An underwater low-frequency long-range acoustic navigation method and system

Abstract

The application relates to the technical field of navigation, and particularly discloses a kind of underwater low-frequency remote acoustic navigation method and system, and the method comprises the following steps: S1: according to the inertial navigation accuracy threshold of underwater vehicle, the basic positioning unit of seabed acoustic beacon arrangement is determined;S2: according to the basic positioning unit, the maximum duration of deployment sea area and the inertial navigation accuracy of underwater vehicle, the arrangement pattern of seabed acoustic beacon is determined;S3: according to the arrangement pattern, seabed acoustic beacon is arranged;S4: using the seabed acoustic beacon arranged to provide full submarine long navigation positioning service for underwater vehicle.The application realizes low-frequency remote acoustic wide area coverage application, and provides full submarine long navigation positioning service with high precision for underwater vehicle.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of navigation technology, in particular to a kind of underwater low frequency long-range acoustic navigation method and system. BACKGROUND

[0002] Underwater vehicle is applied in the field such as underwater topographic survey, marine geological exploration, seawater detection, marine environment monitoring due to its flexible use, high comprehensive benefit, applicable to dangerous environment, low life cost and other significant characteristics. Underwater navigation positioning technology is one of the key technologies for underwater vehicle to complete its mission, and is the basic guarantee for effective implementation of long-range navigation, task operation and safe recovery.

[0003] Due to the inherent characteristics of marine environment and water medium, the commonly used radio and optical navigation on water surface cannot be used underwater. Underwater vehicle needs to constantly float to the water surface to receive satellite navigation information to maintain navigation accuracy, which affects operation efficiency. As the only information carrier that can stably propagate over a long distance in marine medium, underwater acoustic navigation positioning provides wide-area positioning service for underwater vehicle and other carriers, but its action distance can only reach several hundred kilometers, and the full-sea coverage construction will have the problems of great engineering implementation difficulty and low efficiency-cost ratio. SUMMARY

[0004] The present application aims to solve the above problems. To this end, the present application provides a kind of underwater low frequency long-range acoustic navigation method and system, which realizes low frequency long-range acoustic wide-area coverage application and provides full-submarine long-time high-precision navigation positioning service for underwater vehicle. The present application designs the layout interval (side length) of the basic positioning unit according to the inertial navigation calibration threshold of underwater vehicle, adopts the application mode of "M vertical lines N horizontal lines, service area refueling" to construct, designs the layout distance between vertical lines and horizontal lines according to the maximum time length of inertial navigation accuracy of underwater vehicle, and avoids the problems of great engineering implementation difficulty and low efficiency-cost ratio of low frequency long-range acoustic navigation full-sea coverage. The layout scheme of low frequency long-range acoustic navigation adopts square network division method, and blind area and the influence of seabed topography on low frequency long-range acoustic navigation sound propagation are set at the same time. The application of low frequency long-range acoustic navigation is combined with inertial navigation autonomous navigation equipment, and when the inertial navigation accuracy of underwater vehicle exceeds the error, underwater calibration is carried out in time, and full-submarine long-time high-precision navigation positioning service is provided for underwater vehicle.

[0005] The present application provides a kind of underwater low frequency long-range acoustic navigation method, and the technical scheme adopted is as follows: comprising the following steps:

[0006] S1: according to the inertial navigation accuracy calibration threshold of underwater vehicle, the basic positioning unit of seabed acoustic beacon layout is determined;

[0007] S2: according to the basic positioning unit, the maximum time length of the inertial navigation accuracy of the deployment sea area and the underwater vehicle, determine the layout pattern of the seabed acoustic beacon;

[0008] S3: according to the layout pattern, the seabed acoustic beacon is laid out;

[0009] S4: using the laid seabed acoustic beacon to provide full submarine long navigation positioning service for the underwater vehicle.

[0010] Further, in step S1, according to the inertial navigation accuracy threshold, the layout interval of the seabed acoustic beacon is determined.

