Underwater wide area navigation positioning construction method and system

Abstract

The invention relates to the technical field of navigation and positioning, in particular to an underwater wide-area navigation and positioning construction method and system.The method comprises the steps that the electric field intensity of very-low-frequency radio in the long-distance propagation process is calculated according to the transmitting frequency of a very-low-frequency transmitting station, and the cross-domain navigation coverage range is calculated according to the underwater entry depth of the electric field intensity; constructing a very-low-frequency radio cross-domain navigation network in a land-based layout mode by taking a cross-domain navigation coverage range and GDOP distribution as thresholds; constructing a low-frequency remote acoustic navigation network by adopting a seabed subsurface buoy layout mode on the basis of the water depth and terrain required by acoustic propagation; and performing underwater wide-area navigation positioning according to the very-low-frequency radio cross-domain navigation network, the low-frequency remote acoustic navigation network and inertial navigation. According to the method, a multi-source fusion navigation mode of low-frequency radio cross-domain navigation, low-frequency remote acoustic navigation and inertial navigation is realized through a factor graph fusion algorithm, and navigation and positioning in an underwater wide-area range are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of navigation positioning, in particular to a method and system for constructing underwater wide-area navigation positioning. BACKGROUND

[0002] The underwater unmanned platform and submersible have the characteristics of flexible use, high comprehensive combat effectiveness, applicability to dangerous environment, low personnel casualty rate and low life cycle cost. Since the operation range of the underwater unmanned platform and submersible often covers a wide underwater space, from shallow sea to deep sea, from near shore to open sea, the complexity and vastness of the activity area put high requirements on underwater navigation, especially the ability to cover a wide area to ensure accurate positioning and navigation at any operation location and to ensure the smooth completion of the task.

[0003] The inherent characteristics of the marine environment and water medium bring great challenges to underwater navigation. The radio navigation technology widely used on the water surface will be severely attenuated when the electromagnetic wave propagates in water, with a very short propagation distance, which is difficult to meet the demand of underwater wide-area navigation. Optical navigation will be affected by the scattering and absorption of water, resulting in limited signal transmission distance, and cannot work normally in turbid seawater environment. This makes the underwater navigation positioning means relatively scarce, which is one of the key bottlenecks restricting the development and application of underwater unmanned platforms and submersibles.

[0004] As an information carrier that can stably propagate over a long distance in the marine medium, sound waves are particularly suitable for providing wide-area positioning services for underwater unmanned platforms and submersibles and other carriers. It has specific requirements for water depth and terrain, and needs to be used in areas that meet certain sea depth conditions, and the terrain of the operation area needs to be relatively flat. If used in shallow sea areas or areas with complex terrain and many reefs, low-frequency sound waves are easily disturbed by seabed reflection and scattering, resulting in a decrease in positioning accuracy, or even unable to work normally, which limits its application range to some extent. SUMMARY

[0005] The present application aims to at least solve one of the technical problems in the related art. To this end, the present application provides a method and system for constructing underwater wide-area navigation positioning. When the underwater unmanned platform and submersible are in the shallow water and complex terrain area near the coast, a combined navigation mode of very low frequency radio cross-domain navigation and inertial navigation is adopted. In the deep sea area, a combined navigation mode of low-frequency long-range acoustic navigation and inertial navigation is adopted. In the transition area between the near shore and the deep sea, a multi-source fusion navigation mode of low-frequency radio cross-domain navigation, low-frequency long-range acoustic navigation and inertial navigation is adopted, and the fusion of multi-source information is realized through a factor graph fusion algorithm. The navigation and positioning in the underwater wide-area range are realized.

[0006] The present application provides a method for constructing underwater wide-area navigation positioning, comprising: S1: calculating the electric field intensity of VLF radio in long distance propagation according to the transmitting frequency of VLF transmitting station, and calculating the coverage of cross-domain navigation according to the water depth of electric field intensity; S2: constructing VLF radio cross-domain navigation network by land-based layout method with the coverage of cross-domain navigation and GDOP distribution as threshold; S3: constructing low frequency long-range acoustic navigation network by submarine buoy layout method with the water depth and terrain required for sound propagation as reference; S4: underwater wide-area navigation and positioning according to VLF radio cross-domain navigation network, low frequency long-range acoustic navigation network and inertial navigation.

