MEMS Tri-Axial Accelerometer Suspension With Decoupled Vibrational Modes
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Solution Overview
Problem
Current MEMS tri-axial accelerometers face challenges in reducing size and manufacturing costs while maintaining sensitivity and optimizing resonance frequencies across multiple sensing directions, due to the use of single elastic elements that are limited by adhesion forces and non-optimized vibrational modes.
Innovation Solution
A MEMS tri-axial accelerometer design featuring a single inertial mass with decoupling elements that allow independent optimization of vibrational modes in each sensing direction, using a suspension structure with decoupling elements to decouple sensing movements and elastic elements that are compliant to different types of motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single elastic suspension element is used to suspend the sensing mass, then the area occupation and manufacturing costs are reduced, but the mechanical sensitivity decreases and the vibrational modes cannot be independently optimized
Solution Approach 1:
The suspension structure is segmented into multiple elastic suspension elements (first, second, third elements) with distinct functions. The first element provides primary suspension, the second element provides additional suspension and decoupling, and the third element provides further decoupling. This segmentation allows each element to be optimized for specific vibrational modes while maintaining compact area occupation.
2Ease of manufacture
If a single elastic suspension element is used, then manufacturing costs are reduced, but the vibrational modes cannot be independently optimized for each sensing direction
Solution Approach 1:
Each elastic suspension element is designed with specific local properties optimized for particular sensing directions. The first element is optimized for one axis, the second for another axis, and the third for the vertical axis. This local quality approach enables independent optimization of vibrational modes for each sensing direction while using a unified manufacturing process.
3Area of moving object
If the mass of the sensing mass is reduced to decrease area occupation, then the area is reduced, but the mechanical sensitivity decreases
Solution Approach 1:
The suspension structure uses composite elastic elements with different stiffness characteristics. By combining multiple elements with different mechanical properties, the system achieves high sensitivity with reduced mass, as each element contributes differently to the overall mechanical response and decoupling of vibrational modes.
4Measurement precision
If multiple sensing masses are used for each sensing direction, then each sensing mass can be optimized for its specific direction, but the area occupation and manufacturing complexity increase
Solution Approach 1:
Multiple sensing functions are merged into a single sensing mass by using multiple elastic suspension elements with decoupling capabilities. The first, second, and third elements work together to enable independent optimization of vibrational modes for three different sensing directions, achieving the functionality of multiple separate sensing masses while occupying less area.
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 design achieves compact size, reduced manufacturing costs, and optimized sensitivity by allowing independent optimization of vibrational modes, ensuring similar resonance frequencies across sensing directions.
Implementation Method 1
elastic suspension elements, configured to ensure one or more degrees of freedom for the inertial movement of the sensing masses
Implementation Method 2
capacitive variation of the capacitor formed between the mobile electrodes and the fixed electrodes, thus generating an electrical quantity that is variable as a function of the acceleration to be detected
Implementation Method 3
optimized sensitivity by allowing independent optimization of vibrational modes, ensuring similar resonance frequencies across sensing directions
Data Source
AI summary
A MEMS tri-axial accelerometer is provided with a sensing structure having: a single inertial mass, with a main extension in a horizontal plane defined by a first horizontal axis and a second horizontal axis and internally defining a first window that traverses it throughout a thickness thereof along a vertical axis orthogonal to the horizontal plane; and a suspension structure, arranged within the window for elastically coupling the inertial mass to a single anchorage element, which is fixed with respect to a substrate and arranged within the window, so that the inertial mass is suspended above the substrate and is able to carry out, by the inertial effect, a first sensing movement, a second sensing movement, and a third sensing movement in respective sensing directions parallel to the first, second, and third horizontal axes following upon detection of a respective acceleration component. In particular, the suspension structure has at least one first decoupling element for decoupling at least one of the first, second, and third sensing movements from the remaining sensing movements.