Stiffness-Tunable Soft Bellows Actuators by Cross-Fiber Jamming Effect for Robust Grasping

Soft actuators typically exhibit low stiffness and low load-bearing properties due to the intrinsic limitations of soft materials. Stiffness modulation is an effective means to improve the performance of soft actuators. However, most stiffness-tunable mechanisms are nonstretchable, and have difficulty in independently adjusting the tensile stiffness of soft elongation actuators. Here, a universal cross-fiber jamming mechanism with both elongation and bending stiffness-tunable capability is proposed for soft bellows actuators. It is composed of two semicircular symmetrical fiber bundles in an up-and-down crossed arrangement, and can follow the tensile state of the soft bellows actuator through the passive staggered motion of the layered fiber bundles. Furthermore, a soft gripper with wide grasping range and sufficient grasping stability is also developed by applying soft bellows actuators with cross-fiber jamming mechanisms. Experiments are conducted to show the related performance of the proposed cross-fiber jamming mechanism. The results show that it has fast antiimpact damping response, strong shaping ability and adjustable stiffness. Such efficient performance will promote the ability of grasping robots, and is expected to be used in daily life and industry.