阅读说明：本技术 一种地基增强系统完好性故障识别方法及系统 (Method and system for identifying integrity fault of foundation enhancement system ) 是由 薛瑞 王康 于 2020-12-01 设计创作，主要内容包括：本发明涉及一种地基增强系统完好性故障识别方法及系统,属于卫星导航技术领域,解决了现有技术中故障识别方法精度较低,不能更好的识别潜在的的完好性故障的问题。该方法包括获取地面参考接收机以及机载接收机提供的历史实测数据；基于所述历史实测数据,计算机载接收机的差分定位误差以及保护级；基于所述差分定位误差以及所述保护级,从所述历史实测数据中提取故障数据集；对所述故障数据集进行故障特征提取并确定故障类型。提高了故障检测识别的精度,实现了对更高级的完好性故障识别的需求。(The invention relates to a method and a system for identifying integrity faults of a ground-based augmentation system, belongs to the technical field of satellite navigation, and solves the problems that in the prior art, the fault identification method is low in precision and cannot better identify potential integrity faults. The method comprises the steps of obtaining historical measured data provided by a ground reference receiver and an airborne receiver; based on the historical measured data, calculating a differential positioning error and a protection level of the airborne receiver; extracting a fault data set from the historical measured data based on the differential positioning error and the protection level; and extracting fault characteristics of the fault data set and determining the fault type. The accuracy of fault detection and identification is improved, and the requirement for higher-level integrity fault identification is met.)

1. A method for identifying integrity faults of a ground based augmentation system is characterized by comprising the following steps:

acquiring historical measured data provided by a ground reference receiver and an airborne receiver;

based on the historical measured data, calculating a differential positioning error and a protection level of the airborne receiver;

extracting a fault data set from the historical measured data based on the differential positioning error and the protection level;

and extracting fault characteristics of the fault data set and determining the fault type.

2. The fault identification method according to claim 1, wherein the historical measured data comprises first textual data, first observed data, and second textual data and second observed data provided by the ground reference receiver; the calculating the differential positioning error of the airborne receiver based on the historical measured data comprises:

calculating a pseudo-range correction value of the nth satellite and an error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite based on the first text data and the first observation data; wherein, the nth satellite is any one of all satellites;

calculating a pseudo-range measurement value of the airborne receiver and the nth satellite and an error standard deviation of the pseudo-range measurement value of the airborne receiver and the nth satellite based on the second text data and the second observation data; combining the pseudo-range correction value of the nth satellite and the error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite to calculate the position of the airborne receiver;

obtaining a differential positioning error of the airborne receiver based on the calculated position of the airborne receiver and the real position of the airborne receiver; the differential positioning error includes a vertical component and a horizontal component.

3. The method of claim 2, wherein calculating pseudorange corrections for an nth satellite based on the first textual data and the first observation data comprises:

acquiring the orbit position of the nth satellite based on the first text data, and acquiring the real distance between the mth ground reference receiver and the nth satellite by combining the real position of the mth ground reference receiver;

obtaining a pseudo-range observation value between the mth ground reference receiver and the nth satellite based on the first observation data, and calculating to obtain a pseudo-range correction value of the mth ground reference receiver and the nth satellite by combining a real distance between the mth ground reference receiver and the nth satellite;

and averaging the pseudo-range correction values of the M ground reference receivers and the nth satellite to obtain the pseudo-range correction value of the nth satellite, wherein M is the number of the ground reference receivers.

4. The method of claim 3, wherein based on the historical measured data, the level of protection of the computer-based receiver comprises:

calculating to obtain a fault-free hypothesis protection level by combining a projection matrix from a pseudo-range domain to a positioning domain and a fault-free missing detection coefficient based on the pseudo-range correction value error standard deviation between the ground augmentation system and the nth satellite and the pseudo-range measurement value error standard deviation between the airborne receiver and the nth satellite;

calculating to obtain a single receiver fault hypothesis protection level based on a pseudo-range correction value of an nth satellite, a pseudo-range correction value of an mth ground reference receiver and the nth satellite, a pseudo-range correction value error standard deviation of a ground augmentation system and the nth satellite, and a pseudo-range measurement value error standard deviation of an airborne receiver and the nth satellite, in combination with a projection matrix from a pseudo-range domain to a positioning domain and a missing detection coefficient;

and comparing the non-fault assumed protection level with the single-receiver fault assumed protection level to obtain the protection level of the airborne receiver.

