An underwater sonar positioning method and system for a marine vessel
By analyzing the acoustic pulse signals of multiple sonar buoys, calculating the thermocline interference coefficient and initial confidence level, and selecting reliable sonar signals, the problem of pulse broadening caused by the thermocline was solved, thereby improving the accuracy of underwater positioning of ships and the ability to identify seabed structures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN SHIP NAVIGATION (SANYA) TECH SERVICE PARTNERSHIP (LLP)
- Filing Date
- 2026-05-09
- Publication Date
- 2026-07-21
AI Technical Summary
Existing technologies have failed to effectively address the pulse broadening phenomenon caused by changes in sound velocity gradient due to the thermocline, which affects the range resolution of sonar systems and the positioning accuracy of seabed structures, leading to inaccurate underwater positioning of ships.
By acquiring acoustic pulse signals from multiple distributed sonar buoys, calculating the temperature jump interference coefficient and initial confidence level, screening reliable sonar signals, performing time series analysis and in-phase superposition processing, and extracting effective signals, underwater positioning of ships can be achieved.
It reduces the impact of thermocline interference, improves the positioning accuracy of the sonar system and the ability to identify seabed structures, and ensures the accuracy of waterway safety assessment.
Smart Images
Figure CN122151088B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wireless positioning technology, and specifically to an underwater sonar positioning method and system for ships. Background Technology
[0002] In key areas of ocean shipping routes, existing technologies typically deploy multiple buoys equipped with active sonar to form a distributed sound source, combined with ships as mobile receiving platforms, to construct a multi-base sonar detection network. Based on the principles of sound wave propagation and reflection in water, this network receives acoustic signals emitted by buoys at different spatial locations and reflected by the seabed topography. By achieving precise spatiotemporal synchronization and combining multi-node geometric calculations, high-resolution three-dimensional seabed images can be synthesized, accurately identifying obstacles and irregular terrain such as reefs, shipwrecks, and shoals beneath the shipping channel. Based on the acquired data, a comprehensive assessment of the channel's water depth conditions and seabed safety can be conducted, providing support for safe navigation.
[0003] Due to the influence of solar radiation, freshwater input, and ocean currents, the ocean often forms vertical water layers with significant differences in temperature and salinity, namely thermoclines and salinity strata. These differences in physical properties directly lead to variations in local seawater sound speed, creating a distinct sound speed gradient. When a pulsed sound wave emitted by sonar crosses such a sound speed interface during propagation, its propagation path is bent due to refraction, causing sound waves from the same target to reach the receiver through multiple paths of varying lengths and time delays. The superposition of signals from different paths stretches and blurs the originally clear pulse waveform in the time domain, producing a phenomenon known as "pulse broadening." This phenomenon not only reduces the range resolution of the sonar system but also causes deviations or signal overlap in the depth and horizontal directions of echo location of seabed structures or obstacles, severely affecting the ability to determine the true shape and precise location of the seabed topography, and restricting the reliability of channel safety assessments and ship navigation. Summary of the Invention
[0004] To address the problem of inaccurate underwater positioning of ships caused by the use of excessively interfering sonar pulse signals due to the failure of existing technologies to consider the interference of pulse broadening on all received sonar pulse signals, the present invention aims to provide an underwater sonar positioning method and system for ships. The specific technical solution adopted is as follows: The ship receives acoustic pulse signals from multiple distributed sonar buoys targeting the same target location, and calculates multiple depths corresponding to the target location based on each acoustic pulse signal. The temperature jump interference coefficient for each target location is calculated based on the depth differences between multiple depths corresponding to each target location. Time-series analysis is performed on each acoustic pulse signal at each target location to determine the initial reliability of each acoustic pulse signal at each target location; Based on the initial confidence level and temperature jump interference coefficient of each target location, the final confidence level of each acoustic pulse signal at the target location is determined. Based on the final confidence level, reliable sonar signals are selected from all acoustic pulse signals at the target location, and underwater positioning of the ship is achieved based on the reliable sonar signals.
[0005] Furthermore, the acquisition of acoustic pulse signals received by the ship from multiple distributed sonar buoys targeting the same location includes: A multi-channel digital signal sequence for acquiring echo information is obtained through a signal receiving array at the bottom of the ship. Based on the array geometry and beam pointing, the pre-calculated time delay and weighting values are used to perform in-phase superposition processing on the multi-channel digital signal sequence to obtain the processed echo information. Effective signal extraction is performed on the processed echo information to obtain the acoustic pulse signal of each sonar buoy for each target location.
[0006] Furthermore, the calculation of the temperature jump interference coefficient at each target location includes: For all acoustic pulse signals at each target location, the degree of dispersion is calculated based on the time length of each acoustic pulse signal to determine the pulse phenomenon performance at each target location. For each acoustic pulse signal at each target location, the degree of dispersion is calculated based on the depth corresponding to each acoustic pulse signal, and the depth measurement deviation at each target location is determined. Based on the pulse phenomenon performance and depth measurement deviation at each target location, the temperature jump interference coefficient at each target location is determined.
