An underwater acoustic short baseline positioning system and method

Abstract

This invention discloses an underwater acoustic short baseline positioning system and method, belonging to the field of underwater acoustic positioning and spatial geometry calculation technology. It is used for underwater acoustic short baseline positioning. The system includes a catamaran-based platform, an attitude measurement unit, a diagonal extreme topology acoustic array, and a calculation module. The diagonal extreme topology acoustic array consists of five underwater acoustic transducers, including four edge receiving transducers and one central main transducer. The method includes acquiring the real-time coordinates of the edge receiving transducers, correcting the real-time coordinates of the edge receiving transducers using three-dimensional attitude data, measuring the straight-line distance between each edge receiving transducer and the target, constructing and calculating a spherical distance equation with the target's true coordinates as unknowns, introducing a ranging acoustic vector to construct a system of linear equations, and solving to obtain the estimated three-dimensional coordinates of the target. This invention significantly reduces the geometric accuracy attenuation factor of the Z-axis and improves the depth calculation accuracy through the diagonal cross extreme distribution structure.

Description

Technical Field

[0001] This invention discloses an underwater acoustic short baseline positioning system and method, belonging to the field of underwater acoustic positioning and spatial geometry calculation technology. Background Technology

[0002] In existing short baseline (SBL) underwater target acoustic localization systems, the noise immunity (geometric attenuation factor, GDOP) of 3D coordinate intersection depends entirely on the topological coordinate system of the four transducers in 3D space. Currently, mainstream catamaran SBL systems typically mount the four transducers on the same horizontal plane at the bottom of the vessel. In purely acoustic 3D spherical intersection solutions, this coplanar arrangement leads to a missing rank in the Jacobian observation matrix along the Z-axis (depth) direction, causing numerical singularities in the depth calculation. To address this issue, existing solutions typically employ two approaches: one is to rely on the underwater target's built-in pressure depth gauge for data transmission, reducing the 3D solution to a 2D plane, but this increases system hardware costs and dependence on underwater acoustic communication; the other is to introduce constrained adjustment models or state-constrained filtering algorithms at the software algorithm layer. These algorithms have high computational complexity and are still prone to solution divergence under environmental noise interference.

[0003] To overcome the coplanar singularity, some existing algorithm improvements attempt to introduce height differences. Due to the rigid constraint of the maximum depth of physical equipment, technicians typically employ methods such as one deep and three shallow (e.g., only the left front is extremely deep), front deep and back shallow / same-side deep and shallow (e.g., two deep on the left, two shallow on the right), and completely random staggered placement. While the one deep and three shallow method breaks the singularity, the resulting tetrahedron has a small volume and mediocre noise resistance. Although the front deep and back shallow / same-side deep and shallow placement methods have different heights, the four points fall exactly on an inclined two-dimensional plane, causing the algorithm to fall into the "inclined coplanar singularity trap" again, the matrix determinant returns to zero, and the algorithm completely fails. Completely random staggered placement, due to the lack of mathematical extremum optimization for the error propagation model, exhibits extremely random values ​​for the determinant of its observation matrix, and is far from reaching the theoretical upper limit. During the least squares inversion process, the error amplification factor (VDOP) on the Z-axis remains high. Summary of the Invention

[0004] The purpose of this invention is to provide an underwater acoustic short baseline positioning system and method to solve the problems of Z-axis singularity and error divergence in the basic positioning algorithm and the suboptimal Z-axis positioning accuracy under limited physical boundaries in the prior art.

[0005] An underwater acoustic short baseline positioning system and method includes: a catamaran shipborne platform, an attitude measurement unit, a global navigation satellite system, a diagonal extreme topological acoustic array, and a solution module; The diagonal extreme topology acoustic array consists of 5 underwater acoustic transducers, including 4 edge receiving transducers and 1 central main transducer. The central main transducer is installed at the bottom of the geometric centerline of the catamaran platform, and the 4 edge receiving transducers are installed at the four corners of the bottom of the catamaran platform. The 4 edge receiving transducers form a diagonal extreme topology structure with high and low intersections. The solution module incorporates the standard least squares method, receives ranging data from the diagonal extreme topological acoustic array, and outputs the estimated three-dimensional coordinates of the target.

