Annular Angular Rate Sensor Support Layout for Frequency Matching
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Solution Overview
Problem
Existing vibrating structure angular rate sensors face challenges with frequency splitting and reduced sensitivity due to non-linear resonant frequency shifts in the primary and secondary modes, particularly at larger amplitudes, leading to increased noise and uncertainty in angular rate measurements.
Innovation Solution
The number and arrangement of supporting structures are optimized to ensure that the resonant frequencies of the primary and secondary modes remain identical, even at large amplitudes, by selecting p such that k np ≠ integer, where k is an integer between 1 and 6 and n is the order of the primary mode of oscillation, allowing operation in a non-linear regime to enhance secondary mode oscillations and reduce measurement noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplitude of primary mode oscillation is increased to induce larger secondary mode oscillations, then measurement sensitivity improves, but resonant frequency splitting occurs due to non-linear effects
Solution Approach 1:
The patent changes the physical parameters of the supporting structures (stiffness, geometry, material properties) to modify the non-linear characteristics of the system. By adjusting these parameters, the resonant frequencies of primary and secondary modes remain matched even at large oscillation amplitudes, enabling operation in the non-linear regime without frequency splitting.
Solution Approach 2:
The patent introduces asymmetric or non-uniform supporting structures that compensate for the symmetric non-linear effects in the annular resonator. This asymmetric design creates a balance in the non-linear restoring forces, preventing the frequency splitting that would normally occur at large amplitudes.
2Stability of the object's composition
If eight supporting structures are used to elastically support the annular resonator, then structural stability is achieved, but cubic geometrical non-linearity causes frequency splitting
Solution Approach 1:
The patent modifies the parameters of the supporting structures (number, geometry, stiffness distribution) to change the non-linear characteristics. By carefully selecting these parameters, the system maintains structural stability while avoiding the cubic non-linearity that causes frequency splitting in conventional eight-leg designs.
Solution Approach 2:
The patent segments the supporting structure into multiple independent elements with different characteristics, allowing each segment to contribute differently to the overall non-linear behavior. This segmentation enables fine-tuning of the non-linear properties to achieve frequency matching without compromising structural stability.
3Reliability
If the resonator is driven in the linear regime to avoid frequency splitting, then frequency stability is maintained, but measurement sensitivity is limited
Solution Approach 1:
The patent changes the operating parameters and physical characteristics of the system to enable stable operation in the non-linear regime. By modifying the supporting structure parameters, the system achieves frequency matching at large amplitudes, allowing operation beyond the linear regime while maintaining frequency stability.
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 approach enables larger amplitude secondary mode oscillations, reducing uncertainty and noise, thereby improving the sensitivity and accuracy of angular rate sensors.
Implementation Method 1
When the sensor undergoes rotation about an axis perpendicular to the plane of the annular resonator, Coriolis forces are generated which couple energy into a secondary vibration mode
Implementation Method 2
The annular resonator is driven into a primary mode of vibration at resonance by primary drive transducers that excite the primary vibration mode
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
A vibrating structure angular rate sensor 100 comprises a substrate 114; a plurality of supporting structures 204 fixed to the substrate 114; an annular member 202 flexibly supported by the plurality of supporting structures 204; a drive system arranged to apply a periodic driving force such that the annular member 202 oscillates, in use, in a primary mode of vibration at a resonant frequency f1, with an amplitude of motion that generates a restoring force from the plurality of supporting structures 204; and a pick-off system arranged to determine the amplitude of motion of a secondary mode of vibration at a resonant frequency f2, in which oscillation of the annular member 202 is induced by the Coriolis force resulting from an angular rate experienced by the sensor 100. In use, the restoring force has a non-linear relationship with the amplitude of motion and a number p of supporting structures 204 is selected such that f1=f2.