CN113777630B - Fault monitoring method and system for single receiver of ground-based augmentation system - Google Patents
Fault monitoring method and system for single receiver of ground-based augmentation system Download PDFInfo
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Abstract
The invention relates to a single receiver fault detection method and a single receiver fault detection system for a ground-based augmentation system, belongs to the technical field of satellite navigation, and solves the problems of complexity and low sensitivity of the single receiver fault detection method. Acquiring historical data of the M reference receivers at different moments when the M reference receivers work normally to obtain test statistics of the M reference receivers at different moments; classifying the test statistics of M reference receivers at different times according to the number of the visible satellites at different times to respectively obtain test statistic sample sequences under the number of each visible satellite, and calculating a threshold value under the number of each visible satellite according to the false alarm rate; the method comprises the steps of obtaining real-time data of M reference receivers, calculating test statistics of the M reference receivers at the current moment, and judging whether single receiver faults exist at the current moment or not by combining a threshold value under the number of visible satellites at the current moment. The method simplifies the logic judgment execution process and has higher fault detection speed.
Description
Technical Field
The invention relates to the technical field of satellite navigation, in particular to a fault monitoring method and system for a single receiver of a ground-based augmentation system.
Background
As Global Navigation Satellite Systems (GNSS) enter modern development environments, civil requirements for satellite navigation are becoming increasingly important directions of application. However, applying satellite navigation systems to civil aviation must first be made to meet the civil aviation performance requirements for navigation systems, including 4 aspects of accuracy, integrity, continuity and availability, Ground Based Augmentation Systems (GBAS) are considered as GNSS augmentation systems with the highest potential to meet the requirements of the near three categories of civil aviation precision.
The GBAS applied to civil aviation broadcasts differential correction information through a ground subsystem, and the airplane performs differential positioning after receiving the information. Meanwhile, the GBAS carries out integrity monitoring on the basis of differential correction, different monitoring algorithms are designed for different fault sources by a monitoring model, for single-receiver faults, the LAAS developed by FAA adopts a multi-reference receiver consistency Monitoring (MRCC) algorithm, abnormal channels are marked by calculating the comparison of a B value and a threshold value thereof, and then the receiver channels with larger deviation generated in the differential correction process are eliminated by executing logic judgment, so that the reliability of pseudo-range correction values broadcast by the GBAS is ensured.
The MRCC algorithm is not fast enough to detect the single receiver fault, and at the same time, a logic judgment process needs to be executed to process the channel marked by the B value and its state value, which is relatively complex, and under the requirements of three types of precision approaches, the requirement for the alarm time in the integrity index is shortened, and a more sensitive single receiver fault monitoring algorithm needs to be provided.
Disclosure of Invention
In view of the foregoing analysis, embodiments of the present invention provide a method and a system for monitoring a fault of a single receiver of a ground based augmentation system, so as to solve the problem that the existing method for monitoring a fault of a single receiver is complex and has low sensitivity.
In one aspect, an embodiment of the present invention provides a method for monitoring a fault of a single receiver of a ground-based augmentation system, including:
acquiring historical data of the M reference receivers at different moments when the M reference receivers work normally to obtain test statistics S of the M reference receivers at different moments;
classifying the test statistics S of the M reference receivers at different moments by combining the number of the visible satellites at different moments to respectively obtain test statistics S sample sequences under the number of the visible satellites;
calculating the threshold value of the test statistic under each visible satellite quantity based on the test statistic S sample sequence under each visible satellite quantity and combining the false alarm rate;
and acquiring real-time data of M reference receivers, calculating test statistics S' of the M reference receivers at the current moment, and judging whether a single receiver fault exists at the current moment or not by combining the threshold value of the test statistics under the quantity of visible satellites corresponding to the current moment.
