Flight Computer Angle-of-Attack Estimation from Body-Fixed Load Factors
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Solution Overview
Problem
In aerospace applications, determining the aerodynamic angle-of-attack for small vehicles is challenging due to the difficulty in accurately measuring or estimating this parameter without using external probes, which are often prohibitively expensive and/or impractical due to size and weight constraints.
Innovation Solution
A method utilizing an accelerometer on the vehicle to determine body-fixed load factor measurements, which are then used to calculate an angle-of-attack parameter through a flight computer system without requiring a pitot-static system or external probes, allowing for direct determination and adjustment of the angle-of-attack for optimal lift-to-drag ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external probes (vane, cone, or pressure probe) are used to directly measure angle-of-attack, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the angle-of-attack measurement function from external probes and relocates it to an onboard accelerometer system. By measuring body-fixed accelerations and deriving angle-of-attack through computation rather than direct external measurement, the system eliminates the need for complex external probe hardware while maintaining measurement capability.
Solution Approach 2:
The patent replaces the mechanical probe system with an accelerometer-based measurement system. Instead of using physical probes that directly interact with the airflow to measure angle-of-attack, the system uses accelerometers to measure body-fixed accelerations and computationally derives the angle-of-attack, substituting mechanical measurement with inertial sensing and mathematical processing.
2Measurement precision
If pitot-static system is used to obtain accurate airspeed measurement for angle-of-attack estimation, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the airspeed measurement function from the pitot-static system and replaces it with an accelerometer-based approach. By using body-fixed acceleration measurements and deriving airspeed information through computational processing of inertial data, the system eliminates the need for pitot tubes and static ports while maintaining the capability to determine angle-of-attack.
Solution Approach 2:
The patent substitutes the pitot-static mechanical measurement system with an inertial measurement system. Instead of using pressure-based airspeed measurement, the system uses accelerometers to capture motion data and computationally derives the necessary flight parameters, replacing pressure-based mechanics with inertial sensing and mathematical computation.
3Device complexity
If inertial measurement system is used to estimate angle-of-attack, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where body-fixed acceleration measurements are continuously processed through a monotonic portion of a lookup curve to determine angle-of-attack. The system uses the measured accelerations, applies appropriate transformations and quotients, and references a pre-determined monotonic portion of the angle-of-attack operating plot to accurately estimate the current angle-of-attack, ensuring measurement precision through systematic computational feedback.
Solution Approach 2:
The patent performs preliminary action by pre-determining the monotonic portion of the angle-of-attack operating plot before flight operations. This lookup curve is established in advance based on vehicle characteristics, allowing the onboard computer to quickly and accurately determine angle-of-attack during flight by simply referencing the pre-computed curve with current acceleration measurements, thereby improving real-time measurement precision without adding complexity.
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 determination and adjustment of the angle-of-attack for small vehicles, such as gliders, without the need for bulky or heavy sensors, thereby improving flight efficiency and maximizing distance coverage.
Implementation Method 1
determining, by an accelerometer disposed on the unpowered vehicle, first and second accelerometer outputs, where the first and second accelerometer outputs correspond to first and second body-fixed load factor measurements, respectively
Data Source
AI summary
According to one implementation of the present disclosure, a method for determining angle-of-attack for an unpowered vehicle is disclosed. The method includes: determining a monotonic portion of a look-up curve of an angle-of-attack operating plot; during flight, determining, by an accelerometer disposed on the unpowered vehicle, first and second accelerometer outputs, where the first and second accelerometer outputs correspond to first and second body-fixed load factor measurements, respectively; determining an operating point on the monotonic portion by applying a quotient of the first and second accelerometer outputs to the angle-of-attack operating plot; and determining an angle-of-attack parameter corresponding to the determined operating point.