We aren’t sure there’s enough information in the [We Make Machines’] video to easily copy their self-balancing bike project, but if you want to do something similar, you can learn a lot from watching the video. Building sufficient gyros to keep the bike stable required quite a bit of trial and error.
There are some tricks to getting a stable heavy weight to rotate without a lot of vibration and problems. The gyros go on the rider’s saddle, so you aren’t going to be able to ride in the normal fashion. However, a substantial motor drives the wheels so there’s no need to peddle.
The first attempt to self-balance stayed stable for about 10 seconds. Some of it was fine-tuning code, but noise from the gyros also threw off the angle sensor. A higher-quality sensor seemed promising, but it didn’t really fix the problem. Instead of using PID, the guys tried an LQR (Linear Quadratic Regulator) algorithm. Once that was sorted and a servo allowed for steering, it was time to let the bike roam free.
Then disaster struck as the bike lost its cool in a parking lot, causing damage. After repairs, they found issues that confused the angle sensor. They didn’t have the stomach to fit a third sensor onboard, so they put Billy the Crash Dummy onboard and decided to try to run him and the bike off a ramp. That didn’t exactly work out, though. After two attempts, the bike was effectively totaled, although Billy seems to have survived with no more than a bruised ego.
We were dismayed that they didn’t really complete the project, but it does seem like they learned a lot, and maybe that will help someone else out in the future.
We have seen working bikes before. We also have seen some truly strange bike projects.
It seems like they just assumed that turning the bicycle’s handlebar towards the desired direction is the way to steer. It is not, and it’s somewhat ridiculous that they spent so much time engineering and building the wrong method of balancing the bike without stopping to think about how a cyclist balances in real life.
at least they managed to make a trackstanding robot. (and, full fairness, it did trackstanding a lot better than i can.) but it does sort of seem like they were just getting to the really interesting problems around two-wheeled balancing, then gave up. maybe they’d’ve been better served with a set of accelerometers than an angle sensor?
For those interested. When you turn a bike you actually turn the bars the opposite direction initially just a little which throws your weight into the turn, banking you the correct direction. Then you turn jusssst the right amount in the correct direction to kinda catch yourself. Try next time you’re a bike it’s really cool that we do this all subconsciously.
Oh one other fun thing- I read an argument somewhere that the high school physics bicycle wheel angular momentum thing is not really how you “balance” on a bike. The argument goes that you can balance on a bike just fine going super slow. Or during a track stand basically motionless. Or that rollerblade wheels are tiny and you can balance on their fine. Even better an ice skate. Bicycles are super cool no wonder hackers love them.
it’s an error i see a lot of native anglophones making, but for some reason it always grates on me: “peddle” is not the same word as “pedal”, and they shouldn’t be used interchangeably.
I thought maybe they were going for “no need to peddle [on YouTube]”, which obviously didn’t make much logical sense.
shutters
Aren’t bikes pretty much self-balancing already? I’m pretty sure I’ve seen a fair few videos of bikes without riders going just fine after a start.