Universal robotic gripper based on the jamming of granular material

This paper resulted from a close collaboration with iRobot (link) and presents a new architecture in soft robotics that utilizes particulate jamming technology. A novel concept of actuation is described that utilizes jamming technology to modulate the direction and magnitude of the work performed by a single central actuator. Jamming “activators” modulate work by jamming and unjamming (solidifying and liquifying) a granular medium coupled to a core actuator. These ideas are demonstrated in the Jamming Skin Enabled Locomotion (JSEL) prototype which can morph its shape and achieve locomotion. Next, a new actuator, denoted a Jamming Modulated Unimorph (JMU), is presented in addition to the JSEL topology. The JMU uses a single linear actuator and a discrete number of jamming cells to turn the 1 degree of freedom (DOF) linear actuator into a multi DOF bending actuator. Full characterization of the JMU actuator is presented, followed by a concluding argument for jamming as an enabling mechanism for soft robots in general, regardless of actuation technology.

• E. Steltz, A. Mozeika, J. Rembisz, N. Corson, and H.M. Jaeger, “Jamming as an Enabling Technology for Soft Robotics”, in Electroactive Polymer Actuators and Devices (EAPAD) 2010, ed. Yoseph Bar-Cohen, Proc. SPIE vol. 7642 (Conference on Smart Structures/NDE 2010, March 7-11, 2010, San Diego). pdf

Universal robotic gripper based on the jamming of granular material

Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shape and surface properties remains, however, challenging. Most current designs are based on the multifingered hand, but this approach introduces hardware and software complexities. These include large numbers of controllable joints, the need for force sensing if objects are to be handled securely without crushing them, and the computational overhead to decide how much stress each finger should apply and where. Here we demonstrate a completely different approach to a universal gripper. Individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. We find that volume changes of less than 0.5% suffice to grip objects reliably and hold them with forces exceeding many times their weight. We show that the operating principle is the ability of granular materials to transition between an unjammed, deformable state and a jammed state with solid-like rigidity. We delineate three separate mechanisms, friction, suction, and interlocking, that contribute to the gripping force. Using a simple model we relate each of them to the mechanical strength of the jammed state. This opens up new possibilities for the design of simple, yet highly adaptive systems that excel at fast gripping of complex objects.

• Brown, E., Rodenberg, N., Amend, J., Mozeika, A., Steltz, E., Zakin, M., Lipson, H., Jaeger, H. (2010) "Universal robotic gripper based on the jamming of granular material," Proceedings of the National Academy of Sciences (PNAS), Vol. 107, no. 43. link to pdf file (incl. suppl. material)
• Link to more details, high-res images, FAQs, and several nice movies at the website of our Cornell collaborators, John Amend and Hod Lipson
• Link to list of 170+ popular press articles written about the jamming gripper (compiled by John Amend @ Cornell)
• Link to U of Chicago press release
• Link to Cornell University press release