Figure 1 shows the original iRobot Roomba introduced in
2002. Back then, there was only
one company that made robot
vacuum cleaners and there was
only one model. I’m going to
review two of the most
prominent robot vacuum
cleaners on the market, but
more from a technical aspect.
Issues to Consider
Designs of a Robot
One might think that changing a
basic upright vacuum cleaner’s design
by adding batteries and battery-powered motors for the wheels and
impeller with some sort of simple
navigation system might turn it into a
robot vacuum cleaner. Not really. The
fact that it must use batteries presents
the greatest design hurdle.
A cheap ‘standard’ vacuum can
use a relatively powerful AC motor
and probably suck up just as much
dust and dirt as a model twice as
expensive. AC motors are
comparatively inexpensive but basic
vacuum cleaners are notoriously
power-hungry beasts, drawing up to
10 amps at 120 volts. That is 1,200
watts — far more than any battery can
supply. Therefore, inventive designers
have to create systems for robot
vacuums that can operate efficiently
from a greatly diminished power
source that will require regular
replenishment at a charging base.
Improved impeller and cavity
designs allow less powerful systems to
closely match full-sized AC models.
Simple suction alone does not pick up
dirt and debris from a carpet.
Sufficient air flow is required around
each twisted strand of carpet to reach
below the surface and cause the
particles to rise to the top to join a
larger flow of air into the vacuum
cleaner’s dust collector. One or more
rotating brushes can assist in this task.
The required length of time over
any part of a carpet determines the
robot’s speed. Faster means less time
to clean an area but hastens the job’s
completion, whereas a slower
movement means better cleaning at
the expense of a longer overall
process. A designer must be
cognizant that a robot vacuum
cleaner will not have a human behind
it, holding onto a handle and directing
it to all the places that need cleaning.
A robot vacuum must not ding walls,
suck up drapes, cats, wires, or rug
fringes, or dive down the stairs. It
must cover all carpet areas only once
— something that a human can easily
see by marks on the carpet.
Everyone loves a rousing
conversation about whose
team, product, political
party, or even robot
vacuum cleaner is best.
Usually in these
conversations, both sides
finally stop touting their
opinions and quietly step
to the side, holding to their
particular views or
manufacturers never stop
trying to convince potential
buyers of their product's
worthiness. "We've been in
business longer than our
competitors." "Our product
uses this unique
technology that surpasses
that of the other
sold more units than those
other companies." All these
and many more are typical
of the hype used to
convince customers that
they are buying or have
bought the best product.
Robot Wars: Roomba vs.
by Tom Carroll Then Now a n d
74 SERVO 01.2014
Figure 1. The original iRobot Roomba that
started it all a dozen years ago.