[0011] Further, in step S1, the basic positioning unit is a square, and the seabed acoustic beacon is laid at the end point of the square, and the layout interval is the side length of the square.

[0012] Further, in step S2, the layout pattern adopts the form of M longitudinal lines and N transverse lines, the basic positioning unit is arranged on the longitudinal line and the transverse line, the layout interval between the longitudinal lines and the transverse lines is calculated according to the maximum time length of the inertial navigation accuracy of the underwater vehicle, and the number and layout position of the longitudinal lines and the transverse lines are determined according to the deployment sea area, the basic positioning unit and the layout interval.

[0013] Further, in step S2, the maximum time length of the inertial navigation accuracy is determined according to the inertial navigation device configured by the underwater vehicle; and the layout interval is calculated according to the maximum time length of the inertial navigation accuracy and the speed of the underwater vehicle.

[0014] Further, in step S2, the layout interval is adjusted to be an integral multiple of the side length of the basic positioning unit.

[0015] Further, the layout interval is 3000km, and the side length of the basic positioning unit is 500km.

[0016] Further, in step S3, the candidate layout position of the seabed acoustic beacon is obtained from the layout pattern, if the actual seabed trench opening angle at the candidate layout position is greater than or equal to the critical trench opening angle, the seabed acoustic beacon is deployed at the candidate layout position; if the actual seabed trench opening angle is less than the critical trench opening angle, the seabed acoustic beacon layout position is moved outward from the basic positioning unit.

[0017] Further, in step S4, the underwater vehicle enters the basic positioning unit, and directly corrects the inertial navigation underwater by using the factor graph combination method, and the underwater vehicle does not need to float to the water surface.

[0018] The application also provides an underwater low-frequency long-range acoustic navigation system, which adopts the technical scheme as follows: comprising a basic positioning unit calculation module, a layout pattern calculation module and a seabed acoustic beacon,

[0019] The basic positioning unit calculation module is configured to determine the basic positioning unit of the seabed acoustic beacon arrangement according to the inertial navigation accuracy threshold of the underwater vehicle.

[0020] The arrangement array calculation module is configured to determine the arrangement array of the seabed acoustic beacon according to the basic positioning unit, the deployment sea area, and the maximum duration of the inertial navigation accuracy of the underwater vehicle.

[0021] The seabed acoustic beacon is arranged according to the arrangement array, and is configured to provide full-submarine long-duration navigation and positioning services for the underwater vehicle.

[0022] The one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0023] 1. The present application adopts the array form of M longitudinal lines and N transverse lines, and adjacent basic positioning units share seabed acoustic beacons, and the number and position of longitudinal and transverse lines are set in combination with the deployment sea area boundary and blind area; compared with full-sea area arrangement without optimization, the number of acoustic beacons is significantly reduced, and the workload and cost of equipment procurement and seabed deployment are reduced.

[0024] 2. The present application provides support for reasonably designing the arrangement array of M longitudinal lines and N transverse lines by keeping the inertial navigation accuracy at the maximum duration, calculating the basic distance (such as 3108km) based on the speed of the underwater vehicle, reserving redundancy, and determining the arrangement interval (such as 3000km) in combination with the side length of the basic positioning unit.

[0025] 3. The present application determines the square basic positioning unit according to the inertial navigation accuracy threshold of the underwater vehicle and in combination with the parameters of the underwater acoustic ranging sensor. The seabed acoustic beacons at the four endpoints of the basic positioning unit can meet the calibration requirements of inertial navigation, avoid calibration failure caused by improper beacon arrangement parameters, and ensure that the positioning result is highly matched with the inertial navigation accuracy requirement of the underwater vehicle.

[0026] 4. The present application forms a coverage network of M longitudinal lines and N transverse lines by combining multiple basic positioning units, and provides long-duration high-precision navigation for the underwater vehicle in the full-submarine state in the full-sea area with the least number of beacons, without relying on external positioning means or frequent surfacing correction, and perfectly adapts to the actual operation requirements of the underwater vehicle for long-time and large-range diving.

