A method for improving precision of integrated navigation based on fusion of hydrological information

Abstract

The present application relates to a kind of based on the combination navigation precision promotion method of fusion hydrological information, belong to inertial navigation technical field, comprising the following steps: S1, based on the hydrological information of target navigation sea area, the sound speed profile of target navigation sea area and its each water layer beam angle are calculated;S2, based on the sound speed profile of the target navigation sea area and each water layer beam angle, obtain corrected doppler measurement speed;S3, based on the equivalent refraction after beam incidence angle, the compensated doppler measurement speed after the corrected doppler measurement speed is compensated;S4, the compensated doppler measurement speed and inertial navigation speed are fused, and the corrected ship or underwater vehicle navigation solution result is obtained.The present application fuses hydrological environment data and inertial navigation data, and the position accuracy and reliability of ship or underwater vehicle in long time autonomous navigation are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of inertial navigation technology, specifically relating to a method for improving the accuracy of integrated navigation based on fused hydrological information. Background Technology

[0002] Inertial navigation systems (INS) utilize inertial sensors such as accelerometers and gyroscopes to obtain velocity and position by integrating the acceleration of a moving vehicle, making it one of the core technologies for autonomous navigation and positioning. However, INS suffers from accumulated error drift over time, requiring periodic calibration or correction using external reference information. In environments with GNSS signals, INS is typically combined with GNSS to achieve high-precision positioning. However, in environments where GNSS signals are denied (interfered with or blocked) such as underwater or during wartime electronic warfare, the INS loses GNSS correction, resulting in significant drift errors after prolonged operation, making it difficult to meet the requirements for high-precision navigation.

[0003] To control INS error accumulation in the absence of GNSS, a common method is to introduce additional sensor information to correct the inertial navigation system (INS). This includes using a Doppler log or acoustic Doppler current profiler to measure the vehicle's velocity relative to the water or seabed, and using this velocity as an external reference to correct the INS velocity (often called the velocity damping method). Especially in underwater vehicles, ADCPs or DVLs installed under the hull are widely used to provide ground velocity measurements, thereby assisting the INS in suppressing drift. However, traditional SINS / DVL-assisted navigation methods often assume that the speed of sound in water is constant or estimate it using simple models. They frequently use default underwater sound speed and beam angle to resolve frequency shifts, without fully considering the effects of temperature, salinity, and depth gradients on the speed of sound in the actual marine environment. The speed of sound in seawater varies with temperature, salinity, and pressure (depth), causing refraction and propagation time errors in the sound wave transmission path, leading to systematic deviations in the Doppler velocity measurements. If these deviations are not corrected, they will be passed on to the navigation calculations, affecting the final positioning accuracy.

[0004] In existing technologies, some inertial / acoustic integrated navigation methods attempt to improve accuracy through simple sound velocity correction or attitude angle correction, but often fail to form a systematic and comprehensive correction scheme. For example, some methods adjust the sound velocity based on empirical constants, or only calibrate the Doppler velocity measurement and inertial navigation velocity under stable sea conditions. However, when ocean environmental parameters change rapidly or the attitude changes violently, it is still difficult to guarantee the accuracy of Doppler velocity measurement, making it difficult to achieve high-precision navigation. Summary of the Invention

[0005] In view of the shortcomings of existing technologies in terms of the decrease in inertial navigation accuracy in the absence of GNSS, the purpose of this invention is to provide a method for improving the accuracy of combined navigation based on the fusion of hydrological information. By fusing hydrological environmental data and inertial navigation data, the position accuracy and reliability of ships or underwater vehicles during long-term autonomous navigation can be significantly improved.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for improving the accuracy of integrated navigation based on fused hydrological information, comprising the following steps:

[0007] S1. Based on the hydrological information of the target navigation area, the sound speed profile of the target navigation area and the beam angle of each water layer are calculated.

[0008] S2. Based on the sound speed profile of the target navigation area and the beam angle of each water layer, the corrected Doppler measurement velocity is obtained;

[0009] S3. Based on the equivalent refraction beam incident angle, the corrected Doppler measurement velocity is compensated to obtain the compensated Doppler measurement velocity.

[0010] S4. The compensated Doppler measurement velocity is fused with the inertial navigation velocity to obtain the corrected navigation solution for the ship or underwater vehicle.

[0011] Preferably, the specific method of step S1 is as follows:

[0012] S11. Real-time collection of temperature, salinity, and depth data by temperature, salinity, and depth sensors installed on ships or underwater vehicles, or by obtaining average temperature, salinity, and depth data of the target navigation area from historical observations of the same location and season.

