Down the Rabbit Hole: Exploiting Airflow Interactions for Morphologically Intelligent Retracting Vacuum Grippers

Suction cups and closed bellows actuators are commonly used in industrial pick and place tasks. They can be combined and actuated by a single negative pressure line, providing a simple coupling between suction and actuation. However, the capabilities of this - seemingly very simple - system go beyond just being able to grasp and retract an object. By varying the morphology of the suction cup and by tuning airflow between the two serially connected elements, retraction of the bellows changes and functional embodied behaviours emerge. This work explores the novel concept of flexible Sucking & Retracting Bellows (SuReBellows) comprised of a suction cup and a long-stroke bellows actuator, and how they can be tuned for morphologically intelligent behaviours. Our primary investigation explores how the retraction of the bellows can be tuned to enable "exploration" on the surface of an unknown object in order to make a good vacuum seal contact for grasping. Several suction cup designs were tested in grasping a general object set, by varying the compliance and airflow between the bellows and the suction cup. The results show that SuReBellows can explore the surface of objects and find grasp points just by cycling one pressure signal for actuation, with the search pattern and adaptability encoded in its morphology. The grasping force of the system was then investigated. Finally, demonstrations of interesting applications such as bin picking and grasping in confined environments are shown.