Resonant Accelerometer Cross-Coupling Suppression
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Solution Overview
Problem
Conventional accelerometers face challenges in accurately measuring acceleration due to cross-coupling spectral features at the difference frequency, which are obscured by noise, and require improved filtering to reduce interference and enhance measurement accuracy.
Innovation Solution
The design incorporates two substantially identical vibrating sensors with distinct resonant mode frequencies, driven by an excitation-and-detection circuit to produce a difference frequency that varies monotonically with acceleration, using a low-pass filter with a cut-off frequency less than the difference frequency to reduce noise and isolate the acceleration signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional filtering is used to remove cross-coupling spectral features, then measurement accuracy is improved, but the filter cut-off frequency must be set below the difference frequency which limits the measurement bandwidth
Solution Approach 1:
The patent changes the operating parameters by driving the vibrating sensors at different resonant frequencies (f1 and f2) such that their difference frequency Δf is sufficiently large. This allows the low-pass filter cut-off frequency fLP to be set above 100 Hz while still being below Δf, thereby resolving the contradiction between measurement accuracy and bandwidth by optimizing the frequency separation parameter.
2Measurement precision
If the difference frequency between resonant modes is increased to improve signal separation, then filtering effectiveness is improved, but the choice of resonant modes becomes more restricted
Solution Approach 1:
The patent systematically varies the operating parameters by selecting different resonant modes (fundamental, third-order, fifth-order) and adjusting their frequency separation to achieve optimal difference frequencies. This approach maintains adaptability while improving signal-to-noise ratio, as the system can choose from multiple mode combinations depending on the specific application requirements.
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 enhances the accuracy of acceleration measurement by filtering out cross-coupling spectral features, improving the signal-to-noise ratio and reducing the influence of environmental perturbations, while maintaining a suitable balance between noise reduction and measurement speed.
Implementation Method 1
Each vibrating sensor exhibits a corresponding fundamental and higher-order vibrational modes, each characterized by a corresponding fundamental or higher-order resonant mode frequency. The excitation-and-detection circuit drives the first vibrating sensor at a selected resonant mode frequency f1, drives the second vibrating sensor at a selected resonant mode frequency f2
Implementation Method 2
The output signal is filtered by at least one low-pass filter characterized by a low-pass cut-off frequency fLP that is less than Δf. This approach enhances the accuracy of acceleration measurement by filtering out cross-coupling spectral features
Implementation Method 3
The proof mass is connected to the vibrating sensors so that acceleration in one direction along a sensing axis causes the proof mass to apply a tensile load to the first vibrating sensor and a compressive load to the second vibrating sensor
Data Source
AI summary
An inventive accelerometer includes a proof mass, vibrating sensors, and an excitation-and-detection circuit. The vibrating sensors are substantially identical, and each exhibits corresponding fundamental and higher-order vibrational modes characterized by corresponding fundamental and higher-order resonant mode frequencies. The excitation-and-detection circuit drives each corresponding vibrating sensor at one of its resonant mode frequencies f1 or f2; the vibrational modes driven at the frequencies f1 and f2 are the same for each sensor. Compressive or tensile loads oppositely applied by the proof mass to the vibrating sensors cause a difference frequency Δf=f1−f2 to vary monotonically with acceleration of the apparatus along the sensing axis. The excitation-and-detection circuit includes at least one low-pass filter with a low-pass cut-off frequency fLP that is less than Δf.