CN106908818B - Satellite joint navigation method - Google Patents
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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
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- 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 provides a satellite joint navigation method, which comprises the following steps: step S1, establishing a common ground trajectory constellation-based small satellite navigation system; s2, screening a Beidou satellite navigation system and a small satellite navigation system based on a back deletion model to form a satellite combined navigation system; and step S3, optimizing the satellite joint navigation system through parameter selection. The small satellite navigation system based on the common ground track constellation is designed, the Beidou satellite navigation system and the small satellite navigation system are organically combined through a back deletion model, and the main problems of quick space response and coverage enhancement are solved. When the Beidou satellite navigation system does not cover a target area, the rapid navigation service is realized through the small satellite navigation system designed by the common ground track constellation; and under the condition that the Beidou satellite navigation system in the focus area cannot meet the basic coverage or precision requirement, the positioning precision is improved and the satellite launching cost is reduced by the satellite combined navigation method.
Description
Technical Field
The invention relates to a design method of a navigation system, in particular to a design method of satellite joint navigation.
Background
The Global Navigation Satellite System (GNSS) mainly includes gps (Global Positioning System), beidou Satellite Navigation System bds (beidou Navigation System), GLONASS (GLONASS), and galileo Satellite Navigation System (galileo), and its main function is to provide all-weather three-dimensional coordinates, speed, and time information to users at any place on the earth surface or in the near-earth space. The development of the distributed satellite network, the differential enhancement, the inter-satellite link and other related technologies in the further development process can enable the navigation and positioning capacity of the satellite system for the region to reach the meter level, and the satellite system is widely applied to various aspects of life such as time service, navigation, positioning, weather, surveying and mapping, traffic and the like.
Meanwhile, the small satellite with the characteristics of low cost, easiness in deployment, short development period and the like becomes an important mode for demonstration and verification of new technology, new systems and new concepts. A multi-satellite low-orbit communication satellite constellation formed by the small satellites can provide unmanned data acquisition and battlefield short message communication capabilities, and the small satellites are introduced to effectively enhance signal coverage in the field of navigation communication, so that the robustness, coverage and positioning accuracy of the system are improved. In the concept innovation field of the small satellite system, projects such as a space system for quickly responding space and improving military combat effectiveness are successively provided, application scenes of the small satellite technology are further increased, a constellation system is formed by the one-rocket multi-satellite technology and the space station, and accordingly, the front line base layer fighters can quickly provide real-time battlefield data as required, and the dominant advantages of the battlefield under the condition of asymmetric information are obtained.
At present, the navigation service of a target area or the whole world can be realized only through a global navigation system, and in China, the Beidou satellite navigation system has the advantages of wide coverage range, long service life and all-weather work, but faces a plurality of challenges in the actual environment: firstly, the deployment time is long, and the cost is high; physical and electromagnetic attacks in space can cause serious damage to the functions of the satellite, and the communication and other functions of the satellite can stop service under various interference conditions. The system satellite which makes up the deficiency again has longer deployment time, and the emission cost is several times higher than that of a small satellite. Secondly, the high rail position resources are limited; all GEO geostationary satellites and IGSO satellites of GNSS are in high orbit, and scarce orbit resources become targets for competition in various countries. The number of satellites that can be transmitted is very limited. Thirdly, the satellite reuse rate is low; for satellite navigation systems such as GPS and BDS, the reuse rate of satellites is low, and besides the system can complete the designated tasks, the system can also combine with satellites in other systems to complete other functions, so that the satellite resources are prevented from being idle. Fourthly, the navigation precision is limited; for global coverage of GNSS, it is not enough to achieve high-precision navigation in local area, and for other BDSs that are not perfect or lack satellites, it is more necessary to assist other satellites to complete navigation in some blind spot areas.
The method can quickly assist a navigation satellite system, and the best choice for improving the coverage accuracy of a specific area is a low-orbit small satellite. The low-orbit small satellite has the characteristics of short deployment time, low cost, good performance, short development period and the like, and has the advantages of rich orbit resources and the like, but has some defects when being independently used for the construction of a navigation system, for example, the coverage range is limited, the number of the small satellites generally used for the low orbit is large, the range of ground coverage is limited due to the fact that the orbit is low, and if the area of a target area is large, the number of the required low-orbit small satellites is large, and the space waste can be generated.
Disclosure of Invention
The invention aims to solve the technical problem of providing a satellite combined navigation method which can be combined with a Beidou satellite navigation system and a small satellite navigation system, realize high-precision coverage on a specific area, and further realize the purposes of minimizing the design of the system and effectively improving the resource utilization rate.
Therefore, the invention provides a satellite joint navigation method, which comprises the following steps:
step S1, establishing a common ground trajectory constellation-based small satellite navigation system;
s2, screening a Beidou satellite navigation system and a small satellite navigation system based on a back deletion model to form a satellite combined navigation system;
and step S3, optimizing the satellite joint navigation system through parameter selection.
