A sonar target motion recognition method based on low frame rate highlight structure sequence

Abstract

The application discloses a kind of sonar target movement identification methods based on low frame rate bright spot structure sequence, including step one: bright spot structure rough intercepting;Step two: bright spot structure, sonar platform information, tracking information accumulation;Step three: sonar platform motion compensation;Step four: bright spot structure accurate intercepting;Step five: optimal radial velocity search.The method of the present application extracts target radial motion parameters using the distance abrupt change of sonar target between multiple frames of echoes, to solve the problem of long time interval between adjacent echoes and large bright spot structure fluctuation of low frame rate sonar target, innovatively designs a velocity estimation loss function based on global optimal estimation of bright spot structure, fully utilizes the global similarity between input periodic bright spot structures, improves the distance abrupt change measurement accuracy, and can simultaneously give the radial velocity of the sonar target, improves the sonar target movement identification accuracy and stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of underwater acoustics and underwater acoustic signal processing, and particularly relates to bright spot structure extraction and transmission signal frequency design, and especially to a sonar target motion recognition method based on a low-frame-rate bright spot structure sequence. BACKGROUND

[0002] Underwater target detection is an important research field in the field of underwater acoustics, and using an active sonar to detect underwater target information is one of the mainstream underwater target detection methods. When the acoustic signal emitted by the sonar in the water is reflected by the target and received by the hydrophone, some characteristics of the target can be reflected, which may specifically include the size of the target object, the movement speed, etc., and these characteristics are important basis for target type determination.

[0003] Target motion recognition can be achieved by two mainstream methods, Doppler velocity measurement and target tracking. Doppler velocity measurement mainly measures the Doppler frequency offset of the CW pulse echo to solve the target velocity, but when the target motion speed is low, the detection difficulty of the CW echo is greatly improved due to the influence of ocean reverberation, and the measurement accuracy and reliability are greatly reduced. Target tracking measures the change in the target azimuth and distance to calculate the motion speed, but since the sonar target is usually a range expansion target, the accurate distance of the target cannot be obtained, which introduces a large measurement error, and the measurement accuracy is not ideal. SUMMARY

[0004] To solve the problem of target motion recognition under the condition of long transmission interval and unstable bright spot structure of the active sonar, the application provides a sonar target motion recognition method based on a low-frame-rate bright spot structure sequence, which uses the distance abrupt change of the sonar target between multiple frames of echoes to extract the radial motion parameters of the target, innovatively proposes a velocity estimation loss function based on global optimal estimation of bright spot structure, fully utilizes the weak structure correlation between frames, enhances the distance abrupt change perception ability, and can estimate and recognize the motion speed of the sonar target, thereby improving the motion recognition accuracy and stability.

[0005] The technical scheme of the application is as follows:

[0006] A sonar target motion recognition method based on a low-frame-rate bright spot structure sequence, comprising:

[0007] Step 1: rough extraction of bright spot structure;

[0008] Step 2: accumulation of bright spot structure, sonar platform information and tracking information;

[0009] Step 3: sonar platform motion compensation;

[0010] Step 4: accurate extraction of bright spot structure;

[0011] Step 5: optimal radial velocity search.

[0012] In step one, the received active echo data is low-pass filtered, down-sampled, data accumulated, beamformed, and matched filtered to obtain the bright spot structure of the target .

[0013] In step one, the multi-beam data processed by the sonar system is obtained Assuming that the target exists in the i-th beam, the bright spot structure of the target is obtained .

[0014] In step two, the historical bright spot structure, historical sonar platform information (including transmission timestamp, platform motion speed), and tracking information (including side angle, distance) during the detection process are cached to obtain the bright spot structure sequence , the transmission timestamp sequence , the platform motion speed sequence , the side angle sequence , and the distance sequence , where represents the bright spot structure of the i-th frame, represents the transmission timestamp of the i-th frame, represents the platform motion speed of the i-th frame, represents the target side angle of the i-th frame, represents the target distance of the i-th frame.

[0015] In step three, the distance jump caused by the sonar platform motion is calculated through geometric relationship , which is represented as .

[0016] In step four, the starting index of the accurate bright spot structure extraction is first calculated, represented as , and the end index is calculated, represented as , where represents the average of the vector, represents the bright spot structure extraction length, and the extracted bright spot structure is represented as .

