Accelerometer-Based Angle-of-Attack Estimation for Unpowered Flight
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Solution Overview
Problem
In aerospace applications, determining the aerodynamic angle-of-attack for small vehicles is challenging due to the size and weight constraints of traditional measurement methods, which often require external probes that are expensive and impractical.
Innovation Solution
A method using an accelerometer on the vehicle to determine body-fixed load factor measurements, which are then used to calculate an angle-of-attack parameter without the need for pitot-static systems 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 for direct angle-of-attack measurement, then measurement precision is improved, but device complexity and weight 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 computational methods rather than direct physical probing, the system eliminates the need for complex external measurement devices while maintaining measurement capability.
Solution Approach 2:
The patent replaces the mechanical probe-based measurement system with an accelerometer-based inertial measurement system. Instead of using physical vanes, cones, or pressure probes that mechanically interact with the airflow, the system uses accelerometers to measure body-fixed accelerations and computationally derives angle-of-attack, substituting mechanical measurement with inertial sensing and mathematical processing.
2Measurement precision
If pitot-static systems are used for angle-of-attack estimation, then measurement precision is improved, but weight and device complexity increase
Solution Approach 1:
The patent extracts the angle-of-attack measurement function from the pitot-static system and implements it using only an accelerometer. By removing the dependency on pitot tubes and static ports, the system eliminates the associated weight while preserving the capability to determine angle-of-attack through alternative inertial measurement and computational methods.
Solution Approach 2:
The patent substitutes the pitot-static pressure measurement system with an accelerometer-based inertial measurement system. Instead of relying on pressure differential measurements from pitot and static ports, the system uses body-fixed acceleration measurements and derives angle-of-attack through mathematical relationships, replacing a heavier pressure-based system with a lighter acceleration-based system.
3Measurement precision
If accurate inertial measurements are obtained through traditional methods, then angle-of-attack estimation precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the accelerometer serve multiple functions: it measures both the magnitude and direction (body-fixed components) of acceleration, which are then used together to determine angle-of-attack. By utilizing the full capability of a single accelerometer sensor rather than requiring separate specialized sensors, the system reduces device complexity while maintaining measurement precision.
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, optimizing flight profiles and eliminating the need for bulky and heavy sensors, thereby improving performance and efficiency.
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.