Shape Memory Alloy Actuator with Roller Tension Distribution
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Solution Overview
Problem
Existing actuators using shape memory alloy wires face high power consumption due to strong tensile stress, which can lead to wire breakage when thick wires are used to prevent stress, resulting in increased resistance.
Innovation Solution
The actuator design incorporates a stator and mover with rollers made of thermally conductive materials, a thin shape memory alloy wire, and a swaging mechanism to distribute tension evenly, preventing wire breakage and reducing power consumption by using pulse voltage to generate Joule heat efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick wire is used to prevent wire breakage due to tensile stress, then the strength and reliability are improved, but the resistance decreases resulting in high power consumption
Solution Approach 1:
The patent changes the physical parameters of the wire by using a shape memory alloy with specific transformation temperature characteristics. By controlling the wire thickness to be thin (0.01-0.05 times the actuator width) and selecting materials with appropriate transformation temperatures (e.g., Ni-Ti alloy with 5-50% Ti content), the system achieves both mechanical strength through stress distribution and electrical resistance for efficient heating, resolving the contradiction between strength and power consumption
Solution Approach 2:
The patent segments the tensile stress distribution by introducing multiple thin wires instead of a single thick wire. The plurality of wires (at least two, preferably 3-10) distributes the mechanical load across multiple elements while maintaining sufficient total resistance. This segmentation allows the actuator to handle tensile stresses during retraction without requiring excessive wire thickness, thereby maintaining appropriate resistance levels for power-efficient operation
2Use of energy by moving object
If a thin wire is used to reduce resistance and power consumption, then power consumption is reduced, but the wire may break due to strong tensile stress
Solution Approach 1:
The patent transforms the material properties by selecting shape memory alloys with specific characteristics (Ni-Ti alloy with controlled Ti content, transformation temperature range). These material parameter changes enable thin wires to achieve both low resistance and sufficient strength through the shape memory effect, which allows the wire to withstand tensile stress during retraction while maintaining appropriate electrical resistance for efficient Joule heating
Solution Approach 2:
The patent divides the load-bearing function across multiple thin wires instead of relying on a single thick wire. This segmentation reduces the tensile stress on each individual wire while collectively providing sufficient mechanical strength. The plurality of wires (at least two) maintains adequate total resistance for power consumption management, resolving the contradiction between individual wire thinness and overall system strength
3Speed
If pulse voltage is applied to generate Joule heat for wire contraction, then the actuation speed is improved, but temperature rise may occur affecting stability
Solution Approach 1:
The patent employs periodic pulse voltage application instead of continuous heating. By controlling the duty cycle and duration of pulse signals, the system generates sufficient Joule heat for rapid wire contraction and shape memory transformation while allowing cooling intervals to prevent excessive temperature accumulation. This periodic action enables fast response speed while maintaining thermal stability through controlled heating cycles
Solution Approach 2:
The patent optimizes electrical parameters by selecting appropriate pulse voltage amplitude, duration, and frequency based on the specific shape memory alloy characteristics and wire dimensions. By carefully controlling these parameters, the system achieves rapid actuation through sufficient temperature elevation during pulse application while preventing dangerous temperature rise through limited pulse duration and appropriate duty cycles, thus resolving the contradiction between speed and temperature control
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 actuator achieves low power consumption and stable operation with fast response speed and reduced temperature rise, preventing wire breakage and maintaining uniform tension through the use of a thin wire and efficient heat dissipation.
Implementation Method 1
pulse voltage is applied to a wire made of a shape memory alloy that threads its way through multiple columns made of a thermally conductive material that are arrayed in parallel, to contract the wire by Joule heat
Implementation Method 2
The Joule heat generated in the wire is swiftly dissipated through the columns
Data Source
AI summary
The object is to provide an actuator that consumes less power.An actuator comprises: a stator that rotatably supports a plurality of stator rollers; a mover that rotatably supports a mover roller disposed between the stator rollers; and a wire made of a shape memory alloy that is disposed between the stator rollers and the mover roller and has both ends connected to respective two stator terminals provided in the stator.