Method and device for detecting and excluding satellite malfunctions in a hybrid INS/GNSS system

Patent metadata

Field	Value
Publication number	US-9285482-B2
Application number	US-201013257939-A
Country	US
Kind code	B2
Filing date	Mar 24, 2010
Priority date	Mar 24, 2009
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

A method for monitoring the integrity of position information outputted by a hybridization device that includes a bank ( 3 ) of Kalman filters, each filter developing a hybrid navigation solution from inertial measurements calculated by a virtual platform ( 2 ) and from raw measurements of signals transmitted by a satellite constellation which are outputted by a global navigation satellite system (GNSS). The method includes, for each satellite of the constellation of calculating a cross-innovation of the satellite that reflects the deviation between an observation, corresponding to a raw measurement from the satellite, and an a posteriori estimation of said observation that is developed through a Kalman filter and does not use the raw measurement from the satellite; carrying out a statistical test of the cross-innovation to ascertain whether or not the satellite is malfunctioning.

First claim

The invention claimed is:

1. A process for monitoring the integrity of position information delivered by a data fusion device comprising a bank ( 3 ) of Kalman filters including:
a main Kalman filter generating a principal hybrid navigation solution based on inertial measurements calculated by a virtual platform ( 2 ) and raw measurements of signals emitted by all the satellites of a satellite positioning system (GNSS),
for each satellite, a secondary Kalman filter generating a secondary hybrid navigation solution based on inertial measurements calculated by a virtual platform ( 2 ) and raw measurements of signals emitted by all the satellites of the satellite positioning system except for said satellite,
the method comprising for each satellite in the constellation:
calculating (S 1 ) a cross-innovation of the satellite which is representative of the distance between:
an observation corresponding to a raw measurement issuing from said satellite, and
an a posteriori estimate of said observation generated by a Kalman generating a secondary hybrid navigation solution based on inertial measurements calculated by a virtual platform ( 2 ) and raw measurements of signals emitted by all the satellites of the satellite positioning system except for said satellite;

performing (S 2 ) a statistical test comprising comparing the cross-innovation of said satellite to a threshold and declaring a satellite to be faulty when its cross-innovation exceeds a threshold.

2. The process according to claim 1 , wherein the threshold corresponds to (H·P i ·H T +R i )*α, where H represents the observation matrix of the Kalman filter, P i the a posteriori estimation matrix of the covariance of the error, R i the covariance matrix of the measurement noise, and a α coefficient reflecting a probability of a false detection of a satellite failure.

3. The process according to claim 1 , wherein the cross-innovation of a satellite corresponds to the difference between a pseudo-distance to said satellite delivered by the satellite positioning system and an a posteriori estimate of that pseudo-distance supplied by the secondary Kalman filter based on the observations of all the satellites of the satellite positioning system except for said satellite.

4. The process according to claim 1 , also comprising:
invalidating a satellite declared to be faulty so that the raw measurements from said faulty satellite are no longer used by the filters in the bank,
rejecting the invalidated satellite if, on expiration of a predetermined period following invalidation, the statistical test of the cross-innovation still concludes that said satellite is faulty and no other cross-innovation test has declared the failure of another satellite.

5. The process according to claim 4 wherein, in the event of declaration of failure of another satellite during the predetermined period, the formerly invalidated satellite is validated so that these raw data are again used by the filters in the bank, and the new faulty satellite is invalidated.

6. The process according to claim 4 , wherein in the event of a declaration of failure of a satellite, a partial reinitialization of the filters of the bank is performed using the satellite declared to be faulty by reinitializing the states connected with the measurements received from the satellite positioning system and the states connected with the other sensors used, and by desensitizing the states affected by the breakdown by adding state noise.

7. The process according to claim 5 , wherein the main Kalman filter and the secondary Kalman filters further use measurement issued from other sensors, wherein in the event of a declaration of a failure of a satellite, a partial reinitialization of the filters of the bank is performed using the satellite declared to be faulty by reinitializing states connected with the measurements received from the satellite positioning system, and sates connected with the other sensors and by desensitizing the states affected by the breakdown by adding state noise.

8. The process according to claim 1 also implementing, for each filter in the bank, a statistical test of the a priori innovation of each of the satellites used by the filter.

9. The process according to claim 8 wherein, in the case where several satellites are declared to be faulty as a result of the statistical test of their cross-innovation, the method further comprises:
determining the Kalman filter using the greater number of satellites having a prior innovations below a threshold,
invalidating the satellite not used by the previously determined Kalman filter,
so that the raw measurement of said invalidated satellite is no longer used by the filters in the bank.

10. The process according to claim 9 , wherein, in the case where several satellites are declared to be faulty as a result of the statistical test of their cross-innovation and where several secondary Kalman filters are using the same greatest number of satellites having a priori innovation below a threshold, the satellite having the greatest absolute value of the ratio of the cross-innovation to its covariance is invalidated so that the raw measurement of said invalid satellite is no longer used by the filters in the bank.

11. A data fusion device ( 1 ) comprising a bank ( 3 ) of Kalman filters including:
a main Kalman filter generating a principal hybrid navigation solution based on intertial measurements calculated by a virtual platform ( 2 ) and raw measurements of signals emitted by all the satellites of a satellite positioning system (GNSS),
for each satellite, a secondary Kalman filter generating a secondary hybrid navigation solution based on inertial measurements calculated by a virtual platform ( 2 ) and raw measurements of signals emitted by all the satellites of the satellite positioning system except for said satellite,
and a satellite failure detection and rejection module configured so as to implement a process consisting in, for each satellite in the constellation:
calculating a cross-innovation of the satellite representative of the distance between:
an observation corresponding to a raw measurement issuing from said satellite, and
an a posteriori estimate of said observation generated by the secondary Kalman filter generating a secondary hybrid navigation solution based on inertial measurements calculated by a virtual platform ( 2 ) and raw measurements of signals emitted by all the satellites of the satellite positioning system except for said satellite,

performing a statistical test comparing the cross-innovation of said satellite to a threshold, and declaring a satellite to be faulty when its cross-innovation exceeds a threshold.

Assignees

• Vourc H Sébastien
• Mauger Victor
• Sagem Defense Securite

Inventors

• Vourc H Sébastien
• Mauger Victor

Classifications

• G01S19/20

  Integrity monitoring, fault detection or fault isolation of space segment · CPC title

• G01S19/47 Primary

  the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial · CPC title