positioning, and particularly relates to a Doppler parameter coupling line extraction method.
Background
The parameters such as the motion speed, the positive transverse distance and the like of the underwater sound target can be estimated by utilizing the line spectrum with Doppler frequency shift in the radiation noise signal of the underwater sound target (Yandson, Wu II. the university of Harbin engineering proceedings. J. 1996,17(1): 38-44). Ferguson and Quinn, 1994, proposed extracting the Doppler signal instantaneous frequency using time-frequency analysis, and then fitting the extracted frequency to a model using least-squares to achieve target motion parameter estimation (B.G. Ferguson, B.G. Quinn, Application of the Short-time transducer Transform and the Wigner-Ville Distribution to the Acoustic Localization of Aircraft, Journal of the Acoustic Society of America, 96 (1994), 821-. In 2004, the Zhouyanxing et al proposed the Doppllerlet transform, and combined with the optimized global parameter search method, the parameters of the uniform motion object could be estimated. In 2020, Gaodeang et al proposed a method to apply Doppler-warping transform to the estimation of the motion parameters of an underwater acoustic target (Gaodeang, Gao Da Zhi, late, Wang Liang, Song Wen Hua. Doppler-warping transform and its application to the estimation of the velocity of an acoustic target motion [ J ]. Physics, 2021,70(12): 253-.
Although the above documents have disclosed different methods for estimating the motion parameters of an underwater acoustic target based on the doppler shift effect of an underwater acoustic signal, since the speed of sound in water is high and the speed of motion of the underwater target is low, the doppler shift phenomenon of the underwater acoustic signal is weak compared with that of the high-speed moving target in air, when the dual motion parameters (speed, nearest distance) of the underwater acoustic target are estimated by using the doppler shift of a single line spectrum, all the above methods have strong parameter coupling phenomenon, so that the estimation error of the motion parameters of the underwater acoustic target is too large, and the nearest distance and the speed value cannot be accurately located.
Disclosure of Invention
In order to solve the problems in the prior art, an object of the present application is to provide a method for extracting a doppler parameter coupling line, which is used to obtain a theoretical value of the doppler parameter coupling line of an underwater acoustic target, and specifically includes the following steps:
s1: extracting a line spectrum with Doppler frequency shift from a time spectrum of radiated noise of an underwater sound target, and determining a nearest arrival time of the underwater sound target based on the line spectrum
Figure DEST_PATH_IMAGE001
Wherein the time-frequency spectrum is determined based on an original signal of an underwater acoustic target radiation noise;
s2: constructing a search grid based on motion parameters of an underwater acoustic target, wherein the motion parameters include a velocity of the underwater acoustic target VAnd the nearest distance
Figure DEST_PATH_IMAGE002
Speed, velocityVIn a search range of
Figure DEST_PATH_IMAGE003
The step size of speed search is
Figure DEST_PATH_IMAGE004
Distance of closest approach
Figure 987148DEST_PATH_IMAGE002
In a search range of
Figure DEST_PATH_IMAGE005
The nearest distance search step is
Figure DEST_PATH_IMAGE006
；
S3: traversing the search grid to calculate each search grid point
Figure DEST_PATH_IMAGE007
The combination of motion parameters of
Figure DEST_PATH_IMAGE008
Corresponding generationFunction of price
Figure DEST_PATH_IMAGE009
Obtaining a cost function grid, wherein the cost function
Figure 573463DEST_PATH_IMAGE009
The method comprises the steps of calculating spectrum entropy after resampling the original signal;
s4: extracting all cost functions smaller than parameter coupling threshold value from the cost function grid
Figure DEST_PATH_IMAGE010
Corresponding cost function grid point
Figure DEST_PATH_IMAGE011
Obtaining a parameter coupling band;
s5: sequentially generating each cost function grid point in parameter coupling band
Figure 776037DEST_PATH_IMAGE011
The combination of motion parameters of
Figure DEST_PATH_IMAGE012
Corresponding parameter coupling lines;
s6: and (4) sequentially substituting each parameter coupling line generated in the step (S5) into the cost function grid, integrating along the direction of each parameter coupling line, and determining the parameter coupling line with the minimum integral value as the theoretical value of the Doppler parameter coupling line.
Further, step S3 includes the steps of:
s31: extracting any search grid point
Figure DEST_PATH_IMAGE013
Using combinations of motion parameters including at the search grid point
Figure DEST_PATH_IMAGE014
Doppler-warping operator of
Figure DEST_PATH_IMAGE015
Resampling original signals of underwater sound target radiation noise to obtain resampled signals
Figure DEST_PATH_IMAGE016
Wherein, in the process,
Figure DEST_PATH_IMAGE017
，cis the speed of sound in water;
s32: the calculation is combined with the motion parameters at that point
Figure 843350DEST_PATH_IMAGE014
Corresponding cost function
Figure DEST_PATH_IMAGE018
，
Wherein the content of the first and second substances,
Figure DEST_PATH_IMAGE019
in order to integrate the upper and lower limits,
Figure DEST_PATH_IMAGE020
is that it is
Figure 795738DEST_PATH_IMAGE016
In the form of
Figure DEST_PATH_IMAGE021
；
S33: and repeating the steps S31 and S32 until the search grid is traversed to obtain a cost function grid.
Preferably, the upper and lower limits of integration
Figure 431249DEST_PATH_IMAGE019
And determining according to the Doppler frequency broadening situation of the line spectrum.
Preferably, the parameter coupling threshold is determined based on a numerical distribution range of the cost function.
