Acoustic CT three-dimensional imaging and coordinate positioning device and method for underwater target

Abstract

The invention provides an underwater target acoustic CT three-dimensional imaging and coordinate positioning device and method, and the method comprises the steps: laying a plurality of active sound sources and hydrophones in a target water area to form an active sound source array and a hydrophone array, and carrying out the acoustic CT three-dimensional imaging and coordinate positioning according to the underwater target detection distance and imaging spatial resolution required by a task; the method comprises the following steps: selecting sound sources of different sound source levels, setting time synchronization of a plurality of sound sources and a hydrophone array, sequentially starting the sound sources according to a preset sequence, synchronously recording direct sound wave and reflected / scattered sound wave signals collected by each hydrophone, and then obtaining a three-dimensional shape image and coordinate positioning information of a target in water by using an acoustic CT three-dimensional reconstruction algorithm. Based on the scheme of the invention, the three-dimensional shape image and coordinate positioning information of the underwater target can be directly obtained, rapid early warning, identification qualification and space coordinate positioning of the underwater target are realized, the detection and identification capability of the current underwater target is greatly improved, the bottleneck in the prior art is broken through, and the method has a good application prospect.

Description

Technical Field

[0001] The present application relates to the technical field of real-time detection of dynamic targets in water, and in particular to a device and method for acoustic CT three-dimensional imaging and coordinate positioning of targets in water. Background Art

[0002] In the current underwater acoustic detection technology, the more mature imaging sonars can be divided into two categories: side-scan sonars and fan-scan sonars. The detection direction of fan-scan sonars is the same as the navigation direction of the carrier ship. It detects the waters in front of the ship and is mainly used in underwater target detection, marine obstacle avoidance navigation and other fields. Fan-scan sonars include single-beam mechanical scanning sonars and multi-beam electronic scanning sonars. Single-beam sonars use a single beam to detect the target area through a mobile sound source and mechanical scanning. They are mainly used for basic underwater target measurement. The single-beam sonar has a simple device structure and low cost, but the mechanical scanning structure limits its detection efficiency and cannot achieve real-time imaging and imaging of moving targets. Multi-beam sonars emit multiple sound beams through a sound source array, which can simultaneously detect multi-point depth information within a certain range and are suitable for complex underwater terrain mapping. However, its equipment is relatively complex and costly. The detection direction of side-scan sonar is perpendicular to the navigation direction of the carrier ship. It is often used in fields such as seabed topography mapping, underwater archaeology and resource exploration. It can generate high-definition underwater two-dimensional images, but its main disadvantage is that it is easily interfered by seabed echoes. Synthetic aperture sonar is an advanced side-scan sonar technology, and its principle is borrowed from synthetic aperture radar in optical imaging. Synthetic aperture sonar achieves the imaging effect of a large-size array by using a smaller physical aperture and a longer signal accumulation time. It can greatly improve the resolution of two-dimensional images and is suitable for deep-sea exploration and detection in complex environments, but it has high requirements for data processing capabilities and navigation system accuracy.

[0003] The various types of sonar technologies currently in use have limitations. For target detection, the main problem with existing technologies is that they can only produce two-dimensional images, and information in one spatial dimension is missing, resulting in information ambiguity for target detection. Secondly, underwater acoustic signals experience signal attenuation during propagation, and are greatly affected by complex water environments such as water flow velocity, density, seabed topography, and surface echoes, making long-distance and high-precision detection difficult. Even for targets within the detection range, the target attributes in the existing technology detection information are fuzzy, and it is impossible to achieve three-dimensional morphological imaging of the target, and it is impossible to accurately obtain the three-dimensional coordinate positioning of the target. Therefore, it is impossible to achieve rapid and effective identification and early warning of underwater targets in the marine environment. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the purpose of this application is to propose a device and method for acoustic CT three-dimensional imaging and coordinate positioning of underwater targets. In view of the low accuracy and difficulty in identifying target attributes of traditional underwater target acoustic detection technology, a detection array composed of active sound sources and hydrophones and an acoustic CT three-dimensional reconstruction algorithm are used to directly obtain the three-dimensional morphological image and coordinate positioning information of the underwater target, so as to achieve rapid early warning, qualitative identification and spatial coordinate positioning of the underwater target, greatly improve the current detection and identification capabilities of underwater targets, break through the bottleneck of existing technologies, and have good application prospects.

[0006] To achieve the above-mentioned purpose, the first embodiment of the present application proposes a device for acoustic CT three-dimensional imaging and coordinate positioning of underwater targets, including:

[0007] Active sound source array, used for remote controlled sound generation or timed sound generation;

[0008] A hydrophone array, used to receive acoustic data, wherein the acoustic data includes direct waves from the active sound source array and scattered wave signals of underwater targets and water environment;

[0009] A control platform, used to control the active sound source array and the hydrophone array, and collect the sound emission time and three-dimensional spatial coordinate information of the active sound source array and the acoustic data, time information and three-dimensional spatial coordinate information of the hydrophone array;

[0010] The CT image reconstruction unit is used to perform data analysis and CT image reconstruction of the underwater target according to the data collected by the control platform to obtain the final three-dimensional morphological image and spatial coordinates of the target.

