Self-Tensed Optical Fiber Spring for Strain Sensing
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Solution Overview
Problem
Conventional fiber grating sensors face challenges such as complex and costly tensing processes, fragility due to lack of standardized protection, and susceptibility to breakage from external forces, which hinder their standardization and accuracy in strain measurement.
Innovation Solution
An optical fiber sensing spring structure is developed, comprising cylindrical tension and compression coil springs that protect and tense a fiber grating, allowing for precise strain measurement within an elastic limit, using the elastic properties of springs to achieve accurate strain detection and protection against external forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional fiber grating sensors are used without standardized protection, then manufacturing is simpler, but the sensors become fragile and susceptible to breakage from external forces
Solution Approach 1:
The fiber grating sensor is nested within a protective tube structure that provides standardized protection. The sensor is placed inside the tube, which acts as an outer shell, creating a nested configuration that protects the fragile sensor while maintaining a compact integrated structure.
Solution Approach 2:
The protective tube is pre-assembled with the fiber grating sensor before deployment. The sensor is positioned within the tube during manufacturing, providing predetermined protection against external forces before the sensor is installed in its final application location.
2Measurement precision
If fiber grating sensors are tensed to achieve accurate strain measurement, then measurement precision improves, but the tensing process becomes complex and costly
Solution Approach 1:
The fiber grating sensor performs self-tensing through its integration with the protective tube structure. The sensor is pre-stretched during assembly within the tube, eliminating the need for separate complex tensing equipment and processes. The structure itself provides the necessary tensioning force.
Solution Approach 2:
The tensing function is merged with the protective tube structure. The tube serves dual purposes: providing mechanical protection and simultaneously applying the necessary tension to the fiber grating sensor for accurate strain measurement, combining two functions into one integrated component.
3Measurement precision
If multiple sensing devices are used for temperature compensation, then temperature accuracy improves, but device complexity and cost increase
Solution Approach 1:
The protective tube structure serves multiple functions simultaneously: it provides mechanical protection for the sensor, acts as a structural element, and enables temperature compensation through its interaction with the fiber grating sensor. This multi-functionality eliminates the need for separate dedicated temperature compensation devices.
Solution Approach 2:
Temperature compensation functionality is merged into the protective tube-sensor integrated structure. The tube and sensor work together as a unified system that inherently provides temperature compensation, combining protection and temperature sensing functions into one integrated solution rather than requiring separate devices.
4Strength
If fiber grating sensors are coated with resin for protection, then strength against external forces improves, but manufacturing precision requirements increase
Solution Approach 1:
The fiber grating sensor is nested within a pre-formed protective tube structure rather than being coated with resin. This nested configuration provides protection through the tube wall structure, eliminating the need for precise resin coating applications and reducing manufacturing precision requirements.
Solution Approach 2:
The protective tube structure serves as a disposable or replaceable outer shell that provides protection without requiring precise manufacturing tolerances. The tube can be manufactured with standard tolerances and still provide adequate protection, making the overall system more manufacturable.
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 optical fiber sensing spring provides a standardized, cost-effective, and accurate means of strain measurement, with enhanced protection and simplified manufacturing, capable of withstanding external forces and temperature variations, while maintaining high precision and durability.
Implementation Method 1
In an FBG, the optical fiber is exposed by using a coherent laser, such that the index of refraction of the core of the illuminated section of the optical fiber is permanently changed, and that section of index of refraction of the optical fiber, also referred to as a fiber grating or an FBG, has bright and dark periodical striped intervals
Implementation Method 2
the index of refraction of the core of the illuminated section of the optical fiber is permanently changed
Implementation Method 3
cylindrical tension and compression coil springs that protect and tense a fiber grating, allowing for precise strain measurement within an elastic limit, using the elastic properties of springs
Data Source
AI summary
An optical fiber sensing spring of the present invention includes a longer cylindrical tension coil spring, a shorter cylindrical compression coil spring and a longer cylindrical tension coil spring that are connected in series to form a spring having the same inner and outer diameters. A single-mode optical fiber manufactured with a long section of fiber grating is placed in the manufactured spring. This section of the fiber grating is tensed to two ends of the cylindrical compression coil spring having a predetermined gauge length, and the force applied is released. A pre-tensing method for providing a maximum tolerable compression strain and manufacturing technology for this sensing element are then achieved. Thus, the self-tensed optical fiber sensing spring structure satisfies a standard 0.9 mm outer diameter, is fully spring jacketed by the full spring jacketing and protection layer, and forms a linear stress-strain relationship in an elasticity stretched elastic region.