Astro Hacker News - CARA 2.0 – “I Built a Better Robot Dog”

Animats |next [-]

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 them that makes them "robot motors".

Motor overheating might be a problem. The dog, just standing, has its motors stalled under load, converting power to heat. Drones don't do that. Temperature feedback would help if this thing has to operate for extended periods. Remember yesterday's article on humanoid robots and their cooling problems.

The motor controller is nice too, and cheap at $49. Needed fixes to the firmware, but that's not surprising at the price. High performance motor controllers used to cost about $1000.

Repurposed drone technology has done wonders for legged robots. We're not quite at the point where limb drive hardware is off the shelf, but it's way better than it used to be.

[1] https://www.xntyi.com/tyi-5008-kv335/kv400-high-speed-brushl...

regularfry |root |parent |next [-]

It doesn't have to stall to stand still. Or squat, at least. With that leg layout it can safely rest against its backstops when the motors switch off. The drive motors, anyway. The hip motors probably still need to hold vertical balance, but that's intermittent, not a stall load.

barrenko |root |parent |next |previous [-]

Could I pursuade you to expand on "Repurposed drone technology has done wonders for legged robots." ? Thanks!

cyanf |root |parent |next [-]

For legged, you want high torque and backdriveability (for shock absorption).

Agricultural drone motors like the eaglepower 8308 are ideal.

They’re cost effective, (~$80 from aliexpress) & you can pair them with a 3d printed cycloidal drive to fulfill both requirements.

Industry actuators are an order of magnitude more expensive than this.

Extra: If you go down this path, you’ll need a driver. The Xdrive is frequently recommended, but there’s a clone that’s significantly cheaper: https://makerbase3d.com/product/makerbase-xdrive-mini-high-p...

lastdong |root |parent |next [-]

This is pretty cool, thanks for sharing. I wish there was a (mostly) 3d printable Cara mini, but I’ll start with Cara.

regularfry |root |parent [-]

The layout is doable with hobby servos, but you'd need to patch in current sensing for that bit of the feedback. It's not terribly difficult conceptually but it's an extra complication that most servo power distribution boards don't give you.

You can also strap a capstan to the servo axle, if that's your thing. I've prototyped that myself in the past. You can go surprisingly far with an FDM printer, an SG90, and some dyneema bowstring. One thing I haven't tried is modding one for continuout rotation to get around the way the capstan drive limits the output angle you can achieve - I was happy reducing from ~180deg to ~45deg for what I was doing - but that's relatively well-trodden ground. Might pull that project out of the storage box it's languishing in at some point.

cyanf |root |parent |previous [-]

Motor: https://www.aliexpress.us/item/3256804897857573.html?gateway...

The 90KV version is what you want.

franciscop |root |parent |previous [-]

Look at the original video/article, they used drone motors for the robot dog, by reusing the rotor/stator and rewinding the coils manually.

rmast |root |parent |previous [-]

If you read the epilogue, they weren't able to achieve the under $1000 price goal. Total cost ended up being around $1,450. Pretty good price reduction compared to CARA 1.0 though.

Hypothetically if I were to want a quadrupedal robot to experiment with it's not an impulse buy/build, but getting closer to that point... whereas $3000+ is a hard pass (e.g. Apple Vision Pro territory).

regularfry |root |parent [-]

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.

15155 |root |parent [-]

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.

KaiserPro |next |previous [-]

I love Aaed. Not only are the youtube video excellently produced and well researched, the website is a mine of information.

This is spectacular as a reference, which youtube isn't

shutterkiller |next |previous [-]

The mechanical simplicity here is appealing. A lot of robot dog projects feel optimized for demos first; this looks more grounded in maintainability.

abelsm |next |previous [-]

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.

pbmonster |next |previous [-]

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, it looks a bit... "low gear" in the videos.

RoxiHaidi |next |previous [-]

That's impressive! good job

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npodbielski |next |previous [-]

Seeing stuff like this, I am wondering why the hell I am doing software. This is much cooler than CRUD for DB data nth time.

igleria |root |parent |next [-]

Same. I do have an excuse due to lack of space in my apartment, but once we move...

voidUpdate |root |parent |previous [-]

Hardware can be quite expensive and time-consuming, instead of just writing code (free) and running a command to deploy (quick) you have to get hold of good motors (expensive) and design and manufacture parts (slow)

npodbielski |root |parent [-]

You do not have to convince me! I already love it!

Springtime |next |previous [-]

I like the wide layout of the site but just on a readability front on a widescreen monitor after the opening more narrow paragraphs it changes to full width text layout and those could benefit from a `columns: 2` in CSS to split them since reading long width paragraphs is a bit difficult.

3form |next |previous [-]

People are all discussing the technical aspects of the device, which is great and all, but forgetting the one aspect I am in awe of: how googly eyes once again make everything 300% better.

defrost |root |parent [-]

A truism that sadly not all are onboard with: https://www.bbc.com/news/articles/c1wl5jp94eno

crimsoneer |next |previous [-]

As a man who always desperately wanted a Sony AIBO (and is now only put off by the bonkers $300 a year AI subscription), I am unduly excited.

aaron695 |previous [-]

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