A further refinement of the invention is that said step S1 comprises the following sub-steps:
step S101, selecting a target area and a track period;
step S102, calculating a lower limit value N of the total number of navigation constellation satellites of the small satellite navigation system;
step S103, enumerating all constellation schemes suitable for being used as navigation constellations according to the lower limit value N of the total number of the navigation constellation satellites;
step S104, calculating the ascension difference delta omega between two adjacent orbital planes of each constellation scheme and the mean-anomaly angle difference △ M of adjacent satellites on the same orbital plane;
step S105, obtaining the optimal constellation inclination angle of each constellation scheme;
and S106, comparing the positioning performance of each constellation, and determining one constellation scheme as the small satellite navigation system through positioning accuracy verification.
The invention is further improved in that in the step S102, the formula is used
Calculating a lower limit value N of the total number of navigation constellation satellites of the small satellite navigation system, wherein theta is a half included angle between the circle centers of two adjacent satellites in the common ground track constellation and the center-of-earth connecting line; n is the number of movement circles of a fixed star intraday satellite around the earth, and n is an integer.
The invention is further improved in that in the step S104, the formula N is usedsΔΩ＝NeΔ ω or NsΔΩ-NeΔω＝Ne2k pi calculates the ascent and intersection declination difference delta omega between two adjacent orbital planes of each constellation scheme, wherein N issFor the number of movement turns of the minisatellite around the earth, NeIs the number of revolutions of the earth, and Δ ω is the relative phase of any two satellites located on different orbital planes.
A further refinement of the invention is that said step S105 comprises the following sub-steps:
step S1051, obtaining average coverage rate cov (i), average elevation angle El (i) and average positioning accuracy DOP (i) of each constellation scheme at different constellation inclination angles by utilizing STK modeling simulation;
step S1052, according to the formula w (i) ═ wcov×Cov(i)+wDOP×DOP(i)+wElX El (i) calculating a weight value W (i), wherein wcovIs the weight, w, of the average coverage cov (i)DOPWeight, w, of the mean positioning accuracy DOP (i)ElThe weight of the average elevation angle El (i);
step S1053, obtaining the constellation inclination angle i ' corresponding to the maximum weight value W (i ') when the maximum value is obtained through the weight value W (i), where the constellation inclination angle i ' is the optimal constellation inclination angle of the constellation scheme.
The further improvement of the present invention is that in step S106, the satellite connection number NOA, the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP and the vertical positioning accuracy VDOP of two or more test points at the optimal constellation inclination angle of each constellation scheme are simulated by STK, and then the average is made for the satellite connection number NOA, the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP and the vertical positioning accuracy VDOP of the two or more test points, and then the constellation scheme with the larger satellite connection number NOA and the smaller variance as well as the smaller geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP and the vertical positioning accuracy VDOP and the smaller variance is selected as the optimal constellation scheme; judging whether the lower limit value N of the total number of satellites of the optimal constellation scheme meets the positioning requirement through positioning accuracy verification, if so, taking the optimal constellation scheme as the small satellite navigation system, and ending; if not, the value of the lower limit value N of the total number of satellites is increased, and the step S103 is returned.
A further refinement of the invention is that said step S2 comprises the following sub-steps:
step S2011, defining a Beidou satellite selection matrix asThe dimension of the satellite is 1 multiplied by m, which means that m Beidou satellites can be used for covering a target area, and the ith Beidou satellite is selected
When the ith Beidou satellite is available but not selected for coverageDefining a microsatellite selection matrix as
Having a dimension of1 × M, indicating that a total of M microsatellites can be used to cover the target area, and that the jth microsatellite is selected
When the jth microsatellite is available but not selected for coverage
i and j are integers;
step S2012, the service time of the satellite is expanded according to the step length of 1 second and the time sequence, so that a service time matrix of the satellite can be obtained, the dimensionality is 1 multiplied by T, T is the period, and the service time matrix of all the satellites is
And
wherein L isBDIs a Beidou satellite service matrix, b ij1 represents that the ith Beidou satellite is available in the j time slot; l isLEORepresenting the moonlet service time matrix,/ij0 means that the ith microsatellite is not available in the j time slot.
In a further improvement of the present invention, in the step S3, optimization is implemented in the set of feasible satellite combinations according to the accuracy condition and the number of visible satellites, so as to obtain a final satellite combination solution.
In a further improvement of the present invention, in the step S3, the formula is used
Meets the requirement of multiple coverage on the target area, wherein theta belongs to R1*TTheta is a covering weight threshold matrix, and H belongs to R1*(m+M)，L∈R(m+M)*TH is a service matrix, L is the service matrix, R is a real number field, and the value is only 0 value or 1 value; i.e. R is a matrix with a value of 0 or 1.
