Underwater wide-area navigation positioning construction method and system

Abstract

The present application relates to navigation positioning technical field, especially underwater wide-area navigation positioning method and system, method includes according to the transmission frequency of very low frequency transmitting station to calculate the electric field intensity in the long-distance transmission process of very low frequency radio, according to the electric field intensity to calculate the cross-domain navigation coverage range of water depth;With the threshold of cross-domain navigation coverage range and GDOP distribution, the land-based layout method is used to construct very low frequency radio cross-domain navigation network;With the water depth and terrain required for sound propagation as the benchmark, the submarine buoy layout method is used to construct low-frequency long-range acoustic navigation network;According to the very low frequency radio cross-domain navigation network, low-frequency long-range acoustic navigation network and inertial navigation, underwater wide-area navigation positioning is carried out.The present application realizes the multi-source fusion navigation mode of low-frequency radio cross-domain navigation, low-frequency long-range acoustic navigation and inertial navigation through factor graph fusion algorithm, and realizes navigation positioning in underwater wide-area range.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of navigation positioning, in particular to an underwater wide-area navigation positioning construction method and system. 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, and the propagation distance is extremely short, 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 it cannot work normally in turbid seawater environment. This makes the underwater navigation positioning means relatively scarce, which becomes 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 an underwater wide-area navigation positioning construction method and system. 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 underwater wide-area navigation positioning is realized.

[0006] The present application provides an underwater wide-area navigation positioning construction method, comprising:

[0007] S1: calculating the electric field intensity of VLF radio in the process of long-distance propagation according to the transmitting frequency of VLF transmitting station, and calculating the coverage range of cross-domain navigation according to the water depth of electric field intensity;

[0008] S2: constructing the VLF radio cross-domain navigation network by land-based layout mode with the coverage range of cross-domain navigation and GDOP distribution as thresholds;

[0009] S3: constructing the low-frequency long-range acoustic navigation network by submarine buoy layout mode with the water depth and terrain required for sound propagation as the benchmark;

[0010] S4: underwater wide-area navigation and positioning according to the VLF radio cross-domain navigation network, the low-frequency long-range acoustic navigation network, and inertial navigation.

[0011] Further, in S1, the calculation expression of the electric field intensity of VLF radio in the process of long-distance propagation is:

[0012]

[0013] wherein, is the vertical electric field intensity, is the space wave impedance, is the transmitting power, is the coverage range, is the attenuation coefficient.

[0014] Further, S2 includes:

[0015] S21: laying VLF radio stations by land-based layout mode;

[0016] S22: obtaining the positioning error of VLF radio stations by hyperbolic positioning method;

[0017] S23: calculating the GDOP between VLF radio stations;

[0018] 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.

[0019] Further, the calculation expression of GDOP is:

[0020]

[0021] wherein, is the geometric dilution of precision, is the angle between two pairs of ground navigation stations relative to the common navigation station, is half of the opening angle of the carrier relative to the baseline of the first pair of ground stations, half of the opening angle of the carrier relative to the baseline of the second pair of ground stations, is the correlation coefficient of .

[0022] Further, in the S3 step, the Gauss beam tracking method is adopted to arrange the seafloor buoy in the receiving point and the sending point of the reliable acoustic path, and the low-frequency long-range acoustic navigation is realized by using the reliable acoustic path long-range acoustic channel.

[0023] The reliable acoustic path is a path with a water depth greater than 3600m and a flat topography.

[0024] Further, the S3 step comprises:

[0025] S31: The complex sound pressure amplitude of each point in space is calculated by the Gauss beam equation;

[0026] S32: The beam weight is determined according to the uniform medium point source;

[0027] S33: The complex sound pressure of each point in space is summed according to the beam weight to obtain the composite sound pressure;

[0028] S34: The reliable acoustic path is optimized according to the composite sound pressure.

