CN115166781A - Method for monitoring network integrity of world-earth cooperation PNT (public network technology) - Google Patents

Method for monitoring network integrity of world-earth cooperation PNT (public network technology) Download PDF

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CN115166781A
CN115166781A CN202210920937.5A CN202210920937A CN115166781A CN 115166781 A CN115166781 A CN 115166781A CN 202210920937 A CN202210920937 A CN 202210920937A CN 115166781 A CN115166781 A CN 115166781A
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integrity
monitoring
pnt
navigation
error
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易卿武
廖桂生
蔚保国
陶海红
王彬彬
盛传贞
应俊俊
赵精博
惠沈盈
杨建雷
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Xidian University
CETC 54 Research Institute
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    • G—PHYSICS
    • 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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/20—Integrity monitoring, fault detection or fault isolation of space segment
    • G—PHYSICS
    • 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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/45—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement
    • G01S19/46—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement the supplementary measurement being of a radio-wave signal type

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Abstract

The invention discloses a method for monitoring the integrity of a world-earth collaborative PNT network. The method is based on a space-ground cooperative positioning, navigation and time service network composed of a foundation navigation system, and a comprehensive PNT integrity monitoring system is established by analyzing various navigation system error sources and integrity risk models; the system section monitors the integrity of signals and information of a space-based navigation source and a foundation navigation source, and solves the problem of rapid monitoring of the integrity of a global domain of a Beidou navigation system; the service section designs a service section high-precision product integrity unified mathematical expression method; and a user segment is fused with a multi-source heterogeneous sensor, so that an indoor and outdoor seamless high-precision positioning autonomous integrity algorithm is realized. The invention breaks through the integrity restriction bottleneck of the world-wide collaborative PNT network applied to the fields of unmanned driving, artificial intelligence and the like, and fills the technical blank in the aspect of the integrity monitoring algorithm of the comprehensive PNT network at home and abroad at present.

Description

Method for monitoring network integrity of world-earth cooperation PNT (public network technology)
Technical Field
The invention relates to a high-precision integrity monitoring method suitable for a space-ground cooperative PNT network, and belongs to the field of satellite navigation, indoor and outdoor integrated positioning and integrity monitoring.
Background
The high-precision position information plays an important role in promoting the development of national economy and has wide market application requirements in the fields of unmanned driving and artificial intelligence. Currently, outdoor positioning mainly depends on a satellite navigation system mainly based on BDS and GPS, and indoor positioning is realized through navigation systems such as pseudolites and ultra wideband. Aiming at the problems that various positioning source systems are not unified and the positioning means are not fused, a more ubiquitous, fused and intelligent comprehensive navigation system needs to be established urgently. The space-ground cooperative PNT network is based on space-based navigation systems such as GNSS/LEO and the like, and ground-based navigation systems such as pseudolite/ultra wide band/5G and the like, and solves the key problems of unified space-time reference, signal system coordination and positioning method fusion, so that a space-ground cooperative positioning, navigation and timing network is constructed.
The integrity refers to the capability of timely giving an alarm to a user when a navigation system breaks down or an error exceeds a limit, is one of important evaluation indexes of the navigation system, and has important value in the application fields relating to life and property safety of the user, such as civil aviation, precision approach, intelligent transportation, emergency response and the like. The existing SBAS and GBAS integrity models monitor the integrity of a single GNSS satellite-based augmentation positioning system and a single ground-based augmentation system, and cannot meet the requirement of the integrity of a space-ground cooperative PNT network integrating new elements such as low-orbit, pseudo-satellite and multisource sensors. At present, research institutions at home and abroad are dedicated to the research of a comprehensive PNT network composition and positioning system, and a mature integrity monitoring scheme and a mature integrity monitoring model are not formed yet.
