阅读说明：本技术 基于格网拓扑结构迭代最佳环域点提高水下导航精度方法 (Method for improving underwater navigation precision based on grid topological structure iteration optimal ring domain point ) 是由 郑伟 李钊伟 赵世杰 于 2021-06-30 设计创作，主要内容包括：本发明公开了一种基于格网拓扑结构迭代最佳环域点提高水下导航精度方法,包括：通过航迹起点小环域格网匹配定位策略,得到水下潜器航迹起点的最佳匹配位置；根据水下潜器航迹起点的最佳匹配位置,通过航迹终点变角度三层环域匹配定位策略,生成大环域待匹配格网点；迭代计算大环域待匹配格网点的匹配效能评价指标,并按最优原则获得大环域范围内水下潜器航迹终点的最佳匹配位置,以实现水下潜器航迹终点的有效匹配定位,进而修正INS系统控制参数并辅助完成水下潜器长航时长航距的航行目标。通过本发明所述的方法,提高了水下潜器重力辅助导航的匹配精度。(The invention discloses a method for improving underwater navigation precision based on a grid topological structure iteration optimal ring domain point, which comprises the following steps: obtaining the optimal matching position of the track starting point of the underwater vehicle through a track starting point small-ring area grid matching positioning strategy; generating lattice points to be matched in a large ring area by a track end point angle-variable three-layer ring area matching positioning strategy according to the optimal matching position of the track starting point of the underwater vehicle; and (3) iteratively calculating the matching efficiency evaluation index of the grid points to be matched in the large ring area, and obtaining the optimal matching position of the underwater vehicle track terminal in the large ring area range according to the optimal principle so as to realize the effective matching and positioning of the underwater vehicle track terminal, further correcting the INS system control parameters and assisting in finishing the navigation target of the underwater vehicle with long voyage and long voyage distance. By the method, the matching precision of gravity-assisted navigation of the underwater vehicle is improved.)

1. A method for improving underwater navigation precision based on a grid topological structure iteration optimal ring domain point is characterized by comprising the following steps:

obtaining the optimal matching position of the track starting point of the underwater vehicle through a track starting point small-ring area grid matching positioning strategy;

generating lattice points to be matched in a large ring area by a track end point angle-variable three-layer ring area matching positioning strategy according to the optimal matching position of the track starting point of the underwater vehicle;

and (3) iteratively calculating the matching efficiency evaluation index of the grid points to be matched in the large ring area, and obtaining the optimal matching position of the underwater vehicle track terminal in the large ring area range according to the optimal principle so as to realize the effective matching and positioning of the underwater vehicle track terminal, further correcting the INS system control parameters and assisting in finishing the navigation target of the underwater vehicle with long voyage and long voyage distance.

2. The method for improving underwater navigation accuracy based on the iterative optimal ring domain points of the grid topology structure as claimed in claim 1, wherein the construction process of the track starting point small ring domain grid matching positioning strategy is as follows:

obtaining INS track output inertia of a certain section of underwater vehicle navigation according to sampling time interval delta tLeader sequence S₁,S₂,…,S_L}; where L represents the sample sequence length of the INS flight path, S₁、S₂、…、S_LRepresenting each track point in the inertial navigation sequence;

from { S₁,S₂,…,S_LExtracting to obtain position coordinates and actually measured gravity values corresponding to each track point, and constructing to obtain a position coordinate sequence { (x)₁,y₁),(x₂,y₂),…,(x_L,y_L) The measured gravity value sequence of the underwater vehicle and the g₁,g₂,…,g_L}；

Starting point S with track in inertial navigation sequence₁Position coordinates (x)₁,y₁) Centered at 3 σ₀Constructing a small ring domain as the maximum extended search boundary radius; wherein σ₀Representing the standard deviation of inertial navigation drift errors when the sampling interval is delta t;

according to the north east rotation angle theta₀And determining the total number and position coordinates of grid points to be matched in the small ring domain by using a ring radius proportional average coefficient lambda, and constructing to obtain a grid point set to be matched in the small ring domain.

3. The method for improving underwater navigation accuracy based on iterative optimal ring domain points of grid topology structure as claimed in claim 1, wherein the position coordinates of each grid point to be matched in the small ring domainThe calculation formula of (a) is as follows:

wherein the content of the first and second substances,andrespectively represents the horizontal and vertical coordinates r of the jth lattice point on the ith small ring_iDenotes the radius, β, of the ith ring in the small ring_jThe rotation angle of the jth grid point on each ring of the small ring domain is shown.

4. The mesh topology iterative optimal ring domain point-based method for improving accuracy of underwater navigation of claim 3,

r_i＝3σ₀λi

β_j＝j·θ₀

wherein i is 1,2, …, and the maximum value of ij is 1,2, …, and the maximum value of jθ₀∈(0,360]；λ∈(0,1]。

5. The method for improving the accuracy of underwater navigation based on the iterative optimal ring area points of the grid topological structure as claimed in claim 4, wherein the optimal matching position of the track starting point of the underwater vehicle is obtained by a track starting point small ring area grid matching positioning strategy, and the method comprises the following steps:

starting the track S₁Position coordinates (x)₁,y₁) And the position coordinates of each lattice point to be matched in the small ring areaA point set to be matched is used as the true position of the starting point of the flight path;

mapping a point set to be matched of the true position of the track starting point to a gravity reference graph point by point, and taking the gravity value at the nearest gravity reference grid point as the gravity value of the point to be matched to obtain (x)₁,y₁) Corresponding theoretical gravity valueAndcorresponding theoretical gravity value

Wherein, C represents the grid resolution of the gravity reference map, mapt (·,) represents the gravity value matrix of the gravity reference map according to the grid point position, [ · ] represents rounding;

obtaining the best matching position of the track starting point of the underwater vehicle according to the principle of minimizing the absolute value of the gravity deviation

Wherein when i is 0 and j is 0,is x₁、Is y₁。

6. The method for improving underwater navigation accuracy based on the optimal iterative loop points of the grid topology structure as claimed in claim 5, wherein the track end point angle-variable three-layer loop matching positioning strategy is constructed as follows:

according to a track starting point S in an inertial navigation sequence₁Position coordinates (x)₁,y₁) And track end point S_LPosition coordinates of(x_L,y_L) Determining course information and range information of the underwater vehicle navigation:

wherein d is_INSRepresenting that the distance measurement between the start point and the end point of the inertial navigation track is described by h epsilon [0, + ∞) norm, and calculating the Euclidean distance by setting h to be 2; alpha is alpha_INSRepresenting a course arc angle taking the abscissa of the coordinate system as a positive direction;

according toAnd estimating to obtain the central position coordinate (x) of the large ring area according to the course information and the range information of the underwater vehicle navigation_O,y_O)：

With (x)_O,y_O) Centered on R_maxConstructing and obtaining an angle-variable three-layer topological structure annular grid point region covering a true end point of a flight path as a search boundary radius of the maximum extension, and recording the region as a large annular region;

taking the grid resolution C of the gravity reference graph as the span interval of each ring of the large ring area to obtain the total ring number of the large ring area

The grid resolution C and the middle ring of the gravity reference mapRadius ofReference angle generated as each lattice point in large domainAccording to the principle of 'inner times and outer halves', determining the span angle between adjacent lattice points on the inner ring of the large ring area to beThe span angle between adjacent lattice points on the outer ring isConstructing and obtaining a large-ring domain grid point set to be matched by combining the total ring number M; wherein, the large-ring domain grid point set to be matched is a variable-angle three-ring layer grid point topological structure.

