Monolithic Quartz Vibrating Beam Accelerometer for Thermal Stability
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Solution Overview
Problem
Vibrating beam accelerometers face accuracy and precision issues due to thermally induced strains caused by differential coefficients of thermal expansion between materials used in their components, particularly due to conventional bonding mechanisms like epoxy, which introduces errors in measurement.
Innovation Solution
The development of laser etched vibrating beam accelerometers where components are made from the same material, such as crystalline quartz, either monolithically formed or laser welded without adhesives, ensuring zero or reduced differences in coefficient of thermal expansion, thereby minimizing thermal-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional bonding mechanisms like epoxy are used to assemble accelerometer components, then ease of manufacture is improved, but measurement precision deteriorates due to thermal expansion differences
Solution Approach 1:
The patent merges multiple components (proof mass, resonators, flexures, dampening plates, strain isolators) into a monolithic structure formed from a single crystalline quartz substrate. This eliminates the need for bonding materials like epoxy, resolving the contradiction by achieving both manufacturing feasibility through single-material fabrication and measurement precision through zero differential thermal expansion.
Solution Approach 2:
The patent applies homogeneity by using a single material (crystalline quartz) for all accelerometer components. This ensures uniform thermal expansion characteristics throughout the entire device, eliminating measurement errors caused by differential thermal expansion between dissimilar materials while maintaining ease of manufacture through consistent material processing.
2Ease of manufacture
If multiple materials are used in accelerometer components, then ease of manufacture is improved through material selection for specific properties, but reliability deteriorates due to thermally induced strains
Solution Approach 1:
The patent combines all structural and functional components into a monolithic crystalline quartz substrate, eliminating interfaces between different materials where thermal expansion mismatches would cause stress and reliability issues. The single-material construction ensures uniform thermal response while maintaining manufacturing capability through established crystal growth and processing techniques.
Solution Approach 2:
The patent employs crystalline quartz as a composite solution that inherently provides both the mechanical properties needed for resonator operation and the thermal stability required for reliable measurement. By using this single material for all components, the patent achieves reliability through eliminated thermal stress while maintaining ease of manufacture through consistent material behavior.
3Device complexity
If adhesives are used to bond components, then device complexity is reduced through simplified assembly, but manufacturing precision deteriorates due to bonding process variations
Solution Approach 1:
The patent merges all components into a monolithic structure that is formed in a single fabrication process, completely eliminating the bonding step and associated precision issues. This approach reduces device complexity by removing adhesive layers and interfaces while simultaneously improving manufacturing precision by eliminating variability in bonding processes.
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 enhances motion sensing accuracy and robustness by eliminating thermal expansion-related errors, leading to more precise acceleration measurements in varying environmental conditions.
Implementation Method 1
Another technique is to measure the force induced in resonators as they counteract inertial forces of the proof mass. The acceleration may, for example, be determined by measuring the change in the frequencies of the resonators due to the change in load generated by the Newtonian force of a proof mass experiencing acceleration.
Implementation Method 2
the proof mass assembly may be laser etched from a single, monolithic quartz substrate
Data Source
AI summary
A proof mass assembly includes a monolithic substrate, the monolithic substrate including a proof mass, a proof mass support, and a flexure connecting the proof mass to the proof mass support. The proof mass is configured to rotate relative to the proof mass support via the flexure. The monolithic substrate further includes a first resonator connected to a first major surface of the proof mass and a first major surface of the proof mass support and a second resonator connected to a second major surface of the proof mass and a second major surface of the proof mass support.