A Joint Detection and Tracking Method for Active Sonar Targets by Integrating CW and LFM Waveforms

Abstract

This invention discloses an active sonar joint target detection and tracking method integrating CW and LFM waveforms, comprising: Step 1) sequentially transmitting and receiving CW and LFM waves; Step 2) performing power spectrum estimation and target line spectrum detection based on the CW echo. When the target line spectrum is detected, the target Doppler velocity and target distance are obtained, and the target line spectrum detection reliability is estimated; Step 3) performing replica correlation peak detection based on the LFM echo and LFM waveform replica. If detected, the target distance, target echo correlation peak detection reliability, and channel multipath characteristics are estimated; Step 4) comparing the target line spectrum detection reliability and the target echo correlation peak detection reliability with their respective thresholds to determine the target tracking speed and target position; Step 5) if no target is detected, determining whether there is an active target tracking trajectory. If so, estimating the current tracking distance and current tracking speed; otherwise, returning to Step 2) until the target is captured again.

Description

Technical Field

[0001] This invention belongs to the field of active sonar detection, and in particular relates to an active sonar target joint detection and tracking method that integrates CW and LFM waveforms. Background Technology

[0002] When detecting targets, existing active sonars typically emit CW (single-frequency rectangular pulse) waves or LFM (linear frequency modulated pulse) waves separately, or although they emit CW and LFM waves simultaneously, they use each wave to detect the target separately and filter and track the target based on the detection results. They do not fully integrate and utilize the advantages of CW and LFM waves for joint target detection and tracking. As a result, their target detection and tracking performance is poor in harsh underwater acoustic environments or under interference conditions.

[0003] The ability to fully integrate and utilize the advantages of CW and LFM waveforms for joint target detection and tracking is crucial for improving the performance of active sonar target detection and tracking in underwater acoustic environments with distortions such as multipath and Doppler spread. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and to propose an active sonar target joint detection and tracking method that integrates CW and LFM waveforms.

[0005] To achieve the above objectives, this invention proposes a joint detection and tracking method for active sonar targets that integrates CW and LFM waveforms, comprising:

[0006] Step 1) The active sonar sequentially transmits CW waves and LFM waves to the target to be detected, and receives CW echoes and LFM echoes;

[0007] Step 2) Based on CW echo data, power spectrum estimation and target line spectrum detection are performed. When the target line spectrum is detected, the target Doppler velocity and target distance are estimated, and the confidence level of the target line spectrum detection is estimated.

[0008] Step 3) Based on LFM echo data and LFM waveform replicas, perform replica correlation peak detection. When a target echo correlation peak is detected, estimate the target distance and estimate the reliability of the target echo correlation peak detection and the channel multipath characteristics.

[0009] Step 4) Compare the target line spectrum detection confidence of CW echo and the target echo correlation peak detection confidence based on LFM echo with their respective thresholds. Based on the comparison, determine the target tracking speed and target position to achieve joint detection and tracking.

[0010] Step 5) If no target is detected, determine whether there is an active target tracking trajectory in the current state. If yes, estimate the current tracking distance and current tracking speed based on the historical distance and historical speed of the active target tracking trajectory. If no, go to step 2) until the target is captured again.

[0011] Preferably, step 4) includes:

[0012] When the confidence level of target line spectrum detection based on CW echo and the confidence level of target echo correlation peak detection based on LFM echo are both greater than their respective thresholds, the target Doppler velocity obtained in step 2) is used as the target tracking velocity, and the target position in the next frame is estimated and a tracking threshold is set; the target distance obtained in step 3) is used as the target tracking distance and target position.

[0013] Preferably, step 4) includes:

[0014] When the target line spectrum detection confidence of CW echo is greater than the corresponding threshold, and the target echo correlation peak detection confidence based on LFM echo is less than the corresponding threshold, the target Doppler velocity obtained in step 2) is used as the target tracking velocity, and the target position in the next frame is estimated and a tracking threshold is set.

