When artificial intelligence was all the rage in the 1980s, researchers joked that by the turn of the century, smart vacuum cleaners built in Japan would be cleaning smart tanks built in the United States. As it turns out, though, a few years into the new century the vacuum bot that is grinding across the floors of gadget freaks around the nation is American-designed. Produced by iRobot, a Massachusetts company that also makes pack robots for the Defense Department, this not-very-smart but persistent floor cleaner, looking a bit like a hugely pregnant Frisbee, scoops up dust, wood chips, cat hair and other lightweight trash for anyone with no patience for housework and $200 to spare. The Roomba bounces delicately off walls and furniture in a crazy-quilt pattern designed to cover every inch of a room at least once during an hour-long cleaning cycle. Mine scares me a little and fascinates our domestic carnivores.

To at least one budding appliance hacker, however, this useful little household robot has proved irresistible—if tricky to control. Hobbyists and researchers spend hundreds of hours and thousands of dollars developing mobile robots that can reliably cross a room carrying a load of sensors and computing gear. In the Roomba, computer-security consultant Jake Luck saw a nearly perfect prebuilt robotic platform, one with multiple sensors already built in. Sure, it also carried a floor brush, but that ought to be easy enough to fix.

Luck had never taken apart a vacuum cleaner before he and John Ioannidis (a network and mobile gizmo guru at AT&T Labs) took the Roomba into the lab. Under the hood they found a remarkably simple, robust design, with no extraneous mechanical parts. For example, on the spring-loaded bumper that tells the Roomba that it just ran into something, plastic tabs do a job usually performed by finicky microswitches. When the bumper recoils, one of the tabs gets shoved into the path between a matching LED and a phototransistor. With two tabs, the CPU can figure out which part of the bumper hit an obstruction. Other banks of light emitters and detectors tell the robot whether it’s heading over the edge of a flight of stairs and how closely it’s following a wall. (The bot also comes with a “virtual wall”—a small box that emits an infrared beam to fence the Roomba in; sensors on the Roomba activate software that prevents it from crossing the infrared line on the floor.)

When Luck and Ioannidis put their pioneering disassembly guide on the Web, they received a congratulatory e-mail from the Roomba’s designers, but they have not detected a national groundswell in Roomba hacking. Luck guesses this may be because the $200 vacuum cleaner is good at a job that hackers aren’t interested in doing themselves—housework—why mess with it?

“That’s the ultimate compliment,” says former iRobot engineer Phil Mass, laughing: “To not want to hack it because it does its job so well.” Mass has good reason to feel satisfied: He spent the better part of three years writing and polishing the thousands of lines of code that give the Roomba its hardworking personality.
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