Single-Particle Anemometry Signal Filtering for Airspeed Precision
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Solution Overview
Problem
Single-particle LIDAR anemometry struggles to accurately measure airspeed of an aircraft in heterogeneous media due to interference from particles moving at different speeds, leading to incoherent speed measurements, especially near the aircraft where aerodynamic disturbances create velocity gradients.
Innovation Solution
A method that focuses a laser beam on a small volume of gas, filters the backscattered signal using band-pass filters and intensity/threshold criteria to distinguish pulses based on duration, frequency, and modulation, excluding signals from particles moving differently than the gas, thereby improving measurement accuracy by rejecting signals from large particles and enhancing selectivity along the optical axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If single-particle LIDAR anemometry is used to measure airspeed, then power consumption is reduced and particle separation is improved, but measurement precision deteriorates in heterogeneous media due to incoherent signals from particles moving at different speeds
Solution Approach 1:
The patent extracts and removes incoherent signals from particles moving at different speeds by implementing signal filtering based on velocity coherence criteria. The system identifies and eliminates signals that do not match the expected velocity profile of the gas flow, thereby purifying the measurement data while maintaining the low power consumption advantage of single-particle anemometry
Solution Approach 2:
The patent changes the measurement approach by shifting from direct particle velocity measurement to gas velocity inference. By measuring the velocity of many particles and statistically determining the predominant velocity that represents gas motion, the system transforms the measurement parameter from individual particle speed to collective gas flow speed, improving precision in heterogeneous media
2Manufacturing precision
If the laser focusing volume is positioned close to the aircraft to observe particles separately, then particle resolution is improved, but measurement precision deteriorates due to aerodynamic disturbances creating velocity gradients
Solution Approach 1:
The patent implements feedback by continuously monitoring the velocity of detected particles and using this information to adjust the measurement process. By analyzing the velocity distribution of multiple particles and identifying the predominant velocity, the system adapts to local flow conditions and compensates for velocity gradients caused by aerodynamic disturbances, maintaining measurement precision despite the challenging near-field environment
3Reliability
If high transmission power is used in multi-particle anemometry to obtain a permanent backscattered signal, then signal stability is improved, but safety risks increase and material resources are consumed
Solution Approach 1:
The patent adopts a strategy of using low-power, short-duration laser pulses instead of high-power continuous illumination. By emitting brief pulses and detecting backscattered light from individual particles during these pulses, the system achieves sufficient signal stability without requiring high transmission power, thereby eliminating safety risks associated with high-energy lasers and reducing material resource consumption
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 enhances the precision of airspeed measurement by filtering out noise and incoherent signals, allowing for accurate estimation of airspeed even in heterogeneous environments, achieving accuracy of less than 0.5 m/s.
Implementation Method 1
the measurement of the frequency shift between a reference optical signal and the backscattered signal makes it possible to determine the relative speed of the carrier to the aerosols therefore also in the air. The frequency shift thus measured is called the Doppler frequency
Implementation Method 2
An optical beam is emitted by a laser and is backscattered by aerosols in suspension in the air
Data Source
Figure 1~2b
Figure 3a~3c
Figure 3d~3e
AI summary
The method involves determining, at a duration, frequencies of each of pulses comprising a backscattered signal, and distinguishing the pulses on a criterion of duration and/or intensity and/or frequency modulation. A detection chain is arranged for detection of digital signals (460). Displacement speed of a light beam relative to gas is estimated from the determined frequencies at the duration by excluding frequencies corresponding to the distinguished pulses, where the beam is focused at a proximal distance from a fuselage of an aircraft. An independent claim is also included for a single-particle anemometry system including a detection chain for detection of signals.