[0015] Based on the target Doppler velocity and the channel multipath characteristics obtained in step 3), a replica correlation detector with the corresponding matching type and parameters is selected, and replica correlation peak detection is performed on the LFM echo again. When the target echo correlation peak is detected, the detection confidence of the target echo correlation peak is estimated again. If the detection confidence of the target echo correlation peak is greater than the corresponding threshold, the target distance based on the re-detection of the correlation peak is taken as the target tracking distance; otherwise, the target distance obtained in step 2) is taken as the target tracking distance.

[0016] Preferably, the step of selecting a replica correlation detector with corresponding matching type and parameters based on the target Doppler velocity and the channel multipath characteristics obtained in step 3), and then performing replica correlation peak detection on the LFM echo again, includes:

[0017] When the target Doppler velocity is greater than the set threshold, the segmented copy correlation detector is selected;

[0018] When the channel multipath feature shows that the extension exceeds the set threshold, select the replica correlation integral detector, and set the number of segments of the segmented replica correlation detector and the integration time of the replica correlation integral detector according to the target speed and multipath extension time.

[0019] Preferably, step 4) includes:

[0020] When the target line spectrum detection confidence of CW echo is less than the corresponding threshold, and the target echo correlation peak detection confidence based on LFM echo is greater than the corresponding threshold, the target distance obtained in step 3) is used as the target tracking distance. At the same time, based on the target detection distance of the current frame, the target tracking distance of the previous frame and the time difference, the target velocity is estimated and used as the target tracking velocity. The target position of the next frame is predicted, and the tracking threshold is set.

[0021] Preferably, step 4) includes:

[0022] When the target line spectrum detection confidence of CW echo and the target echo correlation peak detection confidence based on LFM echo are both less than their respective thresholds, the target estimated velocity and target detection distance with high detection confidence are selected as the target tracking velocity and target tracking distance.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] 1. Based on the Doppler velocity estimated by CW echo, the number of segments of the segmented replica detector of LFM echo is set to improve the LFM echo detection performance and target distance estimation performance;

[0025] 2. Based on the target distance and time interval detected by multiple LFM echo correlation peaks, the target velocity is estimated, improving the target velocity estimation performance when CW wave detection performance is poor;

[0026] 3. By combining the Doppler velocity estimated from the CW echo with the target position detected by the correlation peak of the LFM echo, the target position in the next frame is predicted, and a tracking threshold is set to achieve accurate prediction and robust tracking of the target when the detection performance is poor. Attached Figure Description

[0027] Figure 1 This is a flowchart of the active sonar target joint detection and tracking method that integrates CW and LFM waveforms according to the present invention. Detailed Implementation

[0028] This invention addresses the poor performance of active sonar in detecting and tracking high-speed maneuvering targets in underwater acoustic channels with distortions such as multipath and Doppler spread. It proposes a joint active sonar target detection and tracking method that integrates CW (single-frequency rectangular pulse) and LFM (linear frequency modulated pulse) waveforms. This method enables robust detection and tracking of high-speed maneuvering targets by the dominant sonar in complex underwater acoustic environments with distortions such as multipath and Doppler spread, thereby improving the target detection and tracking performance of active sonar in underwater acoustic environments with distortions such as multipath and Doppler spread.

[0029] The method includes:

[0030] Step 1) The active sonar sequentially transmits CW waves and LFM waves to the target to be detected, and receives CW echoes and LFM echoes;

[0031] Step 2) Based on CW echo data, power spectrum estimation and target line spectrum detection are performed. When the target line spectrum is detected, the target Doppler velocity and target distance are estimated, and the confidence level of the target line spectrum detection is estimated.

[0032] Step 3) Based on LFM echo data and LFM waveform replicas, perform replica correlation peak detection. When a target echo correlation peak is detected, estimate the target distance and estimate the reliability of the target echo correlation peak detection and the channel multipath characteristics.

[0033] Step 4) Compare the target line spectrum detection confidence of CW echo and the target echo correlation peak detection confidence based on LFM echo with their respective thresholds. Based on the comparison, determine the target tracking speed and target position to achieve joint detection and tracking.