[0011] Optionally, the active sound source array includes:

[0012] Multiple active sound sources for emitting sound signals in a preset configuration sequence;

[0013] The three-dimensional space coordinate measurement and positioning unit bound to each active sound source is used to obtain the three-dimensional space coordinate information of each active sound source and send it to the control platform.

[0014] Optionally, the hydrophone array comprises:

[0015] A plurality of hydrophones, used to receive direct waves from the active sound source array and scattered wave signals from underwater targets and water environment, wherein the hydrophones are arranged in a towed sonar array or a hydrophone array dispersedly arranged in the water;

[0016] The three-dimensional space coordinate measuring and positioning unit bound to each hydrophone is used to obtain the three-dimensional space coordinate information of each hydrophone and send it to the control platform.

[0017] Optionally, the control platform includes:

[0018] A detection program setting unit, used to set the sounding order and sounding interval of each of the active sound sources, and the data collection frequency of each of the hydrophones;

[0019] A time synchronization unit, used to set the time synchronization between each of the active sound sources and each of the hydrophones;

[0020] A remote communication unit is used to realize remote communication between the control platform and the active sound source array and the hydrophone array.

[0021] Optionally, the CT image reconstruction unit is used to:

[0022] The image reconstruction problem in underwater acoustic imaging is converted into a problem of solving the scattering coefficient distribution of each imaging point in the target area, and the final target three-dimensional morphological image is obtained by at least one of an underwater acoustic three-dimensional CT image analytical focusing reconstruction algorithm and an underwater acoustic three-dimensional CT image iterative reconstruction algorithm.

[0023] Optionally, the processing process of the underwater acoustic three-dimensional CT image analytical focusing reconstruction algorithm is:

[0024] Assume that at t = 0, the active sound source sends a narrow pulse signal p 0 (t), then the response of hydrophone j to active sound source i can be expressed as:

[0025]

[0026] Among them, D(x,y,z) is the attenuation coefficient, A(x,y,z) is the target scattering coefficient distribution, and Δt is the propagation time;

[0027] Calculate the position (x i ,y i ,z i The active sound source i at ) emits sound waves to the virtual focal point p, which produces echoes reaching the location (x j ,y j ,z j ) is the time Δt of the receiving element j at the position of the receiver, which is expressed as:

[0028]

[0029] Where s is the sound propagation path;

[0030] When the far-field condition is met, the propagation path is approximately a straight line, and the above formula can be rewritten as:

[0031]

[0032] Wherein, τ is the integral variable, τ = 0 means the acoustic signal is at the transmitting point, and τ = 1 means the acoustic signal is at the receiving point;

[0033] After calculating Δt, according to the sampling rate f s Calculate the sampling point sequence number and substitute it into the hydrophone data to obtain the sound pressure contribution P of the group of transmitting-receiving array elements ij at point p ij , the expression is:

[0034] P ij = ij [·f s ]

[0035] The original hydrophone data is stored in a two-dimensional matrix S, and the elements of the matrix S are ij is an array of length L, representing the L sampling points received by hydrophone j after the active sound source i emits sound waves;

[0036] Traverse the transmitting-receiving sound source combination and sum it to get the total sound pressure at point p, which is expressed as:

[0037]

[0038] Where P(x,y,z) is the total sound pressure at point p;

[0039] After normalization, the sound pressure distribution in the area reflects the relative distribution of the scattering coefficient. If there is a target in the target area, the scattering coefficient at the target position will be much larger than that of the surrounding waters, thereby completing the image reconstruction and obtaining the final three-dimensional morphological image of the target.

[0040] Optionally, the processing process of the underwater acoustic three-dimensional CT image iterative reconstruction algorithm is:

[0041] Assume a three-dimensional area with the origin O as the center of the target imaging area and the active sound source S i (x i ,y i ,z i ) and hydrophone R j (x j ,y j ,z j ) is a combination of the sound source and the hydrophone array, p(x, y, z) is any point in the target imaging area, then the echo p received by the hydrophone at time t is ij (t) can be expressed as:

[0042]

[0043] Under far-field conditions, since the attenuation of the acoustic wave inside the imaging area is negligible, the above formula can be rewritten as:

[0044]

[0045] In the formula, R 0 is the sum of the distances between the sound source and the hydrophone from the center of the imaging area O, s i and j For point p on line S i O and straight line OR j Projection distance on

[0046] Assume that the incident angle of the sound wave is θ i , the echo exit angle is θ j ,θ i and θ j It is only related to the position of the sound source and the hydrophone. When the distance between the sound source and the hydrophone is much smaller than the distance to the center of the imaging area, it can be considered that θ i = j =,s i = j =s, the expression of the echo signal can be rewritten as:

