Multi-Axis Resonant Accelerometer with Orthogonal Proof Masses
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Solution Overview
Problem
Current resonant micro-accelerometers are primarily uniaxial or biaxial, limiting their functionality to one or two dimensional motion control, and increasing cost, size, and power requirements when attempting to measure three-dimensional acceleration, which requires precise alignment of separate accelerometers.
Innovation Solution
A compact, single-device multi-axis accelerometer design featuring two orthogonally aligned proof masses and resonant element assemblies, fabricated from a single semiconductor material, with flexures and resonant elements that minimize cross-talk and allow for accurate three-dimensional acceleration measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If three uniaxial accelerometers are used for three-dimensional acceleration measurement, then measurement capability is improved, but device size, cost, and power requirements increase
Solution Approach 1:
The patent combines three separate uniaxial accelerometer functions into a single integrated device by suspending three proof masses from a common frame structure, sharing common components including the frame, flexures, and resonant element assemblies, thereby achieving three-dimensional acceleration measurement while reducing overall device size and component quantity
Solution Approach 2:
The common frame structure serves multiple functions simultaneously: it provides structural support for all three proof masses, acts as a reference frame for acceleration measurements, and houses the resonant element assemblies. This multi-functional design reduces the number of separate components needed
2Measurement precision
If three separate uniaxial accelerometers are used, then three-dimensional measurement capability is improved, but alignment precision requirements increase
Solution Approach 1:
By integrating three accelerometer functions into a single device with a common frame and shared components, the patent eliminates the need for precise alignment between separate devices. The orthogonally arranged proof masses are inherently aligned through the common frame structure, significantly reducing manufacturing alignment requirements
3Device complexity
If a compact single-device design is used, then device size is reduced, but cross-talk between measurement axes may increase
Solution Approach 1:
The patent segments the measurement system into three independently suspended proof masses, each responsive to acceleration along a specific orthogonal axis. This physical segmentation isolates the measurement functions, minimizing cross-talk between axes while maintaining a compact integrated structure through shared common components
Solution Approach 2:
Each proof mass and its associated resonant element assembly are designed with specific local characteristics optimized for their respective measurement axes. The flexures provide axis-specific mechanical coupling, ensuring that each sensor responds primarily to acceleration along its designated axis while reducing sensitivity to accelerations along other axes
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
Enables accurate two and three-dimensional acceleration measurement in a single, small, and robust device with minimized cross-talk between axes, facilitating applications like gravimetry and reducing manufacturing complexity.
Implementation Method 1
a first resonant element assembly fixed between the frame and the first proof mass, wherein movement of the proof mass along the first axis relative to the frame exerts a strain on the first resonant element that affects the resonant behaviour of the first resonant element assembly
Data Source
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AI summary
There is provided an accelerometer comprising: a frame; a first proof mass suspended from the frame by one or more flexures to move relative to the frame along a first axis; a first resonant element assembly fixed between the frame and the first proof mass, wherein movement of the proof mass along the first axis relative to the frame exerts a strain on the first resonant element that affects the resonant behaviour of the first resonant element assembly; a second proof mass suspended from the frame by one or more flexures to move relative to the frame along a second axis, a second resonant element assembly fixed between the frame and the second proof mass, wherein movement of the second proof mass along the second axis relative to the frame exerts a strain on the second resonant element that affects the resonant behaviour of the second resonant element assembly; wherein the second proof mass surrounds the first proof mass and the first resonant element assembly.