Linear Flexure Bearing Off-Axis Stiffness
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Solution Overview
Problem
High-performance precision motion sensors face challenges with off-axis contamination and non-linearity, limiting their bandwidth and accuracy, particularly in high-end Inertial Measurement Units and ultra-precise linear servo mechanisms due to higher order structural resonance modes and stiffness issues.
Innovation Solution
A high-performance linear flexure bearing system utilizing U or V-shaped spring flexures and corresponding flex couplers to restrict off-axis movements while ensuring linear motion, enhancing the system's stiffness and bandwidth by connecting the stage to a fixed base through these components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional linear bearing or flexure arrangements are used to suspend the stage, then the sensor can move in the sensing direction, but off-axis contamination and non-linearity occur, degrading performance
Solution Approach 1:
The bearing structure is segmented into multiple independent flexure elements (at least two flexures) that connect the stage to the base. Each flexure handles specific degrees of freedom, allowing the system to provide linear motion in the sensing direction while independently restraining off-axis movements through the combined action of multiple segmented elements.
Solution Approach 2:
Different regions of the flexure structure have different stiffness properties tailored to specific functions. The flexures are designed with varying local stiffness characteristics - compliant in the sensing direction to allow motion, but stiff in off-axis directions to restrain contamination. This local differentiation of mechanical properties enables simultaneous achievement of motion freedom and contamination rejection.
2Measurement precision
If attempts are made to improve on-axis performance by modifying the bearing structure, then sensing accuracy may improve, but off-axis contamination and non-linearity in stage movement increase
Solution Approach 1:
The flexure elements are designed with asymmetric geometric configurations optimized for their specific functional requirements. Each flexure has an asymmetric cross-section or shape that provides different stiffness characteristics along different axes, enabling the structure to be compliant in the sensing direction while being stiff in off-axis directions, thus maintaining linearity while improving sensing accuracy.
Solution Approach 2:
The problem of off-axis contamination is solved by introducing additional dimensional constraints through multiple flexure elements arranged in specific spatial configurations. By utilizing three-dimensional spatial arrangement of at least two flexures, the system restrains off-axis movements in multiple directions simultaneously while maintaining linear motion capability in the primary sensing dimension.
3Adaptability or versatility
If higher order structural resonance modes are present, then the system can support complex motion, but servo bandwidth is limited at higher frequencies due to these modes containing off-axis motion components
Solution Approach 1:
The harmful higher order resonance modes containing off-axis motion components are extracted and eliminated from the system's dynamic response. The flexure bearing design specifically targets and removes these unwanted vibrational modes through optimized stiffness distribution and geometric configuration, leaving only the desired low-order modes that support useful motion while enabling higher servo bandwidth operation.
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 significantly improves the on-axis performance by increasing off-axis stiffness and maintaining linearity, thereby expanding the operational bandwidth and enabling higher frequency operation in precision motion sensing applications.
Implementation Method 1
two or more spring flexures that connect the stage to the body, each of the two or more spring flexures having a center portion and being shaped like a U or a V
Implementation Method 2
one or more flex couplers that each connects the center portions of a pair of the two or more spring flexures to restrain off-axis movements of the stage while providing for a linear motion along the direction of sensing
Data Source
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AI summary
A system and a method are disclosed for a high bandwidth linear flexure bearing, which may be particularly useful in high end accelerometers and high-precision linear servo mechanisms. Certain embodiments may apply to sensors that measure motion in one dimension. Such embodiments may substantially improve the off-axis performance of the sensors providing ultra-repeatability while maintaining linearity of motion and linearity in spring rate. Some embodiments use spring flexures (602, 702, 802, 902) and flex-couplers (604, 704, 804, 904) to support the sensor stage (601, 701, 801, 901) and connect it to the reference base (603, 703, 803, 903). Several embodiments are disclosed that may fit the needs of specific applications in the area of high-end servos and accelerometers.