Fully Differential MEMS Gyroscope for Stable Pitch/Roll Sensing
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Solution Overview
Problem
Existing microelectromechanical gyroscopes face challenges in maintaining scale factor stability and vibration rejection, particularly for rotations around pitch or roll axes, due to deformations caused by external factors like temperature variations and mechanical stress, which affect the accuracy of in-plane-type sensing structures.
Innovation Solution
A microelectromechanical gyroscope with a fully differential structure that converts out-of-plane motion of transduction masses into in-plane motion of sensing masses using skew bending motion conversion flexures, enhancing sensitivity and stability by implementing a fully differential sensing architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If out-of-plane sensing structures are used for pitch/roll sensing, then the gyroscope can sense rotations around pitch or roll axes, but the sensitivity is lower compared to in-plane sensing structures
Solution Approach 1:
The patent transforms the sensing mechanism from out-of-plane motion to in-plane motion by introducing skew bending motion conversion flexures. These flexures convert the out-of-plane oscillation of transduction masses into in-plane motion of sensing masses, allowing the sensing electrodes to develop in the plane parallel to the support body main face, thereby achieving both pitch/roll sensing capability and high sensitivity
Solution Approach 2:
The skew bending motion conversion flexures act as intermediary elements between the transduction masses and sensing masses. These flexures mediate the motion conversion process, transforming the out-of-plane motion of transduction masses into the in-plane motion of sensing masses, thus enabling the fully differential sensing architecture to achieve high sensitivity for pitch/roll sensing
2Reliability
If fully differential sensing architecture is implemented, then common-mode contributions are rejected and scale factor stability is improved, but the device complexity increases
Solution Approach 1:
The sensing architecture is segmented into multiple independent sensing channels, with each transduction mass connected to two sensing masses through skew bending motion conversion flexures. This segmentation enables the fully differential sensing structure where each movable sensing electrode is differentially coupled to two respective fixed sensing electrodes, achieving common-mode rejection and scale factor stability while maintaining manageable complexity through modular design
3Measurement precision
If in-plane sensing structures are used, then fixed sensing electrodes are closer and less affected by support body deformations, but the gyroscope cannot effectively sense rotations around pitch or roll axes
Solution Approach 1:
The patent uses skew bending motion conversion flexures to transform the motion dimension from out-of-plane to in-plane. The transduction masses oscillate out-of-plane, but through the skew bending action of the flexures, this motion is converted into in-plane motion of the sensing masses, allowing the sensing electrodes to be positioned in the plane parallel to the support body main face, thus achieving both high sensitivity and pitch/roll sensing capability
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
Improves the rejection of common-mode contributions and maintains scale factor stability by converting out-of-plane motion into in-plane motion, effectively addressing deformations caused by external factors.
Implementation Method 1
skew bending motion conversion flexures
Implementation Method 2
Sensing masses (5a-5d) are provided with movable sensing electrodes (22) capacitively coupled to respective first fixed sensing electrodes (23a) and second fixed sensing electrodes (23b)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A microelectromechanical gyroscope includes: a support body (2) having a main surface (2a) parallel to a reference plane (XY) defined by a first axis (X) and a second axis (Y) perpendicular to each other; transduction masses (3a, 3b), constrained to the support body (2) so as to be capable of oscillating along a driving direction (DD) parallel to the first axis (X) and along a third axis (Z) perpendicular to the first axis (X) and the second axis (Y); sensing masses (5a-5d), constrained to the support body (2) at a distance from the substrate (7) so as to be capable of oscillating in a direction parallel to the second axis (Y); and motion conversion flexures (25) connecting the transduction masses (3a, 3b) to respective sensing masses (5a-5d) and configured so as to convert movements of the transduction masses (3a, 3b) along the third axis (Z) into movements of the respective sensing masses (5a-5d) along the second axis (Y).