Underwater mission-oriented multi-path suppression and airborne base station cooperative positioning system

Abstract

The application provides a multi-path suppression and airborne base station cooperative positioning system for underwater tasks, which comprises an airborne base station module, an underwater node module, a trusted measurement extraction module and a cooperative calculation positioning module; the airborne base station module is used for constructing an airborne positioning reference network for underwater target positioning; the underwater node module is used for completing positioning information transmission between the airborne base station module; the trusted measurement extraction module is used for extracting trusted positioning observations of the airborne base station module; and the cooperative calculation positioning module is used for combining the trusted observations of multiple airborne base stations to jointly calculate the position information of the underwater node; and the application realizes stable and highly reliable positioning of the underwater node in a complex underwater acoustic environment by combining multi-path trusted modeling and robust cooperative calculation.

Description

Technical Field

[0001] This invention relates to the field of underwater mission positioning technology, and in particular to a multipath suppression and airborne base station cooperative positioning system for underwater missions. Background Technology

[0002] With the continuous development of tasks such as marine exploration, underwater inspection, underwater search and rescue, and collaborative operations of underwater equipment, higher requirements are placed on the real-time positioning accuracy and stability of underwater targets. Due to the limitations of the underwater environment, electromagnetic waves are severely attenuated in water, and underwater positioning usually relies on underwater acoustic signals to complete ranging and positioning. However, underwater acoustic channels have the characteristics of slow propagation speed, limited bandwidth, and strong time variability. Especially in shallow seas or complex sea conditions, underwater acoustic signals are easily affected by reflections from the sea surface, seabed, and environmental structures, forming obvious multipath propagation phenomena, which adversely affect positioning accuracy and reliability.

[0003] Existing underwater positioning methods mostly use fixed base stations or a single mobile platform as positioning references. In multipath environments, they typically select the earliest arrival path or the path with the largest amplitude as effective ranging information for positioning calculation. However, in practical applications, such methods are prone to changes or drifts in positioning results due to errors in main path determination, abnormal ranging, or environmental changes, making it difficult to meet the requirements for continuous and stable positioning under complex mission conditions. On the other hand, with the increasing application of aerial platforms such as UAVs and unmanned surface vessels in marine operations, building flexible underwater positioning reference networks using aerial platforms has become a development trend. However, the maneuverability and attitude changes of the aerial platforms themselves further exacerbate the uncertainty of underwater positioning.

[0004] Therefore, how to effectively address the ranging uncertainty caused by underwater acoustic multipath propagation in underwater positioning scenarios involving airborne platforms, and how to achieve stable and reliable positioning of underwater nodes under multi-base station conditions, remains a pressing technical problem that needs to be solved in the field of underwater positioning technology.

[0005] A review of publicly available technical solutions reveals that CN118463991A proposes a UUV cooperative positioning method that considers the positioning error of the master node, addressing the technical problem of the impact of master node position information errors on positioning. First, a measurement model is established to analyze the impact of master node position errors on the positioning performance of child nodes. Then, a state-dimensional expansion model and a cooperative measurement model are established in a geocentric-geofixed coordinate system. When a child node does not receive measurement information, the state model is 15-dimensional. When measurement information is received, the velocity and position errors of the master node are added to the state, and the relationship between the expanded state model and the measurement information is established. Finally, the state information of the child nodes is filtered and updated. This invention effectively improves the positioning accuracy of child nodes by establishing a new state-dimensional expansion model and a cooperative measurement model, providing high-precision position information for subsequent collaborative system path planning, task allocation, and other aspects. However, this scheme still relies on the assumption of single measurement validity in complex multipath environments, addressing the modeling and compensation of the master node's own positioning error. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of current systems by proposing a multipath suppression and airborne base station cooperative positioning system for underwater missions.

[0007] The present invention adopts the following technical solution:

[0008] A multipath suppression and airborne base station cooperative positioning system for underwater missions is disclosed. The system includes an airborne base station module, an underwater node module, a reliable measurement extraction module, and a cooperative solution positioning module. The airborne base station module is used to construct an airborne positioning reference network for underwater target positioning. The underwater node module is used to complete the transmission of positioning information with the airborne base station module. The reliable measurement extraction module is used to extract reliable positioning observations from the airborne base station module. The cooperative solution positioning module is used to combine the reliable observations from multiple airborne base stations to perform joint calculations to obtain the location information of the underwater node.

