  For robot arms to perform everyday tasks in unstructured environments, these
robots must be able to manipulate a diverse range of objects. Today's robots
often grasp objects with either soft grippers or rigid end-effectors. However,
purely rigid or purely soft grippers have fundamental limitations: soft
grippers struggle with irregular, heavy objects, while rigid grippers often
cannot grasp small, numerous items. In this paper we therefore introduce RISOs,
a mechanics and controls approach for unifying traditional RIgid end-effectors
with a novel class of SOft adhesives. When grasping an object, RISOs can use
either the rigid end-effector (pinching the item between non-deformable
fingers) and/or the soft materials (attaching and releasing items with
switchable adhesives). This enhances manipulation capabilities by combining and
decoupling rigid and soft mechanisms. With RISOs robots can perform grasps
along a spectrum from fully rigid, to fully soft, to rigid-soft, enabling real
time object manipulation across a 1 million times range in weight (from 2 mg to
2 kg). To develop RISOs we first model and characterize the soft switchable
adhesives. We then mount sheets of these soft adhesives on the surfaces of
rigid end-effectors, and develop control strategies that make it easier for
robot arms and human operators to utilize RISOs. The resulting RISO grippers
were able to pick-up, carry, and release a larger set of objects than existing
grippers, and participants also preferred using RISO. Overall, our experimental
and user study results suggest that RISOs provide an exceptional gripper range
in both capacity and object diversity. See videos of our user studies here:
https://youtu.be/du085R0gPFI
