Micromachined Accelerometer Thermal Stress Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional micromachined accelerometers are sensitive to thermal expansions and manufacturing tolerances, leading to degraded measurement quality and parasitic stresses, especially when the structure is not homogeneous in temperature, and are limited by the need for precise machining and larger dimensions for high amplification ratios.
Innovation Solution
A micromachined accelerometer design featuring two resonator measuring cells with a common mobile seismic element, connected by a mechanical member that absorbs thermal deformations, allowing the seismic masses to function as a single unit at low frequencies and reducing the impact of external thermal stresses, while maintaining compact dimensions and low production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lever arm is used to amplify the displacement of the seismic mass, then the amplification ratio is improved, but the overall dimensions of the accelerometer become greater
Solution Approach 1:
The patent transitions from a conventional lever arm configuration to a piezoelectric-based amplification system that operates in a different dimensional space. The piezoelectric elements convert mechanical stress directly into electrical signals, enabling amplification without requiring extended lever arms, thus reducing the overall device dimensions while maintaining measurement precision.
Solution Approach 2:
The patent replaces the mechanical lever arm system with a piezoelectric sensing system. Instead of using mechanical amplification through rotating arms, the invention uses piezoelectric materials that generate electrical signals in response to mechanical stress, achieving amplification through material properties rather than mechanical geometry.
2Measurement precision
If the machining quality of hinges and articulations is improved, then the measurement accuracy is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent eliminates mechanical hinges and articulations by using a direct mounting configuration where the seismic mass is connected to the piezoelectric elements through a simplified structure. This substitution of mechanical joints with a direct piezoelectric coupling system reduces the machining quality requirements while maintaining measurement accuracy.
Solution Approach 2:
The patent removes the complex hinge and articulation mechanisms from the design, extracting only the essential functional elements needed for measurement. By eliminating these problematic mechanical joints, the invention simplifies manufacturing while preserving the core measurement capability through piezoelectric sensing.
3Reliability
If the accelerometer structure is made homogeneous to reduce thermal stress, then the measurement stability is improved, but the device complexity increases
Solution Approach 1:
The patent addresses thermal stress issues by carefully selecting and optimizing the material parameters of the piezoelectric elements and their mounting structure. By adjusting material properties such as thermal expansion coefficients and elastic moduli, the design achieves thermal stability without requiring complete structural homogeneity, thus balancing reliability with manufacturing simplicity.
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 design effectively limits the interference of thermal expansions on measurements, maintains measurement accuracy, and reduces the impact of external thermal stresses without increasing production complexity or costs, while allowing the seismic masses to function like a single unit at low frequencies.
Implementation Method 1
a mechanical connecting member able to prevent, at least partly, deformations of the amplification means resulting from deformations of the accelerometer generated by external thermal stresses
Implementation Method 2
A resonator cell comprises a resonator able to vibrate and to undergo a traction or a compression
Implementation Method 3
connected to electrodes making it possible to make it vibrate at its resonant frequency
Implementation Method 4
When the accelerometer is subjected to an acceleration along the sensitive axis, the seismic mass is subjected to an inertial force which is amplified and transmitted to the force sensor
Data Source
AI summary
A micromachined accelerometer in a flat plate includes a base and at least two resonator measuring cells provided with a common mobile seismic element, the two measuring cells being placed one on each side of the common mobile seismic element along the sensitive axis of the accelerometer, such that under the effect of an acceleration, the resonator of one measuring cell undergoes a traction while the resonator of the other measuring cell undergoes a compression, the measuring cells respectively configured to amplify the acceleration force generating the translation of the common mobile seismic element provided with a respective anchoring foot-piece. The common mobile seismic element includes at least two mobile seismic masses able to be displaced in translation along the sensitive axis of the accelerometer and/or in rotation with respect to a respective axis of rotation substantially orthogonal to the sensitive axis under the effect of an acceleration along the sensitive axis.