Unmanned ship formation towed floating base array deep sea cooperative positioning system and method

Abstract

This invention discloses a deep-sea collaborative positioning system and method using an unmanned surface vessel (USV) formation towed floating array, belonging to the field of marine surveying and underwater acoustic positioning technology. It is used for deep-sea target positioning, and the system includes a surface subsystem and an underwater subsystem. The method includes calculating corrected coordinates of towed acoustic nodes based on USV measurement data; calculating the true sound center of the towed acoustic nodes based on their attitude and transducer factory offset vectors; constructing a set of observation equations and calculating the estimated distance and residual vector after iteration; calculating the weight coefficients corresponding to each towed acoustic node and constructing a dynamic observation weight matrix; and outputting the final target coordinates after solving the equations. This invention overcomes the technical bottlenecks of traditional shipborne single-unit equipment being susceptible to interference in shallow water and geometric divergence in positioning results due to aperture limitations in deep water by using multiple USVs to tow acoustic nodes to deep water layers, thus improving the positioning accuracy of deep-sea targets.

Description

Technical Field

[0001] This invention discloses a deep-sea collaborative positioning system and method for unmanned vessel formation towed floating array, belonging to the field of marine surveying and underwater acoustic positioning technology. Background Technology

[0002] As marine resource development expands into deeper waters, the requirements for positioning accuracy of underwater vehicles (AUVs / ROVs) and seabed targets are increasing. Currently, deep-sea positioning mainly relies on shipborne short baseline (SBL) or ultra-short baseline (USBL) systems. However, in practical engineering applications, existing ship-mounted positioning systems face significant physical bottlenecks in shallow water transition zones, limiting the efficiency of deep-sea operations.

[0003] To ensure deep-sea detection range (e.g., >1000m), existing SBL systems typically employ lower frequencies (e.g., 8-16kHz) and larger transmission pulse widths. When operating in shallow water, due to the extremely short round-trip time of the sound waves, the echo signal is easily masked by the transmission aftershocks due to the residual vibration effect of the transmitting transducer and the blanking period of the receiver, creating a detection blind zone. This leads to ranging anomalies during the shallow water commissioning phase.

[0004] The water layer 0-15m below the sea surface is a region with a complex acoustic environment. When shipborne transducers operate close to the water surface, the emitted sound waves will form multipath reflections between the sea surface and the seabed. Due to the coherent destructive effect of the direct wave and the reflected wave from the sea surface, signal strength fluctuations are easily caused, resulting in positioning data jumps and sound velocity profile (SVP) refraction bias.

[0005] The baseline array spacing of a single-ship SBL system is limited by the ship's size (typically 2 to 3 meters). In deep-sea positioning operations, because the target depth is much greater than the baseline aperture, the geometrical dilution factor (GDOP) increases significantly with depth. At this point, minute surface observation noise is amplified by the geometric configuration, leading to a large divergence error in the depth direction of the positioning results. Summary of the Invention

[0006] The purpose of this invention is to provide a deep-sea collaborative positioning system and method for unmanned vessel formation towing a floating array, in order to solve the problem in the prior art that it is difficult to have large-aperture detection capabilities while physically avoiding surface acoustic interference.

[0007] A deep-sea collaborative positioning system and method for unmanned surface vessels towing floating arrays, including surface and underwater subsystems; The water surface subsystem includes An unmanned boat, The unmanned surface vessel is equipped with a global navigation satellite system positioning module, attitude measurement module, main control unit, winch mechanism and shipborne high-frequency short baseline array; Underwater subsystems include A towed acoustic node, which is connected to the winch mechanism of the unmanned vessel via a cable. The towed acoustic node includes an upward-looking high-frequency transducer, a downward-looking low-frequency transducer, an attitude measurement unit, and a pressure depth sensor.

