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Like A Cat, New Robot Lands On Its Feet

Posted by timothy on from the pfffthhpt dept.

eckenheimer writes "Students at the Physics Department at Drury University have developed a robot that uses motions and contortions of its body to orient itself in zero gravity. According to the project site, 'If you've ever seen a cat land on its feet after falling while upside down then you've seen the idea behind our project.' The effort is a proposal for the NASA Reduced Gravity Student Flight Opportunities Program."

57 of 263 comments (clear)

  1. Like a...? by SIGALRM · · Score: 5, Funny
    If you've ever seen a cat land on its feet after falling while upside down
    I'm looking forward to their "like-a-dog" model: word on the street is, licks its own ass.

    Now that's using "motions and contortions".
    --
    Sigs cause cancer.
    1. Re:Like a...? by grunt107 · · Score: 5, Funny

      I would merge the cat/dog projects.

      All the loyalty of a cat with the cleanliness of a dog

    2. Re:Like a...? by Rei · · Score: 4, Interesting

      There are serious applications for this. Namely, being able to orient yourself in space without using propellant is a very valuable ability.

      The real surprise is that this is nothing radical; I really don't get why it deserves a press release. Probes have been using momentum wheels, for example, to do the same thing for decades. What is the big advantage of this over, say, a small set of momentum wheels? All I can really say about it is that it's more complex, and seems more likely to wear and have part failures.

      --
      Very well; let this abomination unto the Lord begin!
    3. Re:Like a...? by drtomaso · · Score: 4, Funny

      Some other "cat-like" behavior they forgot to mention:

      • Robot sleeps 16 hours a day
      • Robot begs for food when scientists are seated around the dinner table
      • Ate robo-bird
    4. Re:Like a...? by pete-classic · · Score: 2, Funny

      I would guess that their next robot will be based on buttered toast, and have the opposite capablities.

      -Peter

  2. Now all we need is buttered bread by Anonymous Coward · · Score: 5, Funny

    ...to stick on its back and we'll have an antigravity engine.

  3. Where's the beef? by Anonymous Coward · · Score: 2, Insightful

    I see no completed robot, no performance data or even a simulation of how it will perform in the real world. Just a REAAALLY bad web site (No page navigation? Come on!) and some digital photos of these kids and their drawings. The dates in the pages and some photos are from fall of 2003. If these were college seniors (as it says in the "meet the team" section) at the time they have already graduated by now, and abandoned these pages.

    How is this newsworthy?

    1. Re:Where's the beef? by enforcer999 · · Score: 5, Informative

      Here you go. It is not a very "pretty" robot but it could have its uses.

    2. Re:Where's the beef? by MooseByte · · Score: 2, Funny


      Couldn't they just build a robotic sphere covered with dozens of feet?

      Young engineers these days... always making everything so dang hard.

    3. Re:Where's the beef? by Animats · · Score: 2, Interesting
      That's not too impressive. They're not even close to active stabilization. All they're doing is rotating a weight that also moves in and out from the axis of rotation to change the moment of inertia. This gets them a little net angular motion. Big deal. I've seen wind-up toys do that.

      Since it's a one-axis device, there's no need to test it in a zero-G environment. Hanging it from a string would work equally well.

      There's useful work to be done on three-axis stablization algorithms, but this isn't it.

      Even NASA didn't go for this one.

    4. Re:Where's the beef? by Trackster · · Score: 2, Insightful
      I'm afraid they made a mistake in the design. Looking at the video, you can see the robot never really changes its orientation to the camera, just ratates back and forth.

      The mistake they made is that the robot needs two of those variable moment of inertia devices (the thing that looks like an umbrella skeleton on top). The cat has two pairs of feet whose distance from its center of gravity it varies as it spins the other pair.

  4. Butter side up? by decipher_saint · · Score: 2, Funny

    Can we apply some kind of techno-butter to one side to see if the robot can stay in a constant state of airborne suspension?

    --
    crazy dynamite monkey
  5. Cats landing on their feet by thedogcow · · Score: 4, Informative

    This was explained to me in my physics for engineers class...

    Cats reposition themselves to land on their feet because they can sense the change in velocity (dv/dt = acceleration). My professor stated this only works for small height values (less than 20 ft), otherwise, the acceleration due to gravity might result in an unpleasant aftermath.

    --
    Yes! I listen to NYC Speedcore and do math at 3AM. I suggest you try it too.
    1. Re:Cats landing on their feet by Kenja · · Score: 2, Informative

      I recall reading a bit about how after the 10th floor, cats cat spread thir legs and "glide" to slow down enough to survive. Statistics show that there are more feline fatalities between floors 3-10 then there are after 10.

