Bird-inspired drone uses legs to walk and jump into the air | Hacker News Reader

Bird-inspired drone uses legs to walk and jump into the air

spectrum.ieee.org

193 pointsbookofjoe65 comments

Would love to see a pterosaur / bat version of this drone. Birds use one set of muscles to jump in the air and another to flap their wings, limiting how big they can get. That’s because, if you make your wing muscles bigger, then you need bigger leg muscles to support them, then you need bigger wing muscles to support your legs, etc. pterosaurs and bats have tiny little legs and use their “arm” (wing) muscles to do the initial jump into the air. It’s just one set of muscles that are used for both functions, which is why pterosaurs were able to get so big. It does beg the question, tho, why we haven’t seen any truly giant bats.

This pbs aeons video has a great explanation: https://youtu.be/scAp-fncp64?si=hjeWKGBI7riyjE1M

> It does beg the question, tho, why we haven’t seen any truly giant bats.

They're mammals, birds have different respiratory system

"Flow-Through Ventilation

Unlike mammals, birds breathe through continuous one-directional flow of air through the respiratory system. We take air in and breathe it out, sort of like the tide moves in and out of a bay. As a result, our breathing system is said to be tidal. Avians have a non-tidal respiratory system, with air flowing more like a running stream."

https://birdfact.com/anatomy-and-physiology/respiratory-syst...

Nature optimizes. The bigger you get, the more you need to eat. The harder it gets to fly. Fruit bats eat fruits.

Look at the food source and you'll understand the evolution.

> Fruit bats eat fruits.

The most caloric dense source of nutrition available in nature? I don't see why that is a limitation to body size for a flying animal - quite the opposite!

Plants aren't particularly calorie-dense. Meat, on the other hand...

Look at great apes. Large land mammals in general. (Apes came to mind specifically because they usually eat fruit)

Are you aware you switched "fruit" for "plant" there?

Fruits want to be eaten, Veggies don't.

this is almost in "not even wrong" territory, but for the fact that autotrophs are definitionally the entry point for abiotic energy into edible calories for animals, and the observation that the largest terrestrial megafauna are herbivorous.

bamboo is not calorie dense to humans, because we've lost the ability to digest most of it, but pecans are absolutely more calorie dense than even fatty beef.

all else being equal, an ideal carbohydrate source is more calorically dense than an equivalent ideal lean protein source due to the balance in the thermic effect of food between the two. most mammals outside the obligate carnivores are really well optimized for getting calories from plants— this is why we have amylase in our saliva.

fruit bats are the biggest bats

not GP but I think that was the point.

also, volume grows as the cube of linear dimensions which also puts an upper limit on size, as wing surface area only grows as the square (not sure what/how lift grows relative to)

That's why mammals can't breathe at high altitudes that birds can, but I'm not sure if that affects the body plan much in terms of size. The largest birds are smaller than the largest mammals on land or at sea. Then again, lower oxygen levels compared to the past seems to be a limitation for insect sizes too (who have an even less efficient respiratory system).

I also don't think it's the warmbloodedness. There are giant mammals in general after all.

Perhaps it is because bats form large, dense colonies? There is only so many resources available in any given ecological niche, so then for any species that fills a niche one would expect those resources to be divided either among many small individuals or a few large ones. Bat evolution chose the "big colony" route, which I assume favors smaller individuals.

> The largest birds are smaller than the largest mammals on land or at sea

With all my respect to you theory I think comparing size of animals should not ignore the medium they moved in: water, land or air. Weight is (loosely but still) related to size. It’s probably not a coincidence the largest mammals lives on water where they need less energy to supper their weight, and it’s not a coïncidents the largest mammals on earth are way bigger that bats.

The biggest bats are ~1.7m which is not so far from biggest albatros (3.7m).

Also consider the biggest bird (Ostriches) can’t fly. Now I’m trying to picture a swimming gigantic bird.

An Emperor Penguin?

Right! To complete the unusual list : flying fish and... Amphibious fish! Wikipedia says there's 11 of them. Ok stop procrastinating now.