[0013] S12. Based on the hydrological information of the target navigation area, the sound speed profile of the target navigation area is calculated using the empirical formula for sound speed.

[0014] S13. Based on the sound velocity profile, the beam angle of the beam in each water layer is obtained by using the beam tracking method based on Snell's law.

[0015] Preferably, the specific method of step S2 is as follows:

[0016] S21. Based on the sound speed profile of the target navigation area and the beam angle of each water layer, obtain the beam propagation time and horizontal distance of each water layer, and then accumulate the total propagation time of each water layer beam to the seabed.

[0017] S22. Based on the sound speed profile of the target navigation area, the beam propagation time of each water layer, and the total propagation time of each water layer beam to the seabed, the average sound speed along the line of sight of each beam is obtained.

[0018] S23. Based on the average sound velocity along the line of sight of each beam, obtain the corrected measurement velocity of each beam;

[0019] S24. Collect the corrected beam measurement velocities into a vector to obtain the corrected Doppler measurement velocity.

[0020] Preferably, the specific method of step S3 is as follows:

[0021] S31. Based on the sound speed profile of the target navigation area and the horizontal distance of beam propagation in each water layer, the equivalent refracted beam incidence angle is obtained.

[0022] S32. Based on the incident angle of the beam after equivalent refraction, calculate the unit direction vector of each beam in the carrier coordinate system.

[0023] S33. Superimpose the unit direction vectors of each beam in the carrier coordinate system to form a geometric rotation matrix;

[0024] S34. Based on the geometric rotation matrix, the least squares method is used to compensate the corrected Doppler measurement velocity to obtain the compensated Doppler measurement velocity.

[0025] Preferably, the specific method of step S4 is as follows:

[0026] S41. Update the attitude using the inertial navigation system to obtain the updated attitude;

[0027] S42. The compensated Doppler measurement velocity and the inertial navigation velocity are fused using a horizontal damping algorithm to obtain the corrected velocity of the ship or underwater vehicle.

[0028] S43. Based on the corrected speed of the ship or underwater vehicle, and by substituting Earth parameters, perform a position update calculation to obtain the corrected position of the ship or underwater vehicle.

[0029] Compared with existing technologies, the present invention has the following advantages: Establishing an accurate sound velocity profile using hydrological environmental information can significantly improve the accuracy of Doppler velocimeter speed measurement, avoiding device errors introduced by inaccurate sound velocity assumptions in traditional methods; fully utilizing hydrological environmental information to correct inertial navigation and Doppler measurement errors in real time, thereby obtaining high-precision navigation calculation results, solving the problem of maintaining accuracy of inertial navigation during long-term operation under GNSS rejection conditions, and is suitable for ships and underwater vehicles with high navigation and positioning accuracy requirements in complex marine environments, improving the high accuracy and high reliability of navigation and positioning under conditions without satellite navigation signals. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on the drawings described below without creative effort.

[0031] Figure 1 This is a flowchart illustrating a method for improving the accuracy of integrated navigation based on fused hydrological information, according to an embodiment of the present invention.

[0032] Figure 2 This is a flowchart of step S1 in an embodiment of the present invention.

[0033] Figure 3 This is a flowchart of step S2 in an embodiment of the present invention.

[0034] Figure 4 This is a flowchart of step S3 in an embodiment of the present invention.

[0035] Figure 5 This is a flowchart of step S4 in an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. To make the above features and advantages of this invention more apparent and understandable, specific embodiments are provided below with reference to the accompanying drawings for detailed description.

[0037] like Figures 1 to 5 As shown, an embodiment of the present invention provides a method for improving the accuracy of integrated navigation based on fused hydrological information, comprising the following steps:

[0038] S1. Based on the hydrological information of the target navigation area, the sound speed profile of the target navigation area and the beam angle of each water layer are calculated.

[0039] S2. Based on the sound speed profile of the target navigation area and the beam angle of each water layer, the corrected Doppler measurement velocity is obtained;

[0040] S3. Based on the equivalent refraction beam incident angle, the corrected Doppler measurement velocity is compensated to obtain the compensated Doppler measurement velocity.

[0041] S4. The compensated Doppler measurement velocity is fused with the inertial navigation velocity to obtain the corrected navigation solution for the ship or underwater vehicle.

[0042] In this embodiment, the specific method of step S1 is as follows:

[0043] S11. Real-time collection of temperature, salinity, and depth data by temperature, salinity, and depth sensors installed on ships or underwater vehicles, or by obtaining average temperature, salinity, and depth data of the target navigation area from historical observations of the same location and season.

