MEMS Angular Rate Sensor Structure for Anti-Phase Motion Amplification
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Solution Overview
Problem
Existing angular rate sensors (ARS) face challenges such as large size, flexibility of rigid masses in the out-of-plane direction, incomplete decoupling of drive and sense modes, and quadrature errors due to mechanical couplings, leading to compromised functionality and performance.
Innovation Solution
The development of dual- and quad-mass tuning fork angular rate sensors with mechanical amplifiers that provide linearly coupled, anti-phase drive and sense-mode motions, minimizing energy dissipation to the substrate, and incorporating structures that suppress in-phase movements to enhance stability and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If large-size masses are used in prior art devices, then the device structure can support the required functionality, but the device becomes very large in size and the masses become flexible in the out-of-plane direction, compromising functionality
Solution Approach 1:
The device is segmented into multiple proof masses (dual-mass or quad-mass configuration) arranged in a compact tuning fork structure. This segmentation allows each mass to be smaller while collectively achieving the required mechanical properties and functionality, resolving the contradiction between structural rigidity and device size.
Solution Approach 2:
The proof masses are nested within a compact frame structure with mechanical amplifiers integrated into the same space. The tuning fork configuration allows the masses to be positioned closely together, achieving rigid mechanical coupling without increasing the overall device volume significantly.
2Device complexity
If mechanical couplings are used to connect masses and levers, then the device structure is formed, but quadrature errors occur due to residual orthogonal drive motion
Solution Approach 1:
The mechanical couplings are designed with asymmetric flexibility characteristics - highly flexible in the drive mode direction and highly rigid in the quadrature direction. This asymmetric design allows the necessary mechanical coupling for compact structure while suppressing residual orthogonal motions that cause quadrature errors, thus improving measurement precision.
3Device complexity
If drive and sense modes are mechanically coupled, then the device structure is simplified, but the modes are not entirely decoupled, leading to performance degradation
Solution Approach 1:
The mechanical amplifier structure exhibits direction-dependent mechanical properties: it provides linear coupling for anti-phase drive mode motion while being highly rigid against quadrature motions. This local quality differentiation achieves effective mode decoupling without requiring complex separate mechanisms, maintaining structural simplicity while ensuring reliable mode separation.
4Device complexity
If in-phase movements of proof masses are allowed, then the mechanical structure is simpler, but the anti-phase movement is not the fundamental resonance mode, reducing bias stability and angle random walk
Solution Approach 1:
The mechanical amplifier structure acts as a counterweight mechanism that actively suppresses in-phase movements of the proof masses through its rigid coupling in the quadrature direction. By providing mechanical opposition to in-phase motion, it ensures that anti-phase movement becomes the fundamental resonance mode, thereby improving bias stability and angle random walk 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
This design results in improved drive mode quality factor, increased rate sensitivity, enhanced signal-to-noise ratio, and better rejection of vibrations and linear accelerations, with decoupled drive and sense modes, thereby improving the angular rate sensor's precision and stability.
Implementation Method 1
The device comprises a first pair of mechanical amplifiers, each coupled to a corresponding one of the proof masses. The pair of mechanical amplifiers are configured to provide a linearly coupled, amplified anti-phase drive mode motion
Implementation Method 2
The further mechanical amplifier is configured to provide a linearly coupled, amplified anti-phase sense-mode motion. The mechanical structures that amplify Coriolis-induced movements
Implementation Method 3
The same mechanical amplifier also suppresses the in-phase movement of the frames and, consequently, of the proof masses. Suppression of the in-phase movement of the proof masses means that the anti-phase movement is left as the fundamental resonance mode of the system
Data Source
AI summary
Architectures and methods of structuring high-precision, high-stability MEMS-based angular rate sensors are provided. The structures include implements that allow the suppression of in-phase movement of the coupled masses, the mechanical enhancement of the drive movement in the driving blocks and the mechanical enhancement of the Coriolis-induced movement in the sensing blocks. Compared to the prior art, the presented architectures minimise the mechanical momenta generated by the actuation forces with the drive, sense and Q-compensation blocks. Furthermore, methods include several implements for the purpose of achieving stress-decoupling between the MEMS device and the environment and the reduction of the anchor damping.