Method for determining the position of a mobile body at a given instant and for monitoring the integrity of the position of said mobile body

• US 8,566,033 B2
• Filed: 05/28/2010
• Issued: 10/22/2013
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Clemenceau, Pierre-Jrme, Coatantiec, Jacques
• Primary Examiner(s): CAMBY, RICHARD M
• Application Number:
  US13/381,357
• Publication Number:
  US 20130030775A1
• Time in Patent Office: 1,243 Days
• Field of Search: 701/3, 701/7, 701/10, 701/11, 701/14, 701/468, 701/469, 701/471, 701/472, 701/500, 701/501, 701/502, 701/507, 701/505
• US Class Current: 701/469
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial

Abstract

A method for determining the position of a mobile body at a given instant and for monitoring the integrity of the position of said mobile body includes a step of determining a sustained position at the given instant by adding the integral of the hybrid speed between the preceding instant and the given instant to the position of the mobile body at the preceding instant; a step of determining the sustained protection radius associated with the sustained position by adding the integral of the hybrid speed protection radius between the preceding instant and the given instant to the position protection radius of the preceding instant; a step of determining a better position at the given instant, the better position being: when information from the first positioning device is available, the position associated with a better protection radius, the better protection radius being selected by comparing the intermediate protection radius with the sustained protection radius according to a predetermined selection criterion; and, when information from the intermediate positioning device is unavailable, the sustained position.

Claims

1. A method for determining the position (P(t)) of a mobile body at a given instant (t) and for monitoring the integrity of the position of said mobile body, comprising:

storing the position of said mobile body (P(t−

Δ

t)) at a previous instant (t−

Δ

t) and an associated protection radius (RP(t−

Δ

t)),

acquiring when it is available, intermediate position information (PPOS) arising from an intermediate positioning device DPOS and an intermediate protection radius (RPPOSS) associated with the intermediate position (PPOS) arising from said intermediate positioning device DPOS,

acquiring information about hybrid speed (VHY) and a hybrid speed protection radius (RPVHY) associated with the hybrid speed (VHY) determined by an INS/GNSS hybridization unit UI,

determining a sustained position (PI(t)) at the given instant (t) by adding, to the position of the mobile body at the previous instant (P(t−

Δ

t)), the integral of the hybrid speed (VHY) between the previous instant (t−

Δ

t) and the given instant (t),

determining the sustained protection radius (RPI(t)) associated with the sustained position by adding to the position protection radius (RP(t−

Δ

t)) of the previous instant (t−

Δ

t), the integral of the hybrid speed protection radius (RPVHY) between the previous instant (t−

Δ

t) and the given instant (t),

determining a best position at the given instant (t), the best position being;

when the information arising from the intermediate positioning device is available, the position associated with a best protection radius, the best protection radius being chosen by comparing, as a function of a predetermined selection criterion, the intermediate protection radius (RPPOS) with the sustained protection radius (RPI) at the given instant,

when the information arising from the intermediate positioning device is unavailable, the sustained position at the given instant,

the position (P(t)) of the mobile body being the best position.

2. The method for determining the position (P(t)) of a mobile body at a given instant (t) and for monitoring the integrity of said position as claimed in claim 1, wherein the hybridization unit UI implements a resetting method based on the independence of the faults affecting the various satellites.

3. The method for determining the position (P(t)) of a mobile body at a given instant (t) and for monitoring the integrity of said position as claimed in claim 1, wherein the selection criterion consists in identifying as being the best protection radius, the smallest protection radius from among the intermediate protection radius (RPPOS) associated with the intermediate position (PPOS) and the sustained protection radius associated with the sustained position.

4. The method for determining the position (P(t)) of a mobile body at a given instant (t) and for monitoring the integrity of said position as claimed in claim 1, wherein the step of acquiring the hybrid speed protection radius is preceded by a step of determining, via the hybridization unit UI, a hybrid speed horizontal (and/or vertical) protection radius of hybrid speed, comprising the following steps:

determination of a hybrid speed auxiliary horizontal (and/or vertical) protection radius, under a hypothesis termed H1, that one of the raw measurements, MBi is erroneous,

determination of a hybrid speed auxiliary horizontal (and/or vertical) protection radius under a hypothesis termed H0, that none of the raw measurements, MBi is erroneous,

determination of the hybrid speed horizontal or vertical protection radius as a maximum of the hybrid speed auxiliary horizontal or vertical protection radii, the determination of the auxiliary hybrid speed horizontal or vertical protection radii being based on a determination of a radius of a circle enveloping a confidence ellipse in a horizontal or vertical plane, and in that the confidence ellipse is determined on the basis of a variance/covariance matrix and of a sought-after probability value.

5. A global system intended to be installed aboard a mobile body, comprising:

sub-system S able to implement the method as claimed in claim 1,

an inertial measurement unit UMI delivering inertial information (INFI),

a GNSS satellite-based positioning receiver receiving signals from a constellation of tracked visible satellites and delivering raw data (MBi),

a hybridization unit UI delivering information about hybrid speed (VHY) and about hybrid speed protection radius on the basis of inertial information (INFI) delivered by the inertial measurement unit UMI and about raw information (MBi) delivered by the GNSS satellite-based positioning receiver;

an intermediate positioning device DPOS delivering information hybrid intermediate positions (PPOS) and about associated intermediate protection radii (RPPOS).

6. The global system intended to be installed aboard a mobile body as claimed in claim 1, wherein the intermediate positioning device is an augmented positioning device.

7. The global system as claimed in claim 1, wherein the mobile body is an aircraft.