Variable-Structure Soft Actuator for Multi-Mode Grasping

Abstract

Soft actuators are widely used in grasping tasks involving irregularly shaped and fragile objects due to their inherent compliance. However, most existing soft actuators lack shape-morphing capabilities, making it difficult to achieve optimal grasping performance when faced with different operational scenarios. Inspired by the grasping ability of the octopus tentacle, we propose a design and fabrication method for a bending-type soft actuator with switchable deformation capability, termed VSSA (Variable-structure Soft Actuator). The VSSA consists of a structurally variable limiting layer and a folded tube. By altering the structure of the limiting layer, the VSSA can achieve both planar bending motion and spatial helical bending motion. A corresponding theoretical model was established to analyze the deformation modes of the VSSA under different air chamber distance. Furthermore, experiments were conducted to evaluate its motion characteristics, stiffness, tip force, and pull-off force. Based on the VSSA, single-finger, two-finger, and multi-finger grippers were further fabricated, demonstrating effective grasping capabilities for daily objects of various shapes, sizes, and weights. The results indicate that the variable-structure capability endows the grippers with enhanced shape and size adaptability, offering a novel approach to improving the performance of soft grippers.