Doppler LiDAR Transverse Velocity Estimation Using Single-Beam Signal Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current Doppler LiDAR systems require multiple beam transmission/reception telescopes and distribute laser power inefficiently, making it costly and complex to estimate the true air speed by combining measurements from multiple non-coplanar beams, especially in environments where particle speed is disturbed by the carrier.
Innovation Solution
A method that focuses on analyzing the electrical signal from a single particle's passage through a laser beam to estimate the transverse component of air velocity using spectrogram analysis, determining the duration and slope of the signal to calculate the beam's radius and distance from the focal point, and subsequently deducing the transverse component, thereby reducing the need for multiple beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple non-coplanar beams are used to estimate true air speed, then measurement accuracy is improved, but device complexity and cost increase due to multiple beam transmission/reception telescopes
Solution Approach 1:
The patent segments the velocity measurement task into two independent components: longitudinal velocity measured by Doppler frequency shift and transverse velocity measured by signal duration. This allows using a single beam for both measurements, eliminating the need for multiple telescopes while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces signal duration as an intermediary parameter that indirectly provides transverse velocity information. By measuring how long the particle signal lasts in the focused beam, the system can deduce transverse velocity without requiring additional measurement axes or telescopes.
2Measurement precision
If laser power is distributed along multiple measurement axes, then velocity vector components can be obtained, but detection sensitivity decreases
Solution Approach 1:
The patent segments the velocity measurement into longitudinal and transverse components that can be extracted from a single beam measurement. The longitudinal component comes from Doppler frequency while the transverse component comes from signal duration, allowing concentrated laser power on one axis.
Solution Approach 2:
The patent changes the measurement parameter from spatial distribution (multiple beams) to temporal characterization (signal duration). By analyzing the time duration of the particle signal in a focused beam, the system obtains transverse velocity information without distributing laser power across multiple axes.
3Quantity of substance
If measurements are carried out at different points in a zone where particle speed is disturbed by the carrier, then velocity data can be collected, but determination of speed modulus becomes complex
Solution Approach 1:
The patent uses signal duration as an intermediary that directly provides transverse velocity information at the measurement point. This allows determining the velocity modulus using the Pythagorean theorem with longitudinal and transverse components from the same location, avoiding complex corrections for spatial variations in the disturbed flow field.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the estimation of the transverse component of air velocity using a single beam, improving detection sensitivity and reducing complexity and cost by leveraging time-frequency characteristics of the signal, enabling accurate airspeed modulus calculation.
Implementation Method 1
The Doppler frequency corresponding to the difference between the frequency of the backscattered beam and that of the incident beam is detected by an interferometer so as to characterize the speed of the aircraft relative to the wind
Implementation Method 2
Doppler LiDARs can be used to measure wind speed and direction by backscattering a laser beam on aerosol-like particles carried by the wind
Implementation Method 3
In this regime, the laser beam is strongly focused so that each particle passing through it produces an individually detectable signal
Implementation Method 4
each particle passing through it produces an individually detectable signal
Data Source
Figure 1~3
Figure 2
Figure 4~5
AI summary
The invention relates to a method for estimating the transverse component Vtrans of the air velocity. It comprises the following steps: emitting a focused laser beam; acquiring (200) an electrical signal s(t) resulting from the passage of a particle through the beam at a point of passage; analyzing (201) the signal s(t) so as to obtain a spectrogram showing an elongated spot representative of said passage; estimating (202) the time D of the particle's transit through the laser beam and the slope P of the spot; deducing from the time D and the slope P the distance z0 between the point of passage of the beam and the focal point; determining the radius ω(z0) of the beam at the point of passage; deducing the transverse component Vtrans (203) from the radius ω(z0) and the time D.