2-DOF Drive MEMS Gyroscope for Gain-Bandwidth Tradeoff
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Solution Overview
Problem
Conventional micromachined vibratory gyroscopes face challenges in achieving robustness and sensitivity while maintaining operational frequencies above several kHz and mechanical bandwidths above 100 Hz, due to limitations in design space and tradeoffs between robustness, bandwidth, and gain.
Innovation Solution
A 3-degree of freedom dynamic gyroscope system with a 1-DOF drive-mode and 2-DOF sense-mode, featuring a symmetrically-decoupled suspension subsystem that optimally places the operational frequency between sense-mode resonant peaks, allowing for flexible selection of bandwidth and high operational frequencies, and utilizing capacitive electrodes for actuation and detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mode-matched operation is used to increase sensitivity, then mechanical gain is improved, but temperature bias drift and bandwidth deteriorate
Solution Approach 1:
The patent transitions from conventional single-DOF drive and sense modes to a 2-DOF drive mode and 1-DOF sense mode configuration. This dimensional change in the drive mode provides additional design freedom to decouple the sensitivity enhancement from temperature drift penalties, allowing the system to achieve high mechanical gain without being locked into mode-matched operation that causes temperature bias drift.
Solution Approach 2:
The patent employs parametric excitation of the drive mode to achieve large amplitudes over a wide frequency range. By changing the excitation parameters and utilizing the 2-DOF drive mode structure, the system can maintain high sensitivity across varying temperatures without the fixed frequency constraints that cause temperature drift in mode-matched designs.
2Reliability
If operational frequency is increased to suppress environmental vibrational noise, then robustness is improved, but bandwidth deteriorates
Solution Approach 1:
The 2-DOF drive mode introduces an additional degree of freedom that enables the system to operate at high frequencies while maintaining bandwidth. The extra dimension provides flexibility in shaping the frequency response, allowing high operational frequencies for noise suppression while preserving adequate bandwidth through the coupled dynamics of the two drive modes.
3Speed
If 2-DOF sense-mode is used to increase bandwidth, then robustness is improved, but gain deteriorates due to peak spacing constraints
Solution Approach 1:
The patent inverts the conventional configuration by placing the 2-DOF in the drive mode rather than the sense mode. This dimensional reassignment allows the sense mode to maintain a simple 1-DOF structure with high gain, while the 2-DOF drive mode provides the bandwidth and robustness benefits. The drive mode's additional degree of freedom compensates for any gain reduction, overall improving system performance.
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 solution provides increased gain and sensitivity, improved temperature robustness, and optimal gain-bandwidth characteristics, enabling the gyroscope to operate effectively in various applications such as camera stabilization and navigation systems while minimizing the impact of fabrication imperfections.
Implementation Method 1
The operation of all micromachined vibratory gyroscopes is based on a transfer of energy between two modes of vibration caused by the Coriolis effect.
Implementation Method 2
utilizing capacitive electrodes for actuation and detection
Data Source
AI summary
The current invention is a novel gyroscope design, which yields devices robust to fabrication and environmental variations, allows flexible selection of operational parameters, and provides increased bandwidth with minimized sacrifice in gain regardless of the selected frequency of operation. The gyroscope has a single degree-of-freedom (DOF) drive-mode and a 2-DOF sense-mode. The drive-mode operational frequency and the sense-mode bandwidth can be selected arbitrarily in the proposed design, relaxing the tradeoff between the gain, die size, and detection capacitance. The symmetry of the structure ensures the optimal location of the drive-mode resonance relative to the sense-mode operational region, even in presence of fabrication imperfections.