Bragg Grating Fibre Sensing for Dynamic Deformation
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Solution Overview
Problem
Existing measuring systems using optical fibers with Bragg gratings cannot distinguish between static and dynamic deformations of an object, limiting their effectiveness in assessing the lifespan of dynamically deformable components like helicopter rotor blades.
Innovation Solution
A measuring system incorporating an optical fiber with a mobile measuring sector inside a tube filled with a non-Newtonian fluid, where the sector comprises Bragg gratings, and the fluid's viscosity changes with mechanical stress to differentiate between static and dynamic deformations by altering the reflected light wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional optical fiber with Bragg grating is used to measure deformation, then the system can measure total deformation, but it cannot distinguish between static and dynamic deformation components
Solution Approach 1:
The measurement system is segmented into two independent functional components: a first optical fiber with Bragg grating for measuring total deformation, and a second optical fiber with Bragg grating for measuring temperature. This segmentation allows the system to separately capture deformation and temperature data, enabling the distinction between static and dynamic deformation components through signal processing.
Solution Approach 2:
Temperature measurement acts as an intermediary parameter that helps distinguish between static and dynamic deformation. By measuring temperature separately with the second optical fiber, the system can compensate for thermal effects and isolate the dynamic deformation component from the total deformation signal.
2Reliability
If temperature compensation is implemented using another Bragg grating or thermocouple, then temperature effects can be accounted for, but the system still cannot measure dynamic deformation specifically
Solution Approach 1:
The system uses two separate optical fibers with Bragg gratings, each dedicated to a specific measurement function. The first fiber measures total deformation while the second fiber measures temperature. This segmentation ensures that temperature compensation does not compromise the deformation measurement capability, and both functions operate independently with high precision.
Solution Approach 2:
The system changes the measurement parameter from a single deformation measurement to two separate measurements (deformation and temperature). By monitoring both parameters simultaneously using identical Bragg grating technology, the system can process the data to extract dynamic deformation information while maintaining temperature compensation reliability.
3Measurement precision
If the optical fiber is rigidly attached to the object, then the fiber deforms with the object, but the system cannot differentiate between static and dynamic deformation components
Solution Approach 1:
The measurement system is divided into two independent measurement channels using separate optical fibers. Both fibers are rigidly attached to the object to ensure accurate deformation transfer, but the segmented architecture allows independent processing of the signals to differentiate between static and dynamic components through comparative analysis.
Solution Approach 2:
The system uses feedback from the temperature measurement to process and interpret the deformation measurement. By continuously monitoring temperature and using it as feedback in the signal processing, the system can distinguish between static and dynamic deformation components while maintaining accurate deformation transfer through rigid attachment.
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 precise measurement of dynamic deformations by detecting changes in the optical fiber's wavelength due to increased fluid viscosity during dynamic events, allowing for accurate assessment of components like helicopter rotor blades.
Implementation Method 1
Each Bragg grating allows only a portion of the light with a particular wavelength to be reflected. The wavelength of this reflected light depends on the product of the Bragg grating pitch and the refractive index of the optical fiber core.
Implementation Method 2
A non-Newtonian fluid filling at least one chamber delimited by the tube, the measuring sector extending into said at least one chamber, the non-Newtonian fluid being in contact with the tube and the measuring sector.
Data Source
Figure 1~4
AI summary
The present invention relates to a measurement system (1) for measuring the dynamic deformation of an object (96), the measurement system (1) comprising an optical fiber (10), the optical fiber (10) extending at least partially within a tube (30) configured to be fixed to said object (96), the optical fiber (10) having a movable measurement sector (14) inside the tube (30), the measurement sector (14) comprising at least one Bragg grating (15). The measurement system (1) comprises a non-Newtonian fluid (40) filling at least one chamber (50) delimited by the tube (30), the measurement sector (14) extending within said at least one chamber (50), the non-Newtonian fluid (40) being in contact with the tube (30) and the measurement sector (14).