MEMS Vibration Sensor Suspension for Mode Isolation and Shock Robustness
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Solution Overview
Problem
Traditional vibration sensor suspensions have limited ability to isolate desired vibrations from undesired modes and are prone to failure under physical shocks due to high stress concentrations at anchor points.
Innovation Solution
A microelectromechanical systems (MEMS) vibration sensor suspension design featuring an anchor assembly with integrally extending springs and a proof mass configuration that isolates vibrations in a specific plane while rejecting vibrations from other axes, incorporating a fixed electrode to lower resonance frequency and enhance robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional vibration sensor suspensions are used, then the device structure is simple, but the ability to isolate vibrations in desired mode from undesired modes is limited
Solution Approach 1:
The suspension structure is divided into multiple functional segments including anchor assemblies with integral springs, proof mass, and electrode structures. Each segment performs a specific function: anchor assemblies provide mechanical support and vibration isolation, springs provide elastic restoring force, and electrodes enable capacitive sensing. This segmentation allows optimized vibration isolation in the desired mode while maintaining manufacturability through batch processing of wafer-based components.
Solution Approach 2:
The suspension design utilizes three-dimensional geometric configurations of the springs and anchor assemblies to achieve direction-dependent vibration isolation. The springs are configured with specific orientations and spatial arrangements that provide high stiffness in undesired vibration directions while maintaining compliance in the desired sensing direction, effectively using dimensional geometry to filter vibration modes.
2Reliability
If traditional vibration sensor suspensions are used, then the manufacturing process is simple, but stress concentrations at anchor points cause breakage under physical shocks
Solution Approach 1:
The spring structures are designed with variable cross-sectional dimensions and optimized geometric parameters that reduce stress concentrations at anchor points. The springs incorporate gradual transitions and optimized thickness variations that distribute mechanical stresses more uniformly, preventing breakage under physical shocks while maintaining the batch manufacturing process for wafer-based production.
Solution Approach 2:
The suspension design incorporates compliant spring elements and energy-absorbing structural features that cushion against physical shocks before they can cause damage to the anchor points or proof mass. The springs are pre-configured with appropriate stiffness and damping characteristics to absorb impact energy, protecting the fragile anchor regions from shock-induced failure.
3Measurement precision
If the suspension isolates vibrations effectively, then sensitivity to desired vibrations is improved, but space requirements increase
Solution Approach 1:
The suspension utilizes thin-film spring structures and membrane-based anchor assemblies that provide the necessary mechanical compliance and vibration isolation with minimal material volume. These thin-film structures achieve high aspect ratios, providing sufficient elastic deformation capability for sensitive vibration detection while occupying minimal space within the sensor package.
Solution Approach 2:
The electrode structures and suspension components are arranged in nested or overlapping configurations that maximize the use of available space. The fixed electrodes are positioned adjacent to the proof mass in a capacitive arrangement that allows the sensing field to extend through the same physical space occupied by the suspension structure, effectively utilizing three-dimensional space efficiently.
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 suspension effectively isolates desired vibrations while rejecting undesired modes, increasing robustness against physical shocks and optimizing space and sensitivity by achieving a resonance frequency ratio of about one-third for the primary vibration mode compared to other modes, and absorbing external stresses effectively.
Implementation Method 1
Each spring comprises a first section integrally extending at a first end away from the anchor body to a second end
Implementation Method 2
incorporating a fixed electrode to lower resonance frequency and enhance robustness
Data Source
AI summary
An anchor assembly for a microelectromechanical systems (MEMS) vibration sensor suspension comprises an anchor body and at least one spring integrally extending from the anchor body. Each spring comprises a first section integrally extending at a first end away from the anchor body to a second end, and first lateral portions of second and third sections extending in opposite lateral directions from the second end. Each of the second and third sections includes a first leg that extends at a first end from the first lateral portion toward the anchor body, a second lateral portion that extends from a second end of the first leg away from the first section, and a second leg that extends from the second lateral portion at a first end away from the anchor body, wherein second ends of the second legs extend farther from the anchor body than the first lateral portions.