Cluster distributed pulsar autonomous navigation system and control method thereof
阅读说明：本技术 一种集群分布式脉冲星自主导航系统及其控制方法 (Cluster distributed pulsar autonomous navigation system and control method thereof ) 是由 李璟璟 胡慧君 王文丛 宋娟 万胜伟 徐延庭 邵思霈 程显光 于 2020-11-27 设计创作，主要内容包括：本发明涉及空间飞行器脉冲星自主导航技术领域,具体涉及一种集群分布式脉冲星自主导航系统及其控制方法。包括若干集群分布式布局的卫星,所述卫星上设置有脉冲星探测器载荷、星间链路载荷、星敏感器载荷及导航计算模块。本发明提供了一套新的脉冲星自主导航系统,能够以集群分布的方式实现卫星自主导航。通过星间链路测距和星光角距观测的方式实现了卫星之间光子序列的折算,从而能够等效实现脉冲星大面积观测阵列的合成。突破了单卫星脉冲星导航方式卫星平台对探测器面积的制约。系统能够有效利用各种类型的卫星,即使是普通卫星也可通过在其上搭载本发明中的载荷,灵活接入集群导航系统,实现集群脉冲星自主导航。(The invention relates to the technical field of pulsar autonomous navigation of spacecraft, in particular to a cluster distributed pulsar autonomous navigation system and a control method thereof. The satellite comprises a plurality of clustered and distributed satellites, wherein a pulsar detector load, an inter-satellite link load, a star sensor load and a navigation calculation module are arranged on each satellite. The invention provides a set of novel pulsar autonomous navigation system which can realize satellite autonomous navigation in a cluster distribution mode. The conversion of photon sequences among satellites is realized through inter-satellite link ranging and star light angular distance observation, so that the synthesis of a pulsar large-area observation array can be equivalently realized. The restriction of a single satellite pulsar navigation mode satellite platform on the area of the detector is broken through. The system can effectively utilize various types of satellites, and even common satellites can be flexibly accessed to the cluster navigation system by carrying the load on the system, so that autonomous navigation of the cluster pulsar is realized.)
1. A cluster distributed pulsar autonomous navigation system is characterized in that: the satellite comprises a plurality of clustered and distributed satellites, wherein a pulsar detector load, an inter-satellite link load, a star sensor load and a navigation calculation module are arranged on each satellite.
2. The clustered distributed pulsar autonomous navigation system according to claim 1, wherein: the pulsar detector load comprises a first rotary table, a photon probe, a first signal amplifying and collecting circuit, a pulsar tracking module and a photon sequence coding module.
3. The clustered distributed pulsar autonomous navigation system according to claim 2, wherein: the pulsar tracking module comprises:
the pulsar database is used for storing pulsar star map information serving as a navigation source;
and the pulsar rotary table control submodule is connected with the pulsar database and used for calculating the rotation angle of the first rotary table according to the satellite position estimated value and the pulsar position so as to drive the first rotary table to rotate, so that the pulsar to be detected is always in the visual field of the photon probe.
4. The clustered distributed pulsar autonomous navigation system according to claim 1, wherein: the star sensor load comprises a second rotary table, an optical probe, a second signal amplifying and collecting circuit, a star map matching module and a star map angular distance generating module.
5. The clustered distributed pulsar autonomous navigation system according to claim 4, wherein: the star map matching module comprises:
the star map database is used for storing star map information of background stars;
and the star sensor rotating table control submodule is connected with the star map database and is used for controlling the second rotating table to rotate so as to enable the main star or the relay star establishing the inter-star link and more than 2 background fixed stars stored in the star map database to be always positioned in the visual field of the optical probe.
