Leaf Flexure Array Guidance for Long-Travel Precision Motion
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Solution Overview
Problem
Conventional flexure-based linear stages require high actuator force and are limited in travel range due to the trade-off between on-axis and off-axis stiffness, resulting in suboptimal motion precision and increased parasitic errors.
Innovation Solution
A flexure-based linear stage guidance system utilizing arrays of thin, compliant leaf flexure elements that are stiff in all degrees of freedom except one, allowing for deterministic deformation and minimizing parasitic straightness and angular errors, with optional stiffeners to enhance rotational and buckling stiffness, enabling longer travels and higher payload capabilities within a compact package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shorter, thicker flexures are used to increase off-axis stiffness, then motion precision is improved, but on-axis stiffness decreases requiring higher actuator force
Solution Approach 1:
The patent divides a single thick flexure into multiple thinner flexure elements arranged in parallel. Each thin flexure element has reduced thickness compared to conventional single flexures, but the array of multiple elements collectively provides the necessary off-axis stiffness through their combined structural support, while individually maintaining appropriate on-axis compliance for precision motion.
Solution Approach 2:
Multiple thin flexure elements are merged into a unified array structure that functions as a single guidance system. The combined array provides both the off-axis stiffness needed for motion precision and the on-axis compliance required for smooth actuation, resolving the trade-off between these two stiffness requirements.
2Stability of the object's composition
If thinner flexures are used to reduce stress and increase compliance, then on-axis compliance is improved, but off-axis stiffness decreases reducing motion quality
Solution Approach 1:
The guidance system segments the flexure function across multiple thin elements rather than relying on a single thick element. This segmentation allows each element to be thin and compliant for smooth actuation while the collective array maintains high off-axis stiffness for motion quality.
Solution Approach 2:
The array of multiple thin flexure elements creates a composite structural system where the combined properties of the elements provide both compliance and stiffness characteristics that individual elements cannot achieve alone, effectively creating a composite mechanical system with tailored mechanical properties.
3Device complexity
If single or compound flexures are used at each corner, then structural simplicity is maintained, but parasitic straightness and angular errors increase
Solution Approach 1:
The patent replaces single corner flexures with distributed arrays of thin flexure elements along the guidance path. This segmentation creates multiple degrees of freedom that can independently accommodate parasitic motions, thereby reducing the impact of straightness and angular errors on overall system precision.
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 system achieves high-quality, repeatable motion with minimal parasitic errors and increased payload capacity while reducing actuation requirements, offering improved precision and extended travel ranges in a smaller form factor compared to traditional single-flexure designs.
Implementation Method 1
The leaf flexure elements are thin and compliant in one linear direction while stiff in all other degrees of freedom; thus, when mechanically stressed, the flexure elements deform, bend, or deflect in a deterministic manner in one degree of freedom
Data Source
AI summary
A flexure based guidance system for precision motion control includes a base that is fixed in position, a carriage that can move relative to the base, an actuator provides the force to move the carriage relative to the base, and one or more flexures arrays that each comprise two or more leaf flexure elements. The actuator causes the carriage to move relative to the base, which causes the flexure elements in the flexure array to flex. The leaf flexure elements are thin, compliant and deform, bend, or deflect in a deterministic manner when mechanically stressed. In some embodiments, stiffeners can be added to the flexures. The guidance system can be integrated into a varifocal head mounted display (HMD) to adjust a location of one or moveable elements in an optical system of the HMD to control a location of an image plane.