[0006] S1. Obtain the real-time coordinates of the four edge receiving transducers under the current attitude of the catamaran platform. The transducer depths of the left front and right rear edge receiving transducers are: The transducer depth of the receiving transducers at the right front and left rear edges is... ; S2. Using the three-dimensional attitude data of the catamaran-based platform measured in real time by the attitude measurement unit, the displacement of the support rod caused by the lever arm effect is compensated based on the three-dimensional attitude data, and the real-time coordinates of each edge receiving transducer are corrected. S3. Acoustic signals are emitted through the central main transducer, and response signals from the target are received by four edge receiving transducers. The straight-line distance between each edge receiving transducer and the target is measured. S4. Using the real-time coordinates of the corrected edge receiving transducers as known quantities and the straight-line distance between each edge receiving transducer and the target as observed values, construct a spherical distance equation with the target's true coordinates as unknowns. Perform differential linearization on the spherical distance equation to obtain the core observation matrix. S5. Introduce the ranging acoustic vector, construct a system of linear equations based on the core observation matrix and the ranging acoustic vector, and solve the system of linear equations using the least squares method to obtain the estimated three-dimensional coordinates of the target.

[0007] The extreme topology structure with diagonal high and low intersections includes transducers at the left front and right rear edges, which are mounted on the bottom of the catamaran platform via support rods, with a draft of the maximum physical lower limit. ; The front right and rear left edge receiving transducers adopt a bottom-mounted design, with a draft of the minimum physical depth boundary. .

[0008] The catamaran platform has a rectangular horizontal acoustic baseline with a length of [missing information]. Width is ; The attitude measurement unit and global navigation satellite system are mounted on the top of the catamaran platform; The calculation module is installed inside the cabin of the catamaran platform; The solution module incorporates the standard least squares method, receives ranging data from four edge receiving transducers, and outputs an estimated three-dimensional coordinate value of the target.

[0009] S1 includes S1.1, setting the spatial coordinate system, and the coordinates of the four edge receiving transducers are as follows: , , , ; The coordinates of the left front edge receiving transducer. The coordinates of the right front edge receiving transducer. The coordinates of the right rear edge receiving transducer. The coordinates of the left rear edge receiving transducer; The depth coordinates of the receiving transducer at the left front edge. The depth of the receiving transducer at the right front edge. The depth coordinates of the right rear edge receiving transducer. The coordinates are the depth coordinates of the receiver transducer at the left rear edge.

[0010] S1 includes S1.2, and satisfy: ; and satisfy: .

[0011] Using the attitude measurement unit, S2 includes real-time acquisition of the roll angle of the catamaran platform. Pitch angle and heading angle ; Based on the geometric length and installation position of the support rod, the lever arm effect displacement of the catamaran-based platform is compensated, and the real-time coordinates of each edge receiving transducer are corrected.

[0012] S3 includes the following: the straight-line distance between each edge receiving transducer and the target is: ; In the formula, For the index of the edge receiving transducer, For the first The distance between an edge receiving transducer and the target. , and For the first Corrected three-dimensional coordinates of an edge receiving transducer.

[0013] S4 includes, assuming the target's true coordinates are... , combined By linearizing the spherical distance equations using difference, we obtain the core observation matrix. : .

[0014] S5 includes the introduction of ranging acoustic vectors. Construct a system of linear equations: ; The linearized system of equations is solved using the least squares method, and the equations are iterated until convergence, outputting the estimated three-dimensional coordinates of the target.