[0009] The airborne base station module includes a base station pose acquisition unit, an acoustic signal transceiver unit, a time synchronization and delay correction unit, and an inter-base station communication unit. The base station pose acquisition unit acquires the real-time spatial position, velocity, and attitude information of the airborne platform and provides a geometric reference for positioning calculations. The acoustic signal transceiver unit interacts bidirectionally with the underwater node module, receiving ranging acoustic signals transmitted by the underwater node and sending response or control signals to the underwater node to complete ranging information acquisition and interactive control. The time synchronization and delay correction unit corrects the clock deviation and acoustic link hardware delay between the airborne base station and the underwater node to improve ranging time accuracy. The inter-base station communication unit enables the sharing of positioning data and status information among multiple airborne base stations to support the construction of a cooperative positioning network.

[0010] Furthermore, the underwater node module includes a node acoustic communication unit and a node status sensing unit; the node acoustic communication unit is used to actively transmit ranging acoustic signals to the airborne base station module and receive the response signals returned by the airborne base station to complete the two-way acoustic ranging and positioning information transmission; the node status sensing unit is used to acquire the motion status information of the underwater node.

[0011] Furthermore, the reliable measurement extraction module includes an acoustic signal extraction unit, a candidate path detection unit, a geometric and motion consistency evaluation unit, and a reliable path generation unit. The acoustic signal extraction unit is used to perform filtering preprocessing on the raw underwater acoustic signal received by the acoustic signal transceiver unit. The candidate path detection unit is used to extract a set of candidate paths containing multiple acoustic propagation paths from the preprocessed underwater acoustic signal through amplitude peak detection. The content of each acoustic propagation path includes arrival delay, peak amplitude, angle of arrival, and Doppler features. The geometric and motion consistency evaluation unit is used to evaluate the consistency between each acoustic propagation path and the real acoustic propagation path. The real acoustic propagation path is the acoustic propagation path between the airborne base station and the underwater node. The reliable path generation unit is used to generate the reliability weight and equivalent observation variance of each acoustic propagation path for subsequent positioning calculation.

[0012] Furthermore, the collaborative solution and positioning module includes a positioning observation construction unit, a positioning solution unit, and a result output unit; the positioning observation construction unit receives the acoustic propagation paths, their confidence weights, and equivalent observation variances corresponding to each airborne base station output by the reliable measurement extraction module; the positioning solution unit is used to perform positioning solution for the underwater node position; the result output unit is used to output the underwater node position information at the current ranging time.

[0013] Furthermore, the geometric and motion consistency evaluation unit's evaluation of the sound propagation path includes the evaluation of the geometric prediction ranging residual and the motion prediction motion consistency residual; the ranging residual is obtained through the following methods:

[0014] ;

[0015] in, Current ranging time Time Distance residuals along the propagation path of a bar sound; For the first The first airborne base station detection and extraction The sound propagation distance along a sound propagation path. The reference distance for the current ranging time represents the theoretical sound propagation distance obtained based on the predicted spatial relationship between the airborne base station and the underwater target at the current ranging time; the motion consistency residual is obtained in the following way:

[0016] ;

[0017] in, Current ranging time Time Motion consistency residuals of the sound propagation path For the first The rate of change of the observed distance along the sound propagation path represents the trend of the sound propagation distance along the path changing over time. To predict the rate of change of distance, we represent the expected trend of sound propagation distance under the assumption of continuous motion between the airborne base station and the underwater target.

[0018] The beneficial effects achieved by this invention are:

[0019] This invention introduces a reliable measurement extraction mechanism between airborne base stations and underwater nodes to evaluate the geometric and motion consistency of multiple acoustic propagation paths detected in a multipath environment, and generates corresponding reliability weights and equivalent observation variances. This transforms multipath interference from uncontrollable noise into modelable positioning observation information. Based on this, a collaborative solution positioning module integrates reliable observations from multiple airborne base stations for joint solution, effectively suppressing positioning errors caused by reflection paths, abnormal ranging, or time-varying multipaths. Compared with traditional underwater positioning methods based on single paths or equal-weighted observations, this invention significantly improves the stability, continuity, and robustness of underwater node positioning results under complex underwater acoustic propagation conditions and airborne platform maneuvering conditions. Attached Figure Description

[0020] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0021] Figure 1 This is a schematic diagram of the overall modules of the present invention.

