CN110764092A - A method and system for azimuth tracking of underwater acoustic targets based on azimuth history map - Google Patents

Abstract

The invention discloses an underwater sound target position tracking method and system based on a position history chart, wherein the method comprises the following steps: step 1) establishing an underwater sound target azimuth course map; step 2) a previous time T_n‑1The target azimuth angle is used as a search center, and the current time T is established_nThe matching template of (2); step 3) based on T_n‑1The matching template of the time is used for searching the current time T within a certain azimuth angle searching range_nThe azimuth history chart is subjected to two-dimensional matching search, and the azimuth corresponding to the position with the highest matching degree is taken as T_nThe orientation of the time; and 4) adding 1 to n, and turning to the step 2) until the target disappears. The method can effectively inhibit multi-target interference and realize stable and continuous tracking of the weak target direction.

Description

A method and system for azimuth tracking of underwater acoustic targets based on azimuth history map

technical field

The invention relates to the technical field of passive sonar signal and information processing, and more particularly to a method and system for azimuth tracking of an underwater acoustic target based on an azimuth history map.

Background technique

The radiated noise of underwater acoustic targets, such as engine noise, underwater acoustic detection pulses, and underwater acoustic communication pulses, can be used by passive detection sonar arrays for target orientation tracking.

It is a common method for underwater acoustic target discovery and azimuth tracking to find and automatically track the target with the aid of the underwater acoustic target azimuth history map. If there is an underwater sound source in the current azimuth direction, the amplitudes of each element signal after time compensation will be superimposed in the same direction during the fusion process, otherwise it will be completely or partially canceled. Therefore, the energy of the composite beam in the target azimuth will be higher than that of the other azimuths. If the noise source persists, a stable bright trajectory will appear on the underwater acoustic target azimuth histogram, and the trajectory will have a corresponding slope or curvature change with the change of the target sound source azimuth.

In practical applications, if the user finds a bright track on the underwater acoustic target azimuth histogram, it can be considered that there is a target in the corresponding azimuth. By tracking the trajectory, the azimuth tracking of the target can be realized. In order to reduce the workload of the user in performing the duty task, the target orientation can be tracked by means of automatic tracking. The specific steps of the existing automatic underwater acoustic target azimuth tracking are:

1. After the user finds the target at time T _n , the target azimuth is manually initialized;

2. At the next time T _n+1 , the automatic tracking system takes the target azimuth at time T _n as the center, searches for the synthetic beam with the largest energy within the limited range of azimuth angles, and takes its corresponding azimuth angle as time T _n+1 the target azimuth;

3. Take the target azimuth angle measured at time T _n+1 as the search center of the target azimuth angle at the next time T _n+2 , search for the synthetic beam with the largest energy within the limited azimuth angle range, and set its corresponding azimuth angle angle as the target azimuth at time T _n+2 ;

In practical applications, the trajectory tracking of underwater acoustic azimuth histories faces the problem of multi-target cross-interference. It is manifested that when other interfering targets appear near the azimuth of the target of interest, a cross trajectory will appear on the azimuth history map, causing tracking deviation. Especially when the noise intensity of the target of interest is weaker than that of the interference target, the traditional tracking method will inevitably lead to tracking deviation.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above-mentioned technical defects, and proposes a method for azimuth tracking of an underwater acoustic target based on an azimuth history map, the method comprising:

Step 1) Establish an underwater acoustic target azimuth history map;

Step 2) The target azimuth of the previous moment T _n-1 is the search center, and the matching template of the current moment T _n is established;

Step 3) Based on the matching template of the current time _Tn , perform a two _- dimensional matching search on the azimuth history map of the current time Tn within a certain azimuth angle search range, and take the azimuth angle corresponding to the position with the highest matching degree as the current time T azimuth of _n ;

Step 4) Increase n by 1, and go to step 2) until the target disappears.