[0015] Compared with existing technologies, the present invention has the following advantages: The present invention proposes a diagonal cross-polarity distribution structure (i.e., the depth of the first diagonal transducer is...). (The depth of the second diagonal transducer is 0). Based on the derivation of the error covariance matrix, the theoretical positioning error of the Z-axis depth is inversely proportional to the characteristic term of the space observation matrix. The diagonal topology of this invention ensures that the characteristic term consistently reaches a global maximum of 2 under constraints. Compared to conventional one-deep-three-shallow or randomly staggered schemes, this invention effectively amplifies the determinant of the observation matrix, significantly reducing the geometrical precision attenuation factor (VDOP) of the Z-axis under the same ranging noise conditions, thus improving depth calculation accuracy. Because the physical array topology of this invention directly generates a full-rank and conditionally optimized Jacobian observation matrix from the bottom layer, the calculation computer does not need to call computationally intensive additional constraint adjustment modules or nonlinear Kalman filters. The system only needs to run the standard unconstrained least squares algorithm to output stable 3D coordinates, reducing processor computational overhead and eliminating the risk of divergence caused by improper constraint algorithm parameter settings, thereby improving the overall stability of the positioning system. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the underwater acoustic short baseline positioning system of the present invention; Figure 2 This is a front view of the underwater acoustic short baseline positioning system of the present invention; Figure 3 This is a side view of the underwater acoustic short baseline positioning system of the present invention; Figure 4 This is a top view of the underwater acoustic short baseline positioning system of the present invention; Figure 5 It is a scatter plot of global optimization of Z-axis precision decay factor (VDOP) based on full permutation grid traversal; Figure 6 This is a comparison diagram of the Z-axis depth probability density distribution (PDF) calculated by the layout of this invention and the prior art; Figure 7This is a comparison diagram of the dynamic spatial trajectory positioning and tracking effects of the layout of this invention and the randomly staggered layout when an underwater target is performing three-dimensional spiral motion. Figure 8 This is a comparison chart of the real-time calculation error timing fluctuations in the Z-axis (depth) direction between the layout of this invention and the randomly staggered layout when an underwater target is undergoing three-dimensional spiral motion. In the diagram, 1-Left platform of the catamaran shipborne platform; 2-Right platform of the catamaran shipborne platform; 3-Attitude measurement unit; 4-Central main transducer; 5-Left front edge receiving transducer; 6-Right front edge receiving transducer; 7-Right rear edge receiving transducer; 8-Left rear edge receiving transducer; 9-Left thruster; 10-Right thruster; 11-Support rod; 12-Crossbeam mounting base; 13-Equipment mounting plate; 14-GNSS antenna; 15-Crossbeam; 16-Mast rotating hinge; 17-Type A mast bracket; 18-Radio communication antenna; 19-Tricolor navigation light; 20-Panoramic camera; 21-Mast reinforcing rib. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0018] An underwater acoustic short baseline positioning system and method includes: a catamaran shipborne platform, an attitude measurement unit, a global navigation satellite system, a diagonal extreme topological acoustic array, and a solution module; The diagonal extreme topology acoustic array consists of 5 underwater acoustic transducers, including 4 edge receiving transducers and 1 central main transducer. The central main transducer is installed at the bottom of the geometric centerline of the catamaran platform, and the 4 edge receiving transducers are installed at the four corners of the bottom of the catamaran platform. The 4 edge receiving transducers form a diagonal extreme topology structure with high and low intersections. The solution module incorporates the standard least squares method, receives ranging data from the diagonal extreme topological acoustic array, and outputs the estimated three-dimensional coordinates of the target.

[0019] S1. Obtain the real-time coordinates of the four edge receiving transducers under the current attitude of the catamaran platform. The transducer depths of the left front and right rear edge receiving transducers are: The transducer depth of the receiving transducers at the right front and left rear edges is... ; S2. Using the three-dimensional attitude data of the catamaran-based platform measured in real time by the attitude measurement unit, the displacement of the support rod caused by the lever arm effect is compensated based on the three-dimensional attitude data, and the real-time coordinates of each edge receiving transducer are corrected. S3. Acoustic signals are emitted through the central main transducer, and response signals from the target are received by four edge receiving transducers. The straight-line distance between each edge receiving transducer and the target is measured. S4. Using the real-time coordinates of the corrected edge receiving transducers as known quantities and the straight-line distance between each edge receiving transducer and the target as observed values, construct a spherical distance equation with the target's true coordinates as unknowns. Perform differential linearization on the spherical distance equation to obtain the core observation matrix. S5. Introduce the ranging acoustic vector, construct a system of linear equations based on the core observation matrix and the ranging acoustic vector, and solve the system of linear equations using the least squares method to obtain the estimated three-dimensional coordinates of the target.