[0007] Further, in S1, the calculation expression of the electric field intensity of VLF radio in long distance propagation is: wherein, is the vertical electric field intensity, is the space wave impedance, is the transmitting power, is the coverage, is the attenuation coefficient.

[0008] Further, S2 includes: S21: laying VLF radio stations by land-based layout method; S22: obtaining the positioning error of VLF radio stations by hyperbolic positioning method; S23: calculating the GDOP between VLF radio stations; S24: correcting the positioning error of VLF radio stations according to the GDOP between VLF radio stations, and completing the construction of VLF radio cross-domain navigation network.

[0009] Further, the calculation expression of GDOP is: wherein, is the geometric dilution of precision, is the included angle of two pairs of ground navigation stations relative to the common navigation station, is half of the included angle of the carrier relative to the baseline of the first pair of ground stations, is half of the included angle of the carrier relative to the baseline of the second pair of ground stations, is and is the correlation coefficient.

[0010] Further, in S3, the submarine buoy is laid at the receiving point and the sending point of reliable sound path by Gaussian beam tracking method, and low frequency long-range acoustic navigation is realized by using reliable sound path long-range acoustic channel. The reliable sound path is a path with a water depth greater than 3600m and a flat terrain.

[0011] Further, the S3 step comprises: S31: calculating the complex sound pressure amplitude of each point in space by the Gaussian beam equation; S32: determining the beam weight according to the uniform medium point source; S33: summing the complex sound pressure amplitude of each point in space according to the beam weight to obtain a composite sound pressure; S34: optimizing the reliable sound path according to the composite sound pressure.

[0012] Further, in the S4 step, When the underwater unmanned platform and the submersible are in the shallow water area near the coast and the complex terrain area, a combined navigation mode of very low frequency radio cross-domain navigation and inertial navigation is adopted; In the deep sea area, a combined navigation mode of low frequency long-range acoustic navigation and inertial navigation is adopted; In the connecting area of the near shore and the deep sea, a multi-source fusion navigation mode of low frequency radio cross-domain navigation, low frequency long-range acoustic navigation and inertial navigation is adopted, and the fusion of multi-source information is realized through a factor graph fusion algorithm; The deep sea area is a sea area with a distance greater than 5000km and a water depth greater than 3600m; The shallow water area near the coast is a sea area with a distance less than 5000km and a water depth less than 3600m.

[0013] Further, the factor graph fusion algorithm comprises: Defining a model factor of a multi-navigation network; According to the observation value at the current time, a joint probability distribution function is constructed, and a maximum a posteriori estimation model is constructed according to the joint probability distribution function; Under Gaussian noise, an unconstrained nonlinear least square algorithm is adopted to solve the maximum a posteriori estimation model according to the model factor to obtain an optimal solution.

[0014] Further, the model factor comprises an inertial navigation factor, a very low frequency radio cross-domain navigation positioning model factor and a low frequency long-range acoustic navigation positioning model factor, and the inertial navigation factor comprises an IMU factor and an IMU bias factor.

[0015] The application also provides an underwater wide-area navigation positioning construction system for executing the above-mentioned underwater wide-area navigation positioning construction method, comprising: A calculation module, which calculates the electric field intensity of the very low frequency radio in the long-distance transmission process according to the transmission frequency of the very low frequency transmitting station, and calculates the cross-domain navigation coverage range according to the water depth of the electric field intensity; A first construction module, which adopts a land-based arrangement mode to construct a very low frequency radio cross-domain navigation network, with cross-domain navigation coverage range and GDOP distribution as thresholds; A second construction module, which adopts a submarine buoy arrangement mode to construct a low frequency long-range acoustic navigation network, with water depth and terrain required for sound propagation as references; A comprehensive navigation and positioning module, which performs wide-area navigation and positioning according to the very low frequency radio cross-domain navigation network, the low frequency long-range acoustic navigation network and inertial navigation.