Further, step S5 includes the steps of:
s51: constructing a calculation grid of parameter coupling line theoretical values based on motion parameters of underwater acoustic targets, wherein the speedVIs calculated in the range of
Figure DEST_PATH_IMAGE022
The speed calculation step length is
Figure DEST_PATH_IMAGE023
Distance of closest approach
Figure DEST_PATH_IMAGE024
Is calculated in the range of
Figure DEST_PATH_IMAGE025
The closest distance calculation step is
Figure DEST_PATH_IMAGE026
；
S52: extracting any cost function grid point in the parameter coupling band
Figure DEST_PATH_IMAGE027
The combination of motion parameters of
Figure DEST_PATH_IMAGE028
；
S53: for the said
Figure 980174DEST_PATH_IMAGE028
Traversing the computational grid to compute each computational grid point
Figure DEST_PATH_IMAGE029
Of
Figure DEST_PATH_IMAGE030
Obtaining a reaction of
Figure DEST_PATH_IMAGE031
A corresponding grid of computation results, wherein,
Figure DEST_PATH_IMAGE032
to obtain the instantaneous frequency after Doppler-warping transform of the spectrum,
Figure DEST_PATH_IMAGE033
at calculation grid point
Figure DEST_PATH_IMAGE034
In the specific form of
Figure DEST_PATH_IMAGE035
Wherein the content of the first and second substances,
Figure DEST_PATH_IMAGE036
is the center frequency of the line spectrum,
Figure DEST_PATH_IMAGE037
to calculate grid points
Figure DEST_PATH_IMAGE038
A combination of motion parameters of (c);
s54: from and to
Figure DEST_PATH_IMAGE039
Extracting a plurality of local minimum value points from the corresponding calculation result grid, and generating and based on the local minimum value points
Figure DEST_PATH_IMAGE040
Corresponding parameter coupling lines;
s55: repeating steps S52-S54 until all cost function grid points within the parametric coupling band are traversed.
Preferably, the first and second electrodes are formed of a metal,
Figure DEST_PATH_IMAGE041
wherein
Figure DEST_PATH_IMAGE042
Are all positive integers.
Preferably, the
Figure DEST_PATH_IMAGE043
The concrete form of (A) is as follows:
Figure DEST_PATH_IMAGE044
。
the method for extracting the Doppler parameter coupling line provided by the embodiment of the application has the following beneficial effects:
(1) according to the method, the technical scheme that curve fitting is directly carried out through the local minimum value of the cost function is improved, the number of candidate motion parameter combinations for estimating the optimal parameter coupling line is effectively reduced by dividing the parameter coupling band, smooth parameter coupling lines are generated for the candidate motion parameter combinations in the parameter coupling band, the optimal parameter coupling line is selected as the theoretical value of the Doppler parameter coupling line, the problems of curve fluctuation, overlarge error and the like caused by the fact that curve fitting is directly carried out on the local minimum value of the cost function are effectively solved, and the accuracy of the extracted parameter coupling line is effectively improved.
(2) According to the method provided by the application, different grid densities are adopted for the search grid and the calculation grid, the grid density of the search grid is properly reduced, the parameter coupling band is determined as soon as possible in steps S3 and S4, and meanwhile the density of the calculation grid is properly improved, so that the accuracy of the parameter coupling line fitted in the step S5 is guaranteed. Through the arrangement of different grid densities, the parameter coupling band is accelerated to be determined, meanwhile, the fitting precision of the parameter coupling line is increased, and the balance between the searching speed and the calculation precision is realized.
Drawings
FIG. 1 is a schematic diagram of an underwater acoustic object motion model;
FIG. 2 is a spectrum of an original signal of a specific single frequency sound source radiated noise;
FIG. 3 is a LOFAR plot of radiated noise generated by a particular underwater acoustic target;
FIG. 4 is a diagram of a specific parametric coupling line fit by local minima of the cost function;
FIG. 5 is a flowchart of a Doppler parameter coupled line extraction method according to an embodiment of the present application;
FIG. 6 is a schematic diagram of partitioning a parametric coupling band from a cost function grid according to an embodiment of the present application;
fig. 7 is a flowchart illustrating an implementation of step S5 according to an embodiment of the present disclosure;
fig. 8A to 8C are thermodynamic diagrams of a plurality of candidate sets of motion parameter combinations obtained by the calculation result grid obtained in step S53;
FIG. 9 is a plurality of parametric coupling lines generated from local minima point fits for each of the computational result grids of FIGS. 8A-8C;
FIG. 10 is a Doppler parameter coupling line superimposed on a cost function grid thermodynamic diagram according to an embodiment of the present application;
FIG. 11 is a signal spectrum diagram according to an embodiment of the present application;
FIG. 12 is a theoretical value of Doppler parametric coupling lines superimposed on a thermodynamic diagram of a cost function grid according to an embodiment of the present application;
FIG. 13 shows theoretical values of Doppler parameter coupling lines and locations of actual motion parameters of a sound source, according to an embodiment of the present application;
FIG. 14 is a thermodynamic diagram of a cost function grid according to another embodiment of the present application;
fig. 15 shows theoretical values of doppler parameter coupling lines and locations of actual motion parameters of a sound source according to another embodiment of the present application.
Detailed Description
Hereinafter, the present application will be further described based on preferred embodiments with reference to the accompanying drawings.
In addition, various components on the drawings are enlarged or reduced for convenience of understanding, but this is not intended to limit the scope of the present application.
Singular references also include plural references and vice versa.
In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "inner", "outer", etc. are used for indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship which is usually arranged when the products of the embodiments of the present application are used, the description is only for convenience and simplicity, but the indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation and be operated, and thus, the application cannot be construed as being limited. Furthermore, the terms first, second, etc. may be used herein to distinguish between various elements, but these should not be limited by the order of manufacture or by importance to indicate or imply relative importance, and their names may differ from the descriptions and claims provided herein.
The terminology used in the description presented herein is for the purpose of describing embodiments of the application and is not intended to be limiting of the application. It should also be noted that unless otherwise explicitly stated or limited, the terms "disposed," "connected," and "connected" should be interpreted broadly, as if they were fixed or removable, or integrally connected; they may be mechanically coupled, directly coupled, indirectly coupled through intervening media, or interconnected between two elements. The specific meaning of the above terms in the present application will be specifically understood by those skilled in the art.
