CN107340529B - Satellite-borne frequency measurement positioning method, device and system - Google Patents
Satellite-borne frequency measurement positioning method, device and system Download PDFInfo
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- CN107340529B CN107340529B CN201710401402.6A CN201710401402A CN107340529B CN 107340529 B CN107340529 B CN 107340529B CN 201710401402 A CN201710401402 A CN 201710401402A CN 107340529 B CN107340529 B CN 107340529B
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- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/421—Determining position by combining or switching between position solutions or signals derived from different satellite radio beacon positioning systems; by combining or switching between position solutions or signals derived from different modes of operation in a single system
- G01S19/423—Determining position by combining or switching between position solutions or signals derived from different satellite radio beacon positioning systems; by combining or switching between position solutions or signals derived from different modes of operation in a single system by combining or switching between position solutions derived from different satellite radio beacon positioning systems
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Abstract
The invention discloses a satellite-borne frequency measurement positioning method, device and system. The method comprises the following steps: determining a common coverage area of beams of at least 2 frequency measurement satellites as a search area of a ground radiation source, and performing meshing on the search area according to longitude and latitude to obtain the position of each grid point; calculating a position vector of each grid point in the geocentric fixed connection coordinate system; calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system; calculating a frequency estimation value of each grid point according to the frequency measurement information of at least 2 frequency measurement satellites and the state matrix; and calculating an objective function of each grid point according to the frequency estimation value, and determining the position of the grid point corresponding to the maximum value of the objective function as the position estimation value of the ground radiation source. Compared with single-satellite frequency measurement positioning, the scheme of the invention can solve the ambiguity, improve the positioning precision and reduce the positioning time.
Description
Technical Field
The invention relates to the technical field of space-based radio positioning, in particular to a satellite-borne frequency measurement positioning method, device and system.
Background
The modern war is an information war, and the key for mastering the initiative of the war is whether the war situation can be sensed preferentially. The radio reconnaissance technology is one of the means for sensing the situation of wars, plays an important role in modern wars, particularly has the advantages of wide coverage range, high interception probability, flexible arrangement, high intelligence response speed, high cost-effectiveness ratio and the like, and becomes the competitive focus of all military and strong countries.
By utilizing the space-based radio reconnaissance technology, not only can the radio characteristic information and the information of the reconnaissance target be obtained, but also the reconnaissance target can be positioned and the activity rule of the reconnaissance target can be detected. By fusing the radio information and the position information of the target, more valuable military information can be provided to sense the war situation. Space-based radio positioning technology is one of the important technical requirements.
The space-based radio positioning technology can be divided into time difference positioning, frequency measurement positioning, phase difference measurement positioning, direction measurement positioning and combined composite positioning means according to the positioning means. Among them, frequency measurement positioning, i.e. the precise positioning of an object under investigation by means of its radio radiation characteristics, is the most common means. Particularly, single-satellite frequency measurement positioning has the characteristics of simple load detection, low requirement on the attitude of the platform and the like, can reduce the difficulty and emission cost of a positioning system, and is suitable for the positioning requirement of a small satellite (such as a pico-satellite).
However, when single-satellite frequency measurement positioning is adopted for positioning, two positioning points are finally determined, wherein one positioning point is the real position of a detection target, and the other positioning point is a false point, namely ambiguity exists, and positioning is not accurate. Because the ambiguity of the single-satellite frequency measurement positioning is an inherent defect, the ambiguity can not be resolved only by the single-satellite positioning system, and the ambiguity needs to be resolved by the cooperation of other information, that is, if the single-satellite frequency measurement positioning is not assisted by other information, the accurate positioning of the reconnaissance target can not be realized. Meanwhile, the single-satellite frequency measurement positioning needs a longer frequency measurement arc length to obtain satisfactory positioning accuracy, so that the positioning time is longer and the positioning efficiency is low.
Disclosure of Invention
In view of the problems that the single-satellite frequency measurement positioning in the prior art cannot realize accurate positioning of a reconnaissance target, the positioning time is long, and the positioning efficiency is low, the invention provides the satellite-borne frequency measurement positioning method, the satellite-borne frequency measurement positioning device and the satellite-borne frequency measurement positioning system, so as to solve or at least partially solve the problems.
According to one aspect of the invention, a satellite-borne frequency measurement positioning method is provided, and the method comprises the following steps:
step one, determining a common coverage area of beams of at least 2 frequency measurement satellites as a search area of a ground radiation source, and performing grid division on the search area according to longitude and latitude to obtain the position of each grid point;
calculating a position vector of each grid point in the geocentric fixed connection coordinate system according to the position of each grid point;
step three, calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of the at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system;
step four, calculating the frequency estimation value of the ground radiation source at each grid point according to the frequency measurement information of the at least 2 frequency measurement satellites to the ground radiation source and the state matrix of each grid point;
step five, calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source, and determining the frequency estimation value of the grid point corresponding to the maximum value of the normalized objective function as the frequency estimation value of the ground radiation source.
