Variable-Surface MEMS Capacitor for Gyroscope Resonance Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS gyrometers face challenges in achieving equal resonance frequencies for mobile frames due to manufacturing imperfections in spring stiffness, leading to measurement biases and limited adjustable stiffness, which affects rotation speed measurements and introduces non-linearities in restoring forces.
Innovation Solution
A variable surface capacitor device with non-parallel rectilinear edges for the electrodes, allowing for adjustable transverse and longitudinal stiffness coefficients, enabling precise control of electrostatic forces and improving resonance matching between frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional parallel-edge capacitor electrodes are used, then the structure is simple and manufacturing is easy, but the stiffness coefficient is limited and cannot be adjusted independently in transverse and longitudinal directions
Solution Approach 1:
The patent applies asymmetry by configuring the capacitor electrodes with non-parallel rectilinear edges, creating an asymmetric geometric arrangement. This asymmetric electrode configuration enables the generation of both transverse and longitudinal stiffness coefficients that can be independently adjusted, overcoming the limitation of traditional parallel-edge designs where only one stiffness coefficient could be obtained.
Solution Approach 2:
The patent transitions from a single-degree-of-freedom stiffness control to multi-degree-of-freedom control by introducing non-parallel edges. This dimensional change in the electrode geometry allows the system to generate stiffness coefficients in multiple directions (transverse and longitudinal) simultaneously, enabling independent adjustment of each stiffness coefficient through appropriate electrode configurations.
2Measurement precision
If manufacturing precision is improved to achieve equal spring stiffness, then resonance frequency matching is better, but manufacturing cost and time increase
Solution Approach 1:
The patent replaces mechanical adjustment methods with electrostatic field-based stiffness control. Instead of relying on precise mechanical manufacturing to achieve equal spring stiffness, the system uses the electrostatic forces generated by the non-parallel electrode configurations to provide adjustable transverse and longitudinal stiffness coefficients, thereby compensating for manufacturing variations without requiring high-precision manufacturing.
Solution Approach 2:
The patent changes the geometric parameters of the electrode configuration (non-parallel edges with specific angles and dimensions) to control the stiffness coefficients. By adjusting the electrode geometry parameters and applied voltages, the system can independently tune the transverse and longitudinal stiffness to achieve resonance frequency matching, eliminating the need for precise mechanical spring manufacturing.
3Adaptability or versatility
If variable surface capacitor with non-parallel edges is used, then adjustable stiffness and resonance matching are achieved, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing the non-parallel edge capacitor structure to simultaneously provide both transverse and longitudinal stiffness coefficients. This single capacitor configuration serves multiple functions: it can independently adjust stiffness in two different directions, enabling both transverse and longitudinal resonance frequency tuning without requiring separate adjustment mechanisms for each direction.
4Measurement precision
If higher stiffness coefficients are achieved, then measurement bias is reduced, but the structure becomes more complex
Solution Approach 1:
The asymmetric non-parallel edge configuration enables the generation of higher stiffness coefficients by optimizing the angle and dimensions of the electrode edges. The asymmetric geometry allows for enhanced electrostatic coupling and greater controllable stiffness, which improves measurement accuracy by reducing measurement bias while maintaining appropriate force linearity through proper geometric 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 device achieves higher stiffness coefficients and minimizes measurement biases by allowing independent adjustment of transverse and longitudinal stiffness, enhancing the accuracy of rotation speed measurements and reducing sensitivity to mechanical vibrations.
Implementation Method 1
A variable surface capacitor device with non-parallel rectilinear edges for the electrodes, allowing for adjustable transverse and longitudinal stiffness coefficients, enabling precise control of electrostatic forces
Implementation Method 2
the overlapping area As varies approximately quadratically as a function of the displacement x... This variation in area causes a variation in the electrical capacitance C of the capacitor formed by the first and second electrodes... a variation which results in an elastic restoring force
Implementation Method 3
A rotation of the gyrometer around an axis Z, perpendicular to the excitation and detection directions X and Y, then causes a displacement of each test mass in the detection direction Y (under the effect of the Coriolis force experienced by the test mass)
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates in particular to a variable-surface capacitor device (15) for a microelectromechanical system, the device comprising a first electrode (151) and a second electrode (152) movable relative to each other, the first electrode having a first free surface (S1) and the second electrode having a second free surface (S2) that partially overlaps the first surface. In the portion where it overlaps the second surface, the first surface is laterally delimited by two straight, non-parallel edges (b11, b21). In the portion where it overlaps the first surface, the second surface is also delimited by two straight, non-parallel edges (b12, b22). The invention also relates to a microelectromechanical system, for example a gyroscope, equipped with such a variable-surface capacitor device.