Angular Rate Sensor Lever Mechanism Suppressing In-Phase Motion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS angular rate sensors are susceptible to common mode excitation of Coriolis masses due to linear and angular acceleration, leading to inaccuracy or failure, as the Coriolis masses move in-phase and at a frequency lower than the operating frequency, causing inaccuracies or complete failure of the sensor.
Innovation Solution
The angular rate sensor incorporates a lever mechanism with first and second sets of levers that are configured to constrain in-phase motion of Coriolis masses, pushing resonance modes responsible for linear and angular acceleration to higher frequencies than the operating frequency, thereby suppressing common mode excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple Coriolis masses are used in a MEMS angular rate sensor, then the sensor can detect angular rate through Coriolis effect, but the sensor becomes susceptible to common mode excitation causing inaccuracy or failure
Solution Approach 1:
The sensor divides the Coriolis masses into multiple groups (first and second Coriolis masses) that can move independently along different axes. This segmentation allows the system to separate drive mode motion from sense mode motion, and to independently control the motion patterns of different mass groups to suppress common mode excitation while maintaining angular rate detection capability
Solution Approach 2:
The patent employs asymmetric coupling mechanisms where the first Coriolis masses are coupled to move along a first axis and the second Coriolis masses are coupled to move along a second axis perpendicular to the first. This asymmetric configuration creates different resonance frequencies and motion patterns for different mass groups, preventing synchronized in-phase motion that would cause common mode excitation
2Ease of operation
If Coriolis masses are driven at resonance in anti-phase, then angular rate sensing is enabled through Coriolis effect, but resonance modes from linear and angular acceleration can cause in-phase motion at lower frequencies
Solution Approach 1:
The patent introduces coupling mechanisms as intermediary elements between the Coriolis masses and the drive/sense modes. These couplings mediate the motion transmission, allowing the system to maintain anti-phase drive mode operation for sensing while preventing the direct transmission of in-phase motion caused by external accelerations. The couplings act as filters that block harmful common mode excitation while preserving useful Coriolis effect signals
Solution Approach 2:
The system employs dynamic coupling configurations where the coupling between Coriolis masses and drive/sense modes is designed to be frequency-selective. The couplings are tuned to transmit anti-phase motion at the drive frequency while blocking in-phase motion at lower frequencies caused by external accelerations. This dynamic behavior allows the sensor to operate effectively at its resonant frequency while rejecting off-frequency disturbances
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 effectively suppresses common mode excitation, enhancing the accuracy and reliability of the angular rate sensor by preventing in-phase motion of Coriolis masses, ensuring accurate angular rate sensing even under external accelerations.
Implementation Method 1
at least some of the Coriolis masses, acting as sense masses, move in phase opposition by exploiting a Coriolis acceleration component, also referred to as the Coriolis effect
Implementation Method 2
a lever mechanism having first and second sets of levers that are configured to constrain in-phase motion of the Coriolis masses
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An angular rate sensor includes four Coriolis masses, configured such that the Coriolis masses move along perpendicular drive and sense axes, and a lever mechanism having first and second sets of levers. The first set of levers is coupled outside a boundary of the Coriolis masses, and the second set of levers is coupled within a boundary of the first set of levers and between the Coriolis masses. The second set of levers is configured to produce an anti-phase drive mode motion of the Coriolis masses along the drive axis. The first set of levers is configured to allow an anti-phase sense mode motion of the Coriolis masses along the sense axis responsive to the angular rate sensor rotating around an input axis that is perpendicular to the drive and sense axes. The first and second sets of levers are configured to constrain an in-phase motion of the Coriolis masses.