[0007] Furthermore, the initial confidence level of each acoustic pulse signal at each target location is determined, including: Time-series analysis is performed on each acoustic pulse signal at the target location to determine several broadening nodes in each acoustic pulse signal at the target location. The initial confidence level of each acoustic pulse signal at each target location is determined based on the consistency of the broadening nodes in time among multiple acoustic pulse signals at the target location.
[0008] Furthermore, several broadening nodes in each acoustic pulse signal at the target location are determined, including: Acquire the pre-segmented sonar signal at each target location using the acoustic pulse signal at each moment. Based on the aforementioned segmented sonar signal, frequency domain conversion processing is performed to determine the number of effective frequency components of the aforementioned segmented sonar signal. Based on the number of effective frequency components of the preceding segmented sonar signal of each acoustic pulse signal at the target location at each time step and the change in acoustic amplitude of each acoustic pulse signal between adjacent time steps, the preceding purity of each acoustic pulse signal at the target location at each time step is determined. Based on the pre-purity of each acoustic pulse signal at the target location at each time step, several broadening nodes in each acoustic pulse signal at the target location are determined.
[0009] Furthermore, based on the pre-purity of each acoustic pulse signal at the target location at each time step, several broadening nodes in each acoustic pulse signal at the target location are determined, including: Based on the pre-purity of each acoustic pulse signal at the target location at each time step and its pre-purity at adjacent time steps, the difference in pre-purity of each acoustic pulse signal at the target location at each time step is determined. Based on the difference in the preceding purity of each acoustic pulse signal at the target location at each time step, a baseline value for the difference in preceding purity of each acoustic pulse signal at the target location at each time step is determined. Based on the difference in pre-purity of each acoustic pulse signal at the target location at each moment and the pre-purity benchmark value, several broadening nodes in the time sequence of each acoustic pulse signal at the target location are determined.
[0010] Furthermore, determining the initial reliability of each acoustic pulse signal at the target location based on the temporal consistency of the broadening nodes in multiple acoustic pulse signals at the target location includes: Based on all acoustic pulse signals at each target location, any one acoustic pulse signal is selected as the standard acoustic pulse signal. Using the length of the standard acoustic pulse signal as a reference, all other acoustic pulse signals are processed to a fixed length to obtain several fixed-length processed acoustic pulse signals for each target position. Clustering is performed on all broadened nodes in the standard acoustic pulse signal and all fixed-length processed acoustic pulse signals to obtain several clusters; Based on the number of broadened nodes in the standard acoustic pulse signal and the number of clusters to which each broadened node belongs, the dispersion distribution of broadened nodes in each standard acoustic pulse signal at each target location is determined. Based on the time difference between each broadening node in the standard acoustic pulse signal and other broadening nodes in its cluster, the temporal dispersion of the broadening nodes in each standard acoustic pulse signal at each target location is determined. Based on the dispersion degree of the broadened nodes and the temporal dispersion degree of the broadened nodes, the initial confidence level of each standard acoustic pulse signal at each target location is determined.
[0011] Furthermore, determining the final confidence level of each acoustic pulse signal at the target location based on the initial confidence level and the temperature jump interference coefficient at each target location includes: Based on the temperature jump interference coefficient at each target location, the confidence adjustment coefficient for each acoustic pulse signal at each target location is determined; Based on the initial confidence level and confidence adjustment coefficient of each acoustic pulse signal at each target location, the final confidence level of each acoustic pulse signal at the target location is determined.
[0012] Furthermore, the step of filtering credible sonar signals from all acoustic pulse signals at the target location based on the final confidence level includes: The final confidence level of each acoustic pulse signal at each target location is compared with a threshold. Acoustic pulse signals that are greater than or equal to the threshold are recorded as the reliable sonar signals at each target location.
[0013] The present invention has the following beneficial effects: By acquiring multiple acoustic pulse signals at the same target location, multiple depth data corresponding to that target location are obtained, and the impact of thermocline interference on each target location is analyzed. Simultaneously, time-series analysis of each acoustic pulse signal at each target location is performed to determine the impact of broadening nodes on each pulse signal. Furthermore, by combining the impact of thermocline interference and broadening nodes on each target location, the final confidence level of each acoustic pulse signal at the target location is comprehensively determined. Finally, reliable sonar signals are selected from all acoustic pulse signals at the target location to reduce the influence of interfering sonar signals, and based on these reliable sonar signals, more accurate underwater ship positioning is achieved. Attached Figure Description
[0014] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0015] Figure 1 A flowchart illustrating the steps of an underwater sonar positioning method for a ship, provided as an embodiment of the present invention; Figure 2 This is a flowchart illustrating the steps for calculating the temperature jump interference coefficient at each target location, as provided in one embodiment of the present invention. Detailed Implementation
[0016] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of an underwater sonar positioning method and system for ships proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.
[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0018] The following description, in conjunction with the accompanying drawings, details a specific scheme for an underwater sonar positioning method and system for ships provided by the present invention.
[0019] Please see Figure 1 The diagram illustrates a flowchart of an underwater sonar positioning method for ships according to an embodiment of the present invention, the method comprising: Step S1: Obtain the acoustic pulse signals received by the ship from multiple distributed sonar buoys targeting the same target location, and calculate multiple depths corresponding to the target location based on each acoustic pulse signal.
