Electric Cable Bending Sensor with Asymmetric Strength Member

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Solution Overview

Problem

Heavy-duty electric cables used in mobile installations face challenges in monitoring and detecting bending strains, which can lead to premature damage and maintenance issues due to harsh environments and mechanical stresses, necessitating a solution for real-time monitoring and localization of bending strains to ensure long-term reliability.

Innovation Solution

Incorporating a peripheral mechanically non-symmetrical strength member and an optical fiber sensor located along the geometrical axis of the cable, allowing for the detection of compressive strains and bending through mechanical congruence between the longitudinal structural elements and the strain sensor, enabling reliable measurement of static and dynamic compressive loads across a large range of elongations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an optical fiber sensor is embedded in the cable to detect bending strain, then measurement precision is improved, but the cable structure becomes more complex

Engineering Contradiction:

Improvebending strain detection accuracyVSAvoidcable structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The optical fiber sensor is embedded within the cable structure, with the fiber positioned in the neutral axis region and surrounded by protective layers and strength members. This nesting approach integrates the sensing function into the cable without adding external components, resolving the contradiction between measurement precision and device complexity

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

A strain-transferring filler material is introduced as an intermediary between the optical fiber sensor and the cable's longitudinal structural elements. This filler ensures mechanical congruence and effective strain transfer from the cable to the fiber, enabling accurate bending strain detection while maintaining a compact integrated structure

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the optical fiber sensor is positioned in the neutral axis region to avoid tensile strain, then reliability is improved, but measurement precision of bending strain is reduced

Engineering Contradiction:

Improvesensor durabilityVSAvoidbending strain detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

A peripheral mechanically non-symmetrical strength member is introduced to create an asymmetric stress distribution in the cable cross-section. This asymmetry causes the neutral axis to shift from the geometrical axis, positioning it closer to the optical fiber sensor and enhancing bending strain detection sensitivity while the fiber remains in a protected position

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The mechanical properties and positioning of the peripheral strength member are optimized to control the neutral axis position. By adjusting the strength member's characteristics, the system achieves optimal balance between fiber protection and bending strain sensitivity, resolving the contradiction between reliability and measurement precision

Inventive Principle:

Principle #35Parameter changes

3Reliability

If real-time monitoring of bending strain is implemented, then reliability is improved, but use of energy increases

Engineering Contradiction:

Improvecable condition monitoringVSAvoidenergy consumption for monitoring

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The optical fiber sensor provides passive, intrinsic sensing capabilities without requiring external power sources at the measurement location. The Brillouin scattering-based detection method uses the fiber itself as both the sensing element and the transmission medium, enabling real-time monitoring with minimal energy consumption

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Traditional active sensing systems with powered sensors and signal processing electronics are replaced by passive optical fiber sensing based on Brillouin scattering. This substitution eliminates the need for local power sources and complex electronic systems, significantly reducing energy consumption while maintaining real-time monitoring capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables real-time monitoring and localization of bending strains, preventing damage from fatigue and unexpected out-of-service events, facilitating effective periodic maintenance and reducing costs by detecting permanent damage and improper use, while ensuring the cable's reliability and longevity.

Implementation Method 1

the use in an electric cable... by utilizing one of optical fibre cores in an optical cable... measuring the strain in optical fibres attached to or incorporated into the power cable... by means of optical time domain reflectometer (OTDR) or optical frequency domain reflectometer (OFDR)

Methodology Applied

Scientific EffectBrillouin backscattering: Brillouin Scattering

Data Source

PatentUS9032809B2Electric cable with bending sensor and monitoring system and method for detecting bending in at least one electric cable

Publication Date: 2015.05.19 PRYSMIAN SPA

AI summary

A method for monitoring at least the bending strain of at least one electric cable provided with at least one peripheral mechanically non-symmetric strength member is provided.