How Robotic Vacuums Work

Roomba Cleaning

According to iRobot, more than half of Roomba owners name their little vacuuming buddy. Electrolux, the maker of the high-end Tribolite robotic vacuum, reports that it receives letters and pictures from families that own its product. Still, most people don't buy a robotic vacuum because they're looking for a low-maintenance pet. They buy it because their floors get dirty.

Roomba Red has a three-part cleaning system:


If you remove the agitator assembly, you can see two dirt sensors:

  • The spinning side brush sticks out past the Roomba shell to reach spots the underside can't access. It spins along walls to kick up dirt and direct it into the vacuum area. The brush on the opposite side of the Roomba directs any wayward dirt back under the unit to be sucked up.
  • The agitator on the underside of the Roomba consists of two counter-rotating brushes that grab dirt and other debris and deposit it directly in the dirt bin.
  • The vacuum sucks up dirt and dust as Roomba moves along the floor.

You typically need to empty the dirt bin at least once for each room the Roomba vacuums, and possibly two or three times depending on how dirty your floors are. Roomba doesn't know when the bin is full -- it just keeps going. There's a filter you'll need to replace when it gets too clogged, but there's no vacuum bag -- you just dump the bin and put it back in the unit.

As far as cleaning power goes, the iRobot Web site states that Roomba has "as much suction as a standard upright," although it offers no specifications. When HowStuffWorks tried out the Roomba Red, we found that it cleans quite well on hardwoods and linoleum, and it picks up a good amount of the dirt and pet hair on low- and medium-pile carpet. According to iRobot, Roomba is not intended for deep-pile carpet.

Now, when you're pushing a vacuum through your home, you make decisions. If you see that an area is especially dirty, you spend more time there. When you pass from the linoleum of the kitchen to the carpet in the dining room, you turn a knob on the vacuum so it can achieve its optimum efficiency on the type of floor its cleaning. As a robot, Roomba should be able to at least partially replicate a human's ability to clean effectively.

In order to figure out which areas need extra cleaning, Roomba Red has two dirt sensors located immediately above the agitator brush. These dirt sensors are acoustic impact sensors. When the agitator kicks up a large amount of dirt, the dirt causes more vibration when it hits the metal plates of the sensors. The sensors detect that increase and tell Roomba to go over the area again. To make the transition between floor types, Roomba's cleaning deck (which houses the agitator setup) automatically adjusts its height when it senses a half-inch (1.3-cm) rise in the floor surface.

One thing Roomba can do that a human and an upright vacuum can't is get completely under furniture. Because Roomba Red is only about 3.5 inches (9 cm) tall, it can easily get under most coffee tables, night stands, beds and some couches. The ability to clean under furniture is arguably one of the biggest draws of the robotic vacuum.

The Roomba Red is a handy device, but it's only one example of a vacuuming robot. In the next section, we'll check out some of the other robotic vacuums available today.