Well, fair. But birds are warmblooded too so that doesn't change much there, and on top of that the difference in requiring bigger lungs for the same amount of oxygen extraction would exactly add much weight per volume, so to speak

Robots and living animals have different limitations and constraints though: compared to separate legs and wings for animals, using one motor with some kind of gearbox to switch output from wings/propellers to legs might have a lower added cost in terms of weight . The legs can stay very skinny. The limitation would be how bulky such a gearbox would be, and how much extra kinetic energy loss it would introduce. At the same time creating functioning wings that can also work as legs sounds like it might be a huge challenge in robotics (unless there's a way to massively simplify it).

Definitely an interesting idea that should be investigated though! :)

(Also, I've seen so many "AI learns to walk" videos that I'm wondering if it could be used to find a design that would work for this task)

Worth pointing out that EPFL's PR release includes a picture of Won Dong Shin (the PhD that actually built it) as opposed to a picture of the lab's director as it sometimes happens in academia.

THIS. Ive found good advisors push there students forward, mediocre ones tend to push themselves. Academic robotics is plagued with profs who do "everything".

The article contains an image of him.

I am assuming IEEE is not travelling the world doing investigative journalism, they will have used whatever media was provided by the university.

Yes because otherwise they would have fact checked that there's no lake Geneva.

Lake Geneva is the English name commonly used to refer to Lac Léman. I suspect you know that, but I don't follow why you object to that name.

Interesting, that's the equivalent of me unilaterally calling New York "Nouvelle Amsterdam" then. But it was simply to tickle Geneva's people.

> that's the equivalent of me unilaterally calling New York "Nouvelle Amsterdam" then

This is very common. The name used by the locals is called endonym and the one used by foreigners is the exonym.

For example Zhōnghuá is the endonym vs China the exonym. Or Magyarország vs Hungary. Or Deutschland vs Germany. Or so I not just list English exonyms Lake Balaton vs Plattensee.

German and Deutsch

The initial GIF is a bit lackluster, as it looks like it’s just walking around dragging a tail. The full video posted later in the article is much more impressive.

https://www.youtube.com/watch?v=-8DJ1a3sLIc

The article itself is worth a read too imo, I found the bits about toes for easier balance and jumping to takeoff energy efficiency interesting.

It's still cute walking around like robots with character

Wow. It really looks like a bird in some of those clips. I know it's still early on but I'm impressed with where we currently are.

First thought when reading the title was that it will look very fragile and clumsy when walking (even real birds do) and that was confirmed by the first video. What's the purpose of actually mimicing bird legs and feet? Why not use something more simple like wheels on a board that has a spring for example? I expected the article to justify why, but to me it seems like the big thing was the jumping itself, which does not require complex bird anatomy necessarily. There's probably a good reason that I missed, but this feels like a too direct translation of the bird feature, unless the purpose is specifically to make it look and move like a real bird.

Spy drones than mimic birds.

It’s going to get interesting when the conspiracy theory becomes reality. Imagine the future historians browsing the Reddit archives going like, ”they knew!!“

More likely that sensible mainstream journalists will laugh at people under Govt surveillance because they sound like the reddit conspiracy nuts from their youth...

What conspiracy? CIA had spy pigeons among other animals half a century ago, which is public info by now.[1]

They are very proud of it too.

> While many of the animal programs studied by CIA were never deployed operationally—or failed for a variety of technical, logistical, or behavioral reasons—collectively they demonstrate the incredible innovation and creative thinking that has come to characterize everything that our Directorate of Science and Technology does.

[1] https://www.cia.gov/stories/story/natural-spies-animals-in-e...

Every good conspiracy theory starts with a truth, I guess.

I had no idea about the CIA thing. I just always assumed the "birds aren't real" meme to be a way of showing how ridiculous the police state is going to become in the next decade or so as surveillance gets more and more weaponized against the people it was supposed to protect.

I always took "birds aren't real" to be an absurdist take on paranoia

Like the Chinese one?

https://interestingengineering.com/military/chinese-special-...

Military contractors have been producing teaser videos on the subject for maybe fifteen years now.