5. The method of claim 4, wherein the protection levels comprise a vertical protection level and a horizontal protection level, and wherein extracting the fault data set from the historical measured data based on the differential positioning error and the protection levels comprises:

and when the vertical component is greater than the vertical protection level and/or the horizontal component is greater than the horizontal protection level, the corresponding historical measured data is a fault data set.

6. The fault identification method of claim 5, wherein said performing fault feature extraction on the fault data set and determining a fault type comprises:

analyzing the fault data set by adopting a statistical method based on the fault data set to determine fault characteristics;

and identifying the fault type according to the fault characteristics.

7. The method of claim 6, wherein when the fault signature is a pseudorange correction vector for the mth terrestrial reference receiver and N satellites;

and based on the pseudo-range correction value vectors of M ground reference receivers, wherein the pseudo-range correction value vectors of the M ground reference receivers are initial clusters, and when the initial clusters are divided into two clusters with the number of 1 and M-1 respectively by combining a Diana fault identification algorithm, the fault type is a single receiver fault.

8. A system for identifying integrity faults in a ground based augmentation system, comprising:

the data acquisition module is used for acquiring historical measured data provided by the ground reference receiver and the airborne receiver;

the differential positioning error calculation module is used for calculating the differential positioning error of the airborne receiver based on the historical measured data;

the protection level calculation module is used for calculating a protection level based on the historical measured data;

the fault data set acquisition module is used for extracting a fault data set from the historical measured data based on the differential positioning error and the protection level;

and the fault type determining module is used for extracting fault characteristics of the fault data set and determining the fault type.

9. The fault identification system of claim 8, wherein the historical measured data includes first textual data, first observed data, and second textual data and second observed data provided by the ground reference receiver; the differential positioning error calculation module comprises:

the first sub-calculation module is used for calculating a pseudo-range correction value of the nth satellite and an error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite based on the first text data and the first observation data; wherein, the nth satellite is any one of all satellites;

the second sub-calculation module is used for calculating a pseudo-range measurement value of the airborne receiver and the nth satellite and an error standard deviation of the pseudo-range measurement value of the airborne receiver and the nth satellite based on the second text data and the second observation data; combining the pseudo-range correction value of the nth satellite and the error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite to calculate the position of the airborne receiver;

the third sub-calculation module is used for obtaining the differential positioning error of the airborne receiver based on the calculated position of the airborne receiver and the real position of the airborne receiver; the differential positioning error includes a vertical component and a horizontal component.

10. The fault identification system of claim 9, wherein the protection level calculation module comprises:

the fault-free hypothesis protection level calculation module is used for calculating a fault-free hypothesis protection level by combining a projection matrix from a pseudo-range domain to a positioning domain and a fault-free undetected coefficient based on the pseudo-range correction value error standard deviation between the ground augmentation system and the nth satellite and the pseudo-range measurement value error standard deviation between the airborne receiver and the nth satellite;

the single-receiver fault hypothesis protection level calculation module is used for calculating to obtain a single-receiver fault hypothesis protection level based on a pseudo-range correction value of an nth satellite, a pseudo-range correction value of an mth ground reference receiver and the nth satellite, a pseudo-range correction value error standard deviation of a ground augmentation system and the nth satellite, and a pseudo-range measurement value error standard deviation of an airborne receiver and the nth satellite by combining a projection matrix from a pseudo-range domain to a positioning domain and a missing detection coefficient;

and the protective level result acquisition module is used for comparing the non-fault assumed protective level with the fault assumed protective level of the single receiver to obtain the protective level of the airborne receiver.

Technical Field

The invention relates to the technical field of satellite navigation, in particular to a method and a system for identifying integrity faults of a ground based augmentation system.

Background

As satellite navigation systems enter modern development environments, civil requirements for satellite navigation are becoming important application directions. However, applying satellite navigation systems to civil aviation, it is necessary to first make them meet the civil aviation's performance requirements for navigation systems, including 4 aspects of accuracy, integrity, continuity and availability.