Disclosure of Invention
The invention provides a method for monitoring the high-precision integrity of a world-collaborative PNT network, aiming at the problems that the indoor and outdoor joint positioning is not uniform and the positioning service risk is uncontrollable caused by the inconsistent outdoor positioning and indoor positioning means and the immature comprehensive PNT network integrity monitoring method. The method mainly divides the world collaborative PNT network into a system section, a service section and a user section, and respectively carries out integrity monitoring key technology research, thereby establishing an indoor and outdoor unified high-precision and high-reliability integrity positioning service.
The invention is realized by the following technical scheme:
a method for monitoring high-precision integrity of a world-earth collaborative PNT network comprises the following steps:
(1) The method comprises the steps of constructing a world-earth cooperative PNT network on the basis of GNSS and pseudolites, establishing a three-level integrity monitoring model by analyzing various navigation system positioning principles and error sources, and sequentially dividing the three-level integrity monitoring model into system section integrity monitoring, service section integrity monitoring and user section integrity monitoring;
(2) And a permanent observation station is arranged on the ground in the system section, and navigation source information and signal integrity are monitored. The satellite-borne monitoring receiver is mounted on the low-earth orbit satellite, so that the global domain integrity of the Beidou navigation system can be rapidly monitored, and meanwhile, the low-earth orbit satellite-based integrity monitoring has the advantage of being not influenced by a ground interference source;
(3) The service section high-precision product comprises a GNSS precision satellite orbit, a precision satellite clock error and a pseudo satellite precision clock error, a reference station residual error is solved through an error modeling and parameter estimation method, and a service section high-precision product integrity unified representation model is established;
(4) The integrity monitoring of the user section is realized by fusing multi-source sensors and estimating the position of the sensor in real time by an anti-error Kalman filtering method, so that the problem of fault identification and processing under the condition of degradation/failure of a navigation signal is solved, the positioning protection level of a user is calculated, and the high-precision positioning integrity monitoring of indoor and outdoor integration is realized;
(5) On the basis of the world collaborative PNT network, the integrity monitoring method of the system section, the service section and the user section is integrated, and integrity service which alarms the user within the set time when the user positioning protection level exceeds the limit within the determined risk level is established.
Further, the specific mode of the step (1) is as follows:
(101) The space-ground cooperative PNT network comprises a space-based navigation source and a foundation navigation source, wherein the space-based navigation source mainly refers to a Global Navigation Satellite System (GNSS), and the foundation navigation source mainly refers to a pseudo satellite positioning system. By unifying time reference and space reference among different positioning means, fusing a plurality of indoor and outdoor positioning methods, and establishing a world-wide cooperative PNT service network;
(102) The error items influencing the integrity of the space-ground cooperative PNT network comprise a ground signal power deviation, an S curve zero crossing point deviation, a space signal ranging error, a precise satellite orbit error, a precise satellite clock error, a phase deviation, a multipath effect, a receiver observation error and the like. Classifying the fault sources, and dividing an integrity monitoring system into system section integrity monitoring, service section integrity monitoring and user section integrity monitoring;
further, the specific mode of the step (2) is as follows:
(201) In order to monitor the integrity of signals and information of a space-ground cooperative PNT network system section, a GNSS monitoring station is arranged outdoors, and a pseudolite monitoring station is arranged indoors and used for monitoring error sources such as power deviation of a landing signal, S curve zero crossing point deviation, space signal ranging precision and the like. Respectively carrying out integrity monitoring and integrity state identification on each navigation satellite and each pseudolite, and identifying the integrity state of the system when the number of the faults of the navigation satellites or the pseudolites reaches a certain proportion;
(202) The Beidou ground monitoring station cannot be distributed in the global and can not directly monitor the overseas navigation satellite, so that the integrity monitoring period of the Beidou system is too long. A low-orbit navigation enhanced constellation is designed, a monitoring receiver is carried on a low-orbit satellite, and the integrity of the full constellation of the Beidou navigation system is monitored in real time. Compared with a ground monitoring means, the low-orbit satellite-based monitoring has the advantage of being not influenced by ground interference signals and error sources. Meanwhile, the Beidou/GNSS with low-orbit navigation enhancement can improve the integrity performance of the whole space-based navigation system;
further, the specific mode of the step (3) is as follows:
(301) The reference station continuously tracks GNSS satellites and pseudo satellites, errors such as antenna phase deviation, relativistic effect and tidal effect are corrected through an error modeling method, and receiver clock error and troposphere delay are determined based on a parameter estimation method. Representing the comprehensive error of the GNSS/LEO precision satellite orbit, the precision satellite clock error and the pseudolite precision clock error by using the observation value residual error;
(302) And carrying out mathematical statistical analysis on the residual error of the reference station by adopting an envelope method, and determining mathematical expectation, variance and probability distribution density. And under a certain confidence probability level, when the residual error of the reference station exceeds the limit, the high-precision product in the service section is indicated to be abnormal, otherwise, the high-precision product in the service section is indicated to be normal. Evaluating a high-precision product through a reference station residual error, thereby establishing a service section integrity unified representation mode;
further, the specific mode of the step (4) is as follows:
(401) And constructing an elastic PNT user positioning terminal by fusing multi-source heterogeneous sensors. Estimating position information of the flexible PNT user terminal by combining the pseudo range, the carrier phase observation value and the acceleration and angular velocity observation value by using an anti-difference Kalman filtering method, and identifying and processing a fault observation value to realize a user side autonomous integrity positioning algorithm;
(402) After the flexible PNT user terminal identifies and eliminates the fault observation value, the positioning protection level of the user is calculated based on the observation condition and the integrity parameter broadcasted by the service section, wherein the positioning protection level comprises a vertical protection level and a horizontal protection level, and when the positioning protection level exceeds an alarm threshold, a warning is sent.
The invention has the beneficial effects that:
1. aiming at the problem that the current integrity monitoring method cannot meet the fusion of various positioning means and the unification of indoor and outdoor positioning, the invention designs a method for monitoring the integrity of a world-earth collaborative PNT network, unifies the time reference and the space reference of various positioning means of GNSS/LEO/PL/INS, and constructs the world-earth collaborative PNT network.
2. According to the method, a three-level integrity monitoring model of a system section, a service section and a user section is established according to the characteristics of a world collaborative PNT network fault tree. By arranging the GNSS/LEO/PL receiver on the ground and designing a low-orbit navigation enhanced constellation, the rapid integrity monitoring of the Beidou/GNSS signals and information is realized.
3. The invention determines the residual error of the observation station by using error modeling and parameter estimation methods, and establishes a uniform integrity representation model of the high-precision product in the service section.
4. The method disclosed by the invention integrates the multi-source heterogeneous sensors, estimates the position of the user terminal in real time by an anti-difference Kalman filtering method, identifies an abnormal observation value, and calculates the positioning protection level by combining the integrity parameters of the service section and the observation conditions.
5. The invention relates to a comprehensive system segment, a service segment and a user segment integrity monitoring method, which establishes an integrity service for warning a user within a specified time when the user positioning protection level exceeds the limit in determining a risk level, thereby breaking through the integrity restriction bottleneck of applying a world-wide collaborative PNT network to the fields of unmanned driving, artificial intelligence and the like and filling the technical blank in the aspect of the integrity monitoring algorithm of the comprehensive PNT network at home and abroad at present.
Drawings
Fig. 1 is a flowchart of a method for monitoring integrity of a world-wide collaborative PNT network according to an embodiment of the present invention.
Detailed Description
To better illustrate the objects and advantages of the present invention, the following description is provided for the purpose of illustrating the invention with reference to the accompanying drawings and detailed description.
A high-precision integrity monitoring method for a world-earth collaborative PNT network is characterized in that a comprehensive PNT integrity monitoring system is established by analyzing various navigation system error sources and integrity risk models based on a world-earth collaborative positioning, navigation and time service network composed of a GNSS/LEO and other ground-based navigation systems and a pseudolite/ultra-wideband/5G and other ground-based navigation systems, and is sequentially divided into system section integrity monitoring, service section integrity monitoring and user section integrity monitoring. The system section is based on a GNSS/LEO/pseudolite/ultra wide band/5G reference station, monitors integrity of signals and information of a space-based navigation source and a foundation navigation source, and solves the problem of rapid monitoring of the integrity of the global domain of the Beidou navigation system by utilizing the short-period characteristic of a low-orbit constellation orbit. The service segment acquires the residual error of the reference station by error modeling and parameter estimation, and a service segment high-precision product integrity unified mathematical expression method is designed. And a user segment is fused with a multi-source heterogeneous sensor, so that an indoor and outdoor seamless high-precision positioning autonomous integrity algorithm is realized.