[0016] The above one or more technical solutions in the embodiments of the present application have at least one of the following technical effects: The present application breaks through the scene limitation of single navigation technology by the combination of low frequency long-range acoustic navigation and very low frequency radio cross-domain navigation. The low frequency long-range acoustic navigation takes the submarine buoy as the core to meet the wide-area navigation demand in deep sea, and the very low frequency radio cross-domain navigation adopts the land-based construction to solve the navigation problem in the near-shore shallow water area and the complex terrain area, and the two achieve the wide-area or even global underwater navigation and positioning coverage from the near-shore to the deep sea and from the simple to the complex terrain, fully play the advantages of the two navigation technologies and make up for the respective shortcomings. The sound wave is used as the information carrier for the stable long-distance propagation in the ocean to ensure the stability of the deep sea navigation, and the very low frequency radio cross-domain navigation overcomes the application limitation of low frequency acoustic in the near-shore shallow water and complex terrain, and improves the overall reliability and applicability of the underwater navigation and positioning through the technical cooperation.

[0017] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0019] Figure 1 is a flowchart of a method for constructing underwater wide-area navigation and positioning provided by the present application.

[0020] Figure 2 is a schematic diagram of the cross-domain navigation coverage range of the very low frequency radio cross-domain navigation network of the embodiment of the present application.

[0021] Figure 3 is a schematic diagram of the relationship between GDOP and positioning accuracy of the embodiment of the present application.

[0022] Figure 4 is a schematic diagram of a low-frequency remote acoustic propagation process of an embodiment of the present application.

[0023] Figure 5 is a schematic diagram of a terrain-considered acoustic propagation process of an embodiment of the present application.

[0024] Figure 6 is a schematic diagram of construction of an underwater wide-area navigation and positioning method of the present application.

[0025] Figure 7 is a schematic diagram of navigation error results of an embodiment of the present application.

[0026] Figure 8 is a schematic diagram of the structure of a system for constructing an underwater wide-area navigation and positioning method provided by the present application.

[0027] Reference signs: 101, a calculation module; 102, a first construction module; 103, a second construction module; 104, a comprehensive navigation and positioning module. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be clearly and completely described below. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. The following embodiments are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0029] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0030] The present application will be described below in conjunction with Figures 1 to 8 a method and system for constructing an underwater wide-area navigation and positioning method.

[0031] As shown in Figure 1 , a method for constructing an underwater wide-area navigation and positioning method comprises: S1: calculating the electric field intensity of VLF radio in long distance propagation according to the transmitting frequency of VLF transmitting station, and calculating the coverage range of trans-regional navigation according to the electric field intensity and the water entry depth; The transmitting frequency of VLF transmitting station is acquired, and the electric field intensity of VLF radio in long distance propagation is calculated according to the transmitting frequency; the calculation expression of the electric field intensity of VLF radio in long distance propagation is: wherein, is the vertical electric field intensity, and the unit is , is the space wave impedance, and the unit is (ohm), is the transmitting power, and the unit is kW, is the coverage range, and the unit is km, is the attenuation coefficient.

[0032] In some specific embodiments of the present application, , , is the VLF radio frequency.

[0033] The amplitude attenuation multiple of electromagnetic wave propagating downward from air to seawater is: wherein, is the amplitude attenuation multiple, is the underwater attenuation rate of electromagnetic wave, is the water entry depth; The calculation expression of the underwater attenuation rate of electromagnetic wave is: wherein, is the water medium conductivity, and the seawater medium is generally taken as 4 s / m, is the permeability coefficient of seawater, and generally taken as .

[0034] The VLF radio navigation adopts the magnetic antenna with high magnetic permeability and multiple turns of coil to receive VLF radio signal underwater, and the calculation expression of the initial sensitivity of the magnetic antenna is: wherein, is the initial sensitivity of the magnetic antenna, is the magnetic permeability, is the number of turns of coil, is the cross-sectional area of magnetic core, is the VLF frequency.

[0035] According to the water entry depth ​Computing amplitude attenuation factor , according to the value of the water entry depth , the vertical electric field intensity at the water entry depth The propagation distance of the vertical electric field intensity at the water entry depth is greater than the magnetic antenna receiver sensitivity, and the VLF radio cross-domain navigation network cross-domain navigation coverage.

[0036] In some embodiments of the application, the VLF transmitting station transmits at a power of 1 MW, the magnetic antenna receiver sensitivity is 0.1 nT as the threshold value, and the cross-domain navigation is calculated at a water entry depth of 15 m, then the VLF radio cross-domain navigation network cross-domain navigation coverage is 5884 km, as shown in Figure 2 .

