[HN Gopher] CARA - High precision robot dog using rope
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CARA - High precision robot dog using rope
https://www.youtube.com/watch?v=8s9TjRz01fo
Author : hakonjdjohnsen
Score : 984 points
Date : 2025-07-23 17:38 UTC (1 days ago)
(HTM) web link (www.aaedmusa.com)
(TXT) w3m dump (www.aaedmusa.com)
| hakonjdjohnsen wrote:
| See also the youtube video about the project:
| https://youtu.be/8s9TjRz01fo
| PaulDavisThe1st wrote:
| The linked page has that video embedded.
| hakonjdjohnsen wrote:
| Yeah good point!
|
| When I came across this amazing project and wanted to share
| it to HN, I was debating whether to post the youtube link or
| the project page. I decided to post the project page and
| mention the youtube link in the description for those who
| prefer video, but somehow that description got posted as a
| comment instead (not sure how that happened?). Anyway as you
| said the video is embedded in the project page so it wasn't
| really necessary
| btbuildem wrote:
| I've watched and re-watched Aaed's videos on the capstan drive,
| it's great stuff. High speed, high torque, compliance,
| effectively no backlash. It's fascinating to watch a legit
| engineering mind at work.
| DeepSeaTortoise wrote:
| He's easily one of my favorite content creators. Ofc, there are
| much better engineers, domain experts or more entertaining
| people on youtube, but he strikes a very enjoyable balance.
|
| I wanted to start writing a list of other tech related, pop-sci
| and industrial-design Youtubers I kinda enjoy, but noticed just
| how many channels I'm subscribed to... If there's any interest,
| I'll drop it, just tell me. Meanwhile I have some filtering and
| sorting to do.
| noman-land wrote:
| I am interested. I love these builder channels.
| patatman wrote:
| I'm interested as well! I never can get enough of these
| builders and engineers.
| DeepSeaTortoise wrote:
| Hey, I'll reply later to noman-land's comment below, but
| progress is kinda slow. It takes more time than expected to
| categorize this many channels and I stopped yesterday after
| having sorted a bit over 500 and have barely reached the
| letter "H" (most not tech related ofc, so no worries about
| getting a monstrous list).
|
| I got a bit more time today, so maybe today evening (German
| time), elsewise I'll have to skip Friday, so likely
| Saturday afternoon.
| Lerc wrote:
| I recently found his videos also. It's one of those things that
| gets my mind bubbling with ideas for things I want to make,
| never enough time to do them all though (and this breadboard
| beside me is asking for attention)
|
| It does make me wonder about the algorithm, Quite a lot of
| things I find on Youtube turn up on HN a week or two later. I'm
| not sure if this is an indicator of the effectiveness or
| failure of the algorithm. It is definitely succeeding in
| finding videos popular with some people and showing it to more
| who might share that interest. The question is, are the things
| I (and consequently many others of similar interests) see the
| best of all there is, or a subset of the excellent videos out
| there that happen to get noticed.
|
| I sometimes find channels that are years old with a goldmine of
| good information. That suggests that there is more good stuff
| out there than what I see. Were they just unlucky that I didn't
| see them before? Am I lucky to be seeing them now? It also
| might be that it is not luck but the algorithm has arbitrarily
| decided that the video has some special factor that requires
| promotion or that I have passed some arbitrary threshold of
| perceived character development that makes me supposedly now
| interested in such things.
| godelski wrote:
| > It does make me wonder about the algorithm
|
| IIRC he uses a pretty simple algorithm. I remember him
| discussing the gating mechanism and how he had it follow a
| cycloid. I think there's a lot of opportunities for others to
| optimize the algorithms and he is focused on the physical
| engineering side. I'd love to see him collaborating with
| someone who does more reinforcement leaning. I also think
| it's very impressive what he achieves with such simplified
| algorithms.
|
| If I'm misremembering or missed something please correct me.
| I'm out now but I'll try to find the video of him talking
| about gating when I'm back if someone hasn't already linked
| it.
|
| Also, I love how YouTube has all these "small" creators doing
| extremely impressive stuff. It's a real shame the algorithms
| make discovery challenging. The beauty of something like
| YouTube is not about just getting something to watch, it's by
| being able to get access to any content. Search is always a
| difficult problem to solve but I'm afraid it's currently over
| optimizing for views rather than intent. Which, to be fair,
| is much harder to measure. But I say over optimized because
| frequently I can search the title with 90% accuracy and fail
| to find the video. Something minor like missing an "s" or
| something effectively non meaningful. It's extremely
| frustrating...
| 8note wrote:
| the algorithm in question is youtube's for how its getting
| to all the HN users at about the same time. i was also
| suggested this same video a few days back
| godelski wrote:
| My post discussed two algorithms: the gating algo for
| CARA[0] and the search algorithm for YouTube.
|
| If I'm reading your comment accurately, you're mentioning
| the discovery algorithm, which is neither of these. I
| also got the video, but I was already subscribed (it was
| suggested to me when it was released). Yes, the discovery
| algorithm has some of these issues but I'm more
| understanding of that because it's a much harder problem.
|
| Both have self inflicted problems and I think they can be
| more easily addressed:
|
| Discovery over optimizes to recent views and can get
| stuck in certain genres[1]. There is also a strong
| preference to things average user enjoys which doesn't
| work well for those of us who are only slightly less
| schizophrenic than the algorithm itself. Too much
| exploitation, not enough exploration (I wish this was a
| setting I could adjust. My mood changes, how can I let
| the algorithm know?)
|
| Search has two critical self inflicted problems.
|
| 1) after about 5 results it will suggest completely
| unrelated videos (looks like it hands off to the
| discovery feed). Sometimes I need page two... just
| fucking show me more...
|
| 2) the problem I mentioned previously, where it distrusts
| you prioritizing popular videos over a trivial spelling
| or grammatical error. Google search has this exact same
| problem.
|
| [0] my dumbass didn't check which video was linked. It's
| this one where he discusses it. At 12:30 in the video
|
| [1] this leads me to having tons of YouTube tabs open as
| I'm unsure if a video I'm interested in but don't have
| the current bandwidth for is never going to be shown to
| me again
| barbecue_sauce wrote:
| The quote in your intial reply ("It does make me wonder
| about the algorithm") was referring to the YouTube
| algorithm.