According to another aspect of the invention, there is provided a satellite borne frequency measurement positioning device, the device comprising:
the grid division unit is used for determining a common coverage area of beams of at least 2 frequency measurement satellites as a search area of a ground radiation source, and carrying out grid division on the search area according to the longitude and latitude to obtain the position of each grid point;
the position vector calculation unit is used for calculating the position vector of each grid point in the geocentric fixed connection coordinate system according to the position of each grid point;
the state matrix calculation unit is used for calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of the at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system;
a frequency estimation value calculation unit, configured to calculate a frequency estimation value of the ground radiation source at each grid point according to the frequency measurement information of the at least 2 frequency measurement satellites on the ground radiation source and the state matrix of each grid point;
and the position estimation unit is used for calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source, and determining the frequency estimation value of the grid point corresponding to the maximum value of the normalized objective function as the frequency estimation value of the ground radiation source.
According to a further aspect of the invention, there is provided a satellite borne frequency measurement positioning system comprising at least 2 frequency measurement satellites and a satellite borne frequency measurement positioning device as described above;
the at least 2 frequency measurement satellites respectively send position vectors, relative velocity vectors and frequency measurement information of a ground radiation source in a geocentric fixed connection coordinate system to the satellite-borne frequency measurement positioning device;
the satellite-borne frequency measurement positioning device determines a common coverage area of beams of the at least 2 frequency measurement satellites as a search area of the ground radiation source, and performs grid division on the search area according to longitude and latitude to obtain the position of each grid point; calculating the position vector of each grid point in the geocentric fixed connection coordinate system according to the position of each grid point; calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of the at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system; calculating a frequency estimation value of the ground radiation source at each grid point according to the frequency measurement information of the at least 2 frequency measurement satellites on the ground radiation source and the state matrix of each grid point; and calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source, and determining the frequency estimation value of the grid point corresponding to the maximum value of the normalized objective function as the frequency estimation value of the ground radiation source.
In summary, in the technical scheme of the invention, at least 2 frequency measurement satellites are utilized, and the common coverage area of the beams is determined as the search area of the ground radiation source, so that the blindness of the search area is reduced; then, carrying out grid division on the search area according to the longitude and latitude to obtain the position of each grid point, and calibrating the search area by using the positions of the grid points; then calculating the position vector of each grid point in the earth center fixed connection coordinate system according to the position of each grid point; calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system; calculating a frequency estimation value of the ground radiation source at each grid point according to frequency measurement information of at least 2 frequency measurement satellites to the ground radiation source and the state matrix of each grid point; and calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, and determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source. The invention utilizes the position vector and the relative velocity vector of at least 2 frequency measurement satellites and the frequency measurement information of the ground radiation source, can obtain enough frequency measurement data without longer frequency measurement arc length, realizes the positioning of the ground radiation source, and compared with the single-satellite frequency measurement positioning, the invention can not solve the defect of ambiguity, not only can solve the ambiguity, but also can improve the positioning precision and reduce the positioning time, and is very suitable for the positioning requirements of ground low-speed or static radiation source targets of a pico-satellite operation group with simple function and low cost.
Drawings
Fig. 1 is a schematic flow chart of a satellite-borne frequency measurement positioning method according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a position relationship between a frequency measurement satellite and a ground radiation source in a geocentric fixed coordinate system according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a satellite-borne frequency measurement positioning device according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a satellite-borne frequency measurement positioning system according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a satellite-borne frequency measurement positioning system according to another embodiment of the present invention;
fig. 6 is a positional relationship between a satellite subsatellite point trajectory and a ground radiation source in single-satellite frequency measurement positioning according to an embodiment of the present invention;
FIG. 7 is a diagram illustrating a distribution of normalized objective functions in single-satellite frequency measurement positioning according to an embodiment of the present invention;
FIG. 8 is a diagram of an anchor point of a single-satellite frequency measurement positioning according to an embodiment of the present invention;
fig. 9 is a positional relationship between a satellite subsatellite point trajectory and a ground radiation source in a two-satellite frequency measurement positioning according to an embodiment of the present invention;
FIG. 10 is a diagram illustrating a normalized objective function distribution in a two-satellite frequency measurement positioning according to an embodiment of the present invention;
fig. 11 is a schematic diagram of an anchor point for two-satellite frequency measurement positioning according to an embodiment of the present invention.