To better explain the technical solution of the present application, first, the principle of motion parameter estimation based on the radiated noise of an underwater acoustic target and the existing defects are explained.
FIG. 1 is a schematic diagram of a motion model of an underwater acoustic object, as shown in FIG. 1, the underwater acoustic object is a sound source 1 such as a ship or a transmitting transducer towed by the ship, and the sound source 1 is at a constant speed for a certain timeVPerforms linear motion and generates radiation noise which is transmitted in an underwater acoustic environment, and the real-time distance between a sound source 1 and a hydrophone 2 arranged in water is rThe closest distance to the hydrophone 2 and the corresponding closest point time during the process of the sound source 1 are respectively
Figure DEST_PATH_IMAGE045
And with
Figure DEST_PATH_IMAGE046
. Because the sound source 1 moves linearly relative to the hydrophone 2, the original signal of the radiation noise generated by the sound source 1 received by the hydrophone 2 will have a doppler shift effect, fig. 2 shows a spectrum of the original signal of the radiation noise of a specific single-frequency sound source, and it can be seen from fig. 2 that the single-frequency signal has a significant frequency band broadening phenomenon due to the doppler shift.
The time spectrum of the original signal of the radiation noise generated by the underwater acoustic target can be obtained by performing short-time fourier transform processing, and is generally represented by a low Frequency Analysis (lofar) graph. Fig. 3 shows a LOFAR diagram of the radiation noise generated by a specific underwater acoustic target, and from fig. 3, a plurality of parabolic line spectrums can be observed, which are respectively generated by various single-frequency noise sources (such as a propeller on a ship, mechanical equipment, a towing sound source emitting a single-frequency signal, and the like) included in the underwater acoustic target, and the parabola-like shape represents the doppler frequency shift phenomenon occurring in the process of gradually approaching the underwater acoustic target and moving away the hydrophone again. Specifically, the line spectrum including the doppler shift described above satisfies equation (1):
Figure DEST_PATH_IMAGE047
Wherein, the first and the second end of the pipe are connected with each other,
Figure DEST_PATH_IMAGE048
the original frequency of the above-mentioned monochromatic noise source (i.e. the center frequency of the line spectrum),cis the speed of sound in water (approximately constant when the underwater acoustic target is a close distance from the hydrophone).
It is clear that the closest point in time can be directly determined by the above LOFAR map
Figure 701046DEST_PATH_IMAGE046
On the basis of which the speed of the underwater acoustic target is continuously determined if necessaryVThe shortest distance, the most recent distance
Figure 104346DEST_PATH_IMAGE045
The information of the equal motion parameters can be obtained by performing Doppler-warping conversion on the original signal of the radiation noise and constructing
Figure DEST_PATH_IMAGE049
The search grid of (2) is performed in a manner of solving a cost function in the search grid.
Because the Doppler frequency shift generated by the movement of the underwater sound target is far smaller than that generated by the high-speed moving target in the air, the movement parameters
Figure 425606DEST_PATH_IMAGE049
Obvious parameter coupling phenomenon exists between the two, the expression is that the cost function obtained by calculation has a plurality of local minimum values, the positions of the local minimum values form a parameter coupling line, and the real motion parameters of the underwater sound target
Figure DEST_PATH_IMAGE050
I.e. on the parameter coupling line.
The parameter coupling line for accurately acquiring the real motion parameters of the underwater sound target as far as possible has important significance for accurately positioning the underwater sound target and the like. The existing method for determining the parameter coupling line is mainly implemented by performing curve fitting on a plurality of cost function local minimum value positions obtained by traversing a search grid, however, in the process of processing actual experimental data, as shown in fig. 4, due to the complexity of an underwater acoustic environment and an underwater acoustic target radiation noise signal, the positions of the cost function local minimum values often have the phenomena of fluctuation, drift and the like, so that the parameter coupling line obtained by fitting has a larger deviation with a parameter coupling line where a real motion parameter is located, and the precision of subsequent underwater acoustic target positioning is influenced. In view of the above problems in the prior art, it is necessary to provide a doppler parameter coupling line extraction method, which can accurately extract the theoretical value of the doppler parameter coupling line where the real motion parameter is located.
In order to solve the above problems in the prior art, an embodiment of the present invention provides a method for extracting a doppler parameter coupled line (fig. 5 is a flowchart of the method for extracting a doppler parameter coupled line provided in the embodiment of the present invention), which includes the following steps:
s1: extracting a line spectrum with Doppler frequency shift from a time spectrum of radiated noise of an underwater sound target, and determining a nearest arrival time of the underwater sound target based on the line spectrum
Figure 990055DEST_PATH_IMAGE001
Wherein the time-frequency spectrum is determined based on an original signal of an underwater acoustic target radiation noise;
s2: constructing a search grid based on motion parameters of an underwater acoustic target, wherein the motion parameters include a velocity of the underwater acoustic targetVAnd the nearest distance
Figure 258225DEST_PATH_IMAGE002
Speed ofVIn a search range of
Figure 312769DEST_PATH_IMAGE003
The step size of speed search is
Figure 24504DEST_PATH_IMAGE004
Distance of closest approach
Figure 797288DEST_PATH_IMAGE002
In a search range of
Figure 603570DEST_PATH_IMAGE005
The nearest distance search step is
Figure 794511DEST_PATH_IMAGE006
；
S3: traversing the search grid to calculate each search grid point
Figure 926415DEST_PATH_IMAGE007
The combination of motion parameters of
Figure 186495DEST_PATH_IMAGE008
Corresponding cost function
Figure 530889DEST_PATH_IMAGE009
Obtaining a cost function grid, wherein the cost function
Figure 576336DEST_PATH_IMAGE009
The method comprises the steps of calculating spectrum entropy after resampling the original signal;
s4: extracting all cost functions smaller than parameter coupling threshold value from the cost function grid
Figure 879142DEST_PATH_IMAGE010
Corresponding cost function grid point
Figure 564201DEST_PATH_IMAGE011
Obtaining a parameter coupling band;
s5: sequentially generating each cost function grid point in parameter coupling band
Figure 977865DEST_PATH_IMAGE011
The combination of motion parameters of (1)
Figure 127086DEST_PATH_IMAGE012
Corresponding parameter coupling lines;
s6: and (4) sequentially substituting each parameter coupling line generated in the step (S5) into the cost function grid, integrating along the direction of each parameter coupling line, and determining the parameter coupling line with the minimum integral value as the theoretical value of the Doppler parameter coupling line.