| godelski wrote:
| The comment you responded to clarified that there are two
| YouTube algorithms (in reality there are many, but was
| distinguishing the categories). I was talking about
| search while the response was talking about discovery
| (like what you see when you open YouTube. The automatic
| suggestions)
| imtringued wrote:
| I get absurdly niche videos with 33 views in my feed about
| robotics but most of them have views in the low thousands.
| The algorithm isn't holding you back.
| mrheosuper wrote:
| i noticed recently YT has been suggesting micro-small
| channel(<1000 subscriber) to me, not sure if this is good
| thing.
| throwaway2037 wrote:
| The real question: Are the recent recommendations better
| than previously? Example: If the recommendation engine
| (presumably driven by some kind of AI/LLM at this point)
| better understands the content of videos, it can make
| better recommendations. If anything, it seems logical
| that smaller channels would begin to appear on your
| YouTube feed, as long as the content is highly quality
| and matches your interests.
| mrheosuper wrote:
| It's both good and bad: Sometime it suggest some small
| channels about some niche topics that i found very
| interesting.
|
| But i don't like how aggressive it is with suggestion. If
| i search some random topic, my newsfeed will be flooded
| with all videos about that topic many days later. So
| sometime i have to use different profile just to not
| "contaminate" the algorithm.
| adolph wrote:
| I haven't watched the one about the dog, but the one with the
| initial explication of capstan drives [0] was excellent. I've
| been dreaming about it for the last year, especially since
| about the same time another person started working with the da
| Vinci robot actuators which use cables to generate find motion.
|
| 0. High Precision Speed Reducer Using Rope:
| https://www.youtube.com/watch?v=MwIBTbumd1Q
|
| 1. Building a DIY Surgical Robot
| https://www.youtube.com/watch?v=d_8rHKrwr-Q
| ACCount36 wrote:
| The "DIY Surgical Robot" vid is so good. And it's also posted
| over a year ago with no follow-up. Damn.
| Keyframe wrote:
| "back in the day", we used capstans to drive film (movie) rolls
| around the scanning aparatus. Both high speed and precise
| without backlash. Great stuff. Somehow I always thought maybe
| lack of high torque is the issue more people aren't using them
| or wear and tear.. but, apparently not?
| mlhpdx wrote:
| Dynema makes a huge difference, a true game changer in many
| ways. I came across it rigging sailboats where is started out
| replacing ropes and now replaces steel cables as well.
| Spectra is another brand with different, equally amazing
| properties.
| darksaints wrote:
| Spectra and Dyneema are both UHMWPE. They're different
| brand names (from Honeywell and DSM respectively) but
| chemically and mechanically the same, possibly with some
| small and insignificant differences due to manufacturing
| processes.
| mlhpdx wrote:
| That's an answer straight from an LLM methinks and not
| reflective of actual experience. Read up on real world
| tests for the practical differences. They are very
| similar but far from "the same".
| Keyframe wrote:
| Interesting you've mentioned sailboats. I've encountered
| dyneema for the first time in spearfishing!
| dyauspitr wrote:
| How is there no backlash? I can't imagine a rope drive without
| backlash.
| Animats wrote:
| Improved materials. Kevlar and Dyneema.[1] Dyneema is about
| 15x stronger than steel per unit weight. Kevlar toothed belts
| have been available for many years, and can be used for many
| of the same applications as this capstan setup. Neither
| material has much elasticity.
|
| The advantage over gears is that overloads are distributed
| over much more material. You don't snap gear teeth. This is
| good for leg landing shocks.
|
| [1] https://www.impact-fibers.com/info/unveiling-the-
| strength-ke...
| kragen wrote:
| The relevant feature of Dyneema is specifically that its
| Young's modulus is much higher than most other organic
| fibers, about half that of steel, which is probably what
| you mean by "neither material has much elasticity".
|
| Steel cables would work just as well if weight isn't a
| consideration, but I think Dyneema is likely to be more
| resistant to abrasion. However, heat produced by any
| significant dynamic friction will ruin it immediately, as I
| found to my sorrow. Kevlar is much more heat-resistant, and
| of course steel is more heat-resistant than Kevlar.
| regularfry wrote:
| Dyneema is much easier to work with, too.
|
| I'm quite fond of bowstring as a material for this sort
| of thing. It usually has other fibres mixed in with it so
| it's a little more bouncy than raw dyneema but that's
| minimised if you get thread that's intended for
| crossbows. It's usually waxed so there's some friction to
| it when you're manipulating it, and it's also easy to
| source.
| darksaints wrote:
| He actually used steel cables for his initial prototypes,
| but steel cables have a problem with rolling fatigue that
| actually gets worse the larger the diameter...so if a
| tiny steel cable is not strong enough, you might actually
| have to change the gear dimensions (and therefore ratios)
| in order to not fatigue them.
| Animats wrote:
| Right. Steel cables have to be oiled internally if flexed
| frequently. This was a major cause of cable failure in
| gym exercise machines for decades. Newer exercise
| machines tend to use synthetic flat straps over pulleys.
| scotty79 wrote:
| It's very non-stretchy rope material. I imagine with enough
| force you can bend it away from the set position a little bit
| but it comes back when you remove the force. Nothing like
| traditional backlash with gears where you can move it with
| very little force between two adjacent gear teeth.
| monuszero wrote:
| So, Aaed was our intern last summer - and he's the real deal. I
| got to work with him on some really cool bespoke robotic end-
| effectors and the guy has great design instincts. Picked up
| mechatronics skills like a sponge, grokked hamming codes in
| like 30sec from a whiteboard doodle. Super hard worker too, he
| would stay late in the electronics lab to work on the motor
| design for what turned out to be CARA - we had fun testing the
| backlash one evening and ever since I've been trying to
| shoehorn one of those actuators into a project.
|
| Potential and active founders here should consider reaching out
| (i think a startup setting would suit him better than corporate
| research), though he's obviously got his own stuff going on and
| a degree to finish!
| foobarian wrote:
| These drives sound amazing, so why are they not used
| everywhere? What are the disadvantages?
