Time difference direction-finding cooperative positioning method based on star-sky-ground combination

Abstract

The invention belongs to the field of signal processing, particularly relates to a target positioning problem, and particularly relates to a time difference direction finding cooperative positioning method under a space-based, air-based and ground-based combined positioning model. According to the invention, the target positioning equation set is constructed according to the position relation between the target and the unmanned aerial vehicle and the position relation between the target and the ground station, the accuracy of target position information estimation by the positioning model can be ensured, then based on the least square thought, a star-sky-ground TDOA-AOA joint-based least square positioning algorithm is deduced, the target positioning equation set is solved, and the positioning accuracy of the target is improved. And solving target position information. Starry-sky-ground integrated positioning is a positioning system combining a satellite positioning system and a near-ground positioning system, the defect that observation information of a satellite positioning platform is little is made up to a certain degree, and meanwhile the positioning range of a traditional near-ground positioning system is expanded by means of a satellite-borne platform.

Description

Technical Field

[0001] The invention belongs to the field of signal processing, relates to a target positioning problem in the field of signal processing, and in particular to a star-space-ground joint time difference direction finding collaborative positioning method. Background Art

[0002] The passive positioning system only needs to passively receive the signal emitted by the target radiation source to locate the target. Compared with the active positioning system, the passive positioning system has superior anti-interference ability and concealment. With the development of satellite reconnaissance technology, the passive positioning system based on the satellite electronic reconnaissance platform has been increasingly valued and matured to obtain target information within a larger instantaneous reconnaissance range.

[0003] Existing passive positioning systems can be divided into two types based on the type of observation station: satellite-based positioning systems and land-based positioning systems. The satellite-based positioning system mainly uses a single satellite or multiple satellites as a platform to receive target signals, extract target parameters, and locate the target. It has the characteristics of wide reconnaissance range and full real-time line-of-sight reconnaissance. However, the satellite positioning system based on a single star is limited, the observation information acquisition is limited, the positioning accuracy is poor, and it generally requires the combination of the earth's spherical model to obtain the target position information. The multi-star system is cumbersome to implement, and the parameter measurement accuracy requirements are high. At the same time, it requires inter-satellite clock synchronization, and the cost of interstellar networking is high, and it does not have high flexibility. The land-based positioning system has loose requirements on the station environment, and at the same time avoids the problem of the target being unable to be seen together due to the narrow beam width. In addition, it has the characteristics of simple system composition, low maintenance cost, portability and mobility. However, the land-based positioning system has limitations such as being easily blocked.

[0004] In view of the above problems, the inherent defects of passive positioning systems such as satellite-borne positioning systems and land-based short baseline positioning systems lead to the inability to provide continuous, stable and reliable positioning results. Consider adding a ground observation system based on a single-satellite platform to make up for the defects of the single-satellite system and improve the positioning accuracy. Compared with the land-based positioning system, it increases the positioning line-of-sight reconnaissance range. The paper "Li Gaoyun, Li Bin, Chen Liang. Satellite-ground collaborative reconnaissance and positioning under low-constraint conditions [J]. Electronic Information Countermeasure Technology, 2019, 34(1): 1–4, 18." proposes a satellite-ground joint positioning algorithm combined with the earth's spherical equation to achieve collaborative positioning of ground targets. However, the existing satellite-ground joint positioning system achieves the positioning of aerial targets with high requirements for direction finding accuracy and complex systems. It also needs to measure the pitch angle or can only estimate the position of ground targets, which is not very practical. Summary of the invention

[0005] The purpose of the present invention is to address the problem of insufficient positioning capabilities of satellite positioning, satellite-ground joint positioning, etc. in complex environments, and propose a time difference direction finding collaborative positioning method based on the joint star-space-ground. Based on the target positioning method based on the joint star-space-ground, the satellite, the unmanned aerial vehicle and the ground station are unified in the same coordinate system, and the directional surface observation equation is constructed according to the positional relationship between the target and the coordinate origin of the centroid coordinate system, and the time difference observation equation is constructed according to the arrival time difference between the target arriving at the origin of the centroid coordinate system and the satellite and the arrival time difference between the target arriving at the origin of the centroid coordinate system and the ground station. The azimuth surface observation equation and the time difference observation equation are combined to obtain the target positioning equation group based on the joint star-space-ground, and the parameter equation is solved to obtain the estimated value of the target position.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A time difference direction finding collaborative positioning method based on star-space-ground combination includes the following steps:

[0008] S1. Based on the coordinate conversion method, the coordinates of the UAV, satellite and ground station are converted from the geodetic coordinate system to the paracentric coordinate system with the UAV as the origin, and a star-space-ground integrated positioning model is established;

[0009] The coordinates of the drone are s0 = (x0, y0, z0) = (0, 0, 0), and the coordinates of the satellite are s1 = (x1, y1, z1) T , the ground station coordinates are s2 = (x2, y2, z2) T , the radiation source target coordinates in three-dimensional space u=(x,y,z) T ;

[0010] S2, the distance from the target to the satellite is The distance from the target to the drone is The distance from the target to the ground station is

[0011]

[0012] S3, the arrival time difference between the target arrival UAV and the satellite and ground station is: Where c is the propagation speed of the electromagnetic wave signal;

[0013] The observation equation of time difference of arrival TDOA is:

[0014] Among them, τ i is the measured value corresponding to the arrival time difference, is the measurement noise corresponding to the arrival time difference.

[0015] For the further improvement or specific implementation of the above-mentioned time difference direction finding collaborative positioning method based on the combination of star, sky and ground, the observation equation corresponding to the azimuth angle of the target reaching the drone is:

[0016]

[0017] Among them, θ represents the measured value of the azimuth from the target to the drone, v θ is the corresponding measurement noise;

[0018] After linearizing the azimuth angle and substituting the master station as the origin of the coordinate system, the azimuth angle observation equation is simplified to: θ )-y=0.

[0019] A further improvement or specific implementation of the above-mentioned satellite-space-ground joint time difference direction finding collaborative positioning method further includes a step for determining the estimated position of the target, and the specific steps include:

[0020] Determine the spatial plane based on the three points, the direction-finding azimuth θ of the drone to the target, obtain the direction-finding line of the geographic coordinate system with the drone as the origin, expand it into three-dimensional space, and obtain the direction-finding plane; randomly select three non-collinear points on the direction-finding plane to determine the direction-finding plane;

[0021] Take the coordinates of three points in the coordinate system with the drone main station as the origin:

[0022] s0=(x0,y0,z0)=(0,0,0);

[0023] s a =(x a ,y a ,z z )=(tanθ,1,0);

[0024] s b =(x b ,y b ,z b )=(0,0,-1);

[0025] Substituting the target position into the direction finding plane, we have

[0026]

[0027] Expand the direction-finding plane equation to get p x x+p y y+p z z = q;

[0028] in

[0029] p x =(y a-y0)(z b -z0)-(z a -z0)(y b -y0)

[0030] p y =-(x a -x0)(z b -z0)+(z a -z0)(x b -x0)

[0031] p z =(x a -x0)(y b -y0)-(y a -y0)(x b -x0)

[0032] q=x0·p x +y0·p y +z0·p z

[0033] The direction finding plane equation ① and the time difference equation ② are combined, and the equation group is solved to obtain the position of the target source; the combined equations are:

[0034]

[0035] Solving the equation yields the estimated position of the target.

[0036] The beneficial effects of the present invention are:

[0037] The invention proposes a satellite-space-ground joint time difference direction finding collaborative positioning method, which has the following advantages:

[0038] 1. The present invention only requires a single satellite, a single UAV and a ground station to achieve three-dimensional positioning of the target, and only requires the UAV to perform azimuth direction finding on the target to obtain a closed-form solution for the three-dimensional position of the target.

[0039] 2. From the perspective of the positioning model, the present invention is based on the target positioning method of the star-sky-ground joint TDOA-AOA. The target direction is measured by the drone, and the direction plane pointing from the drone to the target is obtained. Then, the time difference between the target signal reaching the drone and the satellite, and the time difference between the target signal reaching the drone and the ground station are used to obtain two equal time difference rotation hyperboloids. By solving the intersection of the azimuth plane and the two time difference hyperboloids, the target position azimuth plane is nearly perpendicular to the hyperboloid shape, which can ensure the accuracy of the positioning model in estimating the target position information;