The GBAS airborne equipment calculates the protection level of the airborne differential positioning error according to the parameters in the telegraph text broadcasted by the ground station in real time, and determines whether to alarm or not by comparing the protection level with the alarm line. When GNSS signals are affected by multiple factors from satellites, propagation paths, environment and receivers, etc., it may cause the error characteristic parameters calculated by the GBAS ground station to be inconsistent with the true error characteristics, thus increasing the risk of the actual positioning error of the airborne equipment exceeding the protection level, and such factors are called faults. Moreover, the traditional fault identification method cannot meet the requirement of high precision and can not better identify potential integrity faults, so that the probability of risk generation of the recording user is reduced.

Disclosure of Invention

In view of the foregoing analysis, embodiments of the present invention provide a method and a system for identifying integrity faults of a ground based augmentation system, so as to solve the problem that the existing fault identification method has low accuracy and cannot better identify potential integrity faults.

In one aspect, an embodiment of the present invention provides a method for identifying integrity faults of a ground based augmentation system, including:

acquiring historical measured data provided by a ground reference receiver and an airborne receiver;

based on the historical measured data, calculating a differential positioning error and a protection level of the airborne receiver;

extracting a fault data set from the historical measured data based on the differential positioning error and the protection level;

and extracting fault characteristics of the fault data set and determining the fault type.

Further, the historical measured data comprises first telegraph text data, first observation data and second telegraph text data and second observation data provided by the ground reference receiver; the calculating the differential positioning error of the airborne receiver based on the historical measured data comprises:

calculating a pseudo-range correction value of the nth satellite and an error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite based on the first text data and the first observation data; wherein, the nth satellite is any one of all satellites;

calculating a pseudo-range measurement value of the airborne receiver and the nth satellite and an error standard deviation of the pseudo-range measurement value of the airborne receiver and the nth satellite based on the second text data and the second observation data; combining the pseudo-range correction value of the nth satellite and the error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite to calculate the position of the airborne receiver;

obtaining a differential positioning error of the airborne receiver based on the calculated position of the airborne receiver and the real position of the airborne receiver; the differential positioning error includes a vertical component and a horizontal component.

Further, the calculating a pseudorange correction value for an nth satellite based on the first textual data and the first observation data includes:

acquiring the orbit position of the nth satellite based on the first text data, and acquiring the real distance between the mth ground reference receiver and the nth satellite by combining the real position of the mth ground reference receiver;

obtaining a pseudo-range observation value between the mth ground reference receiver and the nth satellite based on the first observation data, and calculating to obtain a pseudo-range correction value of the mth ground reference receiver and the nth satellite by combining a real distance between the mth ground reference receiver and the nth satellite;

and averaging the pseudo-range correction values of the M ground reference receivers and the nth satellite to obtain the pseudo-range correction value of the nth satellite, wherein M is the number of the ground reference receivers.

Further, based on the historical measured data, a protection level of the computer-mounted receiver comprises:

calculating to obtain a fault-free hypothesis protection level by combining a projection matrix from a pseudo-range domain to a positioning domain and a fault-free missing detection coefficient based on the pseudo-range correction value error standard deviation between the ground augmentation system and the nth satellite and the pseudo-range measurement value error standard deviation between the airborne receiver and the nth satellite;

calculating to obtain a single receiver fault hypothesis protection level based on a pseudo-range correction value of an nth satellite, a pseudo-range correction value of an mth ground reference receiver and the nth satellite, a pseudo-range correction value error standard deviation of a ground augmentation system and the nth satellite, and a pseudo-range measurement value error standard deviation of an airborne receiver and the nth satellite, in combination with a projection matrix from a pseudo-range domain to a positioning domain and a missing detection coefficient;

and comparing the non-fault assumed protection level with the single-receiver fault assumed protection level to obtain the protection level of the airborne receiver.

Further, the protection stages include a vertical protection stage and a horizontal protection stage, and the extracting a fault data set from the historical measured data based on the differential positioning error and the protection stages includes:

and when the vertical component is greater than the vertical protection level and/or the horizontal component is greater than the horizontal protection level, the corresponding historical measured data is a fault data set.

Further, the performing fault feature extraction on the fault data set and determining the fault type includes:

analyzing the fault data set by adopting a statistical method based on the fault data set to determine fault characteristics;

and identifying the fault type according to the fault characteristics.

