Dual-Mode MEMS Gyroscope Readout for High Range and Resolution
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Solution Overview
Problem
Gyroscopes face a trade-off between high dynamic range and rate resolution, where high angular rate measurement capabilities come at the cost of reduced resolution, and high-resolution measurements have limited range, making them inadequate for applications requiring both.
Innovation Solution
A Coriolis vibratory gyroscope with a dual-mode readout system, comprising a coarse readout circuit for initial angular rate measurement and a fine readout circuit that adjusts drive frequencies and natural frequencies to derive a high-resolution difference, allowing for both high range and fine resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gyro is designed to operate at high angular rates, then the range is improved, but the resolution deteriorates
Solution Approach 1:
The measurement system is segmented into two independent measurement paths: a first measurement path using a first pair of modes for coarse measurement of high angular rates, and a second measurement path using a second pair of modes for fine measurement of low angular rates. Each path is optimized for its specific range, and the results are combined to achieve both high range and high resolution simultaneously.
Solution Approach 2:
The patent transitions from a single-dimensional measurement approach to a two-dimensional measurement space by utilizing two distinct pairs of modes with different measurement characteristics. The first pair of modes provides coarse measurement capability for high rates, while the second pair provides fine measurement capability for low rates, creating a multi-dimensional measurement system that overcomes the traditional trade-off.
2Measurement precision
If the resolution of the ADC is increased, then the rate resolution is improved, but the device complexity increases
Solution Approach 1:
The measurement task is segmented between two mode pairs, allowing each ADC to operate at moderate resolution (e.g., 19 bits) rather than requiring a single ADC to handle the full dynamic range at high resolution. The coarse measurement from the first mode pair and fine measurement from the second mode pair are combined through digital processing to achieve the final high-resolution output.
Solution Approach 2:
Digital signal processing acts as an intermediary that combines the coarse measurement from the first mode pair and the fine measurement from the second mode pair. This digital processing merges the two measurements to produce the final high-resolution angular rate output, avoiding the need for extremely high-resolution ADC hardware.
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
The dual-mode system achieves a high dynamic range with 19-bit resolution, enabling accurate guidance in maneuverable aircraft and missiles by effectively combining coarse and fine measurements.
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
Data Source
AI summary
A sensor includes an acceleration or magnetic field sensitive microelectromechanical systems (MEMS) resonator, configured to oscillate in at least a first normal mode and a second normal mode. The sensor further includes: a coarse readout circuit configured to drive the first normal mode, measure a motion of the first normal mode, and derive from the measured motion a coarse measurement of the true acceleration or true external magnetic field; and a fine readout circuit configured to drive the second normal mode, measure a motion of the second normal mode, and derive from the measured motion and the coarse measurement a measurement of the difference between the true acceleration or true external magnetic field and the coarse measurement.