Delft University of Technology

There's a whole line of study into how a moving bike can stay upright without a rider.

There's a whole new science of how to balance bike-share stations. The idea may sound overly academic, but there's a practical outcome: an empty station means no one can rent, and a full station means no one can drop off. We joked that the ideal solution would be bikes capable of riding themselves to different stations—except that they'd fall over on the way, for lack of (yes) balance.

Well it turns out some bikes are actually quite good at balancing themselves, and that there's a whole science devoted to this area of inquiry, too. Just have a look at the following video, courtesy of Cornell robotics professor Andy Ruina and Arend Schwab of Delft University of Technology. Here, a dinged-up, seatless, mustard-yellow, otherwise unspectacular old bicycle somehow rides itself all the way across a parking lot—no human required:

And here's the mustard miracle again, this time recovering from a pretty sharp swerve on its own:

"The amazing thing about bicycles is that they can balance themselves," says Ruina in a separate explainer. "That somehow a bicycle, if it's moving fast enough and not too fast, will steer itself and balance."

The question Ruina and colleagues have tried to answer is: How, exactly? Turns out people have been studying this problem for years. In a TEDx talk from 2012, Schwab says entire book chapters on the physics behind the self-stability of bicycles appear as far back as 1910. Two main mechanisms were thought to be at play: a "gyroscopic" effect, and a "trail" effect.

Those terms should be familiar enough to any average reader with an advanced degree in physics or engineering, but we'll explain a bit more anyway. The gyro effect essentially says that since the front wheel is spinning (like a gyroscope), it creates torque that helps the wheel center itself even when the bike tips to one side. The trail (or "caster") effect says that since a bike's front wheel is positioned behind the steering axis, the wheel will follow the steering motion and self-align—a little like how a shopping cart wheel should function, in the rare instance it's not broken.

But Ruina and company weren't convinced those effects explained everything that was going on with the likes of their yellow wonder. So they built a funny-looking bike prototype that canceled out the gyro effect and had no trail effect. And sure enough, in several test trials, it performed very well—almost managing to escape from overprotective research assistants:

The researchers wrote up their findings and published them in Science in 2011. Here's Ruina talking to Popular Mechanics around that time about what he hopes the work will mean for bikes of the future:

People have been stuck in their ways about what bicycles look like and how they can work. We'd like to think that using our ideas, people might make better bicycles, and this certainly opens up the possibilities.

Count Ruina among those thinking outside the box when it comes to bike design. He's developed a "bricycle" (a bicycle-tricycle hybrid with three large back wheels) and tells CityLab he hopes to unveil an "unusually robust robotic bicycle" in the coming months. So we're nowhere near the point of seeing bicycles redistribute themselves equitably across a city. But perhaps heading, a little wobbly, in that general direction.

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