MEMS Accelerometer Electrode Structure for Multi-Axis Sensing
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Solution Overview
Problem
Existing multi-axis micromachined gyroscopes and accelerometers require separate drive and sense electronics for each axis, leading to increased size and cost, and suffer from cross-axis sensitivity and temperature coefficient issues due to separate proof-masses and complex control electronics.
Innovation Solution
A micromachined monolithic 3-axis gyroscope and accelerometer design utilizing a single center-anchored proof-mass with unique partitioning and flexure structures to decouple response modes, allowing for single drive-mode oscillation and reduced cross-axis sensitivity, and shifting mass from electrode stator frames to proof-mass frames to improve shock and vibration resistance and temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate proof-masses are used for each acceleration axis, then measurement precision for each axis is improved, but device complexity and size increase
Solution Approach 1:
The patent combines three separate acceleration sensing functions into a single integrated proof-mass structure. The unified proof-mass contains embedded electrodes that can detect acceleration along multiple axes simultaneously, eliminating the need for three separate proof-masses while maintaining measurement capabilities for each axis.
Solution Approach 2:
The single proof-mass structure serves multiple functions: it acts as the sensing element for all three acceleration axes, provides a common reference frame, and integrates multiple electrode sets for different measurement directions. This multi-functional design reduces overall device complexity while preserving measurement precision.
2Measurement precision
If separate drive and sense electronics are used for each sensor, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the drive and sense electronics into a shared electronic system that serves all three gyroscope axes. The unified electronic architecture provides drive signals to common drive electrodes and processes sense signals from multiple axes simultaneously, reducing the quantity of electronic components while maintaining precise angular rate detection.
Solution Approach 2:
The shared electronics system performs multiple functions: generating drive signals for gyroscopic operation, sensing angular rate across three axes, and providing compensation signals. This multi-functional electronic design reduces complexity and cost while preserving measurement precision through centralized signal processing.
3Measurement precision
If complex control electronics are used, then measurement precision is improved, but temperature performance deteriorates
Solution Approach 1:
The patent extracts and eliminates complex control electronics from the system by using a simplified capacitive sensing approach. The design relies on direct capacitive measurement between proof-mass electrodes and stator electrodes, removing the need for complicated control circuits that generate temperature drift, thereby improving temperature performance while maintaining adequate measurement precision.
4Adaptability or versatility
If separate sensors are integrated into a 3-axis cluster, then measurement capability is improved, but size and cost increase
Solution Approach 1:
The patent merges three separate acceleration sensors into a single integrated device with a unified proof-mass structure. The combined sensor provides 3-axis acceleration detection capability while occupying significantly less area than three separate sensors, as the proof-mass and electrode structures are shared across all three measurement axes.
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 reduces the complexity and cost of control electronics, minimizes cross-axis sensitivity, and enhances temperature performance, resulting in a more robust and efficient 3-axis angular rate and acceleration detection system with improved shock and vibration resistance.
Implementation Method 1
first and second electrode stator frames... each separately including a central platform and an anchor configured to fix the central platform to the via wafer
Implementation Method 2
unique partitioning and flexure structures to decouple response modes, allowing for single drive-mode oscillation
Data Source
AI summary
This document discusses, among other things, an inertial sensor including a single proof-mass formed in an x-y plane of a device layer, the single proof-mass including a single, central anchor configured to suspend the single proof-mass above a via wafer. The inertial sensor further includes first and second electrode stator frames formed in the x-y plane of the device layer on respective first and second sides of the inertial sensor, the first and second electrode stator frames symmetric about the single, central anchor, and each separately including a central platform and an anchor configured to fix the central platform to the via wafer, wherein the anchors for the first and second electrode stator frames are asymmetric along the central platforms with respect to the single, central anchor.