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Traditionally,
Atmospheric Diving Suits (ADS) – such as
the ‘JIM’, ‘Wasp’,
‘Newtsuit’, and ‘Hardsuit’
– have relied on a two-jawed ‘manipulator’ in
place of the human hand. This manipulator operates much like a
pair of pliers: by squeezing the handles inside the ADS, a set
of jaws close on an object outside of the suit. The difficulty
involved in executing an underwater task that requires significant
manual dexterity can be demonstrated on the surface by attempting
the same task using only two pairs of pliers. With practice and
good eye/hand coordination skills, the operator can perform simple
tasks; with extensive experience it is possible to do some rigging,
shackle-pin removal and replacement, and similar work; however,
to complete complex tasks, an ADS pilot needs the ability to use
his or her hands in the same manner as a Scuba or helmet diver.
Until now this has not been possible.
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Much is made
of the ‘opposed thumb’ of humans, with the suggestion
that the ability to grasp distinguishes us from more ‘primitive’
animals. If it were that simple, crabs would rule the world! The
kinesiology of the human hand is amazingly complex, but it comes
down largely to the ability of the human thumb to ‘index’.
That is, to directly oppose each of the individual fingertips,
to centre itself if more than a single finger or digit is employed,
as in grasping, and to do all of this reflexively, without conscious
thought.
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simple experiment will serve to illustrate the point: put a pen
or pencil down on a desk or table. Pick it up with your thumb and
forefinger. Note that your thumb is now directly opposite your forefinger.
Of course it is! If your thumb and your forefinger were offset,
then the pen would simply spin out of your grasp. Try it. Now pick
up the pencil again with your thumb, your forefinger and your index
finger – a ‘three-jawed’ approach. Again note
that your thumb automatically indexes to the centre – the
space between the two fingers. Try it again with three fingers and
your thumb. Same result: your thumb indexes to the centre. It is
not simply the ‘opposable thumb’ that gives some primates
(including humans) the ability to carry out complex manipulative
tasks, it is the ‘indexable’ thumb! |
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The
development of an ADS manipulator, or end-effector, that could match
or nearly match the dexterity of a gloved hand would require that
the external ‘fingers’ not only mimic the exact movements
of the inside ‘master’ hand, but also provide full,
100% reflexive index-ability of the external thumb, in concert with
the number of other digits employed. In addition, the outside ‘slave
hand’ should also provide directly proportional sensory feedback
of pressure, weight, etc., to the inside master hand (yours!). |
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Previous attempts to build
such a device have achieved reasonably close mechanical matches
to the geometry and motion of the individual phalanges of the
fingers, but the designers and engineers were not able to provide
a true, rotating, index-able thumb to oppose those fingers.
The Nuytco
‘Prehensor’ does just that. Pick up a ball, throw
it against a wall, and catch it on the rebound. Pick up a pen
and sign your name on a piece of paper. Pick up a nut with the
tips of the thumb, forefinger and index finger, start it on a
bolt in exactly the same manner that you usually do, then spin
it up the flange with one finger before you pick up a wrench to
tighten it.
You literally
have to see it to believe it!
The unique
capabilities of the ‘Prehensor’ were
developed specifically with the Nuytco ADS ‘Exosuit’
in mind, but the system can easily replace existing simple jaw-style
manipulators for use on ADS units. Completed prototypes currently
are undergoing exhaustive beta testing before limited production
begins. An electronically-controlled version is under development
for use on remotely operated vehicles (ROV’s) and deep submersibles.
There also is considerable interest and discussion with the national
space agencies of several countries on the use of the ‘Prehensor’
as a possible alternative to the conventional space-suit gloves.
Nuytco has
produced a DVD showing the stages of evolution of the ‘Prehensor’
and examples of different versions working on various tasks. Copies
of this DVD are available to qualified potential users. Please
contact us with a brief description of your company and intended
use.
(All trademarks
are the properties of their respective holders.)
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