Aircraft navigation positioning method and system

Abstract

The invention discloses an aircraft navigation positioning method and system, and belongs to the technical field of terrain-aided navigation. The method comprises the following steps: firstly, determining a candidate position coordinate set which may be a real position coordinate of an aircraft by using real nearest echo distances at a plurality of acquisition points and geographic information in a radar beam coverage range, and combining the candidate position coordinate set into a candidate flight trajectory which may be a real flight trajectory of the aircraft; finally, real shape information carried by the theoretical flight trajectory is fully utilized, trajectory matching is conducted on the candidate flight trajectories and the theoretical flight trajectory, a real flight trajectory is found out from the candidate flight trajectories, then the real position coordinates of the aircraft are determined, and accurate navigation and positioning can be achieved during terrain-aided navigation. The horizontal positioning precision is within 6 meters, the elevation positioning precision is within 2.5 meters, and compared with the horizontal positioning precision of 10-100 meters and the elevation positioning precision of 5-15 meters of an existing terrain matching aided navigation positioning method, the navigation positioning precision is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of terrain-assisted navigation, and more specifically, relates to an aircraft navigation and positioning method and system. Background Art

[0002] For aircraft with cruise missions, long-term or long-distance flights cause the INS (Inertial Navigation System) to accumulate positioning errors, resulting in a continuous decrease in navigation accuracy. Due to the fragility of GNSS (Global Navigation Satellite System) signals, GNSS signals are subject to denial, intentional or unintentional interference or deception, making it impossible to achieve the purpose of navigation and positioning through external channels. In view of this application background, the existing technology often uses terrain matching assisted navigation technology, which is an assisted navigation technology that uses the terrain and geographic information below the aircraft to correct the horizontal disturbance drift error of INS. Among them, the traditional terrain matching assisted navigation and positioning methods include: TERCOM (Terrain Contour Matching), SITAN (Sandia Terrain Aided Navigation), TERPROM (Terrain Profile Matching), PTAN (Precision Terrain Aided Navigation System), and their positioning accuracy is: horizontal positioning accuracy of 30-100 meters, and elevation positioning accuracy of 5-15 meters. The current more accurate terrain matching assisted navigation and positioning methods, such as the inertial navigation-terrain matching-satellite composite guidance method, have a horizontal positioning accuracy of only 10 meters and an elevation positioning accuracy of only 5 meters. Through analysis, it is found that the above-mentioned terrain-assisted navigation technology needs to use the measured terrain elevation curve of the terrain matching area to match the geographic elevation information stored in the aircraft to correct the accumulated error of the disturbance drift of the aircraft's horizontal position. However, in the terrain matching process, the distance of the nearest echo measured by the radio altimeter is accurate, but calculating the distance of the nearest echo as the height above the ground is inaccurate, resulting in an inaccurate terrain elevation curve and ultimately inaccurate positioning accuracy. Summary of the invention

[0003] In view of the above defects or improvement needs of the prior art, the present invention provides an aircraft navigation and positioning method and system to solve the technical problem that the prior art cannot achieve accurate navigation and positioning during terrain-assisted navigation.

[0004] In order to achieve the above-mentioned object, in a first aspect, the present invention provides an aircraft navigation and positioning method, comprising:

[0005] S1. When the aircraft flies at a fixed altitude above a certain terrain area, a theoretical flight trajectory of the aircraft is intercepted from the flight record; the flight trajectory includes: M collection points collected in chronological order; the information on the i-th collection point includes: the actual closest echo distance L of the aircraft at the i-th collection point i and theoretical position coordinates (X i * ,Y i * ,H); where i=1,2,…,M,M≥2; H is a height value selected from [H0-σH0,H0+σH0]; H0 is the measured height of the pressure altimeter on the aircraft; 0<σ<1;

[0006] S2: Sampling the position coordinates in the local area of ​​the i-th acquisition point to obtain N candidate position coordinates (X ij ,Y ij ,H), j=1,2,…,N,N≥2, thereby forming a candidate position coordinate set at the position of the i-th collection point; any position coordinate point in the local area is the same as the theoretical height H of the i-th collection point, and the distance between the two is less than or equal to the preset distance;

[0007] S3, in (X ij ,Y ij ,H) to obtain the coordinates within the ground coverage area corresponding to K i The terrain position coordinates (X ijk ,Y ijk ,Z ijk ), k=1,2,…,K i , K i ≥2; where the ground coverage is from (X ij ,Y ij ,H) the coverage of the radar beam emitted downward from the position on the terrain area; Z ijk =S(X ijk ,Y ijk ); S(·) is the terrain surface fitting function of the terrain area;

[0008] S4, calculate (X ij ,Y ij ,H) and the distance between each terrain position coordinate, and the minimum distance is taken as the nearest echo distance L ij ;

[0009] S5. Determine L ij With L i Is the absolute value of the difference less than or equal to the preset value L sIf so, then keep the (X ij ,Y ij ,H), otherwise, delete the (X ij ,Y ij ,H), thereby realizing the screening of candidate position coordinate sets;

[0010] S6. After the screening is completed, all candidate flight trajectories of the aircraft are obtained; the candidate flight trajectories are obtained by sorting a candidate position selected from the candidate position coordinate set at each collection point position according to the order of the collection points;

[0011] S7. Match each candidate flight trajectory with the theoretical flight trajectory respectively, retain the successfully matched candidate flight trajectory, and use the candidate flight trajectory with the smallest absolute value of the difference between the shape feature of the theoretical flight trajectory as the actual flight trajectory of the aircraft, and the candidate position coordinates on it as the actual position coordinates of the aircraft, thereby realizing the navigation and positioning of the aircraft, and ending the operation.