6. The clustered distributed pulsar autonomous navigation system according to claim 1, wherein: the navigation computation module includes:
the cluster satellite pulsar observation task dynamic planning unit is used for dynamically calculating and distributing the observation tasks of each satellite in the cluster to pulsars according to the specific information of inter-satellite links, orbits and attitude estimation of the satellite cluster;
the photon sequence conversion unit is used for converting the photon sequence at the auxiliary star position to the main star position;
and the TOA extraction and navigation resolving unit is used for processing all photon sequences collected by the main satellite, comparing the photon sequences with standard pulsar data information, giving TOA information and performing navigation resolving by using the TOA information.
7. The clustered distributed pulsar autonomous navigation system according to claim 6, wherein: the photon sequence conversion unit also comprises a relative Doppler frequency shift compensation subunit, wherein the relative Doppler frequency shift compensation subunit is used for calculating the relative speed between satellites by using the inter-satellite distance information and the unit position vector information of the observed satellite, and further compensating the relative Doppler frequency shift by using the relative speed.
8. A control method of a cluster distributed pulsar autonomous navigation system is characterized by comprising the following steps: the method comprises the following steps:
s1, constructing a cluster distributed satellite system, selecting any satellite with low, medium and high orbits in the earth space, and establishing connection between the satellites through inter-satellite link loads;
s2, initializing a system, sharing the position, speed and attitude estimation information of each satellite through an inter-satellite link, and selecting one satellite as a main satellite and the rest satellites as auxiliary satellites;
s3, selecting navigation pulsar, wherein the main star selects a certain number of pulsars from a pulsar database as navigation observation objects;
s4, observation task allocation, wherein the main satellites dynamically group in the satellite motion process according to the visibility of each satellite to the pulsar, so that each group of satellites optimally observes the target pulsar;
s5, information observation, namely observing a main star or a relay star and more than two background fixed stars by the auxiliary star by using the star sensor load to obtain a starlight angular distance; observing a target pulsar by using a pulsar detector load to obtain the photon sequence information of the pulsar, and sending the obtained information to a main star through an inter-satellite link;
s6, information is collected, and a photon sequence conversion unit of the main satellite aligns the information sent by the auxiliary satellites and the distance measurement information between each auxiliary satellite and the distance measurement information obtained through inter-satellite link carriers in a difference mode to form tabular information;
s7, geometric distance compensation and conversion, namely performing compensation and conversion on the geometric delay of the photon sequence caused by the distance between the satellites;
s8, compensating relative Doppler frequency shift, namely compensating the relative Doppler frequency shift caused by different satellite speeds;
s9, performing navigation positioning calculation on the main satellite, calculating the TOA value of the main satellite according to the photon sequence detected by the main satellite and the photon sequence completed by compensation conversion from the auxiliary satellite, correcting the last position estimation according to the TOA by utilizing a Newton iteration method, and completing navigation positioning calculation on the main satellite when the algorithm is converged;
s10, auxiliary satellite navigation positioning, wherein the main satellite distributes navigation positioning results to each auxiliary satellite through an inter-satellite link, and each auxiliary satellite can further calculate to obtain navigation positioning information of the main satellite by combining high-precision relative navigation positioning information which is given by the inter-satellite link and is relative to the main satellite.
9. The method of claim 8, wherein the method comprises: the specific method of the geometric distance compensation conversion is as follows:
s1, converting the projection of the inter-satellite distance to the pulsar direction according to the following formula:
wherein l3The distance between the main satellite and the auxiliary satellite is projected in the direction of the pulsar;
l0giving an inter-satellite distance for an inter-satellite link;
α1and alpha2Observing starlight angular distances formed by 2 fixed stars and a main star or a relay star at the auxiliary star position, which are respectively given by the star sensor;
α3the included angle between a certain fixed star of the two fixed stars and the pulsar is a known quantity according to the ephemeris;
theta is a high-low angle formed by a connecting line of the main satellite and the auxiliary satellite and the epsilon plane;
is the coordinate system rotation angle;
s2, when l3After the calculation is finished, converting the time of the photons from the auxiliary satellite to the main satellite:
wherein v is0The speed of the primary or relay satellite;
t is the time difference of the photon from the secondary star to the primary star;
and c is the speed of light.
