SMA Wire Release Actuator With Thermal Threshold Control
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Solution Overview
Problem
Existing release devices, such as pyrotechnic, burn-wire, and paraffin actuators, face challenges in reliability, force management, multi-use capabilities, and operational efficiency, particularly in harsh environmental conditions like aerospace and underwater applications.
Innovation Solution
An actuator using a shape memory alloy (SMA) with a transition temperature, coupled with a power source and heat transfer material, that remains unchanged under a first current for a predetermined time and moves when a second current is applied, incorporating a heat sink for thermal management, allowing controlled activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pyrotechnic devices are used for release, then high reliability and strong actuating force are achieved, but the structure must manage large forces and the device is single-use
Solution Approach 1:
The patent replaces pyrotechnic mechanical/chemical actuation with a shape memory alloy (SMA) based actuator that uses thermal-mechanical coupling. The SMA wire undergoes phase transformation when heated by electrical current, producing linear contraction force that actuates the release mechanism, eliminating the need for high-force pyrotechnic charges.
Solution Approach 2:
The patent changes the actuation parameter from chemical energy (pyrotechnics) to thermal energy (electrical heating of SMA). By controlling the temperature of the SMA wire through electrical current, the actuator produces controlled linear motion and force, avoiding the large forces inherent in pyrotechnic systems.
2Force
If burn-wire devices are used, then force management is improved, but the device is limited to small loads and requires reloading
Solution Approach 1:
The SMA actuator provides universal applicability across different load requirements. By adjusting electrical current parameters and SMA wire specifications, the same actuator design can handle various load conditions, replacing the need for different specialized devices like burn-wire for small loads or pyrotechnics for large loads.
Solution Approach 2:
The SMA wire can be reset by cooling it below its transformation temperature, allowing the actuator to be reused multiple times without replacement or reloading, unlike single-use pyrotechnic or burn-wire devices.
3Duration of action of stationary object
If paraffin actuators are used, then reusability is achieved, but the device size increases, cost increases, and operation speed decreases
Solution Approach 1:
The patent replaces the mechanical/thermal expansion mechanism of paraffin actuators with an electrical-thermal-SMA mechanism. Electrical current directly heats the SMA wire, which contracts through phase transformation, providing faster and more compact actuation compared to paraffin's thermal expansion method.
Solution Approach 2:
The patent utilizes the martensitic phase transition of shape memory alloy at specific temperatures. When heated above the transformation temperature, the SMA wire transforms from martensite to austenite phase, causing linear contraction that actuates the release mechanism, providing a more efficient and compact solution than paraffin's phase change.
4Reliability
If shape memory alloy actuator is used, then controlled activation is achieved, but thermal management is required to prevent unintended operation
Solution Approach 1:
The patent introduces a thermal management system with heat transfer material and heat sink as intermediaries between the SMA actuator and the environment. These components control the thermal field, conducting heat away from the actuator during low-current conditions and allowing heat accumulation during high-current actuation, thereby preventing unintended operation.
Solution Approach 2:
The thermal management system provides thermal feedback control. The heat sink and heat transfer material create a thermal pathway that regulates the temperature of the SMA actuator based on the electrical current applied, ensuring the actuator only activates when the temperature threshold is reached through controlled heating.
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 SMA actuator provides reliable and controlled activation, avoiding unintended operation in low-energy events and ensuring high-energy event activation, enhancing reliability and efficiency in diverse applications like payload deployment and emergency hatch release.
Implementation Method 1
an actuating element disposed within the first path, the actuating element being made from a shape memory alloy having a transition temperature
Implementation Method 2
when the power source applies a second current; and a heat transfer material disposed in the first path between the actuating element and the housing
Implementation Method 3
a heat transfer material disposed in the first path between the actuating element and the housing
Data Source
AI summary
An actuator, a release device, and a method of actuating a release device are provided. The actuator comprises a housing defining a first path; an actuating element disposed within the first path, the actuating element being made from a shape memory alloy having a transition temperature, the actuating element being configured to couple with a power source, at least portion of the actuating element being further configured to not change shape when the power source applies a first current for a predetermined amount of time and moves at least a portion of the actuating element from the first position to a second position when the power source applies a second current; and a heat transfer material disposed in the first path between the actuating element and the housing.