[0034] Step 5) If no target is detected, determine whether there is an active target tracking trajectory in the current state. If yes, estimate the current tracking distance and current tracking speed based on the historical distance and historical speed of the active target tracking trajectory. If no, go to step 2) until the target is captured again.

[0035] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0036] Example

[0037] like Figure 1 As shown, embodiments of the present invention propose a joint detection and tracking method for active sonar targets by fusing CW and LFM waveforms. The technical solution is as follows:

[0038] 1) The active detection waveform of the present invention consists of a CW (single-frequency rectangular pulse) wave and an LFM (linear frequency modulated pulse) wave. The CW wave is mainly used to estimate the Doppler velocity of the target, while the LFM wave is mainly used to estimate the target range and channel multipath characteristics.

[0039] 2) After the active sonar sequentially transmits CW and LFM waves, it performs power spectrum estimation and target line spectrum detection based on the CW echo data. When the target line spectrum is detected, the target Doppler velocity and target distance are estimated, and the reliability of the line spectrum detection is estimated. Based on the LFM echo data and LFM waveform replicas, the replica correlation peak is detected for the target. When the target echo correlation peak is detected, the target distance is estimated, and the reliability of the target echo correlation peak detection and the channel multipath characteristics are estimated.

[0040] 3) If the confidence levels of both the target echo line spectrum detection based on CW echo and the target echo correlation peak detection based on LFM echo are high, then the target Doppler velocity detected based on CW echo line spectrum will be used as the target tracking velocity, and the target position in the next frame will be estimated based on the Doppler velocity, and a tracking threshold will be set; the target distance detected based on LFM echo copy correlation peak will be used as the target tracking distance and target position.

[0041] 4) If the reliability of target echo line spectrum detection based on CW echo is high, while the reliability of target echo correlation peak detection based on LFM echo is low, then the target Doppler velocity detected based on CW echo line spectrum is used as the target tracking velocity, and the target position is estimated based on the Doppler velocity, and a tracking threshold is set. At the same time, based on the estimated Doppler velocity characteristics and the estimated channel multipath spread characteristics, a replica correlation detector with the appropriate matching type and parameters is selected, and replica correlation detection is performed on the LFM echo again (for example, when the target Doppler velocity is large, a segmented replica correlation detector is selected; when the channel multipath spread is severe, a replica correlation integral detector is selected, and the number of segments of the segmented replica correlation detector and the integration time of the replica correlation integral detector are set according to the target velocity and multipath spread time). When the target echo correlation peak is detected, the reliability of the target echo correlation peak detection is estimated again. If the reliability is high, the target distance detected based on the re-correlation peak is used as the target tracking distance. If the reliability is still low, the target distance detected based on CW echo line spectrum is used as the target tracking distance.

[0042] 5) If the reliability of target echo correlation peak detection based on LFM echo is high, while the reliability of target echo line spectrum detection based on CW echo is low, then the target distance detected based on LFM echo replica correlation peak is used as the target tracking distance. At the same time, the target velocity is estimated based on the target detection distance in the current frame, the target tracking distance in the previous frame, and the time difference. The estimated velocity based on the target distance difference is used as the target tracking velocity. The target position in the next frame is also predicted, and a tracking threshold is set.

[0043] 6) If the confidence level of target echo line spectrum detection based on CW echo and the confidence level of target echo correlation peak detection based on LFM echo are both low, then select the target estimation speed and target detection distance with high detection confidence as the target tracking speed and target tracking distance.

