A method for adaptive target velocity measurement and absolute bearing estimation of a proactive sonar

Abstract

The application discloses a kind of active sonar adaptive target velocity measurement and absolute position estimation method, adopt active sonar transmission waveform as the combined signal of wideband+single frequency, reverberation ellipse fitting is carried out through the reverberation data of single frequency signal, and then the estimated value of ship speed and array deflection angle is calculated, simultaneously determine Doppler filtering range, target position is obtained by wideband signal decision result, and its index single frequency signal processing result corresponding position is filtered to measure speed, obtain target relative radial velocity, finally, the relative distance and angle of wideband signal judgment, ship GPS information, the absolute position of target is calculated by the modified array deflection angle.It is verified by sea trial data that the application can solve the problem that single frequency reverberation filtering range is difficult to determine and absolute position is difficult to calculate under the condition of missing array deflection angle information, realize the effective acquisition of target absolute position and relative radial velocity under the detection mode of wideband+single frequency combined wave signal.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustic signal processing, and in particular to an active sonar adaptive target velocity measurement and absolute azimuth estimation method. Background Technology

[0002] Active sonar can estimate multiple parameters of a target, including angle, range, and velocity, by emitting a combination of broadband and single-frequency signals and processing the echo signals. Broadband signals have a shorter reverberation duration and possess high range resolution and Doppler invariance; high-gain processing of broadband signals can yield angle-range information. Single-frequency signals have high processing gain and Doppler sensitivity, allowing the acquisition of target velocity information.

[0003] However, in practical sonar detection systems, the discrepancy between the direction of the listening ship's movement and the ocean current direction leads to array deflection, making it impossible to calculate the target's absolute bearing from the relative angular distance. Furthermore, due to the long reverberation duration of single-frequency signals, if the target is located within the reverberation zone, velocity measurement will be affected by reverberation interference, making it difficult to accurately obtain the target's velocity. Therefore, reverberation data preprocessing is necessary. Many scholars have studied and analyzed these issues. Sun et al. proposed that when the sonar operates in active mode and transmits a single-frequency pulse signal, the reverberation data contains array deflection information (Wei S, Fangyong W. Estimation of Towed-array heading using reverberation data [C] / / 2021 IEEE International Conference on Signal Processing, Communications and Computing. Xi'an, China, 2021:14.), but they did not conduct in-depth research on how to obtain this array deflection information. Li Yuqiang et al. used the space-time adaptive processing (STAP) method to suppress reverberation (Li Yuqiang, Li Yuwei, Jiang Xiaoyong. Research on key technologies of active sonar anti-reverberation space-time adaptive processing [J]. Ship Electronic Engineering, 2022, 2(11): 177-180.). However, on the one hand, due to the non-stationarity of shallow sea reverberation, the covariance matrix is ​​prone to being less than rank, and the algorithm has stability and robustness problems. On the other hand, the algorithm does not analyze the relationship between the reverberation center frequency and the angle, but filters the whole, and the target echo may also be weakened.

[0004] In summary, during the processing of broadband and single-frequency combined sonar waves, the presence of array deflection and the long reverberation duration of single-frequency signals during actual detection make it difficult to calculate the absolute orientation of the target and obtain the relative radial velocity of the target. Existing solutions are all unable to reliably estimate multiple parameters of the target, including angle, distance, and velocity. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an active sonar adaptive target velocity measurement and absolute azimuth estimation method to address the shortcomings of the existing technology and achieve accurate estimation of the reverberation frequency.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an active sonar adaptive target velocity measurement and absolute azimuth estimation method, comprising the following steps:

[0007] S1. Acquire reverberant acoustic sampling data uploaded by the hydrophone, perform narrowband beamforming on the array data to obtain the reverberant spatial frequency characteristic spectrum S(θ,f), reduce the dimensionality of the reverberant spatial frequency characteristic spectrum S(θ,f) to obtain the reverberant spatial characteristic spectrum S1(θ), filter out interference from the reverberant spatial characteristic spectrum S1(θ), and convert the frequency of the reverberant spatial characteristic spectrum S1(θ) into frequency offset to obtain the filtered reverberant spatial characteristic spectrum S2(θ); θ is the scanning angle, and f is the frequency of the acoustic sampling data;

