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It Takes Two Neurons to Ride a Bicycle (2004)

paradise.caltech.edu

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Re: It Takes Two Neurons to Ride a Bicycle (2004)

#21

Post by Safyia »

lucb1e wrote: post #20
chrischen wrote: post #12

I wish math notation becomes substitued with pseudocode. I can never figure out all the greek letters!

But then it wouldn't look as "scientific" (i.e. anyone could understand it, it wouldn't look complicated). At least that's what I feel like, reading and writing a bunch of papers for my master's. We are encouraged to put math stuff in ours just because it looks more theoretical that way. Whenever I do something of worth I also make sure to blog about it so I can write down in normal terms what we did and found, with…

It would be great to have a website where the writers of the paper, or well, anyone who understood it well, would write an article about it in a more accessible way with some examples included etc. I am a big fan of blogs explaining such things.

Re: It Takes Two Neurons to Ride a Bicycle (2004)

#22

Post by lucb1e »

Safyia wrote: post #21
lucb1e wrote: post #20

Earlier quoted context omitted.

But then it wouldn't look as "scientific" (i.e. anyone could understand it, it wouldn't look complicated). At least that's what I feel like, reading and writing a bunch of papers for my master's. We are encouraged to put math stuff in ours just because it looks more theoretical that way. Whenever I do something of worth I also make sure to blog about it so I can write down in normal terms what we did and found, with…

It would be great to have a website where the writers of the paper, or well, anyone who understood it well, would write an article about it in a more accessible way with some examples included etc. I am a big fan of blogs explaining such things.

That's an interesting idea! Might be something indeed.

Re: It Takes Two Neurons to Ride a Bicycle (2004)

#23

Post by andars »

Seden wrote: post #15
hathawsh wrote: post #8

Does a Raspberry Pi have enough computing power to run these two neurons in the real world? Could I attach motors and sensors to a real bike and have it drive itself? That would be amazing.

This is just a PID controller, they have existed and been used in industry much longer than computers and thus require almost no computing power at all. Everyone taking higher level engineering courses learns how to design these because almost everything uses them. Honestly I thought that the paper was a joke on how everything is called neural network, but maybe it is serious... https://en.wikipedia.org/wiki/PID_cont…

It looks more like a cascade of a P controller (theta setpoint to gamma setpoint) with a PD controller (gamma setpoint to torque). But yeah, basically just classical control.

Re: It Takes Two Neurons to Ride a Bicycle (2004)

#24

Post by crispyambulance »

tgb wrote: post #17
Seden wrote: post #15

Earlier quoted context omitted.

This is just a PID controller, they have existed and been used in industry much longer than computers and thus require almost no computing power at all. Everyone taking higher level engineering courses learns how to design these because almost everything uses them. Honestly I thought that the paper was a joke on how everything is called neural network, but maybe it is serious... https://en.wikipedia.org/wiki/PID_cont…

Yeah, that was my thinking: how is this doing anything other than a PID controller? Glancing at the paper it actually looked like a PD controller, but maybe I missed some feed back where it could accumulate an integral term as well.

I guess you can think of it as a "self-tuning" PID controller. It "learns" how to ride a bike.

If it were really "just" a PID, you would need some arbitrarily complex procedure involving a human for tuning all the parameters?

Re: It Takes Two Neurons to Ride a Bicycle (2004)

#25

Post by andars »

crispyambulance wrote: post #24
tgb wrote: post #17

Earlier quoted context omitted.

Yeah, that was my thinking: how is this doing anything other than a PID controller? Glancing at the paper it actually looked like a PD controller, but maybe I missed some feed back where it could accumulate an integral term as well.

I guess you can think of it as a "self-tuning" PID controller. It "learns" how to ride a bike. If it were really "just" a PID, you would need some arbitrarily complex procedure involving a human for tuning all the parameters?

It isn't self-tuning, and it doesn't "learn."

From the paper: "The three constants c_i need to be set by the implementor"

Under "Future Directions": "One obvious thing to do with this system is to have it learn and tune its parameters with experience." The work presented in the paper does not do this.

"This network was designed in an ad-hoc, if traditional, way. First, a human tried to control the bicycle with the simulator. After many attempts, the human finally became a somewhat skilled operator of the bicycle ... the human at this point was able to describe the key parameters which were being attended to, and based on this, the two-neuron network was designed." By "designed," the author means "the three constants were selected."

This sounds like the "arbitrarily complex procedure" you are looking for.

Re: It Takes Two Neurons to Ride a Bicycle (2004)

#26

Post by andars »

lucb1e wrote: post #20
chrischen wrote: post #12

I wish math notation becomes substitued with pseudocode. I can never figure out all the greek letters!

But then it wouldn't look as "scientific" (i.e. anyone could understand it, it wouldn't look complicated). At least that's what I feel like, reading and writing a bunch of papers for my master's. We are encouraged to put math stuff in ours just because it looks more theoretical that way. Whenever I do something of worth I also make sure to blog about it so I can write down in normal terms what we did and found, with…

Would you mind sharing your field of study?

Re: It Takes Two Neurons to Ride a Bicycle (2004)

#28

Post by digikata »

vletal wrote: post #19
digikata wrote: post #13

Nice paper. It makes me wonder how different the two 'neurons' are from a classical control theory set of equations (w/ gains in a feedback loop) solving for the same plant model. I do love the visualization of "Instability of an unsteered bicycle" in figure 2 though.

I have some minor background in control theory. After going trough the paper I had a very same thought thus I googled and found this: http://www.control.lth.se/media/Staff/KarlJohanAstrom/Lectur... After checking out the slides I kind of feel that there might be some oversimplification in the used simulator, like producing _the desired lean angle_ might not be enough. But I am no expert.

I give the authors a little bit of a break because they're sort of more thinking about the meta problem of how to build an automated system to create a controller. From that standpoint, the original paper is more introducing the early landscape of the problem and documenting some early stabs at it. Introducing the question of how to get that automated derivation to arrive a simple set of end controls for the system as simulated.

Re: It Takes Two Neurons to Ride a Bicycle (2004)

#29

Post by Joe-Z »

lucb1e wrote: post #20
chrischen wrote: post #12

I wish math notation becomes substitued with pseudocode. I can never figure out all the greek letters!

But then it wouldn't look as "scientific" (i.e. anyone could understand it, it wouldn't look complicated). At least that's what I feel like, reading and writing a bunch of papers for my master's. We are encouraged to put math stuff in ours just because it looks more theoretical that way. Whenever I do something of worth I also make sure to blog about it so I can write down in normal terms what we did and found, with…

I got the same feeling while I was still in university. I mean if the mathematical notation would at least make it more concise, because there are definitely computations which are easier explained using this notation.

But more often than not I look at papers, where I know what they were doing and how and just have to ask myself: Why would you go through the work of translating what you did back into formulas, which bring exactly zero benefit and are harder to understand than the code you wrote?!

Re: It Takes Two Neurons to Ride a Bicycle (2004)

#30

Post by tnecniv »

iovrthoughtthis wrote: post #16
Seden wrote: post #15

Earlier quoted context omitted.

This is just a PID controller, they have existed and been used in industry much longer than computers and thus require almost no computing power at all. Everyone taking higher level engineering courses learns how to design these because almost everything uses them. Honestly I thought that the paper was a joke on how everything is called neural network, but maybe it is serious... https://en.wikipedia.org/wiki/PID_cont…

I'm with you here. Did no-one else do robotics in CS?

Lot's of schools don't put robotics in CS. They put it in EE or ME. Computer vision is often a CS class, but control theory and other subjects that involve interacting with the physical world are often placed in other departments most CS students avoid.
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