Further, the obtaining of the historical data of the M reference receivers at different times when the M reference receivers normally operate to obtain the test statistic S of the M reference receivers at different times includes:
acquiring historical data of the M reference receivers at different moments when the reference receivers work normally, and calculating pseudo-range correction value vectors of the M reference receivers at different moments, wherein M is the number of the reference receivers;
and calculating test statistic S of the M reference receivers at a certain moment based on the pseudo-range correction value vectors of the M reference receivers at the certain moment and the normalized weight vector w.
Further, calculating pseudo-range correction value vectors of M reference receivers at different time instants, comprising:
acquiring pseudo-range correction values of the mth reference receiver and each satellite at different moments based on the measured data provided by the mth reference receiver at different moments and the actual position of the mth reference receiver;
obtaining a pseudo-range correction value vector of the mth reference receiver at different time based on the pseudo-range correction values of the mth reference receiver at different time and each satellite;
the mth reference receiver is any one of the M reference receivers.
Further, the normalized weight vector w is calculated according to the following formula:
wherein σgnd＝[σgnd,1,...,σgnd,N]TPseudo-range correction value error standard deviation vectors of the foundation enhancement system and the N visible satellites; sigmagnd,nThe pseudo range correction value error standard deviation of the foundation enhancement system and the nth visible satellite.
Further, the calculating a test statistic S of the M reference receivers at a certain time based on the pseudorange correction value vectors of the M reference receivers at the certain time in combination with the normalized weight vector w includes:
calculating a difference vector of the pseudo-range correction value vector of the mth reference receiver at the moment and an average value vector of the pseudo-range correction value vectors of other reference receivers;
based on the difference vector and in combination with the normalized weight vector w, calculating to obtain a test statistic S of the mth reference receiver at the momentm。
Further, the calculation obtains the test statistic S of the mth reference receiver at the momentmThe method comprises the following steps:
calculating S according to the following formulam：
Pc,m＝[ρc,m,1,...,ρc,m,n,...,ρc,m,N]TA pseudorange correction value vector representing the mth reference receiver at that time; pc,j＝[ρc,j,1,...,ρc,j,n,...,ρc,j,N]TJ ∈ M, j ≠ M, which represents the pseudorange correction value vector of the jth reference receiver except the mth reference receiver at the moment.
Further, the calculating the threshold value of the test statistic based on the test statistic S sample sequence under each visible satellite quantity and the false alarm rate includes:
calculating a probability density function of a test statistic S based on the test statistic S sample sequence when the number of visible satellites is N;
enveloping the probability density function of the test statistic S by using a probability density function of chi-square distribution with the degree of freedom N, wherein N is the number of satellites;
and if the tail part of the probability density function of the chi-square distribution with the degree of freedom N can envelop the tail part of the probability density function of the test statistic S, calculating a threshold value when the number of the visible satellites is N according to the probability density function of the chi-square distribution with the degree of freedom N and the false alarm rate.
Further, the calculating the threshold value of the test statistic based on the statistic S sample sequence under each quantity of visible satellites in combination with the false alarm rate further includes:
if the tail part of the probability density function of chi-square distribution with the degree of freedom N can not envelop the tail part of the probability density function of the test statistic S, enveloping the probability density function of the test statistic S by adopting the probability density function of gamma distribution;
continuously adjusting the values of alpha and beta in the probability density function of gamma distribution until the tail of the probability density function of gamma distribution envelopes the tail of the probability density function of the test statistic S to obtain the adjusted probability density function of gamma distribution;
and calculating a threshold value when the number of the visible satellites is N according to the adjusted probability density function of gamma distribution and the false alarm rate.
Further, the acquiring real-time data of the M reference receivers, calculating test statistics S' of the M reference receivers, and determining whether a single receiver fault exists at the current time by combining a threshold value of the test statistics of the number of visible satellites corresponding to the current time includes:
when the test statistic S 'of at least one reference receiver in the M reference receivers is larger than the threshold value of the test statistic under the number of visible satellites corresponding to the current moment, the reference receiver corresponding to the largest test statistic in the test statistic S' of the at least one reference receiver is removed;
and recalculating the test statistic of the rest reference receivers, comparing the recalculated test statistic with the threshold value of the test statistic of the number of the visible satellites corresponding to the current moment, and if the test statistic of the rest reference receivers is less than or equal to the threshold value of the test statistic of the number of the visible satellites corresponding to the current moment, judging that the single receiver fault exists at the current moment.