      --

      "Have you ever thought about just turning off the TV, sitting down with your kids, and hitting them?"
    2. Re:Cats landing on their feet by forrestt · · Score: 2, Insightful

      Statistics show that there are more feline fatalities between floors 3-10 then[sic] there are after 10.

      I bet statistics also show that there are more buildings with top floors between 3-10 than there are buildings > 10. But what do I know?

    3. Re:Cats landing on their feet by Rob+Carr · · Score: 5, Interesting
      Cats reposition themselves to land on their feet because they can sense the change in velocity (dv/dt = acceleration). My professor stated this only works for small height values (less than 20 ft), otherwise, the acceleration due to gravity might result in an unpleasant aftermath.

      Actually, it's the short falls that tend to kill cats. Cats (like skydivers) can assume a position that reduces the terminal velocity and presents the greatest surface area for impact, reducing the force per unit of surface area. It takes a while to rotate and get into the position, so if the fall is too short, the cat will land in an awkward position and is far more likely to die.

      This is not to say that the cats that fell from a great height were uninjured - just that they were more likely to have non-fatal injuries.

      --
      This sig seemed like a good idea at the time....
    4. Re:Cats landing on their feet by captnjameskirk · · Score: 5, Funny

      the acceleration due to gravity might result in an unpleasant aftermath

      Actually, it's the deceleration when meeting the ground that is usually the culprit.

    5. Re:Cats landing on their feet by no+longer+myself · · Score: 5, Funny
      I'm just having this morbidly funny image of people throwing cats out windows as part of a government study to test that "statistic":

      "Damn, Bob... Did you see that? He might have made it if that cab driver hadn't run over him."

      "Yeah, Pete. Let's take this tabby up to the 23rd floor. Oh, by the way, did you hear they're working on a robot that mimics this sort of behavior."

      "I think I did read something about that, Bob, but tossing an expensive piece of hardware out the window just isn't as satisfying."

      "You've never owned a Mac, have you, Pete?"

    6. Re:Cats landing on their feet by eunos94 · · Score: 5, Insightful
      I call bullshit. This study has one HUGE flaw in it. I remember in college when this study was brought up in a statistics class. The flaw can be summed up in one clear thought.

      "No one brings a clearly dead cat to the vet."

      If the fall is high enough, the odds of living decrease and therefore no cats are brought to the vet unless they miraculously survived. The study self-selects for those cases. Ergo...bad stats. Grrr...the bane of my social sci existence.

    7. Re:Cats landing on their feet by Rob+Carr · · Score: 2, Insightful
      " I remember in college when this study was brought up in a statistics class. No one brings a clearly dead cat to the vet."

      Then your statistics class was flawed.

      I'll grant that people are less likely to bring a dead cat to the vet. But that simply won't explain the data.

      Trauma produces a spectrum of results, from "uninjured" to "dead." The curve is basically bell shaped, but as the forces involved increase the curve will skew toward "dead."

      Let's divide the result of the cat impact up into 6 groups:

      1. uninjured
      2. minor injury
      3. moderate injury
      4. severe but survivable injury
      5. eventually fatal
      6. immediately fatal

      We can assume that most dead cats and most uninjured cats are not brought to the vet. Still, the shape of the curve we see (i.e. brought into the vet) tells us about the shape of the curve we can't see. For short falls, there are many more of "eventually fatal" cases and far fewer (in proportion) of the others we see. In contrast, for the falls from a greater height, cats were far less likely to die if they made it to the vet at all. This implies that either a) greater falls give cats a chance to impliment a survival strategy or b) greater falls are less likely to kill the cat if the cat does not die instantly. "B" would be truly bizarre.

      What we would expect to see based on the physics backs up the study as well. Cats have been repeatedly observed to go into a "drag" mode if given enough distance to fall. Terminal velocity for the "drag" mode would be far less than the terminal velocity of the non-drag mode. Cats entering "drag mode" have been observed to slow down - just as a parachutist going from "tumble" to "drag" mode slows down. This means that the cats slow down - if they don't get the chance to slow down, then they will be going faster than if they have enough time to fall. The "drag" position also allows the cat the most surface area to impact on. The force per unit of surface area is far less, whereas a cat that lands on it's feet has a far, far greater force per unit of surface area - something that's more likely to produce massive trauma damage.

      And there's the final clue. Above a certain height, there's no significant change in the type and severity of trauma seen. Once the cat hits terminal velocity, additional altitude doesn't change outcome.

