MEMS Gyroscope Spring Layout for Quadrature Error Decoupling
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Solution Overview
Problem
MEMS gyroscopes face significant quadrature errors due to direct coupling of drive oscillation to sense oscillation, which are not effectively addressed by existing electrical compensation methods, particularly in x- or y-axis gyroscopes with out-of-plane motion detection, where etching imperfections lead to substantial quadrature errors.
Innovation Solution
A MEMS gyroscope design with a primary in-plane oscillator coupled to a substrate via a first spring system, a secondary in-plane oscillator connected via a drive coupling spring with higher rigidity in the in-plane direction and elasticity in the out-of-plane direction, and an out-of-plane oscillator connected via a third spring system, decoupling out-of-plane motion to minimize quadrature errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrical compensation methods are used to address quadrature errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the source of quadrature error by decoupling the drive and sense oscillations through structural design. The drive oscillator and sense oscillator are separated into distinct mechanical systems with different suspension configurations, removing the direct coupling that generates quadrature signals at their origin rather than compensating for them electrically.
Solution Approach 2:
The patent introduces differential suspension systems as intermediaries between the drive and sense oscillators. The first suspension system with higher rigidity in the drive direction and the second suspension system with higher rigidity in the sense direction act as mechanical mediators that filter out direct coupling effects while transmitting the intended oscillatory motions.
2Adaptability or versatility
If x- or y-axis gyroscopes with out-of-plane motion detection are used, then adaptability is improved, but manufacturing precision requirements worsen due to etching imperfections
Solution Approach 1:
The patent applies local quality by creating suspension systems with directionally dependent rigidity characteristics. The first suspension system is optimized with higher rigidity specifically in the drive oscillation direction, while the second suspension system has higher rigidity in the sense oscillation direction. This localized mechanical property differentiation compensates for manufacturing imperfections in specific critical directions.
Solution Approach 2:
The patent changes the mechanical parameters of the suspension systems to achieve differential rigidity. By adjusting the structural geometry and material distribution in the suspension elements, the system creates anisotropic mechanical properties where rigidity varies by direction, thereby reducing sensitivity to etching imperfections in the out-of-plane direction.
3Device complexity
If direct coupling of drive oscillation to sense oscillation is present, then device complexity is reduced, but measurement precision deteriorates due to quadrature errors
Solution Approach 1:
The patent segments the gyroscope into distinct drive and sense oscillator systems with separate suspension mechanisms. This segmentation creates mechanical independence between the two oscillatory modes, eliminating the direct coupling pathway that would otherwise cause quadrature error while maintaining overall system compactness through integrated design.
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 minimizes quadrature errors by decoupling out-of-plane motion, ensuring precise in-plane oscillations and accurate angular motion detection, enhancing the reliability of rotation rate measurements.
Implementation Method 1
a primary in-plane oscillator that includes an actuator element and that is suspended from a primary anchor region on the main body by a first spring system
Implementation Method 2
a secondary in-plane oscillator that is connected to the primary in-plane oscillator by a drive coupling spring system... with higher rigidity in the in-plane direction than in an out-of-plane direction
Implementation Method 3
suspended from one or more secondary anchor points on the main body by a second spring system... the second spring system has a higher rigidity in the first in-plane direction than the first spring system
Implementation Method 4
an out-of-plane oscillator that is connected to the secondary in-plane oscillator by a third spring system
Implementation Method 5
a primary in-plane oscillator that includes an actuator element... drive circuitry configured to actuate oscillation of the primary in-plane oscillation with the actuator element
Implementation Method 6
Rotation of the MEMS gyroscope about a third axis, which is perpendicular to both the first and second axes causes the proof mass to experience a Coriolis force, which drives oscillation of the proof mass along the second axis
Data Source
AI summary
A MEMS gyroscope for sensing rotational motion about an in-plane extending axis includes a body, a primary in-plane oscillator, a secondary in-plane oscillator and an out-of-plane oscillator. The primary in-plane oscillator includes an actuator element and is suspended from a primary anchor region on the body by a first spring system. The secondary in-plane oscillator is connected to the primary in-plane oscillator by a drive coupling spring system and is suspended from one or more secondary anchor points on the substrate by a second spring system. The out-of-plane oscillator is connected to the secondary in-plane oscillator by a third spring system. The drive coupling spring has higher rigidity in the first in-plane direction than in the out-of-plane direction, and the first spring system has higher rigidity in the first in-plane direction than the second spring system.