Fiber Bragg Grating Sensor for Axial and Rotational Displacement
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Solution Overview
Problem
Existing sensors fail to accurately measure rotational or linear displacement while effectively compensating for temperature-related effects, leading to inaccurate strain measurements.
Innovation Solution
The use of two Fiber Bragg Gratings (FBGs) disposed on opposite sides of a deformed structure, one experiencing tensile and the other compressive strain, with an interrogation unit and processor to derive the difference in wavelengths, allowing for temperature compensation and precise measurement of mechanical strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single Fiber Bragg Grating is used to measure strain, then the measurement setup is simple, but temperature effects cannot be compensated leading to inaccurate strain measurements
Solution Approach 1:
The sensor system is segmented into multiple independent Fiber Bragg Gratings (at least two) disposed at different locations on the structure. Each FBG independently measures strain at its location, and by segmenting the measurement function across multiple sensors, the system can distinguish between temperature effects (affecting all FBGs similarly) and mechanical strain (affecting FBGs differently based on their positions), thereby enabling temperature compensation and improving measurement accuracy
Solution Approach 2:
The patent introduces an intermediary processing system that receives wavelength signals from multiple FBGs, calculates wavelength differences, and correlates these differences to temperature and strain. This intermediary layer acts as a mediator that transforms raw FBG signals into compensated strain measurements by using the wavelength difference between FBGs to determine and compensate for temperature effects
2Measurement precision
If multiple Fiber Bragg Gratings are used to compensate for temperature effects, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The multiple Fiber Bragg Gratings serve dual functions: they simultaneously measure both temperature effects and mechanical strain. By disposing FBGs at different locations on the structure, each FBG contributes to both temperature compensation and strain measurement, making the sensor system multi-functional and reducing the need for separate temperature and strain sensors, thereby limiting the increase in device complexity
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 measurement of displacement and temperature, isolating mechanical strain from thermal effects, resulting in reliable and precise engineering unit measurements.
Implementation Method 1
at least first and second Fiber Bragg Gratings disposed along the fiber
Data Source
AI summary
A sensor is disclosed herein. The sensor includes a fiber operable to communicate a light wave. The sensor also includes at least first and second Fiber Bragg Gratings disposed along the fiber. The sensor also includes a structure operable to be deformed in a plane of deformation. The at least first and second Fiber Bragg Gratings are disposed on opposite sides of the structure in the plane of deformation. The sensor also includes an interrogation unit operable to receive first and second signals corresponding to first and second wavelengths from the at least first and second Fiber Bragg Gratings. The first signal is associated with the first Fiber Bragg Grating and the second signal is associated with the second Fiber Bragg Grating. The sensor also includes a processor operable to derive a difference between the wavelengths of the first and second signals and compare the difference with data correlating wavelength differences to extents of deformation of the structure to yield a current extent of deformation.