[0029] Further, in the S4 step,

[0030] When the underwater unmanned platform and the submersible are in the shallow water area near the coast and the complex topography area, the combined navigation mode of very low frequency radio cross-domain navigation and inertial navigation is adopted;

[0031] In the deep sea area, the combined navigation mode of low-frequency long-range acoustic navigation and inertial navigation is adopted;

[0032] In the connecting area of the near shore and the deep sea, the 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 the factor graph fusion algorithm;

[0033] The deep sea area is a sea area with a distance greater than 5000km and a water depth greater than 3600m;

[0034] The shallow water area near the coast is a sea area with a distance less than 5000km and a water depth less than 3600m.

[0035] Further, the factor graph fusion algorithm comprises:

[0036] Defining the model factor of the multi-navigation network;

[0037] 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.

[0038] In the Gaussian noise, the maximum posterior estimation model is solved according to the model factor by using an unconstrained nonlinear least square algorithm, and an optimal solution is obtained.

[0039] 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.

[0040] The application further provides an underwater wide-area navigation positioning construction system for executing the above-mentioned underwater wide-area navigation positioning construction method, comprising:

[0041] A calculation module is configured to calculate the electric field intensity of the very low frequency radio during long-distance transmission according to the transmission frequency of the very low frequency transmitting station, and calculate the cross-domain navigation coverage range according to the water depth of the electric field intensity;

[0042] A first construction module is configured to construct a very low frequency radio cross-domain navigation network in a land-based arrangement mode with the cross-domain navigation coverage range and GDOP distribution as thresholds;

[0043] A second construction module is configured to construct a low frequency long-range acoustic navigation network in a seabed buoy arrangement mode with the water depth and the terrain required for acoustic propagation as references;

[0044] An integrated navigation positioning module is configured to perform wide-area navigation positioning according to the very low frequency radio cross-domain navigation network, the low frequency long-range acoustic navigation network and the inertial navigation.

[0045] The above one or more technical solutions in the embodiments of the application have at least one of the following technical effects:

[0046] The application connects and combines the low frequency long-range acoustic navigation and the very low frequency radio cross-domain navigation, breaks through the scene limitation of single navigation technology, and satisfies the wide-area navigation demand in deep sea with the low frequency long-range acoustic navigation taking the buoy as the core; the very low frequency radio cross-domain navigation is constructed in a land-based mode to solve the navigation problem in the near-shore shallow water area and the complex terrain area, and the two modes are cooperated to realize the wide-area or even global underwater navigation positioning coverage from the near-shore to the deep sea and from the simple terrain to the complex terrain, fully play the advantages of the two navigation technologies and make up for the respective shortcomings, the acoustic wave is used as the information carrier for long-distance stable transmission in the ocean to guarantee the stability of the deep sea navigation, and the very low frequency radio cross-domain navigation overcomes the application limitation of the low frequency acoustic navigation in the near-shore shallow water and the complex terrain, and improves the overall reliability and applicability of the underwater navigation positioning through the technical cooperation.

[0047] Additional aspects and advantages of the present application will be given in part in the following description, become apparent from the following description, or be learned by the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the present application or the prior art, the drawings required to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0049] Figure 1 is a flowchart of a method for constructing an underwater wide-area navigation and positioning provided by the present application.

[0050] Figure 2 is a schematic diagram of the cross-domain navigation coverage of the very low frequency radio cross-domain navigation network of the embodiment of the present application.

[0051] Figure 3 is a schematic diagram of the relationship between GDOP and positioning accuracy of the embodiment of the present application.

[0052] Figure 4 is a schematic diagram of the low-frequency long-range acoustic propagation process of the embodiment of the present application.

[0053] Figure 5 is a schematic diagram of the acoustic propagation process considering the terrain of the embodiment of the present application.

[0054] Figure 6 is a schematic diagram of the method for constructing an underwater wide-area navigation and positioning of the present application.

[0055] Figure 7 is a schematic diagram of the navigation error result of the embodiment of the present application.

[0056] Figure 8 is a schematic diagram of the structure of a system for constructing an underwater wide-area navigation and positioning provided by the present application.

[0057] Reference signs:

[0058] 101, calculation module; 102, first construction module; 103, second construction module; 104, integrated navigation and positioning module. DETAILED DESCRIPTION

[0059] 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 work 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.