[0044] 7) If no target is detected, if there is an active target tracking trajectory in the current state, estimate the current tracking distance and current tracking speed based on the target's historical distance and historical speed in the active target tracking trajectory; if there is no active target tracking trajectory in the current state, repeat steps 2) to 7) until the target is captured again.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A joint detection and tracking method for active sonar targets by fusing CW and LFM waveforms, comprising: Step 1) The active sonar sequentially transmits CW waves and LFM waves to the target to be detected, and receives CW echoes and LFM echoes; Step 2) Based on CW echo data, power spectrum estimation and target line spectrum detection are performed. When the target line spectrum is detected, the target Doppler velocity and target distance are estimated, and the confidence level of the target line spectrum detection is estimated. Step 3) Based on LFM echo data and LFM waveform replicas, perform replica correlation peak detection. When a target echo correlation peak is detected, estimate the target distance and estimate the reliability of the target echo correlation peak detection and the channel multipath characteristics. Step 4) Compare the target line spectrum detection confidence of CW echo and the target echo correlation peak detection confidence based on LFM echo with their respective thresholds. Based on the comparison, determine the target tracking speed and target position to achieve joint detection and tracking. Step 5) If no target is detected, determine whether there is an active target tracking trajectory in the current state. If yes, estimate the current tracking distance and current tracking speed based on the historical distance and historical speed of the active target tracking trajectory. If the result is negative, proceed to step 2) until the target is captured again.

2. The active sonar target joint detection and tracking method fusing CW and LFM waveforms according to claim 1, characterized in that, Step 4) includes: When the confidence level of target line spectrum detection based on CW echo and the confidence level of target echo correlation peak detection based on LFM echo are both greater than their respective thresholds, the target Doppler velocity obtained in step 2) is used as the target tracking velocity, and the target position in the next frame is estimated and a tracking threshold is set; the target distance obtained in step 3) is used as the target tracking distance and target position.

3. The active sonar target joint detection and tracking method fusing CW and LFM waveforms according to claim 1, characterized in that, Step 4) includes: When the target line spectrum detection confidence of CW echo is greater than the corresponding threshold, and the target echo correlation peak detection confidence based on LFM echo is less than the corresponding threshold, the target Doppler velocity obtained in step 2) is used as the target tracking velocity, and the target position in the next frame is estimated and a tracking threshold is set. Based on the target Doppler velocity and the channel multipath characteristics obtained in step 3), a replica correlation detector with the corresponding matching type and parameters is selected, and replica correlation peak detection is performed on the LFM echo again. When the target echo correlation peak is detected, the detection confidence of the target echo correlation peak is estimated again. If the detection confidence of the target echo correlation peak is greater than the corresponding threshold, the target distance based on the re-detection of the correlation peak is taken as the target tracking distance; otherwise, the target distance obtained in step 2) is taken as the target tracking distance.

4. The active sonar target joint detection and tracking method fusing CW and LFM waveforms according to claim 3, characterized in that, The step of selecting a replica correlation detector with appropriate matching type and parameters based on the target Doppler velocity and the channel multipath characteristics obtained in step 3), and then performing replica correlation peak detection on the LFM echo again, includes: When the target Doppler velocity is greater than the set threshold, the segmented copy correlation detector is selected; When the channel multipath feature shows that the extension exceeds the set threshold, select the replica correlation integral detector, and set the number of segments of the segmented replica correlation detector and the integration time of the replica correlation integral detector according to the target speed and multipath extension time.

5. The active sonar target joint detection and tracking method fusing CW and LFM waveforms according to claim 1, characterized in that, Step 4) includes: When the target line spectrum detection confidence of CW echo is less than the corresponding threshold, and the target echo correlation peak detection confidence based on LFM echo is greater than the corresponding threshold, the target distance obtained in step 3) is used as the target tracking distance. At the same time, based on the target detection distance of the current frame, the target tracking distance of the previous frame and the time difference, the target velocity is estimated and used as the target tracking velocity. The target position of the next frame is predicted, and the tracking threshold is set.

6. The active sonar target joint detection and tracking method fusing CW and LFM waveforms according to claim 1, characterized in that, Step 4) includes: When the target line spectrum detection confidence of CW echo and the target echo correlation peak detection confidence based on LFM echo are both less than their respective thresholds, the target estimated velocity and target detection distance with high detection confidence are selected as the target tracking velocity and target tracking distance.

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