Compared with the prior art, the invention has the beneficial effects that: a common-ground-track-constellation-based small satellite navigation system is designed, and a satellite combined navigation method for organically combining a Beidou satellite navigation system and the small satellite navigation system is realized through a back deletion model, so that the problems of quick space response and coverage enhancement are mainly solved. When the Beidou satellite navigation system does not cover a target area, the rapid navigation service is realized through a small satellite navigation system (basic navigation system) designed by a common ground track constellation; under the condition that a Beidou satellite navigation system in a focus area cannot meet basic coverage or precision requirements, the satellite combined navigation method is provided, and the satellite combined navigation method organically combining a small satellite and the Beidou is designed on the basis of the basic navigation system, so that the positioning precision is improved, the satellite launching cost is reduced, the minimized design of the navigation system is realized, and the resource utilization rate of the satellite combined navigation method and the satellite combined navigation system thereof is greatly improved.
Drawings
FIG. 1 is a schematic workflow diagram of one embodiment of the present invention;
FIG. 2 is a schematic diagram of a process flow for designing a microsatellite navigation system in accordance with one embodiment of the present invention;
fig. 3 is a schematic diagram of a workflow for calculating an optimal constellation tilt angle of a constellation scheme according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a satellite coverage bandwidth calculation according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a back-deletion model service time compensation according to an embodiment of the present invention;
fig. 6 is a simulation comparison diagram of the positioning accuracy DOP of different constellation schemes according to an embodiment of the present invention when the number P of orbital planes is 4 and the number S of satellites per orbital plane is 7;
fig. 7 is a diagram illustrating probability distribution simulation of the number NOA of satellite connections when the number P of orbital planes is 4 and the number S of satellites per orbital plane is 7 according to an embodiment of the present invention;
fig. 8 is a simulation comparison diagram of the positioning accuracy DOP of different constellation schemes according to an embodiment of the present invention when the number P of orbital planes is 7 and the number S of satellites per orbital plane is 4;
fig. 9 is a diagram showing a probability distribution simulation of the number NOA of satellite connections when the number P of orbital planes is 7 and the number S of satellites per orbital plane is 4 according to an embodiment of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
As shown in fig. 1 and fig. 2, the present embodiment provides a method for joint satellite navigation, including the following steps:
step S1, establishing a common ground trajectory constellation-based small satellite navigation system;
s2, screening a Beidou satellite navigation system and a small satellite navigation system based on a back deletion model to form a satellite combined navigation system; the satellite combined navigation system is a new heterogeneous navigation system formed by organically combining a Beidou satellite navigation system and a small satellite navigation system, and is a combined navigation system corresponding to the satellite combined navigation method;
and step S3, optimizing the satellite joint navigation system through parameter selection.
That is to say, the present example mainly includes two parts, the first part is to use a low orbit small satellite based on a common ground track constellation to construct a basic navigation system to realize navigation positioning calculation under the condition that no Beidou navigation satellite is available; and in the second part, when the Beidou satellite navigation system cannot meet the high-precision coverage for a specific area, a back Deletion Model provided by a heterogeneous navigation satellite network is constructed, and a back Deletion Model BTD (Back tracking Deletion Model) is utilized to realize organic combination of a small satellite navigation system (basic navigation system) and a Beidou satellite navigation system (BDS) to construct a satellite combined navigation method between a small satellite and a Beidou so as to obtain a navigation system corresponding to the satellite combined navigation method.
The microsatellite navigation system, also called a satellite basic navigation system, is based on the common ground trajectory constellation theory, and provides navigation services for a specific target area by using a minimum number of LEO microsatellites on the basis of meeting the requirements of required coverage rate and positioning accuracy, and the design and system establishment process are shown in fig. 2 and 3.
As shown in fig. 2, step S1 in this example includes the following sub-steps:
step S101, selecting a target area and a track period;
step S102, calculating a lower limit value N of the total number of navigation constellation satellites of the small satellite navigation system;
step S103, enumerating all constellation schemes suitable for being used as navigation constellations according to the lower limit value N of the total number of the navigation constellation satellites;
step S104, calculating the ascension difference delta omega between two adjacent orbital planes of each constellation scheme and the mean-anomaly angle difference △ M of adjacent satellites on the same orbital plane;
step S105, obtaining the optimal constellation inclination angle of each constellation scheme;
and S106, comparing the positioning performance of each constellation, and determining one constellation scheme as the small satellite navigation system through positioning accuracy verification.
Specifically, in step S101 in this example, an area that needs to be provided with navigation service, that is, a coverage area of a satellite is selected as a target area, the orbital height h of an LEO microsatellite is determined, and the orbital periods (which can be obtained according to the formula of universal gravitation) of all LEO microsatellites can be determined according to the orbital height h of the satellite.