[0047]

[0048] If the pulse width Δt generated by the sound source is short enough to satisfy cΔt≤Δx, where Δx is the pixel size, the echo signal p(s,θ) under three-dimensional far-field conditions is obtained, which can be expressed as

[0049]

[0050] The formula indicates that the projection data at intervals s in the θ direction is the surface integral of the ellipsoidal surface with different focal lengths s, with a certain set of sound sources-hydrophones corresponding to the direction as the focus;

[0051] Since the projection data p(s,θ) is known, it can be calculated based on the data of the sound source-hydrophone group, and the expression is:

[0052]

[0053] The above hydroacoustic imaging model is expressed by a set of equations, which is expressed as follows:

[0054] RX=Y

[0055] In the formula, vector X represents the imaging area to be solved, x j is the value of the jth pixel. For a three-dimensional image of size x×y×z, it can be expanded layer by layer and column by column into a one-dimensional vector for processing. Its length is xyz. In the underwater acoustic imaging model, x jThe value reflects the scattering coefficient of the imaging area, Y represents the projection data, which is calculated from the data measured by the hydrophone, and R is the system response matrix, which represents the intersection area of ​​each ellipsoid surface and each cubic pixel in the imaging area;

[0056] The equation is solved by iterative solution, and the expression is:

[0057]

[0058] in

[0059]

[0060] In the formula, R i represents the i-th row of the response matrix R, λ l represents the relaxation factor of each iteration; before the iteration, the approximate three-dimensional image of the object is obtained by the analytical focusing algorithm, which is used as the initial value of the iteration to determine the position and size of the imaging area, and the scattering coefficient distribution X () As the initial value; in each iteration, by calculating θ j The pixels are corrected by the errors of all ray projections in the direction, and the final target three-dimensional morphological image is obtained after multiple iterations.

[0061] To achieve the above-mentioned purpose, the second embodiment of the present application proposes a method for underwater target acoustic CT three-dimensional imaging and coordinate positioning using any device in the first aspect, characterized in that it includes the following steps:

[0062] Setting the sounding order and sounding interval of each active sound source in the active sound source array, and the data collection frequency of the hydrophone in the hydrophone array, and maintaining the time synchronization of each active sound source and each hydrophone;

[0063] Controlling each of the active sound sources to emit sound signals in sequence according to preset settings, and sending the three-dimensional spatial coordinate information of each active sound source to the control platform;

[0064] In response to each hydrophone receiving acoustic data, the acoustic data and three-dimensional spatial coordinate information of each hydrophone are sent to a control platform, wherein the acoustic data includes direct waves from the active sound source array and scattered wave signals of underwater targets and water environment;

[0065] The control platform is controlled to send the collected data to the CT image reconstruction unit to perform data analysis and CT image reconstruction of the underwater target, so as to obtain the final three-dimensional morphological image and spatial coordinates of the target.

[0066] To achieve the above-mentioned purpose, the third aspect of the present application provides an electronic device, including: a processor, and a memory communicatively connected to the processor;

[0067] The memory stores computer-executable instructions;

[0068] The processor executes the computer-executable instructions stored in the memory to implement the method as described in any one of the first aspects above.

[0069] To achieve the above-mentioned purpose, the fourth aspect embodiment of the present application proposes a computer-readable storage medium, in which computer-readable storage medium is stored computer execution instructions, and when the computer execution instructions are executed by a processor, they are used to implement the method as described in any one of the above-mentioned first aspects.

[0070] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:

[0071] By deploying multiple active sound sources and hydrophones in the target waters to form an active sound source array and a hydrophone array, according to the underwater target detection distance and imaging spatial resolution required by the task, select sound sources of different sound source levels and set multiple sound sources and hydrophone array time synchronization, start the sound sources in sequence according to the preset order, and synchronously record the direct sound waves and reflected / scattered sound wave signals collected by each hydrophone, and then use the acoustic CT three-dimensional reconstruction algorithm to obtain the three-dimensional morphological image and coordinate positioning information of the underwater target. Based on the solution of this application, the three-dimensional morphological image and coordinate positioning information of the underwater target can be directly obtained, and the rapid early warning, identification and spatial coordinate positioning of the underwater target can be realized, which greatly improves the current detection and identification capabilities of underwater targets, breaks through the bottleneck of existing technologies, and has good application prospects.