[0022] Figure 2 This is a schematic diagram of the workflow of the reliable measurement extraction module of the present invention.

[0023] Figure 3 This is a schematic diagram of the workflow of the collaborative solution and positioning module of the present invention.

[0024] Figure 4 This is a schematic diagram comparing the positioning error of the present invention and the traditional solution over time.

[0025] Figure 5 This diagram illustrates the comparison between the solution of this invention and the traditional solution in terms of average positioning error. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Other systems, methods, and / or features of this embodiment will become apparent to those skilled in the art after reviewing the following detailed description. It is intended that all such additional systems, methods, features, and advantages are included within this specification, are included within the scope of the present invention, and are protected by the appended claims. Further features of the disclosed embodiments are described in the following detailed description, and these features will be apparent from the following detailed description.

[0027] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0028] Example 1:

[0029] like Figure 1 , Figure 2 As shown, this embodiment provides a multipath suppression and airborne base station cooperative positioning system for underwater missions. The system includes an airborne base station module, an underwater node module, a reliable measurement extraction module, and a cooperative solution positioning module. The airborne base station module is used to construct an airborne positioning reference network for underwater target positioning. The underwater node module is used to complete the transmission of positioning information with the airborne base station module. The reliable measurement extraction module is used to extract reliable positioning observations from the airborne base station module. The cooperative solution positioning module is used to combine the reliable observations from multiple airborne base stations to perform joint solution to obtain the location information of the underwater node.

[0030] The airborne base station module includes a base station pose acquisition unit, an acoustic signal transceiver unit, a time synchronization and delay correction unit, and an inter-base station communication unit. The base station pose acquisition unit acquires the real-time spatial position, velocity, and attitude information of the airborne platform and provides a geometric reference for positioning calculations. The acoustic signal transceiver unit interacts bidirectionally with the underwater node module, receiving ranging acoustic signals transmitted by the underwater node and sending response or control signals to the underwater node to complete ranging information acquisition and interactive control. The time synchronization and delay correction unit corrects the clock deviation and acoustic link hardware delay between the airborne base station and the underwater node to improve ranging time accuracy. The inter-base station communication unit enables the sharing of positioning data and status information among multiple airborne base stations to support the construction of a cooperative positioning network.

[0031] The underwater node module includes a node acoustic communication unit and a node status sensing unit; the node acoustic communication unit is used to actively transmit ranging acoustic signals to the airborne base station module and receive the response signals returned by the airborne base station to complete the two-way acoustic ranging and positioning information transmission; the node status sensing unit is used to acquire the motion status information of the underwater node.

[0032] The reliable measurement extraction module includes an acoustic signal extraction unit, a candidate path detection unit, a geometric and motion consistency evaluation unit, and a reliable path generation unit. The acoustic signal extraction unit performs filtering preprocessing on the raw underwater acoustic signal received by the acoustic signal transceiver unit. The candidate path detection unit extracts a set of candidate paths containing multiple acoustic propagation paths from the preprocessed underwater acoustic signal through amplitude peak detection. Each acoustic propagation path includes arrival delay, peak amplitude, angle of arrival, and Doppler characteristics. The geometric and motion consistency evaluation unit evaluates the consistency between each acoustic propagation path and the actual acoustic propagation path, which is the acoustic propagation path between the airborne base station and the underwater node. The reliable path generation unit generates the reliability weight and equivalent observation variance for each acoustic propagation path for subsequent positioning calculations.

[0033] Furthermore, the geometric and motion consistency evaluation unit's evaluation of the sound propagation path includes the evaluation of the geometric prediction ranging residual and the motion prediction motion consistency residual; the ranging residual is obtained through the following methods:

[0034] ;

[0035] in, Current ranging time Time Distance residuals along the propagation path of a bar sound; For the first The first airborne base station detection and extraction The sound propagation distance along a sound propagation path. The reference distance for the current ranging time satisfies:

[0036] ;

[0037] in, The equivalent speed of sound in the underwater environment at the current ranging time is obtained through prior measurement of the underwater environment; For the first The arrival delay of the sound propagation path. For the hardware time delay of the base station acoustic link;

[0038] ;

[0039] in, The underwater node location information is obtained by the collaborative calculation and positioning module based on the previous ranging time of the current ranging time. For the current ranging time, the [number]th ... The location of each airborne base station;

[0040] Furthermore, the motion consistency residual is obtained in the following way:

[0041] ;

