Shape Memory Wire Four-Joint Drive for High-Stroke Actuation
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Solution Overview
Problem
Existing actuators with shape memory drives face challenges in simplifying their setup while maintaining high stroke and force output.
Innovation Solution
A drive unit with a transmission unit comprising four support elements and four hinge elements forms a four-joint configuration, allowing a wire made of shape memory material to be guided multiple times between these elements, leveraging the lever effect to increase stroke and counteract force reduction, with contacts for current feed through the wire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a shape memory wire is used to extend the limited displacement of a shape memory drive, then the stroke is increased, but the force output is significantly reduced
Solution Approach 1:
The wire is guided multiple times between support elements in a spatial arrangement, transforming a linear contraction into a multiplied linear displacement through dimensional routing. The wire runs back and forth between support elements 4a and 4c, creating a meandering path that amplifies the stroke while the support elements and hinge elements maintain force transmission through their structural arrangement.
2Length of moving object
If multiple wire pieces are used to achieve high stroke, then the displacement is increased, but the device complexity increases due to multiple connections
Solution Approach 1:
Multiple wire pieces and their connections are merged into a single continuous wire that runs multiple times between the same support elements. This eliminates the need for multiple separate wire pieces and their corresponding connections, reducing device complexity while maintaining the stroke multiplication effect through the wire's repeated routing between support elements 4a and 4c.
3Length of moving object
If the wire is guided multiple times between support elements, then the stroke is multiplied, but the force is reduced due to the lever effect
Solution Approach 1:
The force reduction caused by the lever effect is compensated by the mechanical advantage provided by the hinge elements and support elements arrangement. The hinge elements act as fulcrums that counterbalance the force reduction, allowing the system to maintain sufficient force output while achieving stroke multiplication through the wire's multiple passages between support elements.
4Device complexity
If a simple wire arrangement is used, then the device setup is simplified, but the stroke is limited
Solution Approach 1:
The wire's path is segmented into multiple straight sections between support elements, with each section contributing to the overall stroke multiplication. The wire is divided into segments that run between different pairs of support elements (4a-4c, 4b-4d, etc.), allowing the system to achieve extended stroke while maintaining a relatively simple overall structure with only four support elements and four hinge elements.
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 configuration simplifies the actuator setup, enhances stroke, and maintains force output by utilizing the wire's length contraction for efficient movement, reducing the need for multiple wire pieces and complex connections.
Implementation Method 1
a wire, which is formed from a profiled sheet of the material... decreases its extension in at least one spatial length when heated... This heating may for instance be effected by a current feed to an electrically conductive shape memory material
Implementation Method 2
This heating may for instance be effected by a current feed to an electrically conductive shape memory material
Implementation Method 3
a transmission unit, to which the at least one wire is attached, for transmitting a force exerted by the at least one wire to the connection unit... leveraging the lever effect to increase stroke
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a drive unit (1) for an actuator (9) with a shape memory drive, comprising at least one elongated wire (2), which is formed from a shape memory material, a transmission unit (3), to which the at least one wire (2) is attached, for transmitting a force exerted by the at least one wire (2) to a connection unit, wherein the connection unit is configured for force output on an output side of the drive unit (1), and two contacts (7) for contacting the at least one wire (2) with a control unit (8). To simplify the setup of an actuator with shape memory drive whilst maintaining a high stroke and a high force, it is envisaged that the transmission unit (3) comprises four support elements (4) and four hinge elements (5), wherein in each case two of the four support elements (4) are connected to one another via a respective one of the hinge elements (5).