[0020] The extreme topology structure with diagonal high and low intersections includes transducers at the left front and right rear edges, which are mounted on the bottom of the catamaran platform via support rods, with a draft of the maximum physical lower limit. ; The front right and rear left edge receiving transducers adopt a bottom-mounted design, with a draft of the minimum physical depth boundary. .

[0021] The catamaran platform has a rectangular horizontal acoustic baseline with a length of [missing information]. Width is ; The attitude measurement unit and global navigation satellite system are mounted on the top of the catamaran platform; The calculation module is installed inside the cabin of the catamaran platform; The solution module incorporates the standard least squares method, receives ranging data from four edge receiving transducers, and outputs an estimated three-dimensional coordinate value of the target.

[0022] S1 includes S1.1, setting the spatial coordinate system, and the coordinates of the four edge receiving transducers are as follows: , , , ; The coordinates of the left front edge receiving transducer. The coordinates of the right front edge receiving transducer. The coordinates of the right rear edge receiving transducer. The coordinates of the left rear edge receiving transducer; The depth coordinates of the receiving transducer at the left front edge. The depth of the receiving transducer at the right front edge. The depth coordinates of the right rear edge receiving transducer. The coordinates are the depth coordinates of the receiver transducer at the left rear edge.

[0023] S1 includes S1.2, and satisfy: ; and satisfy: .

[0024] Using the attitude measurement unit, S2 includes real-time acquisition of the roll angle of the catamaran platform. Pitch angle and heading angle ; Based on the geometric length and installation position of the support rod, the lever arm effect displacement of the catamaran-based platform is compensated, and the real-time coordinates of each edge receiving transducer are corrected.

[0025] S3 includes the following: the straight-line distance between each edge receiving transducer and the target is: ; In the formula, For the index of the edge receiving transducer, For the first The distance between an edge receiving transducer and the target. , and For the first Corrected three-dimensional coordinates of an edge receiving transducer.

[0026] S4 includes, assuming the target's true coordinates are... , combined By linearizing the spherical distance equations using difference, we obtain the core observation matrix. : .

[0027] S5 includes the introduction of ranging acoustic vectors. Construct a system of linear equations: ; The linearized system of equations is solved using the least squares method, and the equations are iterated until convergence, outputting the estimated three-dimensional coordinates of the target.

[0028] The specific process of compensating for lever arm effect displacement in this invention includes, using the attitude measurement unit (IMU) of the catamaran platform as the coordinate origin, obtaining the first... The mounting arm vector of an edge receiver transducer in the ship's inherent hull coordinate system. ; Roll angle acquired in real time using IMU Pitch angle and heading angle Construct a three-dimensional rotation matrix from the ship's hull coordinate system to the geographic reference coordinate system. ; Calculate the displacement deviation vector caused by the lever effect of the hull rolling with the waves. : ; By superimposing this deviation vector onto the initial absolute coordinates of the platform in a horizontal, static state, the corrected real-time three-dimensional coordinates can be obtained. This step effectively eliminates the disruption of extreme topological elevation differences caused by changes in hull attitude.

[0029] The specific process of solving and iteratively converging using the least squares method in this invention includes setting an initial iterative estimate of the true coordinates of the target. ; Using the current iteration value Calculate the theoretical distance from each transducer to the target and subtract it from the actual acoustic measurement distance to obtain the error acoustic vector. In the present Constructing the core observation Jacobian matrix by taking partial derivatives ; Calculate the coordinate correction using the least squares formula: ; Update target coordinates: ; Determine the norm of the correction quantity If the value is less than the preset convergence threshold (0.01m), stop the iteration and output the result. The three-dimensional coordinates of the target are used as the reference; otherwise, continue to the next iteration.

