Resonant Device Frequency Analysis Using Hilbert Transform Demodulation
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Solution Overview
Problem
Resonant frequency measurement in vibrating devices like accelerometers is hindered by nonlinear relationships and parasitic vibrations, leading to bias and scale factor errors that cannot be compensated due to the random nature of vibrations, especially at resonance frequencies.
Innovation Solution
A system implementing broadband demodulation algorithms using Hilbert transforms and derivative calculations to separate low-frequency acceleration signals from parasitic vibrations, ensuring accurate measurement by analyzing the instantaneous amplitude and frequency of the sensor output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resonant frequency measurement is used to determine acceleration, then measurement capability is provided, but parasitic vibrations at resonance frequency cause bias and scale factor errors that cannot be compensated
Solution Approach 1:
The patent segments the acceleration signal into two distinct frequency components: low-frequency useful acceleration signals (0-400 Hz) and high-frequency parasitic vibrations (3-5 kHz resonance frequency). By separating these components through frequency-domain analysis, the system can process each independently to eliminate interference.
Solution Approach 2:
The patent applies excessive filtering action by using both band-pass filtering (to isolate the resonance frequency component) and low-pass filtering (to extract only the low-frequency acceleration component). This multi-stage filtering approach ensures complete elimination of parasitic vibrations even at the cost of additional processing steps.
2Measurement precision
If the mass-spring system operates at resonance frequency for sensitive measurement, then measurement sensitivity is improved, but noise is strongly amplified causing degradation of measurement results
Solution Approach 1:
The patent extracts the parasitic vibration component from the total signal by using band-pass filtering centered at the resonance frequency. This isolated vibration component is then subtracted from the original signal, effectively removing the harmful noise amplification while preserving the useful low-frequency acceleration information.
Solution Approach 2:
The patent introduces an intermediary processing stage that calculates the vibration component as a separate intermediate result. This intermediary representation of parasitic vibrations serves as a mediator that can be independently analyzed and removed before final acceleration calculation, preventing direct contamination of the measurement.
3Measurement precision
If broadband demodulation algorithms are implemented to separate signals from noise, then measurement accuracy is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical vibration isolation systems with electronic/digital signal processing methods. Instead of physically isolating the sensor from vibrations, the system uses digital filtering and demodulation algorithms to separate and remove vibration components computationally, simplifying the physical system while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the processing approach from time-domain analysis to frequency-domain analysis by applying Fourier transforms and operating with frequency-specific filters. This parameter change in the domain of signal representation enables effective separation of acceleration and vibration components that are mixed in the time domain.
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 effectively eliminates scale and bias errors by isolating low-frequency signals from high-frequency noise, allowing for precise acceleration measurement even under conditions of random vibrations.
Implementation Method 1
A system implementing broadband demodulation algorithms using Hilbert transforms and derivative calculations
Implementation Method 2
the frequency of the oscillations of an oscillating mechanical system either in free oscillations, or in forced oscillations, this frequency depending on the parameter that one seeks to measure
Implementation Method 3
The current passes through a charge amplifier filter. The voltage at the output of this filter constitutes the output signal of the sensor
Data Source
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AI summary
The system has a measurement unit for measuring a position of a vibrating device along an axis and providing a signal representative of the position. The measurement unit calculates a function representative of square of resonance pulse of the vibrating device, where the calculated function includes parameters such as instantaneous pulse, instantaneous amplitude and second derivative of the amplitude.