Detailed Description
The design idea of the invention is as follows: in order to fully exert the advantages of single-satellite frequency measurement positioning and make up for the defects of the single-satellite frequency measurement positioning, the invention provides a technical scheme for positioning a ground radiation source by adopting at least 2 frequency measurement satellites, the solved positioning result has no fuzzy problem, and the positioning is accurate; and enough data can be obtained for positioning without needing longer frequency measurement arc length, the positioning time is short, and the positioning efficiency is high. In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic flow chart of a satellite-borne frequency measurement positioning method according to an embodiment of the present invention. As shown in fig. 1, the method includes:
and step 110, determining a common coverage area of beams of at least 2 frequency measurement satellites as a search area of a ground radiation source, and performing grid division on the search area according to the longitude and latitude to obtain the position of each grid point.
In this embodiment, at least 2 satellites are needed for positioning the ground radiation source, so that at least 2 frequency detectors are needed for determining the search areaThe common coverage area of the beams of the stars is determined as the search area for the ground radiation source. And in the present embodiment, the position of each grid point is expressed in longitude and latitude, for example, the grid point
Wherein the x is a longitude, and the x is a longitude,
the latitude is.
And step 120, calculating a position vector of each grid point in the earth center fixed connection coordinate system according to the position of each grid point.
And step 130, calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system.
And step 140, calculating a frequency estimation value of the ground radiation source at each grid point according to the frequency measurement information of the ground radiation source of at least 2 frequency measurement satellites and the state matrix of each grid point.
And 150, calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source, and determining the frequency estimation value of the grid point corresponding to the maximum value of the normalized objective function as the frequency estimation value of the ground radiation source.
When single-satellite frequency measurement positioning is carried out, after a normalized objective function value is calculated, two normalized objective function peak values can be obtained, wherein one normalized objective function value is the normalized objective function value of the position of the ground radiation source, the other normalized objective function value is the normalized objective function value of the false point, the normalized objective function values are equivalent in size, and the false point cannot be distinguished from the real position of the radiation source depending on the size of the objective function values. The invention adopts data of at least 2 frequency measurement satellites, the positions of the ground radiation sources obtained by the at least 2 frequency measurement satellites are the same as or similar to the actual positions of the ground radiation sources, namely, the same ground radiation source position can be obtained, and the positions of the false points are different, so that after the data of the at least 2 frequency measurement satellites are used for calculating the normalized objective function value of each grid point, although two normalized objective function peak values can be obtained, the sizes of the two normalized objective function peak values are obviously different, the normalized objective function value corresponding to the false point is obviously smaller than the normalized objective function value corresponding to the ground radiation source position, and the finally obtained normalized objective function maximum value is unique, namely, the position of the ground radiation source is unique. The invention utilizes the position vector and the relative velocity vector of at least 2 frequency measurement satellites and the frequency measurement information of the ground radiation source, can obtain enough frequency measurement data without longer frequency measurement arc length, realizes the positioning of the ground radiation source, and compared with the single-satellite frequency measurement positioning, the invention can not solve the defect of ambiguity, not only can solve the ambiguity, but also can improve the positioning precision and reduce the positioning time, and is very suitable for the positioning requirements of ground low-speed or static radiation source targets of a pico-satellite operation group with simple function and low cost.
In an embodiment of the present invention, in step 110, specifically, the common coverage area of the beams of at least 2 frequency measurement satellites is determined as a first search area of the ground radiation source, the first search area is subjected to coarse grid division with a first preset step size, and a preliminary position estimation value of the ground radiation source is obtained through steps 120 to 150.
After obtaining the preliminary location estimate, the method shown in fig. 1 further includes: and determining a second search area of the ground radiation source by taking the preliminary position estimation value as a center, performing fine grid division on the second search area by a second preset step length smaller than the first preset step length, and repeating the steps from the second step to the fifth step to obtain an accurate position estimation value of the ground radiation source.
In this embodiment, the second preset step is smaller than the first preset step, so as to perform finer meshing on the second search area. In this embodiment, the first search area is first coarsely gridded, and then the preliminary estimation of the position of the ground radiation source is performed, and then the second search area of the ground radiation source is determined by using the preliminary position estimation value as the center, and the second search area is finely gridded by a second preset step length, so that the position of the ground radiation source is accurately estimated. On one hand, the calculation amount of the system can be reduced, the system resources are saved, the calculation speed is increased, and the positioning efficiency is further improved.
