Development and evaluation of a robust soft robotic gripper for apple harvesting

Fruit harvesting is facing challenges due to the labour shortage, which has been more severe since the rapid pandemic. Robotic harvesting has been attempted in autonomous fruit harvesting tasks, such as apple harvesting. However, current apple harvesting robots show limited harvesting performance in the orchard environment due to the inefficiency of the robotic grippers. This research presents a fruit harvesting method that includes a novel soft robotic gripper and a detachment strategy to achieve apple harvesting in the natural orchard. The soft robotic gripper includes four tapered soft robotic fingers (SRF) and one multi-mode suction cup. The SRF is customised to avoid interference with obstacles during grasping, and its compliance and force exertion are comprehensively evaluated with FEA and experiments. The multi-mode suction cup can provide suction adhesion force, show active extrusion/withdrawal, and present passive compliance mode. The simultaneously twist-pulling motion is finally proposed and implemented to detach the apples from the trees. The proposed robotic gripper is compact, compliant with apple grasping and generates a large grasping force. Our proposed method is finally validated in a natural orchard and achieves a detachment, damage and harvesting rate of 75.6%, 4.55%, and 70.77%, respectively.