[0017] In step five, the optimal radial velocity search process is as follows:

[0018] (1) Set the velocity range for search and the search step size , and traverse all possible velocity candidates ;

[0019] (2) According to the set velocity value , the jump distance of the bright spot structure sequence is calculated , and the calculation formula is The bright spot structure sequence is delayed, and a delayed bright spot structure sequence is obtained through cyclic shift Wherein Indicates The bright spot structure after delay processing

[0020] (3) define the speed estimation loss function of the global optimal estimation of the bright spot structure , calculate the speed estimation loss function of the delayed bright spot structure sequence

[0021] (4) obtain the traversal loss value sequence Select the minimum loss value corresponding to the speed value as the speed estimation value.

[0022] The present application can bring the following beneficial effects:

[0023] For the problem that the time interval of adjacent echoes of low frame rate sonar targets is long and the bright spot structure fluctuates greatly, the method of the present application extracts the radial motion parameters of the target by using the distance steep change of the sonar target between multiple frames of echoes, innovatively designs a speed estimation loss function based on the global optimal estimation of the bright spot structure, fully utilizes the global similarity between the input periodic bright spot structures, improves the distance steep change measurement accuracy, can simultaneously give the radial velocity of the sonar target, and improves the sonar target motion recognition accuracy and stability. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the implementation flowchart of the present application

[0025] Figure 2 is the bright spot structure sequence of merchant ship target 1 echo

[0026] Figure 3 is the radial velocity extraction result of merchant ship target 1 of the method of the present application

[0027] Figure 4 is the bright spot structure sequence of merchant ship target 2 echo

[0028] Figure 5 is the radial velocity extraction result of merchant ship target 2 of the method of the present application DETAILED DESCRIPTION

[0029] The present application will be further described below in combination with specific embodiments and drawings:

[0030] The present application provides a sonar target motion recognition method based on low frame rate bright spot structure sequence, and the implementation flowchart is as shown in Figure 1 The specific implementation process is as follows:

[0031] Step 1: Rough Extraction of Bright Spot Structure. The received active echo data is processed through low-pass filtering, downsampling, data accumulation, beamforming, and matched filtering to obtain the target's bright spot structure. .

[0032] Multibeam data obtained from sonar system processing Assuming the target exists in the i-th beam, the bright spot structure of the target can be obtained. .

[0033] Step Two: Accumulation of Bright Spot Structures, Sonar Platform Information, and Tracking Information. Historical bright spot structures, historical sonar platform information (including launch timestamps and platform velocity), and tracking information (including hull angle and distance) from the detection process are cached to obtain a bright spot structure sequence. Launch timestamp sequence Platform motion velocity sequence hull angle sequence Distance sequence ,in This represents the bright spot structure captured in the i-th frame. This represents the transmission timestamp of the i-th frame. This represents the platform's motion velocity in the i-th frame. Indicates the target hull angle in the i-th frame. This represents the target distance in the i-th frame.

[0034] Step 3: Sonar Platform Motion Compensation. The distance abrupt change caused by the sonar platform's motion is calculated using geometric relationships. , represented as .

[0035] Specifically, The distance abrupt change caused by the motion of the sonar platform at any given moment is equal to the product of the radial velocity and the time difference, expressed as: ,in, Indicates the first Frame transmission timestamp, Indicates the first Frame platform motion speed, Indicates the first The target's hull angle in the frame. Therefore, for a time series, it can be represented in matrix form as an element-wise product. ,in, This represents the element-wise product of matrices.

[0036] Step 4: Precise Extraction of the Highlight Structure. First, calculate the starting index for precise extraction of the highlight structure, which can be represented as... Calculate the cutoff index, represented as ,in This represents the average of vectors. The intercepted length of the bright spot structure is represented as L, and the intercepted bright spot structure is represented as .

[0037] Step five: optimal radial velocity search. The detailed process is as follows:

[0038] (1) Set the velocity range of the search and the search step size , and traverse all possible velocity candidates .

[0039] (2) According to the set velocity value , calculate the steep distance of the bright spot structure sequence , and the calculation formula is , perform delay processing on the bright spot structure sequence, and obtain the delayed bright spot structure sequence through cyclic shift , wherein represents the bright spot structure after delay processing.

[0040] (3) Define the velocity estimation loss function of the global optimal estimation of the bright spot structure , and calculate the velocity estimation loss function of the delayed bright spot structure sequence.

[0041] (4) Obtain the loss value sequence after traversal , and select the velocity value corresponding to the minimum loss value as the velocity estimation value.

[0042] Description: The following simulation data is used to analyze and process merchant ship target 1 and merchant ship target 2, and the processing results of the present application are given, as shown in Figures 2-5 .