[0020] Multiple sonar transmitters are deployed in the target area where sonar positioning is required, and they emit sound wave pulse signals of different frequencies. The sound wave pulse signals of the target area are received by sonar receivers, so that the depth of the target position relative to each sonar transmitter can be calculated.
[0021] It should be noted that, based on the spatiotemporal synchronization protocol or preliminary beamforming scan, acoustic pulse signals falling into the same spatial grid are classified as acoustic pulse signals corresponding to the same target location.
[0022] It should be noted that the target location is not the location already obtained through positioning, but refers to the target source detected by distributed sonar.
[0023] It should be noted that, compared with the traditional single-sonar localization method, this multi-sonar localization method can effectively suppress noise, reverberation and multipath contamination through spatial diversity, and the ensemble solution can reduce the dependence on the shape of the echo pulse.
[0024] In one specific implementation of this invention, acquiring acoustic pulse signals received by the ship from multiple distributed sonar buoys targeting the same target location includes: Step S11: Obtain the multi-channel digital signal sequence of echo information through the signal receiving array at the bottom of the ship.
[0025] The bottom of the ship is equipped with a receiving hydrophone array (such as a towed linear array or a side array), which can convert the received sound pressure signal into an electrical signal. After being pre-amplified, filtered and converted into a high-speed analog-to-digital signal by the receiver, a multi-channel digital signal sequence containing echo information can be obtained.
[0026] Step S12: Based on the array geometry and the pre-calculated time delay and weighting value of the beam pointing, the multi-channel digital signal sequence is superimposed in phase to obtain the processed echo information.
[0027] It should be noted that the processing based on multi-channel digital signal sequences utilizes the spatial characteristics of the hydrophone array. Through precise time delay compensation, signals from a specific direction are aligned (in phase) in each channel, and then coherently superimposed after weighted adjustment. This synchronously enhances the signal energy in the target direction, while noise and interference from other directions are suppressed because they cannot be aligned. Ultimately, this significantly improves the signal-to-noise ratio and spatial resolution of the output signal, forming a highly directional beam that enables effective detection and accurate direction finding of weak echoes.
[0028] Therefore, the process of performing in-phase superposition processing on multi-channel digital signal sequences to obtain processed echo information is existing technology, and will not be described in detail in this embodiment.
[0029] Step S13: Extract effective signals from the processed echo information to obtain the acoustic pulse signal of each sonar buoy for each target location.
[0030] It should be noted that noise interference exists in the processed echo information. Matched filtering is used to utilize the known transmitted signal waveform (i.e., the transmitted signal waveform at each position) as a template. Cross-correlation is used to perform optimal filtering of the acoustic pulse signal at each target position in the time dimension, so that the pulse energy is concentrated into a sharp peak at a specific time point. This further compresses the signal bandwidth, improves the time resolution, and maximizes the output signal-to-noise ratio. Finally, the echo pulses submerged in noise are transformed into acoustic pulse signals that are easy to detect and accurately timed, providing a reliable basis for subsequent target detection and parameter estimation.
[0031] The process of using matched filtering to process the echo information and obtain the acoustic pulse signal at each location is an existing technology and will not be described in detail here.
[0032] Based on the acoustic pulse signals at the target location, the depth of the target location is calculated using echo ranging, thereby obtaining multiple depths corresponding to each target location (i.e., each acoustic pulse signal at the target location corresponds to a depth).
[0033] It should be noted that echo ranging is an existing technology and will not be elaborated upon here.
[0034] Step S2: Calculate the temperature jump interference coefficient for each target location based on the depth differences between multiple depths corresponding to each target location.
[0035] Underwater, water is divided into surface water and bottom water. Surface water is heated by solar radiation and cooled by evaporation, resulting in greater temperature variations. Bottom water, primarily influenced by ocean currents and subsurface currents, maintains a relatively constant temperature. The area between the surface and bottom water is called the thermocline. If the sound source and target are located on opposite sides of the thermocline, sound waves will experience strong refraction and energy loss as they pass through it. This refraction will also deflect downward-probing sound waves to other target points and the sea surface. Consequently, the acquired sound signal will contain not only the sound pulses emitted by the transmitter but also those reflected from other interfaces. This results in a mixture of sound pulses of other frequencies—mixed sound pulses with frequency and phase shifts—causing pulse broadening. Therefore, the sound pulse signal acquired for each target location will be affected by this pulse broadening phenomenon.
[0036] It should be noted that pulse broadening refers to the phenomenon where multiple phase sound pulses are considered as a single sonar pulse, which is emitted instantaneously but becomes a sequence of pulses that are spaced out in time and arrive sequentially, ultimately leading to differences in sonar results.
[0037] In one specific implementation of this invention, such as Figure 2 As shown, the temperature jump disturbance coefficient at each target location is calculated, including: Step S21: For all acoustic pulse signals at each target location, calculate the degree of dispersion based on the time length of each acoustic pulse signal to determine the pulse phenomenon performance at each target location.
[0038] For the several acoustic pulse signals acquired at each target location, the more discrete the time lengths of the several acoustic pulse signals, the greater the influence of pulse broadening phenomenon in the process.