Makes you wonder what will come first:

- energy-efficient, long-lasting, mechanically optimized robotic "birds"

- good-enough understanding of the avian brain connectome & operation, such that all you need is a bunch of fine wires stuck in it, and a small CPU sending commands (local and remote operation, etc.)

https://www.reddit.com/r/BirdsArentReal/

It’s like the ultimate bio-inspired stealth tech.

Avoiding cheap surveillance technologies seems like a big deal. Although I assume once the government works out what you can do with it, it’ll become illegal pretty quickly. I assume this research will attract DOD grant funding pretty quickly. Students have to eat somehow.

Wheels need a reasonably flat surface to be efficient. Walking is more efficient than flying for short distances..

> reasonably flat

comparing to wheel size. one can use bigger light wheels. that would make landing on short runways possible. besides, wheeling is much easier than walking. two wheels balancing and rolling around is not a problem today. but.. without legs it's just an common airplane, nothing to talk about. the best of both? put small motorized wheels instead of flat platforms for feet.

2 more things that can break/go wrong/stop working resulting in mission failure.

1 working wheel is enough for balancing. they can be as simple as just a motor in rubber. it's more likely tail or wing will fail than both motors

BTW, here is how it works from Boston Dynamics, it can jump:

https://www.youtube.com/watch?v=LHJKGgwpWY8

Playing your song: https://www.donutlab.com/motor/

> the big thing was the jumping itself, which does not require complex bird anatomy necessarily

No, this is exactly the opposite. The jumping requires exactly this specific anatomy for so many reasons. It stores energy in the joints, it has a specific balance, the jumping works at multiple angles, etc, etc. You can’t do better than that for this specific purpose.

Maybe there’s a niche application we’re not considering where bird-like movement is crucial?

Naval versions of fighters can use "jump strut" [1]. For instance the Rafale M [2] [3]. I dislike weapons, but those planes are amazing.

[1] https://www.researchgate.net/publication/257410805_Effect_Of...

[2] https://en.wikipedia.org/wiki/Dassault_Rafale#Overview

[3] https://www.alachassebordel.com/post/20-secrets-about-naval-...

> I dislike weapons

A throwaway comment, but huh?

> Despite its name, RAVEN is approximately the size of a crow

This phrase first puzzled me, but after some googling I found out that in English "raven" is generally used for bigger crows. Until now I had thought that raven was just a more elegant-sounding synonym for crow. TIL...

EDIT: to my surprise, it's the same in my native German: the bigger ones are called "Raben", the smaller ones "Krähen". TIL²...

Here’s the thing…

Could this be viable on Mars? Having legs might support a bigger range of terrains than wheels while the flying mode requiring more resources might be used sparingly to overcome bigger elevation changes or to cover a higher distance quicker.

Tough adding legs instead if wheels might introduce balancng issues, the drone could be lowered further to ground level for the time of harsh weather conditions to increase the traction.

If your drone can land on a high spot and save energy by not flying, while using energy to use camera and radio communications, that would be really nice!

Also: the noise a drone makes, gives away it's presence.

Bonus points for being able to perch on a thin branch, wire etc.

https://www.silentflyer.tech/

I think I might be building one of these... This is insanely cool.

Is there info on how efficient this is compared to a regular drone? I suspect the boring regular drone with four propellers on each corner destroys this.

I love bio-inspired robotics. It’ll be interesting to see how these evolve. And the drone itself (for me do not know why) looks really cute.

Future warfare would be really fun. You would have to eliminate every single animal you find because it could be drone.

Yes, we must shoot down the flying bears.

Alright, we're getting there. Still feels like there's a very long way to go.

See also this week's IEEE Robot Friday for another uav with bird-inspired legs:

We’ve seen hybrid quadrotor bipeds before, but this one, which is imitating the hopping behavior of Jacana birds, is pretty cute. . . .What’s a Jacana bird, you ask? It’s these things, which surely must have the most extreme foot to body ratio of any bird

https://spectrum.ieee.org/video-friday-arms-on-vacuums

You talk like we already don't know that birds are now real, and are actualy goverment drones.

Ah yes, the bird-inspired ... nose propeller.

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