[0008] S1. Define the geographic coordinate system, the hull coordinate system, and the towing node coordinate system; S2. By measuring the acoustic round-trip time between the towed acoustic node's upward-looking high-frequency transducer and the shipborne high-frequency short-baseline array transducer element, the corresponding acoustic slant range measurement value is obtained. Combined with the fixed coordinates of the transducer element in the ship's coordinate system, a spherical intersection equation system is established. The estimated value of the relative position vector of the towed acoustic node in the ship's coordinate system is obtained by solving it using the least squares method. Combined with the coordinates of the unmanned vessel, the attitude matrix of the unmanned vessel, the fixed arm vector from the global navigation satellite system antenna to the center of gravity of the unmanned vessel, and the depth value of the towed acoustic node measured by the pressure depth sensor, the corrected coordinates of the towed acoustic node are calculated. S3. Calculate the true sound center of the towed acoustic node based on the attitude rotation matrix of the towed acoustic node and the factory offset vector of the sound center of the downward-looking low-frequency transducer relative to the origin of the towed node coordinate system. S4. Based on the actual sound emission center of each towed acoustic node and the equivalent branch acoustic slant distance between each towed acoustic node and the target, construct the observation equation set and Jacobian matrix. According to the three-axis angular velocity norm output by the inertial measurement unit of each towed acoustic node, calculate the weight coefficient corresponding to each towed acoustic node and construct the dynamic observation weight matrix. Use the weighted least squares method to iteratively calculate the target position correction. When the target position correction is less than the preset threshold, output the final target coordinates.

[0009] The global navigation satellite system positioning module is the global navigation satellite system, and the attitude measurement module is the inertial measurement unit; Shipborne high-frequency short baseline array The draggable acoustic node is placed in the still water layer; A hierarchical cascaded positioning architecture is adopted, including a first-level positioning link and a second-level positioning link; The first-level positioning link uses high-frequency signals between the shipborne high-frequency short-baseline array and the towed acoustic node. Perform relative positioning; The second-level positioning link uses low-frequency signals between the towed acoustic node and the target. Perform distance measurement and intersection positioning; ; Shipborne high-frequency short baseline arrays include One transducer array element .

[0010] S1 includes the use of the northeast geodetic coordinate system. Hull coordinate system The axis points towards the bow of the ship. The axis points to the starboard side of the hull. The axis is perpendicular to the bottom of the ship, pointing downwards, with the origin at... Located at the center of gravity of the unmanned vessel; Drag acoustic node coordinate system The axis points towards the head of the drag acoustic node. The axis points to the starboard side of the towed acoustic node. The vertical axis drags the acoustic node downwards, with the origin at the top. Located at the geometric center of the drag acoustic node.

[0011] S2 includes, let... Indexing for unmanned vessels and towed acoustic nodes. Let the first Unmanned boats equipped with One shipborne high-frequency short-baseline array transducer element. ,set up For transducer array element index, ; By dragging the acoustic node, the high-frequency transducer is viewed and connected to the first... The acoustic round-trip time of each transducer element is used to obtain the corresponding acoustic slant range measurement. , No. Fixed coordinates of each transducer element in the ship's coordinate system for: ; In the formula, , and For the first The three-dimensional coordinates of each transducer element in the ship's coordinate system It is the transpose symbol; Let the relative position vector of the towed acoustic node in the ship's coordinate system be... for: ; In the formula, , and The three-dimensional coordinates of the towed acoustic node in the ship's coordinate system; Establish the system of equations for spherical intersection: ; In the formula, For the first Measurement error of acoustic slant range measurement value corresponding to each transducer array element; Solving the system of equations for the intersection of spheres using the least squares method yields the following results: The estimated value; Let the coordinates of the unmanned vessel measured by the Global Navigation Satellite System be... The attitude matrix of the unmanned surface vessel measured by the inertial measurement unit is: The vector of the fixed arm from the global navigation satellite system antenna to the center of gravity of the unmanned vessel is Preliminary solution location of the dragged acoustic node in the geographic coordinate system for: ; Let the depth value of the dragged acoustic node measured by the pressure depth sensor be... The revised first Coordinates of draggable acoustic nodes for: ; In the formula, for of Axis coordinates for of Axis coordinates.

