Soft, Multi-DoF, Variable Stiffness Mechanism Using Layer Jamming for Wearable Robots

Recently, vacuum-based layer jamming mechanisms have been actively researched for safe human-robot interaction. However, most conventional layer jamming mechanisms provide restricted motion in one direction such that their application in wearable robots is significantly limited. To address this problem, we propose a novel, soft, multi-degree of freedom (multi-DoF) layer jamming mechanism that employs a sliding linkage-based layer jamming mechanism (SLLJ). The proposed SLLJ allows movement not only in the linear direction, but also in the pitch and yaw directions. Furthermore, the SLLJ can control its stiffness in multi-directions and generate a large resisting force with small thickness and light weight. Experimental results show that the maximum linear resisting force of SLLJ is 264.8 N, which is comparable to the conventional layer jamming mechanism, and the maximum yaw resisting torque is 1.363 Nm before buckling. In addition, the stiffness of the SLLJ can be increased by 96.6 folds in the linear direction and 60.02 folds in the yaw direction when the SLLJ transforms from soft state to rigid state. Being fabricated in various shapes, the SLLJ can be adapted to a wide range of wearable robots, which require multi-DoF motions with variable stiffness and substantial resisting force.