Variable-Area Shock Strut Metering for Adaptive Damping Control
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Solution Overview
Problem
Current aircraft landing gear shock struts with traditional metering pin systems face inefficiencies in controlling the rate of piston translation and energy dissipation, particularly due to fixed orifice areas which do not adapt to varying load conditions effectively.
Innovation Solution
A shock strut variable-area metering unit featuring a metering pin analog with variable area flutes and a translation shaft, positioned within an orifice plate, which changes operational orifice area in response to load pressure, allowing for controlled fluid flow and energy dissipation through a combination of variable area flutes and a return spring mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional metering pin system with fixed orifice area is used, then the structure is simple, but the adaptability to varying load conditions deteriorates
Solution Approach 1:
The patent applies the dynamics principle by replacing the fixed orifice area with a variable area mechanism. The metering pin analog moves axially in response to load pressure changes, dynamically adjusting the orifice area to match varying load conditions. This allows the system to adapt its metering characteristics in real-time, improving adaptability while maintaining a relatively simple overall structure through the use of a single moving component.
2Ease of operation
If a traditional metering pin system is used, then the energy storage capability is maintained, but the control over piston translation rate deteriorates
Solution Approach 1:
The patent implements feedback control through the metering pin analog, which automatically responds to load pressure changes. As the piston translates and load pressure varies, the metering pin analog moves to adjust the orifice area, providing continuous feedback control over the fluid flow rate. This ensures optimal control over piston translation rate while maintaining efficient energy dissipation through the variable area metering mechanism.
3Measurement precision
If a variable area metering mechanism is implemented, then the control precision over fluid flow improves, but the device complexity increases
Solution Approach 1:
The patent uses the metering pin analog as an intermediary element that translates load pressure changes into corresponding changes in orifice area. This single intermediary component provides precise control over fluid flow by mediating between the pressure differential across the orifice plate and the resulting flow rate. The approach achieves high control precision while minimizing complexity by using one well-designed intermediate element rather than multiple complex components.
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 solution enhances the control over the rate of piston translation and energy dissipation by mimicking traditional metering pin behavior, reducing the weight of the shock strut and improving adaptability to dynamic load conditions, while maintaining efficient energy storage and return capabilities.
Implementation Method 1
a trapped volume of gas is compressed as the shock strut is axially compressed, and a volume of oil is metered through a metering orifice. The gas acts as an energy storage device, similar to a spring
Implementation Method 2
Shock struts also dissipate energy by passing the oil through the orifice so that as the shock absorber is compressed or extended, its rate of motion is limited by the damping action from the interaction of the orifice and the oil
Implementation Method 3
the return spring is configured to force the metering pin analog back to an original position when a shock strut moves to an extended position from a compressed position
Data Source
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AI summary
A metering unit is provided. The metering unit includes a metering pin analog (406) and a translation shaft (410). The metering pin analog is configured to translate about the translation shaft in a first direction in response to a load pressure acting on an annular region of a bottom portion of the metering pin analog. The metering pin analog is configured to translate about the translation shaft in a second direction opposite the first direction in response to the load pressure ceasing.