[0012] Further preferably, the above-mentioned shape features include direction features, trajectory step length features and linear features;

[0013] Directional features include: the direction of each trajectory line vector on the flight trajectory;

[0014] Trajectory step length feature: the length of each trajectory line vector on the flight trajectory;

[0015] Linear features include: the angle of each vector group on the flight trajectory;

[0016] The trajectory vector is the vector from the previous collection point to the next collection point between two adjacent collection points on the flight trajectory;

[0017] Every two adjacent trajectory line vectors on the flight trajectory form a vector group; the angle of the vector group is the angle between the two trajectory line vectors in the vector group.

[0018] Further preferably, the successfully matched candidate flight trajectory satisfies:

[0019] The absolute value of the difference between the direction of each trajectory line vector on the candidate flight trajectory and the direction of the corresponding trajectory line vector on the theoretical flight trajectory is less than or equal to the preset direction difference;

[0020] The absolute value of the difference between the length of each trajectory line vector on the candidate flight trajectory and the length of the corresponding trajectory line vector on the theoretical flight trajectory is less than or equal to the preset step size difference;

[0021] The absolute value of the difference between the angle of each vector group on the candidate flight trajectory and the angle of the corresponding vector group on the theoretical flight trajectory is less than or equal to the linear preset difference.

[0022] Further preferably, the absolute value of the difference between the shape feature of the candidate flight trajectory and the theoretical flight trajectory is: a weighted sum of the absolute value of the difference between the direction feature of the candidate flight trajectory and the theoretical flight trajectory, the absolute value of the difference between the trajectory step feature and the absolute value of the difference between the linear feature;

[0023] The absolute value of the difference in the directional feature is the sum of the absolute values ​​of the difference between the direction of each trajectory line vector on the candidate flight trajectory and the direction of the corresponding trajectory line vector on the theoretical flight trajectory;

[0024] The absolute value of the difference of the trajectory step length feature is the sum of the absolute values ​​of the difference between the length of each trajectory line vector on the candidate flight trajectory and the length of the corresponding trajectory line vector on the theoretical flight trajectory;

[0025] The absolute value of the difference of the linear feature is the sum of the absolute values ​​of the difference between the angles of each vector group on the candidate flight trajectory and the angles of the corresponding vector group on the theoretical flight trajectory.

[0026] Further preferably, the absolute value of the difference between the direction of the trajectory line vector on the candidate flight trajectory and the direction of the corresponding trajectory line vector on the theoretical flight trajectory is the absolute value of the angle between the trajectory line vector on the candidate flight trajectory and the corresponding trajectory line vector on the theoretical flight trajectory.

[0027] Further preferably, the above-mentioned aircraft navigation and positioning method further comprises: the following steps performed between S5 and S6: determining whether the candidate position coordinate set is an empty set, and if so, adjusting L s , and go to S5; otherwise, go to S6.

[0028] Further preferably, the above step S7 further includes:

[0029] When all candidate flight trajectories are not successfully matched, H is adjusted and the process goes to step S3 for iteration; when the number of iterations exceeds the preset number of iterations, the positioning is determined to have failed and the operation ends;

[0030] The above adjustment of H includes: selecting a height value that has not been selected from [H0-σH0, H0+σH0] and updating H.

[0031] Further preferably, the terrain surface fitting function of the terrain area is obtained by performing surface fitting on discrete terrain points in a digital elevation map of the terrain area.

[0032] In a second aspect, the present invention provides an aircraft navigation and positioning system, comprising: a memory and a processor, wherein the memory stores a computer program, and the processor executes the aircraft navigation and positioning method provided in the first aspect of the present invention when executing the computer program.

[0033] In a third aspect, the present invention further provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the aircraft navigation and positioning method provided in the first aspect of the present invention.

[0034] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0035] 1. The present invention provides an aircraft navigation and positioning method. First, the actual nearest echo distances at multiple acquisition points and the geographic information within the coverage of the radar beam are used to determine a set of candidate position coordinates that may be the actual position coordinates of the aircraft, and then the candidate flight trajectories that may be the actual flight trajectories of the aircraft are combined. Finally, the actual shape information carried by the theoretical flight trajectory is fully utilized to match the trajectories of each candidate flight trajectory with the theoretical flight trajectory, and the actual flight trajectory is found from the candidate flight trajectories, thereby determining the actual position coordinates of the aircraft, and realizing accurate navigation and positioning in terrain-assisted navigation.

[0036] 2. Furthermore, in the aircraft navigation and positioning method provided by the present invention, the shape features include directional features, trajectory step features and linear features. Among them, the directional features ensure the directional consistency of the trajectory vector, the trajectory length features ensure the consistency of the trajectory length, and the linear features ensure the consistency of the trajectory shape. Accurate matching can be obtained through comprehensive weighting, thereby obtaining accurate coordinates of the aircraft's real position, with a high success rate, and more accurate navigation and positioning can be achieved.