[0039] Based on each acoustic pulse signal at each target location, the standard deviation of the time length of all acoustic pulse signals is calculated. This standard deviation is used to characterize the dispersion of the time length of the acoustic pulse signals. The standard deviation is then normalized by a maximum and minimum value, and the result of the normalization is used as the pulse phenomenon performance of each target location.
[0040] It should be noted that the maximum and minimum values in the maximum-minimum normalization are based on the statistical data within the historical period, rather than just the sample from the current single sampling.
[0041] Step S22: For each acoustic pulse signal at each target location, calculate the degree of dispersion based on the depth corresponding to each acoustic pulse signal, and determine the depth measurement deviation at each target location; For the several acoustic pulse signals acquired at each target location, the more inconsistent the depths corresponding to the several acoustic pulse signals, the greater the impact of the acoustic pulse signals on the reflection caused by the thermocline during the process, that is, the greater the impact of the thermocline interference on each target location. Based on each acoustic pulse signal at each target location, the standard deviation of the depth corresponding to all acoustic pulse signals is calculated. This standard deviation is used to characterize the dispersion of the depth corresponding to the acoustic pulse signal. The standard deviation is then normalized by a minimum and maximum value, and the result of the normalization is used as the depth measurement deviation for each target location.
[0042] It should be noted that the maximum and minimum values in the maximum-minimum normalization are based on statistical data within historical periods.
[0043] Step S23: Determine the temperature jump interference coefficient for each target location based on the pulse phenomenon performance and depth measurement deviation at each target location.
[0044] Based on the pulse phenomenon reflected by the duration of several acoustic pulse signals and the influence of the thermocline reflected by the corresponding depth of several acoustic pulse signals, the two can be combined to consider the degree of interference at each target location when acquiring acoustic pulse signals.
[0045] The pulse phenomenon performance at each target location is multiplied by the depth measurement deviation, and then normalized to the maximum and minimum values. The normalized result is used as the temperature jump interference coefficient for each target location.
[0046] It should be noted that the maximum and minimum values in the maximum-minimum normalization are based on the statistical data within the historical period, rather than just the sample from the current single sampling.
[0047] Step S3: Perform time-series analysis on each acoustic pulse signal at each target location to determine the initial reliability of each acoustic pulse signal at each target location.
[0048] Because of the density difference between two water layers with different temperatures, density creates a temperature interface. When a sonar signal passes through this interface, it undergoes both refraction and reflection. When the seabed is sufficiently deep, multiple thermoclines may exist. Combined with the refraction at these thermoclines, multiple acoustic pulse signals will be received. The order of these acoustic pulse signals is as follows: the sound wave arriving directly or via refraction arrives first, the sound wave arriving after one reflection arrives slightly later, and the sound wave arriving after multiple reflections arrives last. Therefore, the first sonar signal received has the highest purity. However, the purity of sonar signals from different directions will vary due to the angle of incidence and the underwater structure.
[0049] In one specific implementation of this invention, determining the initial reliability of each acoustic pulse signal at each target location includes: Step S31: Perform time-series analysis on each acoustic pulse signal at the target location to determine several broadening nodes in each acoustic pulse signal at the target location.
[0050] The pulse broadening phenomenon that occurs in the timing of each acoustic pulse signal at the target location alters the waveform of the acoustic pulse signal, causing a sudden change in the acoustic amplitude and resulting in interference. Therefore, in order to quantify the reliability of each acoustic pulse signal at each target location, the broadening nodes in each acoustic pulse signal at the target location are first identified.
[0051] In one specific implementation of this invention, time-series analysis is performed on each acoustic pulse signal at the target location to determine several broadening nodes in each acoustic pulse signal at the target location, including: Step S311: Obtain the pre-segmented sonar signal of each target location's acoustic pulse signal at each time step.
[0052] Specifically, for each acoustic pulse signal at each target location, all signal data prior to each moment of each acoustic pulse signal are extracted as the pre-segmented sonar signal for each moment.
[0053] It should be noted that at the starting point of the acoustic pulse signal (i.e., t=0), to avoid the situation of having no preceding data, a minimum calculation window is preset. The determination of the preceding segmented sonar signal for each time moment starts from the minimum calculation window. At the same time, the determination of the minimum calculation window can be based on the length of the acoustic pulse signal, and there is no limitation here. For example, the minimum calculation window can be the amount of data for 10 time moments.
[0054] Step S312: Perform frequency domain conversion processing on the pre-segmented sonar signal to determine the number of effective frequency components of the pre-segmented sonar signal.
[0055] It should be noted that: for each acoustic pulse signal, the pre-segmented sonar signal at each moment is processed by Fourier transform to obtain a frequency spectrum, and the number of effective frequency components with amplitudes greater than a preset background noise threshold is counted. Specifically, acoustic pulse signals can be collected under the same environmental conditions for a period of time (e.g., 10 minutes). Fourier transform is performed on the sonar signal at each moment to obtain the spectrum. Then, all spectral data (i.e., the amplitudes of all frequency points at all moments) are sorted from smallest to largest, and the 95th percentile value is selected as the preset background noise threshold.
[0056] Step S313: Based on the number of effective frequency components of the preceding segmented sonar signal of each acoustic pulse signal at the target location at each time step and the change in acoustic amplitude of each acoustic pulse signal between adjacent time steps, determine the preceding purity of each acoustic pulse signal at the target location at each time step.
