MEMS Gyroscope with Planar Seismic Masses and Anti-Phase Oscillation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS gyroscopes face challenges in achieving high accuracy and insensitivity to external shocks while being less sensitive to deviations from designed dimensions, due to the small Coriolis force and susceptibility to vibrations and packaging complexities.
Innovation Solution
A microelectromechanical gyroscope structure with planar seismic masses and spring assemblies that enable opposite phase rotary oscillations about a common primary axis, with detection axes separated by a non-zero distance, utilizing capacitive comb structures for signal detection, which is less sensitive to packaging deformations and environmental changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensing electrodes are patterned to the cap wafer to detect seismic mass motion, then detection capability is provided, but the structure becomes more vulnerable to deviations from designed dimensions and packaging complexity increases
Solution Approach 1:
The patent introduces an intermediary mechanism by using the cap wafer not as a direct sensing element but as a support structure for suspension beams that connect to fixed electrodes on the substrate. This intermediary approach transfers the detection function from cap-wafer-integrated electrodes to substrate-based electrodes, reducing the cap's sensitivity to dimensional variations while maintaining detection capability through the suspension beam mechanism.
2Ease of manufacture
If traditional epoxy overmolding processes are used for packaging, then manufacturing simplicity is maintained, but the structure with cap-wafer-patterned electrodes cannot be properly packaged
Solution Approach 1:
The patent inverts the traditional packaging approach by designing the electrode structure such that fixed electrodes are on the substrate rather than the cap, and suspension beams provide the necessary mechanical connection. This inversion allows standard epoxy overmolding processes to be applied without compromising the electrode functionality, as the sensitive detection elements are no longer dependent on cap wafer dimensions that may vary during packaging.
3Volume of moving object
If seismic masses are positioned close together to reduce device size, then miniaturization is achieved, but susceptibility to external vibrations and shocks increases
Solution Approach 1:
The patent employs anti-weight principles by configuring two seismic masses to oscillate in anti-phase, where the motion of one mass counteracts the motion of the other. This anti-phase oscillation creates a counterbalancing effect that reduces the net impact of external vibrations and shocks on the overall structure, allowing the masses to be positioned closer together without proportionally increasing susceptibility to harmful external factors.
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 enhances signal levels and robustness against external shocks and vibrations, providing improved accuracy and stability by transforming rotary oscillations into linear oscillations detectable with capacitive comb structures.
Implementation Method 1
a first spring assembly attached to the first anchor point and the first seismic mass, which first spring assembly enables rotary oscillation of the first seismic mass
Implementation Method 2
MEMS gyroscopes use the Coriolis Effect to measure the angular rate. When a mass is moving in one direction and rotational angular velocity is applied, the mass experiences a force in orthogonal direction as a result of the Coriolis force
Implementation Method 3
The resulting physical displacement caused by the Coriolis force may then be read from, for example, a capacitively, piezoelectrically or piezoresistively sensing structure
Data Source
Figure 1
Figure 2
AI summary
A microelectromechanical gyroscope that comprises two seismic masses suspended to form a plane of masses. The seismic masses are excited into rotary oscillation about a common primary axis that is in the plane of masses. Detected angular motion causes a rotary oscillation of the first seismic mass about a first detection axis, and of the second seismic mass about a second detection axis. The detection axes are perpendicular to the plane of masses and separated by a non-zero distance.