Vibrating Beam Accelerometer Common Mode Rejection
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Solution Overview
Problem
Vibrating beam accelerometer devices face limitations in accuracy due to insufficient common mode rejection, which is crucial for distinguishing acceleration from extraneous forces like temperature, radiation, and static charge, as they typically rely on only two resonator frequencies.
Innovation Solution
The implementation of multiple resonant modes using two double-ended tuning forks driven into extra resonant modes, increasing common mode rejection from two to four modes, and employing additional oscillators to enhance the scale factor for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only two resonator frequencies are used in conventional VBA devices, then the device complexity is reduced, but the measurement precision deteriorates due to insufficient common mode rejection
Solution Approach 1:
The invention segments the common mode rejection function by using multiple independent resonant modes (first mode, second mode, third mode, and fourth mode) instead of relying on a single two-frequency differential measurement. Each resonant mode provides an independent measurement channel that contributes to rejecting common mode errors, thereby improving acceleration measurement accuracy through divided functional segments.
Solution Approach 2:
The invention transitions from a two-dimensional measurement space (two frequencies) to a four-dimensional measurement space by utilizing four distinct resonant modes. This dimensional expansion allows for more comprehensive common mode rejection by measuring acceleration through multiple independent frequency channels, effectively adding measurement dimensions to improve precision.
2Measurement precision
If additional oscillators are used to drive DETFs into extra resonant modes, then the scale factor is enhanced, but the device complexity increases
Solution Approach 1:
The additional oscillators serve multiple functions: they drive the DETFs into higher resonant modes for enhanced scale factor, enable common mode rejection across four modes, and provide redundant measurement channels. This multi-functionality justifies the increased device complexity by delivering comprehensive measurement capabilities and improved accuracy through a single integrated system.
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 significantly enhances common mode rejection, providing more accurate force and acceleration measurements by effectively canceling out non-acceleration errors such as temperature, radiation, and static charge influences.
Implementation Method 1
The DETFs 36, 38 are designed to resonant at different frequencies. The DETFs 36, 38 are driven at two different resonant modes (e.g., mode 1 and mode 3), thereby producing output signals in the two resonant modes but at slightly different frequencies
Data Source
AI summary
Systems and methods for improving common mode cancelation in a vibrating beam accelerometer (VBA) by using multiple resonant modes. The VBA includes two double-ended tuning forks (DETF). Additional oscillators drive the DETFs into the extra resonant modes. This increases common mode rejection from two modes to four modes. In addition the scale factor of the additional mode may provide a greater scale factor than prior designs.