7. The method for improving underwater navigation accuracy based on the iterative optimal ring domain points of the grid topology structure as claimed in claim 6, wherein the generation mode of the grid points to be matched in the large ring domain is as follows:

the total number of the large-loop domain under the three mechanisms of 1 sigma-EPMP, 2 sigma-EPMP and 3 sigma-EPMP is respectively recorded asWherein, sigma represents the standard deviation of inertial navigation accumulated drift errors;

to pairRespectively corrected to obtain the total ring number M 'of the large ring domain in the three corrected mechanisms'₁、M′₂、M′₃：

Wherein ξ ═ 1,2 and 3 respectively correspond to a 1 σ -EPMP mechanism, a 2 σ -EPMP mechanism and a 3 σ -EPMP mechanism;

according to the corrected three mechanismsTotal Ring number M 'of Large Ring Domain'₁、M′₂、M′₃Obtaining the radius R of each ring of the large ring domain under three mechanisms_1,j、R_2,j、R_3,j：

R_ξ,ζ＝ζC，ζ＝1,2,…,M′_ξ…(6)

Wherein R is_ξ,ζA radius of a zeta-th ring representing a large ring domain under a zeta-th mechanism;

according to the total ring number M 'of the large ring domain under the three corrected mechanisms'₁、M′₂、M′₃Obtaining the intermediate ring radius of the large ring domain under three mechanisms

Intermediate ring radius of large ring domain according to three mechanismsObtaining the reference angle generated by each lattice point in the large domain under three mechanisms

And (5) obtaining the lattice points to be matched of the large ring area under different mechanisms according to the steps (5) to (8).

8. The mesh topology iterative optimal ring domain point-based method for improving accuracy of underwater navigation of claim 7,

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 1 sigma-EPMP mechanismThe calculation formula of (a) is as follows:

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 2 sigma-EPMP mechanismThe calculation formula of (a) is as follows:

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 3 sigma-EPMP mechanismThe calculation formula of (a) is as follows:

9. the method for improving underwater navigation accuracy based on the iterative optimal ring domain points of the grid topological structure as claimed in claim 8, wherein the step of iteratively calculating the matching efficiency evaluation index of the grid points to be matched in the large ring domain and obtaining the optimal matching position of the track end point of the underwater vehicle in the large ring domain according to the optimal principle comprises the following steps:

determining the total number N of lattice points to be matched on an inner-middle-outer ring layer of a large ring domain under the xi mechanism_ξ；

Taking the r-th grid point to be matched of the large ring domain under the xi mechanism as the end point of the flight path to be evaluated and recording the r-th grid point as a pointWherein r ∈ {1,2, …, N_ξ}；

Will be dottedCorresponding position (x) in the gravity reference map_r,y_r) Comparing with the grid resolution C of the gravity reference diagram, and obtaining the nearest neighbor point on the gravity reference diagram according to the rounding principleGrid point base_L；

Base the grid points_LCorresponding gravity valueAs a pointAn approximation of the value of gravity;

according to the grid point base_LExtracting the position coordinates on the gravity reference map, the navigation speed and the navigation course of the underwater vehicle to obtain pointsCorresponding gravity map track sequenceAnd corresponding nearest neighbor gravity sequence

Will be provided withSequence of gravity values { g actually measured with underwater vehicle₁,g₂,…,g_LComparing, calculating the evaluation index of matching efficiency, and recording as MSD_r；

Sequentially calculating to obtain the matching efficiency evaluation indexes of all lattice points to be matched on the inner-middle-outer ring layer of the large ring area under the xi mechanism, and obtaining the matching efficiency evaluation index set and { MSD (maximum data set) of all lattice points to be matched on the inner-middle-outer ring layer of the large ring area under the xi mechanism_r|r＝1,2,…,N_ζ}；

Based on { MSD_r|r＝1,2,…,N_ζAnd (6) screening according to an optimal principle to obtain an optimal matching position of the track terminal of the underwater vehicle in the large-ring-area range

10. A system for improving underwater navigation precision based on a grid topological structure iteration optimal ring domain point is characterized by comprising:

the resolving module is used for obtaining the optimal matching position of the track starting point of the underwater vehicle through a track starting point small-ring area grid matching positioning strategy;

the generating module is used for generating lattice points to be matched in a large ring area through a track end point angle-variable three-layer ring area matching positioning strategy according to the optimal matching position of the track starting point of the underwater vehicle;

and the iteration determination module is used for iteratively calculating the matching efficiency evaluation index of the lattice points to be matched in the large ring area, and obtaining the optimal matching position of the underwater vehicle track terminal in the large ring area according to the optimal principle so as to realize the effective matching and positioning of the underwater vehicle track terminal, further correct the control parameters of the INS system and assist in finishing the long-endurance long-range navigation target of the underwater vehicle.

Technical Field

The invention belongs to the cross technical field of underwater navigation, ocean mapping and the like, and particularly relates to a method for improving underwater navigation precision based on a grid topological structure iteration optimal ring region point.

Background

An Inertial Navigation System (INS) is a core Navigation System for realizing autonomous Navigation of an underwater vehicle, and has a short-time high-precision positioning characteristic, but inherent errors of Inertial components and multiple integration of positioning calculation and the like cause that INS errors are accumulated and dispersed along with time and are difficult to meet a high-precision positioning target of the underwater vehicle in a long journey, so that the INS needs to be regularly calibrated to keep the Navigation precision.

The gravity field information, which is one of the inherent geographic attributes of the earth, is not easily affected by uncertain environments such as climate, sea wave and the like and shows long-term relative stability, so that the gravity field information is suitable for being used for assisted navigation, and the current gravity assisted navigation system is used as an important technology for underwater assisted INS navigation and has become an international hot topic for research of domestic and foreign learners.

The matching algorithm is the core of the gravity-assisted inertial navigation system, and the current common gravity matching algorithm mainly comprises a Sondiya inertial terrain-assisted navigation algorithm SITAN, an iterative nearest contour point algorithm ICCP and a terrain contour matching algorithm TERCOM. In comparison, the TERCOM algorithm obtains the extensive attention and research of scholars with the advantages of simple calculation, insensitivity to initial errors, strong robustness, high positioning accuracy and the like.

In the aspect of improving the TERCOM algorithm matching precision, Liu and the like provide a novel INS/TERCOM system optimization structure combining coordinate transformation, mismatching detection and Kalman filtering, and research the matching performance of a distributed and self-adaptive federal filtering information fusion algorithm; yan and the like propose a new matching algorithm by integrating TERCOM and ICCP, and obtain an initial position by using TERCOM and perform accurate positioning by using ICCP; yuan and the like use TERCOM/ICCP algorithm to fuse Kalman filtering to provide a combined underwater auxiliary navigation algorithm, and meanwhile, the precision of accurate matching adopts a sliding window to improve the algorithm efficiency; wang et al propose a rotation splicing type gravity matching algorithm based on a TERCOM algorithm; tong et al approximate a local gravity reference map with a two-dimensional gaussian basis function and solve a relevant extreme value matching model with a quasi-newton BFGS nonlinear optimization method to provide a combined matching algorithm based on local gravity map approximation, and simultaneously improve the matching accuracy of the algorithm with coarse matching of TERCOM and actual measurement data preprocessing with a difference method; zhao et al combines the TERCOM algorithm with particle filtering to provide a new terrain-aided navigation algorithm to enhance the positioning accuracy of the BITAN II algorithm; wei et al propose a correlation SITAN algorithm based on weighted decreasing iteration to solve the initial error and linear error problems, while using TERCOM for the correlation processing of the algorithm; zhang et al propose a multi-reference point joint probability mismatching online judgment criterion in a correlation plane for solving the mismatching problem that TERCOM algorithm is susceptible to elevation measurement error, terrain similarity and the like; wang et al realize the non-sonar positioning at the deepest part of the earth ocean through a TERCOM algorithm under the support of sea fighting data; zhang et al utilizes TERCOM algorithm simulation analysis to obtain the influence rule of main factors such as the speed of a submersible vehicle, the depth measurement precision, the initial position deviation, the underwater topography feature, the digital map resolution and the like on the matching precision. In the aspect of improving the TERCOM algorithm matching efficiency and reliability, Han and the like fuse a shortest path algorithm and a new correlation analysis algorithm to construct an improved TERCOM algorithm, and simultaneously, a new matching algorithm under a mismatching diagnosis method is provided through a space sequence constraint and decision criterion limit integration mechanism so as to improve the TERCOM reliability and matching precision; liu Shing and the like track the track of the submarine according to the speed and the course information output by the INS, and a TERPM positioning algorithm based on track line tracking is provided; based on a rough-fine matching strategy, Lezhaowei and the like propose a novel hierarchical neighborhood threshold search method to improve the matching efficiency of the TERCOM algorithm point-by-point traversal search; li and the like are coupled with an attitude control theory under the air-sea environment through the shortest arc principle of spherical geometry, so that a new geodesic-based method is provided to reduce the scale of a matching area and improve the matching efficiency of an algorithm; zhang et al use TERCOM as line matching algorithm to perform surface matching with geometric similarity and provide an underwater terrain matching algorithm of line-surface combination so as to improve the robustness and positioning accuracy of the algorithm.

