Fiber Optic Bearing Load Measurement Beyond Nyquist Limits
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Solution Overview
Problem
Existing optical sensing systems for bearings are limited by the Nyquist sampling criterion, restricting the maximum rotating speed to 1250 Hz, which hinders accurate load measurement at higher frequencies.
Innovation Solution
A method and device using a fiber optic sensor with optical strain gauges and random sampling to measure deformations, determining load through statistical parameters beyond the Nyquist frequency, allowing for load determination at higher rotational frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Nyquist sampling criterion is applied to measure bearing deformations, then measurement accuracy is improved, but maximum rotating speed is limited to 1250 Hz
Solution Approach 1:
The patent changes the sampling strategy from periodic (Nyquist) sampling to random sampling, fundamentally altering the temporal parameter of measurement. This allows the system to capture sufficient statistical information about deformations without being constrained by the Nyquist frequency limit, enabling accurate load measurement at rotating speeds exceeding 1250 Hz
Solution Approach 2:
The patent replaces the traditional mechanical approach of high-frequency periodic sampling with a statistical method using random sampling. By substituting deterministic periodic measurement with probabilistic random sampling and statistical analysis, the system overcomes the hardware sampling frequency limitation while maintaining measurement accuracy
2Device complexity
If optical interrogator sampling frequency is kept low (2500 Hz), then device complexity is reduced, but measurement signals above 1250 Hz cannot be captured
Solution Approach 1:
The patent introduces statistical parameters as an intermediary between the low-frequency random samples and the high-frequency deformation information. By computing statistical characteristics (mean, variance, higher-order moments) of the randomly sampled data, the system recovers high-frequency load information without requiring high-speed sampling hardware
Solution Approach 2:
The patent transitions from the time domain to the statistical domain by analyzing higher-order moments of the deformation distribution. This dimensional transformation allows extraction of high-frequency signal characteristics from low-frequency random samples, effectively bypassing the Nyquist sampling limitation
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 load measurement on bearings rotating beyond 1250 Hz by decoupling sample values from machine rotation speed, overcoming the limitations of conventional optical interrogators.
Implementation Method 1
each optical strain gauge includes a different set of refraction gratings
Implementation Method 2
an optic fiber surrounding the outer ring of the bearing. The optical interrogator emits a laser signal into the optic fiber, and receives a reflected signal corresponding to the deformation of the outer ring
Data Source
AI summary
A bearing device includes a bearing having an inner ring and an outer ring, at least one of the inner and outer rings being capable of rotating concentrically relative to the other ring. A fiber optic sensor includes an array of optical strain gauges mounted on the inner ring or on the outer ring of the bearing and an optical interrogator is configured to measure the deformations of the inner ring or the outer ring from the optical strain gauges. A command device commands the optical interrogator, a first determining device determines a statistical parameter from random samples of measurements, and a second determining device determines the load acting on the bearing from the statistical parameter and a predetermined relationship between the statistical parameter and the load.