Cross Beam Flexure Pivot Assembly With Uniform Moment Stiffness
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Solution Overview
Problem
Cross beam flexure pivot assemblies face challenges in maintaining precision pointing due to unequal moment stiffness in different directions, which can lead to reduced performance when supporting cantilevered loads, requiring larger or heavier designs that compromise system performance.
Innovation Solution
A cross beam flexure pivot assembly design with five beams of equal length and thickness, arranged to provide equal linear stiffness in both X and Y directions and equal moment stiffness about the X and Y axes, minimizing friction and optimizing size and mass within given constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cross beam flexure pivot assemblies are designed using the softer direction moment stiffness to support cantilevered loads, then the load can be supported, but the assembly requires a larger or heavier design that reduces system pointing performance
Solution Approach 1:
The patent applies asymmetry by configuring beams with different cross-sectional dimensions and material properties to achieve equal moment stiffness in both principal directions. Specifically, beams are designed with asymmetric cross-sections where the width and thickness are optimized to provide identical flexural rigidity (EI) about both the x and y axes, eliminating the need to design for the softer direction only. This allows the assembly to support cantilevered loads effectively while minimizing mass.
Solution Approach 2:
The patent employs parameter changes by systematically varying beam cross-sectional dimensions, material composition, and beam spacing to achieve the optimal balance between moment stiffness and mass. The design process involves adjusting parameters such as beam width, thickness, length, and material properties to equalize the moment of inertia products (Ix and Iy) while minimizing the total mass of the flexure assembly. This enables support of cantilevered loads with optimally sized components.
2Device complexity
If cross beam flexure pivot assemblies have unequal moment stiffness in different directions, then the structure can be simplified, but precision pointing is compromised
Solution Approach 1:
The patent applies asymmetry by configuring beams with different cross-sectional dimensions and material properties to achieve equal moment stiffness in both principal directions. Specifically, beams are designed with asymmetric cross-sections where the width and thickness are optimized to provide identical flexural rigidity (EI) about both the x and y axes, eliminating the need to design for the softer direction only. This allows the assembly to support cantilevered loads effectively while minimizing mass.
Solution Approach 2:
The patent employs parameter changes by systematically varying beam cross-sectional dimensions, material composition, and beam spacing to achieve the optimal balance between moment stiffness and mass. The design process involves adjusting parameters such as beam width, thickness, length, and material properties to equalize the moment of inertia products (Ix and Iy) while minimizing the total mass of the flexure assembly. This enables support of cantilevered loads with optimally sized components.
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 design achieves reliable and repeatable pointing performance for cantilevered loads by balancing linear and moment stiffness, ensuring maximum performance within mass and volume constraints, while reducing friction and maintaining precision.
Implementation Method 1
Flexing beam members connect two parts of the cross beam flexure pivot assembly, which have limited rotation relative to one another
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
Cross beam flexure pivot assembly includes a first housing member having a first arcuate member a second housing member having a second arcuate member wherein the first arcuate member extends into the second housing member and the second arcuate member extends into the first housing member. First, second and, third beams extend in first direction and fourth and fifth beams extend in a second direction all secured to first and second arcuate members. A first axis, second axis and radial axis of the first and second housing members form a common point of intersection. Total of cross section areas of beams extending in first direction and of beams extending in second direction are equal providing equal linear stiffness in both directions. Total moment stiffness about first axis equals total moment stiffness about the second axis.