In summary, most scholars mainly conduct research on the application of TERCOM and the improvement of navigation performance of underwater vehicles, and there is little research on changing the topological structure of TERCOM matching grids. However, the traditional TERCOM algorithm is not dependent on the position information of the starting point of the flight path, only uses 3 times of INS error at the end point of the flight path as a half-length to form a square grid matching lattice, and traverses and searches to determine the optimal matching location of the position of the underwater vehicle, but the search mechanism has large computation load and easily causes low algorithm matching efficiency; in addition, the TERCOM algorithm is difficult to effectively process observation noise and process noise and is sensitive to the angle error of the inertial navigation segment, and therefore, a design problem different from the TERRCOM matching grid topology needs to be further discussed.

Disclosure of Invention

The technical problem of the invention is solved: the method and the system for improving the underwater navigation precision based on the optimal iteration ring domain point of the grid topological structure are provided, and aim to improve the matching precision of the gravity-assisted navigation of the underwater vehicle.

In order to solve the technical problem, the invention discloses a method for improving underwater navigation precision based on a grid topological structure iteration optimal ring domain point, which comprises the following steps:

obtaining the optimal matching position of the track starting point of the underwater vehicle through a track starting point small-ring area grid matching positioning strategy;

generating lattice points to be matched in a large ring area by a track end point angle-variable three-layer ring area matching positioning strategy according to the optimal matching position of the track starting point of the underwater vehicle;

and (3) iteratively calculating the matching efficiency evaluation index of the grid points to be matched in the large ring area, and obtaining the optimal matching position of the underwater vehicle track terminal in the large ring area range according to the optimal principle so as to realize the effective matching and positioning of the underwater vehicle track terminal, further correcting the INS system control parameters and assisting in finishing the navigation target of the underwater vehicle with long voyage and long voyage distance.

In the method for improving the underwater navigation precision based on the optimal circular grid point of the grid topological structure iteration, the construction process of the track starting point small circular grid matching positioning strategy is as follows:

obtaining INS track output inertial navigation sequence (S) of a certain section of underwater vehicle navigation according to sampling time interval delta t₁,S₂,…,S_L}; where L represents the sample sequence length of the INS flight path, S₁、S₂、…、S_LRepresenting each track point in the inertial navigation sequence;

from { S₁,S₂,…,S_LExtracting to obtain position coordinates and actually measured gravity values corresponding to each track point, and constructing to obtain a position coordinate sequence { (x)₁,y₁),(x₂,y₂),…,(x_L,y_L) The measured gravity value sequence of the underwater vehicle and the g₁,g₂,…,g_L}；

Starting point S with track in inertial navigation sequence₁Position coordinates (x)₁,y₁) Centered at 3 σ₀Constructing a small ring domain as the maximum extended search boundary radius; wherein σ₀Representing the standard deviation of inertial navigation drift errors when the sampling interval is delta t;

according to the north east rotation angle theta₀And determining the total number and position coordinates of grid points to be matched in the small ring domain by using a ring radius proportional average coefficient lambda, and constructing to obtain a grid point set to be matched in the small ring domain.

In the method for improving the underwater navigation precision based on the iterative optimal ring domain point of the grid topological structure, the position coordinates of each grid point to be matched in a small ring domainThe calculation formula of (a) is as follows:

wherein the content of the first and second substances,andrespectively represents the horizontal and vertical coordinates r of the jth lattice point on the ith small ring_iDenotes the radius, β, of the ith ring in the small ring_jThe rotation angle of the jth grid point on each ring of the small ring domain is shown.

In the method for improving the underwater navigation precision based on the iterative optimal ring domain point of the grid topological structure,

r_i＝3σ₀λi

β_j＝j·θ₀

wherein i is 1,2, …, and the maximum value of iAnd the maximum value of j

In the method for improving the underwater navigation precision based on the grid topological structure iterative optimal ring area point, the optimal matching position of the track starting point of the underwater vehicle is obtained through a track starting point small ring area grid matching positioning strategy, and the method comprises the following steps:

starting the track S₁Position coordinates (x)₁,y₁) And the position coordinates of each lattice point to be matched in the small ring areaA point set to be matched is used as the true position of the starting point of the flight path;

mapping a point set to be matched of the true position of the track starting point to a gravity reference graph point by point, and taking the gravity value at the nearest gravity reference grid point as the gravity value of the point to be matched to obtain (x)₁,y₁) Corresponding theoretical gravity valueAndcorresponding theoretical gravity value

Wherein, C represents the grid resolution of the gravity reference map, mapt (·,) represents the gravity value matrix of the gravity reference map according to the grid point position, [ · ] represents rounding;

obtaining the best matching position of the track starting point of the underwater vehicle according to the principle of minimizing the absolute value of the gravity deviation

Wherein when i is 0 and j is 0,is x₁、Is y₁。

In the method for improving the underwater navigation precision based on the optimal iterative loop point of the grid topological structure, the construction process of the track end point angle-variable three-layer loop matching positioning strategy is as follows:

according to a track starting point S in an inertial navigation sequence₁Position coordinates (x)₁,y₁) And track end point S_LPosition coordinates (x)_L,y_L) Determining course information and range information of the underwater vehicle navigation:

wherein d is_INSRepresenting that the distance measurement between the start point and the end point of the inertial navigation track is described by h epsilon [0, + ∞) norm, and calculating the Euclidean distance by setting h to be 2; alpha is alpha_INSRepresenting a course arc angle taking the abscissa of the coordinate system as a positive direction;

according toAnd estimating to obtain the central position coordinate (x) of the large ring area according to the course information and the range information of the underwater vehicle navigation_O,y_O)：

With (x)_O,y_O) Centered on R_maxConstructing and obtaining an angle-variable three-layer topological structure annular grid point region covering a true end point of a flight path as a search boundary radius of the maximum extension, and recording the region as a large annular region;

taking the grid resolution C of the gravity reference graph as the span interval of each ring of the large ring area to obtain the total ring number of the large ring area

The grid resolution C and the middle ring of the gravity reference mapIs taken as a reference angle generated by each grid point in the large domainAccording to the principle of 'inner times and outer halves', determining the span angle between adjacent lattice points on the inner ring of the large ring area to beThe span angle between adjacent lattice points on the outer ring isConstructing and obtaining a large-ring domain grid point set to be matched by combining the total ring number M; wherein, the large-ring domain grid point set to be matched is a variable-angle three-ring layer grid point topological structure.