[0037] 3. Furthermore, the aircraft navigation and positioning method provided by the present invention performs surface fitting on discrete terrain points in the digital elevation map of the terrain area through a surface fitting function to obtain a continuous terrain, which can obtain more accurate positioning accuracy than discrete terrain data. At the same time, the digital elevation map data represents the surface terrain through a series of regularly or irregularly distributed discrete points, including various discrete point distribution situations, and can adapt to more positioning methods compared to other terrain data. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of an aircraft navigation and positioning method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] For aircraft with cruise missions, long-term or long-distance flights cause INS to accumulate positioning errors, resulting in a continuous decrease in navigation accuracy. Due to the fragility of GNSS signals, there is denial, intentional or unintentional interference or deception of GNSS signals, making it impossible to achieve the purpose of navigation and positioning by relying on external channels.

[0041] The prior art often uses terrain matching assisted navigation technology for this application background. It is an assisted navigation technology that uses the terrain geographic information below the aircraft to correct the horizontal disturbance drift error of INS. Among them, typical terrain matching systems include: TERCOM, SITAN, TERPROM and PTAN. When using terrain matching guidance, this method needs to use the measured terrain elevation curve of the terrain matching area to match the geographic elevation information stored in the aircraft to correct the horizontal cumulative error and elevation disturbance error of the aircraft. However, in the terrain matching process, the nearest echo distance measured by the radio altimeter is accurate, but it is inaccurate to calculate the nearest echo distance as the height above the ground, resulting in the terrain elevation curve obtained is not accurate enough, and the final positioning accuracy is also not accurate enough.

[0042] To this end, the first aspect of the present invention provides an aircraft navigation and positioning method, the accuracy of autonomous positioning is improved compared with the existing terrain matching navigation and positioning method, the horizontal positioning accuracy is improved from 10-100 meters to within 6 meters, and the elevation positioning accuracy is improved from 5-15 meters to within 2.5 meters. The overall framework is: during the dynamic flight process, the shortest radar echo information will be generated in real time, the shortest radar echo information and terrain data will be used to generate a possible flight trajectory, the possible flight trajectory will be matched with the flight record trajectory, and the dynamic trajectory matching algorithm will be used to obtain the optimal path, that is, the real flight trajectory, and then the positioning error of the three dimensions of the aircraft INS will be accurately corrected at the same time.

[0043] Specifically, the aircraft navigation and positioning method provided by the present invention includes:

[0044] S1. When the aircraft flies at a fixed altitude above a certain terrain area (i.e., terrain matching area), a theoretical flight trajectory of the aircraft is intercepted from the flight record; the flight trajectory includes: M collection points collected in chronological order; the information on the i-th collection point includes: the actual closest echo distance L of the aircraft at the i-th collection point iand theoretical position coordinates Wherein, i=1,2,…,M, M≥2; H is a height value selected from [H0-σH0,H0+σH0]; H0 is the measured height of the pressure altimeter on the aircraft; σ is a preset ratio, 0<σ<1;

[0045] In an optional implementation, based on the considerations of matching success rate and matching real-time performance, the matching probability of less than 3 trajectory collection points is only 75% at most, and the matching probability of more than 4 is more than 99%, but the time consumed gradually increases, so the trajectory matching of 4 collection points is set, and the value of M is 4.

[0046] In one optional implementation, σ is 1%. In another optional implementation, σ is 2%. Preferably, [H0-σH0, H0+σH0] is [H0-10, H0+10], in meters.

[0047] It should be noted that when the aircraft altitude remains unchanged, the aircraft flies along a predetermined route, intercepts a theoretical flight trajectory in the flight record, and this trajectory has multiple airborne radar echo information collection points, and obtains the nearest echo information corresponding to the collection point. The distance between adjacent collection points can be equal or unequal, and is set according to the situation. The distance should be moderate and match the flight speed and collection efficiency of the aircraft. In an optional implementation, the intercepted theoretical flight trajectory has 4 airborne radar echo information collection points, and the distance between adjacent collection points in the trajectory is 25 meters.

[0048] S2: Sampling the position coordinates in the local area of ​​the i-th acquisition point to obtain N candidate position coordinates (X ij ,Y ij ,H), j = 1, 2, ..., N, N ≥ 2; and then form a candidate position coordinate set {Ψ i}; Among them, any coordinate point in the local area has the same theoretical height H as the i-th acquisition point, and the distance between the two is less than or equal to the preset distance R, that is,

[0049] In an optional implementation, the local area of ​​the i-th collection point can be a circular area, a square area, an elliptical area, etc. centered at the i-th collection point, which is not limited here; in an optional implementation, based on the size of the horizontal drift error, the preset distance R is 200m.

[0050] In an optional implementation, based on a horizontal drift error of 200 meters, the number of grid points with a spacing of 1 meter within a 200-meter square is 40,000, and the value of N is 40,000.

[0051] S3, in (Xij ,Y ij ,H) to obtain the coordinates within the ground coverage area corresponding to K i The topographic position coordinates (X ijk ,Y ijk ,Z ijk ), k=1,2,…,K i , K i ≥2; among which, The corresponding ground coverage range is from (X ij ,Y ij ,H) The coverage of the downward-emitting radar beam on the terrain area; Z ijk =S(X ijk ,Y ijk );S(·) is the terrain surface fitting function of the terrain area;

[0052] Specifically, the above (X ijk ,Y ijk ,Z ijk )satisfy:

[0053]

[0054] Where θ is the radar beam angle.

[0055] In an optional implementation, θ=3°; based on the radar beam angle θ=3° and the effective height above the ground of 3000 meters, it is calculated that the number of coordinates sampled within the ground coverage range of the radar beam does not exceed (tan1.5°×3000) 2 =6400, that is, K i The value is 6400.