[0060] In the description of the present application, 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 combination with the embodiment or example are contained in at least one embodiment or example of the embodiments of the present application. In the present application, 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 suitable manner in any one or more embodiments or examples. In addition, the skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0061] The present application will be described below in combination with Figures 1 to 8 A method and system for constructing an underwater wide-area navigation positioning system are described.

[0062] As Figure 1 shown, a method for constructing an underwater wide-area navigation positioning system comprises:

[0063] S1: calculating the electric field intensity of very low frequency radio in long-distance propagation process according to the transmission frequency of very low frequency transmitting station, and calculating the cross-domain navigation coverage range according to the electric field intensity and the water entry depth;

[0064] The transmission frequency of the very low frequency transmitting station is obtained, and the electric field intensity of the very low frequency radio in long-distance propagation process is calculated according to the transmission frequency. The calculation expression of the electric field intensity of the very low frequency radio in long-distance propagation process is:

[0065]

[0066] Among them, is the vertical electric field intensity, and the unit is , is the space wave impedance, and the unit is (ohm), is the transmission power, and the unit is kW, is the coverage range, and the unit is km, is the attenuation coefficient.

[0067] In some specific embodiments of the present application, , , Very low frequency radio frequency.

[0068] The electromagnetic wave is transmitted downward from air to seawater, and the amplitude attenuation multiple is:

[0069]

[0070] wherein, is the amplitude attenuation multiple, is the underwater attenuation rate of electromagnetic wave, is the water entry depth;

[0071] The calculation expression of the underwater attenuation rate of electromagnetic wave is:

[0072]

[0073] wherein, is the water medium conductivity, and the seawater medium is generally taken as 4s / m, is the permeability of seawater, and is generally taken as .

[0074] The very low frequency radio navigation adopts a magnetic antenna with high magnetic permeability and multiple turns of coil to receive the very low frequency radio signal underwater, and the calculation expression of the initial sensitivity of the magnetic antenna is:

[0075]

[0076] 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 the magnetic core, is the very low frequency, .

[0077] According to the water entry depth , the amplitude attenuation multiple is calculated, and according to the value of , the vertical electric field intensity at the water entry depth is calculated, and the propagation distance of the vertical electric field intensity at the water entry depth is greater than the sensitivity of the magnetic antenna receiver, so that the very low frequency radio cross-domain navigation network cross-domain navigation coverage range is obtained.

[0078] In some specific embodiments of the present application, the very low frequency transmitting station transmits with a power of 1MW, the sensitivity of the magnetic antenna receiver is 0.1nT as a threshold value, the cross-domain navigation with a water entry depth of 15m is taken as a calculation depth, and then the very low frequency radio cross-domain navigation network cross-domain navigation coverage range is 5884km, as shown in Figure 2 .

[0079] S2: using land-based arrangement to build the VLF radio cross-domain navigation network, taking the cross-domain navigation coverage and GDOP distribution as thresholds;

[0080] S21: using land-based arrangement to arrange VLF radio stations;

[0081] Considering the cross-domain navigation coverage and GDOP distribution of VLF radio, the VLF radio navigation uses land-based arrangement to complete the construction of VLF radio cross-domain navigation network, which can realize navigation and positioning under a certain water depth within a range of 5000 kilometers, and solve the problem of wide-area underwater navigation and positioning in shallow water areas and complex terrain areas within the near-shore range.

[0082] S22: using hyperbolic positioning method to obtain the positioning error of the VLF radio station;

[0083] 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 measurement performance of the equipment 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:

[0084]

[0085] wherein, is the positioning error, is the geometric dilution of precision, is the ranging error.

[0086] S23: calculating the GDOP between VLF radio stations;

[0087] The GDOP calculation formula of the single station chain configured by the two pairs of ground navigation stations (one station public) composed of three stations is as follows:

[0088]

[0089] wherein, is the geometric dilution of precision, is the angle between the two pairs of ground navigation stations relative to the public 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, is and is the correlation coefficient of and Whether independent of each other.

[0090] Different in different quadrants, in I, III quadrant: , in II, IV quadrant: .