[0008] S2. Perform elliptic fitting on the filtered reverberation spatial characteristic spectrum S2(θ) to obtain the elliptic equation f1(x,y)=0, where x is the cosine of the scanning angle and y is the frequency offset; calculate the ship speed v based on the parameters of the elliptic equation f1(x,y)=0. ship The array deflection angle α is obtained, and the corrected array deflection angle α1 is obtained from the ocean current direction. The length of the major axis of the ellipse equation f1(x,y)=0 is obtained. The major axis is scaled and transformed to obtain the ellipse f2(x,y)=0 whose semi-major axis length is projected as 1 on the x-axis. The Doppler filtering range h(θ) is determined.

[0009] S3. Perform CFAR decision on the normalized space-time energy spectrum L(θ,d) of the broadband signal to obtain the target azimuth θ0 and range d0, and calculate the spectrum S of the single-frequency signal at the azimuth θ0 and range d0 positions. target (θ0,f); the spectrum S is obtained by the Doppler filtering range h(θ). target The relative radial velocity v0 of the target is obtained by filtering (θ0,f);

[0010] S4. Based on the target bearing θ0 and distance d0, the ship's GPS information, the corrected array deflection α1, and the ship's speed and direction α. vThe absolute coordinates of the target are calculated, that is, the latitude and longitude coordinates (Lon1, Lat1) when the target is on the port side or the latitude and longitude coordinates (Lon2, Lat2) when the target is on the starboard side.

[0011] The formula for calculating the Doppler filtering range h(θ) is:

[0012] h(θ)=[f1(θ)+f0-B0,f1(θ)+f0+B0]∪[f2(θ)+f0-B0,f2(θ)+f0+B0];

[0013] Where f1(θ) and f2(θ) are the port and starboard reverberation center frequencies obtained from the coordinates of the ellipse f2(x,y)=0, respectively, and B0 is the filter bandwidth.

[0014] The formula for calculating the target's relative radial velocity v0 is:

[0015]

[0016] in, h(θ0) is the Doppler filtering range of the target's angle, and c is the underwater sound speed.

[0017] The formula for calculating the spatial frequency characteristic spectrum S(θ,f) of reverberation data is: S(θ,f)=Beamform cw (X);

[0018] Beamform CW Narrowband beamforming representing a single-frequency signal, where X represents M′N T Reverberation data for a Wikipedia array, where M is the number of array elements and N is the number of elements. T It is the number of sampling points with the same duration as the CW signal.

[0019] The formula for calculating the filtered reverberation spatial characteristic spectrum S2(θ) is as follows:

[0020]

[0021] f t The threshold is [ ], which indicates the deletion of the corresponding data point. f0 is the transmitted wave frequency. Detrend[S1(θ)-f0] is the least squares fitted line removed from the S1(θ)-f0 data. The expression of the least squares fitted line is:

[0022] y = k s x+b s ;

[0023] x is the cosine of the scanning angle, y is the frequency offset, and the slope k is the slope. s and constant term b s We obtain it from the following formula:

[0024]

[0025] Where, x i =cos(θ) i ), θ i =kΔθ, k = 0, 1, 2...N, where N is the total number of scanning angles. Δθ is the scanning angle interval, S1(θ) i ) is θ=θ i The value of the spatial characteristic spectrum of reverberation.

[0026] own ship speed v ship The formulas for calculating the array deflection angle α and the corrected array deflection angle α1 are as follows:

[0027]

[0028] Among them, v 洋流 The velocity of the ocean current is positive if the velocity component along the ship's transverse direction is to the starboard side, and negative otherwise. A, C, and D are the coefficients of the ellipse equation f1(x,y)=0.

[0029] The formulas for calculating the target azimuth θ0 and distance d0 are: (θ0,d0)=CFAR[L(θ,d)];

[0030] The formula for calculating the absolute coordinates (Lon1, Lat1) or (Lon2, Lat2) of the target is as follows:

[0031]

[0032] Where R is the Earth's radius.

[0033] As an inventive concept, the present invention also provides an active sonar adaptive target velocity measurement and absolute orientation estimation system, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the steps of the above method.