As shown in fig. 1, the method comprises the following specific steps:
(1) Constructing a heaven-earth collaborative PNT network based on a heaven-earth navigation source and a ground navigation source, establishing a three-level integrity monitoring system, and sequentially carrying out system section integrity monitoring, service section integrity monitoring and user section integrity monitoring;
(101) The space-based navigation source comprises a Global Navigation Satellite System (GNSS) mainly comprising Beidou/GPS/GLONASS/GALILEO and a low-orbit satellite navigation enhancement system (LEO), and the ground-based navigation source comprises a pseudo satellite positioning system (PL), an ultra-wideband positioning system and a 5G base station. By unifying the time reference T between different positioning means sys And a spatial reference X sys Fusing multiple indoor and outdoor positioning methods F (T) sys ,X sys ) Establishing a world-to-earth collaborative PNT service network;
(102) The error source of the space-ground cooperative PNT network mainly comprises a power deviation S of a ground signal bias S curve zero crossing point deviation SCB, space signal ranging error SISRE and precision satellite orbit error delta X GNSS 、ΔX LEO 、ΔX PL Clock error delta T of precise satellite GNSS 、ΔT LEO 、ΔT PL Phase deviation FCB, multipath effect MP, receiver observation error e, etc. Classifying the error sources, and dividing an integrity monitoring model into system section integrity monitoring, service section integrity monitoring and user section integrity monitoring;
(2) The integrity monitoring of the system section is to arrange a GNSS/LEO/PL permanent observation station in a ground open environment or indoors and monitor the information and signal integrity of a space-based navigation source and a ground-based navigation source. A satellite-borne monitoring receiver is installed on a low-orbit satellite, and the problem of rapid integrity monitoring of a Beidou navigation system due to global station distribution difficulty is solved by using the short-period characteristic of a low-orbit constellation orbit. When the navigation signal or the information is monitored to be abnormal, a warning is sent to the integrity monitoring model, otherwise, the next monitoring stage is started;
(201) By arranging the GNSS/LEO monitoring station outdoors and the PL monitoring station indoors, the power deviation S of the landing signal is monitored bias And error sources such as S curve zero crossing point deviation SCB, space signal ranging error SISRE and the like. Integrity monitoring and integrity state identification are respectively carried out on each GNSS/LEO navigation satellite and each PL satellite
Figure BDA0003777544520000071
When the number of the faults of the navigation satellite or the pseudo satellite reaches a certain proportion, the state of the integrity of the system is adjusted
Figure BDA0003777544520000072
And (3) carrying out identification:
Figure BDA0003777544520000081
in the formula (I), the compound is shown in the specification,
Figure BDA0003777544520000082
the signal and information integrity flag of the ith satellite in the navigation system is set as 1 when the monitored satellite signal and information are normal and 0 when the monitored satellite signal and information are abnormal.
Figure BDA0003777544520000083
In the formula, H system For navigation system integrity identification, the navigation system is normal when the number of normal operating satellites exceeds 80%, and is represented by 1, and the navigation system is abnormal when the number of normal operating satellites is less than 80%, and is represented by 0.