[0012] S3 includes, assuming the attitude rotation matrix of the towed acoustic node, measured by the inertial measurement unit of the towed acoustic node, is... The sound emission center of the dragged acoustic node's downward-looking low-frequency transducer is relative to The factory offset vector is After attitude compensation, the first The true sound-generating center of each draggable acoustic node The coordinates are: .

[0013] S4 includes, S4.1, setting the target location. for: ; In the formula, , and The three-dimensional coordinates of the target location; The equivalent branch acoustic slant distances between each towed acoustic node and the target are as follows: Establish the observation equation system: ; In the formula, For the first Error term of the equivalent branch acoustic slant distance measured at each dragged acoustic node. It is an L2 norm.

[0014] S4 includes S4.2, which uses the weighted least squares method to iteratively calculate the target position correction, including assuming the first... Initial approximate coordinates of the target in the next iteration for: ; In the formula, For the number of iterations, , and For the first The target's three-dimensional coordinates at the next iteration; Calculate the first The estimated distance of the equivalent branch acoustic slant range in the next iteration. : ; Calculate the first The residual vector of the next iteration : ; ; ; In the formula, This is the measured equivalent acoustic slant moment vector. For the first The estimated acoustic slant moment vector for each iteration; Constructing the Jacobian matrix : ; In the formula, , and for The three-dimensional coordinates.

[0015] S4 includes, S4.3, the triaxial angular velocity norm output by the inertial measurement unit of the towed acoustic node. calculate : ; In the formula, For the first The weight coefficients corresponding to each draggable acoustic node. This is the weight decay coefficient. For the natural constant An exponential function with base 0; Constructing a dynamic observation weight matrix : ; In the formula, To place the elements in parentheses sequentially on the main diagonal of the matrix.

[0016] S4 includes S4.4, which uses the weighted least squares method to solve the... Position correction amount : ; Update target coordinates: ; In the formula, For the first The target's three-dimensional coordinates at the next iteration; when If the value is less than a preset threshold, stop the iteration and output the final target coordinates.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention utilizes multiple unmanned vessels to tow acoustic nodes to the deep water layer via flexible cables to physically avoid sea surface wave noise and surface waveguide interference, effectively overcoming the technical bottlenecks of traditional shipborne single equipment being susceptible to interference in shallow water areas and geometric divergence of positioning results due to aperture limitations in deep sea areas, thereby improving the positioning accuracy of deep-sea targets. Attached Figure Description

[0018] Figure 1 This is a flowchart of the technology of this invention; Figure 2 This is a bar chart comparing the accuracy statistics of four architectures; Figure 3 This is a scatter plot of the positioning points for each scheme; Figure 4 This is a comparison chart of the landing point distribution of various collaborative networking schemes; Figure 5 These are the action distance and error characteristic curves of high-frequency and mid-to-low-frequency acoustic signals; Figure 6 This is a bar chart comparing the comprehensive observation errors in the deep sea using different acoustic frequency architectures. Detailed Implementation

[0019] 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.

[0020] A deep-sea collaborative positioning system and method for unmanned surface vessels towing floating arrays, including surface and underwater subsystems; The water surface subsystem includes An unmanned boat, The unmanned surface vessel is equipped with a global navigation satellite system positioning module, attitude measurement module, main control unit, winch mechanism and shipborne high-frequency short baseline array; Underwater subsystems include A towed acoustic node, which is connected to the winch mechanism of the unmanned vessel via a cable. The towed acoustic node includes an upward-looking high-frequency transducer, a downward-looking low-frequency transducer, an attitude measurement unit, and a pressure depth sensor.

