Equivalent unit cell model for predicting large deformation of soft actuators

Abstract

Soft actuators are versatile devices used in engineering applications such as soft robotics, and medical devices. Recently, shape memory alloy (SMA)-textile-based actuators have been developed using knitting methods, specifically knit (K) loop and purl (P) loop arrangements. SMA provides considerable deformation (usually 4–8 %). However, knitting is complex, time-consuming, and needs extra expertise to ensure accuracy. Research has been done on four different combinations of K-loop and P-loop and their application to blooming flowers to analyze their actuation. Predicting SMA behavior is challenging due to the material's nonlinear properties. In this research, a novel method has been developed to analyze the actuation of K-loop and P-loop-based soft actuators by creating the Equivalent Unit Eell model (EUC), using ABAQUS. The EUC model employs linear constitutive equations used in ABAQUS using user-defined material subroutine (UMAT) for SMA material. By simulating the behavior of soft actuators using EUC models, we aim to comprehensively understand their actuation capabilities with various knit morphing structures. Nine new pattern arrangements were also explored. Experimental results validated the EUC model's effectiveness, demonstrated through a novel blooming knitted flower design. This approach successfully predicts soft actuator performance. © 2025 Elsevier B.V., All rights reserved.