[0027] Additional aspects and advantages of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood by the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0028] 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 prior art description. Obviously, the drawings described in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0029] Figure 1 is a flow chart of the method provided by the present application.

[0030] Figure 2 is a curve diagram of the laying interval and the positioning accuracy of the underwater vehicle provided by the present application.

[0031] Figure 3 is an inertial navigation accuracy error divergence diagram of the underwater vehicle provided by the present application.

[0032] Figure 4 is a schematic diagram of the full sea area range of the seabed acoustic beacon.

[0033] Figure 5 is a schematic diagram of the seabed acoustic beacon provided by the present application, which is laid according to the M longitudinal line and N transverse line mode.

[0034] Figure 6 is a schematic diagram of the inertial navigation correction provided by the present application. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the present application clearer, the following will combine the drawings in the present application to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the protection scope 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.

[0036] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures or characteristics described in combination with the embodiment or example are contained in at least one embodiment or example 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 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 application and the features of the different embodiments or examples without contradiction.

[0037] The following will be described in combination withFigures 1 to 6 Further detailed description of the present application, describes an underwater low frequency long-range acoustic navigation method and system:

[0038] In this embodiment, as Figure 1 indicated, an underwater low frequency long-range acoustic navigation method is provided, comprising the following steps:

[0039] S1: According to the inertial navigation accuracy threshold of underwater vehicle, determine the basic positioning unit of the seabed acoustic beacon layout.

[0040] The basic positioning unit is a square, and the seabed acoustic beacon is laid at the end point of the square. According to the inertial navigation accuracy threshold, the layout interval of the seabed acoustic beacon is determined, that is, the side length of the square.

[0041] According to the parameters of underwater acoustic ranging sensor, the qualitative relationship between the layout interval and the positioning accuracy of underwater vehicle is analyzed, as Figure 2 . The inertial navigation accuracy threshold is set to 500m, and through Figure 2 , the maximum layout interval that meets the navigation accuracy threshold is 500km. Setting the layout interval of the seabed acoustic beacon to 500km can meet the inertial navigation calibration requirement.

[0042] Considering the one-way propagation delay between the seabed acoustic beacon and the underwater vehicle, at least 4 seabed acoustic beacons are needed to complete the positioning of the underwater platform. Let the coordinates of the seabed acoustic beacon be , the position coordinates of the underwater vehicle be , , the underwater sound speed be , the one-way propagation time delay between the mth seabed acoustic beacon and the underwater vehicle be , the distance between the mth seabed acoustic beacon and the underwater vehicle be . According to the geometric position relationship, the following equation group is obtained:

[0043]

[0044] Solving the equation can obtain the three-dimensional position coordinates of the underwater vehicle.

[0045] The above equation group can be written as , when the matrix is invertible, according to the least square method, the optimal solution is: , wherein. is the coefficient matrix of the equation group, is the unknown vector to be solved, is the constant term matrix of the equation group, is the matrix transpose.

[0046] The underwater vehicle (positioning target) receives feedback signals from each seabed beacon, obtains the signal propagation time, and further obtains the pseudo-range between the underwater vehicle and each seabed beacon , . The approximate position of the underwater vehicle can be roughly given by an autonomous navigation device such as an inertial navigation device, as the initial estimated position of the receiver. The coordinates of the initial estimated position are written as . In addition, the solution vector of the position not only includes a spatial vector, but also includes a sound ranging error, so the actual initial estimated value is , is the initial estimated value of the sound ranging error. The phase shift from the first position to the next iteration is estimated using the first position. This quantity will be used as the convergence criterion for the iterative algorithm, i.e. the true position of the underwater vehicle can be calculated. Wherein, the difference between the true position and the estimated position is represented by the vector , is the estimated deviation of the horizontal coordinate, is the estimated deviation of the vertical coordinate, is the estimated deviation of the depth coordinate, is the estimated deviation of the ranging error.

