Abstract
In this work we experimentally demonstrate (a) that the holding strength of universal jamming grippers increases as a function of the jamming pressure to greater than three atmospheres, and (b) that jamming grippers can be operated in the deep sea in ambient pressures exceeding one hundred atmospheres, where such high jamming pressures can be readily achieved. Laboratory experiments in a pressurized, water-filled test cell are used to measure the holding force of a "universal" style jamming gripper as a function of the pressure difference between internal membrane pressure and ambient pressure. Experiments at sea are used to demonstrate that jamming grippers can be installed on, and operated from, remotely operated vehicles at depths in excess of 1200 m. In both experiments, the jamming gripper consists of a latex balloon filled with a mixture of fresh water and ∼200 μm glass beads, which are cheaply available in large quantities as sand blasting media. The use of a liquid, rather than a gas, as the fluid media allows operation of the gripper with a closed-loop fluid system; jamming pressure is controlled with an electrically driven water hydraulic cylinder in the laboratory and with an oil hydraulic-driven large-bore water hydraulic cylinder at sea.
Highlights
Robotic sampling of fragile and irregularly shaped objects is often a critical component of deep sea biological and archaeological investigations
In this work we experimentally demonstrate (a) that the holding strength of universal jamming grippers increases as a function of the jamming pressure to greater than three atmospheres, and (b) that jamming grippers can be used for deep sea grasping tasks in ambient pressures exceeding one hundred atmospheres, where such high jamming pressures can be readily achieved
The influence of initial volume and gripper weight on performance for different target geometries is a necessary area of future work. In this effort we demonstrate that the universal jamming gripper is a viable deep water sampling technology
Summary
Robotic sampling of fragile and irregularly shaped objects is often a critical component of deep sea biological and archaeological investigations. Even with highly skilled pilots, collecting samples at any reasonably complex site with an ROV is difficult and time consuming. It is not atypical for a >2000kg robot with a potential grip closure strength of >1000N to be used to sample objects with a weight of only a few grams in water. The fundamental danger in these sampling tasks is that a rigid gripper on a non-back drivable arm could make unintended contact with a priceless, fragile object with a huge amount of momentum driving the gripper and the arm. Soft robotics are attractive in large part because their inherently compliant structures can passively eliminate accidental shock loading on sampled objects
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