SMA Actuator Assembly with Compliant Link Force Amplification
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Solution Overview
Problem
Existing miniature SMA actuators face limitations in stroke and actuating force due to the small contraction percentage of SMA wires, leading to increased size, cost, and energy consumption, especially in miniaturized applications like mobile devices.
Innovation Solution
An SMA actuator assembly with a force-modifying mechanism that amplifies displacement and force using a coupling link compliant perpendicular to the actuating force, allowing shorter SMA wires and reducing the actuator's footprint and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If longer or thicker SMA wires are used to increase maximum stroke or actuating force, then the actuating force and stroke are improved, but the size of the actuator increases and response time decreases
Solution Approach 1:
A force-modifying mechanism is introduced as an intermediary between the SMA wire and the movable part. This mechanism amplifies the actuating force generated by the SMA wire, allowing shorter and thinner wires to achieve the required force output without increasing actuator size or reducing response time.
Solution Approach 2:
The force-modifying mechanism changes the force parameter by providing mechanical advantage through its lever arm configuration. The ratio between the input force arm and output force arm creates force amplification, enabling the system to achieve high actuating force with minimal SMA wire contraction.
2Force
If longer or thicker SMA wires are used to increase maximum stroke or actuating force, then the actuating force and stroke are improved, but the response time is reduced
Solution Approach 1:
The force-modifying mechanism serves as a mediator that decouples the relationship between SMA wire dimensions and actuating force. By using the lever arm mechanism, the system achieves force amplification without requiring longer or thicker wires, thereby maintaining fast response times characteristic of miniaturized actuators.
3Force
If stiffer flexures are used to provide stronger returning force, then the biasing force is improved, but the achievable stroke is reduced and energy consumption increases
Solution Approach 1:
The force-modifying mechanism changes the force parameter by providing mechanical advantage through its lever arm configuration. The ratio between the input force arm and output force arm creates force amplification, enabling the system to achieve high actuating force with minimal SMA wire contraction.
4Force
If stiffer flexures are used to provide stronger returning force, then the biasing force is improved, but the achievable stroke is reduced
Solution Approach 1:
The force-modifying mechanism introduces an intermediary lever system between the flexure and the movable part. This intermediary mechanism provides mechanical advantage, allowing the flexure to generate sufficient biasing force while the lever arm configuration amplifies the available stroke, thus resolving the trade-off between force and displacement.
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 assembly achieves greater stroke and force capabilities, enabling efficient movement of heavier lenses or sensors while maintaining a compact size and reducing costs.
Implementation Method 1
an SMA wire connected between the first part and the force-modifying mechanism for applying an input force on the force-modifying mechanism thereby causing the force-modifying mechanism to apply an output force on the coupling link
Implementation Method 2
the coupling link is compliant in a direction perpendicular to the direction of the actuating force
Data Source
AI summary
An actuator assembly (2) comprising: first (50) and second (60) parts that are movable relative to each other; and one or more actuating units, each actuating unit comprising: a force-modifying mechanism (72) connected to the first part (50); a coupling link (78) connected between the force-modifying mechanism (72) and the second part (60); and an SMA wire (80) connected between the first part (50) and the force-modifying mechanism (72) for applying an input force on the force-modifying mechanism (72) thereby causing the force-modifying mechanism (72) to apply an output force on the coupling link (78) and causing the coupling link (78) to apply an actuating force on the second part (60); wherein the coupling link (78) is compliant in a direction perpendicular to the direction of the actuating force.