[0072] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0074] Figure 1 It is a block diagram of a device for acoustic CT three-dimensional imaging and coordinate positioning of underwater targets according to an embodiment of the present application;

[0075] Figure 2 is a schematic diagram of the geometric relationship of underwater acoustic CT imaging according to an embodiment of the present application;

[0076] Figure 3 is a schematic diagram of a system simulation model according to an embodiment of the present application;

[0077] Figure 4 is a schematic diagram of the results of an underwater acoustic three-dimensional CT image analytical focusing reconstruction algorithm according to an embodiment of the present application;

[0078] Figure 5 is a schematic diagram of the results of an underwater acoustic three-dimensional CT image iterative reconstruction algorithm according to an embodiment of the present application;

[0079] Figure 6 It is a block diagram of an electronic device. DETAILED DESCRIPTION

[0080] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0081] The following describes an apparatus and method for acoustic CT three-dimensional imaging and coordinate positioning of an underwater target according to an embodiment of the present application with reference to the accompanying drawings.

[0082] Figure 1 is a block diagram of a device for acoustic CT three-dimensional imaging and coordinate positioning of an underwater target according to an embodiment of the present application, such as Figure 1 As shown, the device includes: an active source array 1, a hydrophone array 2, a control platform 3 and a CT image reconstruction unit 4.

[0083] In the embodiment of the present application, the active sound source array 1 is used to remotely control the sound or timed sound; the hydrophone array 2 is used to receive acoustic data, and the acoustic data includes direct waves from the active sound source array and scattered wave signals of underwater targets and water environments; the control platform 3 is used to control the active sound source array and the hydrophone array, and collect the sound emission time and three-dimensional spatial coordinate information of the active sound source array and the acoustic data, time information and three-dimensional spatial coordinate information of the hydrophone array; the CT image reconstruction unit 4 is used to perform data analysis and CT image reconstruction of underwater targets according to the data collected by the control platform, and obtain the final target three-dimensional morphological image and spatial coordinates.

[0084] In some embodiments of the present application, the active sound source array 1 includes a plurality of active sound sources and a three-dimensional space coordinate measurement and positioning unit bound to each active sound source.

[0085] Among them, multiple active sound sources are used to emit sound signals in a preset configuration order; the three-dimensional space coordinate measurement and positioning unit bound to each active sound source is used to obtain the three-dimensional space coordinate information of each active sound source and send it to the control platform.

[0086] In the embodiments of the present application, there is no specific limitation on the type of active sound source, and various types of sound sources such as electroacoustic sources and explosion sound sources can be used. In practical applications, both medium and high frequency sound sources of traditional sonar and low frequency sound sources can be used. The types of sound sources are also very wide, and imaging of the system can be achieved from acoustic-electric transducers to explosion sound sources.

[0087] In order to facilitate the description of the functions of the device of the present application, a low-frequency active sound source is selected in the subsequent embodiments for long-distance detection.

[0088] In some other embodiments of the present application, the hydrophone array 2 includes a plurality of hydrophones and a three-dimensional space coordinate measurement and positioning unit bound to each hydrophone.

[0089] Among them, multiple hydrophones are used to receive direct waves from the active sound source array and scattered wave signals from underwater targets and water environments; the three-dimensional spatial coordinate measurement and positioning unit bound to each hydrophone is used to obtain the three-dimensional spatial coordinate information of each hydrophone and send it to the control platform.

[0090] In the embodiment of the present application, there is no specific limitation on the arrangement of the hydrophones, and a towed sonar array or a hydrophone array dispersedly arranged in the water can be used.

[0091] In other embodiments of the present application, the control platform 3 includes a detection program setting unit, a time synchronization unit and a remote communication unit.

[0092] Among them, the detection program setting unit is used to set the sounding order, sounding interval and data collection frequency of each active sound source; the time synchronization unit is used to set the time synchronization of each active sound source and each hydrophone to ensure that the time reference between all components remains consistent; the remote communication unit is used to realize remote communication between the control platform and the active sound source array and hydrophone array.

[0093] It should be noted that the control platform 3 is connected to the active sound source array 1 and the hydrophone array 2 wirelessly or wired, and the control platform can be a separate device or integrated with a subsequent CT image reconstruction unit, which is not specifically limited in the present application.

[0094] Finally, the CT image reconstruction unit 4 converts the image reconstruction problem in underwater acoustic imaging into the problem of solving the distribution of scattering coefficients of each imaging point in the target area, and obtains the final target three-dimensional morphological image through at least one of the underwater acoustic three-dimensional CT image analytical focusing reconstruction algorithm and the underwater acoustic three-dimensional CT image iterative reconstruction algorithm.

[0095] Refer to the attached Figure 1 The proposed device for underwater target acoustic CT three-dimensional imaging and coordinate positioning, a typical active acoustic CT detection process is as follows:

[0096] (1) For the pre-arranged or immediately arranged sound source array and hydrophone array, set up the detection program, including the sound source sounding sequence and interval, hydrophone data collection frequency, etc., and set the time synchronization of each device.

[0097] (2) The active sound source array emits sound signals in sequence according to the settings, and sends the three-dimensional spatial coordinate information of the active sound source to the control platform; the hydrophone array starts to receive the direct wave of the sound source and the scattered wave signals from the underwater target and the water environment, and sends them together with the three-dimensional spatial coordinate information of the hydrophone to the control platform.