[0034] Compared with existing technologies, the advantages of this invention are as follows: This invention fully utilizes the reverberation center frequency information of a single-frequency signal, and obtains ship speed and array deflection information through reverberation expression analysis, thereby more accurately obtaining the Doppler filtering range. Compared with traditional space-time adaptive processing methods, it can achieve accurate estimation of reverberation frequency points, accurate filtering of target echo spectra, and estimation of target relative radial velocity. Simultaneously, since the array deflection information has been obtained through reverberation information, the absolute bearing of the target can be calculated based on the decision results of the normalized space-time energy spectrum of the broadband signal, combined with ship speed, ship GPS information, etc., which is more accurate than traditional relative coordinate system positioning. Attached Figure Description

[0035] Figure 1This is a flowchart of the adaptive target velocity measurement and absolute orientation estimation method according to an embodiment of the present invention;

[0036] Figures 2(a) to 2(e) This is a diagram showing the fitting effect of single-frequency signal reverberation data in an embodiment of the present invention;

[0037] Figures 3(a) and 3(b) are diagrams showing the single-frequency signal target spectrum filtering effect of an embodiment of the present invention;

[0038] Figure 4 This is a diagram illustrating the broadband signal absolute azimuth estimation effect of an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] Embodiment 1 of this invention provides an active sonar adaptive target velocity measurement and absolute azimuth estimation method, the framework of which is as follows: Figure 1 As shown, the invention includes a single-frequency signal reverberation data fitting module, a broadband signal normalized space-time energy spectrum decision module, an absolute bearing estimation module, and a Doppler filter frequency-locked velocity measurement module. By fitting a reverberation ellipse to the reverberation data of the single-frequency signal, estimated values ​​of ship speed and array deflection are obtained, and the Doppler filtering range is determined. Then, the target bearing is indexed from the broadband signal decision result to the corresponding position in the single-frequency signal processing result for filtered velocity measurement, yielding the target's relative radial velocity. Finally, the target's absolute bearing is calculated using the relative distance and angle determined by the broadband signal, the ship's GPS information, and the corrected array deflection. Sea trial data verification shows that this invention can solve the problems of difficulty in determining the reverberation filtering range of single-frequency signals and difficulty in calculating absolute bearing, achieving effective acquisition of the target's absolute bearing and relative radial velocity under a broadband + single-frequency combined wave signal detection mode.

[0042] The following section uses a segment of towed linear array sonar sea trial data as an example to introduce the main processing flow of the algorithm. The specific process is as follows:

[0043] Step 1: Let X represent M′N T Reverberation data of a Wikipedia array, where M is the number of array elements and N is the number of elements. T It is the number of sampling points with the same duration as the CW signal, Beamform CW Narrowband beamforming representing a single-frequency signal, the spatial frequency characteristic spectrum S(θ,f) of this frame of reverberation data is expressed as:

[0044] S(θ,f)=Beamform cw (X) (1)

[0045] Where θ is the scanning angle. Where Δθ is the scanning angle interval, f0 is the transmitted wave frequency, and f0-f e £f£f0+f e This means that the maximum frequency shift that can be processed is f. e The signal is given by f based on empirical values ​​in this data. e =5.

[0046] Step 2: Select the spatial frequency characteristic spectrum S(θ,f) and extract the reverberation frequency features. Since the reverberation energy is generally higher than noise and other interference, it is assumed that the frequency with the highest energy at each angle is the center frequency of the reverberation, thus obtaining the reverberation spatial characteristic spectrum S1(θ). This process is expressed as follows:

[0047]

[0048] in, This represents the position of f when S(θ,f) reaches its maximum value.

[0049] Step 3: Select the reverberation spatial characteristic spectrum S1(θ), perform frequency shifting on it, and apply amplitude limiting filtering to obtain the filtered reverberation spatial characteristic spectrum S2(θ). The expression for the reverberation frequency shift as a function of the cosine value of the scanning angle is shown below.

[0050]

[0051] in, v ship Let α be the ship's speed and α be the array deflection angle.

