Circular Synchronization Structure for Z-Axis MEMS Gyroscope Vibration
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Solution Overview
Problem
Z-axis MEMS gyroscopes face challenges in suppressing common-mode oscillations induced by external vibrations, which can disturb angular rate measurements due to the difficulty in designing suspension arrangements that are perfectly flexible for desired oscillation modes while being rigid for undesired ones, leading to coupling of external vibrations with desired modes.
Innovation Solution
A substantially circular synchronization structure is placed at the center of the gyroscope, suspended with tangentially oriented linear suspenders that allow only elliptical deformation corresponding to desired oscillation modes, effectively suppressing linear and rotational common-mode oscillations while allowing drive and sense oscillations to proceed undisturbed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If suspension arrangements are designed to be perfectly flexible for desired oscillation modes, then resonant frequencies are achieved for desired modes, but external vibrations can easily cause disturbances due to lack of rigidity for undesired modes
Solution Approach 1:
The suspension system is segmented into multiple suspenders (first suspenders for drive mode, second suspenders for sense mode) with different flexibility characteristics. Each suspender group is optimized for specific oscillation modes, allowing the system to achieve desired resonant frequencies while providing differential flexibility to suppress common-mode vibrations through segmented functional specialization.
2Device complexity
If a single proof mass is used, then device complexity is reduced, but the gyroscope is more vulnerable to disturbances from external vibrations
Solution Approach 1:
The proof mass is configured with a center of gravity offset from the rotation axis, creating a counterbalancing effect. This offset configuration generates anti-phase motion components that automatically cancel out common-mode disturbances induced by external vibrations, providing passive vibration rejection without increasing device complexity.
3Reliability
If synchronization arrangement suppresses common-mode oscillation, then measurement robustness is improved, but device complexity and area increase
Solution Approach 1:
The synchronization arrangement is designed to perform multiple functions simultaneously: it synchronizes differential-mode oscillations to maintain measurement accuracy, suppresses common-mode vibrations for robustness, and serves as a structural support element. This multi-functionality allows common-mode suppression without proportionally increasing device 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
This arrangement effectively suppresses all linear and rotational common-mode oscillations, maintaining the integrity of angular rate measurements while minimizing the area and cost contribution near the gyroscope's center.
Implementation Method 1
If the gyroscope undergoes angular rotation about the z-axis, which is perpendicular to the substrate plane, the resulting sense or secondary oscillation induced by the Coriolis force also will also occur in the substrate plane.
Implementation Method 2
The partly mobile proof masses, which constitute the rotation-sensitive elements of the gyroscope, may be suspended from a fixed structure by suspenders which are configured to flexibly allow oscillating drive motion and sense motion at a desired resonant frequency.
Data Source
AI summary
A microelectromechanical z-axis gyroscope which comprises a proof mass system centred around a gyroscope center point. The oscillation of first and second proof mass pairs is synchronized by a substantially circular synchronization element which is centred at the gyroscope center point and comprises four first attachment points. Each proof mass is attached to the nearest first attachment point on the substantially circular synchronization element. The substantially circular synchronization element also comprises two or more second attachment points, and a substantially linear suspender extends tangentially from each second attachment point to an anchor point.