Further, when the fault feature is a pseudo range correction value vector of the mth reference receiver and N satellites;

and based on the pseudo-range correction value vectors of M ground reference receivers, wherein the pseudo-range correction value vectors of the M ground reference receivers are initial clusters, and when the initial clusters are divided into two clusters with the number of 1 and M-1 respectively by combining a Diana fault identification algorithm, the fault type is a single receiver fault.

In another aspect, an embodiment of the present invention provides a system for identifying integrity failure of a ground based augmentation system, including:

the data acquisition module is used for acquiring historical measured data provided by the ground reference receiver and the airborne receiver;

the differential positioning error calculation module is used for calculating the differential positioning error of the airborne receiver based on the historical measured data;

the protection level calculation module is used for calculating a protection level based on the historical measured data;

the fault data set acquisition module is used for extracting a fault data set from the historical measured data based on the differential positioning error and the protection level;

and the fault type determining module is used for extracting fault characteristics of the fault data set and determining the fault type.

Further, the historical measured data comprises first telegraph text data, first observation data and second telegraph text data and second observation data provided by the ground reference receiver; the differential positioning error calculation module comprises:

the first sub-calculation module is used for calculating a pseudo-range correction value of the nth satellite and an error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite based on the first text data and the first observation data; wherein, the nth satellite is any one of all satellites;

the second sub-calculation module is used for calculating a pseudo-range measurement value of the airborne receiver and the nth satellite and an error standard deviation of the pseudo-range measurement value of the airborne receiver and the nth satellite based on the second text data and the second observation data; combining the pseudo-range correction value of the nth satellite and the error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite to calculate the position of the airborne receiver;

the third sub-calculation module is used for obtaining the differential positioning error of the airborne receiver based on the calculated position of the airborne receiver and the real position of the airborne receiver; the differential positioning error includes a vertical component and a horizontal component.

Further, the protection level calculation module includes:

the fault-free hypothesis protection level calculation module is used for calculating a fault-free hypothesis protection level by combining a projection matrix from a pseudo-range domain to a positioning domain and a fault-free undetected coefficient based on the pseudo-range correction value error standard deviation between the ground augmentation system and the nth satellite and the pseudo-range measurement value error standard deviation between the airborne receiver and the nth satellite;

the single-receiver fault hypothesis protection level calculation module is used for calculating to obtain a single-receiver fault hypothesis protection level based on a pseudo-range correction value of an nth satellite, a pseudo-range correction value of an mth ground reference receiver and the nth satellite, a pseudo-range correction value error standard deviation of a ground augmentation system and the nth satellite, and a pseudo-range measurement value error standard deviation of an airborne receiver and the nth satellite by combining a projection matrix from a pseudo-range domain to a positioning domain and a missing detection coefficient;

and the protective level result acquisition module is used for comparing the non-fault assumed protective level with the fault assumed protective level of the single receiver to obtain the protective level of the airborne receiver.

Compared with the prior art, the invention can at least realize the following beneficial effects:

according to the method and the device, the fault data set is extracted based on historical measured data, so that the fault characteristics are extracted and the fault type is identified, the micro fault which is not discovered yet in an actual scene can be discovered, and the requirement for potential integrity fault identification is met.

In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.

FIG. 1 is a flow chart illustrating a method for identifying integrity faults of a ground based augmentation system according to an embodiment of the present disclosure;

FIG. 2 is a schematic structural diagram of a system for identifying integrity failure of a ground based augmentation system according to an embodiment of the present disclosure.

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.

In one aspect, the present application discloses a method for identifying integrity failure of a ground based augmentation system, as shown in fig. 1. The method comprises the following steps:

step S1: acquiring historical measured data provided by a ground reference receiver and an airborne receiver;

step S2: based on the historical measured data, calculating a differential positioning error and a protection level of the airborne receiver;

step S3: extracting a fault data set from the historical measured data based on the differential positioning error and the protection level;

step S4: and extracting fault characteristics of the fault data set and determining the fault type.

Compared with the prior art, the method for identifying the integrity fault of the foundation enhancement system provided by the embodiment extracts the fault data set based on the historical measured data, further extracts the fault characteristics and identifies the fault type, can find the micro fault which is not found in the actual scene, and meets the requirement of identifying the potential integrity fault.