      --
      This sig seemed like a good idea at the time....
    8. Re:Cats landing on their feet by rupert2000 · · Score: 2, Insightful

      I'd have to disagree...

      I remember experimenting with my cat growing up to see how short a height it could recover in over a sofa cushion.

      I remember being pretty amazed at how short a distance it could twist around in. I think it was definitely under a foot in height that it could land on its feet in. Anything less it could still manage to land on its side ad least.

      I don't think that a fall of about 8 inches could be considered life threating for a cat.

    9. Re:Cats landing on their feet by eunos94 · · Score: 2, Insightful
      To start with, a study of 115 cats is far from quality data. But given the data, let's take a look a little closer.

      First, there is no bell curve in this study. They reported "Three of the cats were dead upon arrival and 8 more died in the next twenty-four hours, leaving 104 living cats or about 90%". All we know is that 104 of the 115 cats survived. There is no data as to the amount of trauma they incurred, so dividing them into 6 groups is pointless.

      Secondly, we don't know how many cats are falling from places in the first place. The data could be supported if 10000 cats are falling and 104 survived. Doesn't sound good to me.

      Alternate theories abound and are not disproven either. If there was an intervening circumstances (trees, awnings, boxes, flags, etc), that would allow a small % to decrease speed some. Or maybe some cats are less prone to die. Maybe between 5-10% are very light weight cats. There is no data given to a margin of error, so 5-10% could be completely realistic when no population size is known.

      If your cat fell from a 5 story building and had a 10% chance of living and you brought the barely living cat in, we now have a cat in the study, but the cat has a much better than 10% chance of living because the cat already wasn't splattered.

      Keep doing that for higher and higher heights. A 5% chance of living and then bring the living cat in. The cat initially had a 1 in 20 chance, but now that it's at the clinic it's already lived, so the odds are a heck of a lot better than that. Everytime a cat survives from a higher and higher fall, the odds in the clinic keep getting better and better because the surviving cats are part of a smaller and smaller group of "cats that survive falls".

    10. Re:Cats landing on their feet by Anonymous Coward · · Score: 2, Funny

      Ok, so lets conduct an experiment: throw 500 cats from an airplane, say 3,000 ft. above ground level. This way we are certain terminal velocity is attained. Record the bell-curve survival rate. Those on the ground doing the counting, wear a helmet.

    11. Re:Cats landing on their feet by Suidae · · Score: 3, Funny

      I wonder if, given an inverted starting attitude, there is a certain height at which the fall would be less dangerious if it were either higher or lower.

      Above this height the cat would have had time to attain a fully non-inverted attitude and so would better cope with higher impact forces. Below this height and although the cat would still be in a bad attitude, the velocity attained would be sufficently small that injury would be less likely.

      This experiment would require a standard cat, as I would expect that small, fluffy, long-haired cats with tails would have a lower terminal velocity than enormously fat, bald, tailless cats. Likewise, previously fat cats who had lost substantial amounts of weight would have enough loose, baggy skin might have an advantage above certain velocities, where their excess skin would flap about in the wind, helping keep the velocity down. By stretching out their little arms and legs they might even be able to form little parachutes or planes, with which they could glide safely to the ground, much like a flying squirrel. But bigger. And uglyier.

  6. I am not a physicist by kilocomp · · Score: 2, Insightful

    But their project is about " a robot that uses motions and contortions of its body to orient itself in zero gravity" but they describe it using a situation caused by gravity "If you've ever seen a cat land on its feet after falling while upside down then you've seen the idea behind our project."

    1. Re:I am not a physicist by hopews · · Score: 2, Interesting

      When a cat is falling ( or while anything is falling for that matter ) it is in free fall until there is significant drag from its motion through the air. Free fall is effectively a zero gravity state.

      NASA used planes in a dive to simulate zero gravity for astronaught training.

  7. Comment removed by account_deleted · · Score: 3, Funny

    Comment removed based on user account deletion

  8. Bah! I can do that too.. by myrdred · · Score: 2, Funny

    Just make the feet of the robot really, really heavy. Heavier than the rest of its body, then it will always land on its feet!

  9. Have to wonder how they did their research... by foidulus · · Score: 4, Funny

    I can just imagine the papers you would have to fill out
    Experiment: "Drop cats repeatedly, observe results for use in robotics..."
    See how well PETA would love that one!

    1. Re:Have to wonder how they did their research... by jfengel · · Score: 3, Informative

      That research was already done. Complete with pictures of dropped cats. These guys are just taking advantage of the previous research.