[0056] It should be noted that the terrain surface fitting function of the terrain area is obtained by performing surface fitting on discrete terrain points in the terrain area of ​​sampled geographic information. Preferably, in an optional implementation, the terrain surface fitting function of the terrain area is obtained by performing surface fitting on discrete terrain points in a digital elevation map of the terrain area. Specifically, the three-dimensional coordinates of each discrete terrain point in the digital elevation map of the terrain area are known. Considering that there are discontinuous terrain data for discrete terrain points in the digital elevation map of the terrain area, the present invention implements surface fitting of the terrain area by interpolating existing discrete points to generate a continuous elevation surface, so that the surface height can be effectively estimated on a finer grid, thereby obtaining a more accurate terrain representation and more comprehensive terrain data. The coordinate information of missing terrain points is completed through interpolation methods, and the coordinate information of all terrain points within the ground coverage range of the ranging radar beam is obtained, so that the discrete grid points within the coverage range of the radar beam are fitted to form a continuous surface, which is convenient for subsequent dynamic trajectory matching and improving the navigation and positioning accuracy; among them, there are many interpolation methods that can be used, such as cubic interpolation method, polynomial interpolation method, triangular interpolation method, spline interpolation method, etc.

[0057] The following is an example of how to use bicubic interpolation in the cubic interpolation method to fit the terrain discrete points in the digital elevation map into a continuous terrain surface. For a point to be interpolated, by considering the 16 nearest neighboring points around the point to be interpolated, first use a cubic polynomial to get the interpolation weight, then use the weight to perform a weighted average of the elevation values ​​of the 16 known data points to get the elevation z of the point to be interpolated, and use the bicubic interpolation method to traverse all the points to be interpolated, and fit the discrete grid points in the digital elevation map into a smooth and continuous surface. The specific process is as follows:

[0058] 1. Coordinates of the point to be interpolated: The coordinates of the point to be interpolated are (x, y).

[0059] 2. Known data point: Let the coordinates of the known data point be (x i ,y i , z i ), where i = 0, 1, 2, ..., 15, these points constitute the 16 nearest neighbor points around the point to be interpolated (x, y).

[0060] 3. Weight calculation: For each known data point, calculate the distance weight from it to the point to be interpolated. The weight function w(u,υ) can be in many forms, one of the common ones is the bicubic weight function:

[0061] w(u,υ)=(1-|u| 3 ) 2 (3|u| 2 -2|u|3 )+sgn(u)(u 3 -5|u| 2 +8|u|-4)+(1—|υ|3) 2 (3|υ| 2 -2|υ| 3 )+sgn(υ)(|υ| 3 -5|υ| 2 +8|υ|-4)

[0062] Where u = xx i ,υ=yy i , sgn is the sign function; when v is a positive number, sgn(υ)=1; when v is a negative number, sgn(υ)=-1.

[0063] 4. Interpolation formula: Use weights to perform weighted average on the elevation values ​​of known data points to obtain the elevation z of the point to be interpolated:

[0064] 5. Implementation: In Matlab, you can use the griddata function to implement cubic interpolation and specify the method as 'cubic'.

[0065] S4, in (X ij , Y ij , find the nearest echo distance L within the ground coverage area corresponding to H) ij .

[0066] Specifically, L ij =min{L ijk},

[0067]

[0068] Among them, X ij , Y ij and H represent the candidate position coordinates of the aircraft in the x, y and z directions respectively; ijk , Y ijk and Z ijk Respectively represent the coordinates of the terrain points in the x, y and z directions on the terrain area; i = 1, 2, ..., M; j = 1, 2, ..., N; k = 1, 2, ..., K i In an optional implementation, the coordinate system is a left-handed coordinate system, with the x-axis facing north, the y-axis facing east, and the z-axis facing the sky, and the coordinate in the z direction represents the altitude.

[0069] S5. Calculate the nearest echo distance L ij Distance from true echo L i Is the absolute value of the difference less than or equal to the preset value L s , that is, whether |Lij -Li|≤L s ; If so, then the candidate position coordinate set {Ψ i}Retain the (X ij , Y ij , H), otherwise, delete the (X ij , Y ij , H), thereby realizing the candidate position coordinate set {Ψ i}Filter;

[0070] In an optional implementation manner, the preset value L s The value is 1m.

[0071] S6. After the screening is completed, the filtered coordinate set {Ψ i} is used as the basic data to obtain all candidate flight trajectories of the aircraft; the candidate flight trajectories are obtained by selecting a candidate position from the candidate position coordinate set at each collection point and sorting them in the order of the collection points;

[0072] S7. Match each candidate flight trajectory with the theoretical flight trajectory respectively, retain the successfully matched candidate flight trajectory, and use the candidate flight trajectory with the smallest absolute value of the difference between the shape feature of the theoretical flight trajectory as the actual flight trajectory of the aircraft, and the candidate position coordinates on it as the actual position coordinates of the aircraft, thereby realizing the navigation and positioning of the aircraft, and ending the operation.

[0073] In an optional implementation manner, the shape feature includes a direction feature, a trajectory step feature and a linear feature;

[0074] Directional features include: the direction of each trajectory line vector on the flight trajectory;

[0075] Trajectory step length feature: the length of each trajectory line vector on the flight trajectory;

[0076] Linear features include: the angle of each vector group on the flight trajectory;

[0077] The trajectory vector is the vector from the previous collection point to the next collection point between two adjacent collection points on the flight trajectory;

[0078] Every two adjacent trajectory line vectors on the flight trajectory form a vector group; the angle of the vector group is the angle between the two trajectory line vectors in the vector group.

