Thales

Xavier Lacondemine

Jean-Pierre Schlotterbeck

Alain Renard

Bertrand Baillon

Philippe Rondeau

Gregory Baral-Baron

Nicolas Martin

Gilles Fleury

Elisabeth Lahalle

Grégory Baral-Baron

MGrégory Baral-Baron

The invention relates to the measurement of the speed of an aircraft by Doppler laser anemometry, the aircraft being equipped with a LiDAR using coherent detection. According to the invention, the measurement method comprises the following steps:

Method and device for measuring the speed of an aircraft by Doppler

A method for determining the speed vector ({right arrow over (Vd)}), with respect to the surrounding air, of a rotary wing aircraft (HL) equipped with a beam scanning Doppler laser anemometry device for measuring (Step) a set of projections (Vm) of said speed vector ({right arrow over (Vd)}) in at least four non-coplanar directions, comprising the following steps:

Method for determining the speed of a rotocraft relative to the surrounding air

The general field of the invention is that of Doppler lidars intended to measure the speed of a target. The lidar according to the invention comprises: First means for modulating the optical frequency of the transmission signal, said frequency being the sum of a constant frequency and of a variable frequency of determined amplitude modulated by a periodic temporal function; Second means for computing the spectrum of the measured heterodyne signal and for creating two measurement spectra obtained by shifting the spectrum of the heterodyne signal by a positive and negative frequency value, said realignment frequency equal to the difference between the instantaneous frequency of the transmission signal and the frequency of a signal transmitted at a time shifted by the round-trip travel time between the lidar and the target; Third means for comparing the two measurement spectra, the difference in amplitude between the two spectra at the Doppler frequency determining the direction of the speed of the target.

Relative speed measuring doppler LiDAR

An anemometry system comprising a laser source supplying an incident beam that is backscattered by passing through the incident beam mixing means for mixing the backscattered beam and a reference beam, creating an interferometry wave conversion means, converting the interferometry wave into an electrical signal proportional to the power of said wave first determination means, for determining a time-frequency diagram of said electrical signal. The system also comprises second determination means for determining spots of said diagram, each spot being a set of connected points of said diagram, having exceeded a detection threshold computation means for computing an average of the frequency, a duration and a slope characterizing the trend of the frequency as a function of time in the time-frequency diagram, and determination meansfor determining the air speed from all or part of said averages of the frequency, said durations and said slopes.

Laser anemometry system and method

The laser anemometry probe (LAP) system with continuous coherent detection, with single-particle mode, comprises means (AN) for analyzing the measurement signals of the said probe (LAP) and means (MES_T) for measuring the temperature (T). The system comprises, furthermore, means (DET_CG) for determining icing conditions when means (DET_GEL) for detecting the presence of a liquid water drop detect the presence of a liquid water drop, and when the said temperature (T) is below the said third threshold (S).

Laser anemometry probe system and method employing continuous coherent detection, with single-particle mode, capable of detecting ice-forming conditions and of determining the severity of icing

A method for estimating the transverse component Vof the velocity of the air comprises the following steps: emitting a focused laser beam; acquiring an electrical signal resulting from the transit of a particle across the beam at a point of transit; analyzing the signal so as to obtain a spectrogram revealing an elongate mark representative of the transit; estimating the duration of traversal of the laser beam by the particle and the slope of the mark; deducing from the duration and from the slope the distance between the point of traversal of the beam and the focusing point; determining the radius of the beam at the point of transit; deducing the transverse component from the radius and from the duration.

Method for estimating the transverse component of the velocity of the air in a doppler LiDAR measurement

Method of measuring the velocity of an aircraft at a given instant, by laser Doppler anemometry, by performing the steps of acquiring a backscattered signal on at least three oriented line-of-sight axes, and calculating the spectrum of the backscattered signal on each of the line-of-sight axes. Further, acquiring an additional backscattered signal on at least one additional line-of-sight axis (X) not coincident with one of the three first line-of-sight axes (X, X, X), and calculating the spectrum of the backscattered signal on the additional line-of-sight axis (X). Several candidate velocity vectors ({right arrow over (V)}c) and of the projections of the candidate vectors on at least one line-of-sight axis (X, X, X, X) are calculated. The consistency of the candidate vectors ({right arrow over (V)}c) is calculated as a function of their projections and as a function of each spectrum of the corresponding backscattered signal on the respective calculation axis (X, X, X, X). The measured velocity vector ({right arrow over (V)}c) is chosen from among the candidate velocity vectors ({right arrow over (V)}c).

Method of measuring the velocity of an aircraft by laser doppler anemometry

The present invention concerns a single-particle LIDAR anemometry method and system comprising the continuous emission of one or more light beams through a gas containing particles, said beam being focused onto a measurement volume, a step of detecting a signal backscattered by particles passing through said volume, the method being characterized in that it comprises at least the following phases: A notable application of the invention is for the measurement of the airspeed of an aircraft.

Single-particle LIDAR anemometry method and system

The invention relates to an optical measurement device intended for determining a relative velocity vector {right arrow over (v)} of a carrier, such as an aircraft, with respect to a reference medium MILREF. The device includes an optical signal system EMIREC, delivering an optical signal Sinc that follows a direction called the line of sight LDV and is concentrated in a focusing zone ZOF, and means for displacing the focusing zone ZOF in the reference medium MILREF. According to the invention, the means for displacing the focusing zone ZOF act on the orientation of the line of sight LDV, subjecting it to a known movement, with a nonzero speed, a processing unit UTR determines the vector {right arrow over (v)} in at least one 'search' phase based on an identification with an expected waveform of the variation in frequency of an electrical signal as a function of the orientation of the line of sight LDV in order to determine an approximate value of {right arrow over (v)}, followed by a 'tracking' phase based on an iterative validation of values of {right arrow over (v)} close to the approximate value of {right arrow over (v)}.

Laser anemometry with improved eye safety

The invention relates to a device for measuring a Doppler frequency shift, including an optical signal channel delivering a signal light beam illuminating a reference medium; and a reference channel delivering a reference light beam for detecting the Doppler frequency shift. The frequency shift is determined from the difference in frequency between the light signal illuminating the reference medium and the light beam returned by the reference medium. The device includes at least two light radiation sources, preferably lasers, with one light radiating source generating the light beam for the signal channel and the other source generating the light beam for the reference channel.

Optical device for measuring a doppler frequency shift

The invention relates to a Doppler frequency shift measuring device of the optical type comprising an optical signal channel delivering, through a polarization-splitting coupler, through a bidirectional signal port of the coupler, a signal light beam illuminating a reference medium, the coupler receiving, through said bidirectional port, a backscattered light beam returned by the reference medium; a reference channel providing a reference light beam for detection of the Doppler frequency shift, the frequency shift being determined by the frequency shift between the light signal illuminating the reference medium and the light beam returned by the reference medium. The reference light beam is applied to a reference port of the polarization-splitting coupler, said coupler delivering, at a port, a beat signal between the frequency of the reference light beam applied to the port and the frequency of the backscattered light beam applied to the port, possibly containing the Doppler shift.

Low-cost doppler frequency shift measuring device

The invention relates to an optical measurement device designed notably to evaluate the velocity of an aircraft by detection of a Doppler shift. The device for measurement by optical probe comprises at least two light beams of different wavelengths &#x3bb;, denoted as first beam and second beam, the device illuminating a reference medium MILREF () by the first beam and receiving a light echo Sr reflected back by the reference medium, and the device comprising:

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Valence, France

Xavier Lacondemine