[0040] 3. Compared with the traditional land-based positioning system, the present invention uses the lifting platform to find the direction, which has a wider reconnaissance field of view. At the same time, the present invention no longer uses satellites to find the direction of the target, but uses near-ground measurement points to find the direction of the target, avoiding the influence of satellite attitude error and position error on the direction finding effect when using satellite direction finding. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of the time difference direction finding collaborative positioning method based on the combination of star, space and ground;

[0042] Figure 2 This is a schematic diagram of station layout in the positioning center coordinate system of the implementation example of the present invention;

[0043] Figure 3 This is a simulation result diagram of the performance of the joint air-ground time difference direction finding collaborative positioning;

[0044] Figure 4 This is a simulation result diagram of the star-space-ground joint direction finding cross-positioning performance. DETAILED DESCRIPTION

[0045] The present invention is described in detail below in conjunction with specific embodiments.

[0046] The present invention provides a time-difference direction-finding collaborative positioning model based on the combination of star, sky and ground, which mainly includes 1 ground station, 1 unmanned aerial vehicle and 1 satellite. The positions of the unmanned aerial vehicle, satellite and ground reconnaissance station are known, and the position of the target is the unknown quantity to be determined. The positions of the measuring points, satellites and targets are selected, and usually the position coordinates are geocentric coordinates, and the origin of the geocentric coordinate system is at the center of the earth. When using a near-earth positioning system to find the direction of the target, it is necessary to establish a geocentric coordinate system with the unmanned aerial vehicle as the coordinate origin. In order to unify the coordinate system of the positioning system, the coordinates of the satellite and the ground station are added to the geocentric coordinate system with the unmanned aerial vehicle as the origin. The process is as follows: Figure 1 shown.

[0047] The specific steps are as follows:

[0048] Step 1: Assuming that the drone is the coordinate origin, based on the coordinate conversion method, the drone, satellite and ground station are converted from the geodetic coordinate system to the centroidal coordinate system with the drone as the origin; let the drone coordinates be s0 = (x0, y0, z0) = (0, 0, 0), and the satellite coordinates be s1 = (x1, y1, z1) T , the ground station position is s2=(x2,y2,z2) T , target position u=(x,y,z) T .

[0049] Step 2: The distance from the target to the satellite can be expressed as The distance from the target to the UAV can be expressed as The distance from the target to the ground station can be expressed as

[0050] The arrival time difference between the target arriving at the UAV and the satellite and ground station can be expressed as:

[0051]

[0052] Where c is the propagation speed of the electromagnetic wave signal. Considering that there will be certain errors in the positioning parameters during the measurement process, the observation equation of the arrival time difference TDOA can be expressed as:

[0053]

[0054] Among them, τ i is the measured value corresponding to the arrival time difference, is the measurement noise corresponding to the arrival time difference;

[0055] Step 3: The observation equation corresponding to the azimuth angle of the target reaching the drone (coordinate origin) can be expressed as:

[0056]

[0057] Among them, θ represents the measured value of the azimuth from the target to the UAV main station, v θ The corresponding measurement noise is obtained by linearizing the azimuth angle and substituting the drone main station as the coordinate origin. The observation equation of the azimuth angle can be simplified into the following linear form:

[0058] xtan(θ-v θ )-y=0

[0059] The spatial plane can be determined based on the three points. The direction-finding azimuth θ of the drone main station to the target can be used to obtain the direction-finding line of the geographic coordinate system with the drone as the origin, which can be expanded to three-dimensional space to obtain the direction-finding plane. From any three non-collinear points on the direction-finding plane, the direction-finding plane can be determined. Assume that the coordinates of the three points (in the coordinate system with the drone main station as the origin) are: s0 = (x0, y0, z0) = (0, 0, 0); s a =(x a ,y a ,z z )=(tanθ,1,0);s b =(x b ,y b ,z b )=(0,0,-1); Substitute the target position into the direction finding plane, and we have

[0060]

[0061] Step 4: Combine the direction-finding plane equation and the time-difference equation and solve the equations to obtain the location of the target source.

[0062] By expanding the direction-finding plane equation, we get

[0063] p x x+p y y+p z z=q

[0064] in

[0065] p x =(y a -y0)(z b -z0)-(z a -z0)(y b -y0)

[0066] p y =-(x a -x0)(z b -z0)+(z a -z0)(x b -x0)

[0067] p z =(x a -x0)(y b -y0)-(y a -y0)(x b -x0)

[0068] q=x0·p x +y0·p y +z0·p z

[0069] The simultaneous equations are

[0070]

[0071] Simulation test:

[0072] A typical star-space-ground joint positioning system model is constructed below, and the method of the present invention is compared with the traditional direction-finding cross-positioning algorithm to illustrate the feasibility and superiority of the method.