[0052] Because the reverberation ellipse is an oblique ellipse when the launch vessel is in motion, it is necessary to remove the best-fit line from the data and then perform amplitude-limiting filtering. This process is represented as follows:

[0053]

[0054] Where Detrend[S1(θ)-f0] is the least squares fitted line removed from the S1(θ)-f0 data, and the expression of the least squares fitted line is:

[0055] y = k s x+b s (5)

[0056] x is the cosine of the scanning angle, y is the frequency offset, and the slope k is the slope. s and constant term b s We obtain it from the following formula:

[0057]

[0058] x i =cos(θ) i ), θ i =kΔθ, k = 0, 1, 2...N, where N is the total number of scanning angles. Δθ is the scanning angle interval, S1(θ) i ) is θ=θ i The value of the spatial characteristic spectrum of reverberation.

[0059] Step 4: Let the equation of the reverberation ellipse be Ax 2 +Bxy+Cy 2 +D=0, then the fitting of the elliptic coefficient matrix can be expressed as

[0060] a = fitellipse[S2(θ)] (7)

[0061] Where fitellipse represents reverberation ellipse fitting, and 'a' is the ellipse coefficient matrix, a = [A, B, C, D] T Since fitting the elliptic coefficient matrix solely using the least squares method may result in fitting other conic sections, elliptic constraints need to be added. The optimization model can be expressed as follows:

[0062]

[0063] in

[0064] Step 5: The ship speed and array deflection angle can be calculated based on the reverberation ellipse parameters. The calculation formula is as follows:

[0065]

[0066] Among them, v 洋流 The velocity is the ocean current. The velocity component of the ocean current along the ship's transverse direction is positive if it is in the starboard direction, and negative otherwise.

[0067] Step Six: Since the abscissa range of the fitted reverberation ellipse may be less than [-1, 1], making it difficult to determine the Doppler filtering range in the end-shot direction, a scaling transformation of the ellipse is required. Construct a symmetric matrix of ellipse coefficients.

[0068]

[0069] Orthogonalize the elliptic coefficient matrix E1 to E1 = QΛ1Q T The eigenvalues ​​and eigenvectors corresponding to the major axis are obtained as λ. l u l =(x l ,yl The length of the semi-major axis L1 and the corresponding eigenvalue λ of the major axis after ellipse scaling can be calculated. l1 for

[0070]

[0071] The symmetric matrix of the elliptic coefficients after scaling can be obtained as E2=QΛ2Q T Where Λ2 is the eigenvalue matrix of the ellipse after scaling, and the coefficient matrix a of the scaled ellipse can be obtained from E2. l =[A l B l C l D l ] T .

[0072] Step 7: Since reverberation has a certain broadening in the frequency spectrum, the filter bandwidth B0 needs to be set, and the Doppler filter range h(θ) can be obtained as follows:

[0073] h(θ)=[f1(θ)+f0-B0,f1(θ)+f0+B0]∪[f2(θ)+f0-B0,f2(θ)+f0+B0] (12)

[0074] Where f1(θ) and f2(θ) are the ellipse ordinate values ​​corresponding to θ, and are the port and starboard reverberation center frequencies obtained from the ellipse coordinates, respectively.

[0075] Step 8: CFAR decision is performed using the normalized space-time energy spectrum L(θ,d) of the broadband signal to obtain the target azimuth θ0 and range d0. This process is expressed as follows:

[0076] (θ0,d0)=CFAR[L(θ,d)] (13)

[0077] Step 9: Calculate the spectrum S at the corresponding location obtained from single-frequency signal processing using the azimuth θ0 and distance d0 obtained from broadband signal processing. target (θ0,f), and then filter and lock the frequency using the Doppler filtering range h(θ) obtained in step seven, and measure the velocity. The formula for calculating the target's relative radial velocity v0 is as follows:

[0078]

[0079] in, h(θ0) is the Doppler filter range of the target's angle.

[0080] Step 10: The direction of the ship's speed is α v Given that the array tilt angle correction value is α1 and the ship's GPS coordinates are (Lon0, Lat0), then the target's absolute coordinates (Lon1, Lat1) or (Lon2, Lat2) are:

[0081]

[0082] Where R is the Earth's radius, and (Lon1,Lat1) and (Lon2,Lat2) correspond to the latitude and longitude coordinates of the target when it is on the port or starboard side, respectively.

