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CARA – High precision robot dog using rope

aaedmusa.com

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Re: CARA – High precision robot dog using rope

#151

Post by hinkley »

nullc wrote: post #95
tonyarkles wrote: post #34

Earlier quoted context omitted.

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 i…

His capstan reduction can't go all the way around even once.

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.

Re: CARA – High precision robot dog using rope

#152

Post by numpad0 »

kragen wrote: post #116
lazide wrote: post #112

Earlier quoted context omitted.

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.

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 i…

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.

Re: CARA – High precision robot dog using rope

#153

Post by einrealist »

hinkley wrote: post #148
einrealist wrote: post #132

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?

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.

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...

Re: CARA – High precision robot dog using rope

#154

Post by mlhpdx »

Keyframe wrote: post #65
btbuildem wrote: post #3

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.

"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?

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.

Re: CARA – High precision robot dog using rope

#156

Post by mlhpdx »

hinkley wrote: post #151
nullc wrote: post #95

Earlier quoted context omitted.

His capstan reduction can't go all the way around even once.

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.

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.

Re: CARA – High precision robot dog using rope

#157

Post by mlhpdx »

throwawayffffas wrote: post #37
fusionadvocate wrote: post #7

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.

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 lo…

> 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.

Re: CARA – High precision robot dog using rope

#158

Post by mlhpdx »

dvt wrote: post #23
sabareesh wrote: post #12

Earlier quoted context omitted.

That was confusing part of this video . May be there are some limitation on the tools he uses to tune

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.

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.

Re: CARA – High precision robot dog using rope

#159

Post by otikik »

abtinf wrote: post #48
AIorNot wrote: post #8

Amazing presentation! - somebody hire this kid asap https://www.aaedmusa.com/

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.

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.
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