In a specific embodiment, the historical measured data includes first textual data, first observed data, and second textual data and second observed data provided by the ground reference receiver; the calculating the differential positioning error of the airborne receiver based on the historical measured data comprises:

step S21: calculating a pseudo-range correction value of the nth satellite and an error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite based on the first text data and the first observation data; wherein, the nth satellite is any one of all satellites; step S21 includes:

step S211: acquiring the orbit position of the nth satellite based on the first text data, and acquiring the real distance between the mth ground reference receiver and the nth satellite by combining the real position of the mth ground reference receiver;

step S212: obtaining a pseudo-range observation value between the mth ground reference receiver and the nth satellite based on the first observation data, and calculating to obtain a pseudo-range correction value of the mth ground reference receiver and the nth satellite by combining a real distance between the mth ground reference receiver and the nth satellite;

see formula (1):

ρ_c,m,n＝r_m,n-ρ_m,n (1)

wherein r is_m,nIs the true distance, p, between the mth terrestrial reference receiver and the nth satellite_m,nIs a pseudorange observation, p, between the mth terrestrial reference receiver and the nth satellite_c,m,nIs the pseudorange correction for the mth terrestrial reference receiver and the nth satellite.

Further, the pseudorange correction value of the mth terrestrial reference receiver and the nth satellite satisfies formula (2):

ρ_c,m,n＝c_n+ε_m,n (2)

wherein, c_nFor the common pseudo-range errors between the ground reference receiver and the airborne receiver about the nth satellite, including the clock error, the ephemeris error, the ionosphere error and the troposphere error, these errors in the observations of the airborne receiver and the ground reference receiver can be considered to be the same due to the small service range of the GBAS, epsilon_m,nIs the uncorrelated error of the mth terrestrial reference receiver and the airborne receiver, including thermal noise and multipath error, which can be described by a zero-mean gaussian distribution, see the following formula (3):

ε_m,n～N(0,σ_m,n) (3)

wherein σ_m,nIs the standard deviation of the pseudorange correction values of the mth terrestrial reference receiver and the nth satellite, is a function of the elevation angle of the satellite, and because the distance between the antennas of the terrestrial reference receivers is negligibly small compared with the distance from the antennas of the terrestrial reference receivers to the satellite, the sigma of the M terrestrial reference receivers of the GBAS_m,nThe same is true.

Step S213: and averaging the pseudo-range correction values of the M ground reference receivers and the nth satellite to obtain the pseudo-range correction value of the nth satellite, wherein M is the number of the ground reference receivers.

Specifically, the pseudorange correction value of the nth satellite is calculated according to the formula (4):

order toε_gnd,nPseudorange corrected value error for terrestrial augmentation system and nth satellite, and_gnd,nfollowing a zero mean gaussian distribution, see equation (5) below:

ε_gnd,n～N(0,σ_gnd,n) (5)

wherein the content of the first and second substances,σ_gnd,nthe pseudorange correction value error standard deviation of the ground augmentation system and the nth satellite is related to the elevation angle of the satellite, and can be obtained through pseudo range correction value error envelope statistics of the ground augmentation system and the nth satellite according to long-time observation data in an actual scene or is given by an RTCA standard file.

Step S22: calculating a pseudo-range measurement value of the airborne receiver and the nth satellite and an error standard deviation of the pseudo-range measurement value of the airborne receiver and the nth satellite based on the second text data and the second observation data; combining the pseudo-range correction value of the nth satellite and the error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite to calculate the position of the airborne receiver;

specifically, the satellite position may be calculated according to the second text data, and the pseudorange measurement ρ between the airborne receiver and the nth satellite may be obtained according to the second observation data provided by the airborne receiver_air,n，ρ_air,nSatisfies formula (6):

ρ_air,n＝r_air,n+c_n+ε_air,n (6)

wherein r is_air,nIs the true distance, ε, from the airborne receiver to the nth satellite_air,nIs the pseudorange measurement error, ε, of the airborne receiver and the nth satellite_air,nA gaussian distribution that fits a zero mean, see formula (7) below:

ε_air,n～N(0,σ_air,n) (7)

wherein σ_air,nIs the pseudorange measurement error standard deviation of the airborne receiver and the nth satellite.

