A method for accurate underwater target orientation based on vector hydrophone array signal synthesis

Abstract

The present invention relates to the technical field of underwater acoustic signal processing, and provides a method for accurately directing underwater targets by synthesizing vector hydrophone array signals, comprising: obtaining vector hydrophone array signals of sound sources related to underwater targets; designing a conventional beamforming matrix; performing Kronecker product operations on the vector hydrophone array signals using the conventional beamforming matrix, thereby synthesizing the vector hydrophone array signals into new vector signals; and obtaining the azimuth information of underwater targets by using a single vector hydrophone directing method based on the new vector signals. The present invention synthesizes the vector hydrophone array signals into new vector signals by performing Kronecker product operations on the conventional beamforming matrix and the vector hydrophone array signals, and introduces spatial processing gain and array signal averaging operations, thereby improving the signal-to-noise ratio of the vector hydrophone array and the tolerance of array errors and array element errors.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater acoustic signal processing for ocean monitoring and underwater target detection, and in particular to an underwater target precise orientation method for vector hydrophone array signal synthesis, which is suitable for underwater sound source orientation of vector hydrophone array. Background Art

[0002] The continuous development of anechoic and stealth technology has made the sound source level of underwater targets smaller and smaller. The radiated noise of underwater targets is submerged in the background noise of the ocean, which makes it difficult to orient the sound source. Vector hydrophones can detect the low-frequency line spectrum of the radiated noise of underwater targets, maintain constant dipole directivity, high sensitivity and anti-isotropic interference capability in a wide frequency band. A single vector hydrophone can solve the target azimuth and pitch angle by performing simple calculations on its sound pressure signal and three vibration velocity components, and there is no left and right ambiguity problem inherent in underwater acoustic array direction finding, which is superior. However, it is still difficult to achieve superior estimation performance at low signal-to-noise ratios.

[0003] Regarding the research on vector hydrophone array signal processing, from the pioneering work of Professor Zhinovkin of Moscow University and American signal processing expert Aiye Nehorai to the present day, many achievements have been made. However, these array signal processing methods directly calculate and process the received signals of the vector hydrophone, which belongs to the array element domain processing method. The array element domain processing method does not utilize the spatial processing gain of array signal processing, has high requirements for signal-to-noise ratio, is sensitive to array errors, and its directional performance is limited. Vector hydrophone array beamforming is an important method for underwater target orientation, but the directional accuracy is limited. The directional error of the multi-beam system is half the beam width, which is a large error. The directional error of the single-beam scanning system is the scanning interval. To improve the accuracy, the scanning interval must be reduced, which will increase the amount of calculation and is difficult to meet the application requirements in practice.

[0004] It is of great significance to study the high-precision direction-directing method of vector hydrophone arrays which can be robust under low signal-to-noise ratio conditions. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a method for accurately directing underwater targets by synthesizing vector hydrophone array signals.

[0006] A method for accurately directing underwater targets by synthesizing vector hydrophone array signals, comprising: obtaining vector hydrophone array signals of sound sources related to underwater targets; designing a conventional beamforming matrix; performing Kronecker product operations on the vector hydrophone array signals using the conventional beamforming matrix, thereby synthesizing the vector hydrophone array signals into new vector signals; and obtaining the azimuth information of the underwater targets by using a single vector hydrophone directing method based on the new vector signals.

[0007] Further, the vector hydrophone array signal is configured as a 4M×1 vector, which includes the sound pressure signal and velocity component of each element in the vector hydrophone array; the conventional beamforming matrix is ​​configured as an M×1 vector, which includes the array coordinate information of each element of the vector hydrophone array, the azimuth index of the underwater target in the direction to be observed and the sidelobe level index in the non-observation direction; the new vector signal is configured as a 4×1 vector, which includes the sound pressure signal and velocity component obtained by analogy with a single vector hydrophone; wherein M represents the number of elements in the vector hydrophone array. Preferably, 3≤M≤7.

[0008] Optionally, the single-vector hydrophone directional method is a line spectrum analysis directional algorithm.