[0044] S12. Based on the hydrological information of the target navigation area, the sound speed profile of the target navigation area is calculated using the empirical formula for sound speed.

[0045] The empirical formula for sound speed can be the WD Wilson empirical formula, the Chen-Millero empirical formula, etc., which can update the sound speed profile in real time to adapt to environmental changes. For example, the sound speed profile of the target navigation area calculated using the WD Wilson empirical formula is as follows:

[0046] c k =1449.14+v tk +v pk +v Sk +v tpSk ;

[0047] Among them, c k Let v be the speed of sound at the k-th profile of the target navigation area. tk v is the temperature-dependent sound velocity compensation term for the k-th profile. pk v is the sound velocity compensation term related to depth for the k-th profile. Sk v is the sound velocity compensation term related to salinity for the k-th profile. tpSk This is the sound velocity compensation term for the k-th profile related to temperature, salinity, and depth;

[0048] in:

[0049] v tk =4.5721t - 4.4532 × 10 -2 t 2 -2.604×10 -4 t 3 +7.9851×10 -6 t 4 ;

[0050] v pk =1.60272×10 -1 p + 1.0268 × 10 -5 p2 +3.5216×10 -9 p 3 -3.3603×10 -12 p 4 ;

[0051] v Sk =1.39799(S-35)+1.69202×10 -3 (S-35) 2 ;

[0052] v tpSk =(S-35)(-1.1244×10 -2 t+7.7711×10 -7 t 2 +7.7016×10 -5 p-1.2943×10 -7 p 2 +3.1580×10 -8 pt+1.5790×10 -9 pt 2 )+p(-1.8607×10 -4 t+7.4812×10 -6 t 2 +4.5283×10 -8 t 3 )+p 2 (-2.5294×10 -7 t+1.8563×10 -9 t 2 )+p 3 (-1.9646×10 -10 t);

[0053] Where t is temperature, in degrees Celsius (°C); S is salinity, in parts per thousand (‰); and p is depth, in meters (m).

[0054] S13. Based on the sound velocity profile, the beam tracking method based on Snell's law is used to calculate the beam angle at each water layer. The specific formula is as follows:

[0055] ;

[0056] ;

[0057] Where, θ k θ0 is the beam angle of the k-th profile of the target navigation area, θ0 is the default beam angle of the acoustic Doppler velocimeter, and c0 is the default sound speed of the acoustic Doppler velocimeter.

[0058] In this embodiment, the specific method of step S2 is as follows:

[0059] S21. Based on the sound speed profile of the target navigation area and the beam angle of each water layer, the beam propagation time and horizontal beam propagation distance of each water layer are obtained as follows:

[0060] ;

[0061] ;

[0062] Where, Δt k Let Δz be the beam propagation time of the k-th profile of the target navigation area. k Let c be the water layer thickness of the k-th profile in the target navigation area. k Let θ be the speed of sound at the k-th profile of the target navigation area. k The beam angle of the k-th profile of the target navigation area; Δx k The horizontal beam propagation distance of the k-th profile in the target navigation area;

[0063] Then, the total propagation time T from each water layer beam to the seabed is calculated as follows:

[0064] ;

[0065] Where N is the number of water layers spaced at predetermined intervals;

[0066] S22. Based on the sound speed profile of the target navigation area, the beam propagation time of each water layer, and the total propagation time of each water layer beam to the seabed, the average sound speed along the line-of-sight direction of each beam is obtained. for:

[0067] ;

[0068] in, The propagation time of the j-th beam in the k-th profile of the target navigation area;

[0069] S23. Based on the average sound velocity along the line-of-sight direction of each beam, the corrected measurement velocity of each beam is obtained as follows:

[0070] ;

[0071] in, For the velocity measured after correction of the j-th beam, Δf j Let f0 be the Doppler frequency shift of the j-th beam, f0 be the fundamental transmission frequency, and M be the number of beams of the acoustic Doppler velocimeter.

[0072] S24. Collect the corrected beam measurement velocities into a vector to obtain the corrected Doppler measurement velocity. for:

[0073] ;

[0074] in, The measurement speed after correction for the first beam. The measurement speed is the corrected speed for the Mth beam.