[0057] For each acoustic pulse signal at each target location, the pre-segmented sonar signal at each moment is affected by interference. This interference includes not only background noise (i.e., the greater the background noise interference, the larger the effective frequency component of the pre-segmented sonar signal at each moment; "effective" here does not refer to usable data, but rather to frequency components with excessively high amplitude that should be given extra attention, i.e., strong noise interference), but also pulse broadening interference (i.e., the greater the pulse broadening interference, the greater the change in acoustic amplitude between adjacent moments). Specifically, pulse broadening interference occurs because it alters the waveform of the acoustic pulse signal, causing a sudden change in acoustic amplitude. Even if the phase deviation between the reflected acoustic pulse signal and the pure acoustic pulse signal is a complete cycle, the change in sound signal energy will still result in a difference in acoustic amplitude. Therefore, the degree of interference from pulse broadening can be characterized by the change in acoustic amplitude between adjacent moments for each acoustic pulse signal.
[0058] It should be noted that, for each acoustic pulse signal at each target location, the preceding segmented sonar signal at each moment is simultaneously affected by background noise and pulse broadening, thus serving as the basis for analyzing the preceding purity of each acoustic pulse signal at the target location. Furthermore, the calculation of the preceding purity of each acoustic pulse signal at each moment at the target location primarily focuses on the microscopic fluctuations of the acoustic pulse signal. This is because, within a normally smooth acoustic pulse signal, if a large number of high-frequency components (clutter) and drastic amplitude jumps (glitches) occur, the preceding purity of the acoustic pulse signal will be low.
[0059] Specifically, the number of effective frequency components of the pre-segmented sonar signal of each acoustic pulse signal at the target location at time t is multiplied by the absolute value of the difference in acoustic amplitude between each acoustic pulse signal at time t and time t-1. The negative of the multiplication result is substituted into the exponential function exp() for normalization. The normalized result (the value of the exponential function) is used as the pre-purity of each acoustic pulse signal at the target location at time t.
[0060] Step S314: Based on the pre-purity of each acoustic pulse signal at the target location at each moment, determine several broadening nodes in each acoustic pulse signal at the target location.
[0061] The appearance of a broadening node causes a sudden change in the acoustic amplitude, which will affect the magnitude of the preceding purity of each acoustic pulse signal at the target location at each moment. By analyzing the difference between the preceding purity of each acoustic pulse signal at the target location at each moment and the preceding purity at the previous moment, the broadening nodes contained in each acoustic pulse signal at the target location can be screened based on the degree of difference.
[0062] In one specific implementation of this invention, the method for determining several broadening nodes in the acoustic pulse signals at the target location based on the pre-purity of each acoustic pulse signal at the target location at each moment includes: First, based on the pre-purity of each acoustic pulse signal at the target location at each moment and its pre-purity at adjacent moments, the difference in pre-purity of each acoustic pulse signal at the target location at each moment is determined.
[0063] It should be noted that: the absolute value of the difference between the pre-purity of each acoustic pulse signal at the target location at time t and the pre-purity at time t-1 is taken as the difference of the pre-purity of each acoustic pulse signal at the target location at each time.
[0064] Secondly, based on the prior purity of each acoustic pulse signal at the target location at each moment several moments prior to each moment, a reference value for the prior purity of each acoustic pulse signal at the target location at each moment is determined.
[0065] It should be noted that the differences in the prior purity of each acoustic pulse signal at the target location at each moment are accumulated and averaged, and this average is used as the reference value for the prior purity of each acoustic pulse signal at the target location at each moment.
[0066] Finally, based on the difference in pre-purity of each acoustic pulse signal at the target location at each moment and the pre-purity benchmark value, several broadening nodes in the time sequence of each acoustic pulse signal at the target location are determined.
[0067] It should be noted that: if the difference in the pre-purity of each acoustic pulse signal at the target location at time t is greater than its pre-purity reference value, then a secondary comparison is performed, that is, the difference in the pre-purity of each acoustic pulse signal at the target location at time t is compared with its pre-purity reference value (the minimum value is added to the denominator). (For example, a value of 0.001 to avoid a denominator of 0). If this ratio is greater than the deviation coefficient, then time t is considered a broadening node; otherwise, if the above conditions are not met simultaneously, time t is not considered a broadening node. Based on long-term experience in dividing broadening nodes, the deviation coefficient can be preset to 1.1. Simultaneously, the same operation is performed on all subsequent times to obtain several broadening nodes for each acoustic pulse signal in time sequence.
[0068] Step S32: Determine the initial confidence level of each acoustic pulse signal at each target location based on the consistency of the broadening nodes in time among multiple acoustic pulse signals at the target location.
[0069] For multiple acoustic pulse signals at a target location, since the sonar transmitters are not located in the same position, there will be azimuth differences between the transmitters and the target location. This will cause differences in the refraction and reflection angles of the acoustic pulse signals as they pass through the thermocline, thus affecting the timing of the broadening nodes in the multiple acoustic pulse signals at the target location. The greater the difference in the timing of the broadening nodes among the multiple acoustic pulse signals at each target location, the lower the initial reliability of each acoustic pulse signal at that target location.