[0042] in, Current ranging time Time Motion consistency residuals of the sound propagation path For the first The rate of change of the observed distance along the propagation path of the bar sound. To predict the rate of change of distance, the following must be satisfied:

[0043] ;

[0044] in, The time interval between two adjacent ranging time points. The previous ranging time of the current ranging time The distance the sound travels along the propagation path;

[0045] ;

[0046] in, This provides the latest velocity information acquired by the underwater node at the current ranging time. For the first The latest speed information obtained by each airborne base station at the current ranging time;

[0047] Furthermore, since the sound propagation paths at different ranging times do not have a natural correspondence, the sound propagation paths at adjacent ranging times are associated and corresponded in the following way:

[0048] ;

[0049] in, The number obtained for the current ranging time The propagation path of the bar sound and the first measurement time obtained from the previous ranging time The association cost between two sound propagation paths is used to measure the degree of continuity and consistency of the temporal and spatial characteristics of the two sound propagation paths. For the first The arrival delay of the sound propagation path. For the first The arrival delay of the sound propagation path. For the first The angle of arrival of the propagation path of a sound wave. For the first The angle of arrival of the sound propagation path. For the first Doppler characteristics of the propagation path of a sound bar For the first Doppler characteristics of the propagation path of a sound bar This is an angle normalization function used to limit the angle difference within a preset angle range; , and The weighting coefficients for arrival time delay difference, arrival angle difference, and Doppler difference are respectively set through pre-experimentation to satisfy... ;

[0050] Specifically, the arrival delay represents the propagation time difference of the acoustic signal corresponding to the acoustic propagation path from the transmitting end to the receiving end of the airborne base station, which is used to characterize the propagation distance characteristics of the acoustic signal in the underwater acoustic propagation environment; the arrival angle represents the direction angle of the acoustic signal corresponding to the acoustic propagation path incident on the airborne base station array, and its reference direction is zero-degree with the preset coordinate reference direction of the airborne base station array, which is used to characterize the spatial incident direction characteristics of the acoustic propagation path.

[0051] For the current ranging time The The sound propagation path is selected based on the previous ranging time. Related costs of China The path with the smallest sound propagation cost is selected as the candidate corresponding path. When the minimum association cost is less than the preset association threshold, the two sound propagation paths are determined to correspond to the same physical propagation path. Otherwise, the current sound propagation path is determined to be a newly emerging path and is not included in the cross-time continuity calculation.

[0052] Furthermore, the confidence weights and equivalent observation variances generated by the trusted path generation unit are calculated as follows:

[0053] ;

[0054] ;

[0055] in, For the first The credibility weight of a sound propagation path is used to characterize the credibility of the sound propagation path as a positioning observation at the current ranging time. The ranging residual scale parameter is used to describe the statistical distribution range of ranging errors in candidate sound propagation paths, and its value is obtained through offline system calibration. The motion consistency residual scale parameter is used to describe the allowable range of variation of the sound propagation path under the constraint of time continuity. Its value is preset based on the maximum motion speed of the underwater node, the ranging time interval, and the platform maneuvering state. For the first The equivalent observation variance of the sound propagation path is used to perform weighted modeling of the ranging observations of the sound propagation path in the subsequent positioning solution process. The smaller the equivalent observation variance, the greater the influence weight of the path in the positioning solution. The baseline ranging variance is used to characterize the basic error level of ranging observations under ideal single-path propagation conditions, and its value can be obtained by the system pre-calibration. A lower bound constant to prevent numerical divergence;

[0056] This scheme uses the aforementioned reliable measurement extraction method to transform the multiple acoustic propagation paths detected by the airborne base station in a multipath environment from equivalent measurements into positioning observations with reliability weights. This allows acoustic propagation paths that conform to geometric and motion consistency constraints to play a dominant role in subsequent positioning calculations, while acoustic propagation paths that do not conform to consistency constraints are automatically weakened. This effectively reduces the impact of multipath interference on positioning results and improves the stability and robustness of underwater positioning.

[0057] Example 2:

[0058] This embodiment should be understood to include at least all the features of any of the foregoing embodiments, and to further improve upon them;

[0059] This embodiment provides a multipath suppression and airborne base station cooperative positioning system for underwater missions. The system includes an airborne base station module, an underwater node module, a reliable measurement extraction module, and a cooperative solution positioning module. The airborne base station module is used to construct an airborne positioning reference network for underwater target positioning. The underwater node module is used to complete the transmission of positioning information with the airborne base station module. The reliable measurement extraction module is used to extract reliable positioning observations from the airborne base station module. The cooperative solution positioning module is used to combine the reliable observations from multiple airborne base stations to perform joint solution to obtain the location information of the underwater node.

