Optical Air Data Sensor Autonomous Doppler LIDAR
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Solution Overview
Problem
Current airspeed measurement technologies, such as Pitot tubes and ultrasonic sensors, face challenges in accuracy at low speeds and are affected by the aircraft's fuselage, requiring extensive calibration and being unsuitable for low-speed aircraft, while Doppler LIDARs need external reference velocities for airspeed measurement.
Innovation Solution
An optical air data sensor using a Doppler LIDAR system that autonomously measures airspeed by sweeping the frequency offset within the Doppler shift measurement range, allowing for true airspeed determination without external reference, and calculates angle of attack and sideslip angles through laser beam scanning, with turbulence measurement based on airflow vector differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Pitot tube is used for airspeed measurement, then the measurement is reliable at high speeds, but the measurement error increases significantly at low speeds and becomes impossible below 30 m/s
Solution Approach 1:
The patent replaces the mechanical Pitot tube system with an optical Doppler LIDAR system that uses laser light scattering and Doppler frequency shift measurement to determine airspeed. This substitution eliminates the mechanical constraints that limited the Pitot tube's low-speed performance and extends the measurement capability across the full airspeed range including low speeds.
2Length of stationary object
If a Doppler LIDAR is used with high output to measure airflow at 10 km distance for turbulence avoidance, then the measurement distance is sufficient, but the device complexity and energy consumption increase
Solution Approach 1:
The patent applies partial action by using a comparatively low laser output that is sufficient for the actual required measurement distance of several tens of meters for air data sensing, rather than the excessive 10 km distance needed for turbulence avoidance. This reduces device complexity and energy consumption while maintaining adequate measurement capability for the specific application.
3Measurement precision
If a Doppler LIDAR measures wind velocity at a distance of several tens of meters, then the aircraft fuselage does not affect the flow field, but the system requires external reference velocity input and cannot autonomously determine absolute airspeed
Solution Approach 1:
The patent implements self-service by enabling the Doppler LIDAR system to autonomously determine absolute airspeed through frequency sweeping of the laser beam. The system automatically performs frequency offset adjustments and measurements without requiring external reference velocity input, making the measurement process self-contained and autonomous.
4Device complexity
If sensors are directly mounted on the fuselage as Pitot tubes, then the device complexity is reduced, but position errors occur due to fuselage interference with the flow field
Solution Approach 1:
The patent extracts the measurement function from the fuselage-mounted sensor approach by using a Doppler LIDAR that measures airflow at a distance of several tens of meters in front of the aircraft. This extraction eliminates the fuselage interference problem that causes position errors in conventional mounted sensors, while maintaining measurement simplicity.
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
Enables accurate airspeed measurement across a wide range, including low speeds, without position errors, and reduces the need for extensive calibration, making it suitable for low-speed aircraft and as a backup for Pitot tubes, while also measuring turbulence effectively.
Implementation Method 1
measuring an airspeed and a wind velocity of airflow in a distant region on the basis of a Doppler shift amount between the transmission light and the reception light
Implementation Method 2
an emitted light is scattered by fine aerosol floating in the atmosphere, the scattered light is received
Data Source
AI summary
The object of the present invention is to provide an air data sensor that does not require an external input of a reference velocity as a Doppler LIDAR, has a function of autonomously determining the absolute airspeed, and has no position error. The optical air data sensor in accordance with the present invention is an optical air data sensor, mounted on an aircraft, for emitting a laser light as a transmission light into atmosphere, and then receiving a laser scattered light produced by scattering of the laser light by aerosol present in the atmosphere as a reception light, thereby to measure an airspeed and a wind velocity of airflow in a distant region on the basis of a Doppler shift amount between the transmission light and the reception light, wherein a true airspeed is autonomously measured, without setting a reference velocity, by successively sweeping a frequency offset corresponding to a reference velocity for providing an offset to a measurement frequency, and performing this sweeping within a frequency range in which the Doppler shift amount is measured.