10. The method of claim 8, wherein the method comprises: the specific method for compensating the relative Doppler frequency shift comprises the following steps:
s1, estimating relative speed by utilizing inter-star ranging and star sensor observation:
wherein l0Is the inter-satellite distance;
a unit vector of a satellite obtained by measurement of the star sensor;
is the distance between the starsProjection of (2);
is the satellite relative velocity;
dt is a calculus writing method and represents a tiny variable;
interp represents the difference calculation;
the satellite relative speed at the required moment;
s2, obtaining the relative velocity projection in the pulsar direction by using the following formulaComprises the following steps:
s3, compensating the relative Doppler frequency shift in the pulsar direction:
wherein f isd1Is the satellite doppler shift in the direction of the pulsar;
f is the pulsar natural frequency;
the velocity of the satellite in the direction of the pulsar;
the speed of the primary or relay satellite in the direction of the pulsar;
f'd1for projecting by relative velocityA calculated relative doppler shift; wherein the content of the first and second substances,
fd0doppler shift of the dominant star;
and c is the speed of light.
Technical Field
The invention relates to the technical field of pulsar autonomous navigation of spacecraft, in particular to a cluster distributed pulsar autonomous navigation system and a control method thereof.
Background
The pulsar autonomous navigation technology is a new means for realizing autonomous navigation of a spacecraft. Because the signals emitted by pulsar in the universe are generally weak, in order to ensure that the pulsar detector collects enough photon information to realize navigation calculation, the spacecraft can increase the detection time of the pulsar on one hand and increase the detector area on the other hand. However, for the limited spacecraft resources, it is extremely expensive to add a large enough area, and the long-time detection obviously also results in a low frequency of navigation and positioning information. In addition, when the aircraft is positioned geometrically, pulsar observation in 3 directional dimensions is required simultaneously, which requires a probe with 3 probes.
In recent years, scholars and technicians at home and abroad expand autonomous navigation modes of single aircraft pulsar and realize an autonomous navigation method of multiple aircraft pulsar. According to the method, on the basis that the pulsar autonomous navigation is realized by the original single aircraft, the navigation result of each aircraft is further optimized, and the autonomous navigation precision of each aircraft is further improved. Obviously, this type of method is still a single-aircraft navigation in nature, and it still cannot avoid the problems of detection time, detection area and detection dimension of single-aircraft navigation.
Therefore, the invention discloses a pulsar autonomous navigation system capable of greatly improving pulsar autonomous navigation efficiency, and aims to solve the problems of the existing pulsar autonomous navigation technology in detection time, detection area and detection dimension.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a cluster distributed pulsar autonomous navigation system and a control method thereof.
The technical scheme of the invention is as follows:
the invention provides a cluster distributed pulsar autonomous navigation system which comprises a plurality of satellites in cluster distributed layout, wherein pulsar detector loads, inter-satellite link loads, star sensor loads and navigation calculation modules are arranged on the satellites.
Further, the pulsar detector load comprises a first rotary table, a photon probe, a first signal amplifying and collecting circuit, a pulsar tracking module and a photon sequence coding module.
Further, the pulsar tracking module comprises:
the pulsar database is used for storing pulsar star map information serving as a navigation source;
and the pulsar rotary table control submodule is connected with the pulsar database and used for calculating the rotation angle of the first rotary table according to the satellite position estimated value and the pulsar position so as to drive the first rotary table to rotate, so that the pulsar to be detected is always in the visual field of the photon probe.
Further, the star sensor load comprises a second rotary table, an optical probe, a second signal amplifying and collecting circuit, a star map matching module and a star map angular distance generating module.
Further, the star map matching module comprises:
the star map database is used for storing star map information of background stars;
and the star sensor rotating table control submodule is connected with the star map database and is used for controlling the second rotating table to rotate so as to enable the main star or the relay star establishing the inter-star link and more than 2 background fixed stars stored in the star map database to be always positioned in the visual field of the optical probe.
