Analysis of Deflection Angle and Actuation Capabilities of a Soft Knitted Gripper Employing an Equivalent Unit Cell Model

초록

Soft robotics offers enhanced flexibility, adaptability, and safety compared with traditional rigid-body systems, making it particularly suitable for applications involving human interaction and unstructured environments. Among the various actuation mechanisms developed for soft robots, shape memory alloy (SMA)-textile actuators have emerged as a promising solution owing to their lightweight, silent operation, and high energy density. This study investigates the actuation performance and deflection behavior of a soft knitted gripper fabricated using SMA-based textile actuators configured in a P-loop pattern. To model and predict the deformation behavior of the gripper, an equivalent unit cell (EUC) model was implemented in ABAQUS. This model was employed to analyze and compare the deflection capabilities of the soft knitted gripper against the EUC model. Geometric nonlinearity was incorporated to simulate large deformations resulting from the shape memory effect under electrical excitation. The analysis focused on the bending behavior of the P-loop structure, which is critical for effective gripping and manipulation tasks. Experimental validation was performed by applying varying voltages to the gripper and measuring the resulting deflection angles. Results indicate that increasing the applied voltage significantly enhanced bending, with maximum deflection angles up to 180°, demonstrating the actuator’s strong performance. Numerical simulations from the EUC model closely aligned with experimental results, with only a 5% deviation in maximum bending angle, thereby confirming the accuracy and reliability of the proposed modeling approach. This study demonstrates that the EUC model is exceptionally proficient in estimating the actuation behavior of SMA-textile-based soft grippers. The findings provide significant insights for the design and enhancement of next-generation soft actuators and underscore the potential of SMA-textile composites in modern soft robotic systems and biomedical applications requiring conformal, compliant actuation.

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