MEMS Gyroscope Detection Structure with Compensating Masses
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Solution Overview
Problem
MEMS gyroscopes face issues with undesirable cross-talk between detection structures, vibrations, and sensitivity to external stresses due to non-zero resultant forces and torques exerted on the substrate by moving masses during driving movements, leading to instability and inaccurate readings.
Innovation Solution
The detection structure is designed with specific arrangements of driving and driven masses, and elastic coupling elements that generate compensating torques and forces, resulting in a substantially zero resultant of forces and torques on the substrate, thereby minimizing unwanted interactions and stabilizing the sensor device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If moving masses are driven in linear direction to detect angular velocity via Coriolis force, then measurement capability is improved, but resultant forces and torques on substrate become non-zero causing cross-talk and vibrations
Solution Approach 1:
The patent introduces compensating masses arranged symmetrically with respect to the driving masses. These compensating masses are elastically coupled to the substrate and generate counterbalancing forces and torques that offset the resultant forces produced by the driving masses during linear oscillation, thereby eliminating cross-talk and vibrations on the substrate while preserving Coriolis force detection capability
Solution Approach 2:
The patent employs asymmetric arrangement of driving and driven masses relative to the substrate center, where driving masses are positioned to generate Coriolis force in the detection direction while compensating masses are positioned to generate counterbalancing torques. This asymmetric configuration allows independent optimization of measurement sensitivity and substrate force balance
2Measurement precision
If driving masses are oscillated to generate Coriolis force for detection, then detection sensitivity is improved, but torques on substrate increase causing instability
Solution Approach 1:
Compensating masses are elastically coupled to the substrate and positioned to generate counterbalancing torques that offset the torques produced by oscillating driving masses. This counterweight mechanism stabilizes the substrate by maintaining near-zero net torque during detection operation, preventing instability while preserving detection sensitivity
Solution Approach 2:
Elastic coupling elements serve as intermediaries between the driving/driven masses and the substrate. These elements transmit necessary forces for detection while filtering and isolating harmful torques and vibrations from reaching the substrate, thereby maintaining both sensitivity and stability
3Ease of operation
If elastic elements are used to support mobile mass, then measurement function is enabled, but transmission of stresses to substrate occurs
Solution Approach 1:
Elastic coupling elements are introduced as intermediary components between the moving masses and the substrate. These elements enable the measurement function by supporting and coupling the mobile mass while simultaneously filtering and isolating stress transmissions, preventing harmful stresses from reaching the substrate and package
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 configuration prevents transmission of undesirable stresses to the substrate and package, reducing cross-talk, vibrations, and sensitivity to external stresses, enhancing the stability and accuracy of the MEMS sensor device.
Implementation Method 1
When an angular velocity is applied to a mobile mass that is driven in a linear direction, the mobile mass is subject to an apparent force, or Coriolis force, which determines a displacement thereof in a direction perpendicular to the linear driving direction and to the axis about which the angular velocity is applied.
Implementation Method 2
The displacement of the mobile mass may, for example, be detected via a capacitive transduction system, determining the variations of capacitance between mobile electrodes, which are fixed with respect to the mobile mass, and fixed electrodes, which are fixed with respect to the substrate.
Implementation Method 3
The mobile mass is supported above a substrate via elastic elements that enable driving thereof in the driving direction and displacement in the direction of the apparent force, which is directly proportional to the angular velocity.
Data Source
AI summary
A micromechanical detection structure includes a substrate of semiconductor material and a driving-mass arrangement is coupled to a set of driving electrodes and driven in a driving movement following upon biasing of the set of driving electrodes. A first anchorage unit is coupled to the driving-mass arrangement for elastically coupling the driving-mass arrangement to the substrate at first anchorages. A driven-mass arrangement is elastically coupled to the driving-mass arrangement by a coupling unit and designed to be driven by the driving movement. A second anchorage unit is coupled to the driven-mass arrangement for elastically coupling the driven-mass arrangement to the substrate at second anchorages. Following upon the driving movement, the resultant of the forces and of the torques exerted on the substrate at the first and second anchorages is substantially zero.