In another aspect, an embodiment of the present invention provides a system for monitoring a fault of a single receiver of a ground-based augmentation system, where the system includes:
the test statistic acquisition module is used for acquiring historical data of the M reference receivers at different moments when the M reference receivers work normally to obtain test statistics S of the M reference receivers at different moments;
the test statistic classification module is used for classifying the test statistics S of the M reference receivers at different moments by combining the number of the visible satellites at different moments to respectively obtain test statistic S sample sequences under the number of the visible satellites;
the threshold value calculation module is used for calculating the threshold value of the test statistic amount under each visible satellite number based on the test statistic amount S sample sequence under each visible satellite number and by combining the false alarm rate;
and the single receiver fault judgment module is used for acquiring real-time data of the M reference receivers, calculating the test statistic S' of the M reference receivers at the current moment, and judging whether a single receiver fault exists at the current moment by combining the threshold value of the test statistic under the quantity of the visible satellites corresponding to the current moment.
Compared with the prior art, the invention can at least realize the following beneficial effects:
the method comprises the steps of obtaining test statistics of M reference receivers at different moments based on historical data of the M reference receivers at different moments when the M reference receivers work normally, respectively obtaining the test statistics under the quantity of each visible satellite according to the quantity of the visible satellites, respectively obtaining threshold values of the test statistics under the quantity of each visible satellite according to a false alarm rate, and further detecting whether a single receiver fault exists at a certain moment in real time; the single receiver fault monitoring method integrates the additional errors of the reference receiver fault on all satellite channels, amplifies the influence of the fault, simplifies the execution logic judgment process and has higher fault detection speed.
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 of a single receiver fault monitoring method of a ground based augmentation system according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a single receiver fault monitoring system of a ground based augmentation system according to an embodiment of the present application.
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, a specific embodiment of the present invention discloses a method for monitoring a fault of a single receiver of a ground based augmentation system, and a flow diagram of the method is shown in fig. 1.
The method comprises the following steps:
step S10: acquiring historical data of the M reference receivers at different moments when the M reference receivers work normally to obtain test statistics S of the M reference receivers at different moments;
step S20: classifying the test statistics S of the M reference receivers at different moments by combining the number of the visible satellites at different moments to respectively obtain test statistics S sample sequences under the number of the visible satellites;
step S30: calculating the threshold value of the test statistic under each visible satellite quantity based on the test statistic S sample sequence under each visible satellite quantity and combining the false alarm rate;
step S40: and acquiring real-time data of M reference receivers, calculating test statistics S' of the M reference receivers at the current moment, and judging whether a single receiver fault exists at the current moment or not by combining the threshold value of the test statistics under the quantity of visible satellites corresponding to the current moment.
Compared with the prior art, the method and the device have the advantages that the test statistic of the M reference receivers at different moments is obtained based on the historical data of the M reference receivers at different moments when the M reference receivers work normally, the test statistic of each visible satellite is obtained by combining the number of the visible satellites, the threshold value of the test statistic of each visible satellite is obtained by combining the false alarm rate, and whether a single receiver fault exists at a certain moment is monitored in real time; the single receiver fault monitoring method integrates the additional errors of the reference receiver fault on all satellite channels, amplifies the influence of the fault, simplifies the execution logic judgment process and has higher fault detection speed.
In a specific embodiment, step S10 includes:
step S11: acquiring historical data of the M reference receivers at different moments when the reference receivers work normally, and calculating pseudo-range correction value vectors of the M reference receivers at different moments, wherein M is the number of the reference receivers;
further, step S11 includes:
step S111: and obtaining pseudo-range correction values of the mth reference receiver and each satellite at different moments based on the measured data provided by the mth reference receiver at different moments and the actual position of the mth reference receiver.
