MEMS Gyroscope with Anti-Phase Drive Masses for Acceleration Rejection
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Solution Overview
Problem
MEMS gyroscopes face challenges in accurately measuring angular velocity due to interference from linear acceleration and angular acceleration, which can improperly interpret forces and affect the accuracy of rotation measurements.
Innovation Solution
The design incorporates four drive masses and four sense masses, with specific coupling mechanisms that prevent linear acceleration and angular acceleration from impacting the drive and sense motions, ensuring that only Coriolis forces caused by rotation are measured, using a configuration where drive masses oscillate in perpendicular and anti-phase directions and sense masses are coupled to prevent external accelerations from affecting their motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional MEMS gyroscope designs are used, then the device can measure angular velocity, but linear acceleration and angular acceleration interfere with the measurements and reduce accuracy
Solution Approach 1:
The gyroscope is divided into four separate drive masses arranged in a square configuration, each capable of independent oscillation. This segmentation allows the system to differentiate between Coriolis forces (which affect all masses uniformly) and linear acceleration forces (which affect masses differently based on their position), thereby improving measurement precision by isolating the desired measurement from harmful interference.
Solution Approach 2:
The four drive masses are configured with opposite masses positioned diagonally across from each other. When linear acceleration occurs, the forces acting on opposite masses counterbalance each other, canceling out the harmful effects of linear and angular acceleration. This counterweight arrangement ensures that only the Coriolis forces generated by actual rotation are measured, eliminating the interference that would otherwise reduce measurement accuracy.
2Reliability
If four drive masses are used in a square configuration, then robustness to linear and angular acceleration is improved, but device complexity increases
Solution Approach 1:
The four drive masses are coupled together through a combination of rigid connections and flexible springs to form an integrated square structure. This merging allows the individual masses to work collectively as a unified system that inherently rejects linear and angular acceleration while maintaining the complexity benefits of a compact, integrated design rather than four separate components.
Solution Approach 2:
The drive masses serve multiple functions: they generate the primary oscillation signal, detect Coriolis forces through their coupled motion, and simultaneously counterbalance linear acceleration forces through their symmetric arrangement. This multi-functionality increases reliability by making the system robust to undesired forces while avoiding the need for additional separate components that would increase device complexity.
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 configuration enhances the robustness of the gyroscope to undesired forces, ensuring accurate measurement of angular velocity by isolating the effects of linear and angular accelerations, thereby improving the precision of rotation sensing.
Implementation Method 1
drive masses oscillate in perpendicular and anti-phase directions
Implementation Method 2
each of the four sense masses moves in a sense axis in response to a Coriolis force caused by the rotation of the gyroscope
Implementation Method 3
specific coupling mechanisms that prevent linear acceleration and angular acceleration from impacting the drive and sense motions
Data Source
AI summary
A gyroscope includes four drive masses and four sense masses. Each drive mass is adjacent to two other drive masses and opposite the fourth drive mass, and each sense mass is adjacent to two other sense masses and opposite the fourth sense mass. Each drive mass may oscillate in a manner that is perpendicular to its adjacent drive mass and parallel and anti-phase to its opposite mass. The sense motion of the each sense mass may be coupled in a manner that prevents motion due to linear acceleration or angular acceleration.