In one embodiment of the present invention, step 120 shown in FIG. 1 comprises:
simplifying the earth model as a regular sphere according to the position of each grid point
Calculating to obtain the position vector of each grid point in the earth center fixed connection coordinate systemComprises the following steps:
wherein λ isk、
Longitude and latitude, R, of grid points, respectivelyEDifferent values of k may represent different grid points for the radius of the earth.
FIG. 2 is a schematic diagram of a frequency measurement satellite and the ground under a fixed earth center coordinate system according to an embodiment of the present inventionThe position relation of the surface radiation source is shown schematically. As shown in FIG. 2, the simplified earth model is a regular sphere, the center of the regular sphere is the earth center, and a coordinate system S is fixedly connectedeIn one embodiment of the invention, the number of frequency measurement satellites is 2, respectively satellites S1And satellite S2In the earth-center-fixed coordinate system, the position vector of the ground radiation source P is
Satellite S1Is a position vector of
Satellite S2Is a position vector of
Wherein the content of the first and second substances,
the calculation method of (2) is as described above.
Because, it is known that the radiation frequency of the ground radiation source reaches the satellite S1And satellite S2Doppler frequency f1And f2Respectively as follows:
wherein the content of the first and second substances,is the angular velocity vector of the earth rotation, c is the speed of light, fpThe true radiation frequency of the ground radiation source. It can be shown that,
at the same time, since the ground radiation source is stationary or moving slowly, it is possible to operate the ground radiation source in a short timeIt can be approximated as a constant value of,
can be approximated as a zero vector, then the above equation can be simplified as:
wherein the content of the first and second substances,
if the frequency measurement satellite carries out acquisition at different moments, the frequency measurement satellite has
Wherein epsilon1i、ε2jAre respectively a satellite S1Satellite S2Random error (i.e., white gaussian noise) in the frequency measurement.
Writing the above formula in matrix form as:
wherein the content of the first and second substances,
from the above deduction, it can be known that the frequency measurement data measured by the frequency measurement satellite has an equation relation with the position vector, the relative velocity vector, and the position vector of the ground radiation source of the frequency measurement satellite.
If a satellite S is acquired1And satellite S2And obtaining a state matrix by using the position vectors, the relative velocity vectors and the position vectors of the ground radiation source at different moments, and then establishing a relation between the state matrix and frequency measurement information measured by the frequency measurement satellite through the formula.
Then, in one embodiment of the present invention, step 130 shown in FIG. 1 comprises:
receiving satellite S1And satellite S2Respectively obtaining satellites S according to the GPS data1And satellite S2Position vectors at different time instants
And relative velocity vector
Then there is a change in the number of,
wherein the content of the first and second substances,as a satellite S1The position vector at the i time instants,
as a satellite S1Relative velocity vectors at i instants;
as a satellite S2The position vector at the time instant j,
as a satellite S2Relative velocity vector at time j.
The state matrix of each grid point
Comprises the following steps:
where c is the speed of light.
The method step 140 shown in fig. 1 includes:
according to satellite S1And satellite S2Obtaining a frequency measurement matrix from the frequency measurement information of the ground radiation source
Wherein f is1i(i＝1，2，…，N)、f2j(j-1, 2, …, M) is satellite S1And satellite S2Information is measured for the frequency of the ground radiation source.
Calculating the frequency estimation value of the ground radiation source at each grid point according to the frequency measurement matrix and the state matrix of each grid point
In step 150, a normalized objective function of the ground radiation source at each grid point is calculated according to the frequency estimation value of the ground radiation source at each grid pointComprises the following steps:
the position of the grid point corresponding to the maximum value of the normalized objective function is then determined as the position estimate of the ground radiation source, and the frequency estimate of the grid point corresponding to the maximum value of the normalized objective function is determined as the frequency estimate of the ground radiation source.
The formula underlying this is:
and sigma is a grid point set obtained after the grid division of the search area.
This formula represents that the objective function is to be normalized
Maximum time of correspondence
As an estimate of the position of the radiation source
Corresponding thereto
As an estimate of the frequency of the radiation source
Thus, the position of the ground radiation source can be determined, and the radiation characteristic frequency of the ground radiation source can be obtained.
Fig. 3 is a schematic structural diagram of a satellite-borne frequency measurement positioning device according to an embodiment of the present invention. As shown in fig. 3, the satellite-borne frequency measurement positioning apparatus 300 includes:
the grid division unit 310 is configured to determine a common coverage area of beams of at least 2 frequency measurement satellites as a search area of a ground radiation source, and perform grid division on the search area according to longitude and latitude to obtain a position of each grid point;
and a position vector calculation unit 320, configured to calculate a position vector of each grid point in the centroid fixed coordinate system according to the position of each grid point.
