Out-of-Plane MEMS Gyroscope With Decoupled Sense Mode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS gyroscopes are susceptible to inaccuracies due to external forces such as linear acceleration and angular acceleration, which are misinterpreted as Coriolis forces, leading to improper measurement of angular velocity.
Innovation Solution
A MEMS gyroscope design with decoupled drive and sense modes, where drive masses move in anti-phase and are coupled through lever arms to proof masses, allowing the proof masses to move out-of-plane in response to Coriolis forces while being insensitive to external accelerations, with balanced drive and sense modes to prevent energy leakage and coupling of external forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional MEMS gyroscope designs are used with coupled drive and sense modes, then the device structure is simpler, but the measurement precision deteriorates due to susceptibility to external forces such as linear acceleration and angular acceleration
Solution Approach 1:
The gyroscope is divided into separate drive mode structures and sense mode structures that are decoupled from each other. The drive masses are configured to move in anti-phase along a first axis, while the sense masses are configured to move in response to Coriolis forces along a second axis perpendicular to the drive axis. This segmentation isolates the sense mode from external forces while maintaining structural feasibility.
Solution Approach 2:
The gyroscope employs asymmetric mass distribution with drive masses positioned to move in anti-phase and sense masses positioned to detect out-of-plane motion. The spring elements are strategically placed to provide differential coupling that enables asymmetrical response to Coriolis forces while rejecting symmetrical external accelerations.
2Reliability
If drive masses are coupled directly to proof masses without decoupling mechanisms, then the device complexity is reduced, but the reliability deteriorates due to coupling of external forces between drive and sense modes
Solution Approach 1:
Spring elements are introduced as intermediary components between the drive masses and sense masses. These springs provide mechanical coupling that transmits motion from the anti-phase drive masses to the sense masses while filtering out external acceleration forces. The spring elements enable the drive and sense modes to be functionally coupled but mechanically decoupled.
Solution Approach 2:
The gyroscope employs dynamic balancing through anti-phase drive motion of the drive masses. This dynamic configuration creates a moving equilibrium where the combined center of mass of the drive masses remains stationary, preventing transmission of external linear accelerations to the sense masses while maintaining the drive-sense coupling through the spring elements.
3Stability of the object's composition
If the gyroscope uses open drive frames with multiple moving parts, then the ease of manufacture is improved, but the stability of composition deteriorates due to susceptibility to mechanical disturbances
Solution Approach 1:
Multiple spring elements are merged into a unified coupling system that connects the drive masses to the sense masses through a common mechanical pathway. The spring elements are integrated into the MEMS structure as a cohesive assembly, providing both mechanical stability and manufacturability through standard MEMS fabrication techniques.
Solution Approach 2:
The spring elements are designed with specific stiffness parameters and geometric configurations that optimize the balance between stability and manufacturability. By adjusting the spring constants, lengths, and attachment points, the system achieves sufficient mechanical stability against disturbances while remaining compatible with standard MEMS manufacturing processes.
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 gyroscope provides accurate measurement of angular velocity by isolating the sense mode from external forces, maintaining high resonator quality factors and reducing the impact of manufacturing variations.
Implementation Method 1
When a mass that is vibrating at the drive frequency experiences a Coriolis force along an axis that is perpendicular to the drive axis as a result of rotation, it will move along this Coriolis axis
Implementation Method 2
A number of components are often physically connected by numerous springs, each of which is designed to enable motion in certain directions while restricting movement in other directions
Implementation Method 3
This Coriolis force is proportional to the angular velocity of the rotation. This motion may then be sensed based on the motion of the mass (or in some applications, an additional proof mass connected by the additional springs) in the sense direction
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A gyroscope includes drive portions, lever arms, and proof masses located in a device plane. The lever arms are caused to rotate about an anchoring point based on anti-phase movement of the drive portions along a first axis in the device plane, and are coupled to the proof masses to cause the proof masses to move in anti-phase along an axis perpendicular to the first axis in the device plane. In response to a Coriolis force applied to the proof masses, the lever arm rotates out of plane and the proof masses move relative to sense electrodes. The movement of the proof masses with respect to the sense electrodes is used to measure angular velocity.