In the method for improving the underwater navigation precision based on the iterative optimal ring domain points of the grid topological structure, the generation mode of the grid points to be matched of the large ring domain is as follows:

the total number of the large-loop domain under the three mechanisms of 1 sigma-EPMP, 2 sigma-EPMP and 3 sigma-EPMP is respectively recorded asWherein, sigma represents the standard deviation of inertial navigation accumulated drift errors;

to pairRespectively corrected to obtain the total ring number M 'of the large ring domain in the three corrected mechanisms'₁、M′₂、M′₃：

Wherein ξ ═ 1,2 and 3 respectively correspond to a 1 σ -EPMP mechanism, a 2 σ -EPMP mechanism and a 3 σ -EPMP mechanism;

according to the total ring number M of the large ring domain under the three corrected mechanisms₁′、M₂′、M₃', the radius R of each ring of the macrocyclic domain under three mechanisms is obtained_1,j、R_2,j、R_3,j：

R_ξ,ζ＝ζC，ζ＝1,2,…,M′_ξ···(6)

Wherein R is_ξ,ζA radius of a zeta-th ring representing a large ring domain under a zeta-th mechanism;

according to the total ring number M 'of the large ring domain under the three corrected mechanisms'₁、M′₂、M′₃Obtaining the intermediate ring radius of the large ring domain under three mechanisms

Intermediate ring radius of large ring domain according to three mechanismsObtaining the reference angle generated by each lattice point in the large domain under three mechanisms

And (5) obtaining the lattice points to be matched of the large ring area under different mechanisms according to the steps (5) to (8).

In the method for improving the underwater navigation precision based on the iterative optimal ring domain point of the grid topological structure,

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 1 sigma-EPMP mechanismThe calculation formula of (a) is as follows:

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 2 sigma-EPMP mechanismThe calculation formula of (a) is as follows:

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 3 sigma-EPMP mechanismThe calculation formula of (a) is as follows:

in the method for improving the underwater navigation precision based on the grid topological structure iterative optimal ring area point, the method comprises the following steps of iteratively calculating the matching efficiency evaluation index of the grid points to be matched in the large ring area, and obtaining the optimal matching position of the underwater vehicle track end point in the large ring area according to the optimal principle:

determining the total number N of lattice points to be matched on an inner-middle-outer ring layer of a large ring domain under the xi mechanism_ξ；

Taking the r-th grid point to be matched of the large ring domain under the xi mechanism as the end point of the flight path to be evaluated and recording the r-th grid point as a pointWherein r ∈ {1,2, …, N_ξ}；

Will be dottedCorresponding position (x) in the gravity reference map_r,y_r) Comparing with the grid resolution C of the gravity reference diagram, and obtaining the nearest neighbor point on the gravity reference diagram according to the rounding principleGrid point base_L；

Base the grid points_LCorresponding gravity valueAs a pointAn approximation of the value of gravity;

according to the grid point base_LExtracting the position coordinates on the gravity reference map, the navigation speed and the navigation course of the underwater vehicle to obtain pointsCorresponding gravity map track sequenceAnd corresponding nearest neighbor gravity sequence

Will be provided withSequence of gravity values { g actually measured with underwater vehicle₁,g₂,…,g_LComparing, calculating the evaluation index of matching efficiency, and recording as MSD_r；

Sequentially calculating to obtain the matching efficiency evaluation indexes of all lattice points to be matched on the inner-middle-outer ring layer of the large ring area under the xi mechanism, and obtaining the matching efficiency evaluation index set and { MSD (maximum data set) of all lattice points to be matched on the inner-middle-outer ring layer of the large ring area under the xi mechanism_r|r＝1,2,…,N_ζ}；

Based on { MSD_r|r＝1,2,…,N_ζAnd (6) screening according to an optimal principle to obtain an optimal matching position of the track terminal of the underwater vehicle in the large-ring-area range

Correspondingly, the invention also discloses a system for improving the underwater navigation precision based on the optimal iterative loop domain point of the grid topological structure, which comprises the following steps:

the resolving module is used for obtaining the optimal matching position of the track starting point of the underwater vehicle through a track starting point small-ring area grid matching positioning strategy;

the generating module is used for generating lattice points to be matched in a large ring area through a track end point angle-variable three-layer ring area matching positioning strategy according to the optimal matching position of the track starting point of the underwater vehicle;

and the iteration determination module is used for iteratively calculating the matching efficiency evaluation index of the lattice points to be matched in the large ring area, and obtaining the optimal matching position of the underwater vehicle track terminal in the large ring area according to the optimal principle so as to realize the effective matching and positioning of the underwater vehicle track terminal, further correct the control parameters of the INS system and assist in finishing the long-endurance long-range navigation target of the underwater vehicle.

The invention has the following advantages:

in order to break through the limitation of the inherent grid structure of the traditional gravity matching algorithm and improve the navigation precision of underwater gravity matching, the invention provides a novel grid topological structure iterative optimal ring area point method (IOAP), which has the following principle: firstly, constructing a matching positioning strategy of a small-ring area grid of a track starting point according to the position of the inertial navigation starting point, a drift error, a rotation angle and the like, and obtaining the optimal matching positioning of the track starting point and enhancing the insensitivity of an algorithm to an initial position error through matching comparison of matching points of the small-ring area grid; secondly, constructing a track end point variable-angle three-layer ring domain matching and positioning mechanism by utilizing the optimal matching position of a track starting point and combining inertial navigation course range information, accumulated drift errors and the like to generate a ring domain matching point of a ring topology structure; and finally, iteratively calculating the matching indexes of the loop matching points and obtaining the optimal matching position of the track end point in the loop range according to the optimal principle.

The matching performance difference and the good robustness of the method under different inertial navigation accumulated error multiples or reference angle ring radiuses are verified by comprehensively considering the matching precision statistical index, the average matching time, the matching success rate and the like as the analysis basis of the matching quality.

Therefore, the gravity matching test comparison is carried out on the tracks of which the starting points and the end points of different areas are located in different gravity intervals, and the following results are proved: the method has the advantages of high matching precision, strong positioning applicability of different gravity sections and the like, and the average matching precision and the worst matching precision of the method are respectively improved by 40.39 percent and 72.16 percent compared with the TERCOM algorithm to the maximum.

Drawings

FIG. 1 is a flowchart illustrating steps of a method for improving underwater navigation accuracy based on a mesh topology iterative optimal ring domain point according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of distribution of to-be-matched points in a small ring domain based on an SPMP strategy in the embodiment of the present invention;

FIG. 3 is a schematic diagram of distribution of points to be matched in a large ring domain based on an EPMP strategy in the embodiment of the present invention;

FIG. 4 is a schematic diagram of gravity anomaly distribution in a research area satellite remote sensing and local amplification area in an embodiment of the present invention; wherein, 4(a) is a satellite remote sensing image, and 4(b) is a gravity anomaly reference image;

FIG. 5 is a schematic diagram illustrating a comparison of matching test effects of a gravity matching algorithm under different sigma criteria in an embodiment of the present invention; wherein, 5(a) is TERCOM algorithm, 5(b) is 1 sigma-IOAP algorithm, 5(c) is 2 sigma-IOAP algorithm, and 5(d) is 3 sigma-IOAP algorithm;

FIG. 6 is a histogram comparing probability of successful matching for 4 algorithms at different positioning accuracies according to an embodiment of the present invention;

FIG. 7 is a schematic diagram illustrating the comparison between a TERCOM algorithm matching position and a real position and the classification of grid points thereof in the embodiment of the present invention; wherein, 7(a) is the TERCOM algorithm 100 times of tests, and 7(b) is the TERCOM algorithm matching position point classification;