[0021] S1. Define the geographic coordinate system, the hull coordinate system, and the towing node coordinate system; S2. By measuring the acoustic round-trip time between the towed acoustic node's upward-looking high-frequency transducer and the shipborne high-frequency short-baseline array transducer element, the corresponding acoustic slant range measurement value is obtained. Combined with the fixed coordinates of the transducer element in the ship's coordinate system, a spherical intersection equation system is established. The estimated value of the relative position vector of the towed acoustic node in the ship's coordinate system is obtained by solving it using the least squares method. Combined with the coordinates of the unmanned vessel, the attitude matrix of the unmanned vessel, the fixed arm vector from the global navigation satellite system antenna to the center of gravity of the unmanned vessel, and the depth value of the towed acoustic node measured by the pressure depth sensor, the corrected coordinates of the towed acoustic node are calculated. S3. Calculate the true sound center of the towed acoustic node based on the attitude rotation matrix of the towed acoustic node and the factory offset vector of the sound center of the downward-looking low-frequency transducer relative to the origin of the towed node coordinate system. S4. Based on the actual sound emission center of each towed acoustic node and the equivalent branch acoustic slant distance between each towed acoustic node and the target, construct the observation equation set and Jacobian matrix. According to the three-axis angular velocity norm output by the inertial measurement unit of each towed acoustic node, calculate the weight coefficient corresponding to each towed acoustic node and construct the dynamic observation weight matrix. Use the weighted least squares method to iteratively calculate the target position correction. When the target position correction is less than the preset threshold, output the final target coordinates.

[0022] The global navigation satellite system positioning module is the global navigation satellite system, and the attitude measurement module is the inertial measurement unit; Shipborne high-frequency short baseline array The draggable acoustic node is placed in the still water layer; A hierarchical cascaded positioning architecture is adopted, including a first-level positioning link and a second-level positioning link; The first-level positioning link uses high-frequency signals between the shipborne high-frequency short-baseline array and the towed acoustic node. Perform relative positioning; The second-level positioning link uses low-frequency signals between the towed acoustic node and the target. Perform distance measurement and intersection positioning; ; Shipborne high-frequency short baseline arrays include One transducer array element .

[0023] S1 includes the use of the northeast geodetic coordinate system. Hull coordinate system The axis points towards the bow of the ship. The axis points to the starboard side of the hull. The axis is perpendicular to the bottom of the ship, pointing downwards, with the origin at... Located at the center of gravity of the unmanned vessel; Drag acoustic node coordinate system The axis points towards the head of the drag acoustic node. The axis points to the starboard side of the towed acoustic node. The vertical axis drags the acoustic node downwards, with the origin at the top. Located at the geometric center of the drag acoustic node.

[0024] S2 includes, let... Indexing for unmanned vessels and towed acoustic nodes. Let the first Unmanned boats equipped with One shipborne high-frequency short-baseline array transducer element. ,set up For transducer array element index, ; By dragging the acoustic node, the high-frequency transducer is viewed and connected to the first... The acoustic round-trip time of each transducer element is used to obtain the corresponding acoustic slant range measurement. , No. Fixed coordinates of each transducer element in the ship's coordinate system for: ; In the formula, , and For the first The three-dimensional coordinates of each transducer element in the ship's coordinate system It is the transpose symbol; Let the relative position vector of the towed acoustic node in the ship's coordinate system be... for: ; In the formula, , and The three-dimensional coordinates of the towed acoustic node in the ship's coordinate system; Establish the system of equations for spherical intersection: ; In the formula, For the first Measurement error of acoustic slant range measurement value corresponding to each transducer array element; Solving the system of equations for the intersection of spheres using the least squares method yields the following results: The estimated value; Let the coordinates of the unmanned vessel measured by the Global Navigation Satellite System be... The attitude matrix of the unmanned surface vessel measured by the inertial measurement unit is: The vector of the fixed arm from the global navigation satellite system antenna to the center of gravity of the unmanned vessel is Preliminary solution location of the dragged acoustic node in the geographic coordinate system for: ; Let the depth value of the dragged acoustic node measured by the pressure depth sensor be... The revised first Coordinates of draggable acoustic nodes for: ; In the formula, for of Axis coordinates for of Axis coordinates.

[0025] S3 includes, assuming the attitude rotation matrix of the towed acoustic node, measured by the inertial measurement unit of the towed acoustic node, is... The sound emission center of the dragged acoustic node's downward-looking low-frequency transducer is relative to The factory offset vector is After attitude compensation, the first The true sound-generating center of each draggable acoustic node The coordinates are: .

