Decoupled Lateral Axis MEMS Gyroscope with Thickness-Insensitive Spring
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Solution Overview
Problem
Conventional MEMS gyroscope sensors face performance limitations due to design and manufacturing imperfections, such as asymmetric structures, misalignment, non-ideal coupling springs, and unwanted resonance modes, which result in mechanical and electrostatic force perturbations and degrade sensor accuracy.
Innovation Solution
A fully decoupled lateral axis MEMS gyroscope design with symmetric drive and sense elements, utilizing vertical springs with torsional portions thinner than their thickness to minimize erroneous signal input and suppress unwanted resonance modes, thereby reducing quadrature error and increasing resistance to linear acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MEMS gyroscope designs are used, then manufacturing is simpler, but performance is degraded due to asymmetric structures, misalignment, and non-ideal coupling springs causing mechanical and electrostatic force perturbations
Solution Approach 1:
The patent employs asymmetric spring designs where the first and second springs have different configurations relative to the drive and sense elements. This intentional asymmetry compensates for manufacturing imperfections and alignment errors, reducing quadrature error and improving measurement accuracy while maintaining a relatively simple overall device structure
Solution Approach 2:
The gyroscope is divided into distinct functional components: drive elements, sense elements, and coupling springs, each optimized independently. This segmentation allows for precise control of mechanical and electrostatic forces in each component, reducing perturbations and improving sensor accuracy without significantly increasing overall device complexity
2Reliability
If symmetric drive and sense elements are used, then unwanted resonance modes are suppressed and resistance to linear acceleration is increased, but manufacturing precision requirements are more stringent
Solution Approach 1:
While the drive and sense elements are designed to be symmetric to suppress unwanted resonance modes and improve resistance to linear acceleration, the patent intentionally introduces asymmetric spring configurations to compensate for inevitable manufacturing imperfections. This hybrid approach maintains the benefits of symmetry while mitigating its stringent precision requirements
Solution Approach 2:
The patent optimizes spring parameters such as stiffness, length, and attachment points to achieve the desired symmetry in drive and sense elements while accommodating manufacturing tolerances. By carefully adjusting these parameters, the design achieves improved resistance to linear acceleration without requiring extremely high manufacturing precision
3Measurement precision
If vertical springs with torsional portions thinner than their thickness are used, then frequency response predictability is improved and thickness variation impact is minimized, but manufacturing complexity increases
Solution Approach 1:
The springs are designed with non-uniform cross-sections where the torsional portions have locally reduced thickness compared to other sections. This local quality variation optimizes the frequency response and reduces sensitivity to overall thickness variations while keeping the manufacturing process relatively simple through standard MEMS fabrication techniques
4Measurement precision
If fully decoupled lateral axis design is implemented, then erroneous signal input is reduced and quadrature error is minimized, but device structure becomes more complex
Solution Approach 1:
The gyroscope employs distinct drive elements and sense elements that are mechanically decoupled through specifically configured springs. This segmentation minimizes erroneous signal coupling and quadrature error while maintaining a compact structure that does not excessively increase device complexity
Solution Approach 2:
The asymmetric spring configurations are designed to provide different coupling characteristics for drive and sense elements, achieving effective decoupling that reduces quadrature error. This asymmetric design achieves the decoupling function with relatively simple spring structures rather than complex mechanical isolation mechanisms
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 achieves improved predictability and frequency response of the gyroscope, reducing electrical noise and enhancing accuracy by minimizing the impact of thickness variations and manufacturing imperfections, resulting in a more reliable angular velocity measurement.
Implementation Method 1
Each vertical beam torsional spring includes a body having a length dimension parallel to a center line axis that is longer than a width dimension in a plane that is orthogonal to the center line axis, and a plurality of beam connector elements that connect the body between a drive mass and a sense mass
Implementation Method 2
a pair of electrodes symmetrically disposed in relation to a center line axis and positioned beneath the sense mass to sense out-of-plane motion of the sense mass
Implementation Method 3
a pair of drive masses formed in a single layer over a substrate and symmetrically disposed in relation to a center line axis and connected by a first spring system to undergo oscillator linear motion within a plane
Data Source
AI summary
A micro-electromechanical systems (MEMS) transducer (400) is adapted to use lateral axis vibration of the drive mass (210) to generate non-planar oscillations of a coupling mass (220) in response to Coriolis forces created from in-plane rotation, which in turn generate non-planar motions of a symmetric teeter-totter sense mass (230) which are detected as a capacitive difference signal by capacitive electrodes (403, 404) formed on the substrate (402) below the sense mass (230).