Underwater target ultra-short baseline positioning method and system considering sound ray bending

Abstract

The invention relates to the technical field of underwater target positioning, in particular to an underwater target ultra-short baseline positioning method and system considering sound ray bending, and the method comprises the steps: firstly obtaining the time difference of arrival of sound signals received by two hydrophones at any adjacent position; all independent time difference of arrival observation values form an observation vector; calculating the optimal estimated value of the direction of arrival according to the principle of least squares; calculating a beam initial incident angle according to the direction of arrival and a rotation matrix obtained by an attitude sensor on the ultra-short baseline system; calculating the horizontal displacement and depth of the underwater target by adopting a constant gradient sound ray tracking method based on the wave beam initial incidence angle, the sound signal propagation time delay obtained by the ultra-short baseline system and the immersion depth of the ultra-short baseline system; and finally, calculating a coordinate vector of the underwater target in a local horizontal coordinate system by using the direction of arrival and the horizontal displacement and depth of the underwater target. According to the method, the influence of sound ray bending on ultra-short baseline distance measurement and direction finding is considered, and the positioning precision of the underwater target is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater target positioning, and in particular to an underwater target ultra-short baseline positioning method and system taking into account sound line bending. Background Art

[0002] Ultra-short baseline positioning accuracy is an important factor affecting the mission execution capability of underwater equipment. Regarding the issue of how to improve the ultra-short baseline positioning accuracy, existing research mainly focuses on improving the quality of USBL original observations from the perspective of signal processing, such as using generalized cross-correlation, adaptive minimum mean square error, recursive least squares, Fourier transform and other time delay, time delay difference or phase difference estimation methods. Improving the quality of original observations will inevitably help improve the USBL positioning accuracy, but the sound line bending caused by the spatiotemporal changes in underwater sound speed causes the azimuth information measured by USBL to be the direction of arrival (DOA) rather than the line of sight (LOS) of the underwater target, which is one of the important reasons for USBL positioning errors. There are two main existing ultra-short baseline positioning methods. The conventional ultra-short baseline positioning method directly uses azimuth and distance to calculate the position of underwater targets, regards sound waves as propagating in a straight line, and does not consider the impact of sound line bending on ultra-short baseline positioning; the deep-sea ultra-short baseline iterative positioning method based on constant sound velocity sound line tracking uses the depth information of underwater targets to accurately calculate the horizontal distance of the target under the condition that the initial incident angle of the beam is unknown. This method does not use the azimuth information of ultra-short baseline observations and requires the assistance of depth sensors, which increases the complexity of the ultra-short baseline positioning system and the signal interaction load. Summary of the invention

[0003] The present invention aims to solve the problem that sound waves are currently regarded as propagating in a straight line without considering the influence of sound line bending on ultra-short baseline positioning. A method and system for ultra-short baseline positioning of underwater targets taking into account sound line bending is proposed. The method takes into account the influence of sound line bending on ultra-short baseline ranging and direction finding, thereby improving the positioning accuracy of underwater targets.

[0004] To achieve the above purpose, the technical solution adopted is:

[0005] An underwater target ultra-short baseline positioning method taking into account sound line bending comprises the following steps:

[0006] Firstly, the far-field model is used to approximate the acoustic wave sent by the underwater target as a plane wave, and the arrival time difference of the acoustic signal received by two hydrophones at any adjacent position is obtained.

[0007] Then all independent arrival time difference observations are combined into an observation vector;

[0008] Then, based on the least squares principle, the optimal estimate of the direction of arrival is calculated;

[0009] Then, the initial incident angle of the beam is calculated based on the direction of arrival and the rotation matrix obtained by the attitude sensor on the ultra-short baseline system;

[0010] Based on the initial incident angle of the beam, the propagation delay of the acoustic signal obtained by the ultra-short baseline system and the draft of the ultra-short baseline system, the horizontal displacement and depth of the underwater target are calculated using the constant gradient acoustic ray tracking method.

[0011] Finally, the coordinate vector of the underwater target in the local horizontal coordinate system is calculated using the wave arrival direction and the horizontal displacement and depth of the underwater target.

[0012] According to the underwater target ultra-short baseline positioning method taking into account the bending of the sound line of the present invention, further, the sound wave sent by the underwater target is approximated as a plane wave using a far-field model, and the arrival time difference of the sound signal received by two hydrophones at any adjacent position is obtained, and the calculation formula is as follows:

[0013]

[0014] In the formula, δ i,j is the arrival time difference of the acoustic signal received by hydrophones i and j, p represents the position vector of the hydrophone in the USBL carrier coordinate system, and the subscript represents the hydrophone number; the unit vector d represents the direction of arrival of the acoustic signal when it arrives at the ultra-short baseline receiving array, and c represents the sound speed at the ultra-short baseline transceiver.

