MEMS Angular Rate Sensor Bridge Layout for Triaxial Disturbance Rejection
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Solution Overview
Problem
Existing microelectromechanical systems (MEMS) based angular rate sensors face challenges in achieving both stability and sensitivity, particularly in detecting triaxial movements, due to symmetrical structures that fail to effectively reject external disturbances and optimize sensitivity across multiple axes.
Innovation Solution
A MEMS-based angular rate sensor design featuring two pairs of suspended masses with mirror-image configurations and a central bridge, coupled by driving structures and elastic elements, which enhances stability and sensitivity by differentially detecting linear and angular movements while rejecting external disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a symmetrical structure is used in MEMS-based angular rate sensors, then the sensor can detect movements in all directions, but it fails to effectively reject external disturbances
Solution Approach 1:
The patent employs asymmetrical mass distribution within the sensor structure, where masses are positioned at different distances from the center of rotation. This asymmetry creates differential responses to external disturbances, enabling the differential detection mechanism to distinguish between actual angular rate signals and disturbance signals, thereby improving disturbance rejection while maintaining omnidirectional detection capability
2Reliability
If masses are coupled to a differential detection structure, then external disturbances can be rejected, but sensitivity to triaxial movements is not optimized
Solution Approach 1:
The patent implements local quality variations by positioning different masses at specific locations with different mechanical properties and coupling strengths to the differential detection structure. This allows each mass to contribute differently to the detection of specific movement axes, optimizing sensitivity for triaxial movements while preserving the disturbance rejection capability of the differential structure
3Ease of operation
If driving structures generate oscillation frequency in linear direction, then biasing movement is provided for sensing, but stability and sensitivity to triaxial movements are reduced
Solution Approach 1:
The patent extends the sensing capability from linear direction to three-dimensional space by strategically positioning multiple masses and coupling elements that respond to movements along three orthogonal axes. The driving structures generate oscillation that biases the sensing mechanism, while the spatial arrangement of masses and coupling elements enables stable and sensitive detection of triaxial movements simultaneously
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 proposed design increases the sensor's stability and sensitivity to triaxial movements by effectively rejecting external disturbances and optimizing detection across multiple axes, improving the sensor's performance in detecting triaxial rotations.
Implementation Method 1
The driving structures may include driving electrodes, where a driving electrode converts an electrical signal to a mechanical movement of a driving mass coupled to the driving electrode. The electrical signal may be an alternating current (AC) with a resonance frequency, which results in a mechanical oscillation of the driving mass in a mechanical frequency corresponding to the resonance frequency.
Implementation Method 2
A second pair of masses are coupled to the driving masses with coupling elements, where the coupling elements transfer oscillatory movements of the driving masses to the second pair of masses with a same resonance frequency.
Implementation Method 3
The displacements can be detected based on an electrical capacitance variation. The electrical capacitance is generated by a capacitive coupling between suspended semiconductor layers that may be arranged as parallel-plate configurations, where a plurality of electrodes are fixed in parallel with the plurality of masses.
Implementation Method 4
a first spring in the first opening; a first portion that is between the first opening and the central bridge
Data Source
AI summary
A MEMS angular rate sensor is presented with two pairs of suspended masses that are micromachined on a semiconductor layer. A first pair includes two masses opposite to and in mirror image of each other. The first pair of masses has driving structures to generate a mechanical oscillation in a linear direction. A second pair of masses includes two masses opposite to and in mirror image of each other. The second pair of masses is coupled to the first pair of driving masses with coupling elements. The two pairs of masses are coupled to a central bridge. The central bridge has a differential configuration to reject any external disturbances. Each of the masses of the two pairs of masses includes different portions to detect different linear and angular movements.