
It Takes Two Neurons to Ride a Bicycle (2004) [pdf] - DoreenMichele
http://paradise.caltech.edu/%7Ecook/papers/TwoNeurons.pdf
======
floatingatoll
NIPS 2004 Demonstrations:

[https://web.archive.org/web/20041204162656/http://www.nips.c...](https://web.archive.org/web/20041204162656/http://www.nips.cc/Conferences/2004/Demonstrations/Demonstrations.php)

Virtual Bicycle — Matthew Cook, California Institute of Technology:

[http://www.paradise.caltech.edu/cook/papers/index.html](http://www.paradise.caltech.edu/cook/papers/index.html)

 _In this work I created an environment in which I assumed learning of higher
order concepts would be necessary. I created a general purpose physics-based
hinged rigid body simulator and used it to simulate a bicycle for a learning
agent to learn to ride. But as others have found in other contexts, most
environments do not require higher order concepts, and in this case it turned
out that a simple two neuron circuit was already sufficient for controlling
the bicycle, indeed, better than a human using the keyboard.

The physics simulator was a significant project in itself: I studied rigid
body mechanics (which is more complex than most of us realize) and designed
the simulator explicitly so as to simultaneously exactly preserve both angular
momentum and kinetic energy, as previous simulations of mine (in quantum
mechanics!) had shown me that preserving conserved quantities can be crucial
for getting accurate results. The simulator works nicely, and I later read in
Sam Buss's 2001 paper, Accurate and Efficient Simulation of Rigid Body
Rotations, that my precautions were well warranted.

Later I was able to reduce the controller to just one neuron, and then to an
even simpler plain linear feedback system, confirming the finding that many
real problems are best solved by a hack. The simulator has been useful in
other projects since then._

Virtual Bicycle Download Page:

[http://www.dna.caltech.edu/~cook/](http://www.dna.caltech.edu/~cook/)

~~~
dang
Thanks! We changed the URL from
[https://www.reddit.com/r/dataisbeautiful/comments/7s8hck/pat...](https://www.reddit.com/r/dataisbeautiful/comments/7s8hck/paths_of_800_unmanned_bicycles_being_pushed_until/).

A discussion from last year:
[https://news.ycombinator.com/item?id=16215130](https://news.ycombinator.com/item?id=16215130)

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boxcardavin
"How would you ensure having the exact same starting conditions each time?" is
the best question in that thread, and this was the biggest challenge for us in
training our bikes to balance using a NN. Bikes are hard because they're a
non-holonomic system, it isn't just a matter of finding linearized equations
of motion.

~~~
Jedi72
Can you provide additional references around this term "non-holonomic"

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tomglynch
Title gore... What this really is, is a Simulated path of an unmanned bicycle
with a rolling start.

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hammock
Is this a fractal?

~~~
Zenst
No, as no repeating patterns zooming in.

Does it have symmetry, yes.

However, this is a simulation and with that the constraints and randomness of
the variables will over many runs, highlight if there are any aspects that are
overlooked.

Looking at this run, level of wobble seems to be overly bearing with
noticeable patterns that for me would question the model.

That and as a kid, we had a grass hill of about 500m in length and a mild
graduand and fairly flat that you could ride a bike upon. I would go down it,
side straddle my bike, step off and see how far I could run alongside my bike
and get back on. Yes there was accidents, but I was a kid, nothing beyond a
bruise doing this. I would say being conservative, I easily managed 25 meters.
Now this was on a hill, more momentum to start with and the big factor, on
grass.

Yet I look at the model runs and see very little running straight down. I
would factor in the model has a fixed initial momentum, and a random
increasing wobble. This would play out with the pattern being seen.

What's needed now is for this to be done 800 times for real. Even with a
static push, factors would come into play. Such as dust build up, temperature
changes, humidity can all have a small factor in the outcome.

Which highlights a big area with simulation and real runs comparisons.
Simulations will all those nuances chaos factors as static and as if all runs
happen at the same point in time. That's hard to repeat for real for
comparison. Which makes it hard in nailing all those small areas that make
small, but noticeable effects over time.

With that, is the problem a fractal? In that the more you look into all
factors that affect it, you end up zooming into a whole new area of factors
that affect that factor.

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pault
Clicking on this link on Firefox iOS I see:

A dickbar at the top telling me to open it in the app.

A small section in the middle of the screen with a 50% black overlay that
allows me to see about a quarter of the content with no ability to scroll or
close the overlay.

A double wide dickbar on the bottom asking me if I want to open the page in
the app or Safari (I use Firefox). I cannot make this go away so I can see the
page.

Fuck Reddit.

~~~
caymanjim
Reddit is completely unusable on mobile without the app. I get that they want
ad revenue, and if they were less ham-handed about it (and if their app was
significantly less shitty, and with more subtle ads), I might have installed
it.

I'll keep using Reddit from a desktop browser, but I won't install the app. So
now they get no revenue from me, when they had the chance to get some.

~~~
0db532a0
Your demographic has no bearing on Reddit’s bottom line.

~~~
pault
The demographic of people that want to view the site on a phone?

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sliken
Note sure why this one year old post is particularly relevant today. It at
least needs a (2018) in the title.

~~~
kgwxd
Not sure what age has to do with facts. It happened, nothing is going to
change that.

~~~
sliken
Hacker news is to collect news, not facts, right?

Should I submit the periodic table? Every scientific paper ever posted?

It would waste less time if random posts from a year or older appended the
year to the title. Seems very common, but not mentioned in the hacker news
guidelines.

~~~
kgwxd
If I haven't seen it, it's new(s) to me!