FIG. 8 is a diagram illustrating a comparison between a matching location and a true location for a different sigma-IOAP algorithm according to an embodiment of the present invention; wherein 8(a) is 100 tests of 1 sigma-IOAP algorithm, 8(b) is 100 tests of 2 sigma-IOAP algorithm, and 8(c) is 100 tests of 3 sigma-IOAP algorithm;

FIG. 9 is a schematic diagram illustrating a comparison of matching effects of an IOAP algorithm under different ring radius reference angles according to an embodiment of the present invention; wherein, 9(a) is TERCOM algorithm, 9(b) is 1-IOAP algorithm, 9(c) is 1.5-IOAP algorithm, 9(d) is 2-IOAP algorithm, and 9(e) is 2.5-IOAP algorithm;

FIG. 10 is a histogram comparing the matching success probability of the IOAP algorithm at different ring radius reference angles according to an embodiment of the present invention;

FIG. 11 is a schematic diagram illustrating comparison of algorithm matching positioning effects at the start points of different tracks according to an embodiment of the present invention; wherein 11(a) is a TERCOM algorithm (track starting point A), 11(B) is a TERCOM algorithm (track starting point B), 11(C) is a TERCOM algorithm (track starting point C), 11(d) is a 1.5-IOAP algorithm (track starting point A), 11(e) is a 1.5-IOAP algorithm (track starting point B), and 11(f) is a 1.5-IOAP algorithm (track starting point C).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The invention provides a method for improving underwater navigation precision based on a grid topological structure iteration optimal ring domain point, which is called IOAP algorithm for short, based on the structural layout of a TERCOM algorithm matching lattice and the drift error characteristic of an INS system, and the realization principle is as follows: in order to reduce the sensitivity of the IOAP algorithm to initial errors, a small loop matching grid point is formed by stretching a certain drift error and a certain rotation angle by taking the inertial navigation starting point position as the center, a track starting point small loop matching positioning strategy of an annular topological structure is constructed, and the optimal starting point matching position is obtained according to the principle of minimizing the absolute value of gravity deviation; according to the optimal matching position of a track starting point, obtaining the central position of a large-ring matching grid by combining inertial navigation course range information, determining the ring number of the large-ring matching grid based on inertial navigation accumulated drift error and the like, obtaining a topological structure of matching grid point annular distribution according to a grid point reference deflection angle of a middle ring radius and an 'inner-multiple outer-half' principle, constructing a matching positioning strategy of a track end point variable-angle three-layer ring, extracting a gravity graph sequence through grid points, calculating mean square error between the gravity graph sequence and an actually measured gravity sequence, matching and comparing, and obtaining the optimal matching position of the track end point according to the mean square error minimization principle.

As shown in fig. 1, in this embodiment, the method for improving underwater navigation accuracy based on a mesh topology iterative optimal ring domain point includes:

and 101, obtaining the optimal matching position of the track starting point of the underwater vehicle through a track starting point small-ring area grid matching positioning strategy.

In this embodiment, in consideration of the problem of relative sensitivity of gravity Matching algorithms such as SITAN and ICCP to the initial error, and in order to improve insensitivity (robustness) of the IOAP algorithm to the initial error of gravity Matching to a certain extent, a track Starting Point small-ring domain grid Matching Positioning strategy/mechanism (SPMP) is constructed. The SPMP strategy is characterized in that the position of the inertial navigation indicated underwater vehicle is used as the center, a small annular topological structure grid point region (marked as a small annular region) to be matched, which covers the real starting point position of the flight path according to probability, is formed by stretching a certain drift error and a certain rotation angle, and the optimal matching position of the starting point of the flight path is determined by the optimal principle that the gravity of the point to be matched matches with the evaluation index.

Preferably, the construction process of the track starting point small ring area grid matching positioning strategy may be as follows:

obtaining INS track output inertial navigation sequence (S) of a certain section of underwater vehicle navigation according to sampling time interval delta t₁,S₂,…,S_L}; from { S₁,S₂,…,S_LExtracting to obtain position coordinates and actually measured gravity values corresponding to each track point, and constructing to obtain a position coordinate sequence { (x)₁,y₁),(x₂,y₂),…,(x_L,y_L) The measured gravity value sequence of the underwater vehicle and the g₁,g₂,…,g_L}. Where L represents the sample sequence length of the INS flight path, S₁、S₂、…、S_LRepresenting track points in the inertial navigation sequence.

Then, under the SPMP strategy, the track starting point S in the inertial navigation sequence is used₁Position coordinates (x)₁,y₁) Centered at 3 σ₀The ringlet domain is determined as the search boundary radius of maximum extent. Further, according to the rotation angle theta of north and east₀And a ring radius proportion average coefficient lambda can determine the total number and position coordinates of grid points to be matched in the small ring domain, and further construct and obtain a grid point set to be matched in the small ring domain. Wherein σ₀And represents the standard deviation of inertial navigation drift error at a sampling interval Δ t. For example, when theta₀When λ is 1/3 and 45, the distribution of the small ring domain to-be-matched grid point set spanned by the SPMP strategy is as shown in fig. 2.

Furthermore, according to the setting condition of the parameter, the position coordinates of each lattice point to be matched in the small ring area can be obtainedThe calculation formula of (a) is as follows:

wherein the content of the first and second substances,andrespectively representing the horizontal and vertical coordinates of the jth lattice point on the ith small ring; r is_iDenotes the radius, r, of the ith ring in the small ring domain_i＝3σ₀λi；β_jRepresents the rotation angle, beta, of the jth lattice point on each ring of the small ring domain_j＝j·θ₀(ii) a i is 1,2, …, and the maximum value of iAnd the maximum value of j

The process of determining the best match position for the launch point of the underwater vehicle track may then be as follows:

starting the track S₁Position coordinates (x)₁,y₁) And the position coordinates of each lattice point to be matched in the small ring areaA point set to be matched is used as the true position of the starting point of the flight path; mapping a point set to be matched of the true position of the track starting point to a gravity reference graph point by point, and taking the gravity value at the nearest gravity reference grid point as the gravity value of the point to be matched to obtain (x)₁,y₁) Corresponding theoretical gravity valueAndcorresponding theoretical gravity value

In order to determine the optimal matching position of the track starting point of the underwater vehicle, the optimal matching position of the track starting point of the underwater vehicle can be obtained according to the principle of minimizing the absolute value of gravity deviation

Wherein C represents the grid resolution of the gravity reference map, and mapt (·) represents a gravity value matrix of the gravity reference map by grid point position [ ·]Means rounding off and rounding; when i is 0 and j is 0,is x₁、Is y₁。

It should be noted that a multi-modal phenomenon may occur when the gravity reference map mapping is performed on the small-range multi-grid points, and the embodiment matches the small-range multi-grid points according to the first grid point with the minimum absolute value of gravity deviation, and certainly, the optimal matching of the track starting point may also be obtained according to a random selection mechanism, which is not limited in this embodiment.

Therefore, the SPMP strategy can realize effective matching positioning of the track starting point of the underwater vehicle according to the probability, weaken the sensitivity of the IOAP algorithm to the initial error, and provide the position information basis of the track starting point for the next step of track end point position matching positioning guided by the inertial navigation course range information.

And 102, generating grid points to be matched in a large ring area through a track end point angle-variable three-layer ring area matching positioning strategy according to the optimal matching position of the track starting point of the underwater vehicle.

