Fiber Bragg Grating Displacement Sensor Using Shape-Memory Alloy Tube
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring changes in ligament length, particularly in biological tissues, face limitations such as excessive bulk, weight, cost, attachment issues, poor accuracy, and noise, especially when dealing with low-modulus and viscoelastic materials.
Innovation Solution
A lightweight and compact Fiber Bragg Grating (FBG) displacement sensor is developed, where a quartz fiber with etched regularly spaced lines is potted in a shape-memory alloy (SMA) tube, allowing for accurate measurement of deformation by detecting shifts in reflected laser light wavelength, and is securely attached using thin copper tabs or adhesive for reliable data capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional transducers are attached to measure deformation, then measurement capability is achieved, but excessive bulk and weight are introduced
Solution Approach 1:
The patent replaces traditional mechanical transducers with an optical sensing system using Fiber Bragg Grating (FBG). The FBG sensor uses optical fiber with periodic refractive index variations to detect strain through wavelength shifts, eliminating the need for heavy mechanical components while maintaining measurement capability.
Solution Approach 2:
The patent employs a thin flexible substrate that can be attached to the surface being measured. This thin-film approach minimizes the sensor's bulk and weight while allowing conformal attachment to the target surface for accurate deformation measurement.
2Measurement precision
If optical methods are used to track surface markings, then non-contact measurement is achieved, but excessive cost is incurred
Solution Approach 1:
The patent extracts the sensing function from complex optical systems and implements it directly in the optical fiber itself through FBG technology. The FBG acts as both the sensing element and the signal source, eliminating the need for expensive external optical components like cameras and complex illumination systems.
Solution Approach 2:
The patent uses the optical fiber to carry measurement information back to the measurement system, effectively copying the strain information onto the light signal. This allows simple and inexpensive detection equipment to read the wavelength shifts and determine displacement measurements.
3Measurement precision
If transducers are attached to substrate surfaces, then measurement capability is achieved, but unreliable attachment and measurement artifacts occur
Solution Approach 1:
The patent uses a thin flexible substrate that can be conformally attached to the surface being measured. This thin-film approach minimizes interference with the underlying structure and reduces measurement artifacts while maintaining reliable attachment through surface bonding.
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 FBG sensor provides high sensitivity, low noise, and reproducible results, outperforming traditional stereo-optic methods with improved accuracy and reduced signal drift, suitable for measuring displacements in various applications including biological tissues.
Implementation Method 1
when the outer surface of a quartz fiber (fiber optic cable) is etched to form a series of regularly spaced lines (a Fiber Bragg grating), laser light of a wavelength matching the spacing of the lines which enters one end of the fiber will be preferentially reflected
Implementation Method 2
when the outer surface of a quartz fiber (fiber optic cable) is etched to form a series of regularly spaced lines (a Fiber Bragg grating), laser light of a wavelength matching the spacing of the lines which enters one end of the fiber will be preferentially reflected
Implementation Method 3
This fiber is potted with epoxy resin in a narrow tube fabricated from a shape-memory alloy (SMA), and pre-formed into a curved shape. This not only protects the quartz fiber from direct contact with other objects and excessive bending, but also causes it to deform in a predictable fashion, thereby generating a reproducible response to displacement
Implementation Method 4
Due to the high elastic behavior of the SMA tube, a displacement sensor with a gage length of 40 mm can measure displacements in excess of 3 mm
Data Source
AI summary
A displacement sensor based on the underlying principle that when the outer surface of a quartz fiber (fiber optic cable) is etched to form a series of regularly spaced lines (a Fiber Bragg grating), laser light of a wavelength matching the spacing of the lines which enters one end of the fiber will be preferentially reflected. If the fiber is deformed, causing the line spacing to change, the wavelength of the reflected light will also change. This shift can be accurately measured and so can be related to the magnitude of the deformation of the fiber. This fiber is potted with epoxy resin in a narrow tube fabricated from a shape-memory alloy (SMA), and pre-formed into a curved shape. This not only protects the quartz fiber from direct contact with other objects and excessive bending, but also causes it to deform in a predictable fashion, thereby generating a reproducible response to displacement. Due to the high elastic behavior of the SMA tube, a displacement sensor with a gage length of 40 mm can measure displacements in excess of 3 mm.