[0047] Therefore, positioning the underwater vehicle using low-frequency long-range acoustic navigation generally requires four seabed acoustic beacons to form a basic positioning unit. Further, multiple basic positioning units are combined to achieve full sea coverage, providing full-submarine long-endurance high-precision navigation and positioning services for underwater vehicles. The basic positioning unit of the embodiment adopts a square with a side length of 500 km, and seabed acoustic beacons are arranged at the four endpoints of the square.

[0048] S2: According to the basic positioning unit, the maximum duration of the inertial navigation accuracy of the underwater vehicle, and the deployment sea area, determine the layout of the seabed acoustic beacons.

[0049] The layout adopts the form of M longitudinal lines and N horizontal lines, the basic positioning units are arranged on the longitudinal lines and the horizontal lines, the layout spacing between the longitudinal lines and the horizontal lines is calculated according to the maximum duration of the inertial navigation accuracy of the underwater vehicle, and the number and layout position of the longitudinal lines and the horizontal lines are determined according to the deployment sea area, the basic positioning unit and the layout spacing. On the longitudinal lines and the horizontal lines, the basic positioning units are connected end to end, i.e. adjacent basic positioning units share seabed acoustic beacons.

[0050] S2.1: Calculate the layout spacing. Determine the maximum duration of the inertial navigation accuracy according to the inertial navigation device configured for the underwater vehicle; calculate the layout spacing according to the maximum duration of the inertial navigation accuracy and the speed of the underwater vehicle.

[0051] The underwater vehicle is usually configured with inertial autonomous navigation, but its error accumulates and diverges over time, such as Figure 3As shown in the figure, the divergence process of inertial navigation latitude and longitude position error is illustrated in the following equation.

[0052]

[0053] in, For latitude error, For longitude error, The top is drifting eastward. For northward gyroscope drift, The top is drifting upwards. This refers to the eastward attitude error. This refers to the northward attitude error. For the attitude error of the sky, This is the initial latitude error. The angular velocity of Earth's rotation. For time, Latitude.

[0054] This embodiment uses a laser gyroscope inertial navigation positioning accuracy better than 2 nautical miles / 14 days as the design threshold. This means that after activation or external correction, the inertial autonomous navigation can autonomously maintain navigation and positioning accuracy for 14 days without requiring other external positioning methods. Furthermore, the deployment spacing of the low-frequency long-range acoustic navigation system is designed with the underwater vehicle's 14-day journey as a reference. The underwater vehicle's speed is typically 5 knots; therefore, using a speed of 5 knots, the underwater vehicle's 14-day journey is 3108 km. Considering factors such as ocean current interference and equipment errors, and reserving a certain redundancy, combined with the 500 km side length of the basic positioning unit, the deployment spacing in this embodiment is set to 3000 km.

[0055] In determining the deployment spacing, the side length of the basic positioning unit can be appropriately reduced, making the deployment spacing an integer multiple of the side length of the basic positioning unit. For example, the deployment spacing can be set to 2700 km, and the side length of the basic positioning unit can be set to 450 km.

[0056] S2.2: Determine the number and location of vertical and horizontal lines.

[0057] The specific process is as follows: the 3000km ocean area between the M longitudinal line and the N horizontal line is set as the deployment blind zone; then the boundary of the deployment sea area and the side length of the basic positioning unit are input into the square network partitioning method, and the deployment blind zone between the M longitudinal line and the N horizontal line is set at the same time; the actual deployment positions of the longitudinal line and the horizontal line are calculated.

[0058] Taking the deployment across the entire Pacific Ocean as an example, the implementation process of this step is explained:

[0059] like Figure 4 As shown, with a deployment spacing of 500 km for the underwater acoustic beacons, the entire Pacific Ocean coverage was achieved.Figure 4 The red dots in the figure represent the bottom acoustic beacons, and hundreds of bottom acoustic beacons will exist, which will have problems of great engineering implementation difficulty and low cost-effectiveness.