| A4ET8a8uTh0_v2 wrote:
| There is a weird mixture of hope and dread in me as I watch this.
| I am ridiculously excited over a person like me being able to
| mess around with something that, until recently, was gated
| behind, well, a lot of hard problems to overcome ( I am only now
| slowly getting through old Peter Scott's robotics to get some
| perspective ). By comparison, it should be so much easier to
| explore aspects of robotics that may go beyond strict math and
| engineering.
| bmau5 wrote:
| Why dread?
| kragen wrote:
| Land mines have been killing people by surprise for decades.
| Flying drones, some of them dropping land mines and others
| lying in wait for incoming convoys, produced 70% of the
| casualties on both sides in the Ukrainian invasion last year,
| and a few weeks ago the Ukrainians shipped some drones to
| near a Russian airport several thousand kilometers from
| Ukraine to blow up a bunch of airplanes. This betokens a
| future of borderless warfare in which probably most of your
| family members will be killed over the next few decades, by
| one or another type of semi-autonomous or fully autonomous
| weapon.
|
| CARA is a super cool project which is never going to kill
| anybody, but it's another piece of evidence that the cost of
| the technology for such weapons has decreased enormously.
|
| That said, talking about the dread is going to get boring
| fast, because nearly every story on the HN front page is
| catapulting us toward that future.
| A4ET8a8uTh0_v2 wrote:
| Good point. If we do press panic button each time, the word
| will lose its meaning. Naturally, it does not help that
| this particular community did happen to catapult us towards
| the future a fair bit over the past years.
| scotty79 wrote:
| I'm more optimistic. I think filling battlefields with
| autonomous weapons will make humans obsolete there and
| reduce war causalities. Basically any attack on humans is
| going to be a war crime and terrorism akin to attacks on
| civilians russia is doing right now
| lazide wrote:
| That is a really weird take considering how hard Russia
| (and Ukraine) work to continue to kill humans in the same
| situation you are describing.
| kragen wrote:
| Who cares if it's weird? Why are you saying "weird" as if
| that were a bad thing? It's just a derogatory synonym for
| "unusual". A take would _have_ to be weird to be a
| contribution to the conversation, because if it 's _not_
| weird, it 's a widely held opinion we all already know,
| and nobody gains anything by reading it.
|
| What matters, given that it meets the minimal bar of
| weirdness to be _potentially_ worthwhile, is whether it
| 's _correct_. Which depends on what _future_ combatants
| will do once weaponry actually _is_ autonomous, not what
| Ukraine and Russia are doing with remotely-piloted FPV
| drones.
| numpad0 wrote:
| I'd call it delusional than weird. US is clearly
| controlling Ukrainian churn rate so that Russian military
| and Ukraine as nation burn down at the same rate into
| disappearance so that the postwar Ukraine can be rebuilt
| with more Western leaning meatbags from surrounding
| nations. And some of people here are framing exactly that
| as utopian bloodless fights of machines. Calling it
| _weird_ is itself almost weird.
| scotty79 wrote:
| I think we are in transition period and nations are just
| learning that sending people to contact line is a
| terrible idea. People never learned things like that very
| fast. It often takes a generation.
| kragen wrote:
| Well, suppose you have two countries at war, say, Burnia
| and Hevonia. They each produce a million autonomous
| weapons.
|
| Burnia sends their million autonomous weapons to kill the
| million people they judge are most crucial to Hevonia's
| war effort, prioritizing Hevonia's political leadership
| and military officers.
|
| Hevonia, meanwhile, sends their million autonomous
| weapons to destroy Burnia's autonomous weapons, when they
| can find them, but not to attack any humans.
|
| Who wins the war?
|
| I think Burnia does, because even if Hevonia's weapons
| are 99% effective, Hevonia's government has still lost
| its top ten thousand people, including all of their
| military officers, while Burnia has only lost half a
| billion dollars. That's going to make it impossible for
| Hevonia to keep fighting. And I think 50% effective is
| more likely.
| scotty79 wrote:
| It's the same question as when one opponent is ready to
| nuke enemy cities while the other is not. In theory
| everything turns out the same way you postulate. In
| practice cost of winning the war in this manner might be
| higher then the cost of losing localized, limited
| conflict.
| imtringued wrote:
| > This betokens a future of borderless warfare in which
| probably most of your family members will be killed over
| the next few decades, by one or another type of semi-
| autonomous or fully autonomous weapon.
|
| You're talking about a whole bunch of targeted and
| intentional attacks in a literal warzone, the most lawless
| kind of place on the planet and you're complaining that
| they are hitting their intended military targets?
|
| Meanwhile Gaza is boring to you, because Israel uses
| conventional bombs with humans in the loop, even though the
| collateral damage matches your prediction today.
| kragen wrote:
| I'm not _complaining_ , exactly; I'd rather the
| Ukrainians be blowing up Russian planes, which were
| thousands of kilometers from the literal warzone, than
| the Russians blowing up Ukrainian planes thousands of
| kilometers away.
|
| I'm saying that the events we're seeing in the Ukrainian
| war _are convincing evidence that the nature of war has
| changed_ , and the implications of that change for human
| society are disquieting.
|
| For two million years, people have often resolved
| conflicts by warfare. But that warfare, though it has
| never ended completely, has always been localized, which
| meant that _most_ places _most_ of the time were
| peaceful.
|
| This is the foundation of the system of international
| relations in which different states exercised monopolies
| of legitimate violence over geographical territories: by
| so doing, they could prevent warfare and provide
| security. This system has existed to one extent or
| another for thousands of years.
|
| Warfare is no longer localized, so now the only place for
| _anywhere_ to be peaceful will be for _everywhere_ to be
| peaceful. It is no longer possible for states to provide
| security to the people within their borders. Consequently
| statehood itself has lost its meaning. The last time we
| saw such a change in the nature of warfare was twelve
| thousand years ago when the first states arose.
|
| I have some corrections for you about other things that
| you did not understand either about my comment or about
| the wars we are commenting on.
|
| It bears repeating that the planes blown up in Operation
| Spiderweb were not in a literal warzone, nor anywhere
| close to a literal warzone. Some of them were thousands
| of kilometers from the literal warzone, in a part of
| Russia that has China and Mongolia between it and
| Ukraine.