[0060] Furthermore, such as Figure 3 As shown, the collaborative solution and positioning module includes a positioning observation construction unit, a positioning solution unit, and a result output unit; the positioning observation construction unit receives the acoustic propagation paths, their confidence weights, and equivalent observation variances corresponding to each airborne base station output by the reliable measurement extraction module; the positioning solution unit is used to perform positioning solution for the underwater node position; the result output unit is used to output the underwater node position information at the current ranging time;

[0061] Furthermore, the positioning calculation unit extracts the top-ranked units with the highest credibility weights for each airborne base station. Sound propagation path, Range of values The objective function for determining the underwater node positions is solved by addressing the following objective function:

[0062] ;

[0063] in, This is the result of calculating the underwater node position at the current ranging time; For the number of airborne base stations, This is a robust loss function used to suppress the impact of outlier observations on the localization results. The loss function takes the form of the Huber loss function.

[0064] This scheme directly incorporates the multipath confidence weights and equivalent observation variances output by the confidence measurement extraction module into the positioning solution process during underwater node calculation. Through joint optimization of the robust loss function and motion prior constraints, it achieves weighted robust collaborative positioning under multi-airborne base station conditions. Compared with traditional positioning methods based on single paths or equal-weighted observations, this invention avoids the positioning jump problem caused by erroneous paths dominating the solution in multipath environments, and significantly improves the stability and continuity of underwater node positioning results under complex underwater acoustic propagation conditions.

[0065] Example 3:

[0066] This embodiment should be understood to include at least all the features of any of the foregoing embodiments, and to further improve upon them;

[0067] Based on Embodiments 1 and 2, this embodiment further refines the engineering configuration, acoustic parameter selection, and multi-base station collaborative operation strategy of the multipath suppression and airborne base station cooperative positioning system for underwater missions under dynamic airborne platform participation conditions, so as to improve the real-time positioning accuracy, continuity, and anti-interference capability of the system in complex multipath propagation environments and under the conditions of airborne base station maneuvering.

[0068] The airborne base station module described in this embodiment consists of a cooperative positioning network composed of three to six airborne platforms. Each airborne platform can carry acoustic communication and positioning payloads and form a deformable base station array with a spacing of 500 meters to 2,000 meters. The attitude acquisition unit of a single airborne base station integrates an inertial navigation and satellite positioning combination module, so that the base station position measurement accuracy is better than one meter and the attitude angle measurement accuracy is better than 0.1 degrees. The acoustic signal transceiver unit adopts a broadband pulse acoustic system, with the preferred operating frequency band being 6 kHz to 14 kHz, the preferred duration of a single ranging pulse being 50 milliseconds to 100 milliseconds, and the transmit power being adjustable from 20 watts to 60 watts. The sampling rate of the receiving end is not less than 48 kHz to ensure multipath pulse resolution capability. The time synchronization and delay correction unit uses a bidirectional timestamp exchange method to compensate for the clock deviation between the airborne base station and the underwater node in real time, so that the single ranging time calibration error is controlled in the sub-millisecond level, thereby improving the ranging stability under dynamic airborne platform conditions.

[0069] In this embodiment, the underwater node module adopts an active ranging interaction method. The node acoustic communication unit periodically transmits ranging request signals to multiple airborne base stations and receives response signals returned by the base stations to complete the two-way ranging interaction. The node state perception unit synchronously outputs the underwater node's speed, heading, and depth information, and adds the motion state parameters to the ranging data packet and uploads it to the collaborative calculation and positioning module to provide prior input for multi-moment motion consistency assessment.

[0070] In this embodiment, the reliable measurement extraction module adopts a multi-dimensional feature joint evaluation strategy. The acoustic signal extraction unit performs adaptive bandpass filtering and noise suppression processing on the raw underwater acoustic signals received by each airborne base station, thereby improving the signal-to-noise ratio by an average of four to seven decibels. The candidate path detection unit can stably detect no less than three multipath propagation paths and extract arrival delay, amplitude, angle of arrival, and Doppler feature parameters. The geometric and motion consistency evaluation unit combines the real-time pose of the airborne base station and the motion information of underwater nodes to perform cross-time correlation and consistency judgment on each candidate path, so that the acoustic propagation path that conforms to the constraints of the real propagation path still maintains high reliability output under complex sea conditions, while abnormal reflection paths and short-term abrupt change paths are automatically assigned low reliability weights.

