IEEE Robotics & Automation Magazine - December 2018 - 46

The Difficulties of Underwater Manipulation
Performing fine underwater operations with current robotic
manipulation technology is still a very challenging task. In
contrast to human divers, atmospheric diving suits (ADSs),
remotely operated vehicles (ROVs), and autonomous underwater vehicles (AUVs) can readily and safely access the
depths, yet they demonstrate limited manipulation abilities.
Commercially available
underwater systems are
designed to perform simThe richness and
ple and heavy mechanical
work (i.e., construction or
complexity of the human
pipeline maintenance).
Generally, they use clawhand's sensory and motor
like end effectors that are
capable of opening/closfunctions still remain
ing and wrist-rotation
movements only. Such a
unmatched by current
technological limit means
that fine deep-water manipunderwater soft gripper
ulation tasks are still a
goal on the horizon. (For
prototypes.
our purposes here, the
term deep water refers to
any sea region that lies beneath diver depth, i.e., approximately 60 m.) This is particularly true for underwater
archeological recovery and biological sampling. However, these fields present important tasks, some of which are
described later.
Shipwrecks below diver depth present an unusual and
more direct insight into ancient cultures. Historical data indicate that the seafloor far offshore contains 20-23% of all
wrecks [1], preserved for possibly thousands of years as in a
time capsule. Deep near-shore waters, in particular, hold a

Figure 1. The developed system grasping a coin underwater.

IEEE ROBOTICS & AUTOMATION MAGAZINE

december 2018

high number of shipwrecks containing well-preserved artifacts [2]. Biological sampling operations, on the other hand,
find a typical application in coral reef studies. Reefs occurring at depths greater than 30 m, which are protected from
both human and natural disturbances [3], remain dramatically understudied when compared to other highly diverse
habitats. Another example consists of the unexploited biomasses identified in the mesopelagic zone (i.e., the water column between 200 and 1,000 m) [4]. This largely unexplored
zone is known to play a significant role in the global carbon
cycle, and, if exploited at sustainable levels without impacting
biodiversity, this biomass could be used to produce more
high-quality ingredients for the human food chain. Biologists
work to modify research design, collection methods, and
tools to best suit their needs for delicate collection, manipulation, or measurement of deep-sea organisms. The ability to
perform these tasks in situ would open up a vast potential for
expanding our understanding of sea ecology and of its modifications due to climate change.
Soft robotic hands and grippers appear ideally suited for
these kinds of operations: they grasp and manipulate delicate,
complex objects by conforming to the object shape and distributing grasping forces. Soft systems also offer improved
safety in interactions with humans and animals because of
their natural compliance and backdrivability [5]. Among the
few underwater robots currently capable of archeological
recovery (e.g., the OceanOne by Khatib and colleagues [6],
the TRIDENT I-AUV [7], [8], and the MARIS Project AUV
[9]) or biological sampling (e.g., [10]), soft grippers are
employed for specimen manipulation. However, the richness
and complexity of the human hand's sensory and motor functions still remain unmatched by current underwater soft gripper prototypes.
Problem Definition
Underwater archeology consists mainly of locating, monitoring, and preserving archeological sites. Sometimes, however,
cultural heritage artifact rescue from such sites becomes crucial, either for preservation or to prevent dispossession.
Another typical task is preventive conservation, which aims
to prevent or reduce potential damage to artifacts. As with
land archeology, recovery and conservation techniques are
essentially manual, relying on simple equipment and operator
dexterity to handle man-made objects with different shapes,
such as jewelry, dishes, weapons, and tools.
In underwater biological sampling, most specimens consist
of fragile, soft-bodied organisms, like anemones, sponges, and
corals. So scientists need to approach them with the greatest
possible care. Regarding, e.g., coral sampling, the most sustainable method is to manually collect loose fragments already
broken off from the parent colony or to gently snip a small
branch off the parent colony. More complex underwater biological operations consist of tissue biopsy techniques, which
use syringes; fluorescence measurements with lamps and
lasers; and ribonucleic acid stabilizer application. Some of
these tasks are represented in Figure 2(a)-(d). In general, many

IEEE Robotics & Automation Magazine - December 2018

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