A WHEELCHAIR that can automatically move elderly or disabled people from one
room to another has been developed by researchers in Japan. People can also be
given partial control over their chair with a joystick.
The rapid increase in the number of elderly people has become a critical
problem in many societies, says Hiroaki Seki, who designed the wheelchair with
his colleagues at Kanazawa University. Because there are often not enough staff
in old people鈥檚 homes, patients can鈥檛 always be moved when they want to be.
A series of beacons mounted on the ceiling helps the chair to find its way
around. The chair sends regular wireless signals to the two nearest beacons and
the beacons then reply with ultrasonic pulses. These are picked up by two
receivers on the back of the chair. By measuring the delay between the wireless
signal and the ultrasonic pulse, the chair calculates the distance to each
beacon.
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By comparing how far away each of the two beacons is, the chair can then
calculate where it is to within 25 millimetres. To make sure that the beacons鈥�
signals don鈥檛 interfere with each other the chair only activates the two nearest
ones. As a cross check, the chair also stores a map of the building in its
memory and uses its wheels as an odometer鈥攃alculating progress from one
beacon to the next by counting the revolutions of its wheels. By tallying the
position that it calculates from the beacons with the odometer, the chair can
detect if obstacles are delaying the pulses. 鈥淓missions are always checked with
odometry readings from the last position, to make sure there are no problems
with obstacles or reflections from walls,鈥� says Seki.
Illah Nourbakhsh, a robotics engineer at Carnegie Mellon University,
Pittsburgh, questions the amount of use a fully autonomous wheelchair will have,
but says there is plenty of scope for assisted navigation for people with poor
motor skills.
鈥淚t鈥檚 an interesting idea to have the environment as part of the system by
way of the beacons,鈥� Nourbakhsh says. He is adapting his own semi-automatic
wheelchair to work outdoors.