[0043] Merchant ship target 1: The bright spot structure sequence of the echo of merchant ship target 1 is shown in Figure 2 , by comparing the actual motion of the merchant ship target, it is known that the merchant ship target 1 gradually approaches, and the approaching speed is 0.9 m / s, the radial velocity extraction result of the merchant ship target 1 using the method of the present application is shown in Figure 3 , it can be seen that the method obtains the quantitative result of the radial motion speed distribution of the merchant ship target, wherein: the radial motion speed probability reaches the maximum at the position of 0.9 m / s, which is basically consistent with the actual motion speed, and the effect is good.

[0044] Merchant ship target 2: The bright spot structure sequence of the echo of merchant ship target 2 is shown in Figure 4 , by comparing the actual motion of the merchant ship target, it is known that the merchant ship target 2 gradually moves away, and the moving away speed is 0.8 m / s, the radial velocity extraction result of the merchant ship target 2 using the method of the present application is shown in Figure 5 ​As shown, it can be seen that the method obtains quantitative results of the radial motion velocity distribution of the merchant ship target, wherein the radial motion velocity probability reaches maximum at the position of-0.8 m / s, which is basically consistent with the actual motion velocity, and good results are also achieved.

[0045] The simulation analysis result shows that the method fully utilizes the global similarity between input periodic bright point structures, improves the distance step measurement precision, can simultaneously give the radial velocity of the sonar target, and improves the sonar target motion identification precision and stability.

[0046] It should be noted that the above embodiments are only the preferred embodiments of the present application, not to limit the protection scope of the present application, and the equivalent transformations made on the basis of the above embodiments all belong to the protection scope of the present application.

Claims

1. A sonar target motion identification method based on low frame rate bright spot structure sequences, characterized in that, include: Step 1: Roughly extract the key structural elements; Step Two: Accumulate information on key structural features, sonar platform details, and tracking data; Step 3: Motion compensation for the sonar platform; Step 4: Precisely extract the key structural features; In step four, the starting index for the precise extraction of the bright spot structure is first calculated, denoted as: Calculate the cutoff index, represented as ,in This represents averaging over vectors, where D is the range sequence and M is the range jump caused by the motion of the sonar platform. This represents the truncated length of the bright spot structure; the truncated bright spot structure is represented as follows. ; Step 5: Optimal radial velocity search; In step five, the optimal radial velocity search process is as follows: (1) Set the search speed range and search step size Iterate through all possible candidate speed values. ; (2) Based on the set speed value Calculate the steep movement distance of the bright spot structure sequence. The calculation formula is: ,in Represents the launch timestamp sequence. , Represents the timestamp of the first frame's transmission. The matrix is ​​represented by element-wise product, and then the bright spot structure sequence is delayed. The delayed bright spot structure sequence is obtained by cyclic shifting. ,in express The bright spot structure after time delay processing; (3) Define the velocity estimation loss function for the global optimal estimation of the bright spot structure. Calculate the velocity estimation loss function for the delayed bright spot structure sequence; (4) Obtain the loss value sequence after traversal The speed value corresponding to the minimum loss value is selected as the speed estimate.

2. The sonar target motion identification method based on low frame rate bright spot structure sequence according to claim 1, characterized in that: In step one, the received active echo data is processed through low-pass filtering, downsampling, data accumulation, beamforming, and matched filtering to obtain the target's bright spot structure. .

3. The sonar target motion identification method based on low frame rate bright spot structure sequence according to claim 1, characterized in that: In step one, the multibeam data obtained from the sonar system is processed. Assuming the target exists in the i-th beam, the bright spot structure of the target is obtained. .

4. A sonar target motion identification method based on a low frame rate bright spot structure sequence according to claim 2 or 3, characterized in that: In step two, the historical bright spot structures, historical sonar platform information, and tracking information from the detection process are cached to obtain bright spot structure sequences. Launch timestamp sequence Platform motion velocity sequence hull angle sequence Distance sequence ,in This represents the bright spot structure captured in the i-th frame. This represents the transmission timestamp of the i-th frame. This represents the platform's motion velocity in the i-th frame. Indicates the target hull angle in the i-th frame. This represents the target distance in the i-th frame.

5. The sonar target motion identification method based on low frame rate bright spot structure sequence according to claim 4, characterized in that: In step three, the distance abrupt change caused by the motion of the sonar platform is calculated using geometric relationships. , represented as ,in, This represents the element-wise product of matrices.

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