The Roomba robotic vacuum works by utilizing infrared sensors to calculate distance, detect walls, stairs and other obstacles. It has a piezoelectric sensor that recognizes dirty patches, alerting it to move slowly and clean thoroughly. Some models come with a beacon that lets them know which room to stay in.
The Roomba calculates the size of the room it is to clean by using infrared signals. It does this by transmitting signals and then measuring how long it takes for the signals to return. The Roomba has four infrared sensors on its front bottom. These sensors send out signals constantly, and if they are not returned to the Roomba, this indicates a stair or drop-off, so the Roomba knows to turn around and head in another direction.
On its right-hand side, the Roomba has a wall sensor, an infrared sensor that tells the Roomba to stay in a close path alongside a vertical surface without touching it. However, if the Roomba does bump into an object, its object sensors activate, and it backs up and turns around until it finds a clear path.
The vacuum part of the Roomba includes an agitator that grabs at dirt and a vacuum that sucks it up. The Roomba has no vacuum bags, so the dirt bin needs to be emptied at least once per room.