A Study of Shape Memory Alloy Wires as Actuators for Textile Robotics and Compression Garment Applications

Abstract

In 2008, a Surgeon General's Call to Action was published on how to prevent Deep Vein Thrombosis, DVT, and Pulmonary Embolism, PE. These two diseases are the main cause blood clots and hold high death counts. With the only prevention devices being two extremes, a static compression garment and a pneumatic compression boot with a non-movable air pump, hospital-level care is not available in a transportable, comfortable and cost-effective system. If a textile soft-robotic device could be introduced to the employment of blood clot prevention, a medium ground could be accomplished where a patient can obtain hospital-level quality care anywhere with higher comfort. To achieve this goal, textile-based robotics have been considered with the implementation of smart materials into knitted and woven fabrics. This thesis studies and utilizes shape memory alloys, SMAs, as a smart material inside of a woven textile for an outcome of a robotically-controllable fabric. SMAs are a unique material that can transform into a trained or ``memorized'' shape when a thermal condition is met. This, along with many super-elastic material properties, including high power and force-to-weight ratios, makes SMAs remarkable for actuation in robotics. SMA integration into fabrics brings a new outcome of functioning fabric-structures through thermal control. However, most SMA research is within the linear scope of actuation due to a hysteresis in the material, as well as the lack of natural recovery and control over the actuation path. This work characterizes bending-force outcomes of SMA actuators within woven structures to develop a massaging sleeve or sock to prevent DVT and PE. Currently, the field of SMA-fabric integration is limited with the research focused on aesthetic and commercial needs. This work will strive to focus on the robotic, medical, and industrial aspects of the integration through the development of a woven SMA-fabric massaging structure. Specific SMA working parameters are experimentally researched and modeled for both linear and bending actuators. These parameters include transformation temperature, power consumption, acceleration, torque and angular displacement. These parameters are controlled through material properties, the annealing process and the actuation parameters of the SMA wire segments. The main outcomes of this research are a bending force study of 60 mm SMA wire segments by themselves and within a woven textile. Proof of concepts of the textile-based robot and compression garment applications are carried out and compared with current implementations and SMA actuators in this field. The progression has the potential to be implemented in the development of a fully woven massaging sock or sleeve to prevent blood clots.%%%%Ph.D., Electrical Engineering – Drexel University, 2016