[0091] The geometric dilution of precision is very different at different receiving positions of the receiver, and the geometric dilution of precision is very large on the baseline delay line of the transmitting station and cannot be positioned. The user receiver can select an area with a GDOP less than 5-10 according to different positioning needs. When high positioning accuracy is required, an area with a GDOP less than 3 is preferred.

[0092] In the range of 5000km from the very low frequency transmitting station, the geometric dilution of precision (GDOP) of the receiver positioning is less than 5, and high-precision positioning can be achieved, as shown in Figure 3 , the abscissa is the north latitude and the ordinate is the east longitude. Figure 3

[0093] S24: Correct the positioning error of the very low frequency radio station according to the GDOP between the very low frequency radio stations, and complete the construction of the very low frequency radio cross-domain navigation network.

[0094] S3: Based on the water depth and terrain required for sound propagation, a low-frequency long-range acoustic navigation network is constructed by using a seabed buoy arrangement method;

[0095] When the underwater acoustic navigation and positioning equipment works in a lower frequency band, long-distance transmission and wide-area coverage can be achieved. The non-uniform acoustic medium characteristics of the marine environment will cause the sound to bend and reverse during long-distance propagation, causing the sound signal to reach the receiving point along different paths. In the acoustic navigation receiving signal end, it mainly reflects the multiple signals of the direct sound and the reflected sound reflected by the sea surface and the seabed, which gradually attenuate with the arrival time. In the process of underwater acoustic navigation and positioning, it is usually expected to use direct sound signals for navigation calculation, so the design of low-frequency long-range acoustic navigation network needs to consider the water depth and terrain required for sound propagation and propagation loss, so as to meet the low-frequency long-range acoustic navigation and positioning accuracy. In addition, considering that the underwater is usually active in 1-1000m sea depth, the Gaussian beam tracking method is used to arrange the seabed buoy at the receiving point and the transmitting point of the reliable sound path, and the reliable sound path is used to realize low-frequency long-range acoustic navigation; the reliable sound path is a flat terrain with a water depth greater than 3600m.

[0096] S31: Calculate the complex sound pressure amplitude of each point in space by the Gaussian beam equation;

[0097] The water depth and terrain required for sound propagation are calculated by using the Gaussian beam tracking method, and the sound beam equation is: ​

[0098]

[0099] where, is the complex sound pressure amplitude of the Gaussian beam at spatial position is the propagation distance along the beam axis, is the transverse coordinate perpendicular to the beam axis, is the initial amplitude, is the sound speed distribution along is the geometric spreading characteristic coefficient of the beam, is the complex curvature parameter controlling the beam width, is the angular frequency of the sound wave, is the propagation time along is the complex curvature parameter controlling the degree of phase bending of the beam, is the complex unit. and The initial conditions of

[0100] are:

[0101]

[0102] where, is the initial beam width, is the initial value of the complex curvature parameter controlling the degree of phase bending of the beam, is the initial value of the complex curvature parameter controlling the beam width.

[0103] S32: Determine the beam weight according to the uniform medium point source;

[0104] The weighting of each sound beam is determined according to the standard point source problem in the uniform medium. For the point source, the corresponding weighting of the sound beam is:

[0105]

[0106] where, is the weight of the beam in the direction, is the radian corresponding to the included angle between the sound beams, is the propagation speed of the sound beam in water.

[0107] and are dimensionless, the unit of is m / s, 2 the unit of is m

[0108] ​S33: summing the complex sound pressure amplitudes of each point in space according to the beam weight to obtain a composite sound pressure;

[0109] S34: optimizing the reliable sound path according to the composite sound pressure.

[0110] Assuming that the water depth of the sea area is 3800m and the seabed sediment is silty sand type, the sound speed profile adopts Munk standard sound speed profile. The transmission depth is 3000m underwater, 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 changes dramatically. 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.

[0111] 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.

[0112] 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 very low frequency radio cross-domain navigation and inertial navigation is adopted;

[0113] In the deep sea area, the combined navigation mode of low-frequency long-range acoustic navigation and inertial navigation is adopted;

[0114] In the combination area of near-shore and deep sea, the 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 the factor graph fusion algorithm;

[0115] The deep sea area is a sea area with a distance greater than 5000km and a water depth greater than 3600m;

[0116] The near-shore shallow water area is a sea area with a distance less than 5000km and a water depth less than 3600m.