In step S102 described in this example, the formula is used
Calculating a lower limit value N of the total number of navigation constellation satellites of the small satellite navigation system, wherein theta is a half included angle between the circle centers of two adjacent satellites in the common ground track constellation and the center-of-earth connecting line; n is the number of movement circles of a fixed star intraday satellite around the earth, and n is an integer.
According to the target area and the orbit period selected in the step S101, the calculation method of the lower limit value N of the total number of the navigation constellation satellites is different with different constellation types. In view of the launching operation and orbit control, a regression with orbit periods that are integer multiples of a sidereal day is selected hereThe orbit, and thus fig. 2, is also a small satellite navigation system (LEO small satellite navigation system) designed based on a co-terrestrial locus constellation with a regressive orbit or quasi-regressive orbit, the lower limit value N of the total number of navigation constellation satellites being represented by a formulaAn estimation is performed.
As shown in fig. 4: the orbit height h is the half height of the target area, then 2h is the wide band of the coverage zone, and S1 and S2 in fig. 4 respectively represent the subsatellite point positions of two satellites.
In step S103 of this embodiment, all constellation schemes suitable for serving as a navigation constellation of a small satellite navigation system are listed according to the lower limit N of the total number of navigation constellation satellites calculated in step S102.
In step S104 of this example, the ascent difference Δ Ω between two adjacent orbital planes of each constellation scheme in step S103 and the mean-anomaly angle difference △ M between adjacent satellites on the same orbital plane are calculated as follows:
co-ground orbit constellation with regressive or quasi-regressive orbits, with orbit period TsAnd the period of earth rotation TeSatisfies the formula NsTs＝NeTeIn the formula, NsThe number of movement circles of the small satellite around the earth; n is a radical ofeThe mean-near point angle difference △ M of adjacent satellites on the same orbital plane is calculated according to the following formula:
taking the difference between the different values.
In addition, two satellites located in different orbital planes have spatial positions satisfying the formula
In the formula, Δ ω is the relative phase of any two satellites located on different orbital planes; omegasAngular velocity of a satellite for a certain altitude; omegaeIs the rotational angular velocity of the earth.
Formula NsTs＝NeTeAnd
the co-ground trajectory constellation with regression orbits or quasi-regression orbits has the relation: n is a radical ofsΔΩ＝NeΔ ω or NsΔΩ-NeΔω＝Ne2k pi. if there are N satellites in the co-ground trajectory constellation, there may be N or 1 co-ground trajectories. Formula N should be satisfied when there is only one common ground trackeλ S and Ns＝μP+λNcIn the formula, mu is an integer; to minimize the regression period, λ is an integer and is typically taken to be 1; s is the number of satellites in each orbital plane, Nc∈[0,P-1]，NcIs a phase parameter for determining the phase difference between two adjacent track planes. P is the number of orbital planes, N is the minimum orbital height of the satellite when coverage performance is satisfiedcA maximum value needs to be taken.
For a constellation, the configuration of the constellation depends on the difference between the ascent points declination between two adjacent orbital planes Δ Ω and the difference between the approach points of adjacent satellites on the same orbital plane △ M, and the difference between the ascent points declination between two adjacent orbital planes Δ Ω and the difference between the approach points of adjacent satellites on the same orbital plane △ M can calculate the ascent point declination of the jth satellite on the ith orbital plane ΩijMean angle of approach M to the jth satellite in the ith orbital planeijThey satisfy the formula
And
wherein i is 0,1, …, P-1, j is 0,1, …, S-1, i and j are integers.
As shown in fig. 3, step S105 in this example includes the following sub-steps:
step S1051, using STK modeling to obtain constellation configuration of each constellation scheme, and obtaining average coverage rate cov (i), average elevation angle El (i) and average positioning accuracy DOP (i) of each constellation scheme at different constellation inclination angles through simulation;
step S1052, setting the different weights of the average coverage rate cov (i), the average elevation angle El (i) and the average positioning precision DOP (i) as wcov、wDOPAnd wEL. Then according to the formula w (i) ═ wcov×Cov(i)+wDOP×DOP(i)+wElX El (i) calculating a weight value W (i), wherein wcovIs the weight, w, of the average coverage cov (i)DOPWeight, w, of the mean positioning accuracy DOP (i)ElThe weight of the average elevation angle El (i);
step S1053, obtaining the constellation inclination angle i ' corresponding to the maximum weight value W (i ') when the maximum value is obtained through the weight value W (i), where the constellation inclination angle i ' is the optimal constellation inclination angle of the constellation scheme.