According to the method for extracting the Doppler parameter coupling line, after the traversal search is performed on the motion parameter search grid, the cost function is not obtained directly through the traversal calculation
Figure DEST_PATH_IMAGE051
Is fitted to obtain a parametric coupling line, but is based on a cost function
Figure 83017DEST_PATH_IMAGE051
The parameter coupling bands are divided according to the traversal calculation result, the motion parameter combinations in the parameter coupling bands are used as alternative motion parameter combinations, corresponding parameter coupling lines are generated for each alternative motion parameter combination, and finally the theoretical values of the Doppler parameter coupling lines are determined from the multiple alternative parameter coupling lines according to respective cost function integration results. According to the method, the number of the alternative motion parameter combinations for estimating the optimal parameter coupling line is effectively reduced by dividing the parameter coupling band, so that smoother parameter coupling lines are generated for the motion parameter combinations of all the alternatives in the parameter coupling band, the optimal parameter coupling line is selected as the theoretical value of the Doppler parameter coupling line, the problems of curve fluctuation, overlarge error and the like caused by directly performing curve fitting on the local minimum value of the cost function are effectively solved, and the precision of the extracted parameter coupling line is effectively improved.
The following describes steps S1 to S6 in detail with reference to the accompanying drawings and embodiments.
Step S1 is to extract a line spectrum from the time spectrum of the underwater acoustic target radiation noise, and in some embodiments, as shown in fig. 3, the time spectrum of the underwater acoustic target radiation noise may be calculated by short-time fourier transform and a LOFAR map may be generated, the line spectrum is selected from the map, and the closest point time of the underwater acoustic target is determined based on the morphology of the line spectrum
Figure 52110DEST_PATH_IMAGE001
。
At the time of determining the closest point of underwater acoustic target
Figure 269464DEST_PATH_IMAGE001
And the sound velocity in water is obtained through the measured datacThen, to further speed the underwater acoustic targetVThe shortest distance
Figure 476455DEST_PATH_IMAGE002
The estimation of the equal motion parameters needs to first carry out the estimation on the original signal of the radiation noiseRemoving Doppler shift effect, and specifically, setting radiation noise signal of underwater sound target at
Figure DEST_PATH_IMAGE052
Is transmitted at a momenttThe time of day is received and, as shown in figure 1,
Figure DEST_PATH_IMAGE053
the following geometrical relations exist between the two parts:
Figure DEST_PATH_IMAGE054
(2)
according to the formula (2), the motion parameters to be estimated are set
Figure DEST_PATH_IMAGE055
Doppler-warping operator of
Figure DEST_PATH_IMAGE056
And use
Figure 262008DEST_PATH_IMAGE056
Resampling the original signal of the radiated noise, wherein
Figure 469130DEST_PATH_IMAGE056
The concrete form of (A) is as follows:
Figure DEST_PATH_IMAGE057
(3)
doppler-warping operator shown in formula (3)
Figure 959017DEST_PATH_IMAGE056
Having a pair of parameters
Figure 817251DEST_PATH_IMAGE055
The sensitive properties, namely: when using true motion parameter combinations
Figure DEST_PATH_IMAGE058
Bringing in the operatorWhen the original signal is resampled, the resampled signal can eliminate Doppler frequency shift and restore to a single-frequency signal, and meanwhile, the Doppler frequency shift of the target in water is relatively small, and the motion parameter combination
Figure DEST_PATH_IMAGE059
There is a significant coupling phenomenon, i.e. there are also other combinations of motion parameters, which are brought into effect
Figure 914652DEST_PATH_IMAGE056
The re-sampled signal is in single frequency property, and the combination of the multiple motion parameters forms a parameter coupling line, so that the real motion parameter combination
Figure 858337DEST_PATH_IMAGE058
Is located on the parametric coupling line.
The accurate extraction of the parameter coupling line is of great significance for underwater sound target positioning, and is based on the parameters
Figure 620756DEST_PATH_IMAGE056
The single frequency characteristic of the resampled signal may be set as the motion parameter through step S2
Figure 599077DEST_PATH_IMAGE055
Then, the search grids are traversed through step S3, and the spectral entropy of the motion parameter combinations at each grid point is calculated as a cost function, so as to obtain a cost function grid.
In particular, in some preferred embodiments, speed VIn a search range of
Figure DEST_PATH_IMAGE060
The step size of speed search is
Figure DEST_PATH_IMAGE061
Distance of closest approach
Figure 333290DEST_PATH_IMAGE002
In a search range of
Figure DEST_PATH_IMAGE062
The nearest distance search step is
Figure DEST_PATH_IMAGE063
. Generating a search grid according to the search range and the search step length, wherein each search grid point
Figure DEST_PATH_IMAGE064
All correspond to a motion parameter combination to be searched
Figure DEST_PATH_IMAGE065
。
Specifically, in some preferred embodiments, step S3 further includes the steps of:
s31: extracting any search grid point
Figure 374058DEST_PATH_IMAGE013
Using combinations of motion parameters including at the search grid point
Figure 674590DEST_PATH_IMAGE014
Doppler-warping operator of
Figure 507416DEST_PATH_IMAGE015
Resampling original signals of underwater sound target radiation noise to obtain resampled signals
Figure 664728DEST_PATH_IMAGE016
Wherein, in the step (A),
Figure 583006DEST_PATH_IMAGE017
，cis the speed of sound in water;
s32: the calculation is combined with the motion parameters at that point
Figure 687228DEST_PATH_IMAGE014
Corresponding cost function
Figure 125294DEST_PATH_IMAGE018
，
Wherein the content of the first and second substances,
Figure 453507DEST_PATH_IMAGE019
in order to integrate the upper and lower limits,
Figure 796763DEST_PATH_IMAGE020
is that it is
Figure 501414DEST_PATH_IMAGE016
In the form of
Figure 43254DEST_PATH_IMAGE021
；
S33: and repeating the steps S31 and S32 until the search grid is traversed to obtain a cost function grid.