[0030] The core design concept of this invention lies in replacing complex adjustment at the software level with the extreme topology of physical space. This invention effectively improves Z-axis accuracy at the algorithm level, based on the most rigorous least-squares error propagation theory and the boundary extreme value theorem of multivariable linear programming. The proof is as follows. Introduction Assume the position calculation error : ; Using the adjoint matrix expansion ,extract Error propagation term of the shaft : ; ; In the formula, This is the amplification factor of the system's Z-axis error on the ranging noise. , , They are respectively The algebraic cofactors of the elements in the first, second, and third columns corresponding to the elements in the third row. , , They are respectively The distance measurement error component in the data; It is the absolute value; Build Determinant: ; and satisfy: ; In the formula, Proportional to the sign; This formula reveals the method for determining the accuracy of the underlying algorithm, namely, to minimize the Z-axis calculation error of the standard least squares method. Minimization must be achieved through hardware mechanical design, ensuring that the spatial topological denominator characteristic function... To achieve absolute maximization.

[0031] The global optimality of the method in this invention is proven through exhaustive comparison. Let... The known rigid physical constraint boundary of the system is Substitute all possible layouts of existing technologies into Perform an exhaustive test. Case 1 represents the traditional coplanar singularity, where all four transducers have the same depth. hour: ; When the denominator is 0 Infinity, singular matrix, algorithm crashes; Case 2 is characterized by deeper front rows and shallower back rows, or deeper and shallower sides on the same side. Let's assume the front row is deeper than the back row, i.e. , After substituting, it becomes: ; The result is the same as in case 1; Case 3 involves one deep and three shallow cases. Assume the left front is deep and the rest are shallow. , After substituting, it becomes: ; The singularity was eliminated, but the denominator was only 1 times the limit value, resulting in a severe error amplification factor. Case 4 involves completely random height variations. Let... , , , After substituting, it becomes: ; The completely random height variation, due to the failure to follow the diagonal error cancellation logic, results in unstable performance in the real algorithm; Case 5 is the method of the present invention. , After substituting, it becomes: ; Therefore, in Under rigid constraints, The theoretical global maximum upper bound is always equal to Furthermore, within a three-dimensional cuboid space, only one topological structure, the "diagonal intersection extreme value distribution," can achieve this maximum value. Compared to random non-coplanar layouts, the determinant value of this invention achieves a significant leap forward. Under the same wave ranging noise, the Z-axis error of its solution output is mathematically forced to the theoretical minimum, and the system accuracy is superior to all currently known array arrangements.

[0032] The following description, in conjunction with the accompanying drawings, further illustrates the system structure of this invention. Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the catamaran-based platform consists of a left platform 1 and a right platform 2. The left and right platforms are fixedly connected by a crossbeam 15 and a crossbeam fixing seat 12 to form the catamaran-based platform. The system of this invention relies on the catamaran-based platform. The equipment mounting plate 13 spans between the plates to carry the core control equipment. The attitude measurement unit 3 is installed on the crossbeam 15 and located above the central axis of the catamaran-based platform to acquire the platform's six degrees of freedom motion data in real time. The ship is equipped with a left-side thruster 9 and a right-side thruster 10 on both sides of the stern to control the course; a Global Navigation Satellite System (GNSS) is installed inside the left-side platform 1, the right-side platform 2, and the attitude measurement unit of the catamaran ship platform, and a GNSS antenna 14 is installed on the top; the two ends of the A-type mast bracket 17 are fixedly connected to the left-side platform 1 and the right-side platform 2 of the catamaran ship platform, respectively. A panoramic camera 20 and mast reinforcing rib 21 are set on both sides of the A-type mast bracket 17. A mast rotating hinge 16 is installed at the bottom of the transverse support of the A-type mast bracket 17, and a radio communication antenna 18 and a tri-color navigation light 19 are installed on the top.

[0033] In the three-dimensional spatial layout of the underwater acoustic array, the central main transducer 4 is suspended directly below the geometric center of the catamaran; the four key edge receiving transducers are arranged at the four corners of the hull: among them, the left front edge receiving transducer 5 and the right rear edge receiving transducer 7 extend downwards significantly through long support rods 11, forming the first diagonal line with the deepest draft (i.e., reaching the maximum physical depth boundary). Conversely, the right front edge receiving transducer 6 and the left rear edge receiving transducer 8 are mounted on extremely short brackets close to the bottom of the ship, forming the second diagonal with the shallowest draft (i.e., draft close to 0 or the minimum boundary). This mechanical structure directly constructs a strict "diagonal high-low cross extreme value distribution" in three-dimensional space, providing a solid hardware physical foundation for the algorithm to completely eliminate Z-axis singularity and maximize matrix determinant.