And the state matrix calculation unit 330 is configured to calculate a state matrix of each grid point according to the position vector of at least 2 frequency measurement satellites in the geocentric fixed coordinate system, the relative velocity vector, and the position vector of each grid point.
And a frequency estimation value calculation unit 340, configured to calculate a frequency estimation value of the ground radiation source at each grid point according to the frequency measurement information of the ground radiation source for at least 2 frequency measurement satellites and the state matrix of each grid point.
A position estimating unit 350, configured to calculate a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determine a position of the grid point corresponding to a maximum value of the normalized objective function as a position estimation value of the ground radiation source, and determine a frequency estimation value of the grid point corresponding to a maximum value of the normalized objective function as a frequency estimation value of the ground radiation source.
In an embodiment of the present invention, the grid dividing unit 310 is specifically configured to determine a common coverage area of beams of at least 2 frequency measurement satellites as a first search area of a ground radiation source, perform coarse grid division of a first preset step length on the first search area, and obtain a preliminary position estimation value of the ground radiation source through a position vector calculating unit, a state matrix calculating unit, a frequency estimation value calculating unit, and a position estimating unit; and determining a second search area of the ground radiation source by taking the preliminary position estimation value as a center, performing fine grid division on the second search area by a second preset step length smaller than the first preset step length, repeating the second step to the fifth step to obtain an accurate position estimation value of the ground radiation source, and simultaneously obtaining a frequency estimation value of the ground radiation source corresponding to the accurate position estimation value.
In an embodiment of the invention, the position vector calculation unit 320 is adapted to simplify the earth model to a regular sphere according to the position of each grid pointComputingObtaining the position vector of each grid point in the earth center fixed connection coordinate system
Expressed as:
wherein λ isk、
Longitude and latitude, R, of grid points, respectivelyEThe radius of the earth.
In one embodiment of the invention, the number of frequency measurement satellites is 2, satellite S1 and satellite S2,
a state matrix calculation unit 330 for receiving the GPS data of the satellite S1 and the satellite S2, and obtaining the position vectors of the satellite S1 and the satellite S2 at different time points according to the GPS data
Sum velocity vector
Then there is
State matrix for each grid pointComprises the following steps:
wherein c is the speed of light;
a frequency estimation value calculation unit 340 for
Obtaining a frequency measurement matrix according to the frequency measurement information of the satellite S1 and the satellite S2 to the ground radiation source
Wherein f is1i(i＝1，2，…，N)、f2j(j ═ 1,2, …, M) frequency measurement information for the terrestrial radiation source for satellite S1 and satellite S2, respectively;
calculating the frequency estimation value of the ground radiation source according to the frequency measurement matrix of the ground radiation source at each grid point and the state matrix of each grid point
A position estimation unit 350 for calculating a normalized objective function of the ground radiation source at each grid point based on the frequency estimation values
Comprises the following steps:
fig. 4 is a schematic structural diagram of a satellite-borne frequency measurement positioning system according to an embodiment of the present invention. As shown in fig. 4, the satellite-borne frequency measurement positioning system comprises at least 2 frequency measurement satellites and a satellite-borne frequency measurement positioning device 300 shown in fig. 3.
And at least 2 frequency measurement satellites respectively send position vectors, relative velocity vectors and frequency measurement information of a ground radiation source in a geocentric fixed connection coordinate system to the satellite-borne frequency measurement positioning device.
The satellite-borne frequency measurement positioning device 300 determines a common coverage area of beams of at least 2 frequency measurement satellites as a search area of a ground radiation source, and performs grid division on the search area according to longitude and latitude to obtain the position of each grid point; calculating the position vector of each grid point in the geocentric fixed connection coordinate system according to the position of each grid point; calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system; calculating a frequency estimation value of the ground radiation source at each grid point according to frequency measurement information of at least 2 frequency measurement satellites to the ground radiation source and the state matrix of each grid point; and calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source, and determining the frequency estimation value of the grid point corresponding to the maximum value of the normalized objective function as the frequency estimation value of the ground radiation source.
In an embodiment of the present invention, the satellite-borne frequency measurement positioning device 300 can be applied to a ground operation control and data processing system, and is suitable for the ground radiation source positioning requirement of a small satellite (e.g., pico-nano satellite) battle group.
Fig. 5 is a schematic structural diagram of a satellite-borne frequency measurement positioning system according to another embodiment of the present invention. As shown in the figure, the satellite-borne frequency measurement positioning system comprises a satellite 1, a satellite 2 and a ground operation control and data processing system. The ground operation control and data processing system comprises a satellite-borne frequency measurement positioning device.