[0098] (3) The control platform sends the collected data information to the CT image reconstruction unit to perform data analysis and CT image reconstruction of the underwater target to obtain the final target three-dimensional morphological image and spatial coordinates.

[0099] Next, the implementation algorithm of the CT image reconstruction unit of the underwater target is described:

[0100] It can be understood that in underwater acoustic imaging detection, the propagation of sound waves satisfies the superposition principle. The echo signal of a target in three-dimensional space can be equivalent to the independent superposition of scattered waves of several point targets. The echo intensity of a point target can be described by the scattering coefficient A(x, y, z). Therefore, the image reconstruction problem in underwater acoustic imaging can be converted into the problem of solving the distribution of scattering coefficients of each imaging point in the target area. The principle is briefly described in Figure 2.

[0101] In this technology, the present application proposes two analytical focusing reconstruction algorithms and iterative reconstruction algorithms for underwater acoustic three-dimensional CT image reconstruction.

[0102] First, the principle of the underwater acoustic 3D CT image analysis and focusing reconstruction algorithm is as follows:

[0103] Assume that at t = 0, the active sound source sends a narrow pulse signal p 0 (t), then the response of hydrophone j to active sound source i can be expressed as:

[0104]

[0105] Where D(x,y,z) is the attenuation coefficient, A(x,y,z) is the target scattering coefficient distribution, and Δt is the propagation time.

[0106] It should be noted that the above formula shows that the echo signal received by the hydrophone at different times t is composed of a series of points with equal propagation time Δt. These points form an ellipsoidal surface, called an isochronous surface. The signal collected by the hydrophone can distinguish the difference in scattering coefficients between different isochronous surfaces. The signal collected by the hydrophone at a certain moment represents the surface integral of the scattering coefficient on the corresponding isochronous surface. However, it is impossible to distinguish different targets on the same isochronous surface based only on the hydrophone. For this reason, it is necessary to comprehensively utilize the data of each group of sound source-hydrophone to realize CT image reconstruction.

[0107] When implementing the analytical focusing reconstruction algorithm, we first calculate the i ,y i ,z i The active sound source i at ) emits sound waves to the virtual focal point p, which produces echoes reaching the location (x j ,y j ,z j ) is the time Δt of the receiving element j at the position of the receiver, which is expressed as:

[0108]

[0109] Where s is the sound propagation path. When the far-field condition is met, the propagation path is approximately a straight line, and the above formula can be rewritten as:

[0110]

[0111] Wherein, τ is an integral variable, τ=0 represents that the acoustic signal is located at the transmitting point, and τ=1 represents that the acoustic signal is located at the receiving point.

[0112] The original hydrophone data is stored in a two-dimensional matrix S. The elements of the matrix S are ih is an array of length L, representing the L sampling points received by hydrophone j after the active sound source i emits sound waves. After calculating Δt, it can be calculated according to the sampling rate f s Calculate the sampling point sequence number and substitute it into the hydrophone data to obtain the sound pressure contribution P of the group of transmitting-receiving array elements ij at point p ij , the expression is:

[0113] P ij = ij [·f s ]

[0114] Finally, the total sound pressure at point p is obtained by traversing the transmitting and receiving sound source combinations and summing them up, and the expression is:

[0115]

[0116] Where P(x,y,z) is the total sound pressure at point p;

[0117] After normalization, the sound pressure distribution in the area reflects the relative distribution of the scattering coefficient. If there is a target in the target area, the scattering coefficient at the target position will be much larger than that of the surrounding waters, thereby completing the image reconstruction and obtaining the final three-dimensional morphological image of the target.

[0118] Secondly, the principle of the underwater acoustic 3D CT image iterative reconstruction algorithm is as follows:

[0119] Consider a three-dimensional area with the origin O as the center of the target imaging area and the active sound source S i (x i ,y i ,z i ) and hydrophone R j (x j ,y j ,z j ) is a combination of the sound source and the hydrophone array, p(x, y, z) is any point in the target imaging area, then the echo p received by the hydrophone at time t is ij (t) can be expressed as:

[0120]

[0121] Under far-field conditions, since the attenuation of the acoustic wave inside the imaging area is negligible, the above formula can be rewritten as:

[0122]

[0123] In the formula, R 0 is the sum of the distances between the sound source and the hydrophone from the center of the imaging area O, s i and j For point p on line S i O and straight line OR j Projection distance on

[0124] Assume that the incident angle of the sound wave is θ i , the echo exit angle is θ j ,θ i and θ j It is only related to the position of the sound source and the hydrophone. When the distance between the sound source and the hydrophone is much smaller than the distance to the center of the imaging area, it can be considered that θ i = j =,s i = j =s, the expression of the echo signal can be rewritten as:

[0125]

[0126] If the pulse width Δt generated by the sound source is short enough to satisfy cΔt≤Δx, where Δx is the pixel size, the echo signal p(s,θ) under three-dimensional far-field conditions is obtained, which can be expressed as

[0127]

[0128] The formula indicates that the projection data at intervals s in the θ direction are the surface integrals of ellipsoidal surfaces with different focal lengths s, with a certain group of sound sources - hydrophones corresponding to the direction as the focus.

