Capacitive Strain Sensor Core Ring Structure for Shear Measurement
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Solution Overview
Problem
Aircraft landing gear strains are difficult to accurately assess due to subjective inspection criteria and limitations in existing strain gauges, which can lead to unnecessary inspections or missed opportunities, and current sensors have limited sensing range and are affected by temperature and material properties.
Innovation Solution
A capacitive strain sensor with a core and ring structure featuring metallic coatings and capacitive plates, allowing for precise measurement of shear strains through differential capacitance changes, is designed to be attached to aircraft landing gear, providing improved sensitivity and resistance to deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional strain gauges are used, then measurement capability is provided, but sensing range is limited to maximum stress allowed by the sensing element
Solution Approach 1:
The patent replaces conventional mechanical strain gauges with a capacitive sensing system. The capacitive sensor measures displacement between a movable plate and a fixed plate to determine strain, eliminating the mechanical stress limitations of traditional gauges and enabling measurement of larger deformations in landing gear structures.
2Measurement precision
If conventional strain gauges are used, then strain measurement is achieved, but temperature and material properties affect detected resistance
Solution Approach 1:
The patent replaces resistance-based measurement with capacitance-based measurement. Capacitive sensing measures the electric field between plates rather than electrical resistance, making the measurement immune to temperature drift and material property variations that plague conventional strain gauges.
Solution Approach 2:
The patent introduces a dielectric material between the capacitive plates as an intermediary element. This dielectric enhances the capacitive coupling and provides thermal stability, further isolating the measurement from temperature effects while maintaining sensitivity to mechanical displacement.
3Ease of operation
If subjective inspection criteria are used, then inspection decisions can be made, but over-or under-reporting occurs leading to unnecessary inspections or missed opportunities
Solution Approach 1:
The patent implements continuous real-time monitoring of strain in landing gear structures. The capacitive sensors provide ongoing feedback on structural deformation, enabling objective assessment of component health and replacement timing, eliminating subjective judgment and ensuring inspections occur based on actual measured conditions rather than estimates.
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 capacitive strain sensor effectively measures shear strains with enhanced sensitivity and accuracy, reducing the risk of catastrophic failure by providing objective data for inspection and maintenance decisions, while minimizing errors from temperature and material variations.
Implementation Method 1
a capacitive strain sensor for sensing strain, the sensor comprising: a first section configured and adapted to be attached to a structure at a first location, the first section including: a core; and a first capacitor plate being electrically isolated from the structure; a second section configured and adapted to be attached to the structure at a second location, the second section including: a ring having an inner diameter that is greater than the outer diameter of the core; and a pair of opposed capacitive plates being electrically isolated from the structure; and a device configured to flexibly connect the first section to the second section, wherein the core and ring have dimensions along a longitudinal axis, wherein the capacitive plate of the first section is separated from the opposed capacitive plates of the second section by a capacitive gap therebetween; and wherein strain experienced by the structure to which the sensor is attached causes a change in the capacitive gaps due to relative motion between the first and second sections
Data Source
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AI summary
A capacitive strain sensor for sensing strain of a structure. The sensor includes a first section attached to the structure at a first location and a second section attached to the structure at a second location. The first section includes a capacitor plate electrically isolated from the structure and the second section includes two electrically isolated capacitive plates, both of the plates being electrically isolated from the structure. A flexible connector connects the first section to the second section. The capacitor plate of the first section is separated from the two capacitive plates of the second section by at least one capacitive gap. When strain is experienced by the structure, a change occurs in the capacitive gap due to relative motion between the first and second sections. The first section includes a core and the second section includes a ring that receives the core.