In step S106, the Number of satellite connections NOA (Number of Access), the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP, and the vertical positioning accuracy VDOP of two or more test points of each constellation scheme at the optimal constellation inclination angle are simulated by STK, and the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP, and the vertical positioning accuracy VDOP are collectively referred to as positioning accuracy or positioning accuracy DOP; and then averaging the satellite connection number NOA, the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP and the vertical positioning accuracy VDOP of the more than two test points.
Here, a larger value and a smaller variance of the number NOA of satellite connections indicates that the number of satellite connections is larger and stable. The smaller the values of the geometric positioning accuracy GDOP, the positional positioning accuracy PDOP, the horizontal positioning accuracy HDOP and the vertical positioning accuracy VDOP and the smaller the variance, the higher the positioning accuracy and the stability can be maintained. Therefore, the constellation configuration scheme with the best positioning performance is obtained by comparing the satellite connection number NOA, the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP and the vertical positioning accuracy VDOP of each constellation scheme. The constellation scheme with the larger satellite connection number NOA and the smaller variance, the smaller geometric positioning accuracy GDOP, the smaller position positioning accuracy PDOP, the smaller horizontal positioning accuracy HDOP and the vertical positioning accuracy VDOP and the smaller variance is selected as the optimal constellation scheme.
Finally, whether the lower limit value N of the total number of satellites of the optimal constellation scheme meets the positioning requirement is judged through positioning precision verification, if yes, the optimal constellation scheme is used as the small satellite navigation system, and the operation is finished; if not, the value of the lower limit N of the total number of satellites is increased, and the process returns to step S103, as shown in fig. 2.
That is, the STK is used to verify, from multiple aspects, the optimal constellation scheme with the lower limit N for the total number of satellites selected in step S106, including the number NOA of satellite connections, the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP, the vertical positioning accuracy VDOP, and the like, in the edge zone of the target area. Then, through the verification of the positioning precision, if the positioning requirement is not met, the value N needs to be increased, and the steps S103 to S106 are repeated; if the positioning requirement is satisfied, the constellation scheme selected in step S106 is the best constellation scheme that satisfies the requirement and has the least number of satellites, and the implementation process is shown in fig. 2.
The small satellite navigation system is a complete regional navigation system which consists of LEO small satellites and can independently provide navigation services, and the emergency navigation and positioning functions of blind spot regions can be realized through the one-arrow-multi-satellite technology.
In the foregoing, this example designs a basic navigation system based on a small satellite navigation system, and its main functions are to quickly respond to a designated area and implement coverage and navigation in the case of no available constellation. Although the Beidou satellite continuously emits and the global coverage capability is continuously enhanced, the number of visible satellites in certain areas is still small, and the coverage with higher precision is not enough.
In order to design an optimal satellite joint navigation method between a small satellite and a Beidou, which is also called a heterogeneous satellite network, a back Deletion Model (backspacing Deletion Model) is provided based on satellite service time. The back deletion model is a satellite constellation screening model, takes the minimum number of small satellites as a principle, and is used for screening the Beidou satellite and the basic navigation satellite to form an optimal combined navigation system under the conditions of meeting the coverage rate and the navigation precision, and finally finishing the area coverage function. The back-cut model mainly comprises three parts, and firstly, the example is based on the SOICC algorithm, which can refer to the following documents: dongrong in tangfu LEO satellite visibility problem study [ D ] national defense science and technology university, 2007. The SOICC algorithm is an orbital transfer intersection circle compensation algorithm, namely shift orbit intersection circle compensation, SOICC, so that the service time of each satellite is obtained, and a service time matrix of all satellites is formed. And then screening all schemes according to the coverage conditions to obtain a feasible scheme set. Finally, according to the precision condition and the number of visible satellites, a final satellite combination scheme is obtained, namely the joint navigation system where the satellite joint navigation method is located, and the principle of a back-deletion model algorithm is shown in fig. 5.
As shown in fig. 5, each satellite has a fixed service time period for a target region in a regression cycle, and the service state timeslot of each satellite when connected is recorded as 1, the invisible service state timeslot is 0, the timeslot duration is 1 second, the service state of each satellite is represented by an information service matrix of 1 × T dimension, and T is the regression cycle duration, and is a unit of second. For example, if a certain GEO Beidou satellite covers the south China sea area all weather, the matrix is an all-1 matrix. Placing all satellite service information in a matrix, wherein the dimension is M x T, M represents the number of satellites, and M is selected from M satellites1The compensation superposition is carried out on the service time by the satellites, each time slot is ensured to be covered by multiple times, and then M is carried out at the moment1The satellite combination scheme is the satellite combination scheme feasible in this example.
