relatively small number of robots —
between 10 and 100 is typical — the
envisaged operation system could
involve hundreds or thousands of very
small robots, or even millions of
microscopic units.
This concept has served insects
extremely well. ‘If we can achieve it, then
it promises to build a system which has
an extraordinary level of robustness. It
would tolerate very high levels of failure
of individual robots, with the overall
system just carrying on regardless and
doing the job, albeit possibly slower and
less efficiently,’ said Winfield
Swarms are so efficient that they
might even be able to tolerate individual
robots doing completely the wrong thing.
‘Leaf-cutter ants will always have a
number of individuals carrying bits
of leaf the wrong way, but it doesn’t
matter,’ he said.
An individual swarm robot will be
equipped with some way of moving
around, an array of sensors so that it can
detect other robots and aspects of its
environment, and some method of affect-
ing the environment, such as a system for
attaching to other robots; as well as some
processing power to operate the control
algorithms.
Although Winfield calls the
individual robots ‘simple’, this actually
leads to complex little machines; and
advances in miniaturising these
types of technology have led to the
development of swarm robotics.
The field has emerged only in the last
10 years, Winfield said. ‘It has allowed
us to build robots small enough, and
reliable enough, to have significant
numbers of them and to run meaningful
experiments,’ he said.
‘You need sufficient computing,
communication and battery power for
these fairly complex systems, and power
management and sensing are critical.
Experiments tend to take several hours,
so they need to be able to run for a fairly
long time and be reliable.’
Being able to build robots is crucial,
because computer simulation is not a
reliable method for studying swarms.
This is because there is inherent random-
ness in a swarm of robots; wheeled robots
will have wheels which are not all
precisely round; there will be minor
differences in gearboxes; the environ-
ment will interact with the robots in
unpredictable ways.
‘These small differences and the noise
in the environment somehow assist or
‘If you approach the problem using a large
number of simple robots, the solution is more
robust and resilient’ Alan Winfield, Bristol Robotics Laboratory
enable the self-organisation and
emergence of behaviours in ways that
we don’t understand,’ said Winfield.
‘Computers aren’t good at randomness;
they’re always pseudo-random.
Roboticists have found that they can
demonstrate things in simulation, but
when they transfer them to real robots,
they don’t see the same behaviour.’
In terms of applications, swarms are
well suited for any activity that falls
into the ‘foraging’ category. ‘Any
application where you have stuff — any
sort of stuff — spread out in the
environment, and you have to find it
and do something with it, whether it’s
the EnGIneeR 16–29 JUNE 2008 23
on land, sea, in the air or in space, is a
possibility for swarm robotics,’ said
Winfield.
‘All sorts of exploration and
surveying, through to mining and
harvesting, and areas like construction
and search and rescue are also good
targets, as are medical applications.’
Medicine is one area where even
one robot doing the wrong thing could
be disastrous. However, borrowing
another property from nature, the
swarm could be equipped with an
immune system that detects aberrant
units and isolates them so that they can
do no damage.
ROBOTICS
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