Soft Enveloping Gripper Driving Several Fingers by 3D Snap Through Buckling Mechanism

It is difficult to automate the grasping of delicate fruits such as peaches, which require sensitive work. Envelope grasping is an effective approach for grasping such objects due to its large contact area with the object. A method to realize envelope grasping is the fingered gripper, which can perform grasping that follows the shape of the object through compliant interaction. However, this method has the problem that it is structurally difficult to fill the space between fingers. Another method of achieving enveloping grasp is to envelop the object by membrane. This method can touch the object without gap between fingers, but it is difficult to grasp unexpectedly large objects because it cannot deform as large as a fingered gripper. In this study, we propose a soft gripper that realizes envelope grasping while largely deforming several fingers. The proposed method opens and closes using the turning over of the hemispherical shell due to the 3D snap through buckling mechanism. By employing this mechanism, allowing all objects touching the edge of the hemispherical shell to be moved simultaneously and significantly, fingers arranged without gaps can be deformed largely. Another advantage is that it requires no energy to maintain the grasping state due to its bistable, snap through buckling characteristics. In this paper, we present a design methodology based on specific examples and an evaluation of performance.