MEMS Accelerometer Anti-Phase Proof Masses
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Solution Overview
Problem
Conventional inertial sensors, such as accelerometers, face challenges in performance and reliability, particularly in mechanical and electrical sensitivities, and require improvements for commercial applications, with a need for cost-effective and adaptable solutions.
Innovation Solution
A MEMS accelerometer design featuring at least two proof masses with flexible couplings that move in an anti-phase direction normal to the substrate plane, allowing for separate sensing of acceleration and magnetic fields through differential capacitive sensing, enabling high mechanical and electrical sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional accelerometer design is used, then device complexity is reduced, but mechanical and electrical sensitivities are insufficient
Solution Approach 1:
The proof mass is divided into multiple segments (first proof mass and second proof mass) that move in anti-phase directions. This segmentation increases the mechanical sensitivity by maximizing the movement distance of each proof mass segment while maintaining a relatively simple overall sensor structure.
Solution Approach 2:
The proof masses move in the out-of-plane direction (normal to the substrate) rather than in-plane, utilizing the third dimension for sensing. This dimensional change enhances both mechanical sensitivity (larger movement range) and electrical sensitivity (capacitive coupling) without significantly increasing planar device complexity.
2Measurement precision
If proof masses move in anti-phase direction normal to substrate plane, then mechanical and electrical sensitivity are enhanced, but device size increases
Solution Approach 1:
By utilizing the out-of-plane direction for proof mass movement, the sensor achieves enhanced sensitivity without requiring large in-plane dimensions. The vertical movement exploits the third dimension, allowing compact planar footprint while maintaining large sensing amplitude.
Solution Approach 2:
The proof masses are connected to the substrate through flexible coupling structures that enable large out-of-plane movement. These flexible connections allow the proof masses to achieve significant displacement normal to the substrate while maintaining a compact overall sensor volume.
3Force
If flexible coupling is used between proof masses and substrate, then breakout force is increased, but manufacturing precision requirements increase
Solution Approach 1:
The flexible coupling structures are designed with specific geometric parameters that optimize both breakout force and manufacturability. By adjusting parameters such as beam thickness, length, and cross-section shape, the coupling provides sufficient mechanical strength for breakout while remaining compatible with standard MEMS fabrication tolerances.
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 anti-phase movement of proof masses enhances mechanical and electrical sensitivity, resulting in high breakout force, full-scale range, and signal-to-noise ratio, while allowing for reduced sensor size with maintained performance.
Implementation Method 1
A first movable electrode opposite the first fixed electrode is provided on an upper surface of the first movable portion, and a second movable electrode opposite the second fixed electrode is provided on an upper surface of the second movable portion.
Implementation Method 2
a magnetic material that causes the combined accelerometer and magnetometer to rotate around a first axis in response to a magnetic field
Data Source
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AI summary
A sensor is disclosed. The sensor includes a substrate and at least two proof masses. The sensor also includes a flexible coupling between the at least two proof masses and the substrate. The at least two coupling proof masses move in an antiphase direction normal to a plane of the substrate in response to acceleration.