Further, the navigation computation module includes:
the cluster satellite pulsar observation task dynamic planning unit is used for dynamically calculating and distributing the observation tasks of each satellite in the cluster to pulsars according to the specific information of inter-satellite links, orbits and attitude estimation of the satellite cluster;
the photon sequence conversion unit is used for converting the photon sequence at the auxiliary star position to the main star position;
and the TOA extraction and navigation resolving unit is used for processing all photon sequences collected by the main satellite, comparing the photon sequences with standard pulsar data information, giving TOA information and performing navigation resolving by using the TOA information.
Furthermore, the photon sequence conversion unit also comprises a relative Doppler shift compensation subunit, wherein the relative Doppler shift compensation subunit is used for calculating the relative velocity between the satellites by using the inter-satellite distance information and the unit position vector information of the observed satellite, and further compensating the relative Doppler shift by using the relative velocity.
A control method of a cluster distributed pulsar autonomous navigation system comprises the following steps:
s1, constructing a cluster distributed satellite system, selecting any satellite with low, medium and high orbits in the earth space, and establishing connection between the satellites through inter-satellite link loads;
s2, initializing a system, sharing the position, speed and attitude estimation information of each satellite through an inter-satellite link, and selecting one satellite as a main satellite and the rest satellites as auxiliary satellites;
s3, selecting navigation pulsar, wherein the main star selects a certain number of pulsars from a pulsar database as navigation observation objects;
s4, observation task allocation, wherein the main satellites dynamically group in the satellite motion process according to the visibility of each satellite to the pulsar, so that each group of satellites optimally observes the target pulsar;
s5, information observation, namely observing a main star or a relay star and more than two background fixed stars by the auxiliary star by using the star sensor load to obtain a starlight angular distance; observing a target pulsar by using a pulsar detector load to obtain the photon sequence information of the pulsar, and sending the obtained information to a main star through an inter-satellite link;
s6, information is collected, and a photon sequence conversion unit of the main satellite aligns the information sent by the auxiliary satellites and the distance measurement information between each auxiliary satellite and the distance measurement information obtained through inter-satellite link carriers in a difference mode to form tabular information;
s7, geometric distance compensation and conversion, namely performing compensation and conversion on the geometric delay of the photon sequence caused by the distance between the satellites;
s8, compensating relative Doppler frequency shift, namely compensating the relative Doppler frequency shift caused by different satellite speeds;
s9, performing navigation positioning calculation on the main satellite, calculating the TOA value of the main satellite according to the photon sequence detected by the main satellite and the photon sequence completed by compensation conversion from the auxiliary satellite, correcting the last position estimation according to the TOA by utilizing a Newton iteration method, and completing navigation positioning calculation on the main satellite when the algorithm is converged;
s10, auxiliary satellite navigation positioning, wherein the main satellite distributes navigation positioning results to each auxiliary satellite through an inter-satellite link, and each auxiliary satellite can further calculate to obtain navigation positioning information of the main satellite by combining high-precision relative navigation positioning information which is given by the inter-satellite link and is relative to the main satellite.
Further, the specific method of the geometric distance compensation conversion is as follows:
s1, converting the projection of the inter-satellite distance to the pulsar direction according to the following formula:
wherein l3The distance between the main satellite and the auxiliary satellite is projected in the direction of the pulsar;
l0giving an inter-satellite distance for an inter-satellite link;
α1and alpha2Observing starlight angular distances formed by 2 fixed stars and a main star or a relay star at the auxiliary star position, which are respectively given by the star sensor;
α3is one of the two stars andthe included angle of the pulsar is a known quantity according to ephemeris;
theta is a high-low angle formed by a connecting line of the main satellite and the auxiliary satellite and the epsilon plane;
is the coordinate system rotation angle;
s2, when l3After the calculation is finished, converting the time of the photons from the auxiliary satellite to the main satellite:
wherein v is0The speed of the primary or relay satellite;
t is the time difference of the photon from the secondary star to the primary star;
and c is the speed of light.