[0075] In this embodiment, the specific method of step S3 is as follows:

[0076] S31. Based on the sound speed profile of the target navigation area and the horizontal beam propagation distance of each water layer, the equivalent refracted beam incidence angle β is obtained. eff,j for:

[0077] ;

[0078] in, The horizontal propagation distance of the j-th beam in the k-th profile of the target navigation area. Let be the water layer thickness of the j-th beam in the k-th layer profile of the target navigation area;

[0079] S32. Based on the incident angle of the beam after equivalent refraction, calculate the unit direction vector n of each beam in the carrier coordinate system. j ;

[0080] ;

[0081] in, Let be the azimuth angle of the j-th beam in the horizontal plane of the carrier coordinate system;

[0082] S33. The geometric rotation matrix R is formed by superimposing the unit direction vectors of each beam in the carrier coordinate system as follows:

[0083] ;

[0084] in, This is the transpose of the unit direction vector of the first beam in the carrier coordinate system. This is the transpose of the unit direction vector of the Mth beam in the carrier coordinate system;

[0085] S34. Based on the geometric rotation matrix R, the least squares method is used to compensate the corrected Doppler measurement velocity to obtain the compensated Doppler measurement velocity. for:

[0086] ;

[0087] in, , , These represent the eastward, northward, and upward velocities in the navigation coordinate system, R.T R is the transpose of the geometric rotation matrix R.

[0088] In this embodiment, the specific method of step S4 is as follows:

[0089] S41. The attitude is updated using the inertial navigation system to obtain the updated attitude. The specific formula is as follows:

[0090] ;

[0091] in, For t m time n Tie b The coordinate system transformation matrix of the system; For t m-1 time n Tie b The coordinate system transformation matrix of the system; For M RV The transpose of ( ); M RV ( ) is the equivalent rotation vector function, which satisfies: I is a 3×3 identity matrix. For the equivalent rotation vector, For the reason Construct the antisymmetric cross product matrix; Δt is the sampling time, Δt=t m -t m-1 ; for b System relative to i The equivalent rotation vector of the system; For discrete time t m-1 The angular velocity of the navigation frame relative to the inertial frame in the n-frame is given by t. m-1 The rotation of the navigation system caused by the Earth's rotation at all times The rotation of the n-frame caused by the curvature of the Earth's surface when the inertial navigation system moves. composition; For discrete time t m-2 The angular velocity of the navigation frame relative to the inertial frame in the n-frame is given by t. m-2 The rotation of the navigation system caused by the Earth's rotation at all times The rotation of the n-frame caused by the curvature of the Earth's surface when the inertial navigation system moves. composition;

[0092] in:

[0093] ;

[0094] Where, Δθ m For t m The gyroscope angle increment at time Δθ m-1 For t m-1The gyroscope angle increment at any given moment;

[0095] S42. The compensated Doppler measurement velocity and the inertial navigation velocity are fused using a horizontal damping algorithm to obtain the corrected velocity of the ship or underwater vehicle:

[0096] ;

[0097] in, For the corrected t m The speed of the ship or underwater vehicle at any given time, where K is the damping coefficient determined based on the accuracy of the inertial navigation equipment and Doppler velocimetry instrument. For t m-1 The speed of a ship or underwater vehicle at any given time. For t m-1 Time to t m The velocity increment of the n-th system at time n For t m-1 Time to t m The velocity increment of harmful acceleration at all times The compensated Doppler velocity measurement;

[0098] in:

[0099] ;

[0100] ;

[0101] ;

[0102] in, For t m-1 Time to t m Midpoint of the sampling interval at time t (m-1 / 2) The angular velocity of the navigation frame relative to the inertial frame in the navigation system, Δv m For t m The velocity increment at time Δv m-1 For t m-1 The velocity increment at any given moment For t m-1 Time to t m The amount of rotational error compensation at the instantaneous velocity. For t m-1 Time to t m The paddling error compensation amount at a given moment, Δθ m Let Δθ be the angular increment vector measured by the gyroscope during the m-th sampling period. m-1 This is the angular increment vector measured by the gyroscope during the (m-1)th sampling period;

[0103] in:

[0104] ;

[0105] in, For t m-1 Time to t m The midpoint of the sampling interval at time t (m-1 / 2) Earth's rotational angular velocity under the navigation system, For t m-1 Time to t m The midpoint of the sampling interval at time t (m-1 / 2) The angular velocity of the navigation system relative to the Earth system in the current navigation system. For t m-1 Time to t m The midpoint of the sampling interval at time t (m-1 / 2) The velocity vector of the carrier in the navigation system. For t m-1 Time to t m The midpoint of the sampling interval at time t (m-1 / 2) The gravitational acceleration vector in the navigation system;

[0106] S43. Based on the corrected speed of the ship or underwater vehicle, and substituting Earth parameters, perform a position update calculation to obtain the corrected position of the ship or underwater vehicle. for:

[0107] ;

[0108] ;

[0109] ;

[0110] Among them, M PV Let v be the velocity-to-position transformation matrix. n R is the corrected component vector of the ship's or underwater vehicle's velocity in the navigation coordinate system; M R is the radius of curvature of the meridian. N Let be the radius of curvature of the ramustralis circle, and h be the height of the ship or underwater vehicle. The latitude is the local latitude.