|
| The Ukrainians reportedly did have humans in the loop for
| that attack in particular, and both the Ukrainians and
| the Russians are mostly using FPV drones rather than
| autonomous drones of any sort at this point, unless we
| count landmines as "autonomous drones". In
| https://www.youtube.com/watch?v=RmfNUM2CbbM Russian drone
| developer Sergey Tovkach specifically says that Starlink
| is the reason Ukrainian sea drones have established
| control of the Black Sea -- Russia could build sea drones
| but does not have an equivalent to Starlink, so evidently
| both Ukraine and Russia are dependent on remote piloting
| for their sea drones. He also says Starlink's latency is
| too high for piloting quadcopters. (Evidently Operation
| Spiderweb used the Russian cellphone network.)
|
| The Israeli attacks are _also_ using precision-guided
| weaponry and (in some sense) AI, not conventional bombs,
| and they 're killing lots of innocent people, but you're
| right that it's less worrisome to me, for three reasons:
|
| - The total number of people they're killing is about an
| order of magnitude smaller, about 80,000 so far (out of a
| total of 2.1 million Gazans), versus roughly a million in
| the invasion of Ukraine. Many more _civilians_ have been
| killed in Gaza, but both Russia and Ukraine practice
| conscription, so it 's not as if the soldiers being
| killed are only or even mostly volunteers; they were
| civilians until being, in many cases, conscripted.
|
| - The weapons Israel are using are mostly very expensive,
| which limits the number of people they can afford to kill
| with them. By contrast, the drones being mass-produced in
| both Ukraine and Russia cost only a few hundred dollars
| each, and each country is expected to produce about 3
| million of them this year.
|
| - The people Israel are killing are almost entirely in
| close geographical proximity to Israel. Gaza City is 80
| km from Jerusalem. Beirut, the residence of many of the
| Hizbullah personnel that Israel killed with explosive
| charges in pagers (along with, in several cases, their
| children), is 230 km from Jerusalem.
|
| Therefore, while Israel's war is clearly causing terrible
| suffering to millions of innocent people, and it could
| easily spiral into a Third World War, it does not
| represent the advent of a new, borderless mode of warfare
| in which the cost of untraceably killing a precision-
| targeted human anywhere in the world is similar to the
| cost of a small air conditioner or 20 kg of beef.
|
| The developments we are seeing of the mode of war in the
| Ukrainian invasion _do_ represent such a transition, and
| that is true regardless of how the conflict goes. But
| mostly it is not the Ukrainians and Russians who are
| responsible for the transition; it was an inevitable
| result of developments in batteries, motors, power
| electronics, and 3-D printing and (more broadly) digital
| fabrication.
|
| What will the new equilibrium look like, now that
| statehood is effectively meaningless? Well, it might be
| better or it might be worse, but not many people
| currently alive will live long enough to find out.
| numpad0 wrote:
| Gated how? It's all on textbooks, industry standards, Internet,
| everywhere. You could buy a KHR-3 without even driver's license
| for $1.5k cash for past ~20 years. I guess CUDA was technically
| gated behind "I swear I'm not a bad guy" button, but that was
| it.
|
| I'm surprised that Ukraine isn't DIYing full-on solid motor
| cluster SAMs and armor piercing ATGMs. I thought those kinds of
| devices were something just about any sufficiently developed
| country can do in days to weeks should such national emergency
| arises and all bets were off, except nations in peacetime has
| moral obligations to do no evil.
| fusionadvocate wrote:
| Why spend so much effort to achieve an "exact" gear ratio? Having
| more zeros does not equal to being more "precise".
|
| Also, I wonder how resistant this mechanism is to wear and
| fatigue.
| skeeter2020 wrote:
| >> Having more zeros does not equal to being more "precise"
|
| Isn't having more decimal places the exact definition of
| precision (vs accuracy)?
| munchler wrote:
| The point is that those decimal places don't have to be
| zeros. 7.893 is just as precise as 8.001.
| a3w wrote:
| Yet for some reason unknown to me, people get annoyed when
| you tell them ,,let us meet at 13:37. that is no more
| accurate than let us meet at 14:00 hours"
| VMG wrote:
| 14:00 is a Schelling point
| sabareesh wrote:
| That was confusing part of this video . May be there are some
| limitation on the tools he uses to tune
| dvt wrote:
| I don't think the _number_ of the gear ratio really matters,
| what matters is that you know what it actually _is_ (since
| every IK calc depends on said ratio); 8:1 is probably
| arbitrary and /or looks nice & might simplify some stuff.
| eichin wrote:
| It might be a lot easier to _check_ the ratio "by hand"
| (by counting rotations etc) if it's numerically simple.
| (IIRC in some earlier videos he noticed that the pulley
| size ratio wasn't producing the expected movement ratio,
| _because_ they were built as an obvious 8:1 or 10:1 or
| something, and didn 't match - which led to him figuring
| out the subtleties of the design - I can easily imagine
| wanting to preserve that aspect just for debugging, at that
| point, even if you _now_ have correct math.)
| mlhpdx wrote:
| From a coding point of view it's also nice if all the
| drives are exactly the same, so each isn't compensated for
| separately. But yeah, just a nicety.
| michaelt wrote:
| Well, it probably wasn't _that_ much effort. When you 're 3D
| printing you're going to end up printing everything 2-3 times
| _anyway_ , so why not dial in the ratio while you're at it?
|
| And you can't really declare your design is "high precision"
| and present yourself as someone others should take transmission
| design advice from if you aimed for a gear ratio of 8 and
| achieved "somewhere around 7.9 to 8.2"
| LeifCarrotson wrote:
| It probably doesn't matter so much whether it's 7.913 or
| 8.186, but it would be important to know the exact value for
| kinematics. One way to do that is to build an object very
| accurately, the other is to build inaccurately and then
| measure the result after the fact.
|
| It's also interesting because competing actuators with
| strain-wave, cycloidal, or planetary gearboxes will state
| _exactly_ what the ratio is. The actual gear teeth may not be
| spaced out perfectly around the circumference, but the number
| of teeth is an integer with an infinite number of zeros.