[0117] The factor graph fusion algorithm includes:

[0118] Defining the model factor of the multi-navigation network;

[0119] The model factor includes the inertial navigation factor, the very low frequency radio cross-domain navigation positioning model factor and the low-frequency long-range acoustic navigation positioning model factor, and the inertial navigation factor includes the IMU factor and the IMU bias factor;

[0120] The calculation expression of the IMU factor is:

[0121]

[0122] wherein, is the IMU factor, is the state variable at time t, is the state variable at time t, is the IMU bias parameter at time t, is the coverage, is the state variable at time t, is the observation at time t, is predicted as the IMU observation data.

[0123] The calculation expression of the IMU bias factor is:

[0124]

[0125] wherein, is the IMU bias factor, is the predicted IMU bias, is the IMU bias parameter at time t.

[0126] The calculation expression of the VLF radio cross-domain navigation positioning model factor is:

[0127]

[0128] wherein, is the VLF radio cross-domain navigation positioning model factor, is the radio observation data at time t, is the predicted radio observation data.

[0129] The calculation expression of the LF long-range acoustic navigation positioning model factor is:

[0130]

[0131] wherein, is the LF long-range acoustic navigation positioning model factor, is the acoustic observation data at time t, is the predicted acoustic observation data.

[0132] 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;

[0133] The process of finding the maximum a posteriori estimate of variables using nonlinear optimization methods, given observations. Assume the joint probability distribution function is... ,in, This refers to all observations received up to the current time. ,in, for The maximum a posteriori of the parameter to be estimated is given by the observed data at time t:

[0134]

[0135] in, for The maximum a posteriori of the parameter to be estimated at time step 1. The value of the independent variable that makes the function reach its maximum value, These are the parameters to be estimated.

[0136] Under Gaussian noise, an unconstrained nonlinear least squares algorithm is used to solve the maximum a posteriori estimation model based on the model factors to obtain the optimal solution;

[0137] For a Gaussian noise distribution, the maximum a posteriori estimation problem becomes the problem of minimizing the following nonlinear least squares function:

[0138]

[0139] in, for The optimal estimate of the parameter to be estimated at time t. The value of the independent variable that makes the function reach its minimum value, For the first Item residual, for Time of the first The parameter to be estimated, For the first The observed data of the residuals, For the first The covariance matrix of the residuals. For speed prediction, For the prior statistic of velocity, The equivalent residual function of the IMU. for The state variable at time t, For positional residuals, For the velocity residual, for The current velocity value measured by DVL at time point.

[0140] The navigation error results 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 multi-source fusion are shown as follows. Figure 7

[0141] As shown in Figure 8 An underwater wide-area navigation positioning construction system is used to perform an underwater wide-area navigation positioning construction method, and the system comprises:

[0142] The calculation module 101 calculates the electric field intensity of the very low frequency radio in the long-distance propagation process according to the transmission frequency of the very low frequency transmission station, and calculates the cross-domain navigation coverage range according to the water depth of the electric field intensity;

[0143] The first construction module 102 uses the cross-domain navigation coverage range and the GDOP distribution as thresholds, and uses a land-based arrangement method to construct a very low frequency radio cross-domain navigation network;

[0144] The second construction module 103 uses the water depth and the terrain required for acoustic propagation as a reference, and uses a submarine buoy arrangement method to construct a low frequency long-range acoustic navigation network;

[0145] The integrated navigation positioning module 104 performs wide-area navigation positioning according to the very low frequency radio cross-domain navigation network, the low frequency long-range acoustic navigation network and the inertial navigation.

