Folded Spring MEMS Gyroscope Resonant Frequency Matching
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Solution Overview
Problem
MEMS gyroscope designs face challenges in achieving identical resonant frequencies for rotary elements and frames, leading to reduced sensitivity and accuracy due to manufacturing variations in torsion beams and folded springs, which also hinder miniaturization of micro-electromechanical apparatus.
Innovation Solution
A micro-electromechanical apparatus utilizing a rotary element connected by symmetrically disposed folded springs with varying spring lengths, where the moving and fixed ends are not on the axis, allowing for rotation and maintaining proportional stiffness to ensure resonant frequency matching between the rotary element and frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional torsion beam structures are used to enable rotary element rotation, then the apparatus can achieve rotational movement, but the dimension of the micro-electromechanical apparatus cannot be miniaturized due to the required length of the torsion beam
Solution Approach 1:
The patent divides the continuous torsion beam into multiple discrete folded spring segments. Each folded spring consists of multiple spans connected in sequence, creating a segmented structure that replaces the traditional single-piece torsion beam. This segmentation allows the structure to achieve the required rotational flexibility while occupying significantly less space, enabling miniaturization of the overall apparatus.
Solution Approach 2:
The patent transitions from a one-dimensional linear torsion beam to a multi-dimensional folded spring structure. The folded springs are arranged symmetrically about the rotation axis with their spans extending in directions parallel to the axis, utilizing three-dimensional space more efficiently. This dimensional transformation allows the rotational function to be achieved within a compact volume, solving the miniaturization problem.
2Measurement precision
If the stiffness of folded spring is increased to match resonant frequencies, then resonant frequency consistency is improved, but manufacturing precision requirements increase due to the cubic relationship between spring width and stiffness
Solution Approach 1:
The patent employs asymmetric design in the folded spring structure where the moving end and fixed end are positioned at different distances from the rotation axis (moving distance ≠ fixed distance). This asymmetric configuration allows independent optimization of the spring's mechanical properties. By carefully designing the asymmetric geometry, the spring can achieve the required stiffness for resonant frequency matching while maintaining manufacturing tolerances that are practical to achieve.
Solution Approach 2:
The patent utilizes parameter changes in the folded spring design, specifically varying the spring length, span lengths, and attachment distances to optimize the stiffness characteristics. The spring length is defined as the distance between the moving end and a reference point of the fixed end, and this parameter can be adjusted to achieve the desired resonant frequency matching without requiring extreme manufacturing precision.
3Measurement precision
If the spring length is varied according to rotation to maintain resonant frequency matching, then sensitivity and accuracy are improved, but the structural complexity increases due to the asymmetric positioning of ends
Solution Approach 1:
The folded spring structure serves multiple functions simultaneously: it provides rotational support for the rotary element, acts as a suspension mechanism, and functions as a spring element for resonant frequency matching. The same asymmetric structure that creates the varied spring length during rotation also provides the necessary mechanical support and flexibility. This multi-functionality reduces the need for additional components, thereby limiting the increase in overall structural complexity.
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 enhances the sensitivity and accuracy of MEMS gyroscope by maintaining resonant frequency consistency and enabling miniaturization without compromising the rotational frequency of the rotary element.
Implementation Method 1
Each folded spring has a moving end and a fixed end, the moving end is connected to the rotary element, and the fixed end is connected to the at least one restraint. The spring length is varied according to rotation of the rotary element.
Data Source
AI summary
A micro-electromechanical apparatus includes a rotary element, at least one restraint and at least two folded springs. The rotary element is capable of rotating with respect to an axis. The folded springs are symmetrically disposed about the axis. Each folded spring has a moving end and a fixed end, the moving end is connected to the rotary element, and the fixed end is connected to the at least one restraint. The moving end is not located on the axis, and the fixed end is not located on the axis. A moving distance is defined as a distance between the moving end and the axis, a fixed distance is defined as a distance between the fixed end and the axis. A spring length is defined as a distance between the moving end and the fixed end. The spring length is varied according to the rotation of the rotary element.