Further, the measured data includes telegraph text data and observation data, the telegraph text data includes ephemeris data, and the observation data includes pseudo range and carrier phase.
Step S111 includes:
step S1111: acquiring the orbit position of each satellite at different moments based on the text data, and acquiring the real distance between the mth reference receiver and each satellite at different moments by combining the actual position of the mth reference receiver;
step S1112: obtaining pseudo-range observation values between the mth reference receiver and each satellite at different moments based on the observation data;
step S1113: and calculating the pseudo-range correction value of the mth reference receiver and each satellite at different moments based on the real distance between the mth reference receiver and each satellite at different moments and the pseudo-range observation value.
Specifically, for an mth reference receiver and an nth satellite at a certain time, please refer to formula (1):
ρc,m,n＝rm,n-ρm,n (1)
wherein r ism,nIs the true distance, p, between the mth reference receiver and the nth satellite at that timem,nIs the pseudorange observation, p, between the mth reference receiver and the nth satellite at that timec,m,nIs the pseudorange correction for the mth reference receiver and the nth satellite at that time.
Further, the pseudorange correction values of the mth reference receiver and the nth satellite satisfy formula (2):
ρc,m,n＝cn+εm,n (2)
wherein, cnFor common pseudo-range errors between the reference receiver and the airborne receiver with respect to the nth satellite, including clock error, starThe errors in observations of the airborne receiver and the reference receiver can be considered to be the same, epsilon, due to the small GBAS service rangem,nIs the uncorrelated error of the mth 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):
εm,n～N(0,σm,n) (3)
wherein σm,nIs the pseudorange correction value error standard deviation of the mth reference receiver and the nth satellite, is a function of the satellite elevation angle, and because the distance between the reference receiver antennas is negligibly small compared with the distance between the reference receiver antennas and the satellites, the sigma of the M terrestrial reference receivers of the GBASm,nThe same is true.
For the calculation process of the pseudo-range correction value between the mth reference receiver and each satellite at the time and the calculation process of the pseudo-range correction value between the M reference receivers and each satellite at different times, reference may be made to the calculation process of the pseudo-range correction value between the mth reference receiver and the nth satellite at the time, which is not described herein again.
Step S112: and obtaining a pseudo-range correction value vector of the mth reference receiver at different time based on the pseudo-range correction value of the mth reference receiver at different time and each satellite.
Specifically, taking the number of satellites as N for example, the pseudo-range correction values ρ between the mth reference receiver and the N satellites at a certain time are obtained through steps S1111 to S1113 respectivelyc,m,1,...,ρc,m,NAnd further form a pseudo-range correction value vector P of the mth reference receiver at a certain momentc,m＝[ρc,m,1,...,ρc,m,N]TWhere ρ isc,m,1For pseudorange corrections between the mth reference receiver and the 1 st satellite at a time, pc,m,NAnd obtaining pseudorange correction value vectors of the M reference receivers at different times for the pseudorange correction value between the mth reference receiver and the nth satellite at a certain time in the same way, which is not described herein again.
Step S12: and calculating test statistic S of the M reference receivers at a certain moment based on the pseudo-range correction value vectors of the M reference receivers at the certain moment and the normalized weight vector w.
In a specific embodiment, step S12 includes:
step S121: calculating a difference vector of the pseudo-range correction value vector of the mth reference receiver at the moment and an average value vector of the pseudo-range correction value vectors of other reference receivers;
step S122: based on the difference vector, combining with the normalized weight vector w, calculating to obtain the test statistic S of the mth reference receiverm。
Specifically, the test statistic S of the mth reference receiver at the moment is calculated according to the formula (4)m：
Wherein, Pc,m＝[ρc,m,1,...,ρc,m,n,...,ρc,m,N]TA pseudorange correction value vector representing the mth reference receiver at that time; pc,j＝[ρc,j,1,...,ρc,j,n,...,ρc,j,N]TJ ∈ M, j ≠ M, which represents the pseudorange correction value vector of the jth reference receiver except the mth reference receiver at the moment.
