Underactuated grippers represent an appealing solution that allows complex objects to be grasped and manipulated via passive adaptation of the hand with objects via simple control inputs. The grasping ability can be further improved in combination with vacuum gripping, i.e., by outfitting the gripper phalanges with suction cups, that remains a largely underinvestigated solution. This paper presents a novel gripper, referred to as POLYPUS, that features underactuation and vacuum grasping to handle uneven and even objects made of different materials, including cardboard, glass, sheet metal, and plastic. Being characterized by a solid frame, POLYPUS does not fall in the soft gripper category, while preserving similar adaptability. It provides unique load lifting capacity that ranges from light to heavy objects, whereas most of the existing grippers are tailored for a specific target payload. Being modular in design, POLYPUS can be easily reconfigured for a wide range of object sizes and applications. Results obtained from an extensive set of simulations are included to evaluate the grasping performance expressed in terms of the minimum suction force to handle objects of varying shape, material, and pose.
