Sonar target motion identification method based on low-frame-rate bright spot structure sequence

Abstract

The invention discloses a sonar target motion identification method based on a low-frame-rate bright spot structure sequence. The sonar target motion identification method comprises the steps of 1, roughly intercepting a bright spot structure; 2, accumulating a bright spot structure, sonar platform information and tracking information; step 3, motion compensation of the sonar platform; 4, accurately intercepting a bright spot structure; and 5, searching the optimal radial speed. According to the method, target radial motion parameters are extracted by means of distance steep motion of a sonar target among multiple frames of echoes, and a speed estimation loss function based on bright spot structure global optimal estimation is innovatively designed for the problems that the time interval between adjacent echoes of a low-frame-rate sonar target is long and the bright spot structure fluctuates greatly. According to the method, the global similarity between input period bright spot structures is fully utilized, the distance steep motion measurement precision is improved, the radial speed of the sonar target can be given at the same time, and the motion identification precision and stability of the sonar target are improved.

Description

TECHNICAL FIELD

[0001] The present 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 ways of underwater target detection. When the acoustic signal transmitted 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 of Doppler velocity measurement and target tracking. Doppler velocity measurement mainly measures the Doppler frequency offset of the CW pulse echo to calculate 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 of 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 of the active sonar and unstable bright spot structure, the present 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 present application is as follows: A sonar target motion recognition method based on a low frame rate bright spot structure sequence, comprising: Step one: rough extraction of bright spot structure; Step two: accumulation of bright spot structure, sonar platform information and tracking information; Step three: sonar platform motion compensation; Step four: accurate extraction of bright spot structure; Step five: optimal radial velocity search.

[0006] In the step one, the received active echo data is subjected to low-pass filtering, downsampling, data accumulation, beam forming and matched filtering to obtain the bright spot structure of the target .

[0007] The step one, the multi-beam data processed by sonar system , assuming that the target exists in the i-beam, the bright spot structure of the target is obtained .

[0008] The step two, the history bright spot structure, the history sonar platform information (including the transmission timestamp, the platform motion speed) and the tracking information (including the side angle, the distance) in the detection process are cached, respectively obtaining the bright spot structure sequence , the transmission timestamp sequence , the platform motion speed sequence , the side angle sequence , the distance sequence , wherein represents the bright spot structure of the i-frame interception, represents the transmission timestamp of the i-frame, represents the platform motion speed of the i-frame, represents the target side angle of the i-frame, represents the target distance of the i-frame.

[0009] The step three, the distance abrupt change caused by the sonar platform motion is calculated through the geometric relationship , which is represented as .

[0010] The step four, first, the starting index of the bright spot structure accurate interception is calculated, which is represented as , the interception index is calculated, which is represented as , wherein represents the average of the vector, represents the bright spot structure interception length, and the bright spot structure after interception is represented as .

[0011] The step five, the optimal radial velocity search process is as follows: (1) the velocity range of the search is set and the search step , all possible velocity candidates are traversed; (2) according to the set velocity value , the abrupt distance of the bright spot structure sequence is calculated , the calculation formula is , the bright spot structure sequence is delayed, and the delayed bright spot structure sequence is obtained through the circular shift , wherein represents the bright spot structure after the delay processing; (3) define the velocity estimation loss function of the global optimal estimation of highlight structure , calculate the velocity estimation loss function of the highlight structure sequence after time delay (4) get the loss value sequence after traversal , select the minimum loss value corresponding to the velocity value as the velocity estimation value.

[0012] The present application can bring the following beneficial effects: In view of the problem that the time interval of adjacent echoes of low frame rate sonar targets is long and the highlight 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 velocity estimation loss function based on the global optimal estimation of highlight structure, fully utilizes the global similarity between the input periodic highlight 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

[0013] Figure 1 is the implementation flowchart of the present application; Figure 2 is the highlight structure sequence of the merchant ship target 1 echo; Figure 3 is the radial velocity extraction result of the merchant ship target 1 by the method of the present application; Figure 4 is the highlight structure sequence of the merchant ship target 2 echo; Figure 5 is the radial velocity extraction result of the merchant ship target 2 by the method of the present application. DETAILED DESCRIPTION

[0014] The present application will be further described below in combination with specific embodiments and drawings: The sonar target motion recognition method based on low frame rate highlight structure sequence provided by the present application has the implementation flowchart as shown in Figure 1 , and the specific implementation process is as follows: Step one: rough highlight structure extraction. After receiving the active echo data, the low-pass filtering, downsampling, data accumulation, beam forming and matching filtering are performed to obtain the highlight structure of the target .

[0015] The multi-beam data processed by the sonar system , assuming that the target exists in the i-th beam, the highlight structure of the target can be obtained .

[0016] 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.

[0017] Step 3: Sonar Platform Motion Compensation. The distance abrupt change caused by the sonar platform's motion is calculated using geometric relationships. , represented as .

[0018] 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.

[0019] 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. This represents the truncated length of the bright spot structure; the truncated bright spot structure is represented as follows. .

[0020] Step 5: Optimal radial velocity search. The detailed process is as follows: (1) Set the search speed range and search step size Iterate through all possible candidate speed values. .

[0021] (2) Based on the set speed value , the steep distance of the bright point structure sequence is calculated , the calculation formula is , the time delay processing is performed on the bright point structure sequence, and the time-delayed bright point structure sequence is obtained through cyclic shift , wherein represents the bright point structure after time delay processing.

[0022] (3) define the speed estimation loss function of the global optimal estimation of the bright point structure , the speed estimation loss function of the time-delayed bright point structure sequence is calculated.

[0023] (4) obtain the traversed loss value sequence , select the minimum loss value corresponding to the speed value as the speed estimation value.

[0024] 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 .

[0025] Merchant ship target 1: the echo bright point structure sequence of merchant ship target 1 is as 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, the approaching speed is 0.9 m / s, and the radial velocity extraction result of the merchant ship target 1 using the method of the present application is as 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.

[0026] Merchant ship target 2: the echo bright point structure sequence of merchant ship target 2 is as 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, the moving away speed is 0.8 m / s, and the radial velocity extraction result of the merchant ship target 2 using the method of the present application is as shown in Figure 5 , 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 -0.8 m / s, which is basically consistent with the actual motion speed, and the effect is also good.

[0027] The simulation analysis results show that the method of the present application fully utilizes the global similarity between the input periodic bright point structures, improves the distance steep measurement precision, can simultaneously give the radial velocity of the sonar target, and improves the sonar target motion recognition precision and stability.

[0028] It should be noted that the above examples are only the preferred embodiments of the present application, not to limit the scope of protection of the present application, on the basis of the above examples made by equivalent transformation all belong to the scope of protection 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; Step 5: Optimal radial velocity search.

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 .

6. The sonar target motion identification method based on low frame rate bright spot structure sequence according to claim 5, characterized in that: 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 the average of vectors. This represents the truncated length of the bright spot structure; the truncated bright spot structure is represented as follows. .

7. The sonar target motion identification method based on low frame rate bright spot structure sequence according to claim 6, characterized in that: 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: The bright spot structure sequence is delayed, and 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.

Images