[0037] S2: using the cross-domain navigation coverage and GDOP distribution as thresholds, a land-based arrangement is used to construct a VLF radio cross-domain navigation network; S21: using a land-based arrangement to arrange the VLF radio station; Considering the cross-domain navigation coverage of VLF radio and the GDOP distribution, the VLF radio navigation adopts a land-based arrangement to complete the construction of the VLF radio cross-domain navigation network, and can realize navigation and positioning in a certain water depth within a range of 5000 kilometers, solving the problem of wide-area underwater navigation and positioning in shallow water areas and complex terrain areas within the near-shore range.

[0038] S22: using hyperbolic positioning method to obtain the positioning error of the VLF radio station; The VLF radio navigation network usually uses hyperbolic positioning principle, the receiving end receives signals emitted by different transmitting points, and the time difference of the transmitting signals of two transmitting points reaching the receiving point. The positioning accuracy of VLF radio cross-domain navigation is related to its GDOP distribution, and the GDOP depends on the distribution of the shore station and the geometric position relationship between the receiving point and the shore station. Under the condition that the device measurement performance is the same, the positioning error of the receiving point is proportional to the GDOP. The relationship between the positioning error and the GDOP is as follows: wherein, is the positioning error, is the geometric dilution of precision, is the ranging error.

[0039] S23: calculating the GDOP between VLF radio stations; The GDOP of a single station chain configured by two pairs of ground navigation stations (one station public) formed by three stations is calculated as follows: wherein, is the geometric dilution of precision, is the angle between the two pairs of ground navigation stations and the common navigation station, is half of the angle of the carrier relative to the baseline of the first pair of ground stations, is half of the angle of the carrier relative to the baseline of the second pair of ground stations, for and The correlation coefficient of and Are they independent of each other.

[0040] It varies with the quadrant. In quadrants I and III: , in quadrants II and IV: .

[0041] The geometric dilution of precision (GDOP) varies significantly at different receiver locations. A high GDOP on the transmitter baseline delay line makes positioning impossible. User receivers can choose areas with a GDOP of less than 5 to 10 based on different positioning requirements. For higher positioning accuracy, areas with a GDOP of less than 3 are preferred.

[0042] The following three transmitters are deployed within 5000km of the VLF transmitter coverage area. The geometric dilution of precision (GDOP) of the receiver positioning is less than 5, which can achieve high-precision positioning, such as Figure 3 As shown, Figure 3 In the figure, the horizontal coordinate is north latitude and the vertical coordinate is east longitude.

[0043] S24: Correct the positioning error of the VLF radio station according to the GDOP between the VLF radio stations and complete the construction of the VLF radio cross-domain navigation network.

[0044] S3: Based on the water depth and terrain required for sound propagation, a low-frequency long-range acoustic navigation network is constructed using submarine buoys. When underwater acoustic navigation and positioning equipment operates at a lower frequency band, it can achieve long-distance transmission and wide-area coverage. The inhomogeneous acoustic properties of the ocean environment cause underwater sound to bend and reverse during long-distance propagation, causing the acoustic signal to arrive at the receiving point along different paths within the underwater acoustic channel. At the acoustic navigation receiver, the signal is primarily reflected as multiple signals, both the direct sound and the reflected sound from the sea surface and seabed, which gradually decay over time. In underwater acoustic navigation and positioning, it is generally desirable to use the direct sound signal for navigation and resolution. Therefore, the design of the low-frequency long-range acoustic navigation network must consider the water depth and terrain required for sound propagation, as well as propagation losses, to ensure the required accuracy. Furthermore, given that underwater vehicles typically operate at depths of 1-1000m, a Gaussian beam tracking method is employed, with submarine buoys positioned at the receiving and transmitting points along a reliable acoustic path. Low-frequency long-range acoustic navigation is achieved using a long-range acoustic channel along this reliable acoustic path; this reliable acoustic path is defined as a water depth greater than 3600m and flat terrain.

