MEMS Accelerometer Seesaw Coupling for Linearity
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Solution Overview
Problem
Conventional out-of-plane acceleration sensors using seesaw structures face challenges in suppressing rotations and improving linearity of capacitance detection, with existing solutions either failing to eliminate in-plane rotations or having poor suppression of reverse movements around axes.
Innovation Solution
A MEMS accelerometer design featuring two or more seesaw structures with a double coupling structure, where the proof mass is mainly disposed on an outer coupling structure, allowing linear motion along the Z-axis and suppressing remaining translational and rotational modes, enhancing linearity and reducing spurious modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional seesaw structure is used, then the structure is simple, but it cannot suppress rotations and has poor linearity in capacitance detection
Solution Approach 1:
The patent divides the seesaw structure into multiple segments (first seesaw structure and second seesaw structure) that are oppositely disposed and independently connected to the base. Each seesaw structure has its own proof mass and can move independently, allowing the system to detect both in-plane and out-of-plane accelerations while maintaining linearity through differential measurement.
Solution Approach 2:
The patent combines multiple seesaw structures into a single integrated system where the first and second seesaw structures share common anchor points and are coupled through a coupling structure. This merging allows the system to achieve enhanced measurement capabilities and improved linearity while suppressing unwanted rotational modes through the coordinated motion of the combined structures.
2Measurement precision
If the detection plate is set far away from the rotation axis, then the gain of capacitance change is ensured, but rotations around Z-axis and X-axis cannot be suppressed
Solution Approach 1:
The patent employs asymmetric positioning of the detection plate relative to the rotation axis, placing it at a specific distance to optimize capacitance change gain. The asymmetric configuration of oppositely disposed seesaw structures with different proof mass arrangements allows the system to maximize the capacitive signal while the coupling structure simultaneously suppresses spurious rotations around the Z-axis and X-axis through differential motion cancellation.
3Object-affected harmful factors
If a single seesaw structure is used, then the device is simple, but it cannot suppress in-plane rotation and reverse movement around axes
Solution Approach 1:
The patent segments the acceleration sensing function into multiple specialized components: the first seesaw structure detects in-plane acceleration along the X-axis, the second seesaw structure detects in-plane acceleration along the Y-axis, and the coupling structure suppresses spurious rotations. This segmentation allows each component to be optimized for its specific function while collectively achieving comprehensive spurious mode suppression.
Solution Approach 2:
The coupling structure serves multiple functions simultaneously: it connects the first and second seesaw structures to the base, provides elastic support for their motion, and acts as a mechanical filter to suppress spurious rotations around the Z-axis and X-axis. This multi-functionality reduces the need for additional dedicated suppression mechanisms, balancing complexity with performance.
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 improves the linearity of capacitive and non-capacitive displacement detection methods, such as optical detection, by ensuring the mass center is close to the rotation axis, resulting in a more concentrated mass and fewer spurious modes.
Implementation Method 1
The first coupling structure and the second coupling structure are elastic coupling structures
Implementation Method 2
the first elastic torsion spring is fixed to the first anchor point... the second elastic torsion spring is fixed to a second end of the second anchor point
Data Source
AI summary
A MEMS accelerometer includes a base, proof mass, at least one pair of seesaw structures, and an out-of-plane displacement detection component. The at least one pair of the seesaw structures are oppositely disposed and fixed on the base through anchor points, and the out-of-plane displacement detection component is configured to detect rotation of the at least one pair of the seesaw structures or out-of-plane linear motion of the proof mass. Linear displacement of the MEMS accelerometer is not only beneficial to improve linearity of a capacitive displacement detection, but also to other non-capacitive detection methods, such as optical displacement detection. In addition, a double coupling structure is adopted to jointly couple rotation of seesaws, and remaining translational and rotational modes of the seesaw structures are suppressed.