Rotary Wing Load Alleviation via Rotor-Elevator Coordination
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Solution Overview
Problem
Rotary wing aircraft main rotor systems experience high forces and moments during maneuvers, leading to increased structural requirements and weight, as well as peak static and recurring fatigue loads that reduce component life.
Innovation Solution
A flight control system that includes a flight control computer interfacing with the main rotor and elevator systems, utilizing an inverse plant model, load alleviation control filter, and transformed elevator command filter to generate commands that reduce loads on the main rotor system by redistributing loads between the rotor system and tail section, while maintaining system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the main rotor system generates large pitch moments to overcome the stabilizing moment of the tail section, then pitch control is achieved, but the loads on the main rotor shaft and hub increase
Solution Approach 1:
The patent introduces an intermediary control system (flight control computer with load alleviation control) that mediates between the pilot's pitch commands and the actual rotor/elevator actuation. This intermediary processes the control inputs and coordinates between the main rotor system and elevator to achieve pitch control while distributing loads, preventing excessive forces on the main rotor shaft and hub.
Solution Approach 2:
The patent changes the control parameters by implementing a fly-by-wire system with sophisticated control laws that dynamically adjust the distribution of control authority between the main rotor and elevator. The system modifies how pitch moments are generated by coordinating rotor blade pitch changes with elevator deflection, thereby reducing peak loads on the main rotor while maintaining effective pitch control.
2Strength
If larger structural components are used to handle higher loads, then structural strength is improved, but aircraft weight increases
Solution Approach 1:
The patent applies preliminary action by using the load alleviation control system to proactively reduce loads on the main rotor system before peak loading conditions occur. The control system anticipates high-stress maneuvers and pre-adjusts the distribution of control forces between the rotor and elevator, preventing excessive loads from developing in the first place, thereby allowing for lighter structural design.
Solution Approach 2:
The patent implements feedback through the flight control computer that continuously monitors aircraft state and control inputs, and dynamically adjusts the load distribution between main rotor and elevator. This closed-loop control ensures that loads on the main rotor system are kept within acceptable limits during various maneuvers, enabling the use of lighter structural components that would not be required if loads were uncontrolled.
3Adaptability or versatility
If higher loads are applied to aircraft components, then maneuvering capability is improved, but component life decreases
Solution Approach 1:
The patent applies dynamics by implementing a dynamic load alleviation control system that continuously adapts the control law based on current flight conditions, maneuver type, and aircraft state. The system dynamically adjusts the distribution of control authority between the main rotor and elevator in real-time, allowing full maneuvering capability while keeping loads on components within safe limits to preserve component life.
Solution Approach 2:
The patent introduces an intermediary control layer that mediates between maneuvering commands and actual actuator responses. This intermediary (flight control computer with load alleviation logic) ensures that high-g maneuvering capability is achieved through coordinated control of both main rotor and elevator, while preventing excessive loads that would reduce component life, thus decoupling maneuvering performance from component stress.
Data Source
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AI summary
One aspect is a flight control system for a rotary wing aircraft including a main rotor system and an elevator control system. A flight control computer of the flight control system includes processing circuitry configured to execute control logic. The control logic includes an inverse plant model that produces a main rotor feed forward command based on a pitch rate command, and a load alleviation control filter configured to reduce loads on a main rotor system and produce an elevator command for an elevator control system. A transformed elevator command filter produces a main rotor pitch adjustment command based on the elevator command, and a main rotor command generator generates an augmented main rotor feed forward command for the main rotor system based on the main rotor feed forward command and the main rotor pitch adjustment command.