[0045] S31: Calculate the complex sound pressure amplitude at each point in space beam by beam using the Gaussian beam equation; The Gaussian beam tracking method is used to calculate the water depth and terrain required for sound propagation. The sound beam equation is: in, is the spatial position of the Gaussian beam The complex sound pressure amplitude at , is the propagation distance along the beam axis, is the transverse coordinate perpendicular to the beam axis, is the initial amplitude, For the The sound velocity distribution, is the geometric expansion characteristic coefficient of the beam, is the complex curvature parameter that controls the beam width, is the angular frequency of the sound wave, For the propagation time, is the complex curvature parameter that controls the degree of beam phase bending, It is a plural unit.

[0046] and The initial conditions are: in, is the initial beam width, is the initial value of the complex curvature parameter that controls the degree of beam phase bending, is the initial value of the complex curvature parameter that controls the beam width.

[0047] S32: determining the beam weight according to the uniform medium point source; The weighting of each acoustic beam is determined according to the standard point source problem in the uniform medium, and for the point source, the corresponding weighting of the acoustic beam is: wherein, is the weight of the beam in the direction, is the radian corresponding to the included angle between the acoustic beams, is the propagation speed of the acoustic beam in water.

[0048] and are dimensionless, the unit of is m / s, the unit of is m 2 / s.

[0049] S33: summing the complex sound pressure amplitudes of each point in space according to the beam weight to obtain a composite sound pressure; S34: optimizing the reliable sound path according to the composite sound pressure.

[0050] It is assumed that the water depth of the sea area is 3800m, and the seabed sediment is silty sand type. The sound speed profile adopted is the Munk standard sound speed profile. The transmission depth is 3000m underwater, and the receiving depth is 0-3800m. The low-frequency long-range acoustic propagation process is as shown in Figure 4 , and the sound propagation process considering the terrain is as shown in Figure 5 . Due to the terrain mutation of the seamount at 150km, the low-frequency long-range acoustic propagation process produces drastic changes. Low-frequency long-range acoustic direct sound propagation needs to be above 3600m water depth and the terrain is flat without high mountains. Therefore, the low-frequency long-range acoustic navigation network construction can only be used for underwater wide-area navigation and positioning in deep sea areas, providing navigation and positioning services for underwater unmanned platforms and submersibles.

[0051] S4: wide-area navigation and positioning according to the very low frequency radio cross-domain navigation network, the low-frequency long-range acoustic navigation network, and the inertial navigation.

[0052] As shown in Figure 6 , when the underwater unmanned platform and the submersible are in the near-shore shallow water area and the complex terrain area, the combined navigation mode of the very low frequency radio cross-domain navigation and the inertial navigation is adopted; In the deep sea area, the combined navigation mode of the low-frequency long-range acoustic navigation and the inertial navigation is adopted; In the transition area between the near-shore and the deep sea, the multi-source fusion navigation mode of the low-frequency radio cross-domain navigation, the low-frequency long-range acoustic navigation, and the inertial navigation is adopted, and the fusion of multi-source information is realized through the factor graph fusion algorithm; The deep sea region is a sea area with a distance greater than 5000 km and a water depth greater than 3600 m; The near-shore shallow water region is a sea area with a distance less than 5000 km and a water depth less than 3600 m.

[0053] The factor graph fusion algorithm comprises: Defining a model factor of a multi-navigation network; The model factor comprises an inertial navigation factor, a very low frequency radio cross-domain navigation positioning model factor and a low frequency long-range acoustic navigation positioning model factor, and the inertial navigation factor comprises an IMU factor and an IMU bias factor; The calculation expression of the IMU factor is: Wherein, is the IMU factor, is a state variable at the time t, is a state variable at the time t, is an IMU bias parameter at the time t, is a coverage range, is a state variable at the time t, is an observation at the time t, the prediction is IMU observation data.

[0054] The calculation expression of the IMU bias factor is: Wherein, is the IMU bias factor, is a predicted IMU bias, is an IMU bias parameter at the time t.

[0055] The calculation expression of the very low frequency radio cross-domain navigation positioning model factor is: Wherein, is the very low frequency radio cross-domain navigation positioning model factor, is radio observation data at the time t, is predicted radio observation data.

[0056] The calculation expression of the low frequency long-range acoustic navigation positioning model factor is: Wherein, is the low-frequency long-range acoustic navigation positioning model factor, for Acoustic observation data at the moment, The acoustic observation data for prediction.

