A Novel Fabric Muscle Based on Shape Memory Alloy Springs

Fabric muscle is important for wearable robots that are soft, compliant, and silent with high contractility and high force. This study presents a novel shape memory alloy (SMA) spring-based fabric muscle (SFM). The SFM is manufactured by bundling SMA springs with proven performance as artificial muscle. The SFM generates high contractility and high force, and is soft, flexible, and light because it is covered with fabric used to make actual clothes. The SFM is contracted by heat and shows a contraction strain of 50% at a heating temperature of 70°C while generating 100 N force or higher. Furthermore, it generates a maximum contraction strain of 67% under no load. To drive it with the optimum voltage and current, the SFM is designed by optimizing the serial and parallel connection methods for the embedded SMA springs. We propose herein design and manufacturing methods for the SFM and verify the usability of the SFM as a soft actuator through a performance evaluation. The SFM as a soft actuator with a simple structure-like fabric is easily applicable to soft wearable robots that can support muscle power by simply being attached to usual suits. The SFM has a soft touch, and is lightweight; hence, it has the potential for wide applications to new-concept soft wearable robots that can be comfortably worn anytime and anywhere like usual clothes.