[0071] In this embodiment, the collaborative solution and positioning module is deployed on the main control processing terminal of the airborne platform or the shore-based fusion center. The positioning observation construction unit performs time alignment and weight normalization processing on the reliable path observations output by multiple airborne base stations. The positioning solution unit adopts a weighted robust collaborative solution strategy to fuse the observation information of multiple base stations and combines the underwater node motion prior to jointly optimize the current position, so that the positioning iteration is completed within one hundred milliseconds to meet the real-time tracking requirements. The result output unit continuously outputs the three-dimensional positioning results of the underwater node and generates trajectory smoothing constraints to be input into the next ranging cycle, thereby forming a closed-loop stable positioning link.

[0072] like Figure 4 , Figure 5 As shown, to verify the effect of the proposed multipath suppression and airborne base station cooperative positioning system for underwater missions on improving the positioning accuracy and continuity of underwater nodes under complex multipath propagation and airborne platform maneuvering conditions, the following experimental verification scheme is provided, and the experimental process and experimental data results are explained.

[0073] In this experiment, the multipath suppression and airborne base station cooperative positioning system described in Example 3 was deployed in a controlled test water area. Three airborne base stations constructed a cooperative positioning network within a three-kilometer radius according to a dynamic triangular array. Underwater nodes performed cruise measurement tasks within the array coverage area. The test water area was designed with enhanced surface and seabed reflection conditions to form a significant multipath propagation environment. At the same time, an external high-precision reference positioning device was used to obtain the real trajectory of the underwater nodes as a reference. The system ran continuously for thirty minutes and recorded the ranging data, candidate path information and positioning calculation results of each base station at a sampling period of one second.

[0074] Three processing schemes were set up in the experiment while maintaining consistent hardware and sampling conditions. Traditional scheme 1 used the earliest arrival path discrimination method but did not enable multi-path reliable extraction and collaborative solution. Traditional scheme 2 introduced single-base station ranging correction based on traditional scheme 1, but did not enable multi-base station collaborative optimization and motion consistency constraints. The scheme of this invention simultaneously enables multi-path reliable measurement extraction, multi-airborne base station collaborative solution, and joint motion consistency constraints. During operation, the system recorded the positioning error time series in real time and used a sliding time window to statistically analyze the average positioning error and the continuous effective positioning success rate.

[0075] Experimental data shows that traditional scheme 1 exhibits significant fluctuations in positioning error under strong multipath reflection conditions, with an average positioning error of approximately six to eight meters and frequent trajectory jumps. Traditional scheme 2, after introducing single-base station correction, reduces the average positioning error to approximately four meters, but still suffers from intermittent and discontinuous positioning under maneuvering conditions on the airborne platform. In contrast, the scheme of this invention, after fully executing multipath reliable extraction and airborne base station collaborative calculation, further reduces the average positioning error to two to three meters, achieving a continuous positioning success rate of over 98%, and maintaining a smooth and stable positioning trajectory. Therefore, the multipath suppression and airborne base station collaborative positioning mechanism proposed in Embodiment 3 of this invention can significantly improve positioning accuracy, continuity, and anti-interference capabilities under complex underwater acoustic propagation and base station maneuvering environments, fully verifying the beneficial effects of this invention.

[0076] Furthermore, in this embodiment, the airborne base station can be replaced with a fixed buoy base station or a surface unmanned platform base station to adapt to different mission scenarios. The acoustic ranging system can be replaced with a linear frequency modulation signal or a spread spectrum pulse signal to adapt to underwater acoustic channels with different bandwidths. The reliable measurement and evaluation strategy can also be replaced with a path reliability discrimination method based on a learning model to further improve the adaptive capability in complex and unknown environments.

[0077] This embodiment, through the joint design of dynamic networking of multiple airborne base stations, multi-path reliable measurement extraction, and robust collaborative solution, enables the system to achieve high-precision, high-continuity, and high-reliability underwater node positioning under complex underwater acoustic multipath environments and airborne platform maneuvering conditions, and has good engineering promotion value and application prospects.