Further, the normalized weight vector w satisfies formula (5):
wherein σgnd＝[σgnd,1,...,σgnd,N]TPseudo-range correction value error standard deviation vectors of the foundation enhancement system and the N visible satellites;
σgnd,npseudo range corrected value error standard deviation of foundation enhancement system and nth visual satellite, and satelliteThe elevation angle of the satellite is related, and the satellite elevation angle can be obtained by pseudo-range correction value error envelope statistics of a foundation enhancement system and an nth satellite according to long-time observation data in an actual scene, or is given by an RTCA standard file.
Furthermore, the detection statistics of the M reference receivers at each moment can be calculated through the above steps, the test statistics of the M reference receivers at multiple moments in the selected time period can be calculated, the test statistics S of the M reference receivers at different moments can be obtained, and the specific time interval between the moments can be determined according to the actual situation.
In a specific embodiment, step S20 includes:
acquiring the number of visible satellites at different moments;
and classifying the test statistics of the M reference receivers at different moments based on the number of the visible satellites at different moments to obtain a test statistic S sample sequence under each visible satellite number.
Specifically, the number of the visible satellites corresponding to each time may be the same or different, and on the premise of obtaining the test statistics of the M reference receivers at different times, the test statistics belonging to the same number of the visible satellites are classified into one class, so as to obtain the test statistics S sample sequence corresponding to each number of the visible satellites.
In a specific embodiment, step S30 includes:
step S31: calculating a probability density function of a test statistic S based on the sequence of test statistic S samples when the number of visible satellites is N.
Step S32: and enveloping the probability density function of the test statistic S by using the probability density function of chi-square distribution with the degree of freedom N, wherein N is the number of satellites.
Step S33: and if the tail part of the probability density function of the chi-square distribution with the degree of freedom N can envelop the tail part of the probability density function of the test statistic S, calculating a threshold value when the number of the visible satellites is N according to the probability density function of the chi-square distribution with the degree of freedom N and the false alarm rate.
Specifically, each of the numbers of the visible satellites classified in step S20 corresponds to a threshold value.
Further, the false alarm rate can be determined according to the actual demand of the system, and optionally, the false alarm rate is 1.9732 × 10-9。
Specifically, the probability density function of the chi-square distribution with the degree of freedom N is shown in formula (6):
wherein S is greater than 0.
When the tail of the probability density function (formula (6)) of the chi-square distribution with the degree of freedom N can envelop the tail of the probability density function of the test statistic S, calculating that the tail probability of the chi-square distribution with the degree of freedom N is equal to the quantile of the false alarm rate, namely when the tail probability of the probability density function with the degree of freedom N is equal to the false alarm rate, the value of the corresponding abscissa is the threshold value when the number of the visible satellites is N. Furthermore, the fact that the tail of the probability density function of the chi-square distribution with the degree of freedom N can envelop the tail of the probability density function of the test statistic S means that the enveloping effect is good, that is, the tail of the probability density function of the chi-square distribution with the degree of freedom N is completely above the tail of the probability density function of the test statistic S, the tail of the probability density function of the chi-square distribution with the degree of freedom N does not excessively expand, and the shape of the probability density function of the chi-square distribution with the degree of freedom N is more fitted with the shape of the probability density function of the test statistic S.
In a specific embodiment, step S30 further includes:
step S34: if the tail part of the probability density function of chi-square distribution with the degree of freedom N can not envelop the tail part of the probability density function of the test statistic S, enveloping the probability density function of the test statistic S by adopting the probability density function of gamma distribution;
step S35: continuously adjusting the values of alpha and beta in the probability density function of gamma distribution until the tail of the probability density function of gamma distribution envelops the tail of the probability density function of the test statistic S to obtain the probability density function of gamma distribution after adjustment;
step S36: and calculating a threshold value when the number of the visible satellites is N according to the adjusted probability density function of gamma distribution and the false alarm rate.
