Rotor Blade Gyrometer Sensing for Accurate Cyclic Pitch Estimation
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Solution Overview
Problem
Existing methods for measuring the state of a rotorcraft rotor, including longitudinal and lateral cyclic pitches and cone angles, are complex, prone to errors, and inaccurate due to reliance on multiple sensors and neglect of aerodynamic forces.
Innovation Solution
A method utilizing direct measurements from a gyrometer, such as MEMS type, attached to a rotor blade to determine angular velocity components, processed through Fourier series analysis to estimate cyclic pitches and cone angles relative to the TPP disk plane, eliminating the need for additional sensors and reducing bias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors (flapping sensor on blade and non-flapping sensor on hub) are used to measure rotor state, then measurement coverage is improved, but device complexity and implementation difficulty increase
Solution Approach 1:
The invention extracts and eliminates the need for the non-flapping reference sensor on the hub by using only a single flapping sensor on the blade. The measurement system is simplified to use exclusively blade-mounted sensors, removing the complexity of coordinating multiple sensors while maintaining measurement capability through alternative calculation methods.
Solution Approach 2:
The flapping sensor on the blade is made to serve multiple functions: it directly measures blade flapping angle and indirectly enables determination of cyclic pitch and cone angle through mathematical relationships. This single sensor replaces what previously required multiple sensors, reducing system complexity while maintaining comprehensive measurement coverage.
2Measurement precision
If sensor measurements are integrated over time to estimate blade angles, then angle estimation is achieved, but prohibitive angle errors occur
Solution Approach 1:
The invention replaces the mechanical integration method (time integration of sensor measurements) with a mathematical calculation approach based on instantaneous measurements. By using direct mathematical relationships between measured flapping angle and desired blade angles (cyclic pitch, cone angle), the system eliminates cumulative integration errors while achieving accurate angle estimation.
3Measurement precision
If existing measurement methods are used, then rotor state can be determined, but significant inaccuracies occur due to neglecting aerodynamic forces
Solution Approach 1:
The invention incorporates aerodynamic force considerations into the measurement model by establishing mathematical relationships that account for the coupling between blade flapping, cyclic pitch, and aerodynamic forces. The measurement system uses feedback from the flapping sensor measurements to continuously refine the estimation of rotor state parameters, compensating for aerodynamic effects that were previously neglected.
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
Provides accurate and robust measurement of rotor states by eliminating sensor bias and errors, allowing precise estimation of cyclic pitches and cone angles, and enabling improved control and safety features like automatic takeoff.
Implementation Method 1
direct measurement of the evolution over time of an angular velocity component ωθ(t) of a blade around an articulation axis of this blade relative to an inertial reference frame by means of at least one sensor, comprising at least one gyrometer
Implementation Method 2
processing of this angular velocity component ωθ(t) following a Fourier series decomposition of this angular velocity component ωθ(t)
Data Source
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AI summary
The present invention relates to a device for determining the state of a rotor (11) of a rotorcraft (10). Said rotorcraft (10) comprises a fuselage (16) and a main rotor (11) equipped with a hub (13) rotating around a mast of said rotor (11) and a plurality of blades (14) whose second ends (142) describe a trajectory defining a plane of the disk (TPP). Said device includes a sensor for measuring an angular velocity (ωθ(t)) of a blade (14) about a pitch axis. The device (1) then makes it possible to determine a state of said rotor (11), comprising, for example, estimates of a longitudinal cyclic pitch (θ1S/TPP) and a lateral cyclic pitch (θ1C/TPP) of said blade (14) with respect to said plane of the disk (TPP).