Single Drive Mode MEMS Gyroscope for Triaxial Sensing
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Solution Overview
Problem
Designing a multiple sense axis MEMS gyroscope is complex due to the need for multiple drive systems and control loops, which leads to inaccurate sense measurements, increased area occupation, and high power consumption, as well as susceptibility to external perturbations and damping issues.
Innovation Solution
A single drive mode design for a multiple sense axis MEMS gyroscope, utilizing a drive spring system that reduces motion coupling between elements, allowing for efficient sensing of angular velocities about three orthogonal axes with reduced damping and complexity, thereby simplifying fabrication and increasing sensitivity without increasing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple drive systems and control loops are used to achieve multiple sense axis capability, then the gyroscope can sense angular velocity about multiple axes, but the device complexity increases and area occupation increases
Solution Approach 1:
The patent combines multiple drive systems into a single drive mode that operates along one axis. The drive mass is actuated along a single drive axis, and through strategic placement and coupling of sense masses, the system achieves sensitivity to angular velocity about multiple orthogonal axes. This merging of multiple drive functions into one drive system reduces device complexity while maintaining multiple sense axis capability.
Solution Approach 2:
The single drive mode structure serves multiple functions simultaneously. The drive mass oscillating along one axis generates Coriolis forces that can be sensed for angular velocity about multiple different axes. The sense masses are positioned and coupled such that a single drive operation enables measurement of angular velocity about three orthogonal axes, making the drive system universal for multiple sensing functions.
2Adaptability or versatility
If multiple drive systems and control loops are used to achieve multiple sense axis capability, then the gyroscope can sense angular velocity about multiple axes, but the area occupation increases
Solution Approach 1:
The patent merges multiple sensing functions into a compact structure where a single drive mass and associated sense masses occupy a reduced area compared to separate drive systems for each axis. The drive spring system and mass arrangements are optimized to achieve triaxial sensing capability within a smaller footprint by eliminating redundant drive system components.
3Adaptability or versatility
If multiple drive systems and control loops are used to achieve multiple sense axis capability, then the gyroscope can sense angular velocity about multiple axes, but power consumption increases
Solution Approach 1:
The patent combines the power requirements of multiple drive systems into a single drive mode. By actuating one drive mass along a single axis rather than operating multiple independent drive systems, the total power consumption is reduced while still achieving angular velocity sensing about multiple axes through the Coriolis effect and strategic mass coupling.
4Adaptability or versatility
If multiple drive systems and control loops are used to achieve multiple sense axis capability, then the gyroscope can sense angular velocity about multiple axes, but measurement accuracy decreases due to mutual influence of elements
Solution Approach 1:
The patent segments the sensing functions by dedicating specific sense masses to specific sensing axes while using a common drive mode. This segmentation reduces mutual interference between sensing channels because each sense mass or sense mass pair is primarily responsible for detecting angular velocity about a particular axis, isolating the measurement processes and improving accuracy.
5Adaptability or versatility
If traditional multiple drive system design is used, then multiple sense axis capability is achieved, but damping issues and susceptibility to external perturbations increase
Solution Approach 1:
The patent merges multiple sensing functions into a single drive mode structure that inherently reduces damping issues. By operating one drive mass along one axis rather than multiple drive masses on multiple axes, the system reduces the number of elements subject to damping forces and external perturbations, thereby improving reliability and robustness while maintaining multiple sense axis 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
The single drive mode design enhances the robustness and sensitivity of the MEMS gyroscope, reducing power consumption and area requirements, while minimizing damping and external perturbation susceptibility, resulting in a more efficient and accurate multiple sense axis capability.
Implementation Method 1
MEMS gyroscopes typically exploit a Coriolis acceleration. That is, when rotation at an angular velocity (the value of which is to be sensed) is applied to a mobile sense mass that is being driven at a known drive velocity, the sense mass 'feels' an apparent force, called the 'Coriolis force.'
Implementation Method 2
The displacement is proportional to the angular velocity of the rotation which may be detected as a change in capacitance.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A gyroscope (20) includes a first drive mass (22) driven in a first drive motion (140) along a first axis (100), the first drive motion (140) generating a first sense motion (144) of a first sense mass (68) in response to rotation of the gyroscope (20). The gyroscope (20) further includes a second drive mass (24) driven in a second drive motion (142) along a second axis (102) that is transverse to the first axis (100). The second drive motion (142) generates a second sense motion (146) of a second sense mass (70) in response to rotation of the gyroscope (20). A drive spring system (36) interconnects the two drive masses (22, 24) to couple the first and second drive motions (140, 142) so that a single drive mode (98) can be implemented. The sense motion (144, 146) of each sense mass (68, 70) is along a third axis (118), where the third axis (118) is transverse to the other axes (100, 102). The sense motion (144, 146) is translational motion such the sense masses (68, 70) remain parallel to the surface (30) of the substrate (32).