Reconfigurable bionic soft pneumatic gripper for fruit handling based on shape and size adaptation

A universal soft gripper for fruit grasping is challenging to develop. In this study, a modular and reconfigurable soft pneumatic gripper was designed. The designed gripper was inspired by the dexterous grasping of the human hand for fruits of different shapes and sizes. It comprised three soft extension actuators (SEAs), two soft rotation actuators (SRAs), and three soft bending actuators (SBAs). By adjusting SRAs, two grasping poses (claw and clenching pose) could be made to hold fruits of different shapes. The grasping size under each pose could be continuously adjusted by SEAs to grasp fruits of different sizes. SBAs were used to mimic soft fingers for grasping. Theoretical and simulation models were established to predict the relationships between deformations and pressures of SEAs, SRAs, and SBAs. The deformation characteristics of these actuators were experimentally investigated. It was shown that, by inflating SEAs, the grasping sizes under the claw and clenching poses could be increased by 87.5% and 94.5%, respectively. Furthermore, a visual recognition system was designed for automatically controlling the grasping pose and size. Grasping tests showed that, by reconfiguring the grasping pose and size, various fruits, vegetables, and foods with weights from 32 to 786 g (24.6 folds) and diameters from 30 to 141 mm (4.7 folds) could be successfully grasped, indicating the broad applicability of our all-pneumatic soft gripper.