Further, the specific method of the relative doppler shift compensation is as follows: s1, estimating relative speed by utilizing inter-star ranging and star sensor observation:
wherein l0Is the inter-satellite distance;
a unit vector of a satellite obtained by measurement of the star sensor;
is the distance between the starsProjection of (2);
is the satellite relative velocity;
dt is a calculus writing method and represents a tiny variable;
interp represents the difference calculation;
the satellite relative speed at the required moment;
s2, obtaining the relative velocity projection in the pulsar direction by using the following formulaComprises the following steps:
s3, compensating the relative Doppler frequency shift in the pulsar direction:
wherein f isd1Is the satellite doppler shift in the direction of the pulsar;
f is the pulsar natural frequency;
the velocity of the satellite in the direction of the pulsar;
the speed of the primary or relay satellite in the direction of the pulsar;
f'd1for projecting by relative velocityA calculated relative doppler shift; wherein the content of the first and second substances,
fd0doppler shift of dominant star
And c is the speed of light.
The invention achieves the following beneficial effects:
(1) a set of novel pulsar autonomous navigation system is provided, and satellite autonomous navigation can be realized in a cluster distribution mode.
(2) The conversion of photon sequences among satellites is realized through inter-satellite link ranging and star light angular distance observation, so that the synthesis of a pulsar large-area observation array can be equivalently realized. The restriction of a single satellite pulsar navigation mode satellite platform on the area of the detector is broken through.
(3) The system can effectively utilize various types of satellites, and even common satellites can be flexibly accessed to the cluster navigation system by carrying the load on the system, so that autonomous navigation of the cluster pulsar is realized.
Drawings
FIG. 1 is a schematic diagram of the structure of the satellite-borne device of the present invention.
FIG. 2 is a diagram of a clustered distributed satellite system of the present invention, wherein MiRepresents pulsar, AiRepresenting high orbit satellites, BiRepresenting a medium orbit satellite, CiRepresenting low earth orbit satellites, ZiRepresents a satellite group, wherein i is 1,2 … n, and n is a positive number.
FIG. 3 is a schematic view of observing the angular distance between the star lights, wherein S1-SN represent the satellites 1-N in the cluster distribution system, and black double-headed arrows represent the inter-satellite linksThe dotted line represents the observation of the satellite on the main star (or relay star) and the background star by the star sensor, alpha1And alpha2Representing the angular separation of the stars, D the earth, H1 and H2 the stars, Mi the ith pulsar, and the black dotted arrows the photon pulse trains.
Fig. 4 is a flow chart of a control method of the present invention.
Detailed Description
To facilitate an understanding of the present invention by those skilled in the art, specific embodiments thereof are described below with reference to the accompanying drawings.
As shown in fig. 1, the invention provides a cluster distributed pulsar autonomous navigation system, which comprises a plurality of satellites in a cluster distributed layout, wherein the satellites are provided with pulsar detector loads, intersatellite link loads, star sensor loads and navigation calculation modules. The satellite can be a satellite specially used for realizing a navigation function, and can also be a common satellite added with the load in the invention. And information transmission and distance measurement are realized among satellites through an inter-satellite link. The satellite cluster may be a formation, a constellation, or any set of free satellites.
The satellite cluster provides a distributed pulsar observation platform for pulsar autonomous navigation and provides a basis for distributed detection of pulsar photons and synthesis of an equivalent large-area array pulsar detector. The method is characterized in that: and information transmission and distance measurement are carried out between the satellites through the inter-satellite link. Satellites are widely selected and not limited to specific orbits.