[0015] According to the underwater target ultra-short baseline positioning method taking into account the bending of the sound line of the present invention, further, all independent arrival time difference observation values ​​are combined into an observation vector as follows:

[0016] Δ=[δ 1,2 δ 2,3 …δ N-1,N ] T .

[0017] According to the underwater target ultra-short baseline positioning method taking into account the sound line bending of the present invention, further, according to the least squares principle, the optimal estimate of the wave arrival direction is calculated. for:

[0018]

[0019] Where A is the coefficient matrix, which is expressed as follows:

[0020]

[0021] According to the underwater target ultra-short baseline positioning method taking into account the bending of the sound line of the present invention, further, the initial incident angle of the beam is calculated according to the wave direction and the rotation matrix obtained by the attitude sensor on the ultra-short baseline system, and the calculation formula is as follows:

[0022]

[0023] Where n z =

[001] T is the unit normal vector of the horizontal plane in the local horizontal coordinate system, Represents the rotation matrix from the ultra-short baseline carrier coordinate system to the local horizontal coordinate system, obtained by the attitude sensor of the ultra-short baseline system.

[0024] According to the underwater target ultra-short baseline positioning method taking into account the bending of the sound line of the present invention, further, the coordinate vector of the underwater target in the local horizontal coordinate system is calculated using the wave direction and the horizontal displacement and depth of the underwater target. The calculation formula is as follows:

[0025]

[0026] In the formula, is the coordinate vector of the underwater target in the local horizontal coordinate system, and s represents the coordinate vector of the underwater target in the local horizontal coordinate system. The two-dimensional column vector composed of the first two elements of Δp e and z e is the horizontal displacement and depth calculated by the ray tracing method.

[0027] Furthermore, the present invention also provides an underwater target ultra-short baseline positioning system taking into account the bending of sound lines, comprising:

[0028] The arrival time difference calculation module is used to approximate the sound waves sent by the underwater target as plane waves using a far-field model, and obtain the arrival time difference of the sound signals received by two hydrophones at any adjacent positions;

[0029] An observation vector composition module is used to compose an observation vector from all independent arrival time difference observations;

[0030] The optimal estimation calculation module of the wave direction of arrival is used to calculate the optimal estimation of the wave direction of arrival based on the least squares principle;

[0031] The beam initial incident angle calculation module is used to calculate the beam initial incident angle according to the wave direction and the rotation matrix obtained by the attitude sensor on the ultra-short baseline system;

[0032] The horizontal displacement depth acquisition module is used to calculate the horizontal displacement and depth of the underwater target using the constant gradient sound line tracking method based on the initial incident angle of the beam, the propagation delay of the acoustic signal acquired by the ultra-short baseline system, and the draft depth of the ultra-short baseline system;

[0033] The underwater target position calculation module is used to calculate the coordinate vector of the underwater target in the local horizontal coordinate system using the wave arrival direction and the horizontal displacement and depth of the underwater target.

[0034] The beneficial effects achieved by adopting the above technical solution are:

[0035] Compared with the conventional underwater target ultra-short baseline positioning method, the present invention takes into account the influence of sound line bending on ultra-short baseline ranging and direction finding, and the positioning is more accurate. Compared with the deep-sea ultra-short baseline iterative positioning method based on constant sound speed sound line tracking, this method does not require additional depth sensors, ensuring the portability and flexibility of the system. The present invention utilizes the inherent transmitting transducer, receiving array and IMU of the ultra-short baseline system to achieve high-precision positioning without the influence of sound line bending, and improves the accuracy of ultra-short baseline positioning without increasing the complexity of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention, wherein the drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0037] Figure 1 It is a schematic flow chart of an underwater target ultra-short baseline positioning method taking into account sound line bending according to an embodiment of the present invention;

[0038] Figure 2 Schematic diagram of the initial incident angle of the beam according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings of specific embodiments of the present invention to clearly and completely describe the exemplary scheme of the embodiment of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the relevant field.

[0040] The distance observation value of the ultra-short baseline is affected by the bending of the sound line, and actually represents the non-spatial distance; the azimuth observation value of the ultra-short baseline (USBL) is affected by the bending of the sound line, and actually represents the wave arrival direction rather than the line of sight direction, which is an important factor restricting its positioning accuracy. In response to the problem of inconsistency between the wave arrival direction and the line of sight direction, existing methods generally regard the target depth as error-free or with extremely high accuracy, but this premise assumption does not conform to the actual situation that the measurement error of the pressure depth gauge increases linearly with the increase of depth, resulting in the actual effect of the existing method is not ideal. Moreover, the depth information requires the underwater target to carry a depth sensor and transmit the depth value to the ultra-short baseline transceiver, which increases the complexity of the system.