[0129] Since the projection data p(s,θ) is known, it can be calculated based on the data of the sound source-hydrophone group, and the expression is:

[0130]

[0131] The above hydroacoustic imaging model is expressed by a set of equations, which is expressed as follows:

[0132] RX=Y

[0133] In the formula, vector X represents the imaging area to be solved, x j is the value of the jth pixel. For a three-dimensional image of size x×y×z, it can be expanded layer by layer and column by column into a one-dimensional vector for processing. Its length is xyz. In the underwater acoustic imaging model, x j The value reflects the scattering coefficient of the imaging area, Y represents the projection data, which is calculated from the data measured by the hydrophone, and R is the system response matrix, which represents the intersection area of ​​each ellipsoid surface and each cubic pixel in the imaging area;

[0134] In order to solve the above equations, the equations are solved by iterative solution, and the expression is:

[0135]

[0136] in

[0137]

[0138] In the formula, R i represents the i-th row of the response matrix R, λ l Represents the relaxation factor for each iteration.

[0139] It should be noted that before the iteration, an approximate three-dimensional image of the object is obtained by the analytical focusing algorithm, which is used as the initial value of the iteration to determine the position and size of the imaging area, and the scattering coefficient distribution X () As the initial value; in each iteration, by calculating θ j The pixels are corrected by the errors of all ray projections in the direction, and the final target three-dimensional morphological image is obtained after multiple iterations.

[0140] In some embodiments of the present application, the above two algorithms are tested and verified using simulation data. The test model is as follows: Figure 3 shown.

[0141] Figure 3 In the figure, the rectangular block with a length of 4 km, a width of 4 km, and a depth of 3 km is the target water area. The liquid-gas coupling interface is above the water area, reflecting the acoustic characteristics of the water surface. The bottom is the bottom sediment layer. The two lines of arrays arranged on the water surface are sound source-hydrophone arrays, one of which is cross-arranged with 10 hydrophones and 9 active sound sources, and the sound sources are numbered 1-9. The other line is composed of 19 hydrophones, and the distance between two adjacent devices is 100m. During the simulation, the sound sources are ignited in turn in the order of 1-4-7-2-5-8-3-6-9, with an ignition interval of 1s, and the total simulation time is 10s. The detection target is located between the two line arrays. The target is an ellipsoid with a size of 60m×9m×9m, located 800m underwater, and the horizontal distance from the center of the array is 1.8km.

[0142] It should be noted that for the convenience of display and simulation, only one set of arrays of the active sound source array and the hydrophone array in the device is shown in the simulation model. In practical applications, the array arrangement can be freely changed according to actual needs, or it can be randomly scattered over a large range without being restricted to a specific array.

[0143] The simulation results are as follows Figure 4 and Figure 5 As shown in the figure, the simulation results show that the current imaging system and image reconstruction algorithm can achieve imaging of targets at different distances, near and far. The imaging effect is consistent with the real target, proving the feasibility and effectiveness of the active acoustic CT detection and three-dimensional image reconstruction algorithm of underwater targets in this application.

[0144] This application also proposes a method for underwater target acoustic CT three-dimensional imaging and coordinate positioning, including:

[0145] Step 1: setting the sounding order and sounding interval of each active sound source in the active sound source array, and the data collection frequency of the hydrophone in the hydrophone array, and maintaining the time synchronization of each active sound source and each hydrophone;

[0146] Step 2: Control each active sound source to emit sound signals in sequence according to preset settings, and send the three-dimensional spatial coordinate information of each active sound source to the control platform;

[0147] Step 3: in response to each hydrophone receiving acoustic data, the acoustic data and the three-dimensional spatial coordinate information of each hydrophone are sent to the control platform, the acoustic data including direct waves from the active sound source array and scattered wave signals of underwater targets and water environment;

[0148] Step 4: The control platform sends the collected data to the CT image reconstruction unit for data analysis and CT image reconstruction of the underwater target to obtain the final three-dimensional morphological image and spatial coordinates of the target.

[0149] Regarding the method in the above embodiment, the specific steps of each step have been described in detail in the embodiment of the underwater target acoustic CT three-dimensional imaging and coordinate positioning device, and will not be elaborated here.

[0150] Figure 6 A schematic block diagram of an example electronic device 700 that can be used to implement an embodiment of the present application is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present application described and / or required herein.

[0151] like Figure 6 As shown, the device 700 includes a computing unit 701, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 702 or a computer program loaded from a storage unit 708 into a random access memory (RAM) 703. In the RAM 703, various programs and data required for the operation of the device 700 can also be stored. The computing unit 701, the ROM 702, and the RAM 703 are connected to each other via a bus 704. An input / output (I / O) interface 705 is also connected to the bus 704.