In this embodiment, considering that the inertial navigation track sequence contains better short-time high-precision course and range information, the optimal matching position of the track starting point obtained by combining the SPMP strategyThe central position O of the domain to be matched of the track end point can be further obtained; then, based on the drift error statistical characteristic of the inertial navigation system, a new topological structure with grid points to be matched in an annular distribution and a Matching Positioning strategy (a track end Point variable-angle three-layer ring area Matching Positioning strategy/mechanism, Matching Positioning mechanism of the tracking Ending Point in three-layer ring area, EPMP) are constructed, and the EPMP strategy obtains the maximum ring number of an annular covering area and the deflection angle among the points of a Matching grid according to the relative relationship among the inertial navigation accumulated drift error standard deviation sigma, the grid resolution C of a gravity reference graph and the radius of an intermediate ring, and expands a large variable-angle three-layer topological structure annular Point area to be matched, which covers the real end Point position of the track according to the probability, and is marked as a large ring area grid; and extracting a gravity map sequence of the matched flight path according to the coordinate position of each grid point, comparing the gravity map sequence with the real gravity sequence of the underwater vehicle, and determining the optimal matching position of the flight path end point according to the optimal principle of the evaluation index.

Preferably, the construction process of the track end variable-angle three-layer circular domain matching positioning strategy can be as follows:

according to a track starting point S in an inertial navigation sequence₁Position coordinates (x)₁,y₁) And track end point S_LPosition coordinates (x)_L,y_L) Determining course information and range information of the underwater vehicle navigation:

wherein d is_INSRepresenting that the distance measurement between the start point and the end point of the inertial navigation track is described by h epsilon [0, + ∞) norm, and calculating the Euclidean distance by setting h to be 2; alpha is alpha_INSIndicating a heading arc angle with the abscissa of the coordinate system as the positive direction.

Then, according toAnd estimating to obtain the central position coordinate (x) of the large ring area according to the course information and the range information of the underwater vehicle navigation_O,y_O)：

Then, under EPMP strategy, with (x)_O,y_O) Centered on R_maxAnd constructing and obtaining an angle-variable three-layer topological structure annular grid point region covering the true end point of the flight path as the maximum extension search boundary radius, and recording the region as a large annular region. Meanwhile, the grid resolution C of the gravity reference graph is used as the span interval of each ring of the large ring area to obtain the total ring number of the large ring area

On the basis, the deflection angle between adjacent grid points on each ring of the large ring domain is given, and a grid point set to be matched can be formed by stretching. If the same mode as the SPMP strategy is selected to determine the deflection angle between adjacent lattice points on each ring of the large ring domain, and the equal deflection angles of the large ring domain will keep the lattice points of each ring in equal amount, the lattice network formed by the SPMP strategy will have the phenomenon of "dense inside and sparse outside", that is, the interval between the lattice points on the inner layer is too small, and the interval between the lattice points on the outer side is too large. Therefore, for the large ring domain, the embodiment of the present invention provides a novel way of determining the deflection angle between adjacent grid points, that is, a variable-angle three-ring grid point topology structure: grid resolution C and intermediate ring based on gravity reference diagramIs taken as a reference angle generated by each grid point in the large domainDetermining the inner ring of the large ring area according to the principle of' inner times and outer halvesThe span angle between adjacent grid points isThe span angle between adjacent lattice points on the outer ring isAnd combining the total ring number M to construct and obtain a large ring domain grid point set to be matched, wherein the large ring domain grid point set is a variable-angle three-ring layer grid point topological structure. For example, whenWhen M is 9, the distribution of the large ring domain to-be-matched grid point set spanned by the EPMP strategy is as shown in fig. 3.

In this embodiment, in consideration of good applicability of normal distribution to any system error and 99.73% high probability coverage characteristic of the 3 σ criterion under natural conditions, and in order to subsequently test differences in underwater gravity matching performance of the EPMP strategy under the principles of different σ (σ represents standard deviation of inertial navigation cumulative drift error), three IOAP algorithms based on 1 σ -EPMP, 2 σ -EPMP, and 3 σ -EPMP mechanisms are respectively constructed according to different σ principles, which are abbreviated as 1 σ -IOAP, 2 σ -IOAP, and 3 σ -IOAP. Wherein xi ═ 1,2 and 3 are adopted to represent three mechanisms of 1 σ -EPMP, 2 σ -EPMP and 3 σ -EPMP, i.e., xi ═ 1 is adopted to represent a 1 σ -EPMP mechanism; ξ ═ 2, representing the 2 σ -EPMP mechanism; ξ ═ 3, represents the 3 σ -EPMP mechanism.

The EPMP policy can be constructed in a new way as follows:

the total number of the large-loop domain under the three mechanisms of 1 sigma-EPMP, 2 sigma-EPMP and 3 sigma-EPMP is respectively recorded as

Considering that the total number of large ring domains is not necessarily 3 times under different sigma principles, and simultaneously, in order to further enhance the good coverage effect of large ring domain lattices of the EPMP strategy on the real position of the underwater vehicle, the following formula can be used for realizing the coverage of the large ring domain lattices on the real position of the underwater vehicleRespectively correcting to obtain three corrected productsTotal ring number M of large ring domain under mechanism₁′、M₂′、M₃', to facilitate subsequent partitioning of the inner, middle and outer tricyclic layers of the macrocyclic domain:

then, according to the total ring number M of the large ring domain under the three corrected mechanisms₁′、M₂′、M₃', the radius R of each ring of the large ring domain under three mechanisms can be obtained_1,j、R_2,j、R_3,jAnd the intermediate ring radius of the large ring domain under three mechanisms

R_ξ,ζ＝ζC，ζ＝1,2,…,M′_ξ···(6)

Wherein R is_ξ,ζDenotes the radius of the zeta-th ring of the large ring domain under the zeta-th mechanism.

Furthermore, the reference angle generated by each lattice point in the large domain under three mechanisms can be obtained

And finally, obtaining the lattice points to be matched in the large ring area under different mechanisms according to the steps (5) to (8). The calculation formula of the lattice points to be matched in the large ring area under each mechanism is as follows:

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 1 sigma-EPMP mechanismThe calculation formula of (A) is as follows:

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 2 sigma-EPMP mechanismThe calculation formula of (A) is as follows:

position coordinates of lattice points to be matched on inner-middle-outer ring layer of large ring domain under 3 sigma-EPMP mechanismThe calculation formula of (a) is:

and 103, iteratively calculating the matching efficiency evaluation index of the grid points to be matched in the large ring area, and obtaining the optimal matching position of the track terminal of the underwater vehicle in the large ring area according to the optimal principle so as to realize the effective matching and positioning of the track terminal of the underwater vehicle, further correcting the control parameters of the INS system and assisting in finishing the long-endurance long-range navigation target of the underwater vehicle.

In this embodiment, in consideration of the higher accuracy of the gravity value at the grid resolution in the gravity reference map, the gravity value calculated by the interpolation method may not truly reflect the actual gravity at the matching point, so a matching process similar to the conventional tricom algorithm may be adopted to determine the optimal matching location of the end point of the centralized underwater vehicle at the point to be matched in the EPMP large-loop region.

Preferably, a feasible method for iteratively calculating the matching efficiency evaluation index of the grid points to be matched in the large ring area and obtaining the optimal matching position of the track end point of the underwater vehicle in the large ring area according to the optimal principle is as follows:

determining the total number N of lattice points to be matched on an inner-middle-outer ring layer of a large ring domain under the xi mechanism_ξ。

Making the r (r epsilon {1,2, …, N) of large loop domain under the xi mechanism_ξ) } lattice points to be matched are taken as the end points of the flight path to be evaluated and recorded as pointsWill be dottedCorresponding position (x) in the gravity reference map_r,y_r) Comparing with the grid resolution C of the gravity reference diagram, and obtaining the nearest neighbor point on the gravity reference diagram according to the rounding principleGrid point base_L. Base the grid points_LCorresponding gravity valueAs a pointAn approximation of the value of gravity; according to the grid point base_LExtracting the position coordinates on the gravity reference map, the navigation speed and the navigation course of the underwater vehicle to obtain pointsCorresponding gravity map track sequenceAnd corresponding nearest neighbor gravity sequenceWill be provided withMeasured with underwater vehiclesGravity value series g₁,g₂,…,g_LComparing, calculating the evaluation index of matching efficiency, and recording as MSD_r. It should be noted that, when calculating the matching performance evaluation index, any appropriate performance evaluation index may be selected for calculation and matching, and the mean square error MSD is taken as an example in this embodiment.

