Method and integrity verification device location information obtained by at least two satellite geolocation devices

• US 10,094,932 B2
• Filed: 09/25/2015
• Issued: 10/09/2018
• Est. Priority Date: 09/25/2014
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Bonel, Roland, Coatantiec, Jacques, Legoll, Sebastien Francois Philippe
• Primary Examiner(s): Nguyen, Chuong P
• Application Number:
  US14/865,857
• Publication Number:
  US 20160091611A1
• Time in Patent Office: 1,110 Days
• Field of Search: 34235763, 34235723, 34235725
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/42 Determining position

Abstract

The invention relates to a method and a device for verifying the integrity of position vector information obtained by at least two satellite geolocation devices, each of the geolocation devices being able to receive a plurality of wireless signals from a plurality of separate satellites, and to use the received wireless signals to compute a position vector of said geolocation device, including position coordinates computed in a predetermined spatial reference at a given moment in time, each of the geolocation devices being independent of the other geolocation devices, the satellites used being able to be different from one geolocation device to the next. The method includes, for at least one considered pair of geolocation devices made up of a first geolocation device (G_m) and a second geolocation device (G_n), computing (34) a deviation statistic between a first position vector computed by the first geolocation device and a second position vector computed by the second geolocation device, and computing (36) an alarm statistical threshold (S(m,n)) based on the deviation statistic and a first predetermined probability (P_FA). The method makes it possible to raise a malfunction alarm by using the computed alarm statistical threshold. The invention also makes it possible to compute (44), for at least one geolocation device of each pair of geolocation devices, an integrity radius from the alarm statistical threshold and a second predetermined probability (P_ND).

Claims

1. A method for verifying the integrity of position vector information obtained by at least two satellite geolocation devices carried by a moving platform, the position vector information being used for calculating a geolocation position of the moving platform, the geolocation position being used for navigating the moving platform, each of the geolocation devices being able to receive a plurality of radio signals from a plurality of separate satellites, and to use the received radio signals to compute a position vector of said geolocation device, including position coordinates computed in a predetermined spatial reference at a given moment in time, each of the geolocation devices being independent of the other geolocation devices, the satellites used being able to be different from one geolocation device to the next,

the method comprising, for at least one pair of considered geolocation devices made up of a first geolocation device and a second geolocation device, the following steps implemented by a processor of a geolocation computation device:

obtaining, for each of the geolocation devices of said pair of geolocation devices, a set of positioning information,

computing, using the information positioning assemblies respectively associated with the first geolocation device and the second geolocation device, a deviation statistic between a first position vector computed by the first geolocation device and a second position vector computed by the second geolocation device,

computing an alarm statistical threshold based on the deviation statistic and a first predetermined probability,

determining a deviation value between at least part of the components extracted from the first computed position vector and the second computed position vector,

comparing the determined deviation value to the alarm statistical threshold, and

raising a malfunction alarm for one of the first and second geolocation devices when the determined deviation value exceeds the alarm statistical threshold, so as to exclude positioning information from the first or second geolocation device for which the malfunction alarm is raised from computing a geolocation position of the moving platform,

the computation of a deviation statistic including computing a variance matrix representative of the deviation statistic,

and the alarm statistical threshold being such that in the absence of a malfunction on said first and second geolocation devices, the probability of a computed deviation value exceeding said alarm statistical threshold is lower than said first probability.

2. The integrity verification method according to claim 1, wherein the positioning information for each geolocation device includes:

an instantaneous position vector computed by said geolocation device,

an error variance matrix on the computed spatial positions,

a weighted observation matrix associated with satellites used to compute position vectors,

and for each satellite used to compute said position vector, a value representative of the error standard deviation over a distance between said geolocation device and said satellite.

3. The integrity verification method according to claim 2, wherein the positioning information for each geolocation device includes data making it possible to determine, for each satellite, an error standard deviation specific to the geolocation device and an error standard deviation shared by all of the geolocation devices, the error standard deviation over a distance between said geolocation device and said satellite being computed based on said specific error standard deviations and shared error standard deviations.

