Page 78 - Modern Robotics Building Versatile Macines

58 Modern Robotics

effective performance. The robot, called Roomba, follows a random
spiral-like path around the room, cleaning as it goes. It has no idea
where it is located in the room or where obstacles may be located.
When it bumps into something, it reverses itself (using a few special
tricks for dealing with corners and such).
Roomba does not know what parts of the room have already
been cleaned; however, this is not a problem because its modified
random path is designed to make sure it eventually reaches every
area. When the machine detects a wall, it follows it while a spin-
ning side brush collects dirt in edges and corners. There are also two
counter-rotating brushes that bring larger pieces of debris within
range of the vacuum nozzle.
Roomba has an additional feature that helps it clean efficiently.
When special sensors near the brushes detect high concentrations
of dirt, Roomba switches to a tighter cleaning pattern so it spends
more time cleaning in the immediate area. When dirt is no longer
detected, the robot reverts to its general wandering. This combina-
tion of random navigation and focused cleaning behavior results
in a quite satisfactory job—Roomba can clean an average room in
about 20 minutes.
Roomba uses infrared beams to
detect stairs and other “cliffs.”
As long as the robot is on a level
surface, the beam bounces back
to a detector. If the beam does
not bounce back, Roomba reverses
direction to avoid falling. Finally,
the robot can be confined to a
particular area by placing a special
beacon.
Even with a good design, iRo-
bot’s developers also had to master
the practical problems of mass-
producing consumer products.
The compact, unthreatening With a single research robot in a
Roomba can quietly keep floors
clean and return to its recharging laboratory, it is not a problem to
station when necessary. (Photo fix glitches or replace parts that
courtesy of iRobot Corporation) are not up to spec. With consumer