Centrally Positioned Coupling Structures for Angular Rate Sensor
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Solution Overview
Problem
MEMS angular rate sensors are susceptible to common mode excitation due to linear and/or angular acceleration, leading to inaccuracy or failure, as they cannot effectively suppress in-phase motion of proof masses caused by external stimuli like shock and vibration.
Innovation Solution
The use of centrally positioned coupling structures between adjacent proof masses in a four-proof-mass architecture to mechanically constrain and suppress in-phase motion, maintaining symmetry and reducing the impact of accelerations, thereby enabling improved accuracy and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple proof masses are used in a vibrating structure gyroscope, then the sensor can detect angular rate through Coriolis effect, but the sensor becomes susceptible to common mode excitation from linear and angular acceleration
Solution Approach 1:
The patent employs an asymmetric four-proof-mass architecture where proof masses are arranged in a non-symmetric pattern around the sensing element. This asymmetric configuration creates differential response characteristics that allow the system to reject common mode excitation from linear and angular acceleration while maintaining sensitivity to angular rate about the sensing element axis.
Solution Approach 2:
The patent divides the proof mass system into four separate proof masses (first, second, third, and fourth proof masses) that can be independently controlled and sensed. Each proof mass is connected through separate drive couplers and sense couplers, allowing independent manipulation of their motion states to achieve common mode rejection while maintaining angular rate detection capability.
2Measurement precision
If proof masses are driven in anti-phase to sense angular rate, then Coriolis effect can be utilized for measurement, but in-phase motion from external stimuli cannot be suppressed
Solution Approach 1:
The patent incorporates feedback mechanisms through the coupling structures that connect adjacent proof masses. These coupling structures provide mechanical feedback that suppresses in-phase motion between proof masses while allowing anti-phase motion necessary for angular rate sensing. The feedback from the coupling structures actively counteracts common mode excitation.
Solution Approach 2:
The patent designs the coupling structures to preemptively counteract common mode excitation before it can affect the measurement. By pre-configuring the mechanical coupling between proof masses, the system creates restoring forces that automatically oppose in-phase motion induced by external acceleration, preventing sensor failure before it occurs.
3Reliability
If centrally positioned coupling structures are used to suppress in-phase motion, then common mode excitation is reduced, but the device structure becomes more complex
Solution Approach 1:
The coupling structures serve multiple functions simultaneously: they mechanically couple adjacent proof masses, suppress in-phase motion through common mode rejection, and maintain the anti-phase motion necessary for angular rate sensing. By making the coupling structures multi-functional, the patent reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving reliable common mode suppression.
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 centrally positioned coupling structures effectively prevent in-phase motion, enhancing the accuracy and robustness of the angular rate sensor by ensuring that the proof masses move anti-phase, thus reducing errors caused by external accelerations.
Implementation Method 1
Each coupling structure includes a first coupling portion and a second coupling portion... configured to enable anti-phase motion of the adjacent proof masses while constraining an in-phase motion of the adjacent proof masses
Implementation Method 2
In response to an external angular stimulus about an input axis, at least some of the proof masses, acting as sense masses, move in response to a Coriolis acceleration component, also referred to in the art as the Coriolis effect
Data Source
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AI summary
An angular rate sensor includes first, second, third, and fourth proof masses spaced apart from a surface of a substrate, each of the first, second, third, and fourth proof masses being configured to move along first and second transverse axes parallel to the surface of the substrate. A first coupling structure is interposed between and interconnects the first and second proof masses. A second coupling structure is interposed between and interconnects the second and third proof masses. A third coupling structure is interposed between and interconnects the third and fourth proof masses. A fourth coupling structure is interposed between and interconnects the fourth and first proof masses. The first, second, third, and fourth coupling structures are configured to constrain an in-phase motion of adjacent ones of the first, second, third, and fourth proof masses along the first and second transverse axes.