[0057] According to the observation value at the current moment, a joint probability distribution function is constructed, and a maximum a posteriori estimation model is constructed based on the joint probability distribution function; Given an observation, the process of solving the maximum a posteriori estimation of the variables using nonlinear optimization methods. Assume that the joint probability distribution function is ,in, are all observations received up to the current moment. ,in, for The maximum posterior of the observation data at time t is: in, for The maximum a posteriori of the parameters to be estimated at time, In order for the function to obtain the maximum value of the independent variable, is the parameter to be estimated.

[0058] Under Gaussian noise, an unconstrained nonlinear least squares algorithm is used to solve the maximum a posteriori estimation model according to the model factors to obtain the optimal solution; For Gaussian noise distribution, the maximum a posteriori estimation problem becomes the problem of minimizing the following nonlinear least squares function: in, for The optimal estimate of the parameter to be estimated at time, The value of the independent variable that makes the function take the minimum value, For the Item residual, for Moment The parameters to be estimated, For the The observed data of the residuals, For the The covariance matrix of the residuals, is the speed prediction value, is the prior statistic of velocity, is the equivalent residual function of IMU, for The state variables at time , is the position residual, is the velocity residual, for The current speed value measured by DVL at this moment.

[0059] The navigation error results of multi-source fusion of inertial navigation (INS), very low frequency radio cross-domain navigation / inertial navigation, low frequency long-range acoustic navigation / inertial navigation and very low frequency radio cross-domain navigation / low frequency long-range acoustic navigation / inertial navigation are as follows: Figure 7 shown.

[0060] like Figure 8 As shown, an underwater wide-area navigation and positioning construction system is used to execute an underwater wide-area navigation and positioning construction method, including: The calculation module 101 calculates the electric field strength of the very low frequency radio during long-distance propagation according to the transmission frequency of the very low frequency transmitter, and calculates the cross-domain navigation coverage according to the water penetration depth of the electric field strength; The first construction module 102 constructs a very low frequency radio cross-domain navigation network using a land-based deployment method, taking the cross-domain navigation coverage and GDOP distribution as thresholds; The second construction module 103 constructs a low-frequency long-range acoustic navigation network using a submarine buoy deployment method based on the water depth and terrain required for sound propagation; The integrated navigation and positioning module 104 performs wide-area navigation and positioning based on a very low frequency radio cross-domain navigation network, a low frequency long-range acoustic navigation network, and inertial navigation.

[0061] Through the collaborative work of the above modules, and through the integration of low-frequency long-range acoustic navigation and very low frequency radio cross-domain navigation, the scenario limitations of a single navigation technology have been broken through. Among them, low-frequency long-range acoustic navigation is centered on buoys to meet the wide-area navigation needs of the deep sea; very low frequency radio cross-domain navigation adopts a land-based construction to solve the navigation problems in nearshore shallow waters and complex terrain areas. The two work together to achieve wide-area and even global underwater navigation and positioning coverage from nearshore to deep sea, from simple to complex terrain, fully leveraging the advantages of both navigation technologies and making up for their respective shortcomings. Sound waves, as the information carrier for stable long-distance transmission in the ocean, ensure the stability of deep-sea navigation; very low frequency radio cross-domain navigation overcomes the application limitations of low-frequency acoustics in nearshore shallow waters and complex terrain, and through technical collaboration, improves the overall reliability and applicability of underwater navigation and positioning.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for constructing underwater wide-area navigation and positioning, characterized in that: include: S1: Calculate the electric field strength of the VLF radio during long-distance propagation based on the transmission frequency of the VLF transmitter, and calculate the cross-domain navigation coverage based on the electric field strength and water immersion depth; S2: Using cross-domain navigation coverage and GDOP distribution as thresholds, a land-based VLF radio cross-domain navigation network is constructed; S3: Based on the water depth and terrain required for sound propagation, a low-frequency long-range acoustic navigation network is constructed using submarine buoys. S4: Underwater wide-area navigation and positioning based on very low frequency radio cross-domain navigation network, low frequency long-range acoustic navigation network and inertial navigation.

2. The underwater wide-area navigation and positioning construction method according to claim 1, characterized in that: In step S1, the calculation expression for the electric field strength of very low frequency radio during long-distance propagation is: in, is the vertical electric field strength, is the spatial wave impedance, is the transmit power, For coverage, is the attenuation coefficient.

