Shell Gripper Inspired by Human Finger Structure for Automatically Packaging Agricultural Product

Soft robotic end-effectors have been developed for grasping food and agricultural products. However, end-effectors that can package multiple agricultural products simultaneously in a clustered scenario have not been studied frequently so far. In this paper, we propose a robotic end-effector capable of performing such packaging task on multiple cucumbers. The end-effector consists of multiple thin shell grippers and each of them can grasp one cucumber. The shell gripper is composed of a rigid shell and a soft membrane. Upon pressurization, the soft membrane can be inflated to realize a grasping motion. This hybrid (rigid and soft) structure was inspired by human finger structure, which consists of rigid bone or nail and soft tissue. For fabricating the shell gripper, we proposed a demolding-free casting method that eliminates the need of removing silicone rubber from mold. Thanks to this new fabrication method, we are able to minimize the thickness of the shell gripper. The membrane inflation displacement was experimentally measured to confirm the grasping ability. Finally, field tests on packaging nine cucumbers were conducted and results validated that the proposed robotic end-effector can stably package multiple cucumbers simultaneously.