As an improvement of the above method, the step 2) specifically includes:

Step 201) on the azimuth history map, analyze the motion trajectory of the target of interest, and obtain the azimuth change situation in the previous ΔT time period;

The bright trajectory on the target azimuth history map is described as t=kα+b, t represents time, α represents the azimuth angle of the target at time t, and k and b are parameters to be estimated;

By estimating the parameters k and b based on the minimum variance, we have:

Among them, α _n-1-i represents the azimuth angle of the target at the time T _n-1-i ; 1≤i≤m; m is the number of snapshots used for motion analysis; at the initial moment, manually find the target and obtain the target's azimuth. Azimuth;

Step 202) according to the motion trajectory analysis result in step 201), establish the matching template of the current time T _n on the target orientation history map;

Establish a matrix G that matches the template, each row of G corresponds to a snapshot time point, and each column corresponds to an observation angle, then the value of each element of G is calculated as:

in

x ₁ =x cosθ+y sinθ

y ₁ =-x sinθ+y cosθ

γ为条纹的空间纵横比，δ为高斯因子标准差，λ为条纹宽度的调整参数。in,

γ is the spatial aspect ratio of the stripes, δ is the standard deviation of the Gaussian factor, and λ is the adjustment parameter of the stripe width.

As an improvement of the above method, the step 3) specifically includes:

At the current time T _n , the target azimuth angle of the previous time T _n-1 is the center, and the sliding matching is performed along the abscissa with the matrix G of the matching template as the standard within the limited azimuth angle range;

Calculate the correlation parameter Corr in the sliding process:

为方位历程图

结点处对应的能量值；

为方位角，取值范围[α_n-1-β，α_n-1+β]；τ为时间，取值范围[T_n-ΔT，T_n]；α_n-1为T_n-1时刻的目标方位角；Among them, [-β, β] is the value range of the azimuth angle corresponding to the matrix G,

azimuth history map

The corresponding energy value at the node;

is the azimuth, the value range [α _n-1 -β, α _n-1 +β]; τ is the time, the value range [T _n -ΔT, T _n ]; α _n-1 is the time T _n-1 the target azimuth;

为目标在当前时刻T_n的方位角。When the correlation parameter Corr is the largest, its corresponding azimuth

_is the azimuth of the target at the current time Tn.

The present invention also proposes an underwater acoustic target azimuth tracking system based on the azimuth history map, the system comprising:

The azimuth history map establishment module is used to establish the azimuth history map of the underwater acoustic target;

A matching template establishment module is used to take the target azimuth of the current moment T _n-1 as the search center to establish the matching template of the current moment T _n ;

The search module _is used to perform a two _- dimensional matching search on the azimuth history map of the current time Tn within a certain azimuth angle search range based on the matching template of the current time Tn, and use the azimuth angle corresponding to the position with the highest matching degree as the current _Azimuth at time Tn.

As a kind of improvement of the above-mentioned system, the concrete realization process of described matching template establishment module is:

The movement trajectory of the target of interest is analyzed on the azimuth history map, and the azimuth change trend in the previous ΔT time period is obtained;

The bright trajectory on the target azimuth history map is described as t=kα+b, t represents time, α represents the azimuth angle of the target at time t, and k and b are parameters to be estimated;

By estimating the parameters k and b based on the minimum variance, we have:

Among them, α _n-1-i represents the azimuth angle of the target at the time T _n-1-i ; 1≤i≤m; m is the number of snapshots used for motion analysis; at the initial moment, manually find the target and obtain the target's azimuth. Azimuth;

According to the analysis result of the motion trajectory, establish the matching template of the current time _Tn on the target orientation history map;

Establish a matrix G that matches the template, each row of G corresponds to a snapshot time point, and each column corresponds to an observation angle, then the value of each element of G is calculated as:

in

x ₁ =x cosθ+y sinθ

y ₁ =-x sinθ+y cosθ

γ为条纹的空间纵横比，δ为高斯因子标准差，λ为条纹宽度的调整参数。in,

γ is the spatial aspect ratio of the stripes, δ is the standard deviation of the Gaussian factor, and λ is the adjustment parameter of the stripe width.