[0026] S4 includes, S4.1, setting the target location. for: ; In the formula, , and The three-dimensional coordinates of the target location; The equivalent branch acoustic slant distances between each towed acoustic node and the target are as follows: Establish the observation equation system: ; In the formula, For the first Error term of the equivalent branch acoustic slant distance measured at each dragged acoustic node. It is an L2 norm.

[0027] S4 includes S4.2, which uses the weighted least squares method to iteratively calculate the target position correction, including assuming the first... Initial approximate coordinates of the target in the next iteration for: ; In the formula, For the number of iterations, , and For the first The target's three-dimensional coordinates at the next iteration; Calculate the first The estimated distance of the equivalent branch acoustic slant range in the next iteration. : ; Calculate the first The residual vector of the next iteration : ; ; ; In the formula, This is the measured equivalent acoustic slant moment vector. For the first The estimated acoustic slant moment vector for each iteration; Constructing the Jacobian matrix : ; In the formula, , and for The three-dimensional coordinates.

[0028] S4 includes, S4.3, the triaxial angular velocity norm output by the inertial measurement unit of the towed acoustic node. calculate : ; In the formula, For the first The weight coefficients corresponding to each draggable acoustic node. This is the weight decay coefficient. For the natural constant An exponential function with base 0; Constructing a dynamic observation weight matrix : ; In the formula, To place the elements in parentheses sequentially on the main diagonal of the matrix.

[0029] S4 includes S4.4, which uses the weighted least squares method to solve the... Position correction amount : ; Update target coordinates: ; In the formula, For the first The target's three-dimensional coordinates at the next iteration; when If the value is less than a preset threshold, stop the iteration and output the final target coordinates.

[0030] The main control unit of this invention is a core information processing and decision-making module installed on an unmanned surface vessel (USV). It receives acoustic ranging data from the USV's Global Navigation Satellite System (GNSS) positioning module, attitude measurement module (IMU), and onboard high-frequency short-baseline array. It calculates the relative position of the towed acoustic nodes in the ship's coordinate system and then corrects this to obtain high-precision coordinates of the towed nodes in the geodetic coordinate system. It coordinates the formation behavior of multiple USVs, such as controlling the winch mechanism to raise and lower cables to deploy the towed acoustic nodes into the still water layer. Simultaneously, it may exchange data with the main control units of other USVs to achieve synchronous observation of multi-node large-aperture floating arrays. In the second-level positioning link, the main control unit collects the equivalent acoustic slant range to the target sent back by each towed acoustic node. Combining this with the attitude and depth information of each node, it executes a weighted least squares iterative algorithm to calculate the final three-dimensional coordinates of the target.

[0031] The following description, in conjunction with the accompanying drawings and embodiments, further illustrates the process of this invention. Figure 1 As shown, the operation of the surface subsystem of this invention includes: unmanned surface vessels navigating to the operational area, releasing towed nodes (i.e., towed acoustic nodes), performing shipborne high-frequency SBL (shipborne high-frequency short baseline) measurement (determining the relative position vector of the nodes), and acquiring shipborne GNSS (Global Navigation Satellite System) and IMU (Inertial Measurement Unit) data; the towed nodes receive the acquired shipborne GNSS and IMU data, perform node depth sensor measurement, node IMU attitude detection, construct a long baseline array, and acquire mid-to-low frequency acoustic slant range. First-level positioning (calculating the absolute position of the nodes) is performed based on the shipborne high-frequency SBL measurement results, and node coordinates are determined based on the shipborne high-frequency SBL measurement results. Axis correction (replacing acoustic with depth sensor data) Based on the node depth sensor measurement results, the initial geographic coordinates of the node are calculated (fusion of GNSS + relative position + depth constraints). Based on the node IMU attitude monitoring results, lever effect / acoustic center correction is performed (based on attitude calculation of the true position of the low-frequency transducer). Then, the second-level positioning (collaborative calculation of deep-sea target) is entered. The node attitude stability monitoring is judged (i.e., whether the IMU angular velocity is greater than the set angular velocity threshold, which is set to 0.1 rad / s in this embodiment). If the IMU angular velocity is greater than the threshold, the observation weight of the node is reduced. If the IMU angular velocity is less than or equal to the threshold, the normal weight is maintained. Then, based on the node IMU attitude monitoring results and the mid-to-low frequency acoustic slant range, weighted least squares / Kalman filtering is performed (fusion of multi-node distance information to construct equations) to output high-precision coordinates of the deep-sea target.