[0083] Figures 2(a) to 2(e) Figure 2(a) shows the fitting effect of reverberation data for a single-frequency signal. In this processing, the reverberation calculation frequency offset range was selected as ±5Hz, and the resulting spatial frequency characteristic spectrum is shown in Figure 2(a). The spatial frequency characteristic spectrum was reduced to obtain the reverberation spatial characteristic spectrum, as shown in Figure 2(b). It can be seen that there are many interferences in the reverberation spatial characteristic spectrum, which will affect the data fitting effect. Therefore, the reverberation spatial characteristic spectrum after shifting and amplitude limiting filtering was obtained, as shown in Figure 2(c). Finally, the data was fitted by the fitting algorithm, as shown in Figure 2(d). The fitting effect basically met the expectations. At the same time, the ship speed v0 = 1.61m / s and the array deflection angle α0 = 16.43° can be calculated by formula (6), which is in good agreement with the actual parameters. Figure 2(e) shows the ellipse scaling result. There are two ellipses in the figure, namely the ellipse before scaling and the ellipse after scaling. The ellipse after scaling is used to determine the center frequency of the Doppler filter.

[0084] Figures 3(a) and 3(b) show the effect of single-frequency signal target spectrum filtering. Figure 3(a) is the spectrum diagram of the target location, and Figure 3(b) is the spectrum diagram after filtering. As can be seen from the figures, the filtering method provided by the present invention can effectively filter out the reverberation spectrum, making the spectrum line of the target prominent. Thus, the relative radial velocity of the velocity target is 2.31 m / s, which is in good agreement with the actual parameters.

[0085] Figure 4 The figure shows the effect of broadband signal absolute bearing estimation. As can be seen from the figure, there is less interference in the normalized space-time energy spectrum, and the target can be correctly identified. In the experiment, a transponder was used to simulate the target echo, with a transponder delay of 40s, therefore the target bearing was 33.9km, 69.5°. In the experiment, the GPS coordinates of the transmitting ship were (109.9774, 17.7150), the ship's speed direction was 161° (east of north), and the corrected array deflection angle was 16.43°, yielding the target absolute bearing as (109.8517, 17.4339) or (109.8787, 18.0057). The actual target was located near (109.8787, 18.0057), therefore the result basically meets expectations.

[0086] In summary, this invention utilizes the characteristics of broadband and single-frequency signals. It fits a reverberation ellipse using reverberation data from a single-frequency signal, simultaneously calculating ship speed and array deflection. The broadband signal acquires the target's relative distance and angle. The corresponding position spectrum of the single-frequency signal is filtered for velocity measurement. Finally, combining the reverberation fitting parameters of the single-frequency signal with the transmitter's GPS coordinates and heading, the target's absolute bearing and relative radial velocity are calculated. This effectively solves the problems of determining the reverberation filtering range and calculating the absolute bearing of single-frequency signals, achieving effective acquisition of the target's absolute bearing and relative radial velocity under a broadband + single-frequency combined wave signal detection mode.

[0087] Example 2

[0088] Embodiment 2 of the present invention provides a system corresponding to Embodiment 1 above. The terminal device can be a processing device for a client, such as a mobile phone, a laptop, a tablet computer, a desktop computer, etc., to execute the method of the above embodiments.

[0089] The system of this embodiment includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method of Embodiment 1 described above.

[0090] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0091] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0092] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0093] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. An active sonar adaptive target velocity measurement and absolute azimuth estimation method, characterized in that, Includes the following steps: S1. Acquire reverberant acoustic sampling data uploaded by the hydrophone, perform narrowband beamforming on the array data to obtain the reverberant spatial frequency characteristic spectrum S(θ,f), reduce the dimensionality of the reverberant spatial frequency characteristic spectrum S(θ,f) to obtain the reverberant spatial characteristic spectrum S1(θ), filter out interference from the reverberant spatial characteristic spectrum S1(θ), and convert the frequency of the reverberant spatial characteristic spectrum S1(θ) to frequency offset to obtain the filtered reverberant spatial characteristic spectrum S2(θ); θ is the scanning angle, and f is the frequency of the acoustic sampling data; S2. Perform elliptic fitting on the filtered reverberation spatial characteristic spectrum S2(θ) to obtain the elliptic equation f1(x,y)=0, where x is the cosine of the scanning angle and y is the frequency offset; calculate the ship speed v based on the parameters of the elliptic equation f1(x,y)=0. ship The array deflection angle α is obtained, and the corrected array deflection angle α1 is obtained from the ocean current direction. The length of the major axis of the ellipse equation f1(x,y)=0 is obtained. The major axis is scaled and transformed to obtain the ellipse f2(x,y)=0 whose semi-major axis length is projected as 1 on the x-axis. The Doppler filtering range h(θ) is determined. S3. Perform CFAR decision on the normalized space-time energy spectrum L(θ,d) of the broadband signal to obtain the target azimuth θ0 and range d0, and calculate the spectrum at the target azimuth θ0 and range d0. S target (θ0,f); the spectrum S is obtained by the Doppler filtering range h(θ). target The relative radial velocity v0 of the target is obtained by filtering (θ0,f); S4. Based on the target bearing θ0 and distance d0, the ship's GPS information, the corrected array deflection α1, and the ship's speed and direction α. v The absolute coordinates of the target are calculated, that is, the latitude and longitude coordinates (Lon1, Lat1) when the target is on the port side or the latitude and longitude coordinates (Lon2, Lat2) when the target is on the starboard side.