As an improvement of the above system, the specific implementation process of the search module is:

At the current time T _n , the target azimuth at the previous time T _n-1 is the center, and the sliding matching is performed along the abscissa with the matrix G of the matching template as the standard within the limited azimuth range;

Calculate the correlation parameter Corr in the sliding process:

为方位历程图

结点处对应的能量值；

为方位角，取值范围[α_n-1-β，α_n-1+β]；τ为时间，取值范围[T_n-ΔT，T_n]；α_n-1为T_n-1时刻的目标方位角；Among them, [-β, β] is the value range of the azimuth angle corresponding to the matrix G,

azimuth history map

The corresponding energy value at the node;

is the azimuth, the value range [α _n-1 -β, α _n-1 +β]; τ is the time, the value range [T _n -ΔT, T _n ]; α _n-1 is the time T _n-1 the target azimuth;

为目标在当前时刻T_n的方位角。When the correlation parameter Corr is the largest, its corresponding azimuth

_is the azimuth of the target at the current time Tn.

The advantages of the present invention are:

The method of the invention can effectively suppress multi-target interference and realize stable and continuous tracking of weak target azimuth.

Description of drawings

Figure 1 is the original image of the target orientation map for testing;

Fig. 2 is the tracking result of the traditional tracking method;

3 is a schematic diagram of the results of the underwater acoustic target direction finding method based on the azimuth history diagram of the present invention.

Detailed ways

The method of the present invention will be described in detail below.

The present invention proposes an azimuth tracking method for an underwater acoustic target based on an azimuth history map, which specifically includes:

Step 1) Establish a azimuth history map of the underwater acoustic target, which specifically includes:

1. According to a certain time interval, intercept the received signal of a fixed-length sonar array;

2. Based on a certain array element of the sonar array, according to a certain azimuth angle interval, calculate the time difference of the target noise received by each array element under the corresponding azimuth angle;

3. According to the time difference of the target noise received by each array element, perform time compensation on the received signal of each array element (translate the signal along the time axis, so that the initial phase of the received target noise of each array element is consistent);

4. Perform weighting or equal-weight fusion on the time-compensated received signals to obtain a synthetic beam at the corresponding azimuth angle;

5. Calculate the total energy value of the synthesized beam at the corresponding azimuth angle, and obtain the beam energy spectrum with the azimuth angle as the abscissa and the energy amplitude as the ordinate, which is called the azimuth energy spectrum of the synthesized beam;

6. Establish a time-azimuth space coordinate system, and use gray value to represent the beam energy amplitude corresponding to <time azimuth>, and then the azimuth history map of the underwater acoustic target can be obtained.

Step 2) take the target azimuth of the previous moment T _n-1 as the search center, and establish a matching template;

Step 201) on the azimuth history map, analyze the motion trajectory of the target of interest, and obtain its azimuth change situation in the near ΔT time period;

Assume that the azimuth corresponding to the target at time t is α. Considering that the azimuth of the underwater acoustic target generally changes slowly, it can be approximated as a linear change within a certain short period of time ΔT, and the bright trajectory on the target azimuth history map can be described as t = kα+b, where t represents time, and α represents the azimuth of the target at time t; k and b are parameters to be estimated; parameters k and b are estimated by the method based on the minimum variance, as follows:

By estimating the parameters k and b based on the minimum variance, we have:

Among them, α _n-1-i represents the azimuth angle of the target at the time T _n-1-i ; 1≤i≤m; m is the number of snapshots used for motion analysis; at the initial moment, manually find the target and obtain the target's azimuth. Azimuth;

Step 202) Assuming that the movement situation of the target at the current moment Tn _is the same as the movement situation presented in the previous ΔT time period, then according to the movement trajectory analysis result in step 201), the image simulation method can _be used to obtain Tn on the target orientation history map. The matching template of the moment;

Establish a matrix G that matches the template, each row of G corresponds to a snapshot time point, and each column corresponds to an observation angle, then the value of each node of G is calculated as:

in

x ₁ =x cosθ+y sinθ

y ₁ =-x sinθ+y cosθ

γ为条纹的空间纵横比，δ为高斯因子标准差，λ为条纹宽度的调整参数。In the above formula

γ is the spatial aspect ratio of the stripes, δ is the standard deviation of the Gaussian factor, and λ is the adjustment parameter of the stripe width.

