Dual-Axis MEMS Gyroscope Layout for Common-Mode Rejection
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Solution Overview
Problem
Conventional MEMS angular rate sensors are susceptible to common mode oscillation due to linear and angular acceleration, leading to inaccuracy or failure, which is not effectively addressed by existing technologies.
Innovation Solution
A MEMS dual axis angular rate sensor with a quad mass gyroscope arrangement featuring first and second sets of proof masses, coupled with common mode rejection mechanisms to suppress in-phase motion and promote anti-phase motion, reducing cross-coupling and enhancing accuracy by mitigating the impact of external stimuli.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MEMS angular rate sensors are used, then the device can detect angular motion, but the sensor is susceptible to common mode oscillation due to linear and angular acceleration leading to inaccuracy
Solution Approach 1:
The sensor divides the proof mass into four separate masses arranged in a quad configuration, with each mass independently suspended and capable of oscillating. This segmentation allows the system to differentiate between common mode oscillations (affecting all masses equally) and useful signal oscillations (affecting masses differently), thereby rejecting acceleration artifacts while preserving angular rate detection capability
Solution Approach 2:
The patent introduces common mode rejection mechanisms as intermediary elements that couple the four proof masses together. These mechanisms act as filters that allow anti-phase oscillations (signal) to pass while blocking in-phase oscillations (common mode noise) from reaching the detection circuitry, effectively mediating between the proof masses and the measurement system
2Measurement precision
If multiple proof masses are used in a quad mass gyroscope arrangement, then cross-coupling between sense rate channels is reduced, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple proof masses into a single integrated quad mass structure that shares common suspension elements and drive mechanisms. By combining four masses into one coordinated system with shared common mode rejection mechanisms, the design achieves improved channel isolation while minimizing the complexity increase that would result from four completely separate sensor units
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 sensor effectively suppresses common mode oscillation, improving detection accuracy and reliability by isolating sense rate channels and reducing the influence of linear and angular acceleration.
Implementation Method 1
the motion of the proof mass will deviate from the drive axis due to a Coriolis force along an axis (i.e., 'sense axis') that is different from that of the drive axis
Data Source
AI summary
Embodiments of an angular rate sensor are described, including a MEMS structure having a first set of proof masses arranged in a first two-dimensional array, a second set of proof masses arranged in a second two-dimensional array, and drive actuators, each configured to drive a respective proof mass of the first set of proof masses and a respective proof mass of the second set of proof masses. At least two proof masses of the first set of proof masses are disposed at opposite sides of the second set of proof masses.