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CARA – High precision robot dog using rope

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Re: CARA – High precision robot dog using rope

#161

Post by darksaints »

mlhpdx wrote: post #154
Keyframe wrote: post #65

Earlier quoted context omitted.

"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.

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.

Re: CARA – High precision robot dog using rope

#162

Post by syarb »

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

Re: CARA – High precision robot dog using rope

#163

Post by darksaints »

kragen wrote: post #114
Animats wrote: post #88

Earlier quoted context omitted.

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]…

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 r…

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.

Re: CARA – High precision robot dog using rope

#164

Post by robotresearcher »

salomonk_mur wrote: post #80
abtinf wrote: post #48

Earlier quoted context omitted.

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.

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.

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.

Re: CARA – High precision robot dog using rope

#165

Post by Animats »

darksaints wrote: post #163
kragen wrote: post #114

Earlier quoted context omitted.

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 r…

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.

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.

Re: CARA – High precision robot dog using rope

#166

Post by benhurmarcel »

geerlingguy wrote: post #39
dvt wrote: post #21

Earlier quoted context omitted.

Likely makes more money, too!

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…

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

Re: CARA – High precision robot dog using rope

#167

Post by Mars008 »

Paddywack wrote: post #35
taneq wrote: post #32

Earlier quoted context omitted.

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. :)

Can you recommend where to find beginners projects that “do stuff”.

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.

Re: CARA – High precision robot dog using rope

#168

Post by barbecue_sauce »

godelski wrote: post #77
8note wrote: post #74

Earlier quoted context omitted.

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

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 har…

The quote in your intial reply ("It does make me wonder about the algorithm") was referring to the YouTube algorithm.

Re: CARA – High precision robot dog using rope

#169

Post by unicorn_chaser »

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!

Re: CARA – High precision robot dog using rope

#170

Post by godelski »

barbecue_sauce wrote: post #168
godelski wrote: post #77

Earlier quoted context omitted.

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 har…

The quote in your intial reply ("It does make me wonder about the algorithm") was referring to the YouTube algorithm.

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)
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