The inter-satellite link load is used for realizing data exchange between any two satellites in the cluster distributed pulsar autonomous navigation system. This data exchange may also be accomplished via inter-satellite link relays from other satellites. The inter-satellite link adopts the traditional mature load to realize the communication and the accurate distance measurement between the satellites, and the distance measurement information is sent to the photon sequence conversion unit. The satellite serves as a main satellite and receives photon sequence information, star light angular distance information and the like sent by an auxiliary satellite through an inter-satellite link; as the auxiliary star, the satellite transmits the photon sequence information and the starlight angular distance information to the main star through the inter-star link.
The pulsar probeThe detector load mainly realizes the detection of pulsar to obtain the photon sequence information of pulsar to satellite, the photon sequence is the photon arrival time sequence, the pulsar emits photons which are received by the pulsar detector to record the arrival time of the photons, and the photons arrive one by one, so a time sequence { t & lt/EN & gt is formed1，t2，t3…tn}. The pulsar detector load comprises a first rotary table which can be controlled to rotate, wherein the first rotary table is used for realizing the applicability to satellite platforms with different orbits and attitudes and realizing the maximization of the observation time of a specific pulsar under the constraint conditions of the orbit and the attitudes of the satellite. The first turntable is provided with a photon probe for detecting and collecting pulsar photons and a first signal amplifying and collecting circuit which is connected with the photon probe and is used for converting and amplifying photon signals into electric signals, and a pulsar tracking module and a photon sequence coding module are embedded in the load of the pulsar detector.
Further, the pulsar tracking module comprises:
the pulsar database is used for storing pulsar star map information serving as a navigation source;
and the pulsar rotary table control submodule is connected with the pulsar database and used for calculating the rotation angle of the first rotary table according to the satellite position estimated value and the pulsar position so as to drive the first rotary table to rotate, so that the pulsar to be detected is always in the visual field of the photon probe.
When the photon probe is in work, the photon probe can aim at a target pulsar, and the first rotating platform is continuously adjusted and rotated according to the position of the photon probe, so that the pulsar to be measured is always positioned in the visual field of the photon probe. Photon signals collected by the photon probe are converted and amplified into photon sequence electric signals through the first signal amplification and acquisition circuit, then are encoded (adding information such as time, satellite numbers and the like) through the photon sequence encoding module, and finally are sent to the photon sequence conversion unit of the main satellite (or the relay satellite) through the inter-satellite link load.
The traditional satellite is usually required to observe more than 3 pulsar simultaneously to realize pulsar autonomous navigation. This requires the satellite to carry a detector that enables three dimensional observations. In the invention, the satellite realizes the observation function of 3 pulsar satellites at the same time mainly by grouping the satellite clusters, each group of satellites observes the same pulsar, and the observation of 3 pulsars can be realized by 3 groups of satellites, so that the pulsar detector load carried on each satellite only needs to realize the detection of one pulsar at the same time, thereby greatly saving the load resource of the satellite.
The star sensor load comprises a rotatable second rotary table, an optical probe arranged on the second rotary table and used for observing a main star (or a relay star) and a background star, a second signal amplifying and collecting circuit connected with the optical probe and used for converting and amplifying optical signals into electric signals, and a star map matching module and a star map angular distance generating module embedded on the star sensor load.
Further, the star map matching module comprises:
the star map database is used for storing star map information of background stars;
and the star sensor rotating table control submodule is connected with the star map database and is used for controlling the second rotating table to rotate so as to enable the main star or the relay star establishing the inter-star link and more than 2 background fixed stars stored in the star map database to be always positioned in the visual field of the optical probe.
On the auxiliary star, the star sensor load is used for observing a main star (or a relay star) and 2 or more background fixed stars for establishing an inter-star link, so that the information of the included angle (called as the starlight angular distance) between the main star and the background fixed stars relative to the auxiliary star is obtained, and the obtained starlight angular distance information is sent to a photon sequence conversion unit of the main star (or the relay star) through the inter-star link load.