[0034] The verification process of VDOP global extremum search based on feature difference in this invention is as follows: Figure 5 As shown, by setting a mesh traversal algorithm, the depths of the four transducers are... An exhaustive search of nearly 200,000 physical topological combinations is performed within the interval, with the horizontal axis representing the difference in system characteristic terms derived in this invention. The vertical axis represents the Z-axis accuracy decay factor (VDOP) calculated by the system. The scatter plot exhibits a strict "V"-shaped funnel distribution. When the difference between feature terms approaches 0 (i.e., similar heights or falling into sloping coplanarity), VDOP increases significantly, and the algorithm tends to diverge; however, in the entire exhaustive space, the absolute extreme value of 2.0 (i.e., 2) is reached only on the horizontal axis. When VDOP reaches its global minimum (marked by a red pentagram in the diagram), this unique point strictly corresponds to the diagonal extreme value staggered layout of this invention. , From a purely mathematical perspective, it has been proven that the mechanical layout of this invention is the globally unique optimal solution under the constraint space.

[0035] The Monte Carlo ranging noise limit immunity verification results of this invention are as follows: Figure 6 As shown, the true depth of the underwater target is set to 10 meters, and Gaussian white noise with a standard deviation of 2 cm is injected into the ideal slant range of the four sensors. 10,000 independent unconstrained least squares three-dimensional solutions are performed for each layout. The horizontal axis is the calculated Z-axis depth, and the vertical axis is the probability density (PDF). Scheme B (deep in front, shallow in back) diverges directly to infinity due to being trapped in an inclined coplanar singular matrix. The probability distribution curves of Scheme A (random staggered) and Scheme C (one deep and three shallow) are highly flattened, with Z-axis standard deviations reaching 0.991 m and 0.397 m, respectively, which greatly amplifies the error of small noise. Scheme D (diagonal extreme staggered) using the present invention exhibits a pulse-like convergence in its probability density distribution curve (blue), with a Z-axis standard deviation of only 0.194 m. Without increasing any adjustment and filtering computing power, this invention improves Z-axis stability several times by relying solely on the underlying spatial topology physical reconstruction, and forces the depth error variance to be compressed to an extremely low level, thus completely overcoming the natural geometric vulnerability of the catamaran short baseline system in the Z-axis direction.

[0036] The results of the three-dimensional dynamic spiral trajectory tracking and timing error verification of this invention are as follows: Figure 7 and Figure 8 As shown, the system simulates an underwater target performing a continuous spiral motion (lasting 200 seconds) and verifies its robustness under dynamic timing conditions with constant ranging noise (2 cm) interference. The spatial trajectory performance is as follows. Figure 6 As shown, the black solid line represents the actual target spiral trajectory. The red dots, representing the "random staggered solution trajectory," exhibit divergence and jaggedness in 3D space; while the blue dots, representing the "diagonal solution trajectory," are smoother and closer to the actual trajectory's circular surface. The Z-axis timing error is shown below. Figure 7 As shown, the real-time error of the system in the Z-axis (depth) direction is analyzed separately. The red curve (random layout) exhibits significant up-and-down oscillations, with the maximum instantaneous error exceeding 4 meters; while the error amplitude of the blue curve (layout of this invention) is kept within a smaller range. Quantitative analysis shows that this solution reduces the root mean square error (RMSE) of the dynamic trajectory's Z-axis from 1.362 m (random staggered layout) to 0.270 m (layout of this invention), improving dynamic noise resistance by 5.05 times. Cross-validation of the two graphs confirms that this invention provides an absolutely reliable Z-axis coordinate reference for continuous dynamic mapping during positioning.

