Mooring Axial Load Monitoring via Natural Frequency Correlation
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Solution Overview
Problem
Current methods for monitoring axial loads in moorings, such as using load cells and indirect angle measurements, face issues like equipment damage, maintenance challenges, and calibration complexities due to environmental conditions and the need for extensive data collection, leading to inaccurate load calculations and high maintenance risks.
Innovation Solution
A method using a smaller calibration prototype to create a computational model that identifies natural frequencies of structures subjected to axial stress, allowing for easy calibration and load monitoring without requiring extensive data on multiple load types or temperature measurements, and enabling simple sensor installation and replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If load cells with strain gauges are used to directly measure axial loads, then measurement precision is improved, but device complexity and maintenance difficulty increase due to fragile electronic components susceptible to corrosion and damage in marine environments
Solution Approach 1:
The patent replaces electronic strain gauges with a mechanical vibration-based measurement system. Natural frequencies of the mooring line are measured using simple vibration sensors, and loads are determined through calibration curves relating frequency to axial load. This substitution eliminates fragile electronic components while maintaining measurement capability through purely mechanical/physical principles.
Solution Approach 2:
The patent employs simple, inexpensive vibration sensors that can be easily replaced if damaged, rather than expensive load cells with strain gauges. The sensors are mounted externally on the mooring line and can be quickly swapped without requiring complex installation or calibration procedures, making the system more resilient in harsh marine environments.
2Measurement precision
If load cells are installed on mooring lines, then direct load measurement is achieved, but ease of repair deteriorates because maintenance requires relieving load and accessing difficult-to-reach installation sites
Solution Approach 1:
The patent replaces the load cell system with external vibration sensors that attach to the mooring line without requiring internal installation. These sensors can be mounted and removed from accessible locations, eliminating the need to relieve load or access difficult installation sites during maintenance operations.
3Reliability
If extensive calibration data collection is performed to account for multiple load types and temperatures, then measurement reliability is improved, but loss of time and productivity decrease due to the laborious calibration process requiring separate testing of each load scenario
Solution Approach 1:
The patent extracts only the essential calibration parameter (axial load) from the complex multi-parameter calibration process. By focusing solely on the relationship between natural frequency and axial load, the system eliminates the need to separately calibrate for different load types and temperature conditions, dramatically reducing calibration time while maintaining sufficient measurement reliability for the intended application.
Solution Approach 2:
The patent creates a universal calibration curve that relates natural frequency to axial load across the full operating range, making the system adaptable to various conditions without requiring separate calibration for each scenario. The single calibration process produces a comprehensive lookup table that handles different load magnitudes and environmental conditions through one unified relationship.
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
This approach provides a reliable, efficient, and maintainable solution for monitoring axial loads in moorings by correlating natural frequencies with load values, reducing maintenance risks and improving accuracy, and eliminating the need for extensive calibration tables and complex data collection.
Implementation Method 1
The present invention refers to a method of monitoring axial loads in structures, such as moorings, by identifying their natural frequencies
Implementation Method 2
Changes in associated resonant frequencies or phases that are caused by changes in the loads and temperature of the structure are detected
Data Source
AI summary
The present invention relates to a method for monitoring axial loads in structures by identifying natural frequencies. The analyzed structures are made up of elements connected by means of contact and are subjected to tractive loads, such as mooring lines. The proposed method uses bench testing and a computer model of the structure to determine the variation in the natural frequencies in relation to the variation in load. Monitoring is carried out using vibration sensors, in particular accelerometers, laser position sensors or strain gauges, to measure the dynamic behaviour of the structure, a data capture and signal conditioning unit and a computer to correlate the load applied and the vibration behaviour using a computer algorithm, and also to present the result. The invention discloses an easy calibration method for the dimensional template of the structures in question, high accuracy and easy installation and operation in the field.