Planar SMA Actuator on Multi-Layer PCB
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Solution Overview
Problem
Existing actuating devices for aerospace applications face challenges in being lightweight, high load-carrying, fast-acting, and low-shock while also being complex, bulky, and heavy, with little advancement since the introduction of modern shape memory alloy (SMA) actuators in 1998.
Innovation Solution
A reusable actuating device is created using multiple integrated planar shape memory alloy elements with independent driver circuits and a return spring on a single multi-layer printed circuit board, featuring a novel layout for a mechanically simple, electrically and mechanically redundant, lightweight, and low-profile solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SMA actuators are used, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple SMA elements, driver circuits, and mechanical components onto a single PCB substrate, integrating what were previously separate components into one unified structure. This merging reduces the number of discrete parts and simplifies the overall device architecture while maintaining the reliability benefits of redundant SMA elements.
Solution Approach 2:
The PCB serves multiple functions simultaneously: it acts as the structural substrate, the electrical circuit board for driver circuits, the mounting platform for SMA elements, and the mechanical framework for the actuator assembly. This multi-functionality reduces the need for separate components and reduces overall device complexity.
2Force
If cylindrical metallic components with nested mechanisms are used, then actuation force is improved, but weight increases
Solution Approach 1:
The patent replaces complex nested mechanical mechanisms with a planar PCB-based structure. The actuation force is generated directly by the SMA elements mounted on the PCB, eliminating the need for intricate mechanical transmission systems while reducing weight.
Solution Approach 2:
The invention transitions from three-dimensional cylindrical metallic components with nested mechanisms to a two-dimensional planar PCB structure. This dimensional change allows for a lighter, flatter actuator design that maintains actuation force through direct SMA element actuation rather than mechanical leverage.
3Duration of action of stationary object
If external reset devices are used, then reusability is improved, but device complexity increases
Solution Approach 1:
The actuator incorporates an automatic reset mechanism where the SMA elements naturally return to their original shape upon cooling, and the PCB structure automatically resets the mechanical components. This self-service reset capability eliminates the need for external reset devices while maintaining full reusability.
Solution Approach 2:
The reset function is integrated into the PCB structure itself, combining the mechanical reset mechanism with the electrical circuit board. This integration eliminates separate external reset devices and reduces overall device complexity while enabling repeated actuation cycles.
4Reliability
If multiple discrete components are used, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent integrates multiple discrete components (SMA elements, driver circuits, mechanical parts) onto a single PCB, transforming a multi-component assembly into a monolithic structure. This integration dramatically simplifies manufacturing by reducing the number of assembly steps, parts inventory requirements, and quality control checkpoints while maintaining reliability through built-in redundancy.
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 solution provides a reliable, adaptable, and self-resetting actuator that is lightweight, low-profile, and suitable for various applications, including aerospace, by ensuring consistent stroke length and minimizing part count, while preventing overheating and annealing of SMA elements.
Implementation Method 1
electrically through the driver circuits
Implementation Method 2
shape memory alloy elements which directly produce linear motion
Implementation Method 3
heated to their transition temperature
Implementation Method 4
at least one return spring integrated onto a single multi-layer PCB
Data Source
AI summary
This disclosure relates generally to a reusable actuating device utilizing multiple integrated planar shape memory alloy elements integrated with independent driver circuits and at least one return spring integrated onto a single multi-layer PCB with a novel layout to create an electrically and mechanically redundant integrated actuator solution uniquely suited for use in low-profile devices that can be utilized by themselves or as an initiator in a staged device to release higher loads. The apparatus of the invention is particularly useful for spacecraft and other vehicular actuation devices.