Annular Angular Rate Sensor Supports That Prevent Frequency Splitting
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Solution Overview
Problem
Vibrating structure angular rate sensors face challenges due to frequency splitting caused by geometrical non-linearity, leading to decreased sensitivity and increased noise, especially when operating at larger amplitudes, as the resonant frequencies of primary and secondary modes diverge due to the configuration of supporting legs.
Innovation Solution
The use of a combination of passive and active supporting structures allows for the selection of the total number of supporting structures such that the resonant frequencies of the primary and secondary modes remain identical, even at large amplitudes, mitigating frequency splitting and enhancing sensor sensitivity by ensuring that both modes shift by the same amount, thus maintaining measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the annular resonator is driven at larger amplitudes to improve sensitivity, then the measurement sensitivity increases, but frequency splitting occurs due to geometrical non-linearity causing the resonant frequencies of primary and secondary modes to diverge
Solution Approach 1:
The patent changes the physical parameters of the supporting structures by introducing initial stress or pre-tensioning forces. This modifies the stiffness characteristics of the supporting legs, causing the resonant frequencies of both primary and secondary modes to shift by the same amount even at large amplitudes, thereby maintaining frequency degeneracy and preventing frequency splitting while allowing operation at higher amplitudes for improved sensitivity
2Device complexity
If conventional supporting leg configurations are used, then the device complexity remains low, but frequency splitting occurs leading to decreased measurement accuracy
Solution Approach 1:
Rather than changing the basic configuration or number of supporting legs, the patent modifies the physical state parameters of the existing supporting structures by applying initial stress or pre-tensioning. This approach maintains device simplicity while achieving the goal of preventing frequency splitting and maintaining measurement accuracy through parameter modification rather than structural redesign
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 enables the production of more sensitive angular rate sensors by allowing operation at larger amplitudes without frequency splitting, reducing uncertainty in secondary mode oscillation amplitude measurements and maintaining measurement accuracy.
Implementation Method 1
When the sensor undergoes rotation about an axis perpendicular to the plane of the annular resonator, Coriolis forces are generated which couple energy into a secondary vibration mode, causing oscillation in this mode
Implementation Method 2
The annular resonator is driven into a primary mode of vibration at resonance by primary drive transducers that excite the primary vibration mode
Implementation Method 3
As the metal tracks move within the magnetic field, currents are induced in the pick-off transducers, which flow to a pick-off system via metal tracking laid on the surface of the supporting legs
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A vibrating structure angular rate sensor 400 is provided which comprises a substrate 406; a plurality of flexible supporting structures 404a, 404b fixed to the substrate 406; an annular member 402 which is flexibly supported by the plurality of supporting structures 404a, 404b to move elastically relative to the substrate 406; and an electrical drive system configured to drive the annular member 402 to oscillate in a primary mode of oscillation with a resonant frequency f1. The plurality of supporting structures 404a, 404b comprises at least one active supporting structure 404a which carries an active electrical connection from the annular member 402 to the drive system; and at least one passive supporting structure 404b which does not carry an active electrical connection from the annular member 402 to the drive system.