In the frequency spectrum of the resampled signal
Figure DEST_PATH_IMAGE066
When integration is performed, the upper and lower limits of integration are set
Figure DEST_PATH_IMAGE067
Can be determined from the doppler frequency broadening of the line spectrum. For example, the above-mentioned single-frequency sound source signal may be spectrally analyzed at the center frequency as illustrated by fig. 2
Figure DEST_PATH_IMAGE068
In the case of a nearby frequency broadening, the line spectrum at the center frequency can also be analyzed by the LOFAR diagram shown in FIG. 3
Figure 620997DEST_PATH_IMAGE068
The spread of nearby frequencies, and thus determining
Figure 451550DEST_PATH_IMAGE067
。
Traversing the search grid and calculating the gain through step S3After the cost function grid, the cost function grid can be represented in the form of a thermodynamic diagram (or contour diagram) (as shown in fig. 4), wherein the abscissa is VOn the ordinate of
Figure DEST_PATH_IMAGE069
Where the value of each position in the graph isV、
Figure 238853DEST_PATH_IMAGE069
And combining the corresponding cost function values.
The cost function grid in the form of a thermodynamic diagram shown in fig. 4 has a plurality of local minima, where the real motion parameters are combined
Figure DEST_PATH_IMAGE070
Is present in the plurality of local minima. Performing curve fitting on the local minimum values to obtain a coupling parameter line, and further combining the coupling parameter line obtained by curve fitting with other parameter estimation algorithms to obtain the final coupling parameter line
Figure 369620DEST_PATH_IMAGE070
Is located. However, as shown in fig. 4, due to the complexity of the underwater acoustic environment and the radiation noise signal of the underwater acoustic target, the position of the local minimum value of the cost function often has the phenomena of fluctuation, drift and the like, so that the parameter coupling line obtained by fitting has a larger deviation from the parameter coupling line where the real motion parameter is located, thereby affecting the accuracy of the subsequent positioning of the underwater acoustic target.
Therefore, the method of the application improves the technical scheme of directly performing curve fitting on the local minimum value of the cost function, and the specific implementation thought of the method is as follows: firstly, a parameter coupling band is divided from a cost function grid through the step S4, and a cost function corresponding to a motion parameter combination in the parameter coupling band is small, so that the motion parameter combination can be used as an alternative motion parameter combination; further, generating a corresponding smoother candidate parameter coupling line for each group of candidate motion parameter combinations through step S5; and finally, calculating an integral value of the cost function along the direction of each candidate parameter coupling line through step S6, and selecting an optimal parameter coupling line as a theoretical value of the Doppler parameter coupling line.
In particular, step S4 is used to divide the parametric coupling bands, thereby determining alternative motion parameter combinations. Fig. 6 is a schematic diagram illustrating dividing a parametric coupling band from a cost function mesh according to an embodiment of the present application, and as shown in fig. 6, in some embodiments of the present application, a parametric coupling threshold may be determined in advance according to a numerical distribution of a cost function, and then all cost functions smaller than the parametric coupling threshold in the cost function mesh are determined
Figure DEST_PATH_IMAGE071
Corresponding cost function grid point
Figure DEST_PATH_IMAGE072
Divided into parametric coupling bands (i.e. the areas in the upper and lower dotted lines in fig. 6), and located at cost function grid points in the parametric coupling bands
Figure 570794DEST_PATH_IMAGE072
The combination of motion parameters of
Figure DEST_PATH_IMAGE073
I.e. as an alternative motion parameter combination, for generating a corresponding parametric coupling line in the following step S5.
Further, step S5 generates each set of motion parameter combinations by
Figure 232851DEST_PATH_IMAGE073
Corresponding parameter coupling line:
s51: constructing a calculation grid of parameter coupling line theoretical values based on motion parameters of underwater acoustic targets, wherein the speedVIs calculated in the range of
Figure 13725DEST_PATH_IMAGE022
The speed calculation step length is
Figure 733419DEST_PATH_IMAGE023
Distance of closest approach
Figure 839915DEST_PATH_IMAGE024
Is calculated in the range of
Figure 192530DEST_PATH_IMAGE025
The closest distance calculation step is
Figure 980358DEST_PATH_IMAGE026
；
S52: extracting any cost function grid point in the parameter coupling band
Figure 351296DEST_PATH_IMAGE027
The combination of motion parameters of (1)
Figure 628694DEST_PATH_IMAGE028
；
S53: for the said
Figure 452293DEST_PATH_IMAGE028
Traversing the computational grid to compute each computational grid point
Figure 43812DEST_PATH_IMAGE029
Of (2)
Figure 19989DEST_PATH_IMAGE030
Obtaining a reaction of
Figure 468288DEST_PATH_IMAGE031
A corresponding grid of computation results, wherein,
Figure 248025DEST_PATH_IMAGE032
to obtain the instantaneous frequency after Doppler-warping transform of the spectrum,
Figure 174393DEST_PATH_IMAGE033
at a calculation grid point
Figure 519924DEST_PATH_IMAGE034
In the specific form of
Figure 886927DEST_PATH_IMAGE035
Wherein the content of the first and second substances,
Figure 685118DEST_PATH_IMAGE036
is the center frequency of the line spectrum,
Figure 618439DEST_PATH_IMAGE037
to calculate grid points
Figure 818476DEST_PATH_IMAGE038
A combination of motion parameters of (c);
s54: from and to
Figure 608578DEST_PATH_IMAGE039
Extracting a plurality of local minimum value points from the corresponding calculation result grid, and generating and based on the local minimum value points
Figure 97328DEST_PATH_IMAGE040
Corresponding parameter coupling lines;
s55: repeating steps S52-S54 until all cost function grid points within the parametric coupling band are traversed.