The navigation computation module includes:
the system comprises a cluster satellite pulsar observation task dynamic planning unit, a satellite acquisition unit and a satellite tracking unit, wherein the cluster satellite pulsar observation task dynamic planning unit is used for dynamically calculating and distributing the pulsar observation tasks of each satellite in a cluster according to specific information such as inter-satellite links, orbits, attitude estimation values and the like of the satellite cluster; the observation tasks comprise the allocation of observation time of each satellite to pulsar, the distribution of specific information required to observe pulsar and the like. Each satellite carries out observation according to the observation task.
For example, when it is necessary to simultaneously observe 3 or more pulsar satellites, the constellation satellites can be divided into 3 or more groups by means of flexible grouping, and each group realizes observation of a specific pulsar. By flexible grouping, it is meant that the satellite constellation is able to perform dynamic satellite observation task allocation and adjustment based on orbit extrapolation or prediction values and based on the particular spatial distribution of the observed pulsar (obtained from the pulsar database).
And the photon sequence conversion unit comprises two subunits, one is a mandatory unit, and the other is an optional unit. The optional unit has the functions of realizing equivalent conversion of the auxiliary star photon sequence, converting the photon arrival time between the auxiliary star and the main star by utilizing high-precision inter-star distance measurement information and star light angular distance information, and equivalently converting the photon sequence at the auxiliary star to the photon sequence at the main star. The selectable unit has the function of a Doppler frequency shift compensation subunit, and the Doppler frequency shift compensation subunit is used for calculating the relative speed between satellites by using the inter-satellite distance information and the unit position vector information (obtained by observing the observed satellite by the star sensor) of the observed satellite, and further compensating the relative Doppler frequency shift by using the relative speed.
The two subunits realize the conversion of the photon sequence at the auxiliary star to the position of the main star. After the conversion, the pulsar detector area equivalent to the primary star is increased and the pulsar is observed independently. When the module 2 is not adopted, the satellite relative Doppler frequency shift can be equivalently eliminated by other methods.
And the TOA extraction and navigation resolving unit is used for processing all photon sequences collected by the main satellite, comparing the photon sequences with standard pulsar data information (such as a standard profile), giving pulsar pulse arrival Time (TOA) information, and performing navigation resolving by using the TOA information.
As shown in fig. 4, a control method of a cluster distributed pulsar autonomous navigation system includes the following steps:
s1, constructing a cluster distributed satellite system, selecting any satellite in low, medium and high orbits in the earth space, and respectively naming the satellite as Ci, Bi and Ai, wherein i is a satellite number, and i is 1,2 … N; the connection between the satellites is established through inter-satellite link loads, as shown in fig. 2;
s2, initializing a system, sharing the position, speed and attitude estimation information of each satellite through an inter-satellite link, and selecting one satellite as a main satellite and the rest satellites as auxiliary satellites;
s3, selecting navigation pulsar, wherein the main star selects a certain number of pulsars from a pulsar database as navigation observation objects;
s4, observation task allocation, wherein the main satellites dynamically group in the satellite motion process according to the visibility of each satellite to the pulsar, so that each group of satellites optimally observes the target pulsar;
s5, information observation, namely observing a main star or a relay star and more than two background fixed stars by the auxiliary star by using the star sensor load to obtain a starlight angular distance; observing a target pulsar by using a pulsar detector load to obtain the photon sequence information of the pulsar, and sending the obtained information to a main star through an inter-satellite link;
s6, information is collected, and a photon sequence conversion unit of the main satellite carries out time alignment on information sent by the auxiliary satellites and ranging information between each auxiliary satellite and the information obtained through inter-satellite link carriers in a difference mode to form the following tabulated information;
s7, geometric distance compensation and conversion, namely performing compensation and conversion on the geometric delay of the photon sequence caused by the distance between the satellites;
s8, compensating relative Doppler frequency shift, namely compensating the relative Doppler frequency shift caused by different satellite speeds;
s9, the main satellite carries out navigation positioning calculation, the main satellite combines the photon sequence detected by the main satellite and the photon sequence converted by the auxiliary satellite, carries out contour folding to the center of mass of the solar system according to the position estimation value and compares the contour with the standard contour at the center of mass of the solar system, the product of the difference of the contour phases and the period is the TOA value reflecting the position estimation error, the last position estimation is corrected according to the TOA by utilizing a Newton iteration method, and when the algorithm is converged, the navigation positioning calculation of the main satellite is finished;
s10, auxiliary satellite navigation positioning, wherein the main satellite distributes navigation positioning results to each auxiliary satellite through an inter-satellite link, and each auxiliary satellite can further calculate to obtain navigation positioning information of the main satellite by combining high-precision relative navigation positioning information which is given by the inter-satellite link and is relative to the main satellite.