4. The integrity verification method according to claim 3, wherein said variance matrix representative of a deviation statistic between the first position vector computed by the first geolocation device and the second position vector computed by the second geolocation device is computed using the formula:

P_DIFF(m,n)=P_m+P_n−

P_mH_m,c^TΔ

H_n,cP_n−

P_nH_n,c^TΔ

H_m,cP_m

wherein;

P_m is the error variance matrix on the spatial positions computed for the first geolocation device and P_n is the error variance matrix on the spatial positions computed for the second geolocation device,

H_m,c is the observation matrix of the shared satellites for the first geolocation device and H_n,c is the observation matrix of the shared satellites for the second geolocation device,

and Δ

is a diagonal matrix whose terms are defined by;

5. The integrity verification method according to claim 3, wherein, when said first and second geolocation devices use a same set of satellites, said variance matrix representative of a deviation statistic between the first position vector computed by the first geolocation device and the second position vector computed by the second geolocation device is computed using the formula:

P_DIFF(m,n)=P_mH_m^TD_mH_mP_m+P_nH_n^TD_nH_nP_n

wherein;

P_m is the error variance matrix on the spatial positions computed for the first geolocation device and P_n is the error variance matrix on the spatial positions computed for the second geolocation device,

H_m is the weighted observation matrix for the first geolocation device and H_n is the weighted observation matrix for the second geolocation device,

D_m is a diagonal matrix, associated with the first geolocation device, whose terms are defined by;

6. The integrity verification method according to claim 2, wherein the positioning information further includes, for each geolocation device, a set of identifiers of the satellites used by said geolocation device.

7. The integrity verification method according to claim 6, comprising, for each of said first and second geolocation devices, a step for extracting an observation matrix of the shared satellites from the corresponding weighted observation matrix, as a function of the identifiers of the satellites used both by the first geolocation device and the second geolocation device, said identifiers being obtained from respective identifier assemblies contained in the positioning information.

8. The integrity verification method according to claim 1, wherein the alarm statistical threshold is computed as a function of a Gaussian distribution probability centered on the deviation between position vectors computed with no malfunction of said first and second geolocation devices.

9. The integrity verification method according to claim 1, wherein each of the geolocation devices having an associated true position vector, further comprising a step for computing an integrity radius, for at least one of the geolocation devices of the pair of geolocation devices, called processed geolocation device, for which a probability of malfunction or failure is known, said integrity radius being such that the probability of the deviation, for the chosen components, between the true position vector and the position vector computed by said processed geolocation device being above said radius, is below a second determined probability.

10. The integrity verification method according to claim 9, wherein the computation of an integrity radius includes computing an intermediate radius, depending on the computed alarm statistical threshold and a first distance such that in the absence of malfunction on the other geolocation device of the pair of geolocation devices, the probability of having a deviation, for the selected components, between the true position vector and the position vector computed by said other geolocation device of the pair of geolocation devices, greater than said first distance, is lower than the second probability divided by the failure probability of the processed geolocation device.

11. The integrity verification method according to claim 10, wherein the computation of the integrity radius includes selecting the maximum between said intermediate radius and a second distance, such that when there is no failure on the processed geolocation device, the probability of having a deviation, for the selected components, between the true position vector and the position vector computed by said processed geolocation device, greater than said second distance, is lower than the second probability.

12. A device for verifying the integrity of position vector information obtained by at least two satellite geolocation devices carried by a moving platform, the position vector information being used for calculating a geolocation position of the moving platform, the geolocation position being used for navigating the moving platform, each of the geolocation devices being able to receive a plurality of radio signals from a plurality of separate satellites, and to use the received radio signals to compute a position vector of said geolocation device, including position coordinates computed in a predetermined spatial reference at a given moment in time, each of the geolocation devices being independent of the other geolocation devices, the satellites used being able to be different from one geolocation device to the next,

the verification device comprising, for at least one pair of considered geolocation devices made up of a first geolocation device and a second geolocation device, modules suitable for:

obtaining, for each of the geolocation devices of said pair of geolocation devices, a set of positioning information,

computing, using the information positioning assemblies respectively associated with the first geolocation device and the second geolocation device, a deviation statistic between a first position vector computed by the first geolocation device and a second position vector computed by the second geolocation device,

computing an alarm statistical threshold based on the deviation statistic and a first predetermined probability,

determining a deviation value between at least part of the components extracted from the first computed position vector and the second computed position vector,

comparing the determined deviation value to the alarm statistical threshold, and

raising a malfunction alarm for one of the first and second geolocation devices when the determined deviation value exceeds the alarm statistical threshold, so as to exclude positioning information from the first or second geolocation device for which the malfunction alarm is raised from computing a geolocation position of the moving platform,

the module for computing a deviation statistic being capable of computing a variance matrix representative of the deviation statistic,

the alarm statistical threshold being such that in the absence of a malfunction on said first and second geolocation devices, the probability of a computed deviation value exceeding said alarm statistical threshold is lower than said first probability.