[0079] In an optional implementation manner, the successfully matched candidate flight trajectory satisfies:

[0080] The absolute value of the difference between the direction of each trajectory line vector on the candidate flight trajectory and the direction of the corresponding trajectory line vector on the theoretical flight trajectory |α i|Less than or equal to the preset direction difference α ※ , that is |α i |≤α ※ Preferably, the angle based on the deviation of one grid size is arc tan (1 / 25) = 2.3°, and the preset difference value of the direction is α ※ The value is 2.3°.

[0081] The absolute value of the difference between the length of each trajectory line vector on the candidate flight trajectory and the length of the corresponding trajectory line vector on the theoretical flight trajectory |β i |Less than or equal to the preset step size difference β ※ , that is |β i |≤β ※ In an optional implementation, the second preset difference corresponding to a certain trajectory line vector on the candidate flight trajectory is a preset ratio of the length of the corresponding trajectory line vector on the theoretical flight trajectory, and the preset ratio is usually a positive number less than or equal to 0.02. Preferably, based on a ratio of a grid spacing to a step size of 1 / 25=0.04, the step size preset difference β ※ The value is 0.04.

[0082] The absolute value of the difference between the angle of each vector group on the candidate flight trajectory and the angle of the corresponding vector group on the theoretical flight trajectory |γ i |Less than the third preset difference γ ※ , that is |γ i |≤γ ※ Preferably, based on the vertex deviation of a certain side by one grid size, the angle deviation angle is arctan (1 / 25) = 2.3°, and the linear preset difference γ ※ The value is 2.3°.

[0083] Through the above method, candidate flight trajectories with direction consistency, trajectory step consistency and linear consistency with the theoretical flight trajectory are screened out.

[0084] In an optional implementation, the absolute value of the difference between the shape features of the candidate flight trajectory and the theoretical flight trajectory (difference cost value) Γ is: the weighted sum of the absolute value of the difference between the direction features of the candidate flight trajectory and the theoretical flight trajectory α, the absolute value of the difference between the trajectory step features β and the absolute value of the difference between the linear features γ, that is, Γ = θ1·α+θ2·β+θ3·γ;

[0085] The absolute value of the difference in directional features α is the sum of the absolute values ​​of the difference between the direction of each trajectory line vector on the candidate flight trajectory and the direction of the corresponding trajectory line vector on the theoretical flight trajectory, that is, M is the number of flight trajectory collection points;

[0086] The absolute value of the difference of the trajectory step length feature β is the sum of the absolute values ​​of the difference between the length of each trajectory line vector on the candidate flight trajectory and the length of the corresponding trajectory line vector on the theoretical flight trajectory, that is, M is the number of flight trajectory collection points;

[0087] The absolute value of the difference of the linear feature γ is the sum of the absolute values ​​of the difference between the angles of each vector group on the candidate flight trajectory and the angles of the corresponding vector group on the theoretical flight trajectory, that is, M is the number of flight trajectory collection points.

[0088] In an optional implementation, since the dimensions of the three types of difference band values ​​are different, α and β need to be dimensionless. Based on the fact that the maximum directional deviation and linear deviation are 180°, α and β are divided by 180°, i.e., α / 180° and β / 180°, thus obtaining the dimensionless numerical solution Γ. Among them, θ1, θ2, and θ3 are the weights of α, β, and γ respectively. According to the influence of α, β, and γ on the success of matching and the factors of dimensionless processing, the weights are set to θ1=2, θ2=10, and θ3=5 respectively; finally, the candidate flight trajectory corresponding to the minimum difference cost value min(Γ) is taken as the true flight trajectory, and the positioning error is corrected.

[0089] In an optional implementation, the absolute value of the difference between the direction of the trajectory line vector on the candidate flight trajectory and the direction of the corresponding trajectory line vector on the theoretical flight trajectory is the absolute value of the angle between the trajectory line vector on the candidate flight trajectory and the corresponding trajectory line vector on the theoretical flight trajectory.

[0090] It should be noted that when expressing the angle, in addition to using the angle itself, it can also be expressed by the sine value of the angle, etc., and there is no limitation here.

[0091] In an optional implementation manner, the above-mentioned aircraft navigation and positioning method further includes: the following steps performed between S5 and S6: determining whether the candidate position coordinate set is an empty set, and if so, adjusting L s , and go to S5; otherwise, go to S6.

[0092] Preferably, the preset value L s The value is 1m; if {Ψ i} is an empty set, then εL s The step size gradually increases the preset value L s The size of i In an optional implementation, ε is 0.1.

[0093] In an optional implementation manner, the above step S7 further includes:

[0094] When all candidate flight trajectories are not successfully matched, H is adjusted and the process goes to step S3 for iteration; when the number of iterations exceeds the preset number of iterations, the positioning is determined to have failed and the operation ends;

[0095] The above adjustment of H includes: selecting a height value that has not been selected from [H0-σH0, H0+σH0] and updating H.

[0096] Preferably, in an optional implementation manner, the height value H selected from [H0-σH0, H0+σH0] in step S1 is the smallest H0-σH0. The above adjustment of H includes: selecting a height value from [H0-σH0, H0+σH0] in units of 1 meter in order from small to large to iteratively update H.

[0097] In an optional implementation manner, the preset number of iterations is 100 times.

