Angular Rate Sensor Anti-Phase Coupling for Linear Acceleration Noise
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Solution Overview
Problem
Existing angular rate sensors, such as gyroscopes, are susceptible to linear acceleration noise due to in-phase parasitic modes, which are difficult to suppress effectively, leading to errors and noise in rate signals, especially in dual-mass vibratory systems with complex mechanical linkages that are prone to bending and buckling.
Innovation Solution
The design incorporates two planar proof masses suspended by flexible beams and anti-phase couplers with link springs that are stiff in the longitudinal direction and flexible in other directions, allowing for precise anti-phase movement while suppressing in-phase modes by constraining the masses for oscillation about an input axis, using comb drives and capacitive detection to monitor rotation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional coupling method with in-phase linear vibration mode is used, then the sensor structure is simple, but the sensor is susceptible to linear acceleration noise in drive direction
Solution Approach 1:
The coupling structure is segmented into multiple functional elements: arcuate coupling members for anti-phase motion coupling, stiffening beams for structural support, and flexure elements for controlled compliance. This segmentation allows each element to be optimized for its specific function while collectively achieving both structural simplicity and noise rejection.
Solution Approach 2:
The coupling members are designed with asymmetric stiffness characteristics - stiff in the longitudinal direction to suppress in-phase modes, and flexible in the transverse direction to allow anti-phase drive motion. This directional asymmetry enables selective suppression of linear acceleration susceptibility while maintaining drive mode functionality.
2Ease of operation
If arcuate coupling member is used to resist in-phase movement, then anti-phase linear movement is allowed, but the in-phase mode cannot be well suppressed due to bending and buckling under linear acceleration
Solution Approach 1:
The coupling members are pre-curved into an arcuate shape that is specifically designed to resist in-phase movement through geometric non-linearity. This preliminary geometric configuration ensures that when linear acceleration forces are applied, the arcuate shape naturally generates restoring forces that suppress in-phase modes before significant bending or buckling can occur.
Solution Approach 2:
The stiffness parameters of the coupling members are carefully optimized to provide sufficient resistance to in-phase movement while maintaining flexibility for anti-phase motion. By adjusting the arc radius, cross-sectional dimensions, and material properties, the coupling members achieve the desired balance between suppressing in-phase modes and allowing anti-phase drive motion.
3Object-affected harmful factors
If complex mechanical linkage with multiple levers and pivots is used, then in-phase translational movement is better suppressed, but the structure becomes complex and process imperfections cause unbalanced arcuate motion resulting in sense direction errors
Solution Approach 1:
The patent extracts and eliminates the complex system of multiple levers, pivots, and arcuate motion paths from the coupling structure. Instead, it uses a simplified direct coupling approach where masses are connected through stiffened beam elements that provide in-phase suppression without requiring intermediate mechanical linkages, thereby eliminating the source of unbalanced motion errors.
Solution Approach 2:
The patent replaces complex mechanical linkages with a simplified structural coupling approach using stiffened beams and flexure elements. This substitution maintains the essential mechanical coupling function while eliminating the need for multiple pivots and levers, thereby reducing sensitivity to fabrication imperfections and preventing unbalanced motion in the sense direction.
4Object-affected harmful factors
If differential processing of electrical signals is used to reject linear acceleration in sense direction, then acceleration rejection is achieved, but process imperfections prevent identical resonant frequencies resulting in un-cancelled residual error
Solution Approach 1:
The patent applies preliminary anti-action by mechanically pre-balancing the dual-mass system through symmetric coupling structures and equal-stiffness beam elements. This mechanical pre-balancing ensures that the two masses and their support structures have matched resonant frequencies before signal processing, so that differential processing can effectively cancel linear acceleration effects without leaving residual errors from frequency mismatches.
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 significantly suppresses in-phase modes, reducing linear acceleration noise and improving the accuracy of angular rate sensing by ensuring precise anti-phase movement and minimizing errors, while maintaining efficient motion transfer and robustness against fabrication imperfections.
Implementation Method 1
means for constraining the masses for anti-phase sense-mode oscillation along the sense axis in response to Coriolis forces produced by rotation of the masses about the input axis
Implementation Method 2
The design incorporates two planar proof masses suspended by flexible beams and anti-phase couplers with link springs that are stiff in the longitudinal direction and flexible in other directions
Implementation Method 3
using comb drives and capacitive detection to monitor rotation rates
Data Source
AI summary
An angular rate sensor having two generally planar proof masses, a sense axis in the plane of the masses, and an input axis perpendicular to the sense axis. The masses are suspended from a driving frame, which is mounted for torsional movement about the input axis in drive-mode. And the masses are constrained for anti-phase movement along the sense axis in sense-mode in response to Coriolis forces produced by rotation of the masses about the input axis, with sensors responsive to the anti-phase movement of the masses along the sense axis for monitoring rate of rotation.