[0009] Preferably, before the signal synthesis, the vector hydrophone array signal is subjected to line spectrum capture processing, and the signal is captured and interference is suppressed by bandpass filtering.

[0010] Preferably, the method further comprises: removing outliers in the position information of the underwater target by using an average smoothing algorithm.

[0011] The features and advantages of the present disclosure include: the present invention synthesizes the vector hydrophone array signal into a new vector signal, that is, constructs a new single vector hydrophone, and then uses the single vector hydrophone directional method to solve the target angle for the new vector signal; the present invention synthesizes the vector hydrophone array signal into a new vector signal by performing a Kronecker product operation on a conventional beamforming matrix and a vector hydrophone array signal, introduces a spatial processing gain and an array signal averaging operation, thereby improving the signal-to-noise ratio of the vector hydrophone array and the tolerance to array errors and array element errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 The basic principle diagram of the present invention is shown;

[0014] Figure 2 A schematic diagram of the software flow of the present invention is shown;

[0015] Figure 3 The basic algorithm flow diagram of the present invention is shown;

[0016] Figure 4 A more detailed schematic diagram of the algorithm flow is shown. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0018] refer to Figures 1 to 4 The present invention provides a method for accurately locating underwater targets by synthesizing vector hydrophone array signals. For a given vector hydrophone array signal, it is synthesized into a new vector signal, that is, a new single vector hydrophone (new vector hydrophone) is constructed by the vector hydrophone array. The core step is the method for synthesizing vector hydrophone signals from vector hydrophone array signals, which performs a Kronecker product operation on a conventional beamforming matrix and the vector hydrophone array signal. The present invention provides a method for accurately locating underwater targets by synthesizing vector hydrophone array signals, including the steps of: obtaining a vector hydrophone array signal of a sound source related to an underwater target; designing a conventional beamforming matrix; performing a Kronecker product operation on the vector hydrophone array signal using the conventional beamforming matrix to synthesize the vector hydrophone array signal into a new vector signal; and accurately locating the new vector signal according to the single vector hydrophone orientation method.

[0019] Specifically, the vector hydrophone array signal can be obtained by using an experimental method to receive the sound source signal of the underwater target using a vector hydrophone array. Alternatively, the vector hydrophone array signal can be obtained by a simulation method. For example, the vector hydrophone array signal Can be expressed as a 4M×1 vector , where M represents the number of array elements (vector hydrophones) in the vector hydrophone array, and the sound pressure signal x of the M array elements is p (t) and the velocity components x of the M array elements vx (t), x vy (t), x vz (t) is expressed as

[0020]

[0021] In formula [1], p(r,t) represents the sound pressure signal of the first element in the vector hydrophone array. represents the steering vector of the M×1 vector hydrophone array, where the product term ,(x m , y m , z m) represents the coordinates of the mth vector hydrophone in the vector hydrophone array, (θ, φ) is the azimuth and elevation angle of the sound source target to be measured, and λ represents the wavelength of the sound wave. pv (t)=[n p (t), n vx (t), n vy (t), n vz (t)] represents the array noise. Assume that all noises have a mean of zero and a variance of δ n 2 The Gaussian distribution of each noise is uncorrelated with each other and with the sound pressure signal. Then the noise covariance matrix of the vector hydrophone array composed of M vector hydrophones is:

[0022]

[0023] In formula [2], I 4M Represents the 4M×4M identity matrix.

[0024] The present invention provides a method for accurate underwater target orientation by synthesizing vector hydrophone array signals, wherein the array of M array elements can be arranged in a circular array, a linear array or other irregular arrays. Specifically, according to the array coordinates of the vector hydrophone array composed of M vector hydrophones, the sidelobe level index in the non-observation direction, and the azimuth index in the direction to be observed, a conventional beamforming matrix b(α, β) is designed:

[0025]

[0026] In formula [3], Represents the M×1 weighted vector w, which is used to control the sidelobe level in the non-observation direction. Unit vector , is the beam steering angle, which indicates the approximate direction of the sound source to be observed, and can be set based on the prior information of the rough location of the sound source target. .