[0146] Through the cooperative work of the above modules, through the connection and combination of low frequency long-range acoustic navigation and very low frequency radio cross-domain navigation, the scene limitation of single navigation technology is broken. Among them, the low frequency long-range acoustic navigation takes the submarine buoy as the core to meet the wide-area navigation demand in the deep sea; the very low frequency radio cross-domain navigation uses land-based construction to solve the navigation problem in the near-shore shallow water area and the complex terrain area, and the two cooperate to realize the wide-area or even global underwater navigation positioning coverage from the near-shore to the deep sea, from the simple to the complex terrain, fully play the advantages of the two navigation technologies and make up for the shortcomings of each other. As the information carrier for long-distance stable propagation in the ocean, the acoustic wave ensures the stability of the deep sea navigation; 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 underwater navigation positioning through technical cooperation.

[0147] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.​

Claims

1. A method for constructing an underwater wide-area navigation and positioning system, characterized in that, include: S1: Calculate the electric field strength of 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 the water depth. S2: Using the cross-domain navigation coverage and GDOP distribution as thresholds, a very low frequency radio cross-domain navigation network is constructed using a land-based deployment method; S3: Based on the water depth and topography required for sound propagation, a low-frequency long-range acoustic navigation network is constructed by deploying underwater moorings; 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; When underwater unmanned platforms and submersibles are in shallow waters near the coast or in complex terrain areas, a combination 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 area where nearshore and deep sea meet, a multi-source fusion navigation method is adopted, which combines low-frequency radio cross-domain navigation, low-frequency long-range acoustic navigation, and inertial navigation. The fusion of multi-source information is achieved through factor graph fusion algorithm. The deep-sea area refers to sea areas with a distance greater than 5000km and a water depth greater than 3600m; The shallow waters near the coast are sea areas less than 5000 km away and less than 3600 m deep.

2. The underwater wide-area navigation and positioning construction method according to claim 1, characterized in that, In step S1, the expression for calculating the electric field strength of very low frequency radio waves during long-distance propagation is: in, The vertical electric field strength is... For spatial wave impedance, For transmission power, For coverage area, This 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: Very low frequency radio stations are deployed using a land-based deployment method; S22: The positioning error of very low frequency radio stations is obtained by using the hyperbolic positioning method; S23: Calculate the GDOP between very low frequency radio stations; S24: Correct the positioning error of VLF radio stations based on the GDOP between 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 expression for calculating GDOP is: in, Geometric precision factor, The angle between the two pairs of ground navigation stations and the common navigation station. It is half the angle subtended by the carrier relative to the baseline of the first pair of ground stations. It is half the angle subtended by the carrier relative to the baseline of the second pair of ground stations. for and The correlation coefficient.

5. The underwater wide-area navigation and positioning construction method according to claim 1, characterized in that, In step S3, the Gaussian beam tracking method is used to deploy the underwater mooring at the receiving and transmitting points of the reliable acoustic path, and to realize low-frequency long-range acoustic navigation using the reliable acoustic path remote acoustic channel. 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, Step S3 includes: S31: Calculate the complex sound pressure amplitude at each point in space using the Gaussian beam equation; S32: Determine beam weights based on a point source in a uniform medium; S33: Sum the complex sound pressure amplitudes at various points 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, The factor graph fusion algorithm includes: Define the model factors for multi-navigation networks; Based on the observations at the current moment, construct the joint probability distribution function, and then construct the maximum a posteriori estimation model 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 based on the model factors to obtain the optimal solution.

8. The underwater wide-area navigation and positioning construction method according to claim 7, characterized in that, The model factors include inertial navigation factors, very low frequency radio cross-domain navigation and positioning model factors, and low frequency long-range acoustic navigation and positioning model factors. The inertial navigation factors include IMU factors and IMU bias factors.

9. An underwater wide-area navigation and positioning construction system, configured to implement the underwater wide-area navigation and positioning construction method as described in any one of claims 1 to 8, comprising: The calculation module calculates the electric field strength of very low frequency radio during long-distance propagation based on the transmission frequency of the very low frequency transmitter, and calculates the cross-domain navigation coverage range based on the water depth of the electric field strength. The first construction module uses the cross-domain navigation coverage and GDOP distribution as thresholds to construct a very low frequency radio cross-domain navigation network using a land-based deployment method. The second construction module uses the water depth and topography required for sound propagation as a benchmark to construct a low-frequency long-range acoustic navigation network by deploying underwater moorings. The 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.

Images