| tonyarkles wrote:
| Yeah, I think one of the nice things about making it a
| "clean" number (either an integer or a rational with a
| small integer denominator) is that you can easily validate
| it without needing high-precision measurement equipment:
| put a mark on both gears (maybe even embedded in the 3D
| print), line up the marks, rotate the large gear 1 full
| rotation, and count the number of rotations the smaller
| gear makes. Check to see if the marks line up perfectly
| after those rotations.
| nullc wrote:
| His capstan reduction can't go all the way around even
| once.
| hinkley wrote:
| It could though. I don't think the thought has occurred
| to him yet. He could make the stack twice as high and go
| around twice as far. If you moved the worm gear you could
| go farther, but I don't know how he would do that with
| his drive.
|
| He could also go with narrower rope, and spread the load
| over more windings, which would give him more throw.
| mlhpdx wrote:
| What are the loads on a drive in this use case? 35lbs
| robot bouncing on one foot would be 350lbs-ish of dynamic
| load? That can be handled with 2mm Dyneema.
| ErigmolCt wrote:
| Getting that ratio nailed down also makes future designs more
| predictable I think
| throwawayffffas wrote:
| I think it's about kinematics, the more precise your gears the
| better the model fits the real world.
|
| That's why pro crews don't use gears and ropes. At high
| impulses deformations and elasticity throw the kinematics off
| what's actually happening. Modeling the deformations and the
| elasticity is a computational no no. Instead what you see is
| the motors right on the joints.
|
| At least that was the case last time I had a look at robotics.
| PaulDavisThe1st wrote:
| more than 30 years ago I was writing code for a "robotic"
| device that used motors, directly on the joints.
|
| the motors were so sloppy the company wasted a ton of money
| [0] having me write heuristics to tackle the errors they
| accumulated over several hours.
|
| one of his whole points is that by using dyneema (rope),
| there's almost no elasticity at all in the capstans.
|
| [0] relative to the cost of better motors
| michaelt wrote:
| _> That 's why pro crews don't use gears and ropes. [...]
| Instead what you see is the motors right on the joints._
|
| The answer here, as with so many things in robotics, is: It
| Depends.
|
| UR10e robot arm that can lift a 4kg object with a reach of 1m
| and has sub-1mm repeatability? Strain wave gears in the base
| and shoulder joints, 100:1 ratio.
|
| MIT Mini Cheetah robot dog that can do backflips? 6:1
| planetary gearbox.
|
| Shadow Hand with 20 degrees of freedom? Tendon driven, with
| the 20 motors in the forearm to keep the fingers slim.
|
| Little dinky Huggingface SO-101? Servo motors, integrating
| 1:345 gearing with a series of 6 tiny brass gears.
|
| Mid-price CNC milling machine, if you call that a robot?
| Really long ballscrews, driven by stepper motors.
| Joel_Mckay wrote:
| In general, for some platforms each gear mechanism adds
| backlash precision loss, lower energy efficiency, and might
| not be back driven.
|
| >Mid-price CNC milling machine
|
| A ball-screw is mostly decorative on small machines... =3
| michaelt wrote:
| On the other hand, a 100:1 gearbox gives you much-needed
| torque if you're lifting a load at the end of a long arm,
| it makes your encoder 100x more precise (in terms of
| repeatability) and it makes your motor brake 100x
| stronger.
|
| Back-drivability is the enemy of precision, so many
| robotic applications can do without it.
| Joel_Mckay wrote:
| Almost all modern servo driven units I've seen prefer to
| allow some compliance in the end effector. The UR5 and
| UR10 series for example can use force limiting control
| loops, and are safer to use around people.
|
| The old "fast, cheap, or good... choose any two joke is
| mostly still true. =3
| michaelt wrote:
| The UR10 uses 100:1 strain wave gearing in the base and
| shoulder joints.
|
| You're right that it has a freedrive mode, and force
| control modes. But it's a rigid, low-backlash robot with
| the compliance achieved in software afterwards.
|
| Expensive, naturally, but none of the problems that come
| with things like series elastic actuators.
| kragen wrote:
| Surely you mean driven by closed-loop servos with encoders,
| don't you? Jacques Mattheij wrote a long post about how he
| ended up having to replace all the CNC machines he sold
| that used stepper motors because he didn't know any better
| at the time, and brushless motors are a lot faster and more
| powerful as well as not losing steps.
| michaelt wrote:
| I guess "mid price" isn't the most helpful term when
| machines vary from $100 to $100,000 huh?
|
| I think the X-Carve 3-axis wood carver uses stepper
| motors with _belts_ of all things. The Shapeoko Pro is
| leadscrews and stepper motors. Wazers, I believe, are
| belt-and-servo driven. And a lot of 'CNC conversion
| kits' you can order online use stepper motors. Plus of
| course laser cutters have really low torque requirements,
| so they've got a lot of design freedom.
|
| Arguably those are "cheap" rather than "mid price" it
| just felt weird to declare a $4000 machine to be "cheap"
| kragen wrote:
| I think there are CNC machines that cost 100 times more
| than US$100k.
| regularfry wrote:
| Some products should be compared on a log scale. CNC
| machines are a very good example.
| kragen wrote:
| The middle of a log scale from US$100 to US$10M would be
| US$30k.
| WillAdams wrote:
| Actually, it was the Shapeoko 1 which introduces the idea
| of belts (MXL), then switching to Gates GT2 belts with
| the SO2 (ob. discl., I got a free machine for doing the
| instructions, see Github). Since it was opensource, the
| X-Carve was forked from the SO2, though the X-Carve Pro
| was a completely new design.
|
| Note that belts were continued through the Shapeoko 3 (I
| got a machine as a "thank you"), though the Z-axis got a
| leadscrew in the Z-Plus upgrade, then the Pro (since, I
| got a job with the company and got an XXL as part of my
| employment), then the 4 (the original Pro is referred to
| as a 4 Pro sometimes), and it is only with the 5 pro that
| ball screws were switched to for all axes (and I now have
| a 5 Pro).
|
| For an example of what a belt-drive CNC can do see:
|
| https://community.carbide3d.com/t/hardcore-aluminum-
| milling-...
