Vibratory Ring Electrode Geometry for MEMS Gyroscope Stability
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Solution Overview
Problem
MEMS gyroscope devices face issues with non-uniform charge trapping leading to misalignment of transducers and reduced capacitive coupling, affecting sensitivity and bias performance due to variations in charge distribution across dielectric layers.
Innovation Solution
A vibratory ring structure with ring electrodes extending over a larger angular extent than their attachment, centered on anti-nodes of vibrational modes, maintains uniform spacing and reduces the impact of non-uniform charge distribution, enhancing capacitive coupling and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed electrodes are positioned close to the ring structure to enhance capacitive coupling, then sensitivity is improved, but non-uniform charge distribution causes misalignment and sensitivity variations
Solution Approach 1:
The patent applies local quality by creating a differential capacitive sensing arrangement where opposite electrodes experience different capacitance changes during vibration. This local differentiation allows the system to detect vibrational modes while being insensitive to uniform charge distribution errors, resolving the contradiction between close electrode positioning for sensitivity and charge distribution uniformity for alignment stability.
Solution Approach 2:
The patent introduces a differential measurement scheme as an intermediary that processes signals from multiple electrodes. By taking the difference between opposite electrode pairs, the system eliminates common-mode errors from non-uniform charge distribution while preserving the differential signal from vibrational modes, thus maintaining both sensitivity and alignment stability.
2Power
If ring electrodes extend over a larger angular extent to improve capacitive coupling, then coupling strength increases, but attachment complexity increases
Solution Approach 1:
The patent segments the ring electrode into multiple discrete electrodes positioned at specific angular locations around the ring. This segmentation allows each electrode to be independently attached at simple points while collectively providing enhanced capacitive coupling through their combined effect, resolving the contradiction between large angular extent for coupling strength and attachment complexity.
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 improves capacitive coupling and reduces sensitivity variations, leading to better bias performance and shock stability in angular rate sensors by ensuring uniform electrode movement and defined transducer alignment.
Implementation Method 1
operates using a cos 2θ in-plane flexural mode pair
Implementation Method 2
The mutual capacitance between the ring structure and the fixed electrodes results in capacitive coupling which may be used to exert a force on the ring structure or to detect a displacement or velocity of the ring structure
Implementation Method 3
capacitive coupling which may be used to exert a force on the ring structure
Data Source
AI summary
A vibratory ring structure is described which comprises a ring body and at least one ring electrode secured thereto, the or each ring electrode extending over a first angular extent and: being attached to the ring body over second angular extent, wherein the first angular extent is greater than the second angular extent.