Obtaining a pseudorange measurement value rho after correction of the airborne receiver and the nth satellite according to a formula (8)_n：

ρ_n＝ρ_air,n-ρ_c,n＝r_air,n+(ε_air,n-ε_gnd,n) (8)

Let P be [ rho₁,...,ρ_N]And correcting the pseudo range vectors of the N satellites for the airborne receiver.

Calculating the position X of the airborne receiver according to equation (9):

X＝(G^TWG)^-1G^TWP (9)

wherein X ═ X, y, z, b ] is the position of the airborne receiver and the clock difference vector, G is the orientation cosine matrix of the N satellites relative to the position of the airborne receiver, and since the solving process is iterative calculation, it can be calculated from the satellite position and the position solution of each iteration of the airborne receiver, W is the weighting matrix defined as:

wherein σ_nThe pseudorange difference of the airborne receiver to the nth satellite is corrected for the error standard deviation, which can be calculated according to the formula (10):

wherein σ_iono,nIs the residual ionospheric error standard deviation, σ, of the nth satellite_tropo,nThe standard deviation of the residual tropospheric error for the nth satellite can be calculated by the formula in the RTCA standard.

Step S23: obtaining a differential positioning error of the airborne receiver based on the calculated position of the airborne receiver and the real position of the airborne receiver; the differential positioning error includes a vertical component and a horizontal component.

Specifically, the calculated position X of the airborne receiver is compared with the real position of the airborne receiver to obtain a differential positioning error epsilon_pThe differential positioning error includes a vertical component and a horizontal component.

In a specific embodiment of the present invention, based on the historical measured data, a protection level of a computer-mounted receiver comprises:

step S24: calculating to obtain a fault-free hypothesis protection level by combining a projection matrix from a pseudo-range domain to a positioning domain and a fault-free missing detection coefficient based on the pseudo-range correction value error standard deviation between the ground augmentation system and the nth satellite and the pseudo-range measurement value error standard deviation between the airborne receiver and the nth satellite;

specifically, the pseudo-range correction value error standard deviation sigma based on the ground enhancement system and the nth satellite_gnd,nAnd the pseudorange measurement error standard deviation sigma of the airborne receiver and the nth satellite_air,nObtaining σ according to equation (10)_nAnd will not be described in detail herein.

The protection stages include a vertical protection stage (VPL) and a horizontal protection stage (HPL), and the vertical protection stage is described as an example below:

computing fault-free vertical protection level VPL_H0The process of (2) is as follows:

according to the formula (11), the standard deviation sigma of the positioning error in the vertical direction is calculated_vThe positioning error in the vertical direction follows a gaussian distribution, the standard deviation of which is determined by the projection matrix S, S ═ G^TWG)^-1G^TW, S is the projection matrix of the pseudorange correction error from the pseudorange domain to the location domain:

wherein S is_v,nThe element in the 3 rd row and the nth column in S represents the projection coefficient of the pseudo-range correction error of the nth satellite to the positioning error in the vertical direction.

Calculating a fault-free vertical protection level according to equation (12):

VPL_H0＝k_ffmdσ_v (12)

wherein k is_ffmdFor no fault missing coefficient, k_ffmd＝Q^-1(P_ffmd/2) wherein P_ffmdFor the probability of failure-free missed detection, the definition of the Q function is as follows:

further, a fault-free horizontal protection stage HPL_H0Please refer to the non-fault VPL_H0The above process is not described herein.

Step S25: calculating to obtain a single receiver fault hypothesis protection level based on a pseudo-range correction value of an nth satellite, a pseudo-range correction value of an mth ground reference receiver and the nth satellite, a pseudo-range correction value error standard deviation of a ground augmentation system and the nth satellite, and a pseudo-range measurement value error standard deviation of an airborne receiver and the nth satellite, in combination with a projection matrix from a pseudo-range domain to a positioning domain and a missing detection coefficient;

specifically, a VPL (virtual private LAN) for calculating the fault of a single receiver_H1The process of (2) is as follows:

calculating a B value according to equation (13), the B value being an estimate of the deviation of the positioning error if the mth terrestrial reference receiver fails:

where ρ is_c,i,nObserved for ith terrestrial reference receiverPseudorange correction values for n satellites, B_m,nThe optimal estimate of the bias of the pseudorange correction errors for the mth terrestrial reference receiver to the nth satellite also follows a Gaussian distribution, i.e.