[0098] It should be noted that if the optimal candidate flight trajectory that meets the conditions can be successfully matched, it means that the altitude and horizontal position are accurate, that is, the real flight trajectory. The disturbance drift error of the three dimensions of the aircraft INS is corrected according to the real flight trajectory points. If a successful candidate flight trajectory cannot be obtained, it means that the altitude is inaccurate and the altitude needs to be adjusted for matching.

[0099] It should be noted that in three-dimensional coordinate positioning and navigation, the altitude and horizontal position are interdependent and complementary. When both have disturbance drift errors, it is not easy to accurately correct the errors of both at the same time. INS has a large disturbance drift error in altitude, and cannot obtain the nearest echo information of the true position of the aircraft, and thus cannot correct the horizontal positioning error. At the same time, INS has a large disturbance drift error in the horizontal position. Although there is the nearest echo information of the true position, it cannot obtain the accurate altitude. The horizontal position is two dimensions, which is larger than the altitude of one dimension in terms of value range and cumulative error. It is more difficult to use this as a starting point. The difficulty of starting with the altitude of one dimension can be reduced by an order of magnitude. In the existing altitude data, the altitude with disturbance error measured by the barometric altimeter can be used for reference. In an optional implementation, the FRTTS-02 high-precision barometric altimeter, which is more commonly used in the market and provided by Fuaotong Technology, is selected. It is mainly used for military and civil aircraft and aviation ground equipment. The measurement altitude is 200-10000m, the measurement accuracy is 10 meters, and the resolution is 1 meter. Therefore, the aircraft altitude is iteratively updated and re-matched within a range of 10 meters above and below the altitude H0 measured by the barometric altimeter until both the altitude and horizontal position can be successfully matched.

[0100] like Figure 1FIG. 1 is a schematic diagram of an aircraft navigation and positioning method provided by an embodiment of the present invention; it can be seen from the figure that the actual closest echo distance L at multiple acquisition points is used. i (dashed line with arrow) and the terrain position coordinates within the ground range of the airborne radar beam (X i ※ , Y i ※ , H), the candidate position coordinate set {Ψ i}({Ψ i}N candidate position coordinates (X ij , Y ij , H) are composed of five-pointed stars, circles and triangles in the figure above), and then a set of candidate flight trajectories that may be the real flight trajectories of the aircraft are obtained (such as the solid lines, dotted horizontal lines and dotted lines connecting the candidate position coordinates in the figure above). Then, using the real shape information carried by the flight record trajectory (solid line connecting the V shape), each candidate flight trajectory is matched with the flight record trajectory based on shape features, and the real flight trajectory is found from the candidate flight trajectory, and then the coordinate position of the aircraft is corrected.

[0101] In order to further illustrate the aircraft navigation and positioning method provided by the present invention, the effectiveness of the aircraft navigation and positioning method provided by the present invention is further analyzed and illustrated through a Matlab simulation comparison experiment.

[0102] Six different true values ​​of aircraft altitude (i.e., altitude) are set, namely 1000.5 meters, 1500.5 meters, 2000.5 meters, 3000.5 meters, 5000.5 meters, and 7500.5 meters. For each aircraft altitude, a 21-order square matrix is ​​randomly generated, and the matrix elements are all numbers between [300,700]. This matrix is ​​used to simulate the terrain elevation data of a 500-meter square terrain matching area (the resolution of the digital elevation map DEM is 25 meters).

[0103] It should be noted that the setting of terrain matching areas is very particular. The size and number of matching areas must meet certain requirements. If the terrain matching area is too small, it means that more matching areas must be set up in the entire flight corridor. However, the terrain matching area has very high requirements, and there are not many areas suitable for terrain matching. Based on track planning and security cost considerations, generally only a few terrain matching areas are set up in the entire flight corridor. If the distance between adjacent matching areas is too long, it will cause a greater drift error, which requires the length of the matching area to be long enough. The flight distance between adjacent matching areas will cause a drift error of about half the length of the matching area, so the size of the matching area is set according to the drift error. At the same time, the time consumption of the matching algorithm is roughly equivalent to the time consumed by the aircraft to navigate half the length of the matching area. The matching algorithm time of the present invention is 1 second (experimental machine: DESKTOP-DMGL7L9; CPU: Intel(R) Core(TM) i7-7700K CPU@4.20GHz; GPU: NVIDIAGeForce GTX 1650; memory: 16GB; operating system: Windows 10; simulation software: matlab), the flight speed of the aircraft is set to 0.7 times the speed of sound, the drift error of adjacent matching areas is set to 200 meters, and considering comprehensively, a terrain matching area with a length of 250*2=500 meters is set.

[0104] The aircraft flies horizontally over the north-south direction near the center line of the region (250.3 meters away from the westernmost edge of the region), starting from 50.4 meters away from the southernmost edge of the region, and sets 7 groups of sequences every 50 meters along the north-south center line in the region. Each group of sequences has 4 radar echo collection points, and the interval between adjacent collection points is 25 meters, until it is 74.6 meters away from the northernmost edge of the region. It should be noted that if the sequence length is too short when the sequence is matched, the same sequence to be matched may find multiple matching sequences that meet the requirements in the matching area, resulting in mismatching, so the sequence length cannot be too short. However, if the sequence length is too long, the calculation time is too long, which does not meet the requirements of the matching area size setting. According to the situation of this embodiment, a sequence of 3*25=75 meters in length is set, the calculation time is 1 second, and the probability of mismatch is less than 1%.

