Resonantly Vibrating Accelerometer with Dual-Mode Sensors
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Solution Overview
Problem
Conventional accelerometers face challenges in accurately measuring acceleration due to noise interference and sensitivity to environmental factors, particularly with the revelation of cross-coupling spectral features at difference frequencies, which were previously obscured by high noise floors.
Innovation Solution
The design incorporates two substantially identical vibrating sensors with distinct resonant mode frequencies, connected to a proof mass that applies opposite loads, generating difference frequencies that vary monotonically with acceleration, and employs low-pass filters with cut-off frequencies below the difference frequency to reduce noise and enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional accelerometers measure acceleration directly, then measurement speed is maintained, but noise interference and environmental sensitivity increase measurement error
Solution Approach 1:
The patent employs resonantly vibrating sensors that operate at their natural resonant frequency to measure acceleration. By driving the sensors at resonance, the system achieves enhanced sensitivity to acceleration while the resonant operation inherently provides immunity to certain noise sources. The vibrating sensors convert acceleration inputs into frequency shifts that can be measured with high precision, resolving the contradiction between measurement speed and accuracy under noisy conditions.
Solution Approach 2:
The patent replaces direct mechanical acceleration measurement with a frequency-based measurement system. Instead of measuring acceleration directly through mechanical means, the system uses resonant frequency shifts of vibrating sensors as a proxy for acceleration. This substitution of mechanical measurement with frequency domain measurement enables high-precision acceleration sensing that is less susceptible to noise and environmental factors.
2Measurement precision
If low-pass filters with low cut-off frequencies are used to reduce noise, then measurement accuracy improves, but measurement speed decreases
Solution Approach 1:
By operating the sensors at their resonant frequency, the system achieves maximum sensitivity while maintaining a narrow bandwidth naturally. This resonant operation allows the use of higher cut-off frequencies in the low-pass filter without sacrificing noise rejection, because the signal energy is concentrated at the known resonant frequency. Thus, the system can use less aggressive filtering that preserves measurement speed while still achieving excellent noise reduction.
Solution Approach 2:
The system continuously monitors the resonant frequency of the vibrating sensors and uses this information to maintain optimal operation. By tracking the frequency shifts caused by acceleration and actively maintaining resonant operation, the system can use feedback control to preserve measurement speed while achieving high precision through frequency-locked detection rather than relying solely on aggressive time-domain filtering.
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 improves the accuracy of acceleration measurement by reducing noise and minimizing the influence of environmental factors, while maintaining a suitable balance between noise reduction and measurement speed.
Implementation Method 1
Each vibrating sensor exhibits a corresponding set of fundamental and higher-order vibrational modes, each characterized by a corresponding fundamental or higher-order resonant mode frequency
Implementation Method 2
The first 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 3
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 and a pair of vibrating sensors. An excitation-and-detection circuit drives one sensor at resonant frequencies f1 and F1, with f1≠F1; a second excitation-and-detection circuit drives the other sensor at resonant frequencies f2 and F2, with f2≠F2. The vibrational modes driven at the frequencies f1 and f2 are the same for each sensor; 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 a sensing axis, from which a measurement of acceleration can be generated.