Aircraft Engine Speed Monitoring via Spectrogram Denoising
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Solution Overview
Problem
Existing methods for monitoring the operating state of aircraft engines using vibratory signals face challenges due to high-speed operations, harmonic interference, asynchronous operating modes, and low signal-to-noise ratios, making it difficult to accurately discriminate the harmonic content of interest from noise.
Innovation Solution
A method that involves constructing a raw spectrogram from a vibratory signal, denoising it to obtain an equalised spectrogram, separating sources to determine an estimator of the frequencies of interest, and calculating the instantaneous speed of rotation of the engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed operation is achieved, then engine power and productivity are improved, but harmonic interference increases and masks frequencies of interest
Solution Approach 1:
The patent extracts and removes harmful harmonic components from the vibratory signal through spectral analysis and filtering techniques. By identifying and eliminating specific frequency components that cause interference, the method isolates the useful signal from the harmful harmonics generated during high-speed operation.
Solution Approach 2:
The patent changes the operational parameters of signal processing by adjusting filtering thresholds, spectral resolution, and analysis windows to adapt to varying engine speeds. This allows the system to maintain effective harmonic rejection across different operating conditions while preserving the frequencies of interest.
2Measurement precision
If speed sensors are installed to measure rotation, then engine speed monitoring is improved, but device complexity and installation difficulty increase
Solution Approach 1:
The patent enables the engine system to monitor its own speed using existing vibratory sensors and signal processing algorithms, without requiring external speed sensors. The system extracts speed information from the natural vibrations of the engine components, making the monitoring self-sufficient and eliminating additional hardware.
Solution Approach 2:
The patent replaces mechanical speed sensors with a signal processing-based measurement system. By using spectral analysis of vibratory signals, the method substitutes physical sensing devices with computational techniques that extract speed information from the engine's natural vibrations.
3Reliability
If vibration sensors are used to monitor engine operation, then monitoring capability is improved, but signal-to-noise ratio decreases due to multiple noise sources
Solution Approach 1:
The patent extracts the useful vibratory signal from the noisy background by using spectral analysis to identify and isolate frequency components associated with engine operation. Through filtering and signal processing, the method separates the meaningful information from the broadband noise generated by combustion, aerodynamic flow, and resonance.
Solution Approach 2:
The patent employs a composite signal processing approach that combines multiple analysis techniques including spectral analysis, filtering, and pattern recognition. This composite methodology enhances the signal-to-noise ratio by integrating different processing strategies to extract weak signals from noisy environments.
Data Source
AI summary
A method for monitoring the engine speed of a rotating machine, includes constructing a raw spectrogram from a vibratory signal; denoising the spectrogram to obtain an equalised spectrogram, the denoising including a first sub-procedure of determining a foot of the spectrogram, the foot of the spectrum being a set of random harmonic components contained in the raw spectrogram, the first sub-procedure including a first sub-sub-procedure of constructing a regression function robust to the peaks of the spectrogram, the regression function being applied to a logarithm of the spectrogram or to the spectrogram; a second sub-sub-procedure of determining the foot of the spectrum from the regression function; a second sub-procedure of determining the equalised spectrogram from the foot of the spectrogram; separating sources in the equalised spectrogram by determining an estimator of the frequencies of interest; determining an instantaneous speed of rotation of the engine speed from the estimator.