MEMS Gyroscope Spring System for Vibration Robustness
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Solution Overview
Problem
MEMS gyro sensors are susceptible to instability and malfunction due to parasitic modes of vibration excited by shock and vibration, which impair their output signals.
Innovation Solution
The design incorporates two movable masses with couple springs that allow independent adjustment of drive and sense frequencies, pushing parasitic modes of vibration to higher frequencies, thereby reducing the likelihood of excitation and enhancing robustness against shock and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MEMS gyro sensors use suspended vibrating structures, then they can sense angular rotation, but they become susceptible to shock and vibration causing parasitic modes of vibration
Solution Approach 1:
The patent changes the frequency parameter of the suspended structure by designing specific suspension structures with tuned stiffness and mass distribution. This shifts the natural frequencies of parasitic modes away from excitation frequencies caused by shock and vibration, thereby reducing their impact on sensor reliability
Solution Approach 2:
The patent employs dynamic vibration isolation techniques where the suspension structure is designed to dynamically respond to and isolate the sensing element from external shocks and vibrations. The suspension system acts as a dynamic filter that allows desired angular rotation sensing while attenuating harmful vibrational modes
2Stability of the object's composition
If parasitic modes of vibration are excited by shock, then instability and malfunction occur, but increasing structural stiffness to suppress vibration may affect sensor sensitivity
Solution Approach 1:
The patent applies local quality by designing the suspension structure with non-uniform stiffness distribution. Different regions of the suspension structure have different stiffness characteristics - some regions are optimized for vibration suppression while others maintain sensitivity for angular rate detection. This localized optimization allows simultaneous achievement of structural stability and measurement precision
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 reduces the number of parasitic modes and increases their frequencies, making it harder to excite them, thus enhancing the reliability of the MEMS angular rate sensor in the presence of external disturbances.
Implementation Method 1
a spring system located in the opening... wherein the movable mass is resiliently suspended above the surface of the substrate via the suspension structure and the spring system, the spring system enabling drive motion of the movable mass in the drive direction
Implementation Method 2
the spring system enabling sense motion of the movable mass in the sense direction that is perpendicular to the surface of the substrate
Implementation Method 3
a first rigid link coupled to and extending from a first side of the anchor, and a second rigid link coupled to and extending from a second side of the anchor, each of the first and second rigid links having a lengthwise dimension oriented perpendicular to a drive direction of the movable mass
Data Source
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AI summary
A MEMS device includes a movable mass having a central region overlying a sense electrode and an opening in which a suspension structure and spring system are located. The suspension structure includes an anchor coupled to a substrate and rigid links extending from opposing sides of the anchor. The spring system includes a first and second spring heads coupled to each of the rigid links. A first drive spring is coupled to the first spring head and to the movable mass, and a second drive spring is coupled to the second spring head and to the movable mass. The movable mass is resiliently suspended above the surface of the substrate via the suspension structure and the spring system. The spring system enables drive motion of the movable mass in the drive direction and sense motion of the movable mass in a sense direction perpendicular to the surface of the substrate.