[0032] In this embodiment of the invention, the still water layer is at a depth of 10 to 20 meters underwater, with a preset threshold of 0.01 meters. , The average water depth is approximately 1000 meters. The initial base station accuracy statistics for each towed acoustic node in the first-stage positioning are shown in Table 1. Table 1. Initial Base Station Accuracy Statistics for Each Towed Acoustic Node in Level 1 Positioning ; As shown in Table 1, the average horizontal errors of the nodes in the X and Y axes stabilized at around 0.21m, while the Z-axis error was controlled to the order of 0.02m. This mechanism effectively suppressed surface noise and prevented the significant cascading amplification of errors from the first stage to the second stage of the large network.

[0033] The results of comparing the method of this invention with those of existing conventional technical solutions are shown in the following statistical data on the accuracy of terminal target positioning: Figure 2 As shown in Table 2: Table 2. Comparison Statistics of Ultimate Cooperative Positioning Accuracy for Deep-Sea Targets ; like Figure 2 As shown in Table 2, Figure 2 As shown in Table 2, the method (G4 scheme) provided by this invention exhibits extremely high accuracy in deep-sea collaborative positioning, with a 3D integrated error of only 1.3m. Compared to the divergence error of up to 148.46m in the traditional single-ship SBL scheme (G1), and the error magnitude of over 10m in conventional multi-ship surface direct measurement schemes (G2, G3), the method of this invention improves the deep-sea positioning accuracy by an order of magnitude and significantly reduces the error divergence phenomenon, especially in the Z-axis direction.

[0034] As attached Figure 3As shown in the panoramic scatter plot, the G1 scheme (traditional single-ship SBL) is limited by a physical aperture of less than 3 meters. When facing long-distance deep-sea measurements, its Jacobian matrix is ​​ill-conditioned, and its geometric accuracy is diluted by a large factor. After being affected by conventional surface noise, the positioning results exhibit divergent characteristics (overall error exceeding the order of hundreds of meters). This invention constructs a baseline aperture of hundreds of meters through multi-ship distributed networking, effectively improving the spatial geometry. Although the G3 scheme adopts multi-ship large-aperture networking, as... Figure 4 The green dots indicate the sound velocity profile (SVP) during sound wave propagation when the transducer is located between 0 and 2 meters above the water surface, influenced by waves and the complex surface acoustic velocity profile (SVP). (See attached image.) Figure 4 As shown by the blue star-shaped scattering, the present invention physically lowers the transmitting / receiving nodes to a 15m still water layer, avoiding acoustic interference from the surface mixed water. Simultaneously, relying on the absolute coordinates of the first stage (see Table 1) and the high-precision constraint of the Z-axis, the measurement variance of the second-stage long baseline intersection is effectively reduced. The system controls the overall target positioning error to within 1.30m, with all error indicators significantly superior to existing comparative technologies, effectively improving the positioning accuracy of deep-sea targets. The bias effect causes a significant extension and divergence error (approximately 11.73m) in the Z-axis (depth) direction of the intersection positioning results.

[0035] Figure 5 The characteristics of ranging error with distance are shown for high frequency (blue) and mid-to-low frequency (red). The high frequency error is extremely small in the near field (15m), but diverges exponentially in the far field (1000m). The mid-to-low frequency error is slightly larger in the near field, but increases slowly linearly in the far field and is still usable. Figure 6 The overall error of four different frequency architectures at a depth of 1000m was compared. Scenario 1 (all low frequency at the surface) was 2.85m; Scenario 2 (two levels of all low frequency) was 2.36m; Scenario 3 (two levels of all high frequency) had an error as high as 15.93m due to attenuation and divergence; Scenario 4 of the present invention (high + low) gives full play to the advantages of both and has the lowest error of 1.85m.

