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CARA 2.0 – “I Built a Better Robot Dog”

aaedmusa.com

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Re: CARA 2.0 – “I Built a Better Robot Dog”

#51

Post by elictronic »

abelsm wrote: post #16

Awesome video. It's interesting, informative, and entertaining. Founders I talk to that are doing hardware, broadly speaking, say it's a competitive advantage as it's not as crowded. Content like Aaed's will hopefully nudge more people into it.

It’s because hardware has so many limitations that get glossed over vs. software. Manufacturing issues, sourcing issues, regulatory timelines, physical returns, inventory management, and oddities in the physical world are much easier to spot by an investor. Nikola motors and hills?

It can take 6 months once your product is finished to be legally allowed to sell it and even then it could be forced to be recalled or be redesigned. It’s a much more difficult environment to deal with vs I spent a few months throwing together this slop code, thanks for my multi-million dollar buyout.

Re: CARA 2.0 – “I Built a Better Robot Dog”

#52

Post by Gracana »

JKCalhoun wrote: post #33
Animats wrote: post #3

3 DOF per leg, so it needs 12 motors and controllers. Getting that under $1000 is nice. Here's the US$18 motor: [1] Those things are getting really cheap. He did have to rewind it, though, for more turns with thinner wire. The manufacturer mentions that you can order with "custom Kv", which means you might be able to get a different winding from the factory if you order a reasonable quantity. Especially if you tell t…

"Temperature feedback would help if this thing has to operate for extended periods." Rather than thermistors all over the place, perhaps an onboard program could calculate motor temperature by integrating current sent to each over time—assumed some degree of cooling (and perhaps here a single temperature sensor might measure ambient temperature of the environment… or could just assume "indoor temperature").

That’s how industrial VFDs do motor overload protection, they just keep track of heat accumulation (based on current) vs dissipation (based on fan speed) and fault when a threshold is reached. Probably there’s more nuance to it, but that’s the gist of it.

Re: CARA 2.0 – “I Built a Better Robot Dog”

#53

Post by erwincoumans »

Very nice project. If you like this, the Pupper quadruped robot project by Stanford University is also interesting, with RL training pipeline as well and well-documented open source instructions for 3d printing etc. https://pupper-v3-documentation.readthedocs.io/en/latest/gui...

Re: CARA 2.0 – “I Built a Better Robot Dog”

#54

Post by peterleiser »

erwincoumans wrote: post #53

Very nice project. If you like this, the Pupper quadruped robot project by Stanford University is also interesting, with RL training pipeline as well and well-documented open source instructions for 3d printing etc. https://pupper-v3-documentation.readthedocs.io/en/latest/gui...

That is very cool. Their kit is $3,000 and the unaffiliated kit is $2,350, so definitely a commitment.

Re: CARA 2.0 – “I Built a Better Robot Dog”

#55

Post by Animats »

fennecfoxy wrote: post #38
JKCalhoun wrote: post #33

Earlier quoted context omitted.

"Temperature feedback would help if this thing has to operate for extended periods." Rather than thermistors all over the place, perhaps an onboard program could calculate motor temperature by integrating current sent to each over time—assumed some degree of cooling (and perhaps here a single temperature sensor might measure ambient temperature of the environment… or could just assume "indoor temperature").

I would rather just have temperature sensors over the place. More reliable.

For a toy, you might just have a simple thermal fuse.[1] ($0.78 from DigiKey, plus "tariff may apply if shipping to the United States". About $0.15 on Alibaba, if you order enough.). For a working machine for field use, you want feedback to the controller, so it can slow down or rest or something when it overheats.

[1] https://www.digikey.com/en/products/detail/cantherm/RT121/28...

Re: CARA 2.0 – “I Built a Better Robot Dog”

#58

Post by fc417fc802 »

fennecfoxy wrote: post #42
tantalor wrote: post #39

Rewinding the motors manually to increase torque is cheating if you can't scale that up and keep the cost down. And, if you can scale that up, then why even mention it? It's not relevant.

Yeah agree. Having to rewind the motors just adds yet another task to the list for someone trying to build this thing. Also BLDC based motors in bots seem to be popular now, used to be steppers and harmonic drives from what I remember reading. Idk why electrostatic actuators aren't getting more popular like HASEL and a few papers on ones using fiber pumps come out recently. I suppose the danger that the high voltages…

> surely we can replicate muscle fiber actions

Considering what muscle fiber looks like on the molecular level you're literally describing nanotechnology and the associated nanofabrication techniques. Surely it's possible to do but we don't seem to be there just yet.

Re: CARA 2.0 – “I Built a Better Robot Dog”

#59

Post by SamBam »

pbmonster wrote: post #9

The jumps are pretty impressive, this thing has some power. I'd be very curious how fast you could get this dog with some reinforcement learning for a proper transverse gallop gait - and if it converges towards a gallop naturally, or if it discovers some other fast gait patterns during learning. Depending on the max speed of the motors/legs, giving it longer foot pads might be necessary for a good gallop. Intuitively…

I wonder how accurate a virtual model could be made of this, which could be iterated on millions of times faster.

My first project as a research assistant in AI was doing evolutionary algorithms on Khepera robots, which had a virtual Java implementation. We were able to evolve some pretty cool behaviors, although I don't know what would have happened if we had uploaded them into a physical Khepera robot.

Re: CARA 2.0 – “I Built a Better Robot Dog”

#60

Post by Animats »

15155 wrote: post #27
regularfry wrote: post #26

Earlier quoted context omitted.

It's $1450 if you discount the construction time, as ever. Which ordinarily wouldn't be worth commenting on, but in this case it means rewinding 12 motors which just sounds like an exercise in tedium and hand pain.

Only because they didn't know how to ask the vendor to do it for them. I guarantee this vendor would be delighted to make them to spec at a 1ku volume, max. Rewinding isn't even a meaningful SKU distinction or line retool, it's a configuration parameter. At 12 motors per product, it's easy to hit MOQ.

Rewinding drone motors for high torque and lower speed seems to be a popular thing. Here's the commercial process of machine winding motors like that.[1] That's a medium-volume machine, loaded and unloaded by hand, and adjustable for different wire and motor geometry. Here's a hobbyist version of a similar winder.[2] And another automatic hobbyist winder. Those wind under uniform tension, and with wire positioning, so you get a smooth, tight winding. This matters if you're going to use the motor much. Doesn't matter as much for short-lived toys.

There should soon be enough convergence that low cost, high torque, low speed models are off the shelf items. It's a great time to be building robots. Used to be all uphill on the parts side.

[1] https://www.youtube.com/watch?v=cMk2qFFcSho

[2] https://www.youtube.com/watch?v=486nUU2FjGU

[3] https://www.youtube.com/watch?v=e-tAsM0K7Sg

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