Vertical-Axis MEMS Gyroscope Anchoring for Drift-Stable Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS gyroscopes suffer from measurement errors due to deformations induced by temperature variations, mechanical stresses, and environmental factors, leading to instability in angular velocity detection.
Innovation Solution
The detection structure of the MEMS gyroscope is designed with a common anchoring area where the movable mass and fixed electrodes are mechanically coupled to the substrate in close proximity, using superimposed structural layers of conductive material to form a fully double-differential capacitive coupling architecture, making the detection insensitive to substrate deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the movable mass and fixed electrodes are anchored at separate locations on the substrate, then the detection structure can be mechanically supported, but substrate deformations cause measurement errors and instability
Solution Approach 1:
The patent merges the anchoring locations of the movable mass and fixed electrodes by bringing them into close mutual proximity at the same location on the substrate. This combination ensures that both elements experience identical substrate deformations, eliminating differential effects and improving measurement stability and precision simultaneously.
2Stability of the object's composition
If separate anchoring is used, then mechanical support is provided, but thermal expansion and mechanical stresses cause drift in Zero Rate Level and Scale Factor
Solution Approach 1:
By combining the anchoring points of movable and fixed structures, the patent ensures they share the same mechanical and thermal environment. This eliminates differential expansion and stress effects that would otherwise cause drift in detection parameters, maintaining consistent performance under varying conditions.
3Ease of operation
If the detection structure uses conventional capacitive coupling, then angular velocity can be detected, but substrate deformations induce capacitance variations and measurement errors
Solution Approach 1:
The patent combines the positioning of capacitive coupling elements to experience identical substrate deformations. This ensures that any deformation-induced capacitance changes affect both measurement points equally, allowing differential measurement techniques to eliminate these errors and maintain high precision.
4Ease of manufacture
If separate anchoring areas are used, then the detection structure can accommodate manufacturing tolerances, but package-induced deformations cause measurement drift
Solution Approach 1:
By merging the anchoring locations, the patent creates a localized detection structure that is inherently insensitive to package-induced deformations. This approach maintains manufacturing flexibility while achieving high precision by ensuring both elements experience identical mechanical environments.
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 significantly reduces drifts in the Zero Rate Level and Scale Factor, enhancing stability and maintaining consistent detection performance under varying conditions.
Implementation Method 1
When a rotation at a certain angular velocity is applied to the movable mass of the MEMS gyroscope, which is driven with a linear speed, the movable mass senses a apparent force, called the Coriolis force, which determines a displacement thereof in a direction perpendicular both to the direction of the linear driving speed and to the axis around which the aforementioned rotation occurs.
Implementation Method 2
The movable mass is supported by elastic elements that allow a displacement thereof in the direction of the apparent force. According to Hooke's law, the displacement is proportional to this apparent force
Implementation Method 3
According to Hooke's law, the displacement is proportional to this apparent force, thus being indicative of the Coriolis force and the value of the angular velocity to be detected.
Implementation Method 4
The displacement of the movable mass is detected in a capacitive manner, determining, in a resonance condition, the capacitance variations caused by the movement of the movable mass with respect to fixed sense electrodes
Data Source
Figure 1~2B
Figure 3~6
Figure 5
AI summary
A microelectromechanical gyroscope (10) with detection along a vertical axis is provided with a detection structure (10) having a movable structure (12), suspended above a substrate (13) so as to perform, as a function of an angular velocity (Ωz) around the vertical axis a sense movement along a first horizontal axis (x). The movable structure has at least one drive mass (14) internally defining a window (16), elastically coupled to a rotor anchor (20'), at an anchoring region (A), through elastic anchoring elements (21); at least one bridge element (18), rigid and of a conductive material, cantilevered suspended and extending within the window along the first horizontal axis, elastically coupled to the drive mass; movable electrodes (23), carried integrally by the bridge element with extension along a second horizontal axis (y). The detection structure (10) also has stator electrodes (28, 29), arranged in the window and interdigitated with the movable electrodes, at a certain separation distance below the bridge element (18), which extends longitudinally above the same stator electrodes and the movable electrodes.