| topspin wrote:
| > At high impulses deformations and elasticity throw the
| kinematics
|
| Sure. Yet evolution has achieved astonishing kinematics with
| all manner of deformation and elasticity inherent to the
| materials, and also constantly changing physical properties,
| using low resolution data. We cannot build permanently lash
| free mechanical devices at reasonable cost and reasonable
| size/weight. Eventually, the answer must be pervasive real-
| time compensation throughout the kinematic model.
|
| > Modeling the deformations and the elasticity is a
| computational no no.
|
| Why? Nervous systems do this. That's why you can change your
| shoes and still walk upright.
| BHSPitMonkey wrote:
| In the video he mentions how the specific type of Dyneema
| cord he's using is well-suited for the application (compared
| to other kinds of rope/cord). It's particularly strong,
| light, and inelastic; a lot of climbing equipment uses a
| version of it for similar reasons.
| mlhpdx wrote:
| > Modeling the deformations and the elasticity is a
| computational no no. Instead what you see is the motors right
| on the joints.
|
| That sounds like "It's not wrong, we just don't do it". There
| are some amazing examples of imprecise drive systems
| compensated for by excellent control systems all over the
| world, for millions of years.
| ErigmolCt wrote:
| Even small deviations can compound over time in a real-time
| system
| jedimastert wrote:
| > Also, I wonder how resistant this mechanism is to wear and
| fatigue.
|
| He actually discussed this in an earlier video for his initial
| tests on the capstan drive. He ended up testing the rope he
| used for around 358 hours (two weeks) on continuous use in the
| drive itself with very low backlash
|
| https://www.aaedmusa.com/projects/capstandrive
|
| https://youtube.com/watch?v=MwIBTbumd1Q&t=10m
| hinkley wrote:
| Because when a real engineer puts 2 and 2 in and gets 3.8 out,
| it _vexes_ them and they want to at least know _why_ they can't
| get 4. He's trying to make a machine that does what he told it
| to do, so that he understands what is actually happening.
| AIorNot wrote:
| Amazing presentation! - somebody hire this kid asap
|
| https://www.aaedmusa.com/
| abraae wrote:
| I'm going to tell my 12 year old that when he leaves education
| he wants something like this on his personal web site:
|
| "CARA (Capstans Are Really Awesome) is my latest quadrupedal
| robot, following ZEUS, ARES, and TOPS. Built over the course of
| a year, CARA is easily my most dynamic and well-designed
| quadruped yet."
| andrewstuart wrote:
| He might be perfectly happy doing projects and YouTube.
| dvt wrote:
| Likely makes more money, too!
| geerlingguy wrote:
| For many, no; taking on lots of sponsorships, you can make
| a good amount of money (especially the ones where you agree
| to do X posts across Y social media accounts for Z period
| of time, essentially being fully sponsored across a large
| swath of life).
|
| But for a lot of tech/engineering channels, it'd be
| immensely difficult to make the same salary as you could
| working at a FAANG or the like. (I'm making about half what
| I made when I had a W-2, but it's enough).
| sitkack wrote:
| You just need to start selling supplements, anti-aging
| creams and time shares.
| abtinf wrote:
| Do fun projects of your choosing vs the grind of
| corporate life.
|
| The former has a rather large non-pecuniary component of
| total compensation.
| geerlingguy wrote:
| Exactly; especially in terms of stress--which is a major
| problem with my chronic illness, and both the main reason
| I'm happy to be away from a W-2, but also the thing that
| makes me most nervous as I'm dependent on marketplace
| healthcare (which is quite expensive for much worse
| benefits), and it's harder to get things like
| life/disability insurance as an independent.
| julienfr112 wrote:
| Being a top YouTube producer is not without stress :
| Reacting to the change in number of followers, responding
| to comment that can be unpolite, managing sponsors...
| MiguelHudnandez wrote:
| Thank you for taking a pay cut to do what you do, I'm so
| glad your channels exist. Also please remember to take
| vacations! (trade shows don't count)
| benhurmarcel wrote:
| If you're not in software the salary you'd be making as
| an employee would be much lower than what you refer to as
| "FAANG" though
| busymom0 wrote:
| His current Patreon has 57 paid members. Unless he has
| another revenue stream, I think he'd need more paid
| members.
| ekianjo wrote:
| youtube ads and sponsorship are his additional revenue
| streams
| dismalpedigree wrote:
| He is a senior mechanical engineering student at purdue.
| I think the channel is something he is just getting
| rolling in his spare time.
| abtinf wrote:
| That would be a terrible path for someone with this extreme
| level of _demonstrated_ talent, motivation, and follow-through.
|
| Much better for someone to fund a startup run by him.
| salomonk_mur wrote:
| Why would you put someone with clear talent at building stuff
| in charge of running a startup? He'll get bogged down in
| lawyers, day to day operations and growth strategies.
|
| Hire him and put him in R&D in some robotics company.
| wraptile wrote:
| Yes but also the robotics industry notoriously has an
| extremely low shipping rate. So choose your bog I guess?
| hinkley wrote:
| And some of them are military focused.
| robotresearcher wrote:
| Y'know, sometimes smart, dedicated, curious, self-directed
| people are that way with a lot of things.
|
| I was a professor for a long time. My observation was that
| often a top researcher was also a top teacher and even a
| top administrator. There are exceptions of course. But if
| someone is smart and effective at using their attention,
| those skills transfer to many things.
|
| It's a pain in the ass when allocating university roles. I
| want that person to do EVERYTHING 'cos they always deliver.
| ppaattrriicckk wrote:
| ... what tf?
|
| On top of studying engineering at uni, his "side-gig" is
| being creative, empathetic, and fantastic at communication
| - and your prime recommendation is to "hire" him to be a
| specialist hidden away in the back office? Which interwebz
| forum are you on?
|
| EDIT: My last question is clearly an echo-chamber
| statement. But that doesn't subtract from the fact that,
| yeah, should he found a business, yes, he'll deal with
| certain "BS". That is the weight we'll all carry. But he's
| quite likely capable of moving civilization forwards, so...
| :shrug:
| otikik wrote:
| Eugh. No. Let him create stuff and let someone else take care
| of the taxes and payroll and the sales and all that other
| stuff.
| lhmiles wrote:
| Nobody hire him!