[0105] The drift error of the INS in this embodiment is within 200 meters. Within the range of 200 meters with each radar echo collection point as the center, a coordinate point cloud with the shortest distance echo length equal to the collection point is found as the possible aircraft coordinates. The four possible sets of aircraft coordinates are combined into multiple sets of possible flight trajectory sets, which are then matched with the recorded theoretical flight trajectory. If the step length similarity, direction similarity and linear similarity all meet the threshold requirements, the trajectory with the smallest comprehensive weight index is taken as the optimal trajectory as the true flight trajectory, and then the true trajectory point coordinates are used to simultaneously correct the altitude disturbance measurement error and the horizontal position drift cumulative error. The results of navigation positioning at different altitudes are shown in Tables 1 to 6.

[0106] Table 1 Positioning results when the aircraft is actually at an altitude of 1000.5 meters (meters)

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[0109] Table 2 Positioning results when the aircraft is actually at an altitude of 1500.5 meters (meters)

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[0111] Table 3 Positioning results when the aircraft is actually at an altitude of 2000.5 meters (meters)

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[0113]

[0114] Table 4 Positioning results when the aircraft is actually at an altitude of 3000.5 meters (meters)

[0115]

[0116] Table 5 Positioning results when the aircraft is actually at an altitude of 5000.5 meters (meters)

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[0119] Table 6 Positioning results when the aircraft's actual altitude is 7500.5 meters (meters)

[0120]

[0121] It can be seen from Tables 1 to 6 that in the simulation experiment of aircraft navigation and positioning over the terrain matching area with large terrain undulations, the effect of navigation and positioning at low altitude is better than that at high altitude. When the altitude of the aircraft is below 3,000 meters, each calculation of the positioning method provided by the present invention can obtain accurate three-dimensional coordinates of the aircraft, with a horizontal positioning accuracy within 5.92 meters and an elevation positioning accuracy within 2.5 meters.

[0122] Traditional terrain matching assisted navigation and positioning methods include: TERCOM (Terrain Contour Matching), SITAN (Sandia Terrain Aided Navigation), TERPROM (Terrain Profile Matching), and PTAN (Precision Terrain Aided Navigation System). Currently, the terrain matching assisted navigation and positioning method with higher accuracy is the inertial navigation-terrain matching-satellite composite guidance method. A comparison of the positioning results of the present invention and the existing terrain matching assisted navigation and positioning methods is shown in Table 7. As can be seen from Table 7, in comparison, the autonomous positioning effect of the present invention is better than that of the existing terrain matching system in terms of both horizontal positioning accuracy and elevation positioning accuracy. The simulation experiment results verify the effectiveness and accuracy of the autonomous positioning of the present invention over the terrain matching area with large terrain undulations.

[0123] Table 7 Comparison of positioning results between the present invention and the existing terrain matching system (meters)

[0124]

[0125] In general, due to the fragility of GNSS signals, especially in mountainous airborne navigation applications, there is denial, intentional or unintentional interference or deception of GNSS signals, and terrain matching is still a reliable source of autonomous positioning and navigation information. The present invention can accurately and autonomously locate in terrain matching areas with large terrain fluctuations, and at the same time complete the task of correcting the horizontal position drift error and altitude disturbance error of the aircraft output by the inertial navigation, which can greatly improve the accuracy of single autonomous positioning of terrain-assisted navigation, and effectively enhance the navigation and positioning capability of the aircraft under complex terrain conditions and the low-altitude penetration capability.

[0126] In summary, when there is denial, intentional or unintentional interference or deception of GNSS signals, the typical terrain matching navigation has the problem of inaccurate positioning. The present invention provides an aircraft navigation and positioning method based on dynamic trajectory matching. The overall idea is to match the flight trajectory recorded during dynamic flight with the possible flight trajectory generated, and use dynamic trajectory matching to obtain the optimal trajectory, that is, the real flight trajectory, and then correct the three-dimensional coordinate error of the aircraft. It avoids the problem that the traditional terrain height matching method uses the shortest echo distance of the airborne ranging radar as the height of the aircraft from the ground, which has a large error, improves the accuracy of height measurement and positioning, and solves the problem of inaccurate autonomous positioning of terrain matching assisted navigation. The horizontal positioning accuracy is within 5.92 meters, and the elevation positioning accuracy is within 2.5 meters. In particular, the horizontal positioning accuracy is improved by an order of magnitude, realizing autonomous and precise navigation and positioning, saving the cost and difficulty of track planning and data assurance.

[0127] In a second aspect, the present invention provides an aircraft navigation and positioning system, comprising: a memory and a processor, wherein the memory stores a computer program, and the processor executes the aircraft navigation and positioning method provided in the first aspect of the present invention when executing the computer program.

[0128] The related technical solution is the same as the aircraft navigation and positioning method provided in the first aspect of the present invention, and will not be described in detail here.

[0129] In a third aspect, the present invention further provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the aircraft navigation and positioning method provided in the first aspect of the present invention.

[0130] The related technical solution is the same as the aircraft navigation and positioning method provided in the first aspect of the present invention, and will not be described in detail here.