FIG. 7 shows the implementation flow of step S5, according to a specific embodiment of the present application, in which, as shown in FIG. 7, a computational grid of theoretical values of the parametric coupling line is first constructed in step S5, and then two-layer nested traversal is used, in which the inner traversal is used to compute each set of candidate motion parameter combinations
Figure 381810DEST_PATH_IMAGE039
At all calculation grid points
Figure DEST_PATH_IMAGE074
Of
Figure DEST_PATH_IMAGE075
Partial derivative with respect to time (in
Figure DEST_PATH_IMAGE076
Time of day) and generating a grid of computation results; external traversal for motion parameter combinations for each set of alternatives
Figure 498671DEST_PATH_IMAGE039
And fitting to obtain a corresponding parameter coupling line based on a plurality of local minimum value points in the calculation result grid.
Wherein
Figure 210406DEST_PATH_IMAGE075
For the instantaneous frequency after Doppler-warping transform of the spectrum, the following pairs
Figure 717610DEST_PATH_IMAGE075
Is detailed and describes the use thereof to generate alternative combinations of motion parameters
Figure 992734DEST_PATH_IMAGE039
The corresponding parameters couple the principles of the lines.
Setting the instantaneous frequency of the original line spectrum containing the Doppler shift to
Figure DEST_PATH_IMAGE077
The true recent arrival time of the underwater acoustic target is
Figure DEST_PATH_IMAGE078
For true motion parameters
Figure DEST_PATH_IMAGE079
The Doppler-warping operator
Figure DEST_PATH_IMAGE080
Substituting the expression for instantaneous frequency yields:
Figure DEST_PATH_IMAGE081
(4)
the above formula (4) is the original line spectrum
Figure DEST_PATH_IMAGE082
The instantaneous frequency expression after Doppler-warping conversion can be obtained by the formula
Figure DEST_PATH_IMAGE083
Namely: when Doppler-warping transformation is performed with correct motion parameters, the instantaneous frequency will recover the single frequency again.
In addition, the line spectrum of the original signal
Figure 573888DEST_PATH_IMAGE082
The time derivative yields:
Figure DEST_PATH_IMAGE084
(5)
as can be seen from the formula (5), in
Figure DEST_PATH_IMAGE085
The instantaneous frequency corresponds to the derivative value being maximum, i.e.: instantaneous frequency from Doppler-warping transform using correct motion parameters
Figure DEST_PATH_IMAGE086
The derivative of (A) is 0, corresponding to being in
Figure DEST_PATH_IMAGE087
The frequency change rate of the line spectrum after the time Doppler-warping conversion is 0, namely the frequency is a constant. Thus, equation (4) is derived over time and taken into
Figure DEST_PATH_IMAGE088
To give formula (6):
Figure DEST_PATH_IMAGE089
(6)
according to the above analysis, there should be true values of the motion parameters
Figure DEST_PATH_IMAGE090
Therefore, it should correspond to the parameter coupling line
Figure DEST_PATH_IMAGE091
The parametric coupling line direction is the direction in which the change of the directional derivative is the minimum, and corresponds to a plurality of local minimum positions in equation (6).
Above to instantaneous frequency
Figure DEST_PATH_IMAGE092
The Doppler-warping transformation and the method bring correct motion parameters and obtain the time derivative of the motion parameters
Figure DEST_PATH_IMAGE093
The physical meaning of the values in the points is explained in detail. In embodiments of the present application, in particular, for each set of alternative combinations of motion parameters
Figure DEST_PATH_IMAGE094
Substituting it into equation (4) and replacing the true motion parameter combination
Figure DEST_PATH_IMAGE095
Thereby obtaining:
Figure 938748DEST_PATH_IMAGE044
further will be
Figure DEST_PATH_IMAGE096
Derives the time and calculates it at
Figure DEST_PATH_IMAGE097
Time of day and calculation grid point
Figure DEST_PATH_IMAGE098
The value of (A) is obtained:
Figure DEST_PATH_IMAGE099
fig. 8A to 8C show thermodynamic diagrams of the calculation result grids obtained by step S53 for a plurality of candidate sets of motion parameter combinations, and as can be seen from fig. 8A to 8C, for any one of the candidate sets of motion parameter combinations, there is a thin strip covering the local minimum point, and the distribution of the local minimum point is obviously smoother than the local minimum point in the cost function grid. Fig. 9 shows a plurality of parametric coupling lines generated from local minimum point fitting of each of the computation result grids of fig. 8A to 8C.
In addition, in order to accelerate the determination of the parametric coupling band and increase the fitting accuracy of the parametric coupling line, in some preferred embodiments of the present application,
Figure DEST_PATH_IMAGE100
in which
Figure DEST_PATH_IMAGE101
Are all positive integers. According to the method provided by the application, the implementation mode that the local minimum value of the cost function grid generated by directly searching the grid is fitted with the parameter coupling curve is changed, so that the grid density of the searching grid can be properly reduced, the parameter coupling band can be determined as soon as possible in the steps S3 and S4, and the density of the calculating grid can be properly improved, so that the precision of the parameter coupling line fitted in the step S5 is ensured.