[0152] A number of components in the device 700 are connected to the I / O interface 705, including: an input unit 706, such as a keyboard, a mouse, etc.; an output unit 707, such as various types of displays, speakers, etc.; a storage unit 708, such as a disk, an optical disk, etc.; and a communication unit 709, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 709 allows the device 700 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0153] The computing unit 701 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 701 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 701 performs the various methods and processes described above, such as the voice instruction response method. For example, in some embodiments, the voice instruction response method may be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as a storage unit 708. In some embodiments, part or all of the computer program may be loaded and / or installed on the device 700 via ROM 702 and / or communication unit 709. When the computer program is loaded into RAM 703 and executed by the computing unit 701, one or more steps of the voice instruction response method described above may be performed. Alternatively, in other embodiments, the computing unit 701 may be configured to perform the voice instruction response method in any other appropriate manner (e.g., by means of firmware).

[0154] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0155] The program code for implementing the method of the present application can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the program code, when executed by the processor or controller, implements the functions / operations specified in the flow chart and / or block diagram. The program code can be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0156] In the context of the present application, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0157] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0158] The systems and techniques described herein can be implemented in a computing system that includes backend components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes frontend components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such backend components, middleware components, or frontend components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), the Internet, and a blockchain network.

[0159] A computer system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The relationship between the client and the server is generated by computer programs running on the corresponding computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system to solve the defects of difficult management and weak business scalability in traditional physical hosts and VPS services ("Virtual Private Server", or "VPS" for short). The server may also be a server of a distributed system, or a server combined with a blockchain.

[0160] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this application can be executed in parallel, sequentially or in different orders, as long as the expected results of the technical solution of this application can be achieved, and this document is not limited here.

[0161] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A device for acoustic CT three-dimensional imaging and coordinate positioning of underwater targets, characterized in that: include: Active sound source array, used for remote controlled sound generation or timed sound generation; A hydrophone array, used to receive acoustic data, wherein the acoustic data includes direct waves from the active sound source array and scattered wave signals of underwater targets and water environment; A control platform, used to control the active sound source array and the hydrophone array, and collect the sound emission time and three-dimensional spatial coordinate information of the active sound source array and the acoustic data, time information and three-dimensional spatial coordinate information of the hydrophone array; The CT image reconstruction unit is used to perform data analysis and CT image reconstruction of the underwater target according to the data collected by the control platform to obtain the final three-dimensional morphological image and spatial coordinates of the target.

2. The device according to claim 1, characterized in that The active sound source array comprises: Multiple active sound sources for emitting sound signals in a preset configuration sequence; The three-dimensional space coordinate measurement and positioning unit bound to each active sound source is used to obtain the three-dimensional space coordinate information of each active sound source and send it to the control platform.

3. The device according to claim 2, characterized in that The hydrophone array comprises: A plurality of hydrophones, used to receive direct waves from the active sound source array and scattered wave signals from underwater targets and water environment, wherein the hydrophones are arranged in a towed sonar array or a hydrophone array dispersedly arranged in the water; The three-dimensional space coordinate measuring and positioning unit bound to each hydrophone is used to obtain the three-dimensional space coordinate information of each hydrophone and send it to the control platform.

4. The device according to claim 3, characterized in that The control platform comprises: A detection program setting unit, used to set the sounding order and sounding interval of each of the active sound sources, and the data collection frequency of each of the hydrophones; A time synchronization unit, used to set the time synchronization between each of the active sound sources and each of the hydrophones; A remote communication unit is used to realize remote communication between the control platform and the active sound source array and the hydrophone array.

5. The device according to claim 4, characterized in that The CT image reconstruction unit is used for: The image reconstruction problem in underwater acoustic imaging is converted into a problem of solving the distribution of scattering coefficients of each imaging point in the target area, and the final target three-dimensional morphological image is obtained by at least one of an underwater acoustic three-dimensional CT image analytical focusing reconstruction algorithm and an underwater acoustic three-dimensional CT image iterative reconstruction algorithm.

