Hybrid system and device for calculating a position and for monitoring its integrity
AssigneeThales
InventorJacques Coatantiec
Life of this patent
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Abstract
Hybrid system (1) comprising an elementary hybrid system (2) comprising an extended processing module CALC (100) determining a first protection radius of the hybrid system RHG1, associated with a position quantity G, using a first extended variance/covariance matrix MHYPE1 as a function of a predetermined first false alarm probability PFA1, of a predetermined non-integrity level PNI and of a predetermined first probability PP1 of occurrence of an undetected hardware failure of a satellite positioning receiver.
Claims13
Hybrid system (1) comprising an elementary hybrid system (2) comprising:
- a primary module (10) for delivering primary elementary raw measurements MBi1 each comprising positioning measurements and measurements of noise affecting the said positioning measurements,
- an elementary module (20) for delivering inertial measurements MI comprising increments of angles and of speed,
- a hybridization unit (5) receiving the inertial measurements MI and when they are available the primary raw measurements MBi1, and producing a first elementary hybrid solution PPVI1 comprising position measurements and error parameters for the elementary module (20) together with a primary variance/covariance matrix MHYP1,
- characterized in that the said hybrid system also comprises:
- a secondary module (80) for delivering secondary elementary raw measurements MBj2,
- a first extended Kalman filter KE1 (90) receiving the first elementary hybrid solution PPVI1, the primary variance/covariance matrix MHYP1 and, when they are available, the primary and secondary elementary raw measurements and MBj2 coming from satellites common to the primary module and to the secondary module, the said extended filter KE1 having a first extended vector of state VEE1 comprising a part known as hybrid difference ΔX, representing the difference between the first elementary hybrid solution PPVI1 and a second elementary hybrid solution PPVI2 associated with the inertial measurements MI and, when they are available, with the secondary elementary raw measurements MBj2, the said first extended vector of state VEE1 also comprising an error part of the elementary hybrid system X1 affecting the first elementary hybrid solution PPVI1, the said extended Kalman filter delivering a first extended variance/covariance matrix MHYPE1 for the error of a first estimation EVEE1 of the first vector of state VEE1,
- an extended processing module CALC (100) receiving the first extended variance/covariance matrix MHYPE1, the said extended processing module CALC (100) determining a first protection radius for the hybrid system RHG1, associated with a position quantity G, using the first extended variance/covariance matrix MHYPE1 as a function of a first predetermined false alarm probability PFA1, of a predetermined non-integrity level PNI and of a first predetermined probability PP1 of occurrence of an undetected hardware failure of a satellite positioning receiver.
Hybrid system (1) according to the preceding claim, characterized in that the first protection radius of the hybrid system RHG1 associated with a position quantity G is calculated based on a first detection threshold SEΔG1 associated with the hybrid difference ΔX relating to the quantity G, the said first threshold being obtained based on a part of the first extended variance/covariance matrix MHYPE1 associated with the hybrid difference ΔX relating to the said position quantity G, for the first predetermined false alarm probability PFA1, the said first protection radius of the hybrid system RHG1 also depending on a part of the first extended variance/covariance matrix MHYPE associated with the error part of the elementary hybrid system X1 relating to the position quantity G for a first level of risk PND1 chosen so as to be less than or equal to the ratio between the non-integrity level PNI and the probability PP1 of occurrence of an undetected hardware failure of a satellite positioning receiver.
Hybrid system (1) according to any one of the preceding claims, characterized in that:
- the primary module (10), respectively the secondary module (80), is a unit for modelling primary raw measurements, respectively secondary raw measurements, delivered by a primary, respectively secondary, satellite positioning receiver operating using constellations of tracked visible satellites,
- the elementary module (20) for delivering inertial measurements MI is a unit for modelling inertial measurements delivered by an inertial navigation system.
Hybrid system (1) according to the preceding claim, characterized in that when none of the components of the first estimation EVEE1 of the first extended vector of state VEE1 relating to the difference ΔX obtained for the position quantity G is greater than the first detection threshold SEΔG1, the non-integrity level PNI is equal to a normal non-integrity level PNIN.
Device (300) comprising a number M greater than 1 of hybrid systems Sik(1k) according to any one of the preceding claims, each supplying an elementary protection radius REGk associated with a position quantity G, a hybrid protection radius RHGk associated with the said position quantity G together with a variance/covariance matrix of the elementary solution MHYP1k associated with the error made on a first elementary hybrid solution PPVI1k, the said device (300) also comprising a consolidation module CONS (200) determining a global hybrid solution SGLOB, the said consolidation module CONS (200) determining an inertial protection radius RIMUG, which is the lowest value taken from amongst the individual inertial protection radii RIMUGk calculated for each inertial navigation system CIk, the first elementary hybrid solution PPVI1k of which is different from the global solution SGLOB, each individual inertial protection radius RIMUGk depending on:
- the statistics SGk for the difference between the global solution and the first elementary solution PPVI1k, for the quantity,
- the first variance/covariance matrix for the elementary solution MHYP1k,
- a second acceptable false alarm frequency PFA2 and on a second level of risk PND2 chosen so as to be less than or equal to the ratio between the non-integrity level PNI and a determined probability PP2 of occurrence of a failure in an inertial navigation system.
Device (300) according to the preceding claim, characterized in that
- the statistics SGk for the difference between the global solution and the first elementary solution PPVI1k, for the quantity G, is equal to the sum of the errors in the variance-covariance matrices of each of the first elementary hybrid solutions.
Dependencies are inferred from the claim text.