CVG Readout Architecture for High-Range, Fine-Resolution Gyroscopes
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Solution Overview
Problem
Gyroscopes face a trade-off between high dynamic range and rate resolution, limiting their ability to accurately measure both high angular rates and small changes in angular rates, which is crucial for applications like aircraft and missile guidance.
Innovation Solution
A high dynamic range gyroscope design incorporating a Coriolis vibratory gyroscope with a coarse readout circuit and a fine readout circuit, where the fine readout circuit adjusts drive frequencies and natural frequencies to derive a precise measurement of angular rate differences, achieving a resolution of 19 bits and a range of ±0.0017 degrees per second.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gyroscope is designed to operate at high angular rates, then the range is improved, but the resolution deteriorates
Solution Approach 1:
The gyroscope system is segmented into two independent measurement paths: a first pair of modes (e.g., n=2 modes) for coarse measurement of high angular rates, and a second pair of modes (e.g., n=3 modes) for fine measurement of small angular rate changes. Each pair of modes is driven and measured separately by dedicated readout circuits, allowing each subsystem to be optimized for its specific measurement range without compromising the other.
Solution Approach 2:
The patent transitions from a single-dimensional measurement approach to a multi-dimensional approach by utilizing multiple normal modes with different mode numbers (e.g., n=2 and n=3 modes). Each mode number represents a different dimensional characteristic of the resonator's vibration pattern, enabling simultaneous access to both high-range and high-resolution measurement capabilities through dimensional diversification.
2Measurement precision
If the resolution of the ADC is increased to improve rate resolution, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The measurement task is segmented into coarse and fine components, each handled by separate readout circuits measuring different mode pairs. The coarse readout circuit handles the bulk of the dynamic range with moderate resolution requirements, while the fine readout circuit focuses on small deviations with higher effective resolution. This segmentation eliminates the need for a single ultra-high-resolution ADC that would be required to handle the entire dynamic range at once.
Solution Approach 2:
Instead of using a single ADC with excessive resolution to cover the entire measurement range, the system applies partial action by using two ADCs with moderate resolution, each dedicated to a specific measurement subset. The coarse ADC handles the majority of the range, and the fine ADC handles the residual precision requirements, avoiding the complexity and cost of a single ADC with extremely high resolution.
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 design enables the gyroscope to provide both high range and fine resolution, effectively addressing the limitations of existing gyroscopes by allowing accurate measurement of both high angular rates and small changes, enhancing guidance systems' precision.
Implementation Method 1
a Coriolis vibratory gyroscope (CVG) resonator, configured to oscillate in: a first pair of normal modes including a first normal mode and a second normal mode; and a second pair of normal modes including a third normal mode and a fourth normal mode
Data Source
AI summary
An angular sensor. The angular sensor includes a Coriolis vibratory gyroscope (CVG) resonator, configured to oscillate in a first pair of normal modes including a first normal mode and a second normal mode and a second pair of normal modes including a third normal mode and a fourth normal mode. The angular sensor further includes a coarse readout circuit configured to drive the first pair of modes, measure the motion of the first pair of modes, and derive from the measured motion of the first pair of modes a coarse measurement of an angular rate of the resonator. The angular sensor further includes and a fine readout circuit configured to derive a measurement of the difference between the true angular rate of the resonator and the coarse measurement.