[0070] In one specific implementation of this invention, the method for obtaining the initial reliability of each acoustic pulse signal at each target location includes: Step S321: Based on all acoustic pulse signals at each target location, select any one acoustic pulse signal as the standard acoustic pulse signal.
[0071] Step S322: Using the length of the standard acoustic pulse signal as a reference, perform fixed-length processing on all other acoustic pulse signals to obtain several fixed-length processed acoustic pulse signals for each target position.
[0072] It should be noted that, due to the influence of reflection factors, the signal lengths of different acoustic pulse signals at each target location will vary. Therefore, it is necessary to perform equal-length processing on the different acoustic pulse signals at each target location. That is, for the acoustic pulse signals other than the standard acoustic pulse signal at each target location, the acoustic pulse signals are linearly lengthened or shortened proportionally, resulting in several fixed-length processed acoustic pulse signals for each target location. Furthermore, for the broadened nodes in the other acoustic pulse signals before processing, the time points corresponding to these broadened nodes are determined in the processed acoustic pulse signals. These time points are then used as broadened nodes in the amplified acoustic pulse signals and participate in the subsequent clustering process.
[0073] It should be noted that the equal-length processing of different acoustic pulse signals at each target location is to measure the consistency of the broadened feature distribution in different acoustic pulse signals at the target location on a unified time scale. Therefore, all signals are mapped onto a time axis of standard length.
[0074] Step S323: Cluster all broadened nodes in the standard acoustic pulse signal and all fixed-length processed acoustic pulse signals to obtain several clusters.
[0075] It should be noted that: all broadened nodes in the standard acoustic pulse signal and all fixed-length processed acoustic pulse signals are clustered based on temporal differences using hierarchical clustering or density clustering algorithms, thereby obtaining several clusters.
[0076] Step S324: Based on the number of broadened nodes in the standard acoustic pulse signal and the number of clusters to which each broadened node belongs in the standard acoustic pulse signal, determine the dispersion of broadened nodes in each standard acoustic pulse signal at each target location.
[0077] It should be noted that the number of clusters to which each broadened node in a standard acoustic pulse signal belongs reflects the number of thermoclines in the water, because the water layer structure corresponding to the same target location is relatively consistent. If the same cluster contains two or more broadened nodes from the same standard acoustic pulse signal, it indicates that the standard acoustic pulse signal may have been affected by interference or complex structures during transmission, resulting in multiple refractions. This leads to multiple segments of abrupt changes in the received acoustic pulse signal, and the more interference, the lower the reliability. Conversely, the fewer the number of broadened nodes in the standard acoustic pulse signal and the more clusters to which each broadened node belongs, the greater the dispersion of broadened nodes in each standard acoustic pulse signal at each target location, meaning the standard acoustic pulse signal is less affected by interference.
[0078] Specifically, the number of clusters to which the broadened nodes belong in each standard acoustic pulse signal at each target location is compared with the total number of broadened nodes in each standard acoustic pulse signal at each target location (with a minimum value added to the denominator). (e.g., 0.001, to avoid a denominator of 0), this ratio is used as the broadening node dispersion distribution in each standard acoustic pulse signal at each target location.
[0079] Step S325: Based on the time difference between each broadening node in the standard acoustic pulse signal and other broadening nodes in its cluster, determine the temporal dispersion of the broadening nodes in each standard acoustic pulse signal at each target location.
[0080] It should be noted that, due to the simple underwater structure, the occurrence time of the broadened nodes in the clusters caused by scattering and refraction should be relatively consistent. Therefore, by comparing the time difference between each broadened node in the standard acoustic pulse signal and the cluster center of the cluster to which each broadened node belongs, the greater the time difference, the more dispersed the occurrence of each broadened node from other broadened nodes in its cluster, and the greater the interference affecting the standard acoustic pulse signal.
[0081] Specifically, the difference between each broadened node in the standard acoustic pulse signal and the mean of other broadened nodes in its cluster is calculated, and the absolute value is taken as the time difference. The time differences corresponding to all broadened nodes in the standard acoustic pulse signal are accumulated and averaged, and then normalized to the maximum and minimum values. This gives the temporal dispersion of the broadened nodes in each standard acoustic pulse signal at each target location.
[0082] It should be noted that the maximum and minimum values in the maximum-minimum normalization are based on the statistical data within the historical period, rather than just the sample from the current single sampling.
[0083] Step S326: Based on the spread node dispersion degree and the spread node temporal dispersion degree, determine the initial confidence of each standard acoustic pulse signal at each target location.
[0084] The temporal consistency difference of the broadened nodes is characterized by the dispersion degree of the broadened nodes and the temporal dispersion degree of the broadened nodes in each standard acoustic pulse signal at each target location, thereby jointly determining the initial confidence of each standard acoustic pulse signal at each target location.
[0085] Specifically, the difference between the distribution dispersion of the broadened nodes and 1 is taken as the absolute value. This absolute value is then multiplied by the temporal dispersion of the broadened nodes. The result of the multiplication is then inversely multiplied and substituted into the exponential function exp() for normalization. The normalized result (the value of the exponential function) is used as the initial confidence level of each standard acoustic pulse signal at each target location.
