Selective Coupler for MEMS Inertial Sensors
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Solution Overview
Problem
MEMS gyroscopes face inaccuracies and structural damage due to coupling of out-of-plane motion between moving masses, which can lead to false rotation detection and weakened structural integrity.
Innovation Solution
A coupler comprising two levers connected by respective tethers to an anchor and coupled together by a spring, which selectively couples in-plane motion while decoupling out-of-plane motion, using levers of substantially uniform thickness and a curved or straight spring configuration to achieve area-efficient and strong coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If moving masses are coupled together in MEMS gyroscopes, then the device can detect rotation, but out-of-plane motion coupling causes false rotation detection and structural damage
Solution Approach 1:
The coupler is divided into two separate levers (first lever and second lever) that are coupled through a spring rather than being a single rigid structure. This segmentation allows the levers to independently handle in-plane motion while the spring absorbs out-of-plane motion, preventing false rotation detection and structural damage.
Solution Approach 2:
A spring is introduced as an intermediary element between the first lever and second lever. The spring acts as a mediator that couples the levers for in-plane motion transfer while decoupling them for out-of-plane motion, allowing the system to maintain structural integrity while enabling rotation detection.
2Strength
If a rigid coupler is used to connect moving masses, then strong coupling is achieved, but out-of-plane motion is not decoupled leading to false rotation detection
Solution Approach 1:
The coupler transitions from a rigid static structure to a dynamic structure with flexible elements (springs and tethers). The spring provides dynamic coupling that adapts to motion directions, strongly coupling in-plane motion for detection while allowing out-of-plane motion to be absorbed without causing false readings.
Solution Approach 2:
The coupling characteristics are changed by using a spring with specific stiffness properties. The spring's mechanical properties are tuned to provide high coupling strength for in-plane motion while being compliant to out-of-plane motion, thereby changing the coupling parameters to achieve both strong coupling and false rotation prevention.
3Measurement precision
If levers of varied thickness are used to achieve selective coupling, then in-plane motion is coupled and out-of-plane motion is decoupled, but manufacturing complexity increases
Solution Approach 1:
Instead of varying the thickness of levers throughout their entire length, the patent uses uniform thickness levers with localized functional features. The first lever has a first thickness and the second lever has a second thickness, but both are substantially uniform along their lengths. The selective coupling is achieved through the spring connection and tether geometry rather than variable thickness, simplifying manufacturing.
4Measurement precision
If a complex coupler structure is used to transfer in-plane motion and decouple out-of-plane motion, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The first lever and second lever are merged into a single coupler assembly that performs multiple functions simultaneously. The spring connects both levers to provide both in-plane motion transfer and out-of-plane motion decoupling in a unified structure, reducing overall device complexity compared to separate components.
Solution Approach 2:
The coupler assembly with two levers and a spring serves multiple functions: it transfers in-plane motion between masses, decouples out-of-plane motion, provides structural support, and enables rotation detection. This multi-functionality reduces the need for additional separate components, thereby reducing overall device 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 effectively transfers in-plane motion while preventing out-of-plane motion, enhancing the accuracy and durability of MEMS inertial sensors by minimizing false rotation detection and structural damage.
Implementation Method 1
coupled together by a spring
Implementation Method 2
coupled together by a spring
Implementation Method 3
coupled to an anchor by respective tethers
Data Source
AI summary
Couplers for selectively coupling in-plane and out-of-plane motion between moving masses are provided herein. In particular, aspects of the present application provide for a coupler configured to couple in-plane motion between moving masses while decoupling out-of-plane motion between the moving masses. The selective couplers as described herein may be used in a device, such as a microelectromechanical systems (MEMS) inertial sensor. In some embodiments, a MEMS inertial sensor comprises a first mass configured to move in-plane, a second mass configured to move in-plane and out-of-plane, and a coupler coupling the first and second masses and comprising two levers coupled to an anchor point by respective tethers and coupled to each other by a spring.