Helicopter Airspeed Blending for Accurate Low-Speed Control
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Solution Overview
Problem
Existing airspeed measurement systems for rotary-wing aircraft, such as pitot probes, are not accurate at low airspeeds due to factors like rotor downwash, high angles of attack, and poor signal-to-noise ratio in pressure measurements.
Innovation Solution
A method and system that blend airspeed data from airspeed probes with aircraft state information, using fade values to determine a blended airspeed that is more accurate at low airspeeds by weighting the measured and estimated airspeeds based on their confidence levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pitot probes are used to measure airspeed, then airspeed measurement is achieved at normal speeds, but measurement precision deteriorates at low airspeeds due to rotor downwash, high angles of attack, and poor signal-to-noise ratio
Solution Approach 1:
The patent combines multiple airspeed estimation methods (pitot probe measurements, flight model-based estimates, and sensor fusion techniques) into a single blended airspeed calculation. This merging allows the system to leverage the strengths of each method while compensating for their individual weaknesses, particularly improving low-speed measurement precision by blending pitot data with model-based estimates when pitot signals become unreliable.
Solution Approach 2:
The system dynamically changes the weighting parameters of different airspeed estimation methods based on flight conditions. At low airspeeds, the blend ratio shifts to rely more on flight model estimates and less on pitot probe data, while at higher speeds, it transitions to relying more on direct pitot measurements. This parameter adaptation resolves the contradiction by optimizing measurement precision for each speed regime.
2Measurement precision
If a single airspeed measurement method is used, then system complexity is reduced, but measurement precision deteriorates at low airspeeds
Solution Approach 1:
The airspeed measurement system implements dynamic switching and blending of multiple estimation methods based on real-time flight conditions. The system continuously monitors airspeed ranges and automatically adjusts the blend ratio between different measurement methods, creating a dynamic measurement system that adapts to low-speed and high-speed regimes without requiring manual intervention or complex hardware changes.
Solution Approach 2:
The flight control computer is designed to perform multiple functions: it processes pitot probe data, executes flight models, fuses sensor information, and dynamically blends airspeed estimates. This multi-functional approach allows a single system to achieve high measurement precision across all speed ranges without requiring separate dedicated systems for different airspeed regimes, thereby managing complexity while improving precision.
3Ease of operation
If airspeed probe data is used alone, then measurement simplicity is maintained, but handling qualities and control efficiency deteriorate at low airspeeds
Solution Approach 1:
The system implements continuous feedback by monitoring the reliability of pitot probe data and dynamically adjusting the blend ratio of airspeed estimation methods. When low airspeed conditions are detected, the system automatically increases reliance on flight model estimates, providing timely feedback to the control system about actual airspeed. This feedback mechanism improves handling qualities and control responsiveness without requiring complex manual adjustments or pilot training.
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
The blended airspeed approach provides a more accurate calculation of airspeed at low speeds, improving the handling qualities, performance, stability, and efficiency of rotary-wing aircraft, while also enhancing health and usage monitoring of aircraft components.
Implementation Method 1
A method and system blend airspeed data from airspeed probes with aircraft state information, using fade values to determine a blended airspeed that is more accurate at low airspeeds by weighting the measured and estimated airspeeds based on their confidence levels.
Data Source
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AI summary
A method for controlling a rotary wing aircraft includes determining a measured airspeed of the rotary wing aircraft based on data from a pitot probe, determining an estimated airspeed of the rotary wing aircraft based on rotor control commands, and determining a blended airspeed based on both the measured airspeed and the estimated airspeed.