Shared-Cavity Acoustic Resonators for Precise Stress Sensing
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Solution Overview
Problem
Differential acoustic wave sensors face challenges in accurately measuring stress due to inhomogeneities in the material, leading to errors in stress determination, as each resonator measures at a different location and is sensitive to temperature and vibration effects.
Innovation Solution
The resonator device comprises at least two resonators with inter-digitated transducers and reflecting structures on a piezoelectric substrate, positioned to have different wave propagation directions and share a cavity, using materials and geometries that optimize electro-mechanical coupling and reflectivity, allowing for improved temperature stability and reduced sensitivity to temperature and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If each resonator measures at a different location, then the device complexity is reduced, but the measurement precision deteriorates due to material inhomogeneities
Solution Approach 1:
The patent merges the measurement locations of multiple resonators by positioning them to share a common cavity region. This allows all resonators to measure stress at the same location, eliminating errors from material inhomogeneities while maintaining a compact integrated structure rather than requiring separate measurement points
2Measurement precision
If resonators are positioned with different wave propagation directions, then the sensitivity to stress is improved, but the device complexity increases due to additional positioning requirements
Solution Approach 1:
The patent applies local quality by assigning different propagation directions to different resonators within the same device. Each resonator is oriented to be sensitive to specific stress components, creating localized measurement capabilities that together provide comprehensive stress analysis with improved precision
3Volume of moving object
If a shared cavity is used by multiple resonators, then the device compactness is improved, but the reliability deteriorates due to potential interference between resonators
Solution Approach 1:
The patent segments the resonator structures so that each resonator has its own transducer and reflecting structures, while only the cavity region is shared. This segmentation maintains measurement reliability by preserving independent resonator functionality while achieving compactness through shared cavity space
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 enables accurate stress measurement by segregating the origin of perturbations, reducing errors from material inhomogeneities and other stimuli, while allowing for compact design and improved sensitivity to stress, particularly in high-temperature environments.
Implementation Method 1
Acoustic wave sensors utilize the piezoelectric effect to transduce an electrical signal into a mechanical/acoustic wave. An inter-digitated transducer (IDT) converts the electrical energy of an incident electrical signal into acoustic wave energy.
Implementation Method 2
In some devices, the other (output) IDT is replaced by a reflector that reflects the generated acoustic wave back to the (input) IDT
Implementation Method 3
A particular class of acoustic sensors comprises resonators exhibiting resonator frequencies that vary according to varying ambient conditions. At the resonance frequency, the condition of synchronism between the reflectors is satisfied making it possible to obtain a coherent addition of the different reflections
Data Source
AI summary
A resonator device for measuring stress comprises at least two resonators, each resonator comprising an inter-digitated transducer structure arranged between two reflecting structures on or in a piezoelectric substrate, wherein the at least two resonators are arranged and positioned such that they have two different wave propagation directions, and each resonator comprises at least two parts with the area between the two parts of the at least two resonators forming a cavity, wherein the cavity is shared by the at least two resonators and wherein for at least one resonator, in particular, all resonators, the inter-digitated transducer structure comprises a first material and the reflecting structures a second material different from the first material and/or the inter-digitated transducer structure and the reflecting structures have different geometrical parameters. A differential sensing device comprises at least one resonator device as described herein.