MEMS Gyroscope Vibration Robustness via Segmented Mass Design
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Solution Overview
Problem
Current MEMS gyroscopes are sensitive to vibrations, which cause spurious signals and affect stability, especially in applications requiring robustness against high-frequency vibrations, and increasing redundancy to address this issue often results in larger device sizes that do not fully solve the problem.
Innovation Solution
A MEMS gyroscope design featuring a first and second movable mass with alternate drive movements, coupled through rigid and compliant drive elastic structures, and sense elastic systems, allowing for robustness against vibrations while maintaining reduced dimensions by decoupling drive and sense movements and using bridge elements to cancel out vibration-induced displacements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple redundant structures are used to increase sensing robustness, then robustness to vibrations is improved, but device size increases significantly
Solution Approach 1:
The gyroscope is divided into two separate operational modes (drive mode and sense mode) that are activated at different times. The movable mass is segmented in function rather than physically divided into multiple redundant structures, allowing vibration rejection through temporal separation of operations rather than spatial redundancy.
Solution Approach 2:
The gyroscope operates in periodic alternating cycles between drive mode and sense mode. During drive mode, the movable mass is excited and during sense mode, the Coriolis force is measured. This periodic switching allows the system to reject continuous vibrations by only measuring during the sense mode when the drive excitation is absent.
2Reliability
If the gyroscope structure is doubled to reduce vibration sensitivity, then measurement stability is improved, but manufacturing complexity increases
Solution Approach 1:
The gyroscope employs dynamic operation where the same physical structure serves different functions at different times. The movable mass dynamically switches between being driven (source of vibration) and being sensed (measurement target), eliminating the need for static redundant structures that would double the manufacturing complexity.
Solution Approach 2:
The single movable mass structure performs multiple functions: it generates drive motion during drive mode and serves as the sensing element during sense mode. This multi-functionality eliminates the need for separate redundant structures, reducing manufacturing complexity while maintaining measurement stability through temporal separation.
3Object-affected harmful factors
If redundant gyroscope structures are implemented to cancel vibration effects, then robustness against high-frequency vibrations is improved, but the device dimensions increase
Solution Approach 1:
The harmful vibration effects are extracted and isolated to specific time periods (drive mode) rather than being continuously present. By taking out the drive excitation from the measurement period and confining it to separate drive mode cycles, the system eliminates vibration interference during sense mode without requiring extended device dimensions for redundant structures.
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 design effectively reduces sensitivity to linear and rotational vibrations, enhancing stability and robustness while maintaining compact size, allowing for reliable sensing of angular speeds with minimal spurious signal interference.
Implementation Method 1
a first drive assembly, coupled to the first movable mass and configured to generate a first alternate drive movement
Implementation Method 2
a first drive elastic structure, coupled to the first movable mass and to the first drive assembly, rigid in the first drive direction and compliant in the first sense direction
Implementation Method 3
When the MEMS gyroscope rotates with an angular speed around a rotation axis perpendicular to the drive direction, the movable mass is subject to a Coriolis force directed along the sense direction, perpendicular to the rotation axis and to the drive direction
Data Source
AI summary
MEMS gyroscope, having a first movable mass configured to move with respect to a fixed structure along a first drive direction and along a first sense direction, transverse to the first drive direction; a first drive assembly, coupled to the first movable mass and configured to generate a first alternate drive movement; a first drive elastic structure, coupled to the first movable mass and to the first drive assembly, rigid in the first drive direction and compliant in the first sense direction; a second movable mass, configured to move with respect to the fixed structure in a second drive direction parallel to the first drive direction and in a second sense direction parallel to the first sense direction; a second drive assembly, coupled to the second movable mass and configured to generate a second alternate drive movement in the second drive direction; and a second drive elastic structure, coupled to the second movable mass and to the second drive assembly, rigid in the second drive direction and compliant in the second sense direction.