Specifically, the probability density function γ (α, β) of the gamma distribution is shown in formula (7):
wherein the content of the first and second substances,
namely, it is
β＝2。
When the tail of the probability density function of the chi-square distribution with the degree of freedom N cannot envelop the tail of the probability density function of the test statistic S (the fact that the tail of the probability density function of the chi-square distribution with the degree of freedom N is not completely over the tail of the probability density function of the test statistic S or the tail of the probability density function of the chi-square distribution with the degree of freedom N is too expanded and the shape of the probability density function of the chi-square distribution with the degree of freedom N is not fit with the shape of the probability density function of the test statistic S), the probability density function of the test statistic S is enveloped with the probability density function of the gamma distribution, and continuously adjusting the values of alpha and beta by adopting a numerical search method, so that the tail part of gamma (alpha, beta) envelops the tail part of the probability density function of the test statistic S, and obtaining the probability density function of gamma distribution after adjustment. And calculating the fraction that the tail probability of the probability density function of the adjusted gamma distribution is equal to the false alarm rate, namely when the tail probability of the probability density function of the adjusted gamma distribution is equal to the false alarm rate, the numerical value of the corresponding abscissa, namely the threshold value when the number of the visible satellites is N, is calculated. Further, the fact that the tail of γ (α, β) envelops the tail of the probability density function of the test statistic S means that the tail of γ (α, β) does not swell excessively while enveloping, and γ (α, β) is more conformal to the probability density function of the test statistic S.
For example, when the number of the visible satellites at different times has three states, namely, 7, 8, and 9, the threshold corresponding to the number of the visible satellites being 7, the threshold corresponding to the number of the visible satellites being 8, and the threshold corresponding to the number of the visible satellites being 9 are obtained through the above steps. The specific state of the number of visible satellites at different times can be determined based on actual historical data.
In a specific embodiment, step S40 includes:
step S41: when the test statistic S 'of at least one reference receiver in the M reference receivers is larger than the threshold value of the test statistic under the number of visible satellites corresponding to the current moment, the reference receiver corresponding to the largest test statistic in the test statistic S' of the at least one reference receiver is removed;
step S42: recalculating the test statistic for the rest reference receivers, and comparing the recalculated test statistic with the threshold value of the test statistic under the number of visible satellites corresponding to the current moment; and if the test statistic of the rest reference receivers is less than or equal to the threshold value of the test statistic under the quantity of the visible satellites corresponding to the current moment, judging that a single receiver fault exists at the current moment.
Specifically, if the test statistic S' of the M reference receivers is less than or equal to the threshold value of the test statistic under the number of visible satellites corresponding to the current time, it indicates that the consistency of the M reference receivers at the current time is good and no single receiver fault occurs; and if at least one test statistic S is larger than the threshold value of the test statistics under the number of the visible satellites corresponding to the current moment, the reference receiver corresponding to the largest test statistic S' is removed, the test statistics of the remaining reference receivers are calculated, and if the test statistics of the remaining reference receivers are smaller than or equal to the threshold value of the test statistics under the number of the visible satellites corresponding to the current moment, the removed reference receiver is a fault receiver, and the single-receiver fault exists at the current moment.
In a specific embodiment, step S40 further includes, before S41: based on the acquired real-time data of the M reference receivers; test statistics for the M reference receivers are calculated. Specifically, the principle of calculating the test statistic is the same as that in step 10, and is not described herein again.
