This invention relates to an obstacle detection system for an autonomous cleaning robot

generation models have a self-charging homebase they automatically try to find (via its infrared beacons). 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.

Four infrared "cliff sensors" on the bottom of the Roomba's bumper prevent it from falling off ledges such as the top steps of stairways. Most second- and third-generation models have internal acoustic-based dirt sensors that allow them to detect particularly dirty spots (zones having excess particulates) and focus on those areas accordingly.