[0027] Furthermore, the conventional beamforming matrix b(α, β) is used to transform the vector hydrophone array signal Perform Kronecker product operation to synthesize the vector hydrophone array signal into a new vector signal, as shown in equation [4].

[0028]

[0029] In formula [4], the symbol Represents the Kronecker product operator. Substituting into equation [4], the new vector signal can be expressed as shown in equation [5].

[0030]

[0031] because is a complex constant, so the new vector signal has exactly the same expression as the sound pressure signal and velocity component obtained by the single vector hydrophone. The new vector signal contains the azimuth and pitch angle information of the target sound source. Therefore, the new vector signal can be equated to the signal of the new vector hydrophone (new single vector hydrophone).

[0032] Furthermore, the new vector signal is oriented to the target using a single vector hydrophone orientation method to solve the target angle. For example, commonly used single vector hydrophone orientation methods include: average sound intensity method, line spectrum analysis method, cross spectrum method, etc.

[0033] Since all the noises in the vector hydrophone array signal equation [1] have zero mean and variance Therefore, when the direction to be observed is aligned with the target angle, the power of the new vector signal can be derived as shown in formula [6].

[0034]

[0035] In formula [6], represents the noise power in the acoustic pressure signal and velocity component of the vector hydrophone in the vector hydrophone array, Represents the power of the sound pressure signal received by the vector hydrophone in the vector hydrophone array. The input signal of the new vector hydrophone corresponding to the new vector signal is compared with the input signal of each array element in the vector hydrophone array, and the single vector hydrophone input signal-to-noise ratio is uniformly expressed as , for the sound pressure signal, the coefficient ; For the velocity component, the coefficients are , , When the target is not in the direction of the vibration velocity, the output signal-to-noise ratio is , it can be seen that after the signal synthesis transformation, the introduced spatial processing gain is Therefore, the new vector signal Ratio vector hydrophone array signal It has a higher signal-to-noise ratio. And because the weighted average operation of the vector hydrophone array signal by the Kronecker product operation suppresses the random error of the array, the target orientation using the new vector signal is robust.

[0036] The present invention synthesizes the vector hydrophone array signal into a new vector signal, that is, constructs a new single vector hydrophone (new vector hydrophone), and then uses the single vector hydrophone orientation method to solve the target angle for the new vector signal. The present invention synthesizes the vector hydrophone array signal into a new vector signal by performing a Kronecker product operation on a conventional beamforming matrix and a vector hydrophone array signal, introduces a spatial processing gain and an array signal average operation, thereby improving the signal-to-noise ratio of the vector hydrophone array and the tolerance of the array error and the array element error, and then improves the accuracy of underwater target orientation.

[0037] refer to Figure 2 and Figure 4 The present invention is further illustrated below by a specific embodiment.

[0038] First, the vector hydrophone array signal with M=5 is obtained by simulation method. The amplitude values ​​of the component signals input into the five array elements are shown in Table 1. The azimuth and elevation angles of the observed target are both 45 degrees. Signal power is 1, the noise power is 1.

[0039] Table 1

[0040]

[0041] Furthermore, in order to obtain the line spectrum characteristics of underwater targets, the line spectrum frequencies are taken as 100 Hz and 150 Hz, where 100 Hz is the signal frequency and 150 Hz is the interference frequency; the FIR bandpass filter order is taken as 21, and the passband range is [75 Hz, 125 Hz]. The filter suppresses the interference of 150 Hz and captures the signal of 100 Hz.

[0042] Furthermore, a conventional beamforming matrix b(α,β) is designed. Take the weight vector w=[1, 1, 1, 1, 1] T , used to control the sidelobe level in the non-observation direction. Beam control angle Indicates the approximate observation direction and beam control angle The value is (40 degrees, 40 degrees), the unit vector u'=[0.5868, 0.4924, 0.6428] T , the wavelength λ of the sound wave is 15 meters. The coordinates of the five array elements and the obtained conventional beamforming matrix b(α, β) are shown in Table 2.

[0043] Table 2

[0044]

[0045] Furthermore, the conventional beamforming matrix b(α, β) is combined with the vector hydrophone array signal Perform Kronecker product operation to obtain a new vector signal with 4 amplitude parameter values , as shown in Table 3.