Further, the specific method of the geometric distance compensation conversion is as follows:
s1, converting the projection of the inter-satellite distance to the pulsar direction according to the following formula:
wherein l3The distance between the main satellite and the auxiliary satellite is projected in the direction of the pulsar;
l0giving an inter-satellite distance for an inter-satellite link;
α1and alpha2Observing starlight angular distances formed by 2 fixed stars and a main star or a relay star at the auxiliary star position, which are respectively given by the star sensor;
α3the included angle between a certain fixed star of the two fixed stars and the pulsar is a known quantity according to the ephemeris;
theta is a high-low angle formed by a connecting line of the main satellite and the auxiliary satellite and the epsilon plane; the epsilon plane is a plane which passes through the main star or the auxiliary star and is parallel to the direction vectors of the fixed star 1 and the fixed star 2;
is the coordinate system rotation angle;
s2, when l3After the calculation is finished, converting the time of the photons from the auxiliary satellite to the main satellite:
wherein v is0The speed of the primary or relay satellite;
t is the time difference of the photon from the secondary star to the primary star;
and c is the speed of light.
Further, the specific method of the relative doppler shift compensation is as follows:
s1, estimating relative speed by utilizing inter-star ranging and star sensor observation:
wherein l0Is the inter-satellite distance;
a unit vector of a satellite obtained by measurement of the star sensor;
is the distance between the starsProjection of (2);
is the satellite relative velocity;
dt is a calculus writing method and represents a tiny variable;
interp represents the difference calculation;
the satellite relative speed at the required moment;
s2, obtaining the relative velocity projection in the pulsar direction by using the following formulaComprises the following steps:
s3, compensating the relative Doppler frequency shift in the pulsar direction:
wherein f isd1Is the satellite doppler shift in the direction of the pulsar;
f is the pulsar natural frequency;
the velocity of the satellite in the direction of the pulsar;
the speed of the primary or relay satellite in the direction of the pulsar;
f'd1for projecting by relative velocityA calculated relative doppler shift; wherein the content of the first and second substances,
fd0doppler shift of dominant star
And c is the speed of light.
After the geometric distance compensation and the relative Doppler frequency shift compensation, the navigation task is converted into a photon arrival time sequence collected by a trunking satellite system, and the initial phase and the Doppler frequency shift of the main satellite are estimated, so that the position and the speed of the main satellite are solved. And further, calculating the positions and the speeds of all other satellites in the cluster satellite system according to the relative positions and the speeds between the main satellite and the auxiliary satellite, and completing the navigation task.
As shown in fig. 3, for example:
the pulsar detector load and the star sensor load stated in the invention are carried on the satellite, and the satellite S2 observes and obtains the star angular distance, the inter-star distance and the photon sequence information of the pulsar. With this information, the photon sequence information at S2 can be equivalently translated to the main star S1. The photon sequence of the SN can be equivalently converted to S2 and then to S1, and at this time, S2 is the relay star of S1. And S1, navigation calculation can be carried out after the equivalent photon sequence of the auxiliary star to the pulsar is obtained, and the autonomous positioning of S1 is realized. And then, combining information such as inter-satellite links and the like to realize navigation and positioning of other satellites.
The above-described embodiments of the present invention do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.