Magnetic Field Sensor Array for Composite Airframe Current Density Mapping

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Solution Overview

Problem

Measuring current density over composite airframes during lightning strikes is complex due to non-homogenous current distribution and the difficulty in predicting current density across large surface areas, especially with composite materials exhibiting non-isotropic conductivity.

Innovation Solution

A method and apparatus using a plurality of magnetic field sensors arranged in an array to measure changes in magnetic field strength, with integrators converting sensor outputs to magnetic field strength values, allowing inference of current density over the target surface by mapping local current values to corresponding sensor locations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If conventional metal exteriors with isotropic conductivity are used, then current density is uniform and easy to measure, but modern airplanes cannot achieve the desired weight reduction and flexibility

Engineering Contradiction:

Improveairplane weightVSAvoidcurrent density measurement

Core Design Contradiction:

Weight of moving objectVSMeasurement precision

Solution Approach 1:

The patent divides the large surface area into multiple smaller measurement zones by deploying an array of sensors across the surface. Each sensor measures current density at its local position, and the collective data from all sensors reconstructs the overall current distribution pattern, making measurement feasible on composite surfaces

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces direct electrical contact measurement methods with magnetic field sensing. By using magnetic sensors that detect the magnetic field generated by current flow, the system avoids the complexity of embedding electrical contacts in composite materials while achieving accurate current density measurement

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If composite materials with non-isotropic conductivity are used, then weight and flexibility are improved, but current density becomes non-homogenous and difficult to predict

Engineering Contradiction:

Improvematerial flexibilityVSAvoidcurrent density distribution

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent applies different measurement approaches for different regions of the composite surface. By positioning sensors at specific locations and orienting them according to the local fiber direction and conductivity characteristics, the system accurately captures the non-uniform current density distribution that arises from anisotropic material properties

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent measures and maps the directional conductivity parameters of the composite material to understand how current flows differently in various directions. This information is used to interpret sensor readings and reconstruct accurate current density distributions that account for the material's anisotropic nature

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If a single spot current measurement is used, then measurement simplicity is maintained, but representativeness of the entire surface is lost

Engineering Contradiction:

Improvemeasurement simplicityVSAvoidsurface current distribution information

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The patent combines measurements from multiple sensors into a unified current density map of the entire surface. By merging the data from all sensor locations and using spatial interpolation techniques, the system creates a comprehensive view of current distribution that preserves all surface information while maintaining operational simplicity through automated processing

Inventive Principle:

Principle #5Merging (Combining)

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 accurate inference of current density over composite airframes, providing a high-granularity view of current distribution and compensating for individual sensor differences through calibration, effectively addressing the challenges of measuring current density in composite materials.

Implementation Method 1

A plurality of magnetic field sensors, such as arranged in an array, is operative to measure changes in magnetic field strength proximate the surface(s) of a test structure

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

A corresponding plurality of integrators converts the sensor outputs to magnetic field strength values

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP3441774B1Large surface magnetic field sensor array and method of analysing an electrical current over a surface

Publication Date: 2022.07.27 THE BOEING CO

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Figure 6A

AI summary

A plurality of magnetic field sensors (26), for example arranged in an array (30), is operative to measure changes in magnetic field strength proximate the surface(s) (18, 24) of a test structure (10). The test structure (10) may approximate the geometry of an airplane fuselage, wing, or the like. An electric current is applied to the test structure (10), and the magnetic field sensors (26) sense changes in a magnetic field caused by the current. A corresponding plurality of integrators (32) convert the sensor (26) outputs to magnetic field strength values. From the plurality of magnetic field strength values and corresponding sensor locations (27), a current density over the target surface (10) is inferred.