R CUE compliant grippers
Deep Sea Compliant Manipulators
- Everett Collins
- George Badlissi
Licht, S., Collins, E., Mendes, M., Baxter, C., "Stronger at depth: jamming grippers as deep sea sampling tools." Soft Robotics. Accepted June 2017. In press.
Galloway, K.C., Becker, K.P., Phillips, B., Kirby, J., Licht, S., Tchernov, D., Wood, R.J., Gruber, D.F., 2016. Soft Robotic Grippers for Biological Sampling on Deep Reefs. Soft Robotics 3, 23–33. doi:10.1089/soro.2015.0019 link
Mendes, M., *Collins, E., Licht, S. "Universal jamming grippers for deep-sea manipulation." Oceans 2016 - MTS/IEEE Monterrey, CA, September 2016.
Autonomous underwater grasping is a technically challenging task with relevance to a variety of Navy interests including sensor anchoring on structures and cables, UUV and ROV station-keeping, object recovery (including unexploded ordnance), and mine countermeasures. Other areas of potential use include underwater archaeology and biological sampling.
The use of compliant gripping mechanisms is an ongoing area of research for autonomous grasping in air. Compliant mechanisms have been shown to dramatically simplify the problem of grasping objects with unknown or poorly known geometries, orientations, and locations. Unfortunately, many of the mechanisms being developed for use in air may be prone to fail at depth as they are inherently pressure intolerant, requiring, for example, compressible materials for flexibility, laminated parts with anisotropic resilience, and cables sliding through deformable cavities in elastic structures.
We are investigating 'jamming' as a potential solution to pressure tolerant compliance in manipulators. Jamming is a physical process in which a volume of granular materials becomes rigid when packed tightly together.The jamming phenomenon can be used to grasp irregular shaped objects, using a gripper consisting of granular material in fluid enclosed by a thin membrane. This approach has been demonstrated in air, but never before in water.
We have modified the jamming gripper approach to use a pressure tolerant granular material (glass beads) with water as the interstitial fluid. Because the individual beads are pressure tolerant, and because water can be treated as incompressible, the gripper itself can operate as a compliant grasper/anchor at full ocean depth. We have demonstrated the ability to hold objects with jamming grippers at depths up to 1000m in the Atlantis Canyon.
To date, we have demonstrated the use of a jamming underwater gripper to grasp and pick up arbitrarily shaped objects. We have also demonstrated the use of jamming pads to grasp irregular and brittle objects (pretzel sticks) with a hydraulically actuated system without the need for active force sensing.
'Underfilled' Jamming Gripper Approach
Picking up various objects with a jamming gripper on a small inspection ROV.
A corroded hex key retreived from the bottom of the 4m deep acoustic tank.
By underfilling the balloon, we can also pick up a wide range of objects off a substrate which cannot support downward force on the object. Here we use 200 micron glass beads to simulate soft sediment.
Using the Deep Reef ROV (a Falcon Seaeye DR with HydroLek 5-function arm, courtesy of David Gruber of CUNY-Baruch) we have demonstrated object grasping using the hydraulic system of a 1000m rated ROV.
Toroidal Jamming Gripper
For sampling fragile objects, we can also use a gripper which utilizes both a spring mechanism and filled balloons to passively limit the total force applied.
The 'donut' shape allows us to create a small volume within the gripper, into which we can pump a fluid such as an RNA buffer, to help preserve a sample after collection.
A close up of the toroidal gripper getting ready for shipping to the Red Sea.
Open and close, with Dorick observing his creation for scale.