Step 3) Based on the matching template at time T _n , perform a two-dimensional matching search on the current azimuth history map at time T _n within a certain azimuth angle search range, and use the azimuth corresponding to the position with the highest matching degree as the latest update at time T _n . azimuth, the tracking of the target can be realized;

At the current time T _n , the target azimuth angle of the previous time T _n-1 is the center, and the sliding matching is performed along the abscissa with the matrix G of the matching template as the standard within the limited azimuth angle range;

Calculate the correlation parameter Corr in the sliding process:

为方位历程图

结点处对应的能量值；

为方位角，取值范围[α_n-1-β，α_n-1+β]；τ为时间，取值范围[T_n-ΔT，T_n]；α_n-1为T_n-1时刻的目标方位角；Among them, [-β, β] is the value range of the azimuth angle corresponding to the matrix G,

azimuth history map

The corresponding energy value at the node;

is the azimuth, the value range [α _n-1 -β, α _n-1 +β]; τ is the time, the value range [T _n -ΔT, T _n ]; α _n-1 is the time T _n-1 the target azimuth;

为目标在T_n时刻的方位角。When the correlation parameter Corr is the largest, its corresponding azimuth

is the azimuth of the target at time T _n .

Step 4) Increase n by 1, and go to step 2) until the target disappears.

The present invention also proposes an underwater acoustic target azimuth tracking system based on the azimuth history map, the system comprising:

The azimuth history map establishment module is used to establish the azimuth history map of the underwater acoustic target;

A matching template establishment module is used to take the target azimuth of the current moment T _n-1 as the search center to establish the matching template of the current moment T _n ;

The search module _is used to perform a two _- dimensional matching search on the azimuth history map of the current time Tn within a certain azimuth angle search range based on the matching template of the current time Tn, and use the azimuth angle corresponding to the position with the highest matching degree as the current _Azimuth at time Tn.

Example verification:

Figure 1 shows the original image of the azimuth target histogram used for testing. The brighter the trace in Figure 1 is, the stronger the target intensity is. There are 3 targets from left to right at the bottom of Figure 1, of which the leftmost target is a weak target of interest, and the other two targets are strong interference targets. The target with weak interest and two targets with strong interference form an intersection at the same time.

Figure 2 shows the tracking results of the traditional tracking method based on the energy maximum, which is indicated by a green cross in the azimuth histogram. It is clearly seen that tracking deviation is induced at the first strong target disturbance, resulting in tracking failure.

Figure 3 shows the tracking results of the method of the present invention. The prior information is the data of 90 snapshots, the width of the matching template G is 20 observation azimuth intervals, the height of G is 30 snapshot intervals, the spatial aspect ratio γ of the stripes is 0.05, and the Gaussian factor standard deviation δ is 2.4 , the stripe width λ is 30. It can be seen that the method of the present invention effectively avoids the interference of strong targets at the intersection of multiple targets, and successfully performs azimuth tracking on the weak trajectory of the target of interest.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that any modification or equivalent replacement of the technical solutions of the present invention will not depart from the spirit and scope of the technical solutions of the present invention, and should be included in the present invention. within the scope of the claims.

Claims (6)

1. A method for azimuth tracking of an underwater acoustic target based on an azimuth history map, the method comprising: Step 1) Establish an underwater acoustic target azimuth history map; Step 2) The target azimuth of the previous moment T _n-1 is the search center, and the matching template of the current moment T _n is established; Step 3) Based on the matching template of the current time _Tn , perform a two _- dimensional matching search on the azimuth history map of the current time Tn within a certain azimuth angle search range, and take the azimuth angle corresponding to the position with the highest matching degree as the current time T azimuth of _n ; Step 4) Increase n by 1, and go to step 2) until the target disappears. 2. The method according to claim 1, wherein the step 2) specifically comprises: Step 201) on the azimuth history map, analyze the motion trajectory of the target of interest, and obtain the azimuth change situation in the previous ΔT time period; The bright trajectory on the target azimuth history map is described as t=kα+b, t represents time, α represents the azimuth angle of the target at time t, and k and b are parameters to be estimated; By estimating the parameters k and b based on the minimum variance, we have:

Among them, α _n-1-i represents the azimuth angle of the target at the time T _n-1-i ; 1≤i≤m; m is the number of snapshots used for motion analysis; at the initial moment, manually find the target and obtain the target's azimuth. Azimuth; Step 202) according to the motion trajectory analysis result in step 201), establish the matching template of the current time T _n on the target orientation history map; Establish a matrix G that matches the template, each row of G corresponds to a snapshot time point, and each column corresponds to an observation angle, then the value of each element of G is calculated as: in x ₁ =x cosθ+y sinθ y ₁ =-x sinθ+y cosθ in,

γ is the spatial aspect ratio of the stripes, δ is the standard deviation of the Gaussian factor, and λ is the adjustment variable of the stripe width. 3. The method according to claim 2, wherein the step 3) specifically comprises: At the current time T _n , the target azimuth angle of the previous time T _n-1 is the center, and the sliding matching is performed along the abscissa with the matrix G of the matching template as the standard within the limited azimuth angle range; Calculate the correlation parameter Corr in the sliding process:

Among them, [-β, β] is the value range of the azimuth angle corresponding to the matrix G,

azimuth history map

The corresponding energy value at the node;

is the azimuth, the value range [α _n-1 -β, α _n-1 +β]; τ is the time, the value range [T _n -ΔT, T _n ]; α _n-1 is the time T _n-1 the target azimuth; When the correlation parameter Corr is the largest, its corresponding azimuth

_is the azimuth of the target at the current time Tn. 4. An underwater acoustic target azimuth tracking system based on azimuth history map, characterized in that the system comprises: The azimuth history map establishment module is used to establish the azimuth history map of the underwater acoustic target; A matching template establishment module is used to take the target azimuth of the current moment T _n-1 as the search center to establish the matching template of the current moment T _n ; The search module _is used to perform a two _- dimensional matching search on the azimuth history map of the current time Tn within a certain azimuth angle search range based on the matching template of the current time Tn, and use the azimuth angle corresponding to the position with the highest matching degree as the current _Azimuth at time Tn. 5. system according to claim 4, is characterized in that, the concrete realization process of described matching template establishment module is: The movement trajectory of the target of interest is analyzed on the azimuth history map, and the azimuth change trend in the previous ΔT time period is obtained; The bright trajectory on the target azimuth history map is described as t=kα+b, t represents time, α represents the azimuth angle of the target at time t, and k and b are parameters to be estimated; By estimating the parameters k and b based on the minimum variance, we have:

Among them, α _n-1-i represents the azimuth angle of the target at the time T _n-1-i ; 1≤i≤m; m is the number of snapshots used for motion analysis; at the initial moment, manually find the target and obtain the target's azimuth. Azimuth; According to the analysis result of the motion trajectory, establish the matching template of the current time _Tn on the target orientation history map; Establish a matrix G that matches the template, each row of G corresponds to a snapshot time point, and each column corresponds to an observation angle, then the value of each element of G is calculated as:

in x ₁ =x cosθ+y sinθ y ₁ =-x sinθ+y cosθ in,

γ is the spatial aspect ratio of the stripes, δ is the standard deviation of the Gaussian factor, and λ is the adjustment parameter of the stripe width. 6. system according to claim 5, is characterized in that, the concrete realization process of described search module is: At the current time T _n , the target azimuth angle of the previous time T _n-1 is the center, and the sliding matching is performed along the abscissa with the matrix G of the matching template as the standard within the limited azimuth angle range; Calculate the correlation parameter Corr in the sliding process:

Among them, [-β, β] is the value range of the azimuth angle corresponding to the matrix G,

azimuth history map

The corresponding energy value at the node; is the azimuth, the value range [α _n-1 -β, α _n-1 +β]; τ is the time, the value range [T _n -ΔT, T _n ]; α _n-1 is the time T _n-1 the target azimuth; When the correlation parameter Corr is the largest, its corresponding azimuth

_is the azimuth of the target at the current time Tn.

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