On the other hand, an embodiment of the present application discloses a system for monitoring fault of a single receiver of a ground based augmentation system, please refer to fig. 2, which includes:
the test statistic acquisition module is used for acquiring historical data of the M reference receivers at different moments when the M reference receivers work normally to obtain test statistics S of the M reference receivers at different moments;
the test statistic classification module is used for classifying the test statistics S of the M reference receivers at different moments by combining the number of the visible satellites at different moments to respectively obtain test statistic S sample sequences under the number of the visible satellites;
the threshold value calculation module is used for calculating the threshold value of the test statistic amount under each visible satellite number based on the test statistic amount S sample sequence under each visible satellite number and by combining the false alarm rate;
and the single receiver fault judgment module is used for acquiring real-time data of the M reference receivers, calculating the test statistic S' of the M reference receivers at the current moment, and judging whether a single receiver fault exists at the current moment by combining the threshold value of the test statistic under the quantity of the visible satellites corresponding to the current moment.
Compared with the prior art, the single-receiver fault monitoring system of the foundation enhancement system provided by the embodiment obtains the test statistics of the M reference receivers at different moments based on the historical data of the M reference receivers at different moments when the M reference receivers normally work through the combination of the test statistic acquisition module, the test statistic classification module, the threshold value calculation module and the single-receiver fault judgment module, respectively obtains the test statistics of each visible satellite number according to the number of the visible satellites, respectively obtains the threshold value of the test statistics of each visible satellite number according to the false alarm rate, and further monitors whether a single-receiver fault exists at a certain moment in real time; the single receiver fault monitoring method integrates the additional errors of the reference receiver fault on all satellite channels, amplifies the influence of the fault, simplifies the execution logic judgment process and has higher fault detection speed.
The method embodiment and the system embodiment are realized based on the same principle, the related parts can be referenced mutually, and the same technical effect can be achieved.
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.
Claims (8)
1. A single receiver fault monitoring method of a ground based augmentation system is characterized by comprising the following steps:
acquiring historical data of the M reference receivers at different moments when the M reference receivers work normally to obtain test statistic S of the M reference receivers at different moments, wherein the test statistic S comprises the following steps: acquiring historical data of the M reference receivers at different moments when the reference receivers work normally, and calculating pseudo-range correction value vectors of the M reference receivers at different moments, wherein M is the number of the reference receivers; calculating test statistics S of the M reference receivers at a certain moment based on pseudo-range correction value vectors of the M reference receivers at the certain moment in combination with the normalized weight vector w; calculating the normalized weight vector w according to the following formula:
wherein σgnd＝[σgnd,1,...,σgnd,N]TPseudo-range correction value error standard deviation vectors of the foundation enhancement system and the N visible satellites; sigmagnd,nCalculating the pseudo-range correction value error standard deviation of the foundation enhancement system and the nth visible satellite;
classifying the test statistics S of the M reference receivers at different moments by combining the number of the visible satellites at different moments to respectively obtain test statistics S sample sequences under the number of the visible satellites;
calculating the threshold value of the test statistic under each visible satellite quantity based on the test statistic S sample sequence under each visible satellite quantity and combining the false alarm rate;
the method comprises the steps of obtaining real-time data of M reference receivers, calculating test statistic S' of the M reference receivers at the current moment, and judging whether single receiver faults exist at the current moment or not by combining threshold values of the test statistic under the quantity of visible satellites corresponding to the current moment.
2. The method of claim 1, wherein computing a vector of pseudorange corrections for M reference receivers at different times comprises:
acquiring pseudo-range correction values of the mth reference receiver and each satellite at different moments based on actual measurement data provided by the mth reference receiver at different moments and the actual position of the mth reference receiver;
obtaining a pseudo-range correction value vector of the mth reference receiver at different time based on the pseudo-range correction values of the mth reference receiver at different time and each satellite;
the mth reference receiver is any one of the M reference receivers.