3. The underwater wide-area navigation and positioning construction method according to claim 1, characterized in that: Step S2 includes: S21: Land-based deployment of very low frequency radio stations; S22: Positioning error of a very low frequency radio station obtained using the hyperbolic positioning method; S23: Calculate GDOP between VLF radio stations; S24: Correct the positioning error of the VLF radio station according to the GDOP between the VLF radio stations and complete the construction of the VLF radio cross-domain navigation network.

4. The underwater wide-area navigation and positioning construction method according to claim 3, characterized in that: In step S23, the calculation expression of GDOP is: in, is the geometric dilution of precision, is the angle between the two pairs of ground navigation stations and the common navigation station, is half of the angle of the carrier relative to the baseline of the first pair of ground stations, is half of the angle of the carrier relative to the baseline of the second pair of ground stations, for and The correlation coefficient of .

5. The method for constructing underwater wide-area navigation and positioning according to claim 1, characterized in that: In step S3, the Gaussian beam tracking method is used to place the submarine buoys at the receiving and sending points of the reliable acoustic path, and the long-range acoustic channel of the reliable acoustic path is used to realize low-frequency long-range acoustic navigation; The reliable acoustic path is a path with a water depth greater than 3600m and flat terrain.

6. The underwater wide-area navigation and positioning construction method according to claim 5, characterized in that: The S3 steps include: S31: Calculate the complex sound pressure amplitude at each point in space beam by beam using the Gaussian beam equation; S32: Determine beam weight according to the uniform medium point source; S33: summing the complex sound pressure amplitudes at each point in space according to the beam weights to obtain the composite sound pressure; S34: Optimize reliable acoustic paths based on composite sound pressure.

7. The underwater wide-area navigation and positioning construction method according to claim 1, characterized in that: In step S4, When underwater unmanned platforms and submersibles are in shallow waters near the coast or in areas with complex terrain, a combined navigation method of very low frequency radio cross-domain navigation and inertial navigation is used; In deep sea areas, a combination of low-frequency long-range acoustic navigation and inertial navigation is used; In the connecting area between the near coast and the deep sea, a multi-source fusion navigation method of low-frequency radio cross-domain navigation, low-frequency long-range acoustic navigation and inertial navigation is adopted, and the fusion of multi-source information is achieved through the factor graph fusion algorithm; The deep sea area is a sea area with a distance greater than 5000km and a water depth greater than 3600m; The shallow water area near the coast is a sea area with a distance of less than 5000km and a water depth of less than 3600m.

8. The method for constructing underwater wide-area navigation and positioning according to claim 7, characterized in that: The factor graph fusion algorithm includes: Define model factors of multiple navigation networks; According to the observation value at the current moment, a joint probability distribution function is constructed, and a maximum a posteriori estimation model is constructed based on the joint probability distribution function; Under Gaussian noise, an unconstrained nonlinear least squares algorithm is used to solve the maximum a posteriori estimation model according to the model factors and obtain the optimal solution.

9. The underwater wide-area navigation and positioning construction method according to claim 8, characterized in that: The model factors include inertial navigation factors, very low frequency radio cross-domain navigation positioning model factors and low frequency long-range acoustic navigation positioning model factors, and the inertial navigation factors include IMU factors and IMU bias factors.

10. An underwater wide-area navigation and positioning construction system, configured to implement the underwater wide-area navigation and positioning construction method according to any one of claims 1 to 9, comprising: a calculation module, wherein the calculation module calculates the electric field strength of the very low frequency radio during long-distance propagation according to the transmission frequency of the very low frequency transmitter, and calculates the cross-domain navigation coverage range according to the water penetration depth of the electric field strength; A first building module, wherein the first building module uses the cross-domain navigation coverage and GDOP distribution as thresholds to build a very low frequency radio cross-domain navigation network using a land-based deployment method; A second construction module, wherein the second construction module constructs a low-frequency long-range acoustic navigation network using a submarine buoy deployment method based on the water depth and terrain required for sound propagation; An integrated navigation and positioning module performs wide-area navigation and positioning based on a very low frequency radio cross-domain navigation network, a low frequency long-range acoustic navigation network, and inertial navigation.

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