The self-navigation system is what makes a robotic vacuum robotic, and the biggest difference between a $50 model and a $1,500 model is the precision of the navigation sensors. Roomba uses iRobot's AWARE(tm) Robotic Intelligence System to make many decisions for itself, so minimal human input is required. The AWARE system is made up of multiple sensors that pick up environmental data, send it to robot's the microprocessor and alter Roomba's actions accordingly.
According to iRobot, the system can adapt to new input up to 67 times per second.
We'll look at the following parts to learn how Roomba navigates its environment:
Pressing on the bumper activates the object sensors (below).
The first thing Roomba does when you press "Clean" is calculate the room size. iRobot is a bit hazy on how it does this, but HowStuffWorks believes that it sends out an infrared signal and checks how long it takes to bounce back to the infrared receiver located on its bumper. Once it establishes the size of the room, it knows how long it should spend cleaning it.
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While Roomba is cleaning, it avoids steps (or any other kind of drop-off) using four infrared sensors on the front underside of the unit. These cliff sensorsconstantly send out infrared signals, and Roomba expects them to immediately bounce back. If it's approaching a cliff, the signals all of a sudden get lost. This is how Roomba knows to head the other way. When Roomba knocks into something, its bumper retracts, activating mechanicalobject sensors that tell Roomba it has encountered an obstacle. It then performs (and repeats) the sequential actions of backing up, rotating and moving forward until it finds a clear path.
Another infrared sensor, which we'll call a wall sensor, is located on the right side of the bumper and lets Roomba follow very closely along walls and around objects (like furniture) without touching them. This means it can clean pretty close up to these obstacles without bumping into them. It also determines its own cleaning path using what iRobot says is a pre-set algorithm that achieves complete floor coverage.