US 12,436,295 B2
Method for locating a navigation unit
Christophe Villien, Grenoble (FR); and Christophe Combettes, Grenoble (FR)
Assigned to Commissariat à l'Energie Atomique et aux Energies Alternatives, Paris (FR)
Filed by Commissariat à l'Energie Atomique et aux Energies Alternatives, Paris (FR)
Filed on Jun. 2, 2023, as Appl. No. 18/328,017.
Claims priority of application No. 22 05306 (FR), filed on Jun. 2, 2022.
Prior Publication US 2024/0183933 A1, Jun. 6, 2024
Int. Cl. G01S 19/22 (2010.01); G01S 19/39 (2010.01)
CPC G01S 19/22 (2013.01) [G01S 19/393 (2019.08)] 7 Claims
OG exemplary drawing
 
1. A method for locating a navigation unit in an environment containing beacons transmitting messages, the method comprising execution of the following steps for each time tk of a temporal sequence of times {t0, . . . ; tk-1, tk; . . . }:
(a) receiving messages transmitted by at least three beacons,
(b) extracting raw measurements of pseudoranges separating the navigation unit from each of the at least three beacons based on times of receipt of the messages as measured by the navigation unit and on a speed of propagation of the messages through space,
(c) estimating an internal position of the navigation unit at the time tk based on the raw measurements extracted for the time tk, on a preceding internal position of the navigation unit estimated at the time tk-1 and on positions of the beacons,
(d) for a plurality of beacons, establishing a measurement bias for the time tk that, when subtracted from the raw measurement extracted based on the time of receipt of the message transmitted by the beacon, allows an error affecting the raw measurement to be decreased, the measurement bias being established based on a difference between:
(1) a computed pseudorange separating the beacon from the navigation unit, the computed pseudorange being computed based on a position of the beacon and on an internal position of the navigation unit estimated for the time tk, and
(2) a measured pseudorange separating the beacon from the navigation unit, the measured pseudorange being computed based on the raw pseudorange measurement extracted for the beacon for the time tk and without taking into account the internal position of the navigation unit,
(e) for each beacon for which a measurement bias was established for the time tk, computing a corrected measurement of the pseudorange at the time tk by adding the measurement bias established for the beacon to a raw measurement of the pseudorange for the beacon extracted at the time tk, and
(f) estimating an external position of the navigation unit at the time tk based on:
(i) positions of the beacons for which a corrected measurement of the pseudorange at the time tk was computed,
(ii) corrected pseudorange measurements computed for the time tk, and
(iii) the preceding external position of the navigation unit estimated for the preceding time tk-1,
wherein steps (b), (c) and (d) are performed without taking into account the external position of the navigation unit.