[0041] In order to theoretically eliminate the problem that ultra-short baseline positioning is affected by sound line bending, the ultra-short baseline positioning method for underwater targets that takes into account sound line bending uses attitude information to convert the azimuth observation value in the ultra-short baseline carrier coordinate system (abbreviated as b system) to the local horizontal coordinate system (abbreviated as l system) to calculate the initial incident angle of the beam, and then combines the round trip delay (RTD) observation value and calculates the underwater target position based on the constant gradient sound line tracking method. Figure 1 As shown, the method specifically comprises the following steps:

[0042] Step S101: Use the far-field model to approximate the sound waves sent by the underwater target as plane waves, and obtain the calculation formula for the arrival time difference of the sound signals received by two hydrophones at any adjacent positions as follows:

[0043]

[0044] In the formula, δ i,j is the arrival time difference (TDOA) of the acoustic signal received by hydrophones i and j, also known as the time delay difference (TDD); p represents the position vector of the hydrophone in the USBL carrier coordinate system, and the subscript represents the hydrophone number; the unit vector d represents the direction of arrival (direction vector) of the acoustic signal when it arrives at the ultra-short baseline receiving array, and c represents the sound speed at the ultra-short baseline transceiver.

[0045] Step S102: All independent TDOA / TDD observation values ​​are combined into an observation vector:

[0046] Δ=[δ 1,2 δ 2,3 … δ N-1,N ] T .

[0047] Step S103: Calculate the optimal estimate of the direction of arrival (direction vector) based on the least squares principle for:

[0048]

[0049] Where A is a coefficient matrix composed of position vectors, and its expression is as follows:

[0050]

[0051] Step S104: Figure 2 As shown, the initial incident angle of the beam is calculated based on the direction of arrival and the rotation matrix obtained by the attitude sensor on the ultra-short baseline system. The calculation formula is as follows:

[0052]

[0053] Where n z =[0 0 1] T is the unit normal vector of the horizontal plane in the local horizontal coordinate system, Represents the rotation matrix from the ultra-short baseline carrier coordinate system to the local horizontal coordinate system, obtained by the attitude sensor of the ultra-short baseline system.

[0054] Step S105: Calculate the horizontal displacement and depth of the underwater target using a constant gradient ray tracking method based on the initial incident angle of the beam, the acoustic signal propagation delay acquired by the ultra-short baseline system, and the draft of the ultra-short baseline system.

[0055] Step S106, using the wave arrival direction (direction vector) and the horizontal displacement and depth of the underwater target to calculate the coordinate vector of the underwater target in the local horizontal coordinate system, the calculation formula is as follows:

[0056]

[0057] In the formula, is the coordinate vector of the underwater target in the local horizontal coordinate system, and s represents the coordinate vector of the underwater target in the local horizontal coordinate system. The two-dimensional column vector composed of the first two elements of Δp e and z e is the horizontal displacement and depth calculated by the ray tracing method.

[0058] Corresponding to the above method, this embodiment also proposes an underwater target ultra-short baseline positioning system taking into account the bending of sound lines, including:

[0059] The arrival time difference calculation module is used to approximate the sound waves sent by the underwater target as plane waves using the far-field model, and obtain the arrival time difference of the sound signals received by two hydrophones at any adjacent positions.

[0060] The observation vector composition module is used to compose an observation vector from all independent arrival time difference observation values.

[0061] The optimal estimation module of the wave direction of arrival is used to calculate the optimal estimation of the wave direction of arrival based on the least squares principle.

[0062] The beam initial incident angle calculation module is used to calculate the beam initial incident angle according to the wave direction and the rotation matrix obtained by the attitude sensor on the ultra-short baseline system.

[0063] The horizontal displacement depth acquisition module is used to calculate the horizontal displacement and depth of the underwater target using the constant gradient sound line tracking method based on the initial incident angle of the beam, the acoustic signal propagation delay obtained by the ultra-short baseline system and the draft depth of the ultra-short baseline system.

[0064] The underwater target position calculation module is used to calculate the coordinate vector of the underwater target in the local horizontal coordinate system using the wave arrival direction and the horizontal displacement and depth of the underwater target.

[0065] The present invention takes into account the influence of sound line bending on ultra-short baseline ranging and direction finding, so as to make underwater target positioning more accurate.

[0066] Unless otherwise specifically stated, the relative steps, numerical expressions and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0067] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0068] The units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. A person of ordinary skill in the art may use different methods to implement the described functions for each specific application, but such implementation is not considered to be beyond the scope of the present invention.

