SMA Linear Actuator Stroke Amplification
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Solution Overview
Problem
Current shape memory alloy (SMA) devices lack effective linear actuators that provide significant stroke amplification and are adaptable to both pushing and pulling applications, with a focus on deriving gains from interconnected members.
Innovation Solution
A linear actuator comprising a first SMA member that shortens when heated and a second SMA member that lengthens when heated, coupled together to achieve relative movement, with optional third members that also change length upon thermal actuation, forming a thermally actuatable telescoping assembly for enhanced stroke amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SMA devices are used, then reliability and weight efficiency are improved, but stroke amplification and adaptability to pushing/pulling applications are insufficient
Solution Approach 1:
The linear actuator is divided into multiple SMA members (first SMA member, second SMA member, and optional third SMA member) that can be independently configured with different transition temperatures and training states. This segmentation allows each member to contribute differently to the overall actuation, enabling both pushing and pulling applications while maintaining reliability.
Solution Approach 2:
The actuator design enables universal functionality by allowing the same basic structure to perform both pushing and pulling operations through proper configuration of the SMA members' transition temperatures and training states. The system can be adapted for different applications without requiring separate mechanisms.
2Length of moving object
If multiple SMA members are interconnected to derive stroke amplification, then stroke amplification is improved, but device complexity increases
Solution Approach 1:
The SMA members are arranged in a nested configuration where the second SMA member is positioned within or alongside the first SMA member, and the third SMA member is integrated into the assembly. This nesting allows the members to interact and amplify stroke while maintaining a compact structure and reducing overall complexity.
Solution Approach 2:
Multiple SMA members are merged into a single integrated actuator assembly with common coupling elements and shared structural features. The members work together to produce combined stroke amplification while the merging of functions reduces the number of separate components and simplifies the overall device.
3Adaptability or versatility
If SMA members are trained to expand longitudinally, then adaptability to pushing applications is improved, but manufacturing complexity increases
Solution Approach 1:
Different SMA members are assigned different local qualities through selective training processes. The first, second, and third SMA members can be trained with different transition temperatures and shape memory characteristics to suit their specific roles in pushing or pulling applications, while maintaining standard manufacturing procedures for each individual member.
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 enables improved stroke amplification and adaptability to both pushing and pulling applications, allowing for efficient use in scenarios like space vehicle component coupling, with the ability to collapse and extend based on temperature changes, providing repeated cycling and intrinsic resetting.
Implementation Method 1
Shape memory alloys exhibit thermo-mechanical properties that are useful in constructing thermally actuatable devices. Generally, a shape memory alloy (SMA) is a metallic alloy that has distinctly different phases on opposing sides of a transition temperature. An SMA reaches a first physical state when it is below its transition temperature and a second physical state when it is above its transition temperature.
Implementation Method 2
Some SMA materials can be trained to have a first shape for the cooler first state and a second shape for the warmer second state. A two-way trained SMA can forcibly assume the second shape when heated above the transition temperature and then gently return, if not otherwise restricted, to the first shape when cooled to below the transition temperature.
Implementation Method 3
The wire can be heated by ohmic heating produced by passing an electrical current through the wire.
Data Source
AI summary
Linear actuators including coupled elongate members formed of shape memory alloys are provided. Members that lengthen when heated are coupled to members that shorten when heated such that stroke amplification gains are derived from each member. The members may be tubular and may be coaxially arranged for telescopic extension and collapse. Sections of a modular structure such as a space vehicle may be latched and clamped together for assembly or for docking by utilizing linear actuators having shape memory alloys that are actuated thermally.