To mathematically represent the puncturing algorithm, this example first defines its associated variables, wherein the step S2 comprises the following sub-steps:
step S2011, defining a Beidou satellite selection matrix as
The dimension of the satellite is 1 multiplied by m, which means that m Beidou satellites can be used for covering a target area, and the ith Beidou satellite is selectedWhen the ith Beidou satellite is available but not selected for coverage
At the same time, define the microsatellite selection matrix as
The dimension is 1 × M, which means that a total of M small satellites can be used to cover the target area, and when the jth small satellite is selectedWhen the jth microsatellite is available but not selected for coverage
i and j are integers;
step S2012, the service time of the satellite is expanded according to the step length of 1 second and the time sequence, so that a service time matrix of the satellite can be obtained, the dimensionality is 1 multiplied by T, T is the period, the unit is second, and the service time matrices of all the satellites are
And
wherein L isBDIs a Beidou satellite service matrix, b ij1 represents that the ith Beidou satellite is available in the j time slot; l isLEORepresenting the moonlet service time matrix,/ij0 means that the ith microsatellite is not available in the j time slot. Then, correspondingly, b ij0 represents that the ith Beidou satellite is unavailable in the j time slot; l ij1 indicates that the ith microsatellite is available in the j slot.
In step S3 described in this example, in the set of feasible satellite combinationsAnd optimizing according to the precision condition and the number of visible satellites to obtain a final satellite combination scheme. That is, the parameter selection of step S3 is the accuracy condition and the number of visible satellites, and more specifically, the step S3 optimizes the satellite integrated navigation system by parameter selection, and actually has a formula for multiple coverage requirements for the target area
Wherein, theta is epsilon to R1*TAnd theta is the coverage weight threshold matrix, and the elements of the coverage weight threshold matrix are all theta.
Formula (II)The method is characterized in that a proper Beidou satellite and a small satellite of a basic navigation system are selected, so that a target area meets the coverage requirement, and H belongs to R1*(m+M)，L∈R(m+M)*TH is a service matrix, L is a service matrix, and R is a real number and takes a value of 0 or 1. When the available Beidou navigation satellite and the coverage weight threshold of the area are known, the satellite constellation scheme of the satellite combined navigation method can be calculated based on the back deletion model by combining the small satellite navigation system (basic navigation system).
In the software implementation process, the puncturing algorithm pseudo code of the puncturing model in this example is as follows:
1: an INPUT: m, Target area, propofol (0) null, H (0) null// feasible scheme and selection matrix null
2：OUTPUT：Hoptimization
3: l ← SOICC (M, M, Target area)// SIOCC algorithm calculates information service matrix
3: segment ← select (L)// dividing L into 4 segments by time, 5%, 15%, 25%, 45%
4：for i＜＝last segment do
5: proposal (i) No. Iookfor (ithsegment, H (i-1), L)// find a set of feasible satellite combinations
6: h (i) ← Backtrating (Proposal (i); L)// deleting redundant schemes to get optimized multiple H (i)
7：i＝i+1
8：end for
9：HoptimizationStir for Complex (H (i)// comparatively DOP, NOA, etc. to select the optimum H
Namely, after the basic parameters of the Beidou satellite navigation system and the small satellite navigation system are available in the target area, the available scheme set and the corresponding selection matrix are initialized. The satellite service information matrix is further calculated using the SOICC algorithm, and the regression period T is divided into 4 segments. And starting from the first section of the regression cycle, obtaining all combination schemes Proposal (i) in the previous section according to the information service matrix and the feasible satellite combination H (i-1) in the previous section, and removing unavailable schemes according to the coverage condition of the satellite combination schemes to obtain the feasible satellite combination H (i). And obtaining a feasible scheme combination until a complete regression cycle is traversed. Finally, comparing parameters such as positioning accuracy DOP, satellite connection number NOA and satellite number under a feasible scheme to select an optimal satellite scheme H in the satellite joint navigation methodoptimization。
In order to realize the rapid establishment of all-weather and high-precision positioning and Navigation services of a global Navigation Satellite system (gnss) to a focus area under a fault or emergency, the embodiment takes a Beidou Satellite Navigation system (BDS) as an example, and constructs a Satellite combined Navigation method based on the organic combination of a small Satellite Navigation system and the Beidou Satellite Navigation system aiming at a south sea area, thereby obtaining the Satellite combined Navigation system.
Based on a Beidou satellite navigation system and a small satellite navigation system, a target area is set to be a south sea area with north latitude of 0-20 degrees and east longitude of 106-124 degrees. In the design of the small satellite navigation system, in order to meet navigation requirements, at least 4-fold coverage is set in a target area. A minimum of 28 low orbit minisatellites with an altitude of 1681km are required for calculation. The possible constellation configurations are shown in table 1:
table 1 constellation scheme comparison table of N-28
P denotes the number of orbital planes and S denotes the number of satellites per orbital plane. From table 1, it can be seen that only P-7, S-4 and P-7 satisfy the requirement. After obtaining the optimal elevation angle (P-4, S-7, 9 degrees for the constellation, P-7, and 10 degrees for the constellation) under the condition of ensuring the coverage, the positioning accuracy factor (DOP) and the Number of visible satellites (NOA) are compared, as shown in fig. 6 to 9.