| dev0p wrote:
| Very impressive. Commenting to be able to find this later
| because I need to keep tabs on this guy. The CD launcher is
| incredibly cool.
| TheBozzCL wrote:
| Thanks for sharing this! What a treat of a video. It's a fun
| project, and it's presented very well. This guy has a talent for
| communication - the video was super clear and well explained. I
| really admire that ability and I want to get better at it.
| mikewarot wrote:
| It's amazing what he's done in terms of the robotics, and the
| presentation of it to the viewer. I'm amazed at the quality of
| cinematography on the internet these days.
|
| The implications of the tools we now make available for use in
| our own personal workshops are still being discovered, and will
| be for some time.
| ErigmolCt wrote:
| Feels like the golden age of DIY engineering
| sneak wrote:
| I agree 1000%, which is why I find the whole "the internet
| sucks now" movement really disheartening. There are huge
| upsides to a network this large.
| zelphirkalt wrote:
| DIY and "the Internet" (the web?) have fairly little
| overlap, aside from learning resources existing. Those
| learning resources could just as well exist, and probably
| better or more, in a healthier web. I don't think
| contrasting the 2 things is making much sense.
| csours wrote:
| Professor of Upstairs Neighboring.
| https://youtu.be/8s9TjRz01fo?t=1128
| micromacrofoot wrote:
| I'm so excited for a smaller open source version of this, I'd
| love to make one. What a great project.
| andrewstuart wrote:
| He's got the magic combination of tech skill plus ability to make
| and edit entertaining videos.
| heap_perms wrote:
| Fascinating! I want to get into this type of stuff. But I have no
| idea where to start, I just have just a CS degree and 3 years
| experience as a developer.
| taneq wrote:
| Arduinos and hobby servos. No, neither of them are "industrial
| grade" and yeah, you'll reach their limits pretty quickly, but
| building a physical thing that does stuff is (in my experience)
| a huge motivator.
|
| Or if you're already all over the basics, figure out what kind
| of stuff you want to build and then try and build it. :)
| Paddywack wrote:
| Can you recommend where to find beginners projects that "do
| stuff".
| Retr0id wrote:
| Just like the article, there's a huge amount of hobbyist-
| accessible projects on youtube, you can click around the
| recommended videos.
| sitkack wrote:
| Grab a servo and start playing with it.
| taneq wrote:
| https://hackaday.com/ - cool projects and interesting stuff
| https://news.sparkfun.com/tags/tutorial - tutorials on
| embedded software, electronics, etc.
| https://learn.adafruit.com/ - electronics tutorials
| Mars008 wrote:
| To begin with you can get a cheap robotic kit from Amazon,
| there are many of them, and put it together. That's
| probably the easiest and fastest way. From here you can
| read more about servos and controllers, modify its
| mechanics and software.
| adolph wrote:
| I recommend a Brachiograph build. It will introduce you to some
| fundamentals of PWM and inverse kinematics. It is well
| documented but not cookie-cutter. Using a Raspberry Pi will
| give you more direct access to running the servos than the
| microcontroller experience. All the parts are infinitely
| reusable afterward if you don't want to keep it around.
|
| https://www.youtube.com/watch?v=u4Jh1daCl60
|
| https://www.brachiograph.art/
|
| https://github.com/evildmp/BrachioGraph Sample
| Supply List for $80 budget: Pi Zero with header $20:
| https://www.adafruit.com/product/6008 Power supply $9:
| https://www.adafruit.com/product/1995 SD Card $10:
| https://www.adafruit.com/product/1294 Three hobby servos
| $18: https://www.adafruit.com/product/169 Breadboard
| wires $5: https://www.adafruit.com/product/153 Breadboard
| $5: https://www.adafruit.com/product/64 Glue, popsicle
| sticks, pen and paper $10
| ErigmolCt wrote:
| A solid place to start is building something simple
| ZeWaka wrote:
| Just saw this at Open Sauce last weekend! Super cool project,
| looking at all the gearing was fascinating.
| s_dev wrote:
| Cara is the Irish word for 'friend'. Not sure if thats what was
| intended or is just a coincidence.
| kragen wrote:
| Also the Spanish words for "face" ( _no me gusta tu cara,
| boludo_ ) and "expensive and female" ( _esa computadora es re
| cara, boludo_ ). https://en.wiktionary.org/wiki/cara tells us
| it also has meanings in Aragonese, Asturian, Catalan, Crimean
| Tatar, French, Galician, Indonesian, Italian, Latvian, and
| another couple dozen languages.
| Keyframe wrote:
| Male genital organ in few of the balkan languages (spelled with
| K), pronounced the same. So, there's that too.
| srameshc wrote:
| I remember a post previously related to him here on HN but I am
| surprised at how I forgot about him and how cool he is to build
| all these incredible stuff and also teaches in his videos. I am
| subscribing so that I never miss anything from him again.
| aldousd666 wrote:
| I watched this last week and my jaw was on the floor. He's both a
| great technician, and he has the personality to make it
| interesting. He walked through his testing strategy far enough
| that you could understand his methodology and the thought process
| behind it, but didn't belabor it by making us watch it all.
| Banger!
| mikestaas wrote:
| > Programming takes the cake for what is both my most and least
| favourite part of any build. Nothing quite makes you pull out
| your hair and ask yourself, 'What the heck have I gotten into?'
| Like spending weeks programming a robot that just won't work.
| Eventually though, you fix that one line of code that makes all
| the difference. And then it's smooth sailing. Well, kind of.
|
| I feel this deeply, also this whole video is quality content.
| yrcyrc wrote:
| This is absolutely amazing, awe inspiring.
| mnurzia wrote:
| Wow! I actually met Aead last week while he was printing parts
| for this project (we both work at the same place). Surreal to see
| it at the top of HN.
| sarthaksoni wrote:
| This personal site makes me genuinely jealous--in the best
| way.Really awesome side projects and great intro.
|
| Time to raise my own bar.
| fitsumbelay wrote:
| this guy's work is pretty amazing I whole heartedly believe that
| I'll own a gang of (armed) quadrapets for home/property/personal
| protection within the next 10 years. I'm equally worried that
| once these become commodities they might be worse than an
| electric scooters have become to us bipeds on sidewalks but on
| balance I can't wait
| roschdal wrote:
| I don't like these robot dogs.