It should be noted that the embodiments of the apparatus shown in fig. 3 and the systems shown in fig. 4 and 5 are the same as the embodiments of the method shown in fig. 1, and the detailed description is given above and will not be repeated here.
In order to make the technical effect of the present invention more obvious, the following description will be made by comparing the single-satellite frequency measurement positioning with the simulation result of the technical scheme of the present invention. In a simulation experiment, the technical scheme of the invention adopts double-star frequency measurement positioning.
The satellite orbit of the single-satellite frequency measurement positioning system is a sun synchronous orbit with the height of 500km, the width of a beam covering the ground by a detection antenna is 120 degrees, a static radiation source exists on the ground, and the position relationship between the satellite subsatellite point track and the radiation source is shown in figure 6.
The satellite position self-positioning error is 5m (1 sigma), the speed self-positioning error is 0.1m/s (1 sigma), the frequency measurement random error is 1kHz (1 sigma), the observation time of the satellite for detecting and receiving radio signals is 200s, 1s gives a frequency measurement result, and the radiation frequency of a ground radiation source is 2.7 GHz. Through simulation calculation, a distribution diagram of a normalized objective function in single-satellite frequency measurement positioning provided by an embodiment of the invention in fig. 7 can be obtained. As shown in fig. 7, the normalized objective function has two peaks and is relatively close, one of which is an estimate of the radiation source location and the other of which is a ghost point. The false point is an inherent phenomenon of a single-satellite frequency measurement positioning system and can be removed only by depending on other auxiliary information. The specific positioning result is shown in fig. 8, two positioning points of single-satellite frequency measurement positioning are respectively located on the left side and the right side of a satellite subsatellite point track, positioning point 1 is relatively close to the actual position of a ground radiation source, positioning point 2 is a false point, a radiation source frequency estimation value corresponding to positioning point 1 is 2.700001723GHz, and a radiation source frequency estimation value corresponding to positioning point 2 is 2.699999825 GHz.
In the technical scheme of the invention, a satellite is additionally arranged on the basis of a single satellite to form a double-satellite frequency measurement positioning system. The newly added satellite orbit is still a sun synchronous orbit with the height of 500km, and the width of the beam covering the ground by the detecting and receiving antenna is still 120 degrees. The right ascension and the phase angle of the rising point of the two-star orbit are both different by 2 degrees, and the position relationship between the two-star lower point trajectory and the radiation source is shown in fig. 9. Other simulation conditions are the same as those of the single-satellite frequency measurement positioning system. Through simulation calculation, a normalized objective function of the two-star frequency measurement positioning can be obtained as shown in fig. 10. It can be seen from the figure that although there are two peaks in the normalized objective function, one of them is very small relative to the other, so there are no ghost points, and the maximum peak is an estimate of the position of the ground radiation source. Specific positioning results as shown in fig. 8, there is only one positioning result, which is located near the true position of the radiation source, and the corresponding estimated value of the radiation source frequency is 2.700001751 GHz.
And then a Monto-Carlo method is adopted to respectively analyze the positioning errors of the single-satellite and double-satellite frequency measurement positioning systems. The observation time of single-satellite detecting and receiving radio signals is 200s, 150s, 100s and 50s, the observation time of double-satellite simultaneously detecting and receiving radio signals is 200s, 150s, 100s and 50s, 1000 times of Monto-Carlo simulation calculation is carried out, and the statistical positioning error result is shown in Table 1.
TABLE 1 statistical results of positioning error (1 sigma) of single-and double-star frequency measurement positioning system
As can be seen from table 1: under the condition of the same observation time, the double-star frequency measurement positioning precision is superior to the single-star frequency measurement positioning precision; under the condition of the same positioning precision, the positioning time required by the double-satellite frequency measurement positioning is shorter than that required by the single satellite; after the positioning time of the single-satellite frequency measurement positioning is less than 100s, the positioning accuracy is rapidly deteriorated, and after the positioning time of the double-satellite frequency measurement positioning is less than 50s, the positioning accuracy is rapidly deteriorated, namely the stability of the double-satellite frequency measurement positioning system is better.
