Description

The unit is a disc, 13.4 inches (34 cm) in diameter and less than 3.5 inches (9 cm) high. A large contact-sensing bumper is mounted on the front half of the unit, with an infrared sensor at its top front center. A carrying handle is fitted on the top of the unit. Depending on the model, it may come with between one and three "Virtual Wall" infrared transmitter units.

There have been three generations of Roomba units: The original Roomba, Pro, and Pro Elite; the second-generation "Discovery" series with a larger dustbin, dirt detection, and optional home base; and the newest 5xx series.

The Roomba operates with internal nickel-metal hydride batteries and must be recharged regularly from a wall plug, although newer second- and third-generation models have a self-charging homebase they automatically try to find (via its infrared beacon). Charging on the homebase takes about three hours. All second- and most third-generation Roombas can be used with the homebase, even if they do not come packaged with it. First- and second-generation models came packaged with a twelve-hour charger, although a three-hour rapid charger could also be used with them.

First-generation models needed to be told the size of the room via three room size buttons (Small, Medium, and Large), but this is no longer required with second and third-generation models.

Operation

When the "clean", "spot", or "max" button is pressed, the Roomba begins its work. The contact bumper detects bumping into walls and furniture, and the Virtual Walls limit the Roomba to the areas that the owner desires with an infrared signal. Special Scheduler Virtual Walls can be programmed to turn on at the same time the Scheduler-enabled Roomba is activated. Four infrared sensors on the bottom of the unit prevent it from falling off ledges. Second- and third-generation models have additional dirt sensors that allow them to detect particularly dirty spots and focus on those areas accordingly.

Unlike the Electrolux Trilobite vacuuming robots, Roombas do not map out the rooms they are cleaning. Instead, they rely on a few simple algorithms such as spiral cleaning, wall-following and random walk angle-changing after bumping into an object or wall. This design is based on MIT researcher and iRobot CTO Rodney Brooks' philosophy that robots should be like insects, equipped with simple control mechanisms tuned to their environments. The result is that although Roombas are effective at cleaning rooms, they take several times as long to do the job as a person would, usually covering some areas many times and others only once or occasionally not at all.