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Why Are So Many Robot Vacuums Round?

And what does it have to do with Austin Powers?

We’ve all seen robot vacuum cleaners—those self-propelled, oversized hockey pucks that buzz around the house picking up dirt. But why are most of them round? Why not square or rectangular or, as some are, D-shaped?

To get answers, we checked in with Brent Hild, director of product management for iRobot. The Bedford, Massachusetts–based company was founded in 1990 by MIT roboticists, who launched the first home vacuuming robot (called Roomba) in 2002.

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While many competitors—notably Neato, one of the robots that did not ace our tests—claim that their D-shaped robots do a better job getting into corners than a round robot, Hild points out a problem. “The geometry of the form factor makes it difficult to get out of certain environments.”

As a perfect example, he said, watch a clip from the spoof spy movie, “Austin Powers: International Man of Mystery,” where the hero played by Mike Myers tries to go after the villain using a rectangular luggage cart in a narrow hallway.

But first, he has to turn it around.

“The beauty of a round shape is that it makes things easy to navigate,” Hild says. “From a robot perspective, it’s very difficult to navigate [tight spaces and corners], but a round robot can rotate 180 degrees and come out the way it went in.”

Sure enough, in our testing of robot vacuums a D-shaped robot routinely got stuck, pretty much negating any of its vacuuming prowess. We had to rescue it on the regular.

If only Austin Powers’ cart was round, he’d be in business.