In summary, in the technical scheme of the invention, at least 2 frequency measurement satellites are utilized, and the common coverage area of the beams is determined as the search area of the ground radiation source, so that the blindness of the search area is reduced; then, carrying out grid division on the search area according to the longitude and latitude to obtain the position of each grid point, and calibrating the search area by using the positions of the grid points; then calculating the position vector of each grid point in the earth center fixed connection coordinate system according to the position of each grid point; calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system; calculating a frequency estimation value of the ground radiation source at each grid point according to frequency measurement information of at least 2 frequency measurement satellites to the ground radiation source and the state matrix of each grid point; and calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, and determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source. The invention utilizes the position vector and the relative velocity vector of at least 2 frequency measurement satellites and the frequency measurement information of the ground radiation source, can obtain enough frequency measurement data without longer frequency measurement arc length, realizes the positioning of the ground radiation source, and compared with the single-satellite frequency measurement positioning, the invention can not solve the defect of ambiguity, not only can solve the ambiguity, but also can improve the positioning precision and reduce the positioning time, and is very suitable for the positioning requirements of ground low-speed or static radiation source targets of a pico-satellite operation group with simple function and low cost.
While the foregoing is directed to embodiments of the present invention, other modifications and variations of the present invention may be devised by those skilled in the art in light of the above teachings. It should be understood by those skilled in the art that the foregoing detailed description is for the purpose of better explaining the present invention, and the scope of the present invention should be determined by the scope of the appended claims.
Claims (10)
1. A satellite-borne frequency measurement positioning method is characterized by comprising the following steps:
step one, determining a common coverage area of beams of at least 2 frequency measurement satellites as a search area of a ground radiation source, and performing grid division on the search area according to longitude and latitude to obtain the position of each grid point;
calculating a position vector of each grid point in the geocentric fixed connection coordinate system according to the position of each grid point;
step three, calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of the at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system;
step four, calculating the frequency estimation value of the ground radiation source at each grid point according to the frequency measurement information of the at least 2 frequency measurement satellites to the ground radiation source and the state matrix of each grid point;
step five, calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source, and determining the frequency estimation value of the grid point corresponding to the maximum value of the normalized objective function as the frequency estimation value of the ground radiation source.
2. The method of claim 1, wherein in the first step, a common coverage area of the beams of the at least 2 frequency measurement satellites is determined as a first search area of the terrestrial radiation source, the first search area is subjected to coarse grid division of a first preset step size, and a preliminary position estimation value of the terrestrial radiation source is obtained through the second step to the fifth step;
the method further comprises the following steps:
and determining a second search area of the ground radiation source by taking the preliminary position estimation value as a center, carrying out fine grid division on the second search area by a second preset step length smaller than the first preset step length, and repeating the steps from the second step to the fifth step to obtain an accurate position estimation value of the ground radiation source.
3. The method of claim 2, wherein step two comprises:
simplifying the earth model as a regular sphere according to the position of each grid pointCalculating to obtain the position vector of each grid point in the earth center fixed connection coordinate system
Comprises the following steps:
wherein λ isk、Respectively longitude and latitude, R of the grid pointEThe radius of the earth.
4. The method of claim 3, wherein the number of frequency measurement satellites is 2, satellite 1 and satellite 2, respectively, and the third step comprises:
receiving the GPS data of the satellite 1 and the satellite 2, and respectively obtaining the position vectors r of the satellite 1 and the satellite 2 at different moments according to the GPS data1i、r2jAnd a relative velocity vector v1i、v2jThen there is
u1pi＝(rp-r1i)/||rp-r1i|| i＝1,2,…,N
u2pj＝(rp-r2j)/||rp-r2j|| j＝1,2,…,M
g1i(rp)＝1+u1pi·v1i/c i＝1,2,…,N
g2j(rp)＝1+u2pj·v2j/c j＝1,2,…,M
State matrix G for each grid pointkComprises the following steps:
wherein c is the speed of light, rpAnd the position vector of the ground radiation source in the earth center fixed connection coordinate system is obtained.
5. The method of claim 4, wherein the fourth step comprises:
obtaining a frequency measurement matrix F according to the frequency measurement information of the satellite 1 and the satellite 2 to the ground radiation source:
F＝[f11,f12,…,f1N,f21,f22,…,f2M]T
wherein f is1i(i＝1,2,…,N)、f2j(j ═ 1,2, …, M) frequency measurement information for satellite 1 and satellite 2 for the terrestrial radiation source, respectively;
calculating the frequency estimation value of the ground radiation source at each grid point according to the frequency measurement matrix and the state matrix of each grid point
In the fifth step, a normalized objective function of the ground radiation source at each grid point is calculated according to the frequency estimation value of the ground radiation source at each grid point
Comprises the following steps:
6. a satellite-borne frequency measurement positioning device, the device comprising:
the grid division unit is used for determining a common coverage area of beams of at least 2 frequency measurement satellites as a search area of a ground radiation source, and carrying out grid division on the search area according to the longitude and latitude to obtain the position of each grid point;
the position vector calculation unit is used for calculating the position vector of each grid point in the geocentric fixed connection coordinate system according to the position of each grid point;
the state matrix calculation unit is used for calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of the at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system;
a frequency estimation value calculation unit, configured to calculate a frequency estimation value of the ground radiation source at each grid point according to the frequency measurement information of the at least 2 frequency measurement satellites on the ground radiation source and the state matrix of each grid point;
and the position estimation unit is used for calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source, and determining the frequency estimation value of the grid point corresponding to the maximum value of the normalized objective function as the frequency estimation value of the ground radiation source.