[0046] Table 3

[0047]

[0048] Furthermore, based on formula [5], the present invention adopts the line spectrum analysis directional algorithm of the single vector hydrophone and solves (θ, φ) = (45 degrees, 45 degrees). Based on formula [6], for the sound pressure component, the coefficient ŋ is 1, and for the velocity component, the coefficient ŋ is 0.5, 0.5, and 0.707 respectively, and the corresponding signal-to-noise ratio is 5 times the signal-to-noise ratio of the signal before synthesis, and the introduced spatial processing gain G is about 10×lg5≈7dB.

[0049] Since the exemplary embodiment is based on data obtained by simulation method, there are no outliers. In other embodiments, if the data of the vector hydrophone array is based on experimental collection, it is necessary to further take anti-interference measures to reduce interference, such as taking an average smoothing algorithm to eliminate outliers.

[0050] According to the underwater target precise orientation method of vector hydrophone array signal synthesis provided by the present invention, the number of array elements in the vector hydrophone array can be set to 3 to 7; if the number is too small, the gain obtained by the synthesized signal is small; if the number is too large, the expected synthesis effect may not be achieved due to the influence of installation errors and coherence of the underwater acoustic signal.

[0051] The above are only several embodiments of the present disclosure. Those skilled in the art may make various changes or modifications to the embodiments of the present disclosure based on the contents disclosed in the application documents without departing from the spirit and scope of the present disclosure.

Claims

1. A method for accurate underwater target orientation based on vector hydrophone array signal synthesis, characterized in that: include: Acquire a vector hydrophone array signal of a sound source associated with the underwater target, wherein the vector hydrophone array signal is configured as a 4M×1 vector x pv (t), contains the sound pressure signal and vibration velocity component of each array element, expressed as x pv (t) = [x p (t), x vx (t), x vy (t), x vz (t)] T ,in Where p(r, t) represents the sound pressure signal of the first array element, x p (t) represents the sound pressure signal of M array elements, x vx (t), x vy (t), z vz (t) represents the velocity component of M array elements; represents the steering vector of the M×1 vector hydrophone array, and the product term (x m ,y m , z m ) represents the coordinates of the mth element in the vector hydrophone array, are the azimuth and elevation angles of the underwater target to be measured, λ represents the wavelength of the sound wave; n pv (t) = [n p (t), n vx (t), n vy (t), n vz (t)] represents array noise; Design a conventional beamforming matrix b(α, β), which is configured as an M×1 vector and is expressed as Among them, [w1, w2, ... w M ] T represents an M×1 weighting vector used to control the sidelobe level in the non-observation direction; unit vector u′=[cosαcosβ,sinαcosβ,sinβ] T , (α, β) is the beam control angle, which is used to indicate the azimuth index of the direction to be observed; the product term The conventional beamforming matrix is ​​used to perform Kronecker product operation on the vector hydrophone array signal to synthesize a new vector signal, which is configured as a 4×1 vector y pv (t), the expression is Among them, y p (t) represents the sound pressure signal of the new vector hydrophone, y vx (t), y vy (t), y vz (t) represents the velocity component of the new vector hydrophone, represents the Kronecker product operator symbol; and Based on the new vector signal, the single-vector hydrophone orientation method is adopted to obtain the azimuth information of the underwater target.

2. The underwater target precise orientation method according to claim 1, characterized in that: 3≤M≤7。 3. The underwater target precise orientation method according to claim 2, characterized in that: The single-vector hydrophone orientation method is a line spectrum analysis orientation algorithm.

4. The underwater target precise orientation method according to claim 3, characterized in that: Before signal synthesis, the line spectrum signal of the vector hydrophone array signal is captured by a bandpass filtering method.

5. The underwater target precise orientation method according to claim 4, characterized in that: Also includes: Outliers in the position information of the underwater target are eliminated by an average smoothing algorithm.

6. The underwater target precise orientation method according to claim 1, characterized in that: The arrangement of the M array elements is circular, linear or irregular.

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