The combination of motion parameters with each candidate is obtained by step S5
Figure DEST_PATH_IMAGE102
After the corresponding parameter coupling lines, in S6, each parameter coupling line generated in step S5 is sequentially brought into the cost function grid and integrated along the direction of each parameter coupling line, and the parameter coupling line with the minimum integral value is determined as the theoretical value of the doppler parameter coupling line. Fig. 10 shows doppler parameter coupling lines (black solid lines in the figure) superimposed and displayed on a cost function grid thermodynamic diagram according to an embodiment of the present application, and it can be seen from fig. 10 that the doppler parameter coupling line theoretical values obtained by using the method provided by the present application significantly improve the curve accuracy and the smoothness, thereby ensuring that the curve accuracy and the smoothness are ensured The accuracy of subsequent underwater sound target positioning is improved.
Example 1
In the embodiment, simulation data are used, the sound velocity is 1500m/s, the center frequency of a simulation signal is 400Hz, the moving speed of a sound source is 5m/s, the nearest passing distance is 900m, the signal duration is 100s, and fig. 11 is a signal spectrogram, and it can be seen that a phenomenon of spectrum broadening caused by doppler is obvious at 400 Hz. First, the nearest arrival point time of the sound source is obtained
Figure DEST_PATH_IMAGE103
And setting Doppler-warping search grid for time domain signal obtained by simulation
Figure DEST_PATH_IMAGE104
Then, Doppler-warping transform is performed on the simulation signal, a search grid is traversed to obtain a cost function grid (a thermodynamic diagram of the cost function grid is shown in fig. 4), a parameter coupling threshold is set to be 0.1 according to a distribution situation of the cost function values at each search grid point, and grid points corresponding to the values smaller than 0.1 are divided into parameter coupling bands (regions between upper and lower dotted lines in fig. 4).
Next, all motion parameter combinations in the parametric coupling band are generated through step S5
Figure DEST_PATH_IMAGE105
Corresponding parameter coupling line, wherein the calculation grid of theoretical values of the parameter coupling line is
Figure DEST_PATH_IMAGE106
And (4) coupling the parameters into the band to obtain a plurality of theoretical calculation results of the coupling curve.
And finally, bringing each parameter coupling line back into a cost function grid, integrating along the direction of the parameter coupling line, wherein the parameter coupling line corresponding to the minimum value of the integral is the theoretical value of the Doppler parameter coupling line. Fig. 12 shows theoretical values of doppler parametric coupling lines superimposed on a thermodynamic diagram of a cost function grid, which can be seen to conform to the overall trend of variation of the coupling band. Fig. 13 shows the theoretical value of the doppler parameter coupling line and the position (triangular star in the figure) of the real motion parameter of the sound source, and it can be seen from fig. 13 that the theoretical value of the doppler parameter coupling line extracted by the method passes through the position of the real motion parameter, thereby proving the accuracy of extracting the parameter coupling line by the method of the present application.
Example 2
This example uses measured data from a marine experiment. In the experiment, a towed sound source is adopted to transmit 50Hz-400Hz single-frequency and frequency-modulated signals, and two horizontal arrays, a vertical array and an inclined array which are arranged on the seabed are adopted to receive the signals. The experiments were divided into two groups S5 and S59. In this embodiment, an S5 experiment is adopted, and the 13 th array element in the vertical array is selected for analysis.
Specifically, in the embodiment, a 385Hz line spectrum emitted by a shallow water towing sound source in an S5 experiment is selected, signals are selected from 3400S-3700S, the total time duration is 300S, the time of reaching the closest point is 3540S, the ship speed of the S5 experiment is 5 knots (2.5m/S), and the distance between the vertical array and the closest point of the motion track of the sound source is 903 m. The signal spectrum diagram is shown in fig. 2, and it can be seen from the spectrum diagram that a single-frequency signal has a significant band broadening due to doppler shift. First, the nearest arrival point time of the sound source is obtained
Figure DEST_PATH_IMAGE107
Setting a Doppler-warping search grid
Figure DEST_PATH_IMAGE108
And obtaining the average sound velocity of the water body through actual measurementc=1490 m/s. Then, Doppler-forwarding transformation is performed on the signal, a search grid is traversed to obtain a cost function grid (a thermodynamic diagram of the cost function grid is shown in fig. 14), a parameter coupling threshold value is set to be 0.1 according to the distribution situation of the cost function values at each search grid point, and the grid point corresponding to the value less than 0.1 is divided into parameter coupling bands (regions between upper and lower dotted lines in fig. 14).
Next, all motion parameter combinations in the parametric coupling band are generated through step S5
Figure DEST_PATH_IMAGE109
Corresponding parameter coupling line, wherein the calculation grid of theoretical values of the parameter coupling line is
Figure DEST_PATH_IMAGE110
And (4) coupling the parameters into the band to obtain a plurality of theoretical calculation results of the coupling curve.
And finally, bringing each parameter coupling line back into a cost function grid, integrating along the direction of the parameter coupling line, wherein the parameter coupling line corresponding to the minimum integral value is the theoretical value of the Doppler parameter coupling line. Fig. 15 shows the theoretical value of the doppler parameter coupling line and the position (triangular star in the figure) of the real motion parameter of the sound source, and the speed value at the position 903m closest to the real distance in the parameter coupling curve is taken to be 2.51m/s, which is basically consistent with the real speed value.
While the foregoing has described the detailed description of the embodiments of the present application, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the principles of the application, and it is intended to cover all such changes and modifications as fall within the scope of the appended claims.