[0086] Step S4: Based on the initial confidence level and temperature jump interference coefficient of each target location, determine the final confidence level of each acoustic pulse signal at the target location.
[0087] By analyzing the thermocline interference coefficient at each target location, the interference effect of the thermocline layer on the acoustic pulse signal is characterized. Furthermore, by analyzing the initial confidence level of each target location, the interference effect suffered by each standard acoustic pulse signal itself is reflected. Combining the two, the final confidence level of each acoustic pulse signal at the target location is determined.
[0088] In one specific implementation of this invention, determining the final confidence level of each acoustic pulse signal at the target location includes: Step S41: Based on the temperature jump interference coefficient of each target location, determine the confidence adjustment coefficient of each acoustic pulse signal at each target location.
[0089] The absolute value of the difference between the temperature jump interference coefficient at each target location and 1 is used as the confidence adjustment coefficient of the acoustic pulse signal at each target location.
[0090] Step S42: Based on the initial confidence level and confidence adjustment coefficient of each acoustic pulse signal at each target location, determine the final confidence level of each acoustic pulse signal at the target location.
[0091] Specifically, the initial confidence level of each standard acoustic pulse signal at each target location is multiplied by the confidence adjustment coefficient of the acoustic pulse signal at each target location, and then normalized to the maximum and minimum values to determine the final confidence level of each acoustic pulse signal at each target location.
[0092] It should be noted that the maximum and minimum value normalization performed here is based on the result of multiplying the initial confidence of each standard acoustic pulse signal at all target locations by the confidence adjustment coefficient of the acoustic pulse signal at each target location, and then selecting the maximum and minimum values for maximum and minimum value normalization.
[0093] Step S5: Based on the final confidence level, filter reliable sonar signals from all acoustic pulse signals at the target location, and achieve underwater positioning of the ship based on the reliable sonar signals.
[0094] The final confidence level of each acoustic pulse signal based on the target location can be compared with a threshold to select reliable sonar signals, which can then be used as data for underwater positioning of the ship, thereby reducing the influence of interfering sonar signals.
[0095] A preset confidence threshold is set. It should be noted that the value of this confidence threshold can be determined by statistically analyzing the final confidence of each acoustic pulse signal at the target location. There is no limitation here; for example, the value of this confidence threshold can be set to 0.5.
[0096] Specifically, the final confidence level of each acoustic pulse signal at each target location is compared with a threshold, and acoustic pulse signals that are greater than or equal to the threshold are recorded as the reliable sonar signals at each target location.
[0097] It should be noted that if the current underwater environment is harsh, causing the confidence levels of all acoustic pulse signals to be below the confidence threshold, then the N acoustic pulse signals with the highest final confidence levels at the target location should be selected. The value of N can be determined by statistically analyzing the final confidence levels of each acoustic pulse signal at the target location; there is no limitation here, but a value of 5 can be set for N.
[0098] Based on the reliable sonar signal at each target location, the acoustic corner points of all real sonars are found by solving the geometric surface, thereby directly obtaining the three-dimensional coordinates of that location and realizing underwater positioning of the ship.
[0099] It should be noted that the method of underwater positioning of ships based on reliable sonar signals is existing technology and will not be elaborated on further here.
[0100] It should be noted that: by considering the influence of factors such as thermocline and pulse broadening phenomenon, a reliable sonar signal for the target location is selected from several acoustic pulse signals based on the target location, thereby reducing the influence of interfering sonar signals and improving the accuracy of underwater positioning of ships.
[0101] Based on the same inventive concept, embodiments of the present invention also provide an underwater sonar positioning system for ships. The control system includes: a memory, a processor, and computer program code stored in the memory and running on the processor, wherein when the processor executes the computer program code, the system can perform any of the aforementioned underwater sonar positioning methods for ships.
[0102] In this embodiment of the invention, the system can be divided into functional modules according to the above method example. For example, each module can correspond to a separate functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware. It should be noted that the module division in this embodiment is illustrative and only represents one logical functional division. In actual implementation, there may be other division methods.
[0103] Based on the same inventive concept, embodiments of the present invention also provide a computer program product, which includes: computer program code, which, when run on a computer, causes the computer to execute any of the aforementioned underwater sonar positioning methods for ships.
[0104] Based on the same inventive concept, embodiments of the present invention also provide a computer-readable storage medium storing computer program code, which, when executed on a computer, causes the computer to perform any of the aforementioned underwater sonar positioning methods for ships.
[0105] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.
[0106] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.