As can be seen from fig. 6 to 9, the constellation configuration of P-4 and S-7 has a lower DOP value and higher accuracy than P-7 and S-4, and the NOA distribution is more concentrated. So P-4 and S-7 are constellation schemes (constellation configurations) of the small satellite navigation system. The specific parameters are shown in table 2:
table 2 constellation parameter table with P-4 and S-7
| Ω(deg) | Mi1(deg) | Mi2(deg) | Mi3(deg) | Mi4(deg) | Mi5(deg) | Mi6(deg) | Mi7(deg) | |
| |
0 | 0 | 51.43 | 102.86 | 154.29 | 205.71 | 257.14 | 308.57 |
| Track plane2 | 90 | 0 | 51.43 | 102.86 | 154.29 | 205.71 | 257.14 | 308.57 |
| Track plane3 | 180 | 0 | 51.43 | 102.86 | 154.29 | 205.71 | 257.14 | 308.57 |
| Track plane4 | 270 | 0 | 51.43 | 102.86 | 154.29 | 205.71 | 257.14 | 308.57 |
Based on the small satellite navigation system, assume that m is 2 available beidou satellites in the target area, and set the coverage weight threshold value Θ to be 4. According to the back-deletion model, five feasible schemes are obtained in the embodiment, and the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP and the vertical positioning accuracy VDOP are compared, as shown in the following table 3, the five feasible schemes all meet the requirements that the coverage rate is one hundred percent and the number of visible satellites is more than 4.
Table 3 comparison table of feasible solutions of the satellite integrated navigation method according to this embodiment
As shown in table 3, the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP, and the vertical positioning accuracy VDOP of the solution 1 are all lower in value, and higher in accuracy than the other solutions, and the corresponding satellite numbers are 4,5, 6,7,8,9,10,11,13,14,17,20, and 24. The Beidou satellite system comprises two Beidou satellites, and a satellite selection matrix H is [110001111111101100100100010000 ]. L is an information service matrix with dimensions of 30 × T, and T604800 s. The satellite combined navigation method corresponds to the optimal minisatellite and Beidou, and specifically corresponds to satellites, wherein the orbit plane of plane1 is the 4 th, 5 th, 6 th and 7 th satellites, the orbit plane of plane2 is the 1 st, 2 th, 3 th, 4 th, 6 th and 7 th satellites, the orbit plane of plane3 is the 3 rd and 6 th satellites, the orbit plane of plane4 is the 2 nd satellite, and the orbit phase corresponding to each satellite is shown in table 2.
In conclusion, the embodiment designs a common ground track constellation-based small satellite navigation system, and realizes a satellite joint navigation method for organically combining a Beidou satellite navigation system and the small satellite navigation system through a back deletion model, and mainly solves the problems of quick space response and coverage enhancement. When the Beidou satellite navigation system does not cover a target area, the rapid navigation service is realized through a small satellite navigation system (basic navigation system) designed by a common ground track constellation; under the condition that a Beidou satellite navigation system in a focus area cannot meet basic coverage or precision requirements, the satellite combined navigation method is provided, and the satellite combined navigation method organically combining a small satellite and the Beidou is designed on the basis of the basic navigation system, so that the positioning precision is improved, the satellite launching cost is reduced, the minimized design of the navigation system is realized, and the resource utilization rate of the satellite combined navigation method and the satellite combined navigation system thereof is greatly improved.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (6)
1. A satellite joint navigation method is characterized by comprising the following steps:
step S1, establishing a common ground trajectory constellation-based small satellite navigation system;
s2, screening a Beidou satellite navigation system and a small satellite navigation system based on a back deletion model to form a satellite combined navigation system;
step S3, optimizing the satellite combined navigation system through parameter selection;
in the step S3, the satellite integrated navigation system passes through a formula
Obtaining the target region to meet the requirement of multiple coverage on the target region, wherein theta belongs to R1*TTheta is a covering weight threshold matrix, and H belongs to R1*(m+M)，L∈R(m +M)*TH is a service matrix, L is a service matrix, and R is a matrix with a value of 0 or 1;
in step S3, the parameters optimally selected by the joint satellite navigation system include positioning accuracy and coverage rate;
the microsatellite navigation system, also called a satellite basic navigation system, is based on the common ground trajectory constellation theory, and provides navigation service for a target area by using the minimum number of LEO microsatellites on the basis of meeting the requirements of required coverage rate and positioning accuracy, wherein the step S1 comprises the following sub-steps:
step S101, selecting a target area and a track period;
step S102, calculating a lower limit value N of the total number of navigation constellation satellites of the small satellite navigation system;
step S103, enumerating all constellation schemes suitable for being used as navigation constellations according to the lower limit value N of the total number of the navigation constellation satellites;
