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It Takes Two Neurons to Ride a Bicycle (2004)
- XnoiVeX 9y agoAbout the most fascinating thing I read all week.
- hprotagonist 9y ago(2004)
- skykooler 9y agoUnfortunately, the videos linked in the paper seem to have disappeared. Are these mirrored anywhere?
- burkaman 9y agoThey work, but the tilde character in the pdf is wrong. Try this: http://www.paradise.caltech.edu/~cook/Warehouse/RecursiveBike.avi http://www.paradise.caltech.edu/~cook/Warehouse/RecursiveBik...
- sctb 9y agoThanks! A moderator updated the title.
- amerine 9y agoThis is a really easy read if folks are looking for easy-to-digest papers! From the results: > Although the two-neuron network controller works well for a range of speeds, one thing the controller does not do is to try to dampen the instabilities that can arise when riding too slowly or in too sharp of a turn. (This would probably require a third neuron that is dedicated to this task.)
- grondilu 9y agoI've only flown through the paper, but one question : why is it so hard for humans to learn how to ride a bicycle? I mean I do remember it to be pretty challenging.
- hathawsh 9y agoDoes 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.
- AstralStorm 9y agoIf by drive you mean not fall over, yes. If you mean actual routing, avoiding collisions and reacting to unexpected situations, very much no.
- IshKebab 9y agoYes of course. But if your goal is to make a robot bike there are better algorithms than this one.
- Seden 9y agoThis 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_controller#History https://en.wikipedia.org/wiki/PID_controller#History
- iovrthoughtthis 9y agoI'm with you here. Did no-one else do robotics in CS?
- chrischen 9y agoI wish math notation becomes substitued with pseudocode. I can never figure out all the greek letters!
- lucb1e 9y agoBut 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 code, (online) demo, and anything else that might be useful.
- Safyia 9y agoIt 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.
- andars 9y agoWould you mind sharing your field of study?
- lucb1e 9y agoSecurity, software and network engineering. (Previous study was software and security, this one is security and network; and I've always liked to play with tech in those three subfields.)
- digikata 9y agoNice 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.
- vletal 9y agoI 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/Lectures/BikeTalkKTH2006.pdf 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.
- digikata 9y agoI 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.
- snek 9y agodoes anyone recognize what software was used during this study
- plg 9y agocode?
- pje 9y agoThis is now my favorite scientific paper headline, beating out the previous champion, "How Many Birds Are There?" https://link.springer.com/article/10.1023/A:1018341530497 https://link.springer.com/article/10.1023/A:1018341530497
- Zanta 9y agoOn the subject of birds, "Great tits also have age-related defects" https://www.sciencedaily.com/releases/2011/03/110307130215.htm https://www.sciencedaily.com/releases/2011/03/110307130215.h...
- tajen 9y agoIn that case, if you lay outdoors with your mouth open, how long does it take until a bird ... in it? Depending on the worldwide bird density and the relative size of the mouth: https://what-if.xkcd.com/11/ https://what-if.xkcd.com/11/
- rafi_kamal 9y agoDo you have a freely accessible copy of this paper?
- deleted 9y ago[deleted]
- perl4ever 9y agoIs this basically just taking a Fermi type estimation and making a paper out of it? I was just thinking that I like doing those sorts of calculations, and given that so many people on the Internet profess to hate them, there should be an exploitable niche somewhere.
- dahart 9y ago> There is not a direct or fixed correspondence, but as a general rule, during stable riding, a higher clockwise torque on the handlebars will cause the bicycle to start leaning more to the left It's counter-steering! I was glad to read that counter-steering is accounted for and works in their physics simulation like it does in the real world. I don't have a source handy, but I believe that there is a fixed correspondence between steering angle and the resulting turn that depends on the bike's speed, lean & steer. (And maybe tire radius counts too.) A bike riding in a stable constant clockwise turn will have a slight right lean & clockwise steer in steady-state. Steering clockwise from there will turn the bike left, or increase the turning radius until it's straight and then start turning counter-clockwise. Steering counter-clockwise from steady state clockwise turn will turn turn the bike right, increase the lean and decrease the turning radius.
- aidenn0 9y agoThe fixed correspondence between leaning and turning is easy to derive on your own: Draw a picture of a leaning bike from behind. Add a horizontal line for the ground. Assume the entire bike/human system is leaning an equal amount, so put the center-of-mass somewhere in the leaning line. If the bicycle is maintaining a constant amount of lean, then the extended line of the force applied by the ground to the bike must pass through the center of mass (i.e. in this case the angle of the force vector is the same as the angle of lean). Now decompose the force vector into vertical and horizontal components. The vertical portion when riding on the ground (i.e. not jumping the bike), neglecting aerodynamic effects, is fixed to be the gravitational force, so it will be constant regardless of the direction of lean. This means that the horizontal portion of the force will be equal to the the gravitational force times the tangent of the lean-angle. This also means that when the tangent of the lean-angle exceeds the coefficient of friction between the tires and pavement, you will crash. The turn-radius can then be calculated by treating the horizontal force as the centripetal acceleration, and is indeed related to speed (faster speeds mean a larger turn radius).
- dahart 9y agoYeah, that's a useful breakdown, thank you! Does this help to explain the fixed correspondence between steer and direction of turn? (For example, to someone who doesn't believe counter-steering is a thing.) The physics of the lean seems easier to decompose than the physics of counter-steering. I am interested in finding a way to describe counter-steering so that it's obvious, similar to the way you described the horizontal force vs coefficient of friction.
- GoToRO 9y agoThere are no secrets to riding a bike: 1. Do no try to go straight. Move the handlebars violently left and right when you feel you are falling left or right. 2. Going slow is hard. Go fast. The wheels spinning will behave as stabilizers, making it easier to stay on the bike. 3. Moving your body will make you fall at first if you do not counteract by moving the handlebar. Start by going downhill, without pedaling.
- kevin_thibedeau 9y ago> The wheels spinning will behave as stabilizers, making it easier to stay on the bike. Bicycle wheels do not have enough mass to impact handling through gyroscopic inertia. They do not act as stabilizers. Motorcycle wheels do, and consequently they require more effort to lean at higher speeds as well as require additional lean when accelerating into a curve.
- GoToRO 9y agohttps://youtu.be/8H98BgRzpOM?t=27s https://youtu.be/8H98BgRzpOM?t=27s
- boxcardavin 9y agoGyroscopic forces are not the dominant force keep a bicycle upright, this has been demonstrated with bicycles with counter-rotating wheels. Steering geometry of the front wheel is what self-stabilizes a bicycle.
- GoToRO 9y agoIt's not just one thing. At different speeds there are different things that help you stay balanced. At low speeds, yes, what you do with the handlebar and so the front wheel is predominant. At higher speeds gyroscopic forces do not actively keep you upright, but they help by slowing down the speed with which you loose you balance and so you have more time to react (by steering).
- 9y ago
- viach 9y agoLooking at the roads it seem like driving cars is taking no neurons at all.
- dreamcompiler 9y agoThis sounds a whole lot like a Braitenburg vehicle [1] and I was surprised the author did not cite and compare/contrast Braitenburg's work. [1] https://en.m.wikipedia.org/wiki/Braitenberg_vehicle https://en.m.wikipedia.org/wiki/Braitenberg_vehicle
- erikig 9y agoI loved that diagram titled "Instability of an unsteered bicycle"