A low cost, multi-axis robot that mirrors the actions
of a human limb could prove invaluable to the disabled. Tom
Shelley reports
The star of, and the only non-Japanese exhibitor at, the 'Robot
Dream Exposition', part of Robodex 2002 in Yokahama, was a low
cost robot designed and built in Britain.
The arm-like robot, which imitates all the movements of its
human equivalent, uses more than 40 pneumatic 'muscles' to
produce 29 individual axis movements. Its control system is based
on low-cost automotive CANbus electronics and a free version of
Linux.
Among its predecessors is a completely human-like walking robot,
and a very low cost and safe-to- use physiotherapy aid for home
use; the development of which is currently stalled by the lack of
a suitable compressor.
The Shadow Robot Company, based in North London, is a small
company of robot enthusiasts. The company has earned a world-wide
reputation for tackling ambitious robotics projects on very
limited budgets; projects some of which larger companies would
not even attempt.
The team's latest development is a fully articulated hand and
arm. It started out as a DTI SMART Award supported project and
has since attracted £50,000 from the National Endowment for
Science Technology and the Arts (NESTA) - the objective being to
turn it into a commercial product.
Movement is achieved by inflating rubber tubes enclosed by
polymer net bags, in a way described in a past issue of Eureka.
These are about the cheapest actuators that one can devise.
The arm's design is such that, for example, 24 axis of
movement are available for fingers, thumb and wrist, plus five
more from the shoulder. The forearm section has 35 separate
actuator muscles, some of which oppose each other while others
are opposed by springs.
The hand and arm is usually demonstrated by running
pre-programmed scripts. An alternative method is also available
which uses direct instructions fed to the arm via a commercially
available cyber glove.
For use by the disabled, the team intends to combine the data
glove input with voice control and "a few pushbuttons".
It is intended to program in most operations on a teach-and-learn
basis and then make these available as 'canned cycles'.
Part of the development programme involves working with disabled
people to develop solutions for different needs. And a target
task is that the machine should be able to collect a glass of
water - a complicated task given that even picking up a glass or
a cup dictates the need to accommodate various shapes with
differing handles of different sizes.
Positional feedback from the fingers is by Hall effect rotary
sensors, each of which detects the angular position of a ring
magnet from changes in magnetic flux density and direction.
Wiring is simplified by using a four-wire CANbus to take data to
and from the palm of the hand. Surface mount electronics reduce
size, and Real Time Linux simplifies programming.
It is hoped to have a working prototype of a commercial version
finished within a year and to begin production within the next
five years. Other applications for the arm and hand are seen in
tele-operation with hazardous substances, robotic handling of
soft and varying objects and animatronics.
Open movement
The software will be open so that anyone can devise add-ons and
enhancements. At this stage, it is envisaged that the supporting
machinery for the arm will drive itself around on wheels and not
walk, even though walking robots are a Shadow Robot Company
speciality.
However, as Shadow's Richard Greenhill points out: "Bipedal
walking is hard." Which is why most successful walking
robots known to Eureka have four, six or even eight legs.
Nonetheless, Eureka was shown a small, two- legged walking robot
demonstrator just under a metre tall. Also powered by air
muscles, it has reached the point where it can move with help,
rather like a toddler learning to walk. It seems the machine
balances itself by sensing pressure variations under its feet
rather than by using a level sensor to detect vertical
orientation
Human-like robots, as envisaged by science fiction writers, may
well be the ultimate future, but simpler machines based on the
same technologies undoubtedly have more immediate commercial
promise.
One of these is a machine for exercising human joints with a view
to gradually increasing their range of movement. Stiffening
joints may result from old age, an accident or multiple
sclerosis. Treatment requires the attentions of a qualified
physiotherapist and/or the use of a Continuous Passive Motion
machine. This is a fairly large and expensive piece of equipment,
which is normally available only in a hospital and still requires
the attention of a skilled operator.
What is needed is something cheap enough for home use, capable of
being re-programmed from time to time and, above all, 100% safe.
The Shadow Robot Company undertook a feasibility study in
conjunction with the Centre for Disability Research, part of
University College, London, based at Stanmore Hospital. The study
was to decide whether such a machine could be built with Shadow's
technology. The machine has since been developed to the point
where it can be trialled, with further interest now being shown
by a German research institute.
The main barrier to implementation at the present time,
surprisingly, is the inability to source suitable compressors.
Greenhill says he is looking for machines which are both cheap
and quiet, delivering up to 30litres/min of air at up to 3 bar.
Anyone who has such a product should get in touch with him at
rgreenhill@shadow.org.uk.
Greenhill claims that Shadow Robot also has technologies suitable
for machines operating in space, at gas pressures a few bar
greater than vacuum and undersea. And, by the way, the ironing
robot featured on the television programme 'Tomorrow's World'
shown on Millennium Eve was made by Shadow Robot at just three
weeks notice. (More information at www.shadow.org.uk and www.nesta.org.uk )
* Relatively low cost robot arm/hand has 29 individual axis
movements
* Cost effectiveness comes from use of low cost pneumatic
'muscle' actuators, CANbus and Real Time Linux
* Technology is immediately applicable to medical systems,
tele-operation and animatronics
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