[0069] Those skilled in the art will appreciate that all or part of the steps in the above method can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk or an optical disk. Optionally, all or part of the steps in the above embodiment can also be implemented using one or more integrated circuits, and accordingly, each module / unit in the above embodiment can be implemented in the form of hardware or in the form of software function modules. The present invention is not limited to any specific form of combination of hardware and software.

[0070] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An underwater target ultra-short baseline positioning method taking into account the bending of sound lines, characterized in that: The following steps are involved: Firstly, the far-field model is used to approximate the acoustic wave sent by the underwater target as a plane wave, and the arrival time difference of the acoustic signal received by two hydrophones at any adjacent position is obtained. Then all independent arrival time difference observations are combined into an observation vector; Then, based on the least squares principle, the optimal estimate of the direction of arrival is calculated; Then, the initial incident angle of the beam is calculated based on the direction of arrival and the rotation matrix obtained by the attitude sensor on the ultra-short baseline system; Based on the initial incident angle of the beam, the propagation delay of the acoustic signal obtained by the ultra-short baseline system and the draft of the ultra-short baseline system, the horizontal displacement and depth of the underwater target are calculated using the constant gradient acoustic ray tracking method. Finally, the coordinate vector of the underwater target in the local horizontal coordinate system is calculated using the wave arrival direction and the horizontal displacement and depth of the underwater target.

2. The underwater target ultra-short baseline positioning method taking into account the sound line bending according to claim 1 is characterized in that: The far-field model is used to approximate the sound waves sent by underwater targets as plane waves, and the arrival time difference of the sound signals received by two hydrophones at any adjacent positions is obtained. The calculation formula is as follows: In the formula, δ i,j is the arrival time difference of the acoustic signal received by hydrophones i and j, p represents the position vector of the hydrophone in the USBL carrier coordinate system, and the subscript represents the hydrophone number; the unit vector d represents the direction of arrival of the acoustic signal when it arrives at the ultra-short baseline receiving array, and c represents the sound speed at the ultra-short baseline transceiver.

3. The underwater target ultra-short baseline positioning method taking into account the sound line bending according to claim 2 is characterized in that: All independent arrival time difference observations are combined into an observation vector: Δ=[δ 1,2 d 2,3 …d N-1,N ] T 。 4. The underwater target ultra-short baseline positioning method taking into account the sound line bending according to claim 3 is characterized in that: According to the least squares principle, the optimal estimate of the direction of arrival is calculated for: Where A is the coefficient matrix, which is expressed as follows:

5. The underwater target ultra-short baseline positioning method taking into account the sound line bending according to claim 4 is characterized in that: The initial incident angle of the beam is calculated based on the direction of arrival and the rotation matrix obtained by the attitude sensor on the ultra-short baseline system. The calculation formula is as follows: Where n z =[0 0 1] T is the unit normal vector of the horizontal plane in the local horizontal coordinate system, Represents the rotation matrix from the ultra-short baseline carrier coordinate system to the local horizontal coordinate system, obtained by the attitude sensor of the ultra-short baseline system.

6. The underwater target ultra-short baseline positioning method taking into account the sound line bending according to claim 5 is characterized in that: The coordinate vector of the underwater target in the local horizontal coordinate system is calculated using the wave arrival direction and the horizontal displacement and depth of the underwater target. The calculation formula is as follows: In the formula, is the coordinate vector of the underwater target in the local horizontal coordinate system, and s represents The first two elements of the two-dimensional column vector, Δp e and z e is the horizontal displacement and depth calculated by the ray tracing method.

7. An underwater target ultra-short baseline positioning system taking into account the bending of sound lines, characterized in that: include: The arrival time difference calculation module is used to approximate the sound waves sent by the underwater target as plane waves using a far-field model, and obtain the arrival time difference of the sound signals received by two hydrophones at any adjacent positions; An observation vector composition module is used to compose an observation vector from all independent arrival time difference observations; The optimal estimation calculation module of the wave direction of arrival is used to calculate the optimal estimation of the wave direction of arrival based on the least squares principle; The beam initial incident angle calculation module is used to calculate the beam initial incident angle according to the wave direction and the rotation matrix obtained by the attitude sensor on the ultra-short baseline system; The horizontal displacement depth acquisition module is used to calculate the horizontal displacement and depth of the underwater target using the constant gradient sound line tracking method based on the initial incident angle of the beam, the propagation delay of the acoustic signal acquired by the ultra-short baseline system, and the draft depth of the ultra-short baseline system; The underwater target position calculation module is used to calculate the coordinate vector of the underwater target in the local horizontal coordinate system using the wave arrival direction and the horizontal displacement and depth of the underwater target.

8. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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