  10. Anyone could do this... by SlapAyoda · · Score: 2, Funny

    Just attach a printed list of all the Internet Explorer security holes in the past few months to any existing robot's feet, and the resulting weight should be enough to reproduce this cat-like ability.

    --
    # wrote sig.txt, 23 lines, 31337 chars
  11. is it a better mousetrap too? by peter303 · · Score: 2, Funny

    As Ralph Waldo Emerson said "if you build a better mousetrap, the world will beat a path to your door".

    1. Re:is it a better mousetrap too? by mopslik · · Score: 2, Funny

      Or in /.'s case:

      "Build a better mousetrap and the world will not just beat a path to your door but will overwhelm your server."

      Not sure who said that one.

    2. Re:is it a better mousetrap too? by Neil+Blender · · Score: 2, Funny

      Or in /.'s case:

      "Build a better mousetrap and the world will not just beat a path to your door but will overwhelm your server."

      Don' forget "and bitch about the patent."

  12. How cool is that? by senzafine · · Score: 2, Interesting

    That sounds like a fun project to work on. I can think of all sorts of uses for something like this. We can ensure that all olympic divers enter the water perfectly perpendicular to the surface. likewise gymnasts doing the vault will always land on their feet. Throwing spirals with a football could be automagic. Ok...nothing lifechanging there...but I'm sure someone will think of something.

    --
    Better than Flickr - Manage, Share, Archive
  13. I wonder... by Unnngh! · · Score: 4, Interesting

    ...if the robot can survive terminal velocity falls like cats. Cats falling from very high heights (i.e. skyscrapers) tend to survive the fall better than those falling from lower elevations.

    1. Re:I wonder... by h00dLuM · · Score: 2, Insightful
      I've seen a few of these postings, and have to say something.

      I'm no scientist, all I know is that my cat fell from my apartment on the 17th floor and was really fucking dead after that. Where she landed there was no big mess, no blood coming out of her mouth, really pretty clean so I guess her landing was perfect. But at that height it didn't matter.

      Obviously my one cat "study" isn't the scientific method, but if your average living mammal falls from 17 floors up, they will mostly fucking die and skyscrapers are even higher. I've smacked mice and rats off roofs about 50 feet high with a baseball bat and they survived and limped away, but I don't know about cats falling from skyscrapers.

  14. Legs? by Wizzy+Wig · · Score: 2, Insightful

    Why would a robot (or human for that matter) designed for zero g require feet? Go back to the drawing board... replace those feet with a couple more arms.

  15. Another new breakthrough by mseeger · · Score: 2, Funny
    DPA: As professor Fallsonhisface of the chair for human mechanics anounced today, he delivered another breakthrough in robotics. By using a new technology dubbed "artifical clumsiness" he created a robot that appears more humanlike than every other machine today. He stated that "... Most people are scared to death by machines acting perfectly. They will only accept a robot in their daily life if those manage to make mistakes. People want to feel supperior."

    He was confident that the first prototype would convince the public once it has been reassembled again.

    Regards, Martin

  16. How does it all fit together? by Sean80 · · Score: 2
    We tend to see a fair number of these postings coming through here. What I'm trying to get my head around is how all of these fit together.

    It would appear that this posting fits in with a robot's ability to manage its own body. I guess other components are intelligence, being able to sense the environment, being self-sufficient, and so forth.

    Does anybody have any good thoughts on how everything is fitting together, and how far we are, in total, from a robot that can be truly useful, say, as a human companion, or for other purposes?

  17. Story Musgrave by Ferante · · Score: 5, Interesting

    In grad school one of my physics professors wrote a paper on orienting onself in zero g with no net angular momentum. One student was just convinced it was impossible. Soon thereafter we were visted by Story Musgrave (one of astronauts who fixed Hubble) and the professor told him of the paper. Story immediately sat down on a swivel chair and demonstrated the motion necessary to turn in zero g without grabbing on to anything. It's interesting how a concept that caused some interesting debates among the students suddenly became obvious when it was directly demonstrated.

    1. Re:Story Musgrave by roman_mir · · Score: 2, Informative

      Sit calmly in a swivel chair, slowly extend your legs, then extend your arms to one side, say to the left, move your arms from that position to the other side of your legs at the same time pull your arms close to your body, at the same time push your pelvis in opposite direction to your arms.
      There you have it, net angular momentum is 0 but you are still rotating.

      --
      You can't handle the truth.
  18. Zero G? by Shabbs · · Score: 4, Funny

    Just curious... how does something "fall" in zero g? Doesn't falling imply gravity?