| cryptoegorophy wrote:
| How do we make such robots intelligent? Like you only tell it to
| learn to jump the rope and then it goes through trial and
| error(s) to figure out a way to do it, and if it can't and needs
| a physical upgrade then it tells you that? (Like a certain gear
| ratio etc)
| scotty79 wrote:
| https://developer.nvidia.com/blog/introducing-isaac-gym-rl-f...
| scotty79 wrote:
| It might be fun to optimize the shape of the rolling contact
| surface of the capstan drive away from cycloid to make it even
| better suited for specific application, like a robot dog leg that
| smoothly runs for miles.
| joeevans1000 wrote:
| I recently found these videos. Amazing guy, amazing skills, great
| humor.
| jankovicsandras wrote:
| Very cool robot dog and interesting video! Can the dog climb
| stairs? Isn't capstan drive temperature sensitive, e.g. the ropes
| will be shorter in cold and longer in warm wheather?
| pillars wrote:
| Some resources related capstan drive:
| https://www.osti.gov/servlets/purl/1340266
| https://fab.cba.mit.edu/classes/865.21/topics/mechanical_des...
| ErigmolCt wrote:
| This is an absolute masterclass in DIY robotics. With a proper
| battery and a tougher foot material, this thing could really
| stomp.
| amelius wrote:
| Speaking about battery, how much current does it draw while at
| rest?
| froh42 wrote:
| What a horrible video is this, with the robotic translated AI
| voiceover?
|
| Update: Ah, weird, if I watch the non-embedded one on youtube it
| is the original in English with normal sound. It's the one
| embedded on his web site which has AI translation to German.
| indigo945 wrote:
| That's not the video's fault, but YouTube's. YouTube has
| started adding automatic AI voiceover translations to all
| videos, unless the uploader explicitly disables them for each
| single video. It's opt-out and the option is well-hidden, so
| most uploaders will not disable it.
|
| As an end user, there's nothing you can do to prevent from
| seeing them. But you can change the audio track to the original
| while the video is playing.
| jedimastert wrote:
| > YouTube has started adding automatic AI voiceover
| translations to all videos, unless the uploader explicitly
| disables them for each single video.
|
| WHAT?!? It a time when there is a growing animus towards AI
| generated content, for many content creators this would be
| tantamount to slander
| laughing_snyder wrote:
| https://github.com/YouG-o/YouTube_No_Translation
| amelius wrote:
| It's just a gut feeling but I'd trust a feedback based backlash
| elimination mechanism more than rope based, especially in the
| long run and/or with a large deployed base.
| heeton wrote:
| But, why?
| amelius wrote:
| Like I said gut feeling. I suppose over time there may be
| some play in the axles, for example. Something feedback could
| compensate for but a rope could not.
|
| Anyway good engineering requires extensive testing over many
| hours of movements.
| jedimastert wrote:
| > Anyway good engineering requires extensive testing over
| many hours of movements.
|
| He actually discussed this in an earlier video for his
| initial tests on the capstan drive. He ended up testing the
| rope he used for around 358 hours (two weeks) on continuous
| use in the drive itself with very low backlash
|
| https://www.aaedmusa.com/projects/capstandrive
|
| https://youtube.com/watch?v=MwIBTbumd1Q&t=10m
| nickdothutton wrote:
| Similar mechanism might be good for astronomical telescope
| mounts. Gears are often a problem and nobody seems to have solved
| it.
| throwaway2037 wrote:
| Another cool project from this person's blog: "Wrist Mounted CD
| Launcher" -> https://www.aaedmusa.com/projects/wrist-mounted-cd-
| launcher
|
| It definitely gives off Elysium (film) vibes.
| hypertexthero wrote:
| Amazing work, beautifully presented.
|
| Geordi LaForge reminds me of Aaed.
| einrealist wrote:
| What is the power consumption of these robots? I often wonder how
| limited and viable autonomous robots really are. When I look at
| Tesla's Optimus or Boston Dynamics' spectacular robots, how
| quickly do they need to be recharged?
| hinkley wrote:
| My understanding is that those motors he uses are pretty
| special. And I would expect "efficient" to be part of that
| special. You're optimizing for torque and accuracy per unit of
| mass and energy in this sort of space. I know he talked about
| them in earlier videos but I no longer recall the details.
| einrealist wrote:
| Aside from the onboard computing required to power the AI
| model controlling the robot, which also consumes energy, it
| is important to be as efficient as possible. However, if an
| Optimus is intended to replace human labour, such as lifting
| objects and wander around with it, the energy efficiency of
| the platform becomes negligible.
|
| The platform in the video and the robot dogs from Boston
| Dynamics are ideal for tasks where they are only limited by
| their own weight and the amount of computing power required
| to navigate, such as exploration.
|
| I suppose that's why we mostly see autonomous delivery robots
| on wheels.
|
| Or maybe I am being too pessimistic about other platforms...
| kokorikooo wrote:
| The problem with gear is that they suffer from latency.
| otikik wrote:
| Nice to see a cuadruped robot that doesn't sound like a swarm of
| angry bees.
| tgtweak wrote:
| I think he'll have success with youtube/vlogging more than
| getting into the corporate world honestly - especially with some
| healthy sponsorships and great projects like this.
| FugeDaws wrote:
| incredibly impressed everytime i watch one of his videos
| syarb wrote:
| This project is so cool! Congrats Aaed.
|
| Breaking Taps on YouTube did a really awesome video on a somewhat
| similar mechanism (I'm no mechanical engineer haha, it was new to
| me!), rolling contact joints. I love the idea of using
| string/ropes. Worth checking out as well if this kind of stuff
| interests you! https://www.youtube.com/watch?v=TQiLLcumqDw
| unicorn_chaser wrote:
| New here and just stumbled upon this. Seen these "robodogs" live
| in Vegas mining conference. The usage is picking up, their
| functionality and range of movement is so much more advanced now,
| and the list of actions they can complete much more complex.
| Awesome stuff!
| ezekiel68 wrote:
| I had never seen a rope use a robot dog before so I clicked
| immediately. It wasn't what I expected from the headline, but
| very cool nonetheless.
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