[0111] Experimental Example: The method of this invention was applied to an Autonomous Underwater Vehicle (AUV) being tested in nearshore waters. The test waters were approximately 100 meters deep, with significant temperature and salinity gradients. The AUV was equipped with an inertial navigation unit (positioning accuracy 1 nautical mile / hour), a DVL (300 kHz frequency), and a temperature, salinity, and depth sensor. First, the inertial navigation system was initialized based on the AUV's diving position. The AUV then navigated underwater for one hour, during which GNSS signals were completely blocked, and navigation was performed solely using the method of this invention. The results showed that the positioning error calculated by a traditional inertial navigation / Doppler log was 0.24 nautical miles / hour, while the positioning error using the method of this invention was 0.158 nautical miles / hour, significantly improving navigation accuracy. This verifies the effectiveness of this invention in using hydrological information-corrected DVL to constrain inertial navigation drift.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the accuracy of integrated navigation based on fused hydrological information, characterized in that, Includes the following steps: S1. Based on the hydrological information of the target navigation area, the sound speed profile of the target navigation area and the beam angle of each water layer are calculated. S2. Based on the sound speed profile of the target navigation area and the beam angle of each water layer, the corrected Doppler measurement velocity is obtained; S3. Based on the equivalent refraction beam incident angle, the corrected Doppler measurement velocity is compensated to obtain the compensated Doppler measurement velocity. S4. The compensated Doppler measurement velocity is fused with the inertial navigation velocity to obtain the corrected navigation solution for the ship or underwater vehicle.

2. The method for improving the accuracy of integrated navigation based on fused hydrological information according to claim 1, characterized in that, The specific method for step S1 is as follows: S11. Real-time collection of temperature, salinity, and depth data by temperature, salinity, and depth sensors installed on ships or underwater vehicles, or by obtaining average temperature, salinity, and depth data of the target navigation area from historical observations of the same location and season. S12. Based on the hydrological information of the target navigation area, the sound speed profile of the target navigation area is calculated using the empirical formula for sound speed. S13. Based on the sound velocity profile, the beam angle of the beam in each water layer is obtained by using the beam tracking method based on Snell's law.

3. The method for improving the accuracy of integrated navigation based on fused hydrological information according to claim 1, characterized in that, The specific method for step S2 is as follows: S21. Based on the sound speed profile of the target navigation area and the beam angle of each water layer, obtain the beam propagation time and horizontal distance of each water layer, and then accumulate the total propagation time of each water layer beam to the seabed. S22. Based on the sound speed profile of the target navigation area, the beam propagation time of each water layer, and the total propagation time of each water layer beam to the seabed, the average sound speed along the line of sight of each beam is obtained. S23. Based on the average sound velocity along the line of sight of each beam, obtain the corrected measurement velocity of each beam; S24. Collect the corrected beam measurement velocities into a vector to obtain the corrected Doppler measurement velocity.

4. The method for improving the accuracy of integrated navigation based on fused hydrological information according to claim 3, characterized in that, The specific method for step S3 is as follows: S31. Based on the sound speed profile of the target navigation area and the horizontal distance of beam propagation in each water layer, the equivalent refracted beam incidence angle is obtained. S32. Based on the incident angle of the beam after equivalent refraction, calculate the unit direction vector of each beam in the carrier coordinate system. S33. Superimpose the unit direction vectors of each beam in the carrier coordinate system to form a geometric rotation matrix; S34. Based on the geometric rotation matrix, the least squares method is used to compensate the corrected Doppler measurement velocity to obtain the compensated Doppler measurement velocity.

5. The method for improving the accuracy of integrated navigation based on fused hydrological information according to claim 1, characterized in that, The specific method for step S4 is as follows: S41. Update the attitude using the inertial navigation system to obtain the updated attitude; S42. The compensated Doppler measurement velocity and the inertial navigation velocity are fused using a horizontal damping algorithm to obtain the corrected velocity of the ship or underwater vehicle. S43. Based on the corrected speed of the ship or underwater vehicle, and by substituting Earth parameters, perform a position update calculation to obtain the corrected position of the ship or underwater vehicle.

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