Coaxial Cable Strain Sensor for 3D Shape Sensing

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Solution Overview

Problem

Existing strain measurement technologies face challenges in providing accurate, distributed, and three-dimensional shape sensing in mechanically harsh environments, where traditional sensing modalities like optical fibers are limited by mechanical durability and bending issues.

Innovation Solution

A novel coaxial cable strain sensor system utilizing Fabry-Perot interferometers or coaxial cable Bragg gratings, where multiple sensing elements are bundled to create a shape sensing device capable of accurate three-dimensional position measurement, leveraging the mechanical durability of coaxial cables and enabling distributed strain profiling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If optical fibers are used for strain sensing, then sensing capability is achieved, but mechanical durability deteriorates in harsh environments

Engineering Contradiction:

Improvemechanical durabilityVSAvoidbending limitations

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces traditional optical fiber-based sensing systems with coaxial cable-based sensing systems. The coaxial cable construction with distributed sensing elements provides both the mechanical durability needed for harsh environments and the sensing capability through electromagnetic field interactions, eliminating the mechanical fragility of optical fibers while maintaining sensing functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Length of stationary object

If distributed sensing is implemented over long distances, then spatial coverage is improved, but measurement precision deteriorates due to signal attenuation

Engineering Contradiction:

Improvesensing distanceVSAvoidstrain measurement accuracy

Core Design Contradiction:

Length of stationary objectVSMeasurement precision

Solution Approach 1:

The patent divides the long coaxial cable into multiple segments with distributed sensing elements (Fabry-Perot cavities, Bragg gratings, or impedance discontinuities) spaced along its length. Each sensing element independently measures strain at its local position, allowing distributed measurement over long distances while maintaining precision through localized detection rather than relying on signal propagation over the entire length.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses electromagnetic waves as intermediaries to interrogate the distributed sensing elements along the coaxial cable. The electromagnetic signals interact with each sensing element locally, enabling precise strain measurement at multiple positions along the cable without significant signal attenuation, as each element reflects or modulates the signal independently.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If multiple sensing elements are bundled for shape sensing, then three-dimensional measurement capability is improved, but device complexity increases

Engineering Contradiction:

Improvethree-dimensional shape sensing capabilityVSAvoidcable bundle configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent creates a universal sensing platform where a single coaxial cable construction can perform multiple functions: distributed strain measurement along its length, and when bundled with other coaxial cables, three-dimensional shape sensing. The same basic sensing element design (Fabry-Perot, Bragg grating, or impedance discontinuity) is used in all cables, simplifying the system architecture while enabling versatile 3D measurement capabilities through cable bundle configuration.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 system achieves accurate three-dimensional shape sensing with high spatial and temporal resolution, demonstrating linear and repeatable strain measurement with minimal crosstalk and a low strain detection limit, suitable for mechanically challenging applications.

Implementation Method 1

Individual strain sensing elements are constructed using Fabry-Perot interferometers

Methodology Applied

Scientific EffectFabry-Perot interferometer: Fabry-Perot Interferometer

Implementation Method 2

coaxial cable Bragg gratings

Methodology Applied

Scientific EffectBragg grating: Bragg Diffraction

Data Source

PatentUS10309843B2Coaxial cable sensor device for distributed strain measurement and shape sensing applications

Publication Date: 2019.06.04 UNIV OF RHODE ISLAND BOARD OF TRUSTEES

AI summary

The present disclosure provides a novel distributed coaxial cable strain sensor that can measure a strain profile over the entire length of a cable. Individual strain sensing elements are constructed using Fabry-Perot interferometers, coaxial cable Bragg gratings, or other reflectometry-based sensing structures. By assembling three or more strain sensors together in a bundle, a coaxial cable shape sensing device can be constructed which is capable of accurate three dimensional position measurement.