Elastomeric Strain Gauge Load Sensor for Early Weight-on-Wheel Detection

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Solution Overview

Problem

Conventional weight on wheel sensors in VTOL aircraft require significant displacement of components for air-to-ground transition detection, 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 early transitions from air to ground by measuring compressive forces, utilizing a compressible body with aligned metallic shims and elastomeric material layers to deform strain gauges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional weight on wheel sensors are used, then air-to-ground transition detection is achieved, but significant component displacement is required causing delay in control logic switching

Engineering Contradiction:

Improveair-to-ground transition detection accuracyVSAvoiddelay in control logic switching

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The invention changes the detection parameter from macroscopic component displacement to microscopic strain gauge deformation. The strain gauges detect minute changes in the compressible body's dimensions, allowing transition detection at much smaller displacement thresholds, thereby reducing the time delay in control logic switching while maintaining detection reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces conventional mechanical displacement-based detection with electrical strain measurement. Instead of relying on mechanical switches or proximity sensors that require significant component movement, the patent uses strain gauges that convert mechanical deformation into electrical signals, enabling detection with minimal physical displacement

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If strain gauges are coupled to the middle shim in the unsupported area, then micro-displacement detection is enabled, but the structure becomes more complex

Engineering Contradiction:

Improvemicro-displacement detection capabilityVSAvoidsensor structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The compressible body is segmented into multiple shims (first outer shim, middle shim, second outer shim) with resilient material layers between them. This segmentation allows the middle shim to deflect independently in unsupported areas when strain gauges are applied, enabling precise micro-displacement detection while distributing the structural complexity across modular components

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The resilient material layers act as intermediaries between the outer shims and the middle shim. These layers allow controlled deformation and energy distribution, enabling the middle shim to exhibit measurable deflection in unsupported areas while maintaining overall structural integrity, thus achieving precise measurement without excessive complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

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, providing an early indication of air-to-ground transition without significant component displacement.

Implementation Method 1

the resilient material interposed between the first outer shim and the middle shim has a substantially uniform thickness. 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.

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

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.

Methodology Applied

Scientific EffectStrain gauge deformation: Piezoresistive Effect

Data Source

PatentUS20260043694A1Elastomeric Strain Gauge Load Sensors

Publication Date: 2026.02.12 TEXTRON INNOVATIONS INC

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 the first outer shim and the middle 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 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.