    What would a cat do in Zero G? Would it continously try to adjust itself.

    Now THAT would be funny to see.

    Cats in spce... the next fontier.

    --
    Mark
  19. Finally perpetual motion! by Prince+Vegeta+SSJ4 · · Score: 3, Funny

    Like A Cat, New Robot Lands On Its Feet

    Now they will finally be ble to create a perpetual motion machine, which not only works, but is environmentally and feline friendly as well.

    PETA had this to say:

    • the desperately needed, perpetual motion machine can now be achieved, that does not conflict with our interests, The long controversial Buttered Cat array is now available without the cats, it is indeed a great day for humanity
  20. Re:doesnt work by Lord+Bitman · · Score: 5, Insightful

    do the math you twit. Perpetual motion is still impossible because toast doesnt care what side it lands on when it's already got fur all over it.

    --
    -- 'The' Lord and Master Bitman On High, Master Of All
  21. What's A Robot? by blinder · · Score: 2, Funny
    [voice mode="homestarrunner_1936"]what's a robit?[/voice]
    --
    sad robot making broken music
  22. Perhaps... by GersonK · · Score: 2, Interesting

    ...they should add the technology to this robot?

  23. RGSFOP by ghack · · Score: 5, Informative

    As an individual who has participated in the RGSFOP program, I have seen a number of novel experiments, but this particular experiment is a retread that has been done many, many times. Last March, for example, Washington-St. Louis did a very interesting experiment involving zero-gravity orientation of a space vehicle. The typical RGSFOP experiment fails, however, although my University did experience a success this year.

    A list of active RGSFOP teams

  24. The real question is..... by cardshark2001 · · Score: 3, Funny
    Have you ever seen a cat not land on its feet?

    I've seen it. I might have had a little something to do with it. They sure are twisty little b@574d5, I'll tell you that.

    --
    WWJD? JWRTFA!
  25. Re:Air pressure by Anonymous Coward · · Score: 2, Informative

    The GYRE robot, which flew last year, did just that. And hopefully will do so again.

  26. Please name the robot Coriolis by jazzbotley · · Score: 2, Funny

    Not so much a formal study but a fun paper to read: On the Directional Correlation of Axial Rotation in Inverted Felines and Planetary Spin: Coriolis Revisited

    The author also happens to be a Computer Science professor in data networks. Quite a dry sense of humor -- his classes are a lot of fun!

    Mandatory Disclaimer : yes, I'm a starving grad student of his, and yes, I'm pulling for a graduation date this decade!

  27. Absolute crock of shit by SuperBanana · · Score: 2, Informative
    Cats falling from very high heights (i.e. skyscrapers) tend to survive the fall better than those falling from lower elevations.

    Um- no. Every bone in their body breaks and their internal organs are crushed, just like a human. The "paper" you cite is an absolute crock of shit- they have TWO datapoints, and among other things, the data-fit is so poor it implies 100% survival rates above 8 stories for cats! BullSHIT! Nevermind that they consider "skyscraper" to be "under 7 stories", when most people consider a skyscraper to be at least 50 or much more.

    Cats DO survive a two or three story fall(which is nowhere NEAR their terminal velocity) better than they will survive a one story fall, purely because they have plenty of time to orient themselves and extend their legs for full cushioning of the fall. If they don't have time to orient themselves, they often don't get their body fully aligned and it's a roll of the dice between bone strength and impact velocity.

    --
    Please help metamoderate.
    1. Re:Absolute crock of shit by lommer · · Score: 2, Interesting

      No actually, the paper he cited is not the only research that has been done on this - I distincly remember reading an article about this 3 or 4 years ago, and a radio program mentioning it a while back too. I didn't read the paper he pointed to, but the reason it works is because not only do the cats orient themselves properly, they also splay out their legs and stretch the skin out, creating a parachute-like effect which drastically reduces their terminal velocity. Cats falling from 5 stories have plenty of time to orient themselves, but not enough to get this parachute thing going and slow themselves down (i.e. they're falling at the terminal velocity of a bunched up cat, not a spread out one). Also, you seem incredulous that cats falling from over 8 stories have a 100% survival rate. Remarkably, in reality it IS almost this high, certainly >90%.

  28. Re:doesnt work by Anonymous Coward · · Score: 2, Insightful

    I like that the rebuttal has no scientific value but is still rated +5 Insightful. Nothing about thermodynamics, just the supposed emotions of toasted bread.

    You rejected a perfectly valid and testable hