Laser Anemometry Focal Point Particle Selection
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Solution Overview
Problem
Laser anemometry systems face challenges in accurately measuring air speed around aircraft due to the detection of large particles that may not pass through the focal point and the inability to provide speed information when no particles are detected at the focal point.
Innovation Solution
A laser anemometry system that processes backscattered beams to determine the speed of a virtual particle passing through the focal point, using interferometry and time-frequency analysis to select particles intersecting the beam near the focal point, and computes air speed based on specific thresholds and relationships between duration, slope, and frequency variations in the time-frequency diagram.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the system detects only particles passing through the focal point, then measurement precision is improved, but the system becomes unavailable when no detectable particle passes through the focal point
Solution Approach 1:
The patent segments the particle detection process into two categories: particles passing through the focal point (high precision) and particles passing through other regions (fallback option). By dividing the detection space into focal and non-focal regions, the system can selectively process particles based on their passage location, ensuring continuous operation while maintaining measurement quality when possible.
Solution Approach 2:
The patent applies partial action by accepting measurements from particles that do not pass through the focal point when necessary. While focal point particles provide optimal measurements, the system partially relaxes this requirement to include off-focal particles, ensuring system availability without completely sacrificing measurement precision through appropriate filtering and validation.
2Reliability
If the system accepts particles not passing through the focal point, then system availability is improved, but measurement precision deteriorates due to speed gradient and particle inertia
Solution Approach 1:
The patent applies local quality by implementing different processing and validation criteria for particles based on their passage location. Particles passing through the focal point receive standard processing, while off-focal particles undergo additional validation checks regarding speed gradient effects and particle inertia, allowing the system to adapt its measurement approach to local conditions.
Solution Approach 2:
The patent changes measurement parameters dynamically based on particle passage location. When off-focal particles are detected, the system adjusts its processing to account for varying speed gradients and particle characteristics, modifying acceptance criteria and validation thresholds to maintain reasonable measurement precision under changed conditions.
3Difficulty of detecting and measuring
If large particles are detected due to high backscattering section, then detection capability is improved, but measurement accuracy worsens due to falsification from speed gradient and particle inertia
Solution Approach 1:
The patent converts the high backscattering property of large particles, which causes measurement falsification, into a beneficial detection feature. By explicitly detecting and identifying large particles through their strong backscattering signal, the system can then apply specific filtering and validation rules to exclude or correct their potentially falsifying measurements, transforming a harmful characteristic into a useful detection mechanism.
Solution Approach 2:
The patent performs preliminary identification and classification of particles based on their backscattering characteristics before final measurement processing. Large particles are detected and flagged early in the process, allowing the system to apply pre-defined correction factors or exclusion criteria before the measurements are finalized, preventing measurement falsification at the source.
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
Improves the accuracy of air speed measurement by focusing on particles most representative of the air speed, even in conditions where no particle is detected at the focal point, enhancing the system's performance and reliability.
Implementation Method 1
Laser anemometry systems that use the backscattering of a Gaussian laser beam on the particles surrounding the system to detect the air speed of an aircraft
Implementation Method 2
mixing means 102, respectively associated with a laser source, for mixing said backscattered beam and a reference beam, said reference beam being the duplication of said incident beam, creating an interferometry wave
Implementation Method 3
conversion means 103, respectively associated with a laser source, converting said wave into an electrical signal
Implementation Method 4
third determination means 107 for determining the air speed from all or part of said averages of the frequency... computing a Doppler frequency
Data Source
AI summary
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 means 107 for determining the air speed from all or part of said averages of the frequency, said durations and said slopes.