According to the calculation process of the r & ltth & gt lattice point to be matched, the matching efficiency evaluation indexes of all lattice points to be matched on the inner-middle-outer ring layer of the large ring area under the xi mechanism can be sequentially calculated, and the matching efficiency evaluation index set { MSD (maximum digital resolution) of all lattice points to be matched on the inner-middle-outer ring layer of the large ring area under the xi mechanism is obtained_r|r＝1,2,…,N_ζ}。

Finally, based on { MSD_r|r＝1,2,…,N_ζAnd (6) screening according to an optimal principle to obtain an optimal matching position of the track terminal of the underwater vehicle in the large-ring-area range

In conclusion, through the steps 101 to 103, the effective matching and positioning of the underwater vehicle terminal point are realized, and the obtained optimal matching position of the underwater vehicle track terminal point is used as the underwater vehicle track terminal point to correct the INS system control parameters and assist in completing the navigation target of the underwater vehicle with long voyage time and long voyage distance.

On the basis of the above embodiment, the method for improving the underwater navigation accuracy based on the grid topology iterative optimal ring region point described in the above embodiment is verified below.

In order to verify the effectiveness and superiority of the IOAP algorithm in the underwater vehicle gravity navigation application, 3 groups of tests are designed in total:

testing 1, verifying the matching performance difference of the IOAP algorithm under different sigma criteria;

testing 2, verifying different influences of the reference angles under different ring radii on the matching performance of the algorithm;

and 3, verifying the good applicability of the IOAP algorithm to underwater gravity matching navigation by using track starting points of different areas.

Example data was derived from the website of san Diego school, California university (http:// topex. ucsd. edu /), gravity anomaly data with a resolution of 1 '× 1'. As shown in FIG. 4(a), the invention selects the gravity anomaly data of the south China sea area for research, and the longitude and latitude range of the data is (longitude 113 degrees E-115 degrees E, latitude 10 degrees N-12 degrees N). The gravity anomaly reference data is converted into grid resolution gravity data of 100m multiplied by 100m by a bilinear interpolation method, as shown in fig. 4(b), the maximum value of the gravity anomaly of the region is 130.57mGal, the minimum value is-33.53 mGal, and the average value is 15.43 mGal.

(1) Matching performance difference verification of IOAP algorithm under different sigma criteria

The resolution of the gravity abnormal grid in the simulation sample block is 100m multiplied by 100m, and the accelerometer constant value is zero offset by 10^-3m/s²(the inertial navigation root mean square error follows normal distribution) and the navigational speed is 10m/s¹70 degrees north of course, 0m of initial position error and 0.04m/s of speed error¹The course error is 0.05 degrees, the real-time measurement data of the gravimeter is random noise with the standard deviation of 1mGal superposed on the sampling value of the real track in the gravity anomaly database, the number of the sampling points is 110, and the sampling period is 20 s. Wherein, the invention defines the matching positioning precision as l, and the difference between the absolute values of the matching position and the real position is in the closed interval [0, l]The effective matching is achieved, so that the effective matching times N of the algorithm under N times of experimental tests and the matching success rate of the algorithm can be obtainedAnd simultaneously recording the average value (mean), standard deviation (std) and worst value (max) of the matching and positioning accuracy of N times of tests and the track average matching time T (without environment configuration time) as a performance evaluation index of the gravity matching algorithm.

In order to test and analyze the application performance of the IOAP algorithm with different sigma criteria in the gravity matching navigation of the underwater vehicle, 100 independent experiments are carried out by using the 1 sigma-IOAP, 2 sigma-IOAP and 3 sigma-IOAP algorithms, meanwhile, the TERCOM algorithm is used as a comparison algorithm, and the grid point coordinates (1400 and 1500) of the gravity reference graph are used as the simulation starting points of the navigation of the underwater vehicle, so that the comparison effect of the visual matching positioning precision is shown in FIG. 5.

Under the action of different sigma, the matching and positioning performance of the IOAP algorithm is different, and the matching effect of the 3 sigma-IOAP algorithm is the most excellent and is obviously superior to that of the traditional TERCOM algorithm. On the T index, the 1 sigma-IOAP algorithm has poor matching effect although the average running time is minimum, and is difficult to be effectively applied to navigation of an actual underwater vehicle; the average running time of the 2 sigma-IOAP algorithm is about half of that of the TERCOM algorithm, the average matching precision is less than 1 grid resolution, and the matching probability is better than that of the TERCOM algorithm (88% > 82%) under the condition that the positioning precision l is 100, which shows that the 2 sigma-IOAP algorithm has certain practical navigation application value under the dual-target condition of matching efficiency and matching precision, and the gravity navigation mechanism can be selected properly according to the practical navigation requirement; the difference between the 3 sigma-IOAP algorithm and the T index of TERCOM is not large, and the indexes of mean value, std value and max value of matching precision, matching success probability and the like are superior to most index values of TERCOM algorithm and other algorithms, so that the better matching performance and good potential practical value of the provided IOAP algorithm in gravity-assisted navigation of an underwater vehicle are fully shown.

For further analysis of the difference of successful matching effects of 4 algorithms under the constraint conditions of different positioning accuracy L, L is respectively 20, 40, 60, 80, 100 andunder the constraint of (3), a histogram of the comparison result of the successful matching probability of 100 tests is obtained, as shown in fig. 6.

The successful matching probability difference of different sigma-IOAP algorithms under the constraint of different positioning accuracy is obvious, and when l is less than or equal to 40, 3 sigma-IOAP algorithms have a certain number of successful matching but TERCOM matching fails; comprehensively analyzing the successful matching probability of the algorithm under different positioning accuracy l, and performing the matching performance of the 3 sigma-IOAP algorithm to be the best and 2 sigma-IOAP to be superior to the traditional TERCOM algorithm, but the 1 sigma-IOAP algorithm is weaker than the TERCOM algorithm under the constraint of the positioning accuracy; fig. 6 further intuitively shows the excellent successful matching performance of the 3 σ -IOAP algorithm, and the above conclusion still effectively verifies the excellent performance of the proposed 3 σ -IOAP algorithm in the underwater gravity matching navigation.

To further explore and analyze the reason why the 3 σ -IOAP algorithm is superior to TERCOM and other σ -IOAP algorithms in matching efficiency and accuracy, a scatter-to-contrast diagram of the TERCOM algorithm matching position and the actual position of the underwater vehicle is drawn as shown in fig. 7 (the inertial navigation position is used as the origin of image coordinates to ensure that 100 test results can be drawn in the same image).

As can be seen from the analysis in fig. 7(a), the actual positions of the underwater vehicle tested by the tricom algorithm 100 times are almost all within the 3 sigma error grid range of the inertial navigation position (the solid line frame outside the dashed circle in fig. 7 (a)), while all the position points are also almost located inside the 3 sigma ring boundary dotted line centered on the inertial navigation position (dotted line circle of inscribed solid line box in fig. 7 (a)), that is, it indicates to some extent that there is a certain amount of small probability matched points in the rectangular grid of the TERCOM algorithm, see the points between the solid line box and the dashed line circle in FIG. 7(b), namely, although the probability of matching the points outside the 3 sigma circular ring is small, the matching efficiency of TERCOM is obviously influenced, therefore, the gravity matching algorithm for deleting the matching points outside the 3 sigma ring domain can effectively improve the matching efficiency of the algorithm without influencing the matching precision of the algorithm obviously, the feasibility and the effectiveness of the lattice point matching mechanism designed based on the ring domain topology structure are also effectively demonstrated from the side.