step S104, calculating the ascension difference delta omega between two adjacent orbital planes of each constellation scheme and the mean-anomaly angle difference △ M of adjacent satellites on the same orbital plane;
step S105, obtaining the optimal constellation inclination angle of each constellation scheme;
step S106, comparing the positioning performance of each constellation, and determining one constellation scheme as the small satellite navigation system through positioning accuracy verification;
the step S2 includes the following sub-steps:
step S201, obtaining service time of each satellite in a Beidou satellite navigation system and a small satellite navigation system according to an SOICC algorithm to form a service time matrix H of all satellites;
step S202, screening according to coverage conditions to obtain a set of feasible satellite combinations;
the step S201 includes the following substeps:
step S2011, defining a Beidou satellite selection matrix as
The dimension of the satellite is 1 multiplied by m, which means that m Beidou satellites can be used for covering a target area, and the ith Beidou satellite is selected
When the ith Beidou satellite is available but not selected for coverage
Defining a microsatellite selection matrix as
The dimension is 1 × M, which means that a total of M small satellites can be used to cover the target area, and when the jth small satellite is selectedWhen the jth microsatellite is available but not selected for coveragei and j are integers;
step S2012, the service time of the satellite is expanded according to the step length of 1 second and the time sequence, so that a service time matrix of the satellite can be obtained, the dimensionality is 1 multiplied by T, T is the period, and the service time matrix of all the satellites is
And
wherein L isBDIs a Beidou satellite service matrix, bij1 represents that the ith Beidou satellite is available in the j time slot; l isLEORepresenting the moonlet service time matrix,/ij0 means that the ith microsatellite is not available in the j time slot.
2. The joint satellite navigation method according to claim 1, wherein in step S102, the navigation is performed according to a formula
Calculating a lower limit value N of the total number of navigation constellation satellites of the small satellite navigation system, wherein theta is a half included angle between the circle centers of two adjacent satellites in the common ground track constellation and the center-of-earth connecting line; n is the number of movement circles of a fixed star intraday satellite around the earth, and n is an integer.
3. The method for joint satellite navigation according to claim 1, wherein in step S104, the formula N is usedsΔΩ＝NeΔ ω or NsΔΩ-NeΔω＝Ne2k pi calculates the ascent and intersection declination difference delta omega between two adjacent orbital planes of each constellation scheme, wherein N issFor the number of movement turns of the minisatellite around the earth, NeIs the number of revolutions of the earth, and Δ ω is the relative phase of any two satellites located on different orbital planes.
4. The joint satellite navigation method according to claim 1, wherein the step S105 comprises the following sub-steps:
step S1051, obtaining average coverage rate cov (i), average elevation angle El (i) and average positioning accuracy DOP (i) of each constellation scheme at different constellation inclination angles by utilizing STK modeling simulation;
step S1052, according to the formula w (i) ═ wcov×Cov(i)+wDOP×DOP(i)+wElX El (i) calculating a weight value W (i), wherein wcovIs the weight, w, of the average coverage cov (i)DOPWeight, w, of the mean positioning accuracy DOP (i)ElThe weight of the average elevation angle El (i);
step S1053, obtaining the constellation inclination angle i ' corresponding to the maximum weight value W (i ') when the maximum value is obtained through the weight value W (i), where the constellation inclination angle i ' is the optimal constellation inclination angle of the constellation scheme.
5. The satellite joint navigation method according to claim 1, wherein in step S106, the STK is used to simulate the satellite connection number NOA, the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP, and the vertical positioning accuracy VDOP of two or more test points at an optimal constellation inclination angle for each constellation, and then the average is performed on the satellite connection number NOA, the geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP, and the vertical positioning accuracy VDOP of the two or more test points, and then the constellation scheme with the larger satellite connection number NOA and the smaller variance, and the smaller geometric positioning accuracy GDOP, the position positioning accuracy PDOP, the horizontal positioning accuracy HDOP, and the vertical positioning accuracy VDOP, and the smaller variance is selected as the optimal constellation scheme; judging whether the lower limit value N of the total number of satellites of the optimal constellation scheme meets the positioning requirement through positioning accuracy verification, if so, taking the optimal constellation scheme as the small satellite navigation system, and ending; if not, the value of the lower limit value N of the total number of satellites is increased, and the step S103 is returned.
6. The satellite joint navigation method according to claim 1, wherein in step S3, optimization is performed according to the accuracy condition and the number of visible satellites in the set of feasible satellite combinations to obtain a final satellite combination solution.
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