Vibrating Structure Gyroscope Transducer Configuration
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Solution Overview
Problem
Vibrating structure angular rate sensors, particularly those using MEMS technology, face challenges in noise performance due to the noise dominance of sensing amplifiers in secondary pick-off sensing transducers, which affects accuracy in measuring angular rates.
Innovation Solution
The configuration is modified by using an odd number of secondary pick-off and drive transducers, with a single secondary drive transducer instead of a pair, allowing an additional secondary pick-off transducer to enhance the signal-to-noise ratio without adding noise from a second amplifier, and signals from multiple pick-off transducers are summed for improved noise rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an additional secondary pick-off transducer is added to improve signal-to-noise ratio, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by configuring transducers to serve multiple roles. Specifically, the secondary pick-off transducers are arranged such that they can detect both Coriolis-induced vibration (for angular rate measurement) and shock-induced vibration (for shock measurement), eliminating the need for separate dedicated transducers for each function and reducing overall device complexity while maintaining improved signal-to-noise ratio
Solution Approach 2:
The patent merges the functions of angular rate sensing and shock sensing into a unified transducer system. By combining the secondary pick-off transducers to serve both Coriolis detection and shock detection purposes, the invention reduces the total number of transducers required compared to having separate dedicated transducers for each function, thus improving signal-to-noise ratio without proportionally increasing device complexity
2Measurement precision
If diametrically opposed transducer pairs are used to cancel perturbing signals, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent employs asymmetric transducer configuration where secondary pick-off transducers are positioned at non-diametrically-opposed locations (e.g., 90 degrees apart rather than 180 degrees). This asymmetric arrangement provides sufficient noise rejection capability while simplifying the overall transducer configuration and reducing the complexity associated with implementing perfect diametrically opposed pairs
3Measurement precision
If multiple secondary pick-off transducers are used to improve signal-to-noise ratio, then measurement precision is improved, but the number of components increases
Solution Approach 1:
The patent applies multi-functionality by configuring transducers to serve multiple roles. Specifically, the secondary pick-off transducers are arranged such that they can detect both Coriolis-induced vibration (for angular rate measurement) and shock-induced vibration (for shock measurement), eliminating the need for separate dedicated transducers for each function and reducing overall device complexity while maintaining improved signal-to-noise ratio
Solution Approach 2:
The patent implements self-service by designing the transducer system to automatically serve multiple functions without requiring additional dedicated components. The secondary pick-off transducers inherently provide both Coriolis detection and shock detection capabilities through their positioning and signal processing configuration, eliminating the need for separate transducer sets and reducing the total component count while maintaining improved measurement precision
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 improves the signal-to-noise ratio by up to 3/2, reducing noise levels and enhancing accuracy in angular rate measurements, particularly in static or low-shock environments, as demonstrated by reduced Allan Deviation over averaging time.
Implementation Method 1
at least one primary drive transducer arranged to cause the ring structure to oscillate in a primary mode at the resonant frequency of the primary mode
Implementation Method 2
These angular rate sensors may be actuated using capacitive, piezoelectric or electromagnetic transducers
Implementation Method 3
When a rotation is applied around an axis perpendicular to the plane of the ring, Coriolis forces couple energy into a secondary mode of vibration, with the amplitude of the vibration being proportional to the applied angular rate
Implementation Method 4
In this 'force-feedback' mode of operation, the applied nulling force is directly proportional to the applied angular rate, allowing the rate of angular motion experienced by the angular rate sensor to be determined
Implementation Method 5
Due to the compliant nature of the supporting structures, the planar ring may move elastically relative to the silicon mount, for example when deformed by an applied force
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
A vibrating structure angular rate sensor comprises a MEMS structure (10) comprising a mount, a plurality of supporting structures fixed to the mount, and a vibrating planar ring structure flexibly supported by the plurality of supporting structures to move elastically relative to the mount. At least one primary drive transducer (41a,41b) is arranged to cause the ring structure to oscillate in a primary mode at the resonant frequency of the primary mode. At least one primary pick-off transducer (42a,42b) arranged to detect oscillation of the ring structure in the primary mode. At least three secondary pick-off transducers (43a,43b,43c) are arranged to detect oscillation of the ring structure in a secondary mode induced by Coriolis force when an angular rate is applied around an axis substantially perpendicular to the ring structure. At least one secondary drive transducer (44b) is arranged to null the induced oscillation in the secondary mode. The number of secondary pick-off transducers (43a,43b,43c) and the number of secondary drive transducers (44b) is an odd number, wherein the number of secondary drive transducers (44b) is smaller than the number of secondary pick-off transducers (43a,43b,43c).