[0131] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for aircraft navigation and positioning, characterized in that: include: S1. When the aircraft flies at a fixed altitude over a certain terrain area, a theoretical flight trajectory of the aircraft is intercepted from the flight record; The flight trajectory includes: M collection points collected in chronological order; the information on the i-th collection point includes: the actual closest echo distance L of the aircraft at the i-th collection point i and theoretical position coordinates Wherein, i=1,2,…,M, M≥2; H is a height value selected from [H0-σH0,H0+σH0]; H0 is the measured height of the pressure altimeter on the aircraft; 0<σ<1; S2. Sampling the position coordinates in the local area of ​​the i-th acquisition point to obtain N candidate position coordinates (X ij ,Y ij ,H), j=1,2,…,N,N≥2, thereby forming a candidate position coordinate set at the position of the i-th collection point; any position coordinate point in the local area is the same as the theoretical height H of the i-th collection point, and the distance between the two is less than or equal to the preset distance; S3, in (X ij ,Y ij ,H) to obtain the coordinates within the ground coverage area corresponding to K i The topographic position coordinates (X ijk ,Y ijk ,Z ijk ), K i ≥2; the ground coverage range is from (X ij ,Y ij ,H) the coverage of the radar beam emitted downward from the position on the terrain area; Z ijk =S(X ijk ,Y ijk ); S(·) is the terrain surface fitting function of the terrain area; S4, calculate (X ij ,Y ij ,H) and the distance between each terrain position coordinate, and the minimum distance is taken as the nearest echo distance L ij ; S5. Determine L ij With L i Is the absolute value of the difference less than or equal to the preset value L s If so, then keep the (X ij ,Y ij ,H), otherwise, delete the (X ij ,Y ij ,H), thereby realizing the screening of candidate position coordinate sets; S6. After the screening is completed, all candidate flight trajectories of the aircraft are obtained; the candidate flight trajectories are obtained by sorting a candidate position selected from the candidate position coordinate set at each collection point position according to the order of the collection points; S7. Match each candidate flight trajectory with the theoretical flight trajectory respectively, retain the successfully matched candidate flight trajectory, and use the candidate flight trajectory with the smallest absolute value of the difference between the shape feature of the theoretical flight trajectory as the actual flight trajectory of the aircraft, and the candidate position coordinates on it as the actual position coordinates of the aircraft, thereby realizing the navigation and positioning of the aircraft, and ending the operation.

2. The aircraft navigation and positioning method according to claim 1, characterized in that: The shape features include direction features, trajectory step length features and linear features; The directional features include: the direction of each trajectory line vector on the flight trajectory; The trajectory step length feature: the length of each trajectory line vector on the flight trajectory; The linear features include: the angle of each vector group on the flight trajectory; The trajectory vector is a vector from the first to the second of two adjacent collection points on the flight trajectory; Every two adjacent trajectory line vectors on the flight trajectory form a vector group; the angle of the vector group is the angle between the two trajectory line vectors in the vector group.

3. The aircraft navigation and positioning method according to claim 2, characterized in that: The candidate flight trajectories that are successfully matched meet the following requirements: The absolute value of the difference between the direction of each trajectory line vector on the candidate flight trajectory and the direction of the corresponding trajectory line vector on the theoretical flight trajectory is less than or equal to the preset direction difference; The absolute value of the difference between the length of each trajectory line vector on the candidate flight trajectory and the length of the corresponding trajectory line vector on the theoretical flight trajectory is less than or equal to the preset step size difference; The absolute value of the difference between the angle of each vector group on the candidate flight trajectory and the angle of the corresponding vector group on the theoretical flight trajectory is less than or equal to the linear preset difference.

4. The aircraft navigation and positioning method according to claim 2, characterized in that: The absolute value of the difference between the shape feature of the candidate flight trajectory and the theoretical flight trajectory is: the weighted sum of the absolute value of the difference between the direction feature of the candidate flight trajectory and the theoretical flight trajectory, the absolute value of the difference between the trajectory step feature and the absolute value of the difference between the linear feature; The absolute value of the difference of the directional feature is the sum of the absolute values ​​of the difference between the direction of each trajectory line vector on the candidate flight trajectory and the direction of the corresponding trajectory line vector on the theoretical flight trajectory; The absolute value of the difference of the trajectory step length feature is the sum of the absolute values ​​of the difference between the length of each trajectory line vector on the candidate flight trajectory and the length of the corresponding trajectory line vector on the theoretical flight trajectory; The absolute value of the difference of the linear feature is the sum of the absolute values ​​of the difference between the angles of each vector group on the candidate flight trajectory and the angles of the corresponding vector group on the theoretical flight trajectory.

5. The aircraft navigation and positioning method according to claim 1, characterized in that: Also includes: The following steps are performed between S5 and S6: Determine whether the candidate position coordinate set is an empty set. If so, adjust L s , and go to S5; otherwise, go to S6.

6. The aircraft navigation and positioning method according to claim 1, characterized in that: The terrain surface fitting function of the terrain area is obtained by performing surface fitting on discrete terrain points in a digital elevation map of the terrain area.

7. The aircraft navigation and positioning method according to any one of claims 1 to 6, characterized in that: The step S7 further comprises: When all candidate flight trajectories are not successfully matched, H is adjusted and the process goes to step S3 for iteration; when the number of iterations exceeds the preset number of iterations, the positioning is determined to have failed and the operation is terminated; The adjusting H includes: selecting a height value that has not been selected from [H0-σH0, H0+σH0] and updating H.

8. An aircraft navigation and positioning system, characterized in that: include: A memory and a processor, wherein the memory stores a computer program, and the processor executes the aircraft navigation and positioning method according to any one of claims 1 to 7 when executing the computer program.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the aircraft navigation and positioning method according to any one of claims 1 to 7.

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