A Two-Finger Soft-Robotic Gripper with Enveloping and Pinching Grasping Modes

This article presents a two-finger soft-robotic gripper with enveloping grasping (EG) and pinching grasping (PG) modes. The proposed soft-robotic gripper is based on a two-finger design that combines two dual-module pneumatic actuators with a variable chamber height (DMVCHA). The prototype of the DMVCHA has been fabricated by molding of silicone rubber. In the PG mode, the high passive compliance of the DMVCHA allows large contact area and realizes a vertically plane contact with the object, which improves the grasping reliability and is suitable for grasping objects with a small and medium size. In the EG mode, the DMVCHA becomes the pneumatic network actuator (PneuNet) with a variable chamber height, which provides greater grasping force and is suitable for grasping objects with larger and hollow size. Compared with the traditional PneuNets, the DMVCHA has a greater output force. The bending angle and output force of actuators with different structures have been analyzed by finite-element analysis. The grasping performance of the proposed and universal soft grippers is studied by experiments. The result shows that with only two fingers, the gripper can reliably grasp objects with various shapes and volume, especially small and fragile objects.