SKIING fans call it a hot dog: twisting head over heels in mid-air and
landing upright on your skis. Now a team of cybernetics experts has developed a
ski-jumping robot that can pull off the same stunt. And getting the mechanics
right could lead to a new breed of agile space robots, they say.
The ski-jumping droid is the brainchild of Kazuo Yoshida at Keio University
in Yokohama. It looks pretty unprepossessing鈥攋ust two boxes of circuitry
coupled by a motorised universal joint, with a pair of plastic skis fixed
beneath the lower box. It stands half a metre high and weighs 4.5 kilograms.
Like a real skier, the robot uses gravity to pick up speed on a ski slope,
and a ramp to get airborne. Then it has to twist part of its body relative to
the rest to pull off the hot-dog manoeuvre. Instructions from a very fast
parallel-processing computer chip called a transputer control two high-torque
electric motors connected to the universal joint, enabling the robot to make
controlled somersaults and twists. 鈥淭he challenge was to have the robot both
twist and turn in the air. Combining both moves is very difficult,鈥� says
Yoshida.
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To get their machine working as well as possible for a given ski slope,
Yoshida鈥檚 cyberneticists used the emerging technology of 鈥済enetic
algorithms鈥濃�攐ften likened to natural selection鈥攖o hone the software
that controls it. Using data from many trial runs in which the flailing droid
piled helplessly into a vat of polystyrene beads, they gradually bred control
software that can reliably land the machine on two skis.
The technology could be used to control robots designed to build and maintain
orbiting spacecraft, Yoshida says. Staying the right way up while floating in
microgravity poses similar problems to getting the robot skier to land on its
skis.
Yoshida鈥檚 droid could one day aid such space robots as NASA鈥檚 robonaut
(快猫短视频, 25 September 1999, p 20),
which is controlled remotely from a
spacecraft. Robonaut is being designed to respond quickly to emergency repairs
on craft like the International Space Station鈥攁nd the ability to shift
weights, ski-droid style, might make it more useful.