[0073] Simulation conditions:

[0074] Assume that the latitude and longitude of the drone are (100°, 29°, 2km), the latitude and longitude of the low-orbit satellite are (102°, 31°, 800km), and the location of the ground station is (100°, 29.1°, 0.1km). Assume that the drone is the main station, which is the origin of the centroidal coordinate system. The positions of each station in the centroidal coordinate system are as follows: Figure 2 shown.

[0075] The simulation experiment uses the root mean square error RMSE to measure the positioning performance of the algorithm, which is defined as follows:

[0076]

[0077] Where Q is the number of Monte Carlo experiments, and in this experiment, Q = 100; is the estimated position of the target in the qth Monte Carlo experiment.

[0078] Parameter setting: Taking practical factors into consideration, the direction finding error between the UAV and the ground station is set to 2°, the satellite direction finding error is set to 6°, the root mean square error of the time difference estimation between the satellite and the UAV is set to 50ns, and the root mean square error of the time difference estimation between the ground and the UAV is set to 20ns.

[0079] Positioning effect: combined Figure 3 and Figure 4 Under the same station layout, compared with the direction finding cross positioning algorithm, the satellite-ground joint time difference direction finding collaborative positioning algorithm has higher positioning accuracy in a larger range. At the same time, the positioning performance is better on the connection line of the near-ground base station.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A time difference direction finding collaborative positioning method based on star-space-ground joint, characterized in that: The following steps are involved: S1. Based on the coordinate conversion method, the coordinates of the UAV, satellite and ground station are converted from the geodetic coordinate system to the paracentric coordinate system with the UAV as the origin, and a star-space-ground integrated positioning model is established; The coordinates of the drone are s0 = (x0, y0, z0) = (0, 0, 0), and the coordinates of the satellite are s1 = (x1, y1, z1) T , the ground station coordinates are s2 = (x2, y2, z2) T , the radiation source target coordinates in three-dimensional space u=(x,y,z) T ; S2, the distance from the target to the satellite is The distance from the target to the drone is The distance from the target to the ground station is S3. The arrival time difference between the target UAV and the satellite and ground station is: Where c is the propagation speed of the electromagnetic wave signal; The observation equation of time difference of arrival TDOA is: Among them, τ i is the measured value corresponding to the arrival time difference, v τi is the measurement noise corresponding to the arrival time difference.

2. The method for time difference direction finding collaborative positioning based on star-space-ground combination according to claim 1 is characterized in that: The observation equation corresponding to the azimuth angle of the target reaching the UAV is: Among them, θ represents the measured value of the azimuth from the target to the UAV, v θ is the corresponding measurement noise; After linearizing the azimuth angle and substituting the master station as the origin of the coordinate system, the azimuth angle observation equation is simplified to: θ )-y=0.

3. The method for time difference direction finding collaborative positioning based on star-space-ground combination according to claim 1 is characterized in that: The method further includes steps for determining an estimated position of a target, the specific steps comprising: Determine the spatial plane based on the three points, the direction-finding azimuth θ of the drone to the target, obtain the direction-finding line of the geographic coordinate system with the drone as the origin, expand it to three-dimensional space, and obtain the direction-finding plane; randomly select three non-collinear points on the direction-finding plane to determine the direction-finding plane; Take the coordinates of three points in the coordinate system with the drone main station as the origin: s0=(x0,y0,z0)=(0,0,0); s a =(x a ,y a ,z z )=(tanθ,1,0); s b =(x b ,y b ,z b )=(0,0,-1); Substituting the target position into the direction finding plane, we have Expand the direction-finding plane equation to get p x x+p y y+p z z = q; in p x =(y a -y0)(z b -z0)-(z a -z0)(y b -y0) p y =-(x a -x0)(z b -z0)+(z a -z0)(x b -x0) p z =(x a -x0)(y b -y0)-(y a -y0)(x b -x0) q=x0·p x +y0·p y +z0·p z Combine the direction-finding plane equation ① and the lateral plane equation ②, solve the equation group, and obtain the position of the target source; The simultaneous equations are Solving the equation yields the estimated position of the target.

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