MEMS Gyroscope Drive Mass Segmentation for Q Factor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional MEMS gyroscopes face performance limitations due to low quality factor (Q level) issues, which affect sensitivity and drive amplitude, especially in vertically driven mass designs that are prone to reduced Q levels, necessitating an improvement in driving mechanisms without overburdening the driving electronics.
Innovation Solution
A MEMS angular rate sensor with a vertical torsion driven gyroscope design incorporates drive paddles close to the center of a drive mass and a motion amplification structure, using parallel plate actuator-like motion to achieve large force and small displacement, enhancing drive amplitude and velocity while maintaining a low Q factor, and utilizing lateral sense fingers to detect in-plane motions induced by Coriolis forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If vertically driven mass design is used, then drive amplitude can be achieved, but quality factor (Q level) is reduced
Solution Approach 1:
The drive mass is segmented into multiple drive paddles (first drive paddle, second drive paddle) that can be independently actuated. This segmentation allows the system to achieve desired drive amplitude through coordinated motion of multiple paddles while distributing the mechanical stress and energy dissipation, thereby maintaining higher quality factor compared to a single vertically driven mass.
Solution Approach 2:
The invention transitions from purely vertical drive motion to a combination of vertical and lateral drive paddle motions. The drive paddles are positioned at different locations (including lateral positions) and can move in multiple directions, adding dimensional complexity to the drive mechanism. This multi-dimensional motion approach enables achieving drive amplitude without the Q-factor penalties associated with simple vertical driving.
2Speed
If drive paddles are positioned close to center of drive mass, then motion amplification is achieved, but device complexity increases
Solution Approach 1:
The invention introduces motion amplification structures as intermediary elements between the drive paddles and the drive mass. These structures include lever arms and linkages that translate small paddle motions into larger drive mass velocities. The intermediaries amplify the motion without requiring the drive paddles to be positioned at extreme locations, thus achieving high drive velocity while maintaining reasonable structural complexity.
Solution Approach 2:
The drive paddles are merged with the drive mass structure in such a way that they form an integrated assembly. The paddles are positioned close to the center and coupled to the drive mass through rigid or flexible connections, creating a unified structure that reduces the number of separate components and simplifies the overall device architecture while still achieving motion amplification.
3Force
If parallel plate actuator motion is used, then large force with small displacement is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The parallel plate actuator structures are implemented with local quality variations - different regions of the drive paddles have different mechanical properties and geometries optimized for their specific functions. The actuator plates are designed with varying thicknesses, material compositions, and structural features at different locations to achieve the desired force generation while compensating for manufacturing tolerances and reducing sensitivity to alignment errors.
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 achieves desirable drive operating amplitudes and sensitivity at an achievable quality level, effectively enhancing the performance of MEMS gyroscopes by efficiently utilizing drive motion and velocity, thereby improving angular rate sensing capabilities.
Implementation Method 1
a drive system including an electrode aligned to exert electromotive force to pivot the first drive paddle and move the drive mass about the second axis
Implementation Method 2
The amplification structure directs the drive paddles to move in a motion sufficiently like a parallel plate actuator. This motion amplification structure enables a large force and small displacement of the parallel plate actuator drive paddle to be used efficiently
Implementation Method 3
With the drive motion and velocity directed approximately vertically, lateral sense fingers can be used to detect the in-plane motions of the gyroscope that are induced by Coriolis forces from the device being subject to angular rate motion about an axis in-plane but orthogonal to the approximate axis of drive motion
Implementation Method 4
a first link including: a first end coupled to a first spring, wherein the first spring movably couples the first drive paddle to the drive mass
Implementation Method 5
A higher value indicates a sharper peak. For a MEMS gyroscope to achieve desirable sensitivity, it must achieve velocity of a moving mass and therefore large amplitude of vibration. This amplitude is often referred to as the drive amplitude achieved through the drive resonance
Data Source
AI summary
A MEMS sensor for measuring rotational motion about a first axis includes a frame, a base structure under the frame, a drive mass mounted in the frame for rotational movement about a second axis perpendicular to the first axis, and a first drive paddle in the drive mass. A first link includes a first end coupled to a first spring that movably couples the first drive paddle to the drive mass and a second end coupled to a second spring that movably couples the first link to the frame. A drive system includes an electrode aligned to exert electromotive force to pivot the first drive paddle and move the drive mass about the second axis. Deflection of the drive mass is greater than deflection of the first drive paddle when the drive system is operating.