[0037] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An underwater acoustic short baseline positioning system, characterized in that, include: Catamaran shipborne platform, attitude measurement unit, global navigation satellite system, diagonal extreme topological acoustic array and solution module; The diagonal extreme topology acoustic array consists of 5 underwater acoustic transducers, including 4 edge receiving transducers and 1 central main transducer. The central main transducer is installed at the bottom of the geometric centerline of the catamaran platform, and the 4 edge receiving transducers are installed at the four corners of the bottom of the catamaran platform. The 4 edge receiving transducers form a diagonal extreme topology structure with high and low intersections. The solution module has a built-in standard least squares method, receives ranging data from the diagonal extreme topological acoustic array, and outputs the estimated three-dimensional coordinates of the target. The extreme topology structure with diagonal high and low intersections includes transducers at the left front and right rear edges, which are mounted on the bottom of the catamaran platform via support rods, with a draft of the maximum physical lower limit. ; The front right and rear left edge receiving transducers adopt a bottom-mounted design, with a draft of the minimum physical depth boundary. ; The catamaran platform has a rectangular horizontal acoustic baseline with a length of [missing information]. Width is ; The attitude measurement unit and global navigation satellite system are mounted on the top of the catamaran platform; The calculation module is installed inside the cabin of the catamaran platform; The solution module incorporates the standard least squares method, receives ranging data from four edge receiving transducers, and outputs an estimated three-dimensional coordinate value of the target.

2. An underwater acoustic short baseline positioning method, using the underwater acoustic short baseline positioning system as described in claim 1, characterized in that, include: S1. Obtain the real-time coordinates of the four edge receiving transducers under the current attitude of the catamaran platform. The transducer depths of the left front and right rear edge receiving transducers are: The transducer depth of the receiving transducers at the right front and left rear edges is... ; S2. Using the three-dimensional attitude data of the catamaran-based platform measured in real time by the attitude measurement unit, the displacement of the support rod caused by the lever arm effect is compensated based on the three-dimensional attitude data, and the real-time coordinates of each edge receiving transducer are corrected. S3. Acoustic signals are emitted through the central main transducer, and response signals from the target are received by four edge receiving transducers. The straight-line distance between each edge receiving transducer and the target is measured. S4. Using the real-time coordinates of the corrected edge receiving transducers as known quantities and the straight-line distance between each edge receiving transducer and the target as observed values, construct a spherical distance equation with the target's true coordinates as unknowns. Perform differential linearization on the spherical distance equation to obtain the core observation matrix. S5. Introduce the ranging acoustic vector, construct a system of linear equations based on the core observation matrix and the ranging acoustic vector, and solve the system of linear equations using the least squares method to obtain the estimated three-dimensional coordinates of the target. S1 includes S1.1, setting the spatial coordinate system, and the coordinates of the four edge receiving transducers are as follows: , , , ; The coordinates of the left front edge receiving transducer. The coordinates of the right front edge receiving transducer. The coordinates of the right rear edge receiving transducer. The coordinates of the left rear edge receiving transducer; The depth coordinates of the receiver transducer at the left front edge. The depth of the receiving transducer at the right front edge. The depth coordinates of the right rear edge receiving transducer. The depth coordinates of the left rear edge receiving transducer; S1 includes S1.2, and satisfy: ； and satisfy: ； S2 includes the use of an attitude measurement unit to obtain the roll angle of the catamaran platform in real time. Pitch angle and heading angle ; Based on the geometric length and installation position of the support rod, the lever arm effect displacement of the catamaran shipborne platform is compensated, and the real-time coordinates of each edge receiving transducer are corrected. S3 includes the following: the straight-line distance between each edge receiving transducer and the target is: ； In the formula, For the index of the edge receiving transducer, For the first The distance between an edge receiving transducer and the target. , and For the first Corrected 3D coordinates of an edge receiving transducer; S4 includes, assuming the target's true coordinates are... , combined By linearizing the spherical distance equations using difference, we obtain the core observation matrix. : ； S5 includes the introduction of ranging acoustic vectors. Construct a system of linear equations: ； The linearized system of equations is solved using the least squares method, and the equations are iterated until convergence, outputting the estimated three-dimensional coordinates of the target.

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