(202) A low-orbit navigation enhanced constellation is designed, the constellation is composed of 4 orbit surfaces with 45-degree difference of orbit inclination angles, each orbit surface is provided with 3 satellites with 120-degree difference of true approach point angles, and the orbit height is 1000 kilometers. A monitoring receiver is installed in the Z-axis negative direction of the LEO satellite, and the complete constellation integrity of the Beidou navigation system is monitored in real time by utilizing the characteristic that the orbit period of a low-earth orbit is short:
Figure BDA0003777544520000084
where T is the orbital period, GM is the Earth's gravitational constant, and a is the orbital height. For the Beidou MEO satellite, the orbit period is about 12.9 hours, and for the LEO satellite with the orbit height of 1000 kilometers, the orbit period is about 1.7 hours. Through simulation analysis, the low-orbit constellation designed by the invention can monitor the integrity of the full constellation of the Beidou navigation system in real time. Meanwhile, the low-orbit satellite-based integrity monitoring has the advantage of being not influenced by the ground interference signal IFS and the multipath error source MP. The low-orbit navigation enhanced Beidou/GNSS can improve the integrity performance of the whole space-based navigation system, including the minimum detectable deviation and the fault detection rate;
(3) The service segment high-precision product comprises a GNSS precision satellite orbit X GNSS Clock error delta T of precise satellite GNSS Precise clock error delta T of pseudo satellite PL And solving the residual error of the GNSS/LEO/PL reference station by an error modeling and parameter estimation method, thereby establishing a service section high-precision product integrity unified representation model. When monitoring that the high-precision products in the service section are abnormal, sending a warning to the integrity monitoring model, otherwise, entering the next monitoring stage;
(301) The reference station continuously tracks GNSS satellites and pseudo satellites PL, and the phase center deviation delta of the antenna is corrected by an error modeling method pco Relativistic effect delta rel Tidal effect delta tide Equal error, receiver clock error Δ T determined based on a method of parameter estimation r Troposphere delay Trop. Representing GNSS/LEO precision satellite orbit X using observation residuals GNSS/LEO Clock error delta T of precise satellite GNSS/LEO And pseudo satellite precision clock error delta T PL The comprehensive error of (2): v. of GNSS/LEO ＝P-ρ+c·ΔT GNSS/LEO -c·ΔT r +Trop+δ pco +δ rel +δ tide
v PL ＝P-ρ+c·ΔT PL -c·ΔT r
In the formula, v GNSS/LEO Is the combined error, v, of GNSS or LEO satellites PL And the comprehensive error of the pseudo satellite PL is shown, P is the observation value of the GNSS/LEO/PL pseudo range, rho is the geometric distance from the receiver to the GNSS/LEO/PL satellite, and c is the speed of light.
(302) And carrying out mathematical statistical analysis on the residual error of the reference station by adopting an envelope method, and determining mathematical expectation, variance and probability distribution density. And under a certain confidence probability level, when the residual error of the reference station exceeds the limit, the high-precision product in the service section is indicated to be abnormal, otherwise, the high-precision product in the service section is indicated to be normal. Evaluating a high-precision product through a reference station residual error, thereby establishing a service section integrity unified representation mode;
(302) Carrying out mathematical statistics analysis on the reference station residual error v by adopting an envelope method, and determining a mathematical expectation E (v), a standard sigma (v) and a probability distribution density f (v):
Figure BDA0003777544520000101
and under a certain confidence probability level, when the residual error of the reference station exceeds the limit, the high-precision product in the service section is indicated to be abnormal, otherwise, the high-precision product in the service section is indicated to be normal. Evaluating a high-precision product through a reference station residual error, thereby establishing a service segment integrity unified representation mode:
Figure BDA0003777544520000102
in the formula, H product Is a service segment high-precision product integrity mark, and when t is the time, the residual standard deviation statistic sigma [ v (t)]Not exceeding the time limit H product ＝σ[v(t)]When the residual standard deviation statistic at the time t exceeds the limit H product And =0, indicating an abnormality in integrity.
