A Positive Pressure Universal Gripper Based on the Jamming of Granular Material (FAQ)
Frequently Asked Questions (FAQ)
What exactly did you do in this project?
Universal jamming grippers are a concept that we previously presented, where a flexible membrane filled with granular material can be quickly hardened by evacuating the air from within the membrane. This change in hardness due to vacuum-packing is an example of what is known as the "jamming phenomenon," and it enables a jamming gripper to pick up objects of varying shape.
Now, we have greatly improved the performance of jamming grippers by reversing the process and using high pressure air to unjam and reset the gripper. This innovation produces unexpectedly high performance gains in the gripping function, and also enables a new capability to "shoot" objects by fast ejection.
Why is this difficult?
The design and development of universal robotic grippers (universal because they can pick up widely varying items: a ball, a coin, a screw, a spring, a cup, etc.) has proven to be a difficult task for engineers. The typical approach for designing a universal robot gripper is to take inspiration from the human hand. These mechanical human-like robot hands are often incredible machines, but they are also complex and expensive. Our approach is a sharp deviation from the human-inspired approach, and it proves to be simple, low cost, and still highly capable.
Prior to this work, we are unaware of any robot grippers that are able to shoot or throw objects a comparable distance with similar accuracy. Certainly throwing has been demonstrated with robot arms before, but the momentum for throwing is typically provided by the arm motion, while the gripper simply releases the object at the optimum time. Here, the entirety of the shooting function is provided by the gripper.
What applications are there?
Our gripper will be useful in situations where a robot needs to grip or pick up a wide variety of items, including items it may have never seen before. Specific applications that come to mind are: military robotics and improvised explosive device (IED) defeat missions; consumer and service robotics in unstructured environments like the home; and industrial and manufacturing robotics able to perform of a wider variety of gripping tasks than currently possible. The gripper may provide safety benefits in the soft state it assumes between gripping tasks.
The shooting capability in particular could be useful for helping robots extend their workspace. The shooting is not accurate enough to be applicable in the high-precision tasks where many robots are employed (you couldn't assemble a circuit board by shooting the parts from across the room for example). However, as robots move into increasingly unstructured environments (like the home), applications like sorting objects into bins or throwing away trash come to mind. Other ideas are shown in the video of our shooting demonstration.
What field(s) does this work fall under?
This work falls primarily under the field of mechanical engineering, as this paper focuses primarily on the design and performance of a new robotic gripper. The lead researchers for this project are mechanical engineers from here at Cornell. The field of physics is also closely related to this work, and about half of the authors are physicists from the University of Chicago, who contributed a focus on the jamming transition that enables the gripper’s function.
What inspired this work?
The inspiration for our work with jamming grippers came while we were exploring granular jamming for potential applications in DARPA’s Programmable Matter project. The key insight that inspired this project was that this fundamental process of jamming could be exploited for useful materials in robotics.
After working with our original gripper for some time, we found difficulty in performing repeated gripping tasks because the gripper would sometimes fail to reset from the vacuum-packed state. Reversing the air pressure seemed like a natural solution, but we were surprised to find how much of a performance increase it provided, and the new shooting capability was totally unexpected.
What are your next steps?
Our immediate goal is to further develop the gripper we have presented, and to deepen our understanding of how to best utilize the jamming phenomenon for this purpose. In the long term we are striving to apply jamming in a more general way to adaptive robots and structures that might reconfigure, locomote, or recover from damage.
Who are you?
This research was a collaboration between Cornell University and the University of Chicago. Team members from the Creative Machines Lab here at Cornell are John Amend and Hod Lipson. John Amend is a Ph.D. student and Hod Lipson is an Associate Professor. Please return to the research summary for more information about our collaborators.
Who funded this work?
This work was supported by DARPA/DSO through United States Army Research Office Grant W911NF-08-1-0140.