Claims
1. A method for underwater sonar positioning of ships, characterized in that, The method includes: The ship receives acoustic pulse signals from multiple distributed sonar buoys targeting the same target location, and calculates multiple depths corresponding to the target location based on each acoustic pulse signal. The temperature jump interference coefficient for each target location is calculated based on the depth differences between multiple depths corresponding to each target location. Time-series analysis is performed on each acoustic pulse signal at each target location to determine the initial reliability of each acoustic pulse signal at each target location; Based on the initial confidence level and temperature jump interference coefficient of each target location, the final confidence level of each acoustic pulse signal at the target location is determined. Based on the final confidence level, reliable sonar signals are selected from all acoustic pulse signals at the target location, and underwater positioning of the ship is achieved based on the reliable sonar signals. Acquire acoustic pulse signals received by the ship from multiple distributed sonar buoys targeting the same location, including: A multi-channel digital signal sequence for acquiring echo information is obtained through a signal receiving array at the bottom of the ship. Based on the array geometry and beam pointing, the pre-calculated time delay and weighting values are used to perform in-phase superposition processing on the multi-channel digital signal sequence to obtain the processed echo information. Effective signal extraction is performed on the processed echo information to obtain the acoustic pulse signal of each sonar buoy for each target location; The calculation of the temperature jump interference coefficient at each target location includes: For all acoustic pulse signals at each target location, the degree of dispersion is calculated based on the time length of each acoustic pulse signal to determine the pulse phenomenon performance at each target location. For each acoustic pulse signal at each target location, the degree of dispersion is calculated based on the depth corresponding to each acoustic pulse signal, and the depth measurement deviation at each target location is determined. Based on the pulse phenomenon performance and depth measurement deviation at each target location, the temperature jump interference coefficient at each target location is determined.
2. The underwater sonar positioning method for ships according to claim 1, characterized in that, Determine the initial confidence level of each acoustic pulse signal at each target location, including: Time-series analysis is performed on each acoustic pulse signal at the target location to determine several broadening nodes in each acoustic pulse signal at the target location. The initial confidence level of each acoustic pulse signal at each target location is determined based on the consistency of the broadening nodes in time among multiple acoustic pulse signals at the target location.
3. The underwater sonar positioning method for ships according to claim 2, characterized in that, Determine several broadening nodes in each acoustic pulse signal at the target location, including: Acquire the pre-segmented sonar signal at each target location using the acoustic pulse signal at each moment. Based on the aforementioned segmented sonar signal, frequency domain conversion processing is performed to determine the number of effective frequency components of the aforementioned segmented sonar signal. Based on the number of effective frequency components of the preceding segmented sonar signal of each acoustic pulse signal at the target location at each time step and the change in acoustic amplitude of each acoustic pulse signal between adjacent time steps, the preceding purity of each acoustic pulse signal at the target location at each time step is determined. Based on the pre-purity of each acoustic pulse signal at the target location at each time step, several broadening nodes in each acoustic pulse signal at the target location are determined.
4. The underwater sonar positioning method for ships according to claim 3, characterized in that, Based on the pre-purity of each acoustic pulse signal at the target location at each time step, several broadening nodes in each acoustic pulse signal at the target location are determined, including: Based on the pre-purity of each acoustic pulse signal at the target location at each time step and its pre-purity at adjacent time steps, the difference in pre-purity of each acoustic pulse signal at the target location at each time step is determined. Based on the difference in the preceding purity of each acoustic pulse signal at the target location at each time step, a baseline value for the difference in preceding purity of each acoustic pulse signal at the target location at each time step is determined. Based on the difference in pre-purity of each acoustic pulse signal at the target location at each moment and the pre-purity benchmark value, several broadening nodes in the time sequence of each acoustic pulse signal at the target location are determined.
5. The underwater sonar positioning method for ships according to claim 2, characterized in that, The initial reliability of each acoustic pulse signal at the target location is determined based on the temporal consistency of the broadening nodes in multiple acoustic pulse signals at the target location, including: Based on all acoustic pulse signals at each target location, any one acoustic pulse signal is selected as the standard acoustic pulse signal. Using the length of the standard acoustic pulse signal as a reference, all other acoustic pulse signals are processed to a fixed length to obtain several fixed-length processed acoustic pulse signals for each target position. Clustering is performed on all broadened nodes in the standard acoustic pulse signal and all fixed-length processed acoustic pulse signals to obtain several clusters; Based on the number of broadened nodes in the standard acoustic pulse signal and the number of clusters to which each broadened node belongs, the dispersion distribution of broadened nodes in each standard acoustic pulse signal at each target location is determined. Based on the time difference between each broadening node in the standard acoustic pulse signal and other broadening nodes in its cluster, the temporal dispersion of the broadening nodes in each standard acoustic pulse signal at each target location is determined. Based on the dispersion degree of the broadened nodes and the temporal dispersion degree of the broadened nodes, the initial confidence level of each standard acoustic pulse signal at each target location is determined.
6. The underwater sonar positioning method for ships according to claim 1, characterized in that, The determination of the final confidence level of each acoustic pulse signal at each target location, based on the initial confidence level and temperature jump interference coefficient at each target location, includes: Based on the temperature jump interference coefficient at each target location, the confidence adjustment coefficient for each acoustic pulse signal at each target location is determined; Based on the initial confidence level and confidence adjustment coefficient of each acoustic pulse signal at each target location, the final confidence level of each acoustic pulse signal at the target location is determined.
7. The underwater sonar positioning method for ships according to claim 1, characterized in that, The step of filtering reliable sonar signals from all acoustic pulse signals at the target location based on the final confidence level includes: The final confidence level of each acoustic pulse signal at each target location is compared with a threshold. Acoustic pulse signals that are greater than or equal to the threshold are recorded as the reliable sonar signals at each target location.
8. An underwater sonar positioning system for ships, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is executed by the processor, it implements the steps of an underwater sonar positioning method for a ship as described in any one of claims 1-7.