Claims (7)

1. A Doppler parameter coupling line extraction method is used for obtaining the theoretical value of a Doppler parameter coupling line of an underwater sound target and is characterized by comprising the following steps:
S1: extracting a line spectrum with Doppler frequency shift from a time spectrum of radiation noise of the underwater sound target, and determining the nearest arrival time of the underwater sound target based on the line spectrum
Figure 391598DEST_PATH_IMAGE001
Wherein the time-frequency spectrum is determined based on an original signal of the underwater acoustic target radiation noise;
s2: constructing a search grid based on motion parameters of an underwater acoustic target, wherein the motion parameters include a velocity of the underwater acoustic targetVAnd the nearest distance
Figure 839897DEST_PATH_IMAGE002
Speed, velocityVIn a search range of
Figure 26159DEST_PATH_IMAGE003
The step size of speed search is
Figure 952526DEST_PATH_IMAGE004
Distance of closest approach
Figure 422691DEST_PATH_IMAGE002
In a search range of
Figure 917257DEST_PATH_IMAGE005
The nearest distance search step is
Figure 449870DEST_PATH_IMAGE006
；
S3: traversing the search grid to calculate each search grid point
Figure 179928DEST_PATH_IMAGE007
The combination of motion parameters of
Figure 6064DEST_PATH_IMAGE008
Corresponding cost function
Figure 530586DEST_PATH_IMAGE009
Obtaining a cost function grid, wherein the cost function
Figure 425861DEST_PATH_IMAGE009
The method comprises the steps of calculating spectrum entropy after resampling the original signal;
s4: extracting all cost functions smaller than parameter coupling threshold value from the cost function grid
Figure 694031DEST_PATH_IMAGE010
Corresponding cost function grid point
Figure 873209DEST_PATH_IMAGE011
Obtaining a parameter coupling band;
S5: sequentially generating each cost function grid point in parameter coupling band
Figure 568632DEST_PATH_IMAGE011
The combination of motion parameters of
Figure 341416DEST_PATH_IMAGE012
Corresponding parameter coupling lines;
s6: and (4) sequentially substituting each parameter coupling line generated in the step (S5) into the cost function grid, integrating along the direction of each parameter coupling line, and determining the parameter coupling line with the minimum integral value as the theoretical value of the Doppler parameter coupling line.
2. The doppler parameter coupled line extraction method according to claim 1, wherein the step S3 comprises the following steps:
s31: extracting any search grid point
Figure 757485DEST_PATH_IMAGE013
Using combinations of motion parameters including at the search grid point
Figure 932115DEST_PATH_IMAGE014
Doppler-warping operator of
Figure 532860DEST_PATH_IMAGE015
Resampling original signals of underwater sound target radiation noise to obtain resampled signals
Figure 416109DEST_PATH_IMAGE016
Wherein, in the step (A),
Figure 26082DEST_PATH_IMAGE017
，cis the speed of sound in water;
s32: the calculation is combined with the motion parameters at that point
Figure 930584DEST_PATH_IMAGE014
Corresponding cost function
Figure 967811DEST_PATH_IMAGE018
，
Wherein the content of the first and second substances,
Figure 574241DEST_PATH_IMAGE019
in order to integrate the upper and lower limits,
Figure 722326DEST_PATH_IMAGE020
is that it is
Figure 605968DEST_PATH_IMAGE016
In the form of
Figure 955041DEST_PATH_IMAGE021
；
S33: and repeating the steps S31 and S32 until the search grid is traversed to obtain a cost function grid.
3. The method of claim 2, wherein the Doppler parameter coupling line extraction method comprises:
upper and lower limits of the integral
Figure 658555DEST_PATH_IMAGE019
And determining according to the Doppler frequency broadening situation of the line spectrum.
4. The method of claim 1, wherein the Doppler parameter coupling line extraction method comprises:
the parameter coupling threshold is determined based on a numerical distribution range of the cost function.
5. The doppler parameter coupled line extraction method of claim 1, wherein the step S5 comprises the steps of:
S51: constructing a calculation grid of parameter coupling line theoretical values based on motion parameters of underwater acoustic targets, wherein the speedVIs calculated in the range of
Figure 236429DEST_PATH_IMAGE022
The speed calculation step is
Figure 974578DEST_PATH_IMAGE023
Distance of closest approach
Figure 619186DEST_PATH_IMAGE024
Is calculated in the range of
Figure 685362DEST_PATH_IMAGE025
The closest distance calculation step is
Figure 440828DEST_PATH_IMAGE026
；
S52: extracting any cost function grid point in the parameter coupling band
Figure 158117DEST_PATH_IMAGE027
The combination of motion parameters of
Figure 708048DEST_PATH_IMAGE028
；
S53: for the said
Figure 651733DEST_PATH_IMAGE028
Traversing the computational grid to compute each computational grid point
Figure 820677DEST_PATH_IMAGE029
Of
Figure 533418DEST_PATH_IMAGE030
Obtaining a reaction of
Figure 988670DEST_PATH_IMAGE031
A corresponding grid of computation results, wherein,
Figure 42821DEST_PATH_IMAGE032
to obtain the instantaneous frequency after Doppler-warping transform of the spectrum,
Figure 140090DEST_PATH_IMAGE033
at calculation grid point
Figure 582703DEST_PATH_IMAGE034
In the specific form of
Figure 474436DEST_PATH_IMAGE035
Wherein the content of the first and second substances,
Figure 127134DEST_PATH_IMAGE036
is the center frequency of the line spectrum,
Figure 152728DEST_PATH_IMAGE037
to calculate grid points
Figure 308903DEST_PATH_IMAGE038
A combination of motion parameters of (c);
s54: from and to
Figure 512482DEST_PATH_IMAGE039
Extracting a plurality of local minimum value points from the corresponding calculation result grid, and generating and based on the local minimum value points
Figure 652476DEST_PATH_IMAGE040
Corresponding parameter coupling lines;
s55: repeating steps S52-S54 until all cost function grid points within the parametric coupling band are traversed.
6. The Doppler parameter coupled line extraction method according to claim 5, wherein:
Figure 91548DEST_PATH_IMAGE041
wherein
Figure 259486DEST_PATH_IMAGE042
Are all positive integers.
7. The Doppler parameter coupling line extraction method according to claim 5, wherein the Doppler parameter coupling line extraction method is characterized in that
Figure 493022DEST_PATH_IMAGE043
The concrete form of (A) is as follows:
Figure 995678DEST_PATH_IMAGE044
。
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