GSG: A Granary-Shaped Soft Gripper With Mechanical Sensing via Snap-Through Structure

Soft robotic grippers have attracted considerable attention in terms of the advantages of the high compliance and robustness to variance in object geometry; however, they are still limited by the corresponding sensing capabilities. We propose a novel soft gripper that looks like a ‘granary’ in the geometrical shape with a snap-through bistable mechanism fabricated by an ordered mold technology, which consists of a palm chamber, shell, cap and three fingers. It can achieve ‘sensing’ mechanically and perform pinching, enveloping and caging grasps for objects with various profiles. In particular, the snap-through bistable mechanism in the proposed gripper allows us to reduce the complexity of the mechanism, control, and sensing designs. The grasping behavior is activated once the gripper's deformation or perceived pressure arrives at a certain value. First, after the theoretical model for snap-through behavior is constructed, the modularized design of the gripper is described in detail. Then, the ordered molding method is employed to fabricate the proposed gripper. Finally, the finite element (FE) simulations are conducted to verify the built theoretical model. Further, a series of grasping experiments are carried out to assess the performance of the proposed gripper on grasping and sensing. The experimental results illustrate that the proposed gripper can manipulate a variety of soft and rigid objects and remain stable even though it undergoes external disturbances.