Search

EP-4740041-A1 - MEASURING WIND SPEED USING ONE OR MORE LIDAR SYSTEMS

EP4740041A1EP 4740041 A1EP4740041 A1EP 4740041A1EP-4740041-A1

Abstract

Disclosed is a method for measuring wind speed using one or more LIDAR systems (1) located on board a carrier (10), which combines two Doppler-effect measurements taken successively while aiming at the same target location (Z), which is transversely offset with respect to a path (T) of the carrier. The method enables two-dimensional evaluation of wind speed at the target location, with an improved evaluation reliability. It is thus possible to obtain evaluations of vertical and horizontal components of the wind speed ahead of an aeroplane.

Inventors

  • MICHEL, David Tomline
  • BOULANT, Thibault
  • Valla, Matthieu
  • MUSSO, Christian
  • LEFEBVRE, SIDONIE

Assignees

  • Office National d'Etudes et de Recherches Aérospatiales

Dates

Publication Date
20260513
Application Date
20240704

Claims (8)

  1. [Claim 1] Method for measuring a wind speed using at least one LIDAR system (1) which is on board a carrier (10), the measurement relating to at least two components of the wind speed such that said wind speed exists at a location external to the carrier, called the target location (Z), the method comprising the following two steps: /1/ at a first instant (ti) during a movement of the carrier (10), performing a first measurement by directing a line of sight of the LIDAR system (1) towards the target location (Z), said line of sight then being parallel to a first axis (Ai), and by deducing from said first measurement, by means of a Doppler effect characterization, an estimate of a projection (Vci) on the first axis, of the wind speed which exists at the target location; then 121 at a second time (t 2 ) during the movement of the carrier (10), performing a second measurement of the wind speed using the same LIDAR system (1 ) as in step /1 / or another LIDAR system which is also on board the carrier, wherein, for the second measurement of the wind speed which is performed in step 121, the line of sight of the LIDAR system (1 ) used in said step 12/ is again directed towards the target location (Z), but being parallel to a second axis (A2) which is angularly offset from the first axis (Ai), said second measurement being used to deduce therefrom, by means of the Doppler effect characterization, an estimate of a projection (Vc2) on the second axis, of the wind speed which exists at the target location, and the method further comprising the following additional step: /3/ deducing, from the estimates of the projections (Vci, Vc2) of the wind speed on the first and second axes, as obtained in steps /1/ and 121, a two-dimensional estimate (V12) of said wind speed which exists at the target location (Z), said two-dimensional estimate being parallel to a plane which contains the first and second axes (Ai, A 2 ), in which method, when the movement of the carrier (10) is rectilinear or locally rectilinear, the target location (Z) is offset relative to a trajectory (T) of the carrier in accordance with a transverse offset value (d), and a duration between the first and second instants (ti , t 2 ) is selected as a function of the transverse offset value and of a moving speed of the carrier, the method being characterized in that steps /1/ to 131 are performed for the target location (Z) and repeated for another target location (Z') which is symmetrical to said target location with respect to the trajectory (T) of the carrier (10), so as to separately obtain two two-dimensional estimates (V12, V12') of wind speed, one for said target location and one for said other target location, then a two-dimensional estimate (VM) attributed to a point (M) of the trajectory (T) of the carrier (10) is calculated as an average of the two-dimensional estimates (V12, V12') relating respectively to the target location (Z) and to the other target location (Z'), the point being at an intersection of the trajectory of the carrier with a straight segment which connects said target location and said other target location.
  2. [Claim 2] Method according to claim 1, according to which the first and second axes (Ai, A2) form between them an angle which is greater than 10°, preferably less than 45°.
  3. [Claim 3] A method according to claim 1 or 2, wherein the carrier (10) is an aircraft, and the movement of the carrier is movement of the aircraft in flight.
  4. [Claim 4] Method according to one of the preceding claims, according to which steps /1/ to 131 are executed separately for two target locations (Zv, ZH) situated in two respective measurement planes (PV, PH) which each contain the trajectory (T) of the carrier (10) but are angularly offset from each other around said trajectory, so as to provide two-dimensional estimates relating one-to-one to each target location.
  5. [Claim 5] Method according to claim 4, according to which steps /1/ to 131 are carried out separately for the target location (Z) and for the other target location (Z') which is symmetrical to said target location with respect to the trajectory (T) of the carrier (10), and separately also for each of the two measurement planes (PV, PH), and according to which a three-dimensional estimate of the wind speed which exists at the point (M) of the trajectory (T) of the carrier (10) is deduced from the two-dimensional estimates obtained respectively for one and the other of the two measurement planes.
  6. [Claim 6] Method according to one of the preceding claims, according to which steps /1/ to 131 are repeated for a series of target locations which are offset parallel to the trajectory (T) of the carrier (10).
  7. [Claim 7] LIDAR equipment, comprising at least one LIDAR system (1) adapted to measure a wind speed, and further comprising a calculation unit configured to provide for each measurement, from a Doppler effect characterization, an estimate of a projection (Vci, Vc2) on a line of sight of the LIDAR system, of the wind speed which exists at a target location (Z) located on the line of sight, the calculation unit being further configured to deduce from the projection estimates (Vci, Vc2) of the wind speed provided by two measurements for which the respective lines of sight intersect at the target location (Z), the projection estimates relating to said target location, a two-dimensional estimate (V12) of the wind speed which exists at said target location, the calculation unit being further configured to execute a method according to one of the preceding claims.
  8. [Claim 8] Aircraft (10) comprising LIDAR equipment, said LIDAR equipment being according to claim 7 and carried on board the aircraft, preferably installed on a front-rear median axis of said aircraft.

Description

Description Title: MEASUREMENT OF WIND SPEED USING ONE OR MORE LIDAR SYSTEM(S) Technical field [0001] The present description relates to a method for measuring a wind speed using one or more LIDAR system(s). It also relates to equipment which comprises the LIDAR system(s) used as well as an aircraft on board which this equipment is carried. Previous technique [0002] FR 2 942 043 describes a system and method for detecting and determining atmospheric anomalies remotely. [0003] FR 2 938 075 describes a device and method for detecting and measuring wind for aircraft. [0004] Remotely measuring wind speed, and consequently characterizing atmospheric turbulence that is likely to be present in specific areas, is useful for many applications. Such measurements are particularly sought after in the field of air transport, in particular to detect the presence of air flows that have speed components perpendicular to a nominal direction of movement of an aircraft. Indeed, the presence of a wind speed component that is vertical and/or a horizontal wind speed component that is transverse to a front-rear direction of an aircraft can cause risks during the cruise flight phase or when the aircraft is landing. Remote measurement of such wind speed components is also sought to reduce the load that exists on the wings of an aircraft. Still other applications of interest in such remote wind speed measurements include meteorological applications, the control of stratospheric platform stations such as HAPS for "High-Altitude Platform Station" in English, the control of drones flying in areas of atmospheric turbulence, the monitoring of airflow around a moving vehicle such as a truck, etc. [0005] It is known to use LIDAR systems, for "Light-Detection And Ranging" in English or systems for detecting and measuring distances by light, to carry out air velocity measurements. Such measurements are based on Mie backscattering which is produced by particles present in suspension in the air, such as aerosols, dust or ice grains, and/or on Rayleigh backscattering which is produced by molecules in the composition of the air. However, the velocity measurements which are carried out using a LIDAR system are limited to measurements of the velocity component which is parallel to the line of sight of the LIDAR system. [0006] Now for many applications, the velocity components whose measurements are most useful are those which are perpendicular to a separation direction between the instantaneous position of the LIDAR system and the place in the atmosphere concerned by the measurement. Thus, the lateral and vertical components of wind speed which exist at a distance in front of the nose of an aircraft in flight are particularly sought after. A first method for this could consist in arranging several LIDAR systems on board the aircraft, which are offset relative to the front-rear median axis of the aircraft and whose lines of sight are directed obliquely towards an area in front of the nose of the aircraft. But such an installation of several LIDAR systems on board an aircraft outside its front-rear median axis is very difficult, if not impossible, due to the lack of locations available for such a multiple installation. A second method, as described for example in the article entitled "Gust load alleviation for a long-range aircraft with and without anticipation", by N. Fezans et al., CEAS Aeronautical Journal (2019), 10: 1033-1057, Springer, consists of installing a single LIDAR system in the nose of the aircraft, directing its line of sight obliquely to the front-rear median axis of the aircraft according to several azimuth and elevation values, and performing several measurements which are thus distributed angularly around this axis. A velocity component value perpendicular to the front-rear median axis of the aircraft is then deduced from these multiple measurements. But a significant error can affect the result which is thus obtained when the air velocity field is not uniform, because the multiple measurements which are used are relative to different locations, and therefore to wind speeds which are a priori different. Finally, a third method consists of carrying out successive measurements along a constant line of sight direction, oblique to the axis median front-rear axis of the aircraft, while the aircraft is moving in flight, to group together several such measurements which are therefore carried out along different lines of sight but which concern locations located in a plane which is fixed in the terrestrial reference frame and perpendicular to the median front-rear axis of the aircraft, then to extrapolate to the point of intersection between this axis and the plane of the reconstructed values of the perpendicular component of airspeed. But this third method does not seem to provide reliable results either, in particular because it also uses measurements which are relative to different locations in space. Technical problem [0007] From t