2. The active sonar adaptive target velocity measurement and absolute azimuth estimation method according to claim 1, characterized in that, The formula for calculating the Doppler filtering range h(θ) is: h(θ)=[f1(θ)+f0-B0,f1(θ)+f0+B0]∪[f2(θ)+f0-B0,f2(θ)+f0+B0]; Where f1(θ) and f2(θ) are the port and starboard reverberation center frequencies obtained from the coordinates of the ellipse f2(x,y)=0, respectively, B0 is the filter bandwidth, and f0 is the transmitted wave frequency.

3. The active sonar adaptive target velocity measurement and absolute azimuth estimation method according to claim 1, characterized in that, The formula for calculating the target's relative radial velocity v0 is: in, h(θ0) is the Doppler filtering range of the target's angle, and c is the underwater sound speed.

4. The active sonar adaptive target velocity measurement and absolute azimuth estimation method according to claim 1, characterized in that, The formula for calculating the spatial frequency characteristic spectrum S(θ,f) of reverberation data is: S(θ,f)=Beamform cw (X); Beamform CW Narrowband beamforming representing a single-frequency signal, where X represents M×N T Reverberation data for a Wikipedia array, where M is the number of array elements and N is the number of elements. T It is the number of sampling points with the same duration as the CW signal.

5. The active sonar adaptive target velocity measurement and absolute azimuth estimation method according to claim 1, characterized in that, The formula for calculating the filtered reverberation spatial characteristic spectrum S2(θ) is as follows: Among them, f t The threshold is [ ], which indicates the deletion of the corresponding data point. f0 is the transmitted wave frequency. Detrend[S1(θ)-f0] is the least squares fitted line removed from the S1(θ)-f0 data. The expression of the least squares fitted line is: y=k s x+b s ; slope k s and constant term b s We obtain it from the following formula: x i =cos(θ) i ), θ i =kΔθ, k = 0, 1, 2...N, where N is the total number of scanning angles. Δθ is the scanning angle interval, S1(θ) i ) is θ=θ i The value of the spatial characteristic spectrum of reverberation.

6. The active sonar adaptive target velocity measurement and absolute azimuth estimation method according to claim 1, characterized in that, own ship speed v ship The formulas for calculating the array deflection angle α and the corrected array deflection angle α1 are as follows: Among them, v 洋流 The velocity of the ocean current is positive if the velocity component along the ship's transverse direction is to the starboard side, and negative otherwise. A, C, and D are the coefficients of the ellipse equation f1(x,y)=0.

7. The active sonar adaptive target velocity measurement and absolute azimuth estimation method according to claim 1, characterized in that, The formulas for calculating the target azimuth θ0 and distance d0 are as follows: (θ0,d0)=CFAR[L(θ,d)].

8. The active sonar adaptive target velocity measurement and absolute azimuth estimation method according to any one of claims 1 to 7, characterized in that, The formula for calculating the absolute coordinates (Lon1, Lat1) or (Lon2, Lat2) of the target is as follows: Where R is the Earth's radius, and (Lon0,Lat0) are the ship's GPS coordinates.

9. An active sonar adaptive target velocity measurement and absolute azimuth estimation system, comprising a memory, a processor, and a computer program stored in the memory; characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 8.

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