7. The apparatus of claim 6,
the grid division unit is specifically configured to determine a common coverage area of beams of the at least 2 frequency measurement satellites as a first search area of the ground radiation source, perform coarse grid division of a first preset step length on the first search area, and obtain a preliminary position estimation value of the ground radiation source through a position vector calculation unit, a state matrix calculation unit, a frequency estimation value calculation unit, and a position estimation unit; and determining a second search area of the ground radiation source by taking the preliminary position estimation value as a center, carrying out fine grid division on the second search area by a second preset step length smaller than the first preset step length, repeating the steps from the second step to the fifth step to obtain an accurate position estimation value of the ground radiation source, and simultaneously obtaining a frequency estimation value of the ground radiation source corresponding to the accurate position estimation value.
8. The apparatus of claim 6,
the position vector calculation unit is used for simplifying the earth model into a regular sphere according to the position of each grid pointCalculating to obtain the position vector of each grid point in the earth center fixed connection coordinate system
Expressed as:
wherein λ isk、
Respectively longitude and latitude, R of the grid pointEThe radius of the earth.
9. The apparatus of claim 8, wherein the number of frequency measurement satellites is 2, satellite 1 and satellite 2 respectively,
the state matrix calculation unit is used for receiving the GPS data of the satellite 1 and the satellite 2 and respectively obtaining the position vectors r of the satellite 1 and the satellite 2 at different moments according to the GPS data1i、r2jAnd a relative velocity vector v1i、v2jThen there is
u1pi＝(rp-r1i)/||rp-r1i|| i＝1,2,…,N
u2pj＝(rp-r2j)/||rp-r2j|| j＝1,2,…,M
g1i(rp)＝1+u1pi·v1i/c i＝1,2,…,N
g2j(rp)＝1+u2pj·v2j/c j＝1,2,…,M
State matrix G for each grid pointkComprises the following steps:
wherein c is the speed of light, rpThe position vector of the ground radiation source in the earth center fixed connection coordinate system is obtained;
the frequency estimation value calculation unit is used for
Obtaining a frequency measurement matrix F according to the frequency measurement information of the satellite 1 and the satellite 2 to the ground radiation source:
F＝[f11,f12,…,f1N,f21,f22,…,f2M]T
wherein f is1i(i＝1,2,…,N)、f2j(j ═ 1,2, …, M) frequency measurement information for satellite 1 and satellite 2 for the terrestrial radiation source, respectively;
calculating a frequency estimation value of the ground radiation source according to the frequency measurement matrix and the state matrix of each grid point
The position estimation unit is used for calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid pointComprises the following steps:
10. a satellite-borne frequency measurement positioning system, characterized in that the system comprises at least 2 frequency measurement satellites and the satellite-borne frequency measurement positioning device according to any one of claims 6-9;
the at least 2 frequency measurement satellites respectively send position vectors, relative velocity vectors and frequency measurement information of a ground radiation source in a geocentric fixed connection coordinate system to the satellite-borne frequency measurement positioning device;
the satellite-borne frequency measurement positioning device determines a common coverage area of beams of the at least 2 frequency measurement satellites as a search area of the ground radiation source, and performs grid division on the search area according to longitude and latitude to obtain the position of each grid point; calculating the position vector of each grid point in the geocentric fixed connection coordinate system according to the position of each grid point; calculating a state matrix of each grid point according to the position vector, the relative velocity vector and the position vector of each grid point of the at least 2 frequency measurement satellites in the geocentric fixed connection coordinate system; calculating a frequency estimation value of the ground radiation source at each grid point according to the frequency measurement information of the at least 2 frequency measurement satellites on the ground radiation source and the state matrix of each grid point; and calculating a normalized objective function of the ground radiation source at each grid point according to the frequency estimation value of the ground radiation source at each grid point, determining the position of the grid point corresponding to the maximum value of the normalized objective function as the position estimation value of the ground radiation source, and determining the frequency estimation value of the grid point corresponding to the maximum value of the normalized objective function as the frequency estimation value of the ground radiation source.
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