To further analyze the reason why the 3 σ -IOAP algorithm is superior to other σ -IOAP matching accuracy, a graph plotting the matching effect of 100 tests of different σ -IOAP algorithms is shown in fig. 8. From the analysis of fig. 8, it can be known that the coverage matching effect of the IOAP algorithm based on different sigma-ring domains on the real position of the underwater vehicle is different: the 3 sigma-IOAP algorithm realizes high-precision matching positioning of the underwater vehicle by large-ring-domain lattice point coverage; the 2 sigma-IOAP and the 1 sigma-IOAP only realize good matching of real positions in a large domain, but the optimal matching of the real positions outside the domain is often only scattered on a boundary ring of the domain, and a better matching position is difficult to find, so that the matching precision of the algorithm is influenced, the difference of successful matching probabilities of different sigma-IOAP algorithms and the good matching precision of the 3 sigma-IOAP algorithm are explained to a certain extent, and the important potential application value of the 3 sigma-IOAP algorithm in underwater vehicle gravity matching navigation is shown.

(2) Influence difference verification of IOAP algorithm matching performance under different ring radius reference angles

Reference angles determined for further exploration based on different ring radii RThe influence effect on the matching performance of the 3 sigma-IOAP algorithm is respectively calculated according to the maximum ring radius R of the inner ring layer of the 3 sigma-IOAP algorithm¹＝R_M/3Intermediate ring radius of 'inner middle' ring layerMaximum ring radius R of intermediate ring layer²＝R_2M/3Middle ring radius of 'middle and outer' ring layerTo determine a reference angle of the 3 sigma-IOAP algorithmAnd a variable-angle three-ring layer lattice point set to be matched is formed, and corresponding algorithms are respectively marked as 1-IOAP, 1.5-IOAP (namely 3 sigma-IOAP of section 2.1), 2-IOAP and 2.5-IOAP algorithms. According to the analysis of the formula (6), the larger the ring radius R is, the larger the large ring reference angle of the 3 sigma-IOAP algorithm isThe smaller the grid points to be matched are, the more the total number N of the generated grid points to be matched is, so that the 1-IOAP algorithm has the fastest matching efficiency and the 2.5-IOAP algorithm has the slowest execution theoretically.

The parameter settings such as the simulated sample block, the track starting point grid coordinates and the like are the same as those in the above (1), and the algorithm matching positioning statistical results of 100 independent tests are respectively shown in fig. 9 and fig. 10. The matching precision and success probability of the 3 sigma-IOAP algorithm almost show the characteristic of improved matching effect along with the increase of the ring radius R of the reference angle, and the matching effect of the 1-IOAP algorithm is relatively poor but still superior to the TERCTOM algorithm on 6/7 indexes by using the optimal performance of the 2.5-IOAP and the second order of the 2-IOAP, which shows that the reference angles based on different ring radii can influence the matching performance of the 3 sigma-IOAP algorithm; according to T index analysis, the IOAP algorithm of different ring radius reference angles shows a phenomenon of 'matching efficiency reduction' along with the increase of the ring radius R, and the result is consistent with a theoretical analysis conclusion, which shows that the total amount of grid points to be matched corresponding to the different ring radius reference angles is different and causes the difference of the matching efficiency of the algorithm. Therefore, in the practical underwater vehicle navigation application, the 3 sigma-IOAP algorithm corresponding to the appropriate ring radius R can be selected in a proper manner according to the specific matching target requirement, and a specific navigation matching task is completed, so that the 3 sigma-IOAP algorithm provided by the invention has higher algorithm robustness and good application value in the underwater gravity matching navigation.

The matching precision and the matching success probability under different scales of the 2.5-IOAP algorithm are almost superior to those of other IOAP algorithms and TERCOM algorithms, but the matching T index value is the highest and is almost 2 times of the TERCOM matching time, so that the 2.5-IOAP algorithm is not lost as the optimal selection of the gravity matching algorithm under the underwater navigation situation that the matching efficiency requirement is not high and the matching precision is more important; under the condition of dual-target requirements on matching efficiency and matching accuracy, the 1-IOAP algorithm is the best choice of the gravity matching algorithm, so that the 3 sigma-IOAP algorithm is further proved to have better underwater gravity matching navigation robustness. In addition, the 1.5-IOAP algorithm (namely the 3 sigma-IOAP algorithm of section 2.1) shows a better compromise effect between matching efficiency and matching precision, and meanwhile, considering that the matching efficiency of the algorithm is not greatly different from that of the TERCOM algorithm, the following sections are further tested according to the 1.5-IOAP algorithm to verify the good matching performance of the algorithm at different starting points.

(3) Good matching performance verification of IOAP algorithm at starting point of tracks in different areas

To further verify the good matching applicability of the 1.5-IOAP algorithm in underwater vehicle matching navigation, the present invention uses the area grid coordinates A (1660, 1410), B (1550, 740) and C (1400, 350) as the positions of the track start points of the underwater vehicle, respectively. On the premise that the matching efficiency (T index) is not large, the 1.5-IOAP algorithm is obviously superior to the traditional TERCOM algorithm in 4 indexes such as average matching precision (mean), standard deviation of matching precision (std) and worst matching precision (max); compared with TERCOM, the worst matching precision of 1.5-IOAP under 3 situations is respectively and relatively improved by 47.24%, 63.96% and 72.16%, and the average matching precision is relatively improved by 20.37%, 40.39% and 13.88%, which shows that the IOAP algorithm provided by the invention has higher matching precision and good synchronous optimization performance of multiple tests; meanwhile, under different successful matching scales l, compared with a TERCOM algorithm, the algorithm of the invention shows relatively more excellent matching success probability, particularly when the matching precision is less than 40, the successful matching of the underwater vehicle position is realized by the 1.5-IOAP algorithm with a certain probability, and the good matching applicability of the IOAP algorithm to underwater gravity matching navigation under the conditions of different area starting points is effectively verified.

In order to visually show the matching effect difference between the 1.5-IOAP algorithm and the TERCOM algorithm at 3 test positions, a worst matching positioning comparison schematic in 100 tests is drawn, as shown in fig. 11. As can be seen from fig. 11, in the underwater gravity matching positioning at the starting point of the track in different areas, the 1.5-IOAP algorithm has higher matching positioning accuracy compared with the TERCOM algorithm, and meanwhile, the 3 track end points fall in different gravity sections, so that the improved IOAP algorithm has better matching adaptability in different gravity sections to a certain extent, and the effectiveness and reliability of the iterative optimal ring-point algorithm based on the novel grid topology structure in improving the gravity matching accuracy of the underwater vehicle are further effectively verified.

On the basis of the embodiment, the invention also discloses a system for improving the underwater navigation precision based on the optimal iteration ring domain point of the grid topological structure, which comprises the following steps: the resolving module is used for obtaining the optimal matching position of the track starting point of the underwater vehicle through a track starting point small-ring area grid matching positioning strategy; the generating module is used for generating lattice points to be matched in a large ring area through a track end point angle-variable three-layer ring area matching positioning strategy according to the optimal matching position of the track starting point of the underwater vehicle; and the iteration determination module is used for iteratively calculating the matching efficiency evaluation index of the lattice points to be matched in the large ring area, and obtaining the optimal matching position of the underwater vehicle track terminal in the large ring area according to the optimal principle so as to realize the effective matching and positioning of the underwater vehicle track terminal, further correct the control parameters of the INS system and assist in finishing the long-endurance long-range navigation target of the underwater vehicle.

For the system embodiment, since it corresponds to the method embodiment, the description is relatively simple, and for the relevant points, refer to the description of the method embodiment section.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.

Those skilled in the art will appreciate that the invention may be practiced without these specific details.