(4) The integrity monitoring of the user section is realized by fusing multi-source sensors and estimating the position X of the sensor in real time by an anti-error Kalman filtering method, thereby solving the problem of fault identification and processing under the conditions of degradation and failure of GNSS/PL signals and calculating the positioning protection level sigma of the user PL The indoor and outdoor integrated high-precision positioning integrity monitoring IO-RAIM is realized;
(401) In order to solve the problem that the integrity positioning in indoor and outdoor environments and urban complex environments is difficult to realize by a single positioning means, an elastic PNT user positioning terminal is constructed by fusing multi-source sensors such as GNSS/LEO/PL/INS and the like. And (2) estimating the position X of the flexible PNT user terminal by an anti-difference Kalman filtering method by combining an observation vector Obs consisting of a pseudo-range observation value P, a carrier phase observation value L, an acceleration a of the INS and an angular acceleration observation value w of the GNSS/LEO/PL, identifying and processing a fault observation value delta, and realizing a user terminal autonomous integrity positioning algorithm:
Obs＝AX-V
Figure BDA0003777544520000111
in the above equation, matrix a is a parameter estimation coefficient matrix formed from the observation values, and V is a residual vector. When the ith residual vector exceeds the limit value of 2 XH product And if not, the observation value is regarded as a normal observation value.
(402) After the flexible PNT user terminal identifies and eliminates the fault observation value delta, the high-precision product integrity parameter H is broadcasted based on the observation condition and the service section product For calculationHome location protection level sigma PL Including the horizontal guard level σ HPL And a vertical protection level sigma VPL ：
σ PL ＝3×H porduct ×PDOP
σ HPL ＝3×H porduct ×HPDOP
σ VPL ＝3×H porduct ×VPDOP
In the formula, PDOP is a positioning accuracy factor generated according to an observation condition, HDOP is a positioning accuracy factor in the horizontal direction, and VDOP is a positioning accuracy factor in the vertical direction. When the positioning protection level exceeds an alarm threshold, a warning is issued to the user, thereby avoiding the integrity risk due to a missed alarm.
According to the method, through analyzing the positioning principles and fault trees of a plurality of navigation systems such as GNSS, LEO, pseudolite and inertial navigation, the time reference and the space reference of the plurality of positioning systems are unified, and a three-level integrity model of system section signal and information monitoring, service section high-precision product monitoring and user section autonomous positioning integrity monitoring is respectively established, so that the problem of unified representation of integrity models of different positioning systems is solved, and high-precision and high-reliability positioning service guarantee is provided for a world-earth cooperative PNT network.
In a word, the invention solves the problems that the integrity monitoring method of various positioning means in the comprehensive PNT network is not coordinated, the integrity monitoring period of the Beidou navigation system global domain is long, the integrity of high-precision products in a service section is difficult to uniformly express, the indoor and outdoor integrated integrity monitoring technology of a user section is immature and the like. The invention is suitable for application scenes relating to life and property safety of users, such as civil aviation, precision approach, unmanned driving, intelligent transportation, disaster rescue and the like, and has important value in national economic construction and safety guarantee.
The specific embodiments of the present invention have been described above in detail. It should be understood that numerous changes and modifications could be devised by those skilled in the art without departing from the invention. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims (5)

1. A method for monitoring the integrity of a world-wide collaborative PNT network is characterized by comprising the following steps:
(1) The method comprises the steps of constructing a world-earth cooperative PNT network on the basis of GNSS and pseudolites, establishing a three-level integrity monitoring model by analyzing various navigation system positioning principles and error sources, and sequentially dividing the three-level integrity monitoring model into system section integrity monitoring, service section integrity monitoring and user section integrity monitoring;
(2) The system section integrity monitoring is characterized in that a permanent observation station is arranged on the ground to monitor navigation source information and signal integrity, and a satellite-borne monitoring receiver is mounted on a low-orbit satellite to realize rapid monitoring of the integrity of the global domain of the Beidou navigation system;
(3) Establishing a high-precision product in a service section, wherein the high-precision product comprises a GNSS precision satellite orbit, a precision satellite clock error and a pseudolite precision clock error, solving a reference station residual error through an error modeling and parameter estimation method, and establishing a service section high-precision product integrity unified representation model;
(4) The integrity monitoring of the user section is realized by fusing multi-source sensors and estimating the position of the sensor in real time by an anti-error Kalman filtering method, so that the problems of fault identification and processing under the condition of degradation/failure of a navigation signal are solved, the positioning protection level of a user is calculated, and the high-precision positioning integrity monitoring of indoor and outdoor integration is realized;
(5) On the basis of the world collaborative PNT network, the integrity monitoring method of the system section, the service section and the user section is integrated, and integrity service which alarms the user within the set time when the user positioning protection level exceeds the limit within the determined risk level is established.
