Translational Inerter Assembly for Flight Control Surface Damping
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Solution Overview
Problem
Aircraft flight control systems face challenges in preventing flutter of flight control surfaces due to overlapping operating bandwidth and resonant frequency, leading to increased weight, aerodynamic drag, and reduced controllability, with existing solutions either complicating the system or increasing size and weight.
Innovation Solution
A translational inerter assembly is introduced, comprising a press fit element, an inertia element with helical splines, and a torsion bar, which dampens movement of flight control surfaces by translating the inertia element along a hinge axis, allowing the operating bandwidth to match or encompass the resonant frequency without oscillatory response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the operating bandwidth is designed not to overlap the resonant frequency of the flight control surface, then flutter is prevented, but the actuator system must be sized to react larger inertia loads, resulting in increased actuator size and weight
Solution Approach 1:
The patent changes the dynamic parameters of the actuator system by adding an inerter device that modifies the effective inertia and damping characteristics. This allows the system to maintain stability at resonant frequencies without requiring oversized actuators, thus resolving the contradiction between flutter prevention and actuator weight reduction
2Reliability
If the piston cross-sectional area of the actuator is increased to react inertia loads, then the ability to avoid resonance is improved, but the size and weight of the hydraulic system components increase
Solution Approach 1:
The patent replaces the traditional mechanical approach of increasing piston area with a mechanical device (inerter) that uses inertial forces and damping to achieve resonance avoidance. This substitution allows for smaller hydraulic components while maintaining the same stability performance
3Force
If the actuator size is increased to provide static load-carrying capability, then the ability to react inertia is improved, but the actuators protrude further outside the outer mold line, resulting in increased aerodynamic drag
Solution Approach 1:
The inerter device changes the dynamic parameters of the actuator system, enabling smaller actuators to achieve the same inertia reaction capability through modified effective mass and damping characteristics, thereby reducing aerodynamic drag from protruding components
4Reliability
If the control surface area is decreased to limit control surface inertia, then the resonant frequency overlap is avoided, but the attitude controllability of the aircraft is reduced
Solution Approach 1:
The patent substitutes the mechanical constraint of limiting control surface area with a dynamic damping system (inerter) that allows larger control surfaces to be used while maintaining stability through active inertia management and damping forces
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
The solution effectively reduces actuator load oscillatory amplitude, decreases the size and weight of hydraulic systems, and enhances dynamic response, thereby improving aircraft performance by reducing aerodynamic drag and increasing fuel efficiency and payload capacity.
Implementation Method 1
The torsion bar has a plurality of exterior linear splines corresponding to a plurality of interior linear splines of the inertia element. Rotation of the flight control surface causes translational movement of the inertia element, via the press fit element, along a hinge axis of the flight control surface and along the torsion bar, resulting in the translational inerter assembly damping movement of the flight control surface.
Implementation Method 2
The inertia element has a plurality of exterior helical splines corresponding to a plurality of interior helical splines of the press fit element. Rotation of the flight control surface causes translational movement of the inertia element, via the press fit element, along a hinge axis of the flight control surface
Data Source
AI summary
There is provided a translational inerter assembly for damping movement of a flight control surface of an aircraft. The assembly has a press fit element fixedly disposed within a first end of the flight control surface and rotatably movable with the flight control surface. The assembly further has an inertia element coupled to and installed in the press fit element. The assembly further has a torsion bar having a torsion bar first end coupled to and installed in the inertia element, and having a torsion bar second end fixedly attached to a support structure of the aircraft. Rotation of the flight control surface causes translational movement of the inertia element, via the press fit element, along a hinge axis of the flight control surface and along the torsion bar, resulting in the translational inerter assembly damping movement of the flight control surface.