Why Teams of Co-Operating Robots Make Good Planetary Explorers

http://www.ras.org.uk/html/press/pn0408ras.html

RAS Press Notice PN04-08 (NAM 05):
Why teams of co-operating robots make good planetary explorers

Date: 25 March 2004

Issued by Jacqueline Mitton and Peter Bond, RAS Press Officers.

National Astronomy Meeting Press Room phones (30 March - 2 April only):
+44 (0)1908 659726 +44 (0)1908 659729 +44 (0)1908 659730

CONTACT DETAILS ARE LISTED AT THE END OF THIS RELEASE.

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WHY TEAMS OF CO-OPERATING ROBOTS MAKE GOOD PLANETARY EXPLORERS

Will swarms of co-operating robots one day be exploring some of the most
intriguing worlds in the solar system? James Law, an engineer who is a
doctoral student at the Open University, supports the idea that using whole
teams of robotic explorers working together offers distinct advantages,
especially when it comes to tackling the challenges presented by remote
bodies such as Europa and Titan. In a presentation on Wednesday 31 March at
the Royal Astronomical Society's National Astronomy Meeting at the Open
University, he will be reviewing some current ideas on co-operative robot
technology and suggesting how it might be applied to a Titan mission with a
concept for a 'Master' robot controlling a bevy of 'Slaves'.

Of the 17 landers sent to investigate Mars, only 5 have survived to perform
their missions. In spite of this, scientists are already looking for their
next planetary targets, with Saturn's moon Titan and Jupiter's moon Europa
being distinct possibilities. Given both the greater distances involved, and
extreme climatic conditions, how can the likelihood of a successful robotic
surface mission be increased? Although robotic rovers have become the
preferred choice over static landers, due to their greater versatility, the
addition of motion systems increases their weight and reduces the
reliability of these already complex mechanisms.

Advantages of teamwork

One alternative, proposed in 1989 by Rodney Brooks of the Massachusetts
Institute of Technology, is finally coming to fruition - the idea of
replacing solitary rovers with swarms of cooperative robots. With scientific
equipment evenly distributed between them, each rover can be made smaller,
lighter, and less complex. These robots can then work together or
independently, in order to complete the mission objectives.

This approach has several distinct advantages. Launch costs could be reduced
and soft landings achieved by delivering lighter payloads. Robustness is
improved, since a critical failure on any rover is isolated from the rest.
Although losing a rover may restrict the capabilities of the swarm, it is
not likely to result in termination of the mission. Indeed, in many cases
the affected rover will still be able to play a useful, though limited role.

Robotic swarms permit a variety of new missions, such as simultaneous
measurements over wide areas, useful in climate monitoring and seismic
sounding, or multiple experiments performed concurrently by different
robots. Rovers can also work together to access areas of greater scientific
interest, for example cliff faces. James Law cites David Barnes of the
University of Wales at Aberystwyth, who is developing a swarm of aerobots -
flying robots which could be used for terrain mapping or deploying smaller
micro rovers. Another benefit of using small cooperative rovers is that
additional robots can be launched and integrated into the swarm to extend a
mission, enabling new experiments, or replacement of lost and damaged
rovers.

Robots for Titan

In his talk, James Law will present his own vision for a mission to Titan.
Though we have to wait for the Huygens probe, due to land on Titan early
next year, to discover the true nature of Titan's surface, it is likely to
be mixed. "In this situation, a Master-Slave robot configuration with a
variety of transport modes could be favourable," he suggests. "A 'Master'
lander supplying power and communications provides an outpost for a number
of small 'Slave' rovers and balloons. The lander would be equipped with a
range of scientific packages, which it could distribute amongst its slave
robots depending on the environment around the landing site. These
subordinate robots are then able to act either cooperatively - for example,
to dig and image a trench in order to investigate its geological layers - or
on their own, analysing or collecting samples and returning them to the
lander for more in-depth analysis. The rovers would return to the lander to
recharge their batteries and change their scientific payloads. Robots
capable of operating in a liquid environment could be dispersed on any Titan
sea to measure wave motion, perhaps by balloon, then be sacrificed, by
'drowning', to measure conditions below the surface."

Exploring Europa

Among schemes proposed by others that James Law will review is one for the
exploration of Europa, devised by Jeff Johnson of the Open University and
Rodney Buckland of the University of Kent. It involves Self Organising
IMAging Robots, or soimars, small cube-shaped robots each carrying a
single-pixel imaging device (such as a photodiode) and weighing as little as
10 grams. Each one is able to communicate with its neighbours and is capable
of moving in water, using small propulsion screws. A swarm of these tiny
robots could be deployed into a sub surface ocean on Europa to image the
environment.

A transport craft containing communications and power facilities would land
on Europa's ice crust and release an ice-penetrating device containing the
soimars. This device would bore through the ice and release the soimars into
the ocean. The soimars then self-organise into a stack, aligning their
imaging devices. By cooperatively swimming, the stack scans an area under
the ice. If a single imaging device fails, the faulty soimar is simply
released and the swarm reorganises to form an error free array. This also
enables more soimars, perhaps from subsequent landers, to join the swarm and
improve the image resolution. In this configuration, the soimars are
physically attached to one another. An alternative use would be to equip
them with touch sensors and have them swim as a dispersed cloud along the
ocean floor, mapping its elevation. A simulation has been developed at the
Open University to demonstrate the self-organising behaviour of the swarm.

A mechanical workforce for Mars

The Jet Propulsion Laboratory (JPL) has research underway on cooperative
robot teams, including robotic work crews for carrying large items, robotic
excavation teams, and robots that can rappel one another down steep cliff
faces. An objective of this work at JPL is to deploy a robotic workforce on
Mars to construct mining and refining facilities, which will provide fuel
for future human missions. With proposals to land men on Mars, and
eventually more distant locations, these robotic work crews will be
indispensable in both investigating the destinations, and creating outposts
to support our arrival.

CONTACT

James Law
Dept of Design and Innovation, The Open University,
Walton Hall, Milton Keynes MK7 6AA

Phone: (+44) (0)1908 652964
E-mail:

(or via the NAM press room during the meeting)