Calculating the single-receiver fault vertical protection level VPL according to the formulas (14), (15) and (16)_H1：

Wherein, VPL_H1,mA vertical protection level calculated for the mth ground reference receiver fault; sigma_H1,nCorrecting error standard deviation for the pseudo-range difference of the airborne receiver to the nth satellite under the fault of the single receiver, and referring to a formula (15); k is a radical of_md＝Q^-1(P_mdPer 2), as missing detection coefficient, P_mdIs the probability of dangerous misleading information allowed under a single receiver fault, and is also called the miss probability.

Further, a single receiver fault level protection level HPL_H1Please refer to the VPL of the single-receiver fault vertical protection level_H1The above process is not described herein.

Step S26: and comparing the non-fault assumed protection level with the single-receiver fault assumed protection level to obtain the protection level of the airborne receiver.

In particular, the fault-free vertical protection stage VPL_H0VPL (virtual private LAN) with single receiver fault vertical protection level_H1Comparing, and selecting a larger vertical protection level of the airborne receiver; protection level HPL without fault_H0HPL (protection level for single receiver fault level)_H1Comparing, selecting larger horizontal protection level of the airborne receiver to obtain the protection level of the airborne receiverThe receiver-dependent protection stages include a horizontal protection stage and a vertical protection stage.

In a specific embodiment, said extracting a fault data set from said historical measured data based on said differential positioning error and said protection level comprises:

and when the vertical component is greater than the vertical protection level and/or the horizontal component is greater than the horizontal protection level, the corresponding historical measured data is a fault data set.

Specifically, the historical measured data set is composed of data of a plurality of different time periods, the calculation process is carried out on the data set of each time period to obtain the differential positioning error and the protection level of the airborne receiver, the vertical component of the differential positioning error of each time period is compared with the vertical protection level, when the vertical component is larger than the vertical protection level, and/or the horizontal component of the differential positioning error of the time period is compared with the horizontal protection level, and when the horizontal component is larger than the horizontal protection level, the data corresponding to the time period is fault data.

Further, the above process is performed on the data in all the historical time periods, and whether the data in each time period is the fault data is judged, so that all the fault data can be selected from the historical data set to form a fault data set.

In a specific embodiment, the performing the fault feature extraction on the fault data set and determining the fault type includes:

analyzing the fault data set by adopting a statistical method based on the fault data set to determine fault characteristics;

and identifying the fault type according to the fault characteristics.

Specifically, on the basis of the fault data set, mining processing is performed on original data, intermediate processing results and the like of the fault data set by adopting a statistical method, characteristics capable of reflecting fault influences and sources are extracted to serve as fault characteristics, and fault types are determined on the basis of the extracted fault characteristics. The specific statistical method can be determined according to the actual situation of the fault data set, and the method is not limited in the application; the fault type corresponding to each fault feature may be one or more, and the application is not limited thereto.

In a specific embodiment, when the fault is characterized by a pseudo-range correction value vector of the mth ground reference receiver and N satellites;

and based on the pseudo-range correction value vectors of M ground reference receivers, wherein the pseudo-range correction value vectors of the M ground reference receivers are initial clusters, and when the initial clusters are divided into two clusters with the number of 1 and M-1 respectively by combining a Diana fault identification algorithm, the fault type is a single receiver fault.

Specifically, a statistical method is adopted to analyze a fault data set, and when the fault characteristic is that the mth ground reference receiver and pseudo-range correction value vector rho of N satellites_c,m＝[ρ_c,m,1,...,ρ_c,m,N]^TThen, the specific process of identifying the fault type by combining the Diana fault identification algorithm is as follows:

(1) taking the pseudo-range correction value vectors of the M ground reference receivers as an initial cluster, calculating the weighted distance between any two samples in the cluster according to a formula (16) and a formula (17), and solving the average value of the weighted distance between each sample and other M-1 samples, which is also called average dissimilarity:

d_i,j＝||w*(ρ_c,i-ρ_c,j)||₂,0＜i,j≤M (16)

wherein d is_i,jWeighting the distance between the ith ground reference receiver and the jth ground reference receiver; rho_c,iAnd ρ_c,jComputing pseudo-range correction value vectors of the ith and j ground reference receivers; w ═ w₁；...；w_n]^-1N is a weight vector which is normalized after subtracting pseudo-range errors of two ground reference receivers at different elevation angles, wherein,

wherein the content of the first and second substances,is the average degree of dissimilarity of the mth terrestrial reference receiver, d_m,jIs the weighted distance of the mth terrestrial reference receiver from the jth terrestrial reference receiver.

