Deflectable Stabilizer Control for High-Speed Rotorcraft Pitch
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Solution Overview
Problem
The existing methods for controlling pitch stabilization in rotorcrafts face challenges in managing pitch moment instability, particularly at high speeds, leading to increased aerodynamic drag, discomfort for crew and passengers, and adverse effects on the main rotor components due to the complexity of dimensioning and limitations in wing surface size, which result in suboptimal performance and increased workload during landing phases.
Innovation Solution
A method for controlling the steering angle of a pitch stabilization means using a control law that sets a setpoint angle based on flight parameters and incidence parameters, allowing for continuous adjustment over the entire flight envelope without the need for direct incidence measurement, utilizing usual instrumentation and potentially including multiple actuator control for aerodynamic stabilization surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the pitch stabilization system is designed to achieve a longitudinal attitude close to zero for high-speed performance, then the aircraft's maximum speed and aerodynamic efficiency are improved, but the main rotor operation becomes suboptimal due to the steep nose-down attitude required for high forward speed
Solution Approach 1:
The pitch control function is segmented between the longitudinal cyclic control (pilot input) and the pitch stabilization system (automatic control). The stabilization system independently adjusts the stabilizer angle to optimize aircraft attitude without interfering with the pilot's direct control of main rotor pitch, allowing simultaneous optimization of both high-speed performance and rotor operation.
Solution Approach 2:
The pitch stabilization system acts as an intermediary device between the pilot's cyclic control and the aircraft's overall attitude. By controlling the stabilizer surface separately, it mediates the conflict between desired nose-down attitude for speed and stable attitude for rotor operation, achieving both goals simultaneously.
2Reliability
If the wing area of the pitch stabilization system is increased to reduce the effects of disturbances related to variations in mass and center of gravity, then the stabilization effectiveness is improved, but significant variations in pitch attitude occur during flight phases where main rotor airflow impacts the stabilization system
Solution Approach 1:
The pitch stabilization system uses dynamic control through a positioning device that continuously adjusts the stabilizer angle based on real-time flight conditions. This dynamic adjustment allows the system to maintain effectiveness across varying mass and center of gravity conditions without requiring excessive wing area, thereby avoiding the pitch hump phenomenon and airflow interference issues.
Solution Approach 2:
The control law modifies the stabilizer angle parameter as a function of flight parameters including mass variations and center of gravity position. By dynamically changing this geometric parameter, the system maintains optimal stabilization effectiveness without needing a large fixed wing area that would cause airflow interference.
3Measurement precision
If dedicated instrumentation is used to directly measure the angle of attack for control, then the measurement precision is improved, but the device complexity and cost increase due to additional mass and instrumentation requirements
Solution Approach 1:
The system uses standard flight instruments (airspeed indicator, altimeter, attitude indicator) as intermediaries to indirectly determine angle of attack. Rather than directly measuring angle of attack with dedicated sensors, the control law processes data from existing instruments to calculate the required stabilizer angle, eliminating the need for complex additional instrumentation.
Solution Approach 2:
Instead of directly measuring the physical angle of attack parameter, the system creates a computational copy or representation of this parameter by processing data from standard flight instruments. This virtual measurement approach provides sufficient precision for control purposes without requiring physical angle of attack sensors.
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
This approach enables precise control of the pitch stabilization means to maintain desired attitudes, reduce power consumption, and minimize loads on the rotor, improving stability and reducing adverse effects on the aircraft's components, while avoiding the need for costly and mass-additive dedicated instrumentation.
Implementation Method 1
aerodynamic moment exerted on the rotorcraft's fuselage due to variations in its angle of attack relative to the upstream airflow
Data Source
Figure 1~2
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Figure 6~8
AI summary
The present invention relates to a method for controlling a steering angle of a pitch stabilization means of an aircraft. This method comprises a preliminary phase for developing at least one control law providing a setpoint angle (100*) that said steering angle must reach as a function of at least one flight parameter of the aircraft (1) and of an incidence parameter of the pitch stabilization means (10). During an operational phase (STP2), a value called "flight value (51)" of each of said flight parameters is determined, a value called "setpoint value (60*)" of said incidence parameter is determined, determines a setpoint angle (100*) by introducing said flight (51) and setpoint (60*) values into said control law (200), at least one actuator is activated so that said steering angle of the stabilization means in pitch reaches said setpoint angle.