Sensor-Equipped Lug With FBG Sensors for Load Vector Measurement
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Solution Overview
Problem
Existing systems for measuring tensile stress in lugs, such as those used in floating offshore wind energy, lack accuracy in determining both the magnitude and direction of the load, and are not easily adaptable to existing structures without altering their strength.
Innovation Solution
Attaching optical fibre wires equipped with Fiber Bragg Grating (FBG) stress sensors to the lug edge allows for precise measurement of tensile stress, angle of pull, and off-centre angle by correlating sensor readings with calibration data, using methods like Finite Element Method (FEM) for installation and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If instrumented shackles are connected to the lugs to measure load, then the load can be measured, but no information about the direction of the load is provided
Solution Approach 1:
The patent replaces mechanical measurement devices (instrumented shackles) with an optical sensing system. Optical fibre wires with FBG sensors are attached to the lug, substituting mechanical load cells with optical interrogation systems that can detect both magnitude and direction of forces through wavelength shifts in the optical fibres.
Solution Approach 2:
The patent transitions from one-dimensional measurement (load magnitude only via shackles) to multi-dimensional measurement by arranging optical fibres in specific geometric patterns on the lug surface. This spatial arrangement enables detection of force vectors in multiple directions simultaneously, adding directional information to the measurement capability.
2Measurement precision
If direct measurement systems are installed on the lugs, then accurate load measurement is achieved, but the lug structure must be altered which affects its strength
Solution Approach 1:
The patent uses thin optical fibre wires as sensing elements that can be surface-mounted on the lug without penetrating or significantly altering the structural material. These flexible, thin-film sensors conform to the lug surface and provide measurement capability while maintaining the original structural integrity and strength characteristics of the lug.
Solution Approach 2:
The patent introduces adhesive layers and protective coatings as intermediary elements between the optical fibre sensors and the lug structure. These intermediaries enable sensor attachment and environmental protection without requiring direct structural modification that would compromise lug strength, allowing the sensors to measure strain through the adhesive bond.
3Adaptability or versatility
If measurement systems are added to existing lugs, then load measurement capability is provided, but the system becomes more complex
Solution Approach 1:
The patent creates a universal measurement platform where optical fibre sensors can be applied to various lug types and configurations using standardized attachment procedures. The same basic sensor arrangement and interrogation system can measure different parameters (force, strain, temperature) on different structures, reducing overall system complexity through multi-functionality.
Solution Approach 2:
The patent uses optical fibre copies or replicas that can be attached to the lug surface without modifying the original structure. The optical fibres act as informational copies of the structural behavior, sensing strain and force through adhesive bonding while the original lug remains unchanged, simplifying the measurement implementation.
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 direct, accurate, and economical measurement of load magnitude and direction on lugs, suitable for both centred and off-centred pulls, without altering the lug's structural integrity, and can be installed on existing structures during construction.
Implementation Method 1
attaching one or two optical fibre wires equipped with Fiber Bragg Grating (FBG) stress sensors to the lug
Data Source
Figure 1~2
Figure 3a~4
Figure 5
AI summary
The present invention discloses a sensor-equipped lug (1) for measuring tensile force comprising at least one optical fibre wire (2) equipped with a plurality of individual FBG stress sensors (21) attached along the edge (12). The invention also discloses a method for determining the quantity (T), the angle of pull (α) and the angle of off-centre (θ) from the stresses obtained by said sensor-equipped lug (1). Finally, a method of manufacturing such a sensor-equipped lug (1) is disclosed.