Hexagonal Crystal MEMS Gyroscope for Whole Angle Mode
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Solution Overview
Problem
Existing MEMS gyroscopes operating in rate mode face limitations due to dynamic range constraints and spring non-linearities at high rotation rates, while whole angle mode gyroscopes require exceptional symmetry and low damping to avoid bias instability, but are often large and costly.
Innovation Solution
A new MEMS gyroscope design combining features of lumped-element Tuning Fork and rotationally symmetric gyroscopes, using large masses on weak flexures with eight-fold symmetry, capable of operating in both rate and whole angle modes, and fabricated on a hexagonal crystal-based substrate for low cost and high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If MEMS gyroscope operates in rate mode with open-loop sense axis, then manufacturing cost and device complexity are reduced, but measurement precision deteriorates at high rotation rates due to dynamic range limitations and spring non-linearities
Solution Approach 1:
The patent implements a dual-mode operational capability where the gyroscope can dynamically switch between rate mode and whole angle mode based on rotation rate conditions. The system automatically transitions to whole angle mode when high rotation rates are detected, thereby maintaining measurement precision across the full dynamic range while preserving the cost benefits of MEMS fabrication
Solution Approach 2:
The patent changes the operational parameters of the gyroscope by implementing whole angle mode operation with equal amplitude drive on both axes, allowing the system to adapt its measurement characteristics based on the rotation rate. This parameter change enables the gyroscope to maintain accuracy at high rates by preventing the sense axis from saturating
2Measurement precision
If MEMS gyroscope operates in whole angle mode with equal amplitude drive, then measurement precision is improved across wide rotation rates, but device complexity and manufacturing cost increase due to symmetry requirements
Solution Approach 1:
The patent deliberately introduces controlled asymmetry through electrostatic actuation forces to compensate for fabrication-induced symmetries. By applying differential voltages to the drive electrodes, the system can trim the mode split and achieve the required equal amplitude operation, thereby reducing the stringent mechanical symmetry requirements
Solution Approach 2:
The patent implements feedback control mechanisms that monitor the amplitude equality between the two drive axes and adjust the actuation forces accordingly. This feedback loop maintains the whole angle mode operation conditions even when fabrication variations introduce asymmetries, reducing the impact of manufacturing precision limitations
3Measurement precision
If whole angle mode gyroscope uses large masses on weak flexures, then sensitivity is improved, but damping increases causing bias instability
Solution Approach 1:
The patent employs local quality optimization by using large proof masses coupled to the vibratory structure through weak flexures only at specific locations. This localized coupling provides the desired sensitivity enhancement while minimizing the overall damping effect on the vibratory modes, thereby maintaining bias stability
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 design achieves high sensitivity and dynamic range with low damping, enabling accurate angle and rotation rate measurements across a wide range of rates without the cost and size limitations of traditional whole angle gyroscopes.
Implementation Method 1
fabricated on a hexagonal crystal-based substrate for low cost and high sensitivity
Implementation Method 2
a mass moving at a given velocity will experience Coriolis acceleration when the mass is also rotated with an angular velocity. The Coriolis acceleration is perpendicular to the velocity and the angular velocity
Data Source
AI summary
According to one aspect, embodiments herein provide a gyroscope comprising an axially symmetric structure, and a plurality of transducers, each configured to perform at least one of driving and sensing motion of the axially symmetric structure, wherein the plurality of transducers is configured to drive the axially symmetric structure in at least a first vibratory mode and a second vibratory mode, and wherein the gyroscope is implemented on a hexagonal crystal-based substrate.