3. The method of claim 1, wherein computing the test statistic S for the M reference receivers at a time based on the pseudorange correction value vectors for the M reference receivers at the time in combination with the normalized weight vector w comprises:
calculating a difference vector of the pseudo-range correction value vector of the mth reference receiver at the moment and an average value vector of the pseudo-range correction value vectors of other reference receivers;
based on the difference vector and in combination with the normalized weight vector w, calculating to obtain a test statistic S of the mth reference receiver at the momentm。
4. A method according to claim 3, characterized in that said calculation yields the test statistic S of the mth reference receiver at that momentmThe method comprises the following steps:
calculating S according to the following formulam：
Pc,m＝[ρc,m,1,...,ρc,m,n,...,ρc,m,N]TA pseudorange correction value vector representing the mth reference receiver at that time; pc,j＝[ρc,j,1,...,ρc,j,n,...,ρc,j,N]TJ ∈ M, j ≠ M, which represents the pseudorange correction value vector of the jth reference receiver except the mth reference receiver at the moment.
5. The method of claim 1, wherein calculating the threshold value of the test statistic for each number of visible satellites based on the sequence of S samples of the test statistic for each number of visible satellites in combination with the false alarm rate comprises:
calculating a probability density function of a test statistic S based on the test statistic S sample sequence when the number of visible satellites is N;
enveloping the probability density function of the test statistic S by using a probability density function of chi-square distribution with the degree of freedom N, wherein N is the number of satellites;
and if the tail part of the probability density function of the chi-square distribution with the degree of freedom N can envelop the tail part of the probability density function of the test statistic S, calculating a threshold value when the number of the visible satellites is N according to the probability density function of the chi-square distribution with the degree of freedom N and the false alarm rate.
6. The method of claim 5, wherein calculating the threshold value of the test statistic for each number of visible satellites based on the sequence of S samples for each number of visible satellites in combination with the false alarm rate further comprises:
if the tail part of the probability density function of chi-square distribution with the degree of freedom N can not envelop the tail part of the probability density function of the test statistic S, enveloping the probability density function of the test statistic S by adopting the probability density function of gamma distribution;
continuously adjusting the values of alpha and beta in the probability density function of gamma distribution until the tail of the probability density function of gamma distribution envelopes the tail of the probability density function of the test statistic S to obtain the adjusted probability density function of gamma distribution;
and calculating a threshold value when the number of the visible satellites is N according to the adjusted probability density function of gamma distribution and the false alarm rate.
7. The method of claim 1, wherein the obtaining real-time data of the M reference receivers, calculating test statistics S' of the M reference receivers, and determining whether a single receiver fault exists at the current time by combining threshold values of the test statistics of the number of visible satellites corresponding to the current time includes:
when the test statistic S 'of at least one reference receiver in the M reference receivers is larger than the threshold value of the test statistic under the number of visible satellites corresponding to the current moment, the reference receiver corresponding to the largest test statistic in the test statistic S' of the at least one reference receiver is removed;
and recalculating the test statistic of the rest reference receivers, comparing the recalculated test statistic with the threshold value of the test statistic of the number of the visible satellites corresponding to the current moment, and if the test statistic of the rest reference receivers is less than or equal to the threshold value of the test statistic of the number of the visible satellites corresponding to the current moment, judging that the single receiver fault exists at the current moment.
8. A single receiver fault monitoring system of a ground based augmentation system based on the monitoring method of claim 1, the system comprising:
the test statistic acquisition module is used for acquiring historical data of the M reference receivers at different moments when the M reference receivers work normally to obtain test statistics S of the M reference receivers at different moments;
the test statistic classification module is used for classifying the test statistics S of the M reference receivers at different moments by combining the number of the visible satellites at different moments to respectively obtain test statistic S sample sequences under the number of the visible satellites;
the threshold value calculation module is used for calculating the threshold value of the test statistic amount under each visible satellite number based on the test statistic amount S sample sequence under each visible satellite number and by combining the false alarm rate;
and the single receiver fault judgment module is used for acquiring real-time data of the M reference receivers, calculating the test statistic S' of the M reference receivers at the current moment, and judging whether a single receiver fault exists at the current moment by combining the threshold value of the test statistic under the quantity of the visible satellites corresponding to the current moment.
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