[0036] 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. A deep-sea cooperative positioning system for unmanned vessel swarm towed floating arrays, characterized in that, Includes surface subsystems and underwater subsystems; The water surface subsystem includes An unmanned boat, The unmanned surface vessel is equipped with a global navigation satellite system positioning module, attitude measurement module, main control unit, winch mechanism and shipborne high-frequency short baseline array; Underwater subsystems include A towed acoustic node, which is connected to the winch mechanism of the unmanned vessel via a cable. The towed acoustic node includes an upward-looking high-frequency transducer, a downward-looking low-frequency transducer, an attitude measurement unit, and a pressure depth sensor.

2. The unmanned vessel formation towed floating array deep-sea cooperative positioning system as described in claim 1, characterized in that, The global navigation satellite system positioning module is the global navigation satellite system, and the attitude measurement module is the inertial measurement unit; Shipborne high-frequency short baseline array The draggable acoustic node is placed in the still water layer; A hierarchical cascaded positioning architecture is adopted, including a first-level positioning link and a second-level positioning link; The first-level positioning link uses high-frequency signals between the shipborne high-frequency short-baseline array and the towed acoustic node. Perform relative positioning; The second-level positioning link uses low-frequency signals between the towed acoustic node and the target. Perform distance measurement and intersection positioning; ； Shipborne high-frequency short baseline arrays include One transducer array element .

3. A deep-sea cooperative positioning method using an unmanned vessel swarm towed floating array, employing the deep-sea cooperative positioning system of the unmanned vessel swarm towed floating array as described in claim 2, characterized in that... include: S1. Define the geographic coordinate system, the hull coordinate system, and the towing node coordinate system; S2. By measuring the acoustic round-trip time between the towed acoustic node's upward-looking high-frequency transducer and the shipborne high-frequency short-baseline array transducer element, the corresponding acoustic slant range measurement value is obtained. Combined with the fixed coordinates of the transducer element in the ship's coordinate system, a spherical intersection equation system is established. The estimated value of the relative position vector of the towed acoustic node in the ship's coordinate system is obtained by solving it using the least squares method. Combined with the coordinates of the unmanned vessel, the attitude matrix of the unmanned vessel, the fixed arm vector from the global navigation satellite system antenna to the center of gravity of the unmanned vessel, and the depth value of the towed acoustic node measured by the pressure depth sensor, the corrected coordinates of the towed acoustic node are calculated. S3. Calculate the true sound center of the towed acoustic node based on the attitude rotation matrix of the towed acoustic node and the factory offset vector of the sound center of the downward-looking low-frequency transducer relative to the origin of the towed node coordinate system. S4. Based on the actual sound emission center of each towed acoustic node and the equivalent branch acoustic slant distance between each towed acoustic node and the target, construct the observation equation set and Jacobian matrix. According to the three-axis angular velocity norm output by the inertial measurement unit of each towed acoustic node, calculate the weight coefficient corresponding to each towed acoustic node and construct the dynamic observation weight matrix. Use the weighted least squares method to iteratively calculate the target position correction. When the target position correction is less than the preset threshold, output the final target coordinates.

4. The deep-sea cooperative positioning method for unmanned vessel formation towed floating arrays as described in claim 3, characterized in that, S1 includes the use of the northeast geodetic coordinate system. Hull coordinate system The axis points towards the bow of the ship. The axis points to the starboard side of the hull. The axis is perpendicular to the bottom of the ship, pointing downwards, with the origin at... Located at the center of gravity of the unmanned vessel; Drag acoustic node coordinate system The axis points towards the head of the drag acoustic node. The axis points to the starboard side of the towed acoustic node. The vertical axis drags the acoustic node downwards, with the origin at the top. Located at the geometric center of the drag acoustic node.