(2) Taking the ground reference receiver sample with the maximum average dissimilarity as a first fault receiver which is split into an initial cluster, and executing the iteration steps of a Diana clustering algorithm: traversing the rest receiver samples in the initial cluster, if the closest distance from a certain sample to the split sample is less than the closest distance to other samples in the initial cluster, dividing the sample into the split cluster, and circulating the iteration step until the split does not change any more, thereby finishing the final classification.

(3) And when the final classification is finished and the number of the two clusters is respectively 1 and M-1, judging that the fault is a single receiver fault and identifying that the fault receiver is a ground reference receiver corresponding to the cluster with the number of 1.

In another aspect, the present application discloses a system for identifying integrity faults of a ground based augmentation system, comprising:

the data acquisition module is used for acquiring historical measured data provided by the ground reference receiver and the airborne receiver;

the differential positioning error calculation module is used for calculating the differential positioning error of the airborne receiver based on the historical measured data;

the protection level calculation module is used for calculating a protection level based on the historical measured data;

the fault data set acquisition module is used for extracting a fault data set from the historical measured data based on the differential positioning error and the protection level;

and the fault type determining module is used for extracting fault characteristics of the fault data set and determining the fault type.

Compared with the prior art, the integrity fault identification system of the foundation enhancement system provided by the embodiment extracts the fault data set based on the historical measured data by combining the data acquisition module, the differential positioning error calculation module, the protection level calculation module, the fault data set acquisition module and the fault type determination module, further extracts the fault characteristics and identifies the fault type, can find the micro fault which is not found in the actual scene, and meets the requirement of potential integrity fault identification.

In a specific embodiment, the historical measured data includes first textual data, first observed data, and second textual data and second observed data provided by the ground reference receiver; the differential positioning error calculation module comprises:

the first sub-calculation module is used for calculating a pseudo-range correction value of the nth satellite and an error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite based on the first text data and the first observation data; wherein, the nth satellite is any one of all satellites;

the second sub-calculation module is used for calculating a pseudo-range measurement value of the airborne receiver and the nth satellite and an error standard deviation of the pseudo-range measurement value of the airborne receiver and the nth satellite based on the second text data and the second observation data; combining the pseudo-range correction value of the nth satellite and the error standard deviation of the pseudo-range correction value of the ground augmentation system and the nth satellite to calculate the position of the airborne receiver;

the third sub-calculation module is used for obtaining the differential positioning error of the airborne receiver based on the calculated position of the airborne receiver and the real position of the airborne receiver; the differential positioning error includes a vertical component and a horizontal component.

In a specific embodiment, the protection level calculation module includes:

the fault-free hypothesis protection level calculation module is used for calculating a fault-free hypothesis protection level by combining a projection matrix from a pseudo-range domain to a positioning domain and a fault-free undetected coefficient based on the pseudo-range correction value error standard deviation between the ground augmentation system and the nth satellite and the pseudo-range measurement value error standard deviation between the airborne receiver and the nth satellite;

the single-receiver fault hypothesis protection level calculation module is used for calculating to obtain a single-receiver fault hypothesis protection level based on a pseudo-range correction value of an nth satellite, a pseudo-range correction value of an mth ground reference receiver and the nth satellite, a pseudo-range correction value error standard deviation of a ground augmentation system and the nth satellite, and a pseudo-range measurement value error standard deviation of an airborne receiver and the nth satellite by combining a projection matrix from a pseudo-range domain to a positioning domain and a missing detection coefficient;

and the protective level result acquisition module is used for comparing the non-fault assumed protective level with the fault assumed protective level of the single receiver to obtain the protective level of the airborne receiver.

Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.