Accelerometer Flexible Mounting Structure Isolates Thermal Strain
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Solution Overview
Problem
Accelerometers face bias errors due to thermal and mounting strains caused by the coupling of thermal and mounting stresses to the flexures, which degrades their sensitivity and performance.
Innovation Solution
The design incorporates a flexure member with a pendulum member pivotably connected to a support member via a hinge arrangement, and a housing with mounting structures that allow differential movement between the support member and the housing, specifically in directions orthogonal to the sensing axis, to isolate the pendulum from strain effects and absorb thermal strains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the support ring is clamped rigidly in position, then the structural stability is improved, but thermal strains and mounting strains are coupled to the flexures causing bias sensitivity and measurement error
Solution Approach 1:
The mounting structure is segmented into multiple independent mounting posts distributed around the support ring, allowing localized differential movement while maintaining overall structural stability. Each mounting post can independently accommodate thermal and mounting strains without transmitting them to the flexures.
Solution Approach 2:
The mounting posts are designed with non-uniform cross-sections or material properties to provide different stiffness characteristics in different directions. This allows the structure to be rigid in the sensing axis direction while being compliant in orthogonal directions to accommodate thermal expansion and mounting strains.
2Reliability
If the support member is rigidly fixed to the housing, then the mounting stability is improved, but differential movement is prevented causing strain coupling to the pendulum member
Solution Approach 1:
The mounting posts serve as intermediary elements between the support member and housing. These intermediaries provide a compliant connection that allows differential movement to be absorbed without directly coupling strains to the sensitive pendulum member, while still maintaining reliable mounting.
Solution Approach 2:
The mounting structure transitions from a static rigid connection to a dynamic compliant connection. The mounting posts are designed to deform elastically under thermal and mounting loads, allowing the support member to move differentially relative to the housing while maintaining stable attachment.
3Measurement precision
If flexible mounting structures are used to allow differential movement, then thermal strain decoupling is improved, but the device complexity increases
Solution Approach 1:
The mounting posts are designed as flexible beam-like structures with controlled cross-sections that provide the necessary compliance for thermal expansion while maintaining structural integrity. These flexible elements achieve strain decoupling through their geometric design rather than complex mechanical mechanisms.
Solution Approach 2:
The mounting structure may use composite materials or material gradients to achieve the desired combination of stiffness and compliance. By selecting materials with appropriate thermal expansion coefficients and mechanical properties, the mounting posts can accommodate thermal strains while maintaining structural stability without requiring complex multi-component designs.
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 minimizes thermal and mounting biases, enhancing the sensitivity and performance of the accelerometer by decoupling thermal and mounting strains from the flexures, thereby improving the accuracy of acceleration measurements.
Implementation Method 1
The support ring is clamped in position in the device, which can lead to thermal strains as well as mounting strains being coupled to the flexures
Implementation Method 2
The mounting post is configured for allowing displacement between said first longitudinal end and said second longitudinal end in at least one direction different from said sensing axis to permit at least a portion of said differential movement between the support member and the housing
Data Source
AI summary
An accelerometer for sensing acceleration along a sensing axis, includes a flexure member (having a pendulum member pivotably connected to a support member via a hinge arrangement), a housing, and at least one mounting structure configured for clamping the support member to the housing in load bearing contact while concurrently allowing for differential movement between the support member and the housing. Embodiments also include a corresponding housing member for use with a flexure member of an accelerometer, and a flexure member for use with a housing of an accelerometer.