[0078] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of protection of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included within the scope of protection of the present invention. Furthermore, the elements therein can be updated as technology develops.

Claims

1. A multipath suppression and airborne base station cooperative positioning system for underwater missions, characterized in that, The system includes an airborne base station module, an underwater node module, a reliable measurement extraction module, and a collaborative solution and positioning module. The airborne base station module is used to construct an airborne positioning reference network for underwater target positioning. The underwater node module is used to complete the transmission of positioning information with the airborne base station module. The reliable measurement extraction module is used to extract reliable positioning observations from the airborne base station module. The collaborative solution and positioning module is used to combine the reliable observations from multiple airborne base stations to perform joint solution and obtain the position information of the underwater node. The airborne base station module includes a base station pose acquisition unit, an acoustic signal transceiver unit, a time synchronization and delay correction unit, and an inter-base station communication unit. The base station pose acquisition unit acquires the real-time spatial position, velocity, and attitude information of the airborne platform and provides a geometric reference for positioning calculations. The acoustic signal transceiver unit interacts bidirectionally with the underwater node module, receiving ranging acoustic signals transmitted by the underwater node and sending response or control signals to the underwater node to complete ranging information acquisition and interactive control. The time synchronization and delay correction unit corrects the clock deviation and acoustic link hardware delay between the airborne base station and the underwater node to improve ranging time accuracy. The inter-base station communication unit enables the sharing of positioning data and status information among multiple airborne base stations to support the construction of a cooperative positioning network.

2. The multipath suppression and airborne base station cooperative positioning system for underwater missions according to claim 1, characterized in that, The underwater node module includes a node acoustic communication unit and a node status sensing unit; the node acoustic communication unit is used to actively transmit ranging acoustic signals to the airborne base station module and receive the response signals returned by the airborne base station to complete the two-way acoustic ranging and positioning information transmission; the node status sensing unit is used to acquire the motion status information of the underwater node.

3. The multipath suppression and airborne base station cooperative positioning system for underwater missions according to claim 1, characterized in that, The reliable measurement extraction module includes an acoustic signal extraction unit, a candidate path detection unit, a geometric and motion consistency evaluation unit, and a reliable path generation unit. The acoustic signal extraction unit performs filtering preprocessing on the raw underwater acoustic signal received by the acoustic signal transceiver unit. The candidate path detection unit extracts a set of candidate paths containing multiple acoustic propagation paths from the preprocessed underwater acoustic signal through amplitude peak detection. Each acoustic propagation path includes arrival delay, peak amplitude, angle of arrival, and Doppler features. The geometric and motion consistency evaluation unit evaluates the consistency between each acoustic propagation path and the actual acoustic propagation path. The actual acoustic propagation path is the acoustic propagation path between the airborne base station and the underwater node. The reliable path generation unit generates the reliability weight and equivalent observation variance of each acoustic propagation path for subsequent positioning calculations.

4. The multipath suppression and airborne base station cooperative positioning system for underwater missions according to claim 1, characterized in that, The collaborative solution and positioning module includes a positioning observation construction unit, a positioning solution unit, and a result output unit. The positioning observation construction unit receives the acoustic propagation paths, their confidence weights, and equivalent observation variances corresponding to each airborne base station output by the reliable measurement extraction module. The positioning solution unit is used to perform positioning solution for the underwater node positions. The result output unit is used to output the position information of the underwater node at the current ranging time.

5. A multipath suppression and airborne base station cooperative positioning system for underwater missions according to claim 3, characterized in that, The geometric and motion consistency evaluation unit's evaluation of the sound propagation path includes the evaluation of the geometric prediction ranging residual and the motion prediction motion consistency residual; the ranging residual is obtained through the following methods: ； in, Current ranging time Time Distance residuals along the propagation path of a bar sound; For the first The first airborne base station detection and extraction The sound propagation distance along a sound propagation path. The reference distance for the current ranging time represents the theoretical sound propagation distance obtained based on the predicted spatial relationship between the airborne base station and the underwater target at the current ranging time; the motion consistency residual is obtained in the following way: ； in, Current ranging time Time Motion consistency residuals of the sound propagation path For the first The rate of change of the observed distance along the sound propagation path represents the trend of the sound propagation distance along the path changing over time. To predict the rate of change of distance, we represent the expected trend of sound propagation distance under the assumption of continuous motion between the airborne base station and the underwater target.

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