6. The device according to claim 5, characterized in that The processing process of the underwater acoustic three-dimensional CT image analytical focusing reconstruction algorithm is as follows: Assuming that the active sound source sends a narrow pulse signal p0(t) at t = 0, the response of hydrophone j to active sound source i can be expressed as: Among them, D(x,y,z) is the attenuation coefficient, A(x,y,z) is the target scattering coefficient distribution, and Δt is the propagation time; Calculate the position (x i ,y i ,z i The active sound source i at ) emits sound waves to the virtual focal point p, which produces echoes reaching the location (x j ,y j ,z j ) is the time Δt of the receiving element j at the position of the receiver, which is expressed as: Where, s is the sound propagation path; When the far-field condition is met, the propagation path is approximately a straight line, and the above formula can be rewritten as: Wherein, τ is the integral variable, τ = 0 means the acoustic signal is at the transmitting point, and τ = 1 means the acoustic signal is at the receiving point; After calculating Δt, according to the sampling rate f s Calculate the sampling point sequence number and substitute it into the hydrophone data to obtain the sound pressure contribution P of the group of transmitting-receiving array elements ij at point p ij , the expression is: P ij =S ij [Δt·f s ] The original hydrophone data is stored in a two-dimensional matrix S, and the elements of the matrix S are ij is an array of length L, representing the L sampling points received by hydrophone j after the active sound source i emits sound waves; Traverse the transmitting-receiving sound source combination and sum it to get the total sound pressure at point p, which is expressed as: Where P(x,y,z) is the total sound pressure at point p; After normalization, the sound pressure distribution in the area reflects the relative distribution of the scattering coefficient. If there is a target in the target area, the scattering coefficient at the target position will be much larger than that of the surrounding waters, thereby completing the image reconstruction and obtaining the final three-dimensional morphological image of the target.

7. The device according to claim 5, characterized in that The processing process of the underwater acoustic three-dimensional CT image iterative reconstruction algorithm is as follows: Assume a three-dimensional area with the origin O as the center of the target imaging area and the active sound source S i (x i ,y i ,z i ) and hydrophone R j (x j ,y j ,z j ) is a combination of the sound source and the hydrophone array, p(x, y, z) is any point in the target imaging area, then the echo p received by the hydrophone at time t is ij (t) can be expressed as: Under far-field conditions, since the attenuation of the acoustic wave inside the imaging area is negligible, the above formula can be rewritten as: Where R0 is the sum of the distances between the sound source and the hydrophone and the center of the imaging area O, s i and j For point p on line S i O and straight line OR j Projection distance on Assume that the incident angle of the sound wave is θ i , the echo exit angle is θ j ,θ i and θ j It is only related to the position of the sound source and the hydrophone. When the distance between the sound source and the hydrophone is much smaller than the distance to the center of the imaging area, it can be considered that θ i =θ j =θ,s i =s j =s, the expression of the echo signal can be rewritten as: If the pulse width Δt generated by the sound source is short enough to satisfy cΔt<<Δx, where Δx is the pixel size, the echo signal p(s,θ) under three-dimensional far-field conditions is obtained, expressed as p(s,θ)=D(R0)p0∫∫ S A(x,y,z)dS The formula indicates that the projection data at intervals s in the θ direction is the surface integral of the ellipsoidal surface with different focal lengths s, with a certain set of sound sources-hydrophones corresponding to the direction as the focus; Since the projection data p(s,θ) is known, it can be calculated based on the data of the sound source-hydrophone group, and the expression is: The above hydroacoustic imaging model is expressed by a set of equations, which is expressed as follows: RX=Y In the formula, vector X represents the imaging area to be solved, x j is the value of the jth pixel. For a three-dimensional image of size x×y×z, it can be expanded layer by layer and column by column into a one-dimensional vector for processing. Its length is xyz. In the underwater acoustic imaging model, x j The value reflects the scattering coefficient of the imaging area, Y represents the projection data, which is calculated from the data measured by the hydrophone, and R is the system response matrix, which represents the intersection area of ​​each ellipsoid surface and each cubic pixel in the imaging area; The equation is solved by iterative solution, and the expression is: in In the formula, R i represents the i-th row of the response matrix R, λ l represents the relaxation factor of each iteration; before the iteration, the approximate three-dimensional image of the object is obtained by the analytical focusing algorithm, which is used as the initial value of the iteration to determine the position and size of the imaging area, and the scattering coefficient distribution X (0) As the initial value; in each iteration, by calculating θ j The pixels are corrected by the errors of all ray projections in the direction, and the final target three-dimensional morphological image is obtained after multiple iterations.

8. A method for underwater target acoustic CT three-dimensional imaging and coordinate positioning using the device of any one of claims 1 to 7, characterized in that: The following steps are involved: Setting the sounding order and sounding interval of each active sound source in the active sound source array, and the data collection frequency of the hydrophone in the hydrophone array, and maintaining the time synchronization of each active sound source and each hydrophone; Controlling each of the active sound sources to emit sound signals in sequence according to preset settings, and sending the three-dimensional spatial coordinate information of each active sound source to the control platform; In response to each hydrophone receiving acoustic data, the acoustic data and three-dimensional spatial coordinate information of each hydrophone are sent to a control platform, wherein the acoustic data includes direct waves from the active sound source array and scattered wave signals of underwater targets and water environment; The control platform is controlled to send the collected data to the CT image reconstruction unit to perform data analysis and CT image reconstruction of the underwater target, so as to obtain the final three-dimensional morphological image and spatial coordinates of the target.

9. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to claim 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to claim 8 when executed by a processor.

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