Layered Elastomeric Load Sensor for Micro-Displacement Detection
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Solution Overview
Problem
Conventional weight on wheel sensors for VTOL aircraft require significant displacement of components to detect air-to-ground transitions, leading to undesirable delays in switching control logic.
Innovation Solution
A load sensor with a compressible body and strain gauges is positioned between two surfaces to detect compressive forces, providing an early indication of air-to-ground transition by measuring deformations in the strain gauges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional weight on wheel sensors (limit switches or proximity switches) are used to detect air-to-ground transition, then the detection function is achieved, but significant displacement of components is required which causes delay in switching control logic
Solution Approach 1:
The patent changes the measurement parameter from large displacement detection (conventional sensors) to micro-displacement detection (strain gauge measuring minute deformations of the middle shim). The strain gauge detects changes in resistance caused by extremely small deflections of the middle shim, enabling detection of air-to-ground transition with minimal component displacement, thus reducing the time delay in switching control logic while maintaining detection sensitivity
Solution Approach 2:
The patent replaces the mechanical displacement-based detection system (limit switches or proximity switches requiring significant component movement) with an electrical measurement system (strain gauge converting mechanical deformation into electrical resistance changes). This substitution allows detection of micro-displacements through electrical signals, eliminating the need for large mechanical displacements and reducing the time delay in control logic switching
2Loss of time
If strain gauge is coupled to the middle shim in the unsupported area, then micro-displacements are detected providing early indication of air-to-ground transition, but the structure becomes more complex with multiple shims and resilient material layers
Solution Approach 1:
The patent divides the compressible body into multiple discrete layers: first outer shim, middle shim, and second outer shim, with resilient material layers between them. This segmentation allows the middle shim to be specifically designed with an unsupported area for strain gauge coupling, enabling micro-displacement detection without requiring complex overall structure. Each layer has a specific function, and the modular design facilitates assembly and maintenance
Solution Approach 2:
The resilient material layers act as intermediaries between the outer shims and the middle shim. These resilient layers transmit and distribute compressive forces while allowing the middle shim to deflect in the unsupported area. The intermediary resilient materials enable the detection function while maintaining structural integrity, balancing the need for detection capability with structural simplicity
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
Enables timely switching of control logic from in-the-air to on-the-ground modes by detecting micro-displacements, reducing delays in VTOL aircraft landing maneuvers.
Implementation Method 1
A strain gauge is coupled to the middle shim in the unsupported area. When the compressible body is in a compressed state between the two surfaces, the resilient material aligned with the unsupported area and interposed between the first outer shim and the middle shim has a nonuniform thickness such that the middle shim deflects away from the first outer shim in the unsupported area, thereby deforming the strain gauge.
Implementation Method 2
The compressible body has a plurality of aligned layers including first and second outer shims with a middle shim positioned therebetween and with a resilient material interposed between each adjacent shim.
Data Source
AI summary
A load sensor includes a compressible body positionable between two surfaces. The compressible body has a plurality of aligned layers including first and second outer shims with a middle shim positioned therebetween and with a resilient material interposed between each adjacent shim. The second outer shim has a gap that exposes an unsupported area of the middle shim. A strain gauge is coupled to the middle shim in the unsupported area. When the compressible body is uncompressed, the resilient material interposed between the first outer shim and the middle shim has a substantially uniform thickness. When the compressible body is compressed between the two surfaces, the resilient material aligned with the unsupported area and interposed between the first outer shim and the middle shim has a nonuniform thickness such that the middle shim deflects away from the first outer shim in the unsupported area, thereby deforming the strain gauge.