5. The deep-sea cooperative positioning method for unmanned vessel formation towing floating arrays as described in claim 4, characterized in that, S2 includes, let... Indexing for unmanned vessels and towed acoustic nodes. Let the first Unmanned boats equipped with One shipborne high-frequency short-baseline array transducer element. ,set up For transducer array element index, ; By dragging the acoustic node, the high-frequency transducer is viewed and connected to the first... The acoustic round-trip time of each transducer element is used to obtain the corresponding acoustic slant range measurement. , No. Fixed coordinates of each transducer element in the ship's coordinate system for: ； In the formula, , and For the first The three-dimensional coordinates of each transducer element in the ship's coordinate system It is the transpose symbol; Let the relative position vector of the towed acoustic node in the ship's coordinate system be... for: ； In the formula, , and The three-dimensional coordinates of the towed acoustic node in the ship's coordinate system; Establish the system of equations for spherical intersection: ； In the formula, For the first Measurement error of acoustic slant range measurement value corresponding to each transducer array element; Solving the system of equations for the intersection of spheres using the least squares method yields the following results: The estimated value; Let the coordinates of the unmanned vessel measured by the Global Navigation Satellite System be... The attitude matrix of the unmanned surface vessel measured by the inertial measurement unit is: The vector of the fixed arm from the global navigation satellite system antenna to the center of gravity of the unmanned vessel is Preliminary solution location of the dragged acoustic node in the geographic coordinate system for: ； Let the depth value of the dragged acoustic node measured by the pressure depth sensor be... The revised first Coordinates of draggable acoustic nodes for: ； In the formula, for of Axis coordinates for of Axis coordinates.

6. The deep-sea cooperative positioning method for unmanned vessel formation towed floating arrays as described in claim 5, characterized in that, S3 includes, assuming the attitude rotation matrix of the towed acoustic node, measured by the inertial measurement unit of the towed acoustic node, is... The sound emission center of the dragged acoustic node's downward-looking low-frequency transducer is relative to The factory offset vector is After attitude compensation, the first The true sound-generating center of each draggable acoustic node The coordinates are: 。 7. The deep-sea cooperative positioning method for unmanned vessel formation towed floating arrays as described in claim 6, characterized in that, S4 includes, S4.1, setting the target location. for: ； In the formula, , and The three-dimensional coordinates of the target location; The equivalent branch acoustic slant distances between each towed acoustic node and the target are as follows: Establish the observation equation system: ； In the formula, For the first Error term of the equivalent branch acoustic slant distance measured at each dragged acoustic node. It is an L2 norm.

8. The deep-sea cooperative positioning method for unmanned vessel formation towed floating arrays as described in claim 7, characterized in that, S4 includes S4.2, which uses the weighted least squares method to iteratively calculate the target position correction, including assuming the first... Initial approximate coordinates of the target in the next iteration for: ； In the formula, For the number of iterations, , and For the first The target's three-dimensional coordinates at the next iteration; Calculate the first The estimated distance of the equivalent branch acoustic slant range in the next iteration. : ； Calculate the first The residual vector of the next iteration : ； ； ； In the formula, This is the measured equivalent acoustic slant moment vector. For the first The estimated acoustic slant moment vector for each iteration; Constructing the Jacobian matrix : ； In the formula, , and for The three-dimensional coordinates.

9. The deep-sea cooperative positioning method for unmanned vessel formation towed floating arrays as described in claim 8, characterized in that, S4 includes, S4.3, the triaxial angular velocity norm output by the inertial measurement unit of the towed acoustic node. calculate : ； In the formula, For the first The weight coefficients corresponding to each draggable acoustic node. This is the weight decay coefficient. For the natural constant An exponential function with base 0; Constructing a dynamic observation weight matrix : ； In the formula, To place the elements in parentheses sequentially on the main diagonal of the matrix.

10. The deep-sea cooperative positioning method for unmanned vessel formation towed floating arrays as described in claim 9, characterized in that, S4 includes S4.4, which uses the weighted least squares method to solve the... Position correction amount : ； Update target coordinates: ； In the formula, For the first The target's three-dimensional coordinates at the next iteration; when If the value is less than a preset threshold, stop the iteration and output the final target coordinates.

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