Dual-Axis MEMS Gyroscope Layout for Common-Mode Oscillation Suppression
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Solution Overview
Problem
Conventional MEMS angular rate sensors are susceptible to common mode oscillation due to linear and angular acceleration, leading to inaccuracy or failure, which is not effectively addressed by existing technologies.
Innovation Solution
A MEMS dual axis angular rate sensor with a quad mass gyroscope arrangement featuring two sets of proof masses, each coupled to a common mode rejection mechanism, which mitigates oscillation between adjacent proof masses to suppress common mode oscillation, enhancing accuracy by promoting anti-phase motion and reducing cross-coupling between sense rate channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MEMS angular rate sensors use a single proof mass configuration, then the device structure is simple, but the sensor is susceptible to common mode oscillation caused by linear and angular acceleration
Solution Approach 1:
The sensor divides the proof mass into two separate configurations: a first proof mass for detecting rotation about a first axis and a second proof mass for detecting rotation about a second axis. This segmentation allows each proof mass to be optimized for its specific sensing function while the overall structure remains manageable. The segmentation enables independent optimization of each sensing channel, reducing cross-axis coupling and common mode oscillation effects.
Solution Approach 2:
The patent introduces a third dimension by adding a third proof mass that detects rotation about a third axis, creating a three-dimensional sensing architecture. This dimensional expansion allows the sensor to simultaneously measure rotations about multiple axes using orthogonal proof mass configurations, thereby reducing common mode oscillation effects through dimensional separation of sensing functions.
2Adaptability or versatility
If the sensor uses multiple proof masses for multi-axis detection, then the sensing capability is improved, but common mode oscillation between adjacent proof masses increases
Solution Approach 1:
The patent employs asymmetric spring configurations where the first spring has different stiffness characteristics than the second spring. Specifically, the first spring is optimized for oscillation along the first axis while the second spring is optimized for oscillation along the second axis. This asymmetry in spring properties creates differential response characteristics that suppress common mode oscillation by preventing synchronous oscillation between adjacent proof masses.
Solution Approach 2:
Each proof mass and its associated springs are designed with local optimization for its specific sensing function. The first proof mass and its springs are tailored for detecting rotation about the first axis, while the second proof mass and its springs are tailored for the second axis. This local quality optimization ensures that each sensing element responds maximally to its intended axis while minimizing coupling to other axes and common mode oscillation.
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 effectively suppresses common mode oscillation, improving the accuracy and reliability of angular rate sensing by mitigating the impact of linear and angular acceleration on sensor output readings.
Implementation Method 1
When the substrate (including the proof mass) experiences rotation while the proof mass is driven to oscillate along the drive axis, the motion of the proof mass will deviate from the drive axis due to a Coriolis force along an axis (i.e., 'sense axis') that is different from that of the drive axis.
Data Source
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AI summary
Embodiments of an angular rate sensor are described, including a MEMS structure having a first set of proof masses arranged in a first two-dimensional array, a second set of proof masses arranged in a second two-dimensional array, and drive actuators, each configured to drive a respective proof mass of the first set of proof masses and a respective proof mass of the second set of proof masses. At least two proof masses of the first set of proof masses are disposed at opposite sides of the second set of proof masses.