Precision Gyroscope Mode Matching Using Rate-Independent Calibration
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Solution Overview
Problem
Existing gyroscopes face challenges in accurately measuring the difference between resonant frequencies due to environmental variations and rate input, leading to limited precision and signal-to-noise ratio issues in mode matching.
Innovation Solution
A method for continuously monitoring the split between the resonances of the drive and sense modes using a periodic calibration signal that is independent of the rate measurement, allowing for precise tuning of resonant frequencies and eliminating interference from rate input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sinusoidal calibration signal is injected into the sense resonator to measure frequency split, then mode matching precision is improved, but the rate measurement is corrupted and the frequency split extraction becomes dependent on rate signal
Solution Approach 1:
The patent segments the measurement process by using separate resonators: a drive resonator excited at its resonant frequency and a sense resonator that detects frequency split. The calibration signal is applied only to the drive resonator, separating the calibration function from the rate measurement function and eliminating mutual interference.
Solution Approach 2:
The patent introduces an intermediary mechanism (the drive resonator) that mediates between the calibration signal and the sense resonator. The drive resonator converts the calibration signal into mechanical vibrations that couple to the sense resonator through Coriolis force, allowing indirect measurement that avoids direct injection into the sense resonator.
2Reliability
If the calibration signal frequency is placed outside the bandwidth of the rate signal, then rate measurement corruption is avoided, but the signal-to-noise ratio of calibration deteriorates
Solution Approach 1:
The patent uses mechanical vibration resonance of the drive resonator to amplify the calibration signal. By exciting the drive resonator at its resonant frequency, the system achieves high signal-to-noise ratio without requiring the calibration frequency to be outside the rate measurement bandwidth, as the resonant amplification provides sufficient signal strength.
Solution Approach 2:
The patent changes the operating parameters by utilizing the resonant frequency of the drive resonator as the calibration frequency. This parameter selection optimizes both the signal-to-noise ratio (through resonant amplification) and the compatibility with rate measurement bandwidth, resolving the trade-off between these two requirements.
3Measurement precision
If electrostatic tuning is used to adjust resonant frequency of drive or sense mode, then mode matching is achieved, but the system complexity increases
Solution Approach 1:
The patent implements self-service by using the Coriolis coupling between drive and sense resonators to automatically indicate frequency mismatch. When the resonant frequencies are matched, the sense resonator responds maximally to the Coriolis force from the drive resonator, providing a natural feedback signal that eliminates the need for complex external tuning mechanisms.
Solution Approach 2:
The patent uses feedback by monitoring the response of the sense resonator to the drive resonator's Coriolis force. This response serves as a feedback signal that indicates whether the resonant frequencies are matched, allowing for simple frequency adjustment without requiring complex electrostatic tuning systems.
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 accurate and precise mode matching by isolating the calibration signal from rate measurement, enhancing the sensitivity and accuracy of angular rate detection in gyroscopes.
Implementation Method 1
a first resonator, drive resonator, having an x-mode excited at its resonant frequency
Implementation Method 2
a second resonator, sense resonator, having a y-mode driven by receiving a Coriolis force signal from the output of said first resonator
Implementation Method 3
using further means, for instance electrostatic tuning, to adjust the resonant frequency of the drive mode or sense mode
Data Source
AI summary
A precision gyroscope which provides mode matching which is insensitive to rate input in response to continuously monitoring the split between the resonances of the drive and sense modes. A calibration signal, having at least one modulated term whose carrier is synchronous with the excitation in the drive resonator is utilized to modify the feedback signal in the sense resonator. The gyroscope thus does not suffer from corruption of, or from, the rate measurement; whereas the frequency of the calibration signal can be chosen independently of the bandwidth of the rate input.