Single Proof-Mass Dual-Axis Gyroscope Mode Matching
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Solution Overview
Problem
Current vibratory gyroscopes require separate proof masses for each axis' rate measurement, leading to increased size and mass, and there is a need for solutions that do not rely on separate proof masses to achieve smaller and lighter designs.
Innovation Solution
A high-frequency single proof-mass dual-axis gyroscope is designed using a hollow-disk pitch-and-roll gyroscope with mode-matched in-plane and out-of-plane resonance modes, enabled by control electrodes for electrostatic frequency tuning, and fabricated using a modified HARPSS process, which allows for a single-chip tri-axial implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate proof masses are used for each axis' rate measurement, then measurement precision is improved, but device mass increases
Solution Approach 1:
The patent combines multiple proof mass functions into a single integrated proof mass structure that can sense rotation rates along multiple axes simultaneously. This single proof mass is designed with specific geometric features and coupling mechanisms that enable it to perform the functions of what would traditionally require separate proof masses for each axis, thereby reducing overall device mass while maintaining measurement precision.
Solution Approach 2:
The single proof mass is designed as a multi-functional element that can detect rotation rates along different axes through its interaction with multiple sets of comb drive electrodes. The proof mass structure incorporates features that allow it to respond to rotational motions in multiple directions, making it a universal sensing element that replaces multiple specialized components.
2Measurement precision
If separate proof masses are used for each axis' rate measurement, then measurement precision is improved, but device size increases
Solution Approach 1:
The patent merges multiple proof mass structures into a single integrated component that occupies less volume than multiple separate proof masses would require. The single proof mass is strategically positioned and dimensioned to interact with electrode structures for multiple axes within a compact footprint, reducing the overall device volume while maintaining the measurement capabilities.
Solution Approach 2:
The patent utilizes three-dimensional positioning and orientation of the single proof mass relative to multiple sets of electrodes arranged in different spatial dimensions. By exploiting vertical and lateral spacing between electrode pairs, the design achieves multi-axis sensing capability within a compact volume, effectively using dimensional arrangement to pack multiple sensing functions into a single structure.
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 solution achieves high sensitivity and quality factors, reducing Brownian noise and enabling high-resolution dual-axis pitch and roll rate sensing with reduced size and mass, while maintaining operational bandwidth and frequency tunability.
Implementation Method 1
a resonating body member having a top surface and a side surface. The top surface of the resonating body member is separated from the first electrode by a first vertical capacitive air gap and the side surface of the resonating body member is separated from the first electrode by a first lateral capacitive air gap
Implementation Method 2
control electrodes that enable electrostatic frequency tuning of the in-plane and out-of-plane resonance modes to achieve mode-matching
Implementation Method 3
operates under mode-matched condition with a combination of in-plane and out-of-plane resonance modes of an annulus structure which occur at approximately 900 kHz
Data Source
AI summary
A single proof-mass, dual-axis gyroscope apparatus comprises a resonating body member and first and second electrodes each capacitively coupled to the resonating body member by a respective lateral capacitive air gap and a vertical capacitive air gap. The width of one of the lateral capacitive air gap of the first electrode is substantially smaller than the vertical capacitive air gap. The width of one of the vertical capacitive air gap of the second electrode is substantially smaller than the lateral capacitive air gap. The apparatus claimed can address the process variation such as vertical and lateral dimension variation by electrostatic tuning method.