Shape-adaptive stiffness variable soft gripper using porous structure

Robotic grippers are essential components used in robots to perform certain tasks. Effective gripping capabilities are important for industrial and service robots. However, the parallel-type gripper, which is one of the most widely used robotic grippers, has limitations in terms of the objects that it can handle as well as applying the correct handling force, especially when handling fragile objects. Hence, a soft gripper fabricated using soft materials is proposed as a new alternative, with the advantage of preventing injuries when human-robot interaction is required. However, the limited holding force and uncontrollable movement of a soft gripper, due to its softness, could limit its use in real-life conditions. Therefore, in this article, we propose a shape-adaptive tip using a variable stiffness mechanism. To decrease the initial stiffness of the gripper tip, the reticulated polyurethane foam structure was embedded in the tip as the soft supporting layer to support the external force. The flexible mesh structure was applied as the jamming layer to change the stiffness of the tip. The prototype of the gripping system was tested, and the gripper could transfer the grape effectively without damage using the jamming mechanism.