2. The method for monitoring network integrity of a space-ground cooperative PNT according to claim 1, wherein the specific manner of step (1) is as follows:
(101) The space-ground cooperative PNT network comprises a space-based navigation source and a foundation navigation source, wherein the space-based navigation source is a Global Navigation Satellite System (GNSS), and the foundation navigation source is a pseudo satellite positioning system; by unifying time reference and space reference among different positioning means, fusing a plurality of indoor and outdoor positioning methods, and establishing a world-to-earth cooperative PNT service network;
(102) The error items influencing the integrity of the space-ground cooperative PNT network comprise power deviation of a ground signal, zero-crossing deviation of an S curve, space signal ranging error, precision satellite orbit error, precision satellite clock error, phase deviation, multipath effect and receiver observation error, the error items are classified, and an integrity monitoring system is divided into integrity monitoring of a system section, integrity monitoring of a service section and integrity monitoring of a user section.
3. The method for monitoring network integrity of a space-ground cooperative PNT according to claim 1, wherein the specific manner of step (2) is as follows:
(201) In order to monitor the integrity of signals and information of a space-ground cooperative PNT network system section, a GNSS monitoring station is arranged outdoors, and a pseudolite monitoring station is arranged indoors and used for monitoring power deviation of a landing signal, S curve zero crossing point deviation and space signal ranging precision; respectively carrying out integrity monitoring and integrity state identification on each navigation satellite and each pseudolite, and identifying the integrity state of the system when the number of faults of the navigation satellites or the pseudolites reaches a preset proportion;
(202) The Beidou ground monitoring station cannot be distributed in the global and can not directly monitor the overseas navigation satellites, so that the integrity monitoring period of the Beidou system is too long, the low-orbit navigation is adopted to enhance the constellation, and a monitoring receiver is carried on the low-orbit satellite to monitor the integrity of the full constellation of the Beidou navigation system in real time.
4. The method for monitoring network integrity of a space-ground cooperative PNT according to claim 1, wherein the specific manner of step (3) is as follows:
(301) The method comprises the following steps that a reference station continuously tracks GNSS satellites and pseudo satellites, errors of antenna phase deviation, relativistic effect and tidal effect are corrected through an error modeling method, receiver clock error and troposphere delay are determined based on a parameter estimation method, and the comprehensive errors of GNSS/LEO precision satellite orbits, precision satellite clock error and pseudo satellite precision clock error are represented by using observed value residual errors;
(302) Carrying out mathematical statistical analysis on the residual error of the reference station by adopting an envelope method, and determining mathematical expectation, variance and probability distribution density; when the residual error of the reference station exceeds the limit, the high-precision product of the service section is represented to be abnormal, otherwise, the high-precision product of the service section is represented to be normal; and evaluating a high-precision product of the service section through the residual error of the reference station, thereby establishing a unified representation mode of the integrity of the service section.
5. The method for monitoring network integrity of a space-ground cooperative PNT according to claim 1, wherein the specific manner of step (4) is as follows:
(401) Constructing an elastic PNT user positioning terminal by fusing multi-source heterogeneous sensors; estimating position information of the flexible PNT user terminal by combining the pseudo range, the carrier phase observation value and the acceleration and angular velocity observation value by using an anti-difference Kalman filtering method, and identifying and processing a fault observation value to realize a user side autonomous integrity positioning algorithm;
(402) After the flexible PNT user terminal identifies and eliminates the fault observation value, the positioning protection level of the user is calculated based on the observation condition and the integrity parameter broadcasted by the service section, wherein the positioning protection level comprises a vertical protection level and a horizontal protection level, and when the positioning protection level exceeds an alarm threshold, a warning is sent.
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