Flexure Actuator for Precise Rotary-to-Linear Positioning
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Solution Overview
Problem
Conventional actuators for optical systems, such as those in telescopes, face challenges in achieving precise positioning and control over large distances with small increments due to their complexity and weight, and there is a need for simpler and more effective actuator systems that can convert rotational input to linear output with high precision.
Innovation Solution
The actuator system employs a flexure assembly with cross-blade and rotary flexures, monolithically connected to a rotary base and frame, which converts rotary motion into linear motion with minimal mechanical play, using stepper motors and harmonic drives to achieve precise positioning of optical elements like lenses and mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional motor and screw designs (ball, roller, or lead screws) are used to achieve precise positioning, then positioning precision is improved, but device complexity and weight increase due to large number of parts
Solution Approach 1:
The patent combines multiple functions into a monolithic flexure assembly that integrates the carriage, flexure elements, and support structures into a single piece. This eliminates the need for separate motors, screws, nuts, and other discrete components while maintaining precise positioning capability through elastic deformation of the flexure blades.
Solution Approach 2:
The invention replaces traditional mechanical screw and motor assemblies with a flexure-based elastic mechanism. Instead of using threaded screws and motor-driven rotation, the system uses controlled elastic deformation of flexure blades to achieve linear motion, thereby eliminating friction, backlash, and the need for lubrication.
2Measurement precision
If conventional motor and screw designs are used for precise positioning, then positioning precision is improved, but weight increases due to large number of parts
Solution Approach 1:
By merging the carriage, flexure elements, and support structures into a monolithic assembly, the patent eliminates the weight of separate motors, screws, nuts, and fasteners. The single-piece construction reduces overall actuator weight while maintaining structural integrity and positioning precision through elastic deformation.
3Device complexity
If flexure assembly with cross-blade and rotary flexures is used to reduce complexity, then device complexity is reduced, but achieving high axial and lateral stiffness becomes challenging
Solution Approach 1:
The patent applies different geometric configurations to different regions of the flexure assembly. The cross-blade flexures have specific blade geometries optimized for axial motion, while the rotary flexure has a cruciform configuration optimized for rotational flexibility. This local optimization allows each region to provide the appropriate stiffness and flexibility needed for its function.
Solution Approach 2:
The flexure assembly utilizes composite structural design combining multiple blade elements arranged in specific configurations (cross-blade and cruciform patterns). This composite arrangement provides both flexibility for motion and stiffness for load-bearing, achieving a balance between compliance and structural strength without requiring additional support components.
4Ease of operation
If conventional mechanical systems are used, then rotational to linear conversion is achieved, but friction and backlash occur reducing precision
Solution Approach 1:
The patent replaces friction-based mechanical contact (screws, gears, bearings) with elastic deformation-based motion transmission. The flexure blades convert rotational input to linear output through controlled bending and twisting, eliminating friction and backlash entirely since there is no sliding or rolling contact between moving parts.
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 solution provides high axial and lateral stiffness, eliminating friction and backlash, and enabling large distance actuation with fine resolution, enhancing the reliability and precision of optical system positioning without the need for lubricants or wear components.
Implementation Method 1
cross-blade flexures operatively connect the carriage to the rotary base, the cross-blade flexures including a plurality of blade flexures and being oriented at an oblique angle to the rotary base and to the axis of the actuator system. A rotary flexure operatively connects the rotary base to the frame. The cross-blade flexures and the rotary flexure are configured to convert rotary motion of the rotary base into linear motion of the carriage
Implementation Method 2
The rotary flexure can include a cruciform set of axially extending blades connecting between the rotary base and the frame configured for rotational flexibility in axial twisting and rigidity against bending
Data Source
AI summary
An actuator system includes a frame configured to remain stationary relative to a carriage within the frame and connected to the frame by a flexure assembly configured to constrain the carriage for only linear motion along an axis of the actuator system. A rotary base is configured to receive rotational input. Cross-blade flexures operatively connect the carriage to the rotary base, the cross-blade flexures including a plurality of blade flexures and being oriented at an oblique angle to the rotary base and to the axis of the actuator system. A rotary flexure operatively connects the rotary base to the frame. The cross-blade flexures and the rotary flexure are configured to convert rotary motion of the rotary base into linear motion of the carriage and to maintain axial and lateral stiffness.