MEMS Gyroscope Elastic Coupling for Quadrature Error Rejection
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Solution Overview
Problem
MEMS gyroscopes face challenges in rejecting quadrature errors due to manufacturing process variability, leading to increased costs, complexity, and time in production, as well as instability in detection signals when not rotating.
Innovation Solution
The MEMS gyroscope employs a unique elastic coupling structure with a stiff portion and compliant portions to minimize the impact of process variability, ensuring that the coupling between the mobile masses is not affected by asymmetries, thus eliminating quadrature errors without the need for additional electrodes or specialized lithographic machinery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dedicated lithographic machinery and masks are used to reduce process variability, then manufacturing precision is improved, but manufacturing cost and time increase
Solution Approach 1:
The patent applies asymmetry by intentionally designing the elastic coupling structure with different stiffness characteristics in orthogonal directions. The coupling structure is configured to be stiffer in the driving direction than in the quadrature direction, which compensates for manufacturing asymmetries and reduces quadrature error without requiring specialized lithographic processes. This asymmetric design allows standard manufacturing equipment to be used while achieving high precision.
2Measurement precision
If additional electrodes are integrated to compensate quadrature error, then measurement precision is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts the quadrature error compensation function from the electrical domain (additional electrodes) and implements it in the mechanical domain through the elastic coupling structure. By taking out the compensation mechanism from the control circuitry and embedding it in the physical coupling structure, the patent eliminates the need for additional electrodes while maintaining quadrature error compensation capability.
Solution Approach 2:
The elastic coupling structure serves as an intermediary element that mechanically couples the first and second mobile masses while simultaneously providing quadrature error compensation. This intermediary structure translates motion from the driving direction to the detection direction while filtering out quadrature components, replacing the need for electrical compensation electrodes.
3Measurement precision
If additional electrodes are integrated to compensate quadrature error, then measurement precision is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent merges the functions of elastic coupling and quadrature error compensation into a single integrated structure. The elastic coupling structure simultaneously performs mechanical coupling between masses and quadrature error compensation, eliminating the need for separate compensation electrodes and their associated manufacturing steps, thereby reducing manufacturing time.
4Measurement precision
If additional electrodes are integrated to compensate quadrature error, then measurement precision is improved, but control circuit complexity increases
Solution Approach 1:
The patent converts the harmful quadrature error into a beneficial filtering opportunity by designing the elastic coupling structure to naturally attenuate quadrature components. Instead of adding complexity to detect and correct quadrature errors electrically, the mechanical structure itself filters out the error source, simplifying the control circuit.
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 approach results in a stable output signal with reduced manufacturing complexity and costs, as the MEMS gyroscope maintains high stability of the yaw output signal without additional quadrature error compensation electrodes, and does not require dedicated lithographic machinery to improve rejection of yaw quadrature error.
Implementation Method 1
an elastic coupling structure (25) that extends between, and couples together, the first and the second mobile masses (7, 10)
Implementation Method 2
The mobile masses are capacitively coupled to the substrate through drive electrodes, which are configured to cause an oscillation of the mobile masses
Implementation Method 3
detection electrodes, which are configured to detect a displacement of the mobile masses in a detection direction
Implementation Method 4
a mobile mass that oscillates with a linear velocity in a direction perpendicular to the axis of rotation is subject to a Coriolis force directed in a direction perpendicular to the axis of rotation and to the direction of the linear velocity
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The MEMS gyroscope (1) is formed by a substrate (5), a first mass (7) and a second mass (10), wherein the first and the second masses are suspended over the substrate and extend, at rest, in a plane of extension (XY) defining a first direction (X) and a second direction (Y) transversal to the first direction. The MEMS gyroscope further has a drive structure (48) coupled to the first mass and configured, in use, to cause a movement of the first mass in the first direction, and an elastic coupling structure (25), which extends between the first mass and the second mass and is configured to couple the movement of the first mass in the first direction (X) with a movement of the second mass in the second direction (Y). The elastic coupling structure has a first portion (27, 28, 30, 31, 36, 37) having a first stiffness and a second portion (26, 33, 34) having a second stiffness greater than the first stiffness. The first portion of the elastic coupling structure extends, at rest, in the first and the second directions, and the second portion extends, at rest, in a third direction (C), in the plane of extension, transversal to the first and the second directions.