[0060] In this embodiment, the Pacific Ocean boundary coordinates (extracted from the NOAA ocean database), the basic positioning unit (square, 500 km in length), and the blind area range (maximum length of 3000 km) are input into the Grid grid division tool of ArcGIS to generate a layout grid map (layout array). As shown in Figure 5 , this embodiment is in the form of 2 longitudinal lines and 3 transverse lines. Compared with Figure 4 and Figure 5 , the number of bottom acoustic beacons used is significantly reduced, greatly reducing the engineering implementation workload and cost.

[0061] S3: Deploying bottom acoustic beacons according to the layout array.

[0062] The candidate deployment positions of each bottom acoustic beacon are obtained from the layout array, the global / regional bottom topography database is called, and the actual bottom trench opening angle at the candidate deployment position is determined in combination with the shipborne multi-beam echo sounder and other equipment. Considering the influence of the bottom topography on the low-frequency long-range acoustic navigation sound propagation shielding, if the actual bottom trench opening angle is greater than or equal to the critical trench opening angle, the bottom acoustic beacon is deployed at the candidate deployment position; if the actual bottom trench opening angle is less than the critical trench opening angle, the deployment position of the bottom acoustic beacon is adjusted, which is moved in the direction outside the basic positioning unit, preferably in the direction inside the blind area, to the nearest position without topographic shielding influence, and the bottom acoustic beacon is deployed. As shown in Figure 5 , there are two bottom acoustic beacons whose positions are moved into the blind area due to topographic shielding, and the green dots represent the moved deployment positions.

[0063] S4: Providing full-submarine long-duration high-precision navigation and positioning services for underwater vehicles using the deployed bottom acoustic beacons.

[0064] When the precision of the underwater vehicle is out of tolerance, the underwater vehicle enters the basic positioning unit to correct the inertial navigation "service area refueling" by using the factor graph combination method to correct the inertial navigation directly underwater, without the need for the underwater vehicle to float to the surface to receive satellite navigation information. The bottom acoustic beacon can provide full-submarine long-duration high-precision navigation and positioning services for underwater vehicles.

[0065] As shown in Figure 6 , the inertial navigation correction process based on the low-frequency long-range acoustic navigation factor graph combination algorithm: the navigation variable nodes are position, velocity, and heading, the error variable nodes include attitude error, velocity error, position error, gyro random drift, and accelerometer random constant drift, and the navigation variable nodes between different times are updated by the variable factor nodes of the inertial measurement unit (IMU) with the highest update frequency The connection between error variable nodes at different times is formed by error factor nodes based on the system error propagation law. Connect, measurement factor nodes This includes low-frequency long-range acoustic navigation measurement factors derived from seabed acoustic beacons. Using nonlinear solutions and optimization methods such as Gauss-Newton, the navigation variables of the underwater vehicle's calibration platform at all times are jointly optimized to achieve high-precision navigation information output from the calibration platform.

[0066] definition The navigation variables of the time-based metrology calibration platform are The error variable of the system with built-in IMU is The navigation state variables include the position, velocity, and attitude quaternions of the calibration platform; the error variables include gyroscope random drift and dial indicator random drift; and the built-in IMU measurements are... Underwater low-frequency long-range acoustic navigation measurement is Defined from the initial moment. Up to time k (current time) The set of variable nodes is , Variable nodes are a set of navigation state variables and navigation sensor system error variables; defined from the initial time... up to the current moment Measurement information set , ,in, yes Measurement information at time.

[0067] This embodiment also provides an underwater low-frequency long-range acoustic navigation system, which adopts the following technical solution: including a basic positioning unit calculation module, a deployment array calculation module, and an underwater acoustic beacon.

[0068] The basic positioning unit calculation module is used to determine the basic positioning unit for the deployment of seabed acoustic beacons based on the inertial navigation accuracy calibration threshold of the underwater vehicle.

[0069] The deployment array calculation module is used to determine the deployment array of seabed acoustic beacons based on the basic positioning unit, the deployment sea area, and the maximum duration of the inertial navigation accuracy of the underwater vehicle.

[0070] The underwater acoustic beacons are deployed according to the array pattern to provide underwater vehicles with full-submersion, long-endurance navigation and positioning services.

[0071] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; 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 of underwater low frequency long range acoustic navigation, characterized in that, The method comprises the following steps: S1: determining a basic positioning unit of the deployment of the seabed acoustic beacon according to an inertial navigation accuracy threshold of the underwater vehicle; S2: determining a deployment array of the seabed acoustic beacon according to the basic positioning unit, the deployment sea area and the maximum duration of the inertial navigation accuracy of the underwater vehicle; S3: deploying the seabed acoustic beacon according to the deployment array; S4: providing the underwater vehicle with full-submarine long-duration navigation positioning service by using the deployed seabed acoustic beacon.

2. A method of underwater low frequency long range acoustic navigation as claimed in claim 1, wherein, In step S1, the deployment interval of the seabed acoustic beacon is determined according to the inertial navigation accuracy threshold.

3. A method of underwater low frequency long range acoustic navigation as claimed in claim 2, wherein, In step S1, the basic positioning unit is a square, and the seabed acoustic beacon is deployed at the end points of the square, and the deployment interval is the side length of the square.

4. A method of underwater low frequency long range acoustic navigation as claimed in claim 1, wherein, In step S2, the deployment array adopts the form of M longitudinal lines and N transverse lines, the basic positioning unit is arranged on the longitudinal lines and the transverse lines, the deployment interval between the longitudinal lines and between the transverse lines is calculated according to the maximum duration of the inertial navigation accuracy of the underwater vehicle, and the number and deployment position of the longitudinal lines and the transverse lines are determined according to the deployment sea area, the basic positioning unit and the deployment interval.

5. A method of underwater low frequency long range acoustic navigation as claimed in claim 4, wherein, In step S2, the maximum duration of the inertial navigation accuracy is determined according to the inertial navigation device configured by the underwater vehicle, and the deployment interval is calculated according to the maximum duration of the inertial navigation accuracy and the speed of the underwater vehicle.

6. A method of underwater low frequency long range acoustic navigation as claimed in claim 4 or 5, characterised in that, In step S2, the deployment interval is adjusted to an integral multiple of the side length of the basic positioning unit.

7. A method of underwater low frequency long range acoustic navigation as claimed in claim 6, wherein, The deployment interval is 3000 km, and the side length of the basic positioning unit is 500 km.

8. A method of underwater low frequency long range acoustic navigation as claimed in claim 1, wherein, In step S3, the candidate deployment position of the seabed acoustic beacon is obtained from the deployment array, if the actual seabed trench opening angle at the candidate deployment position is greater than or equal to the critical trench opening angle, the seabed acoustic beacon is deployed at the candidate deployment position; If the actual seabed trench opening angle is less than the critical trench opening angle, the seabed acoustic beacon deployment position is moved outward from the basic positioning unit.

9. A method of underwater low frequency long range acoustic navigation as claimed in claim 1, wherein, In step S4, the underwater vehicle enters the basic positioning unit, and the inertial navigation is directly corrected underwater in a factor graph combination manner, and the underwater vehicle does not need to float to the water surface.

10. An underwater low frequency long range acoustic navigation system characterized by, The device is used to perform the underwater low-frequency long-range acoustic navigation method according to any one of claims 1 to 9, comprising a basic positioning unit calculation module, a deployment array calculation module and a seabed acoustic beacon, The basic positioning unit calculation module is used to determine a basic positioning unit of the deployment of the seabed acoustic beacon according to an inertial navigation accuracy threshold of the underwater vehicle; The deployment array calculation module is used to determine a deployment array of the seabed acoustic beacon according to the basic positioning unit, the deployment sea area and the maximum duration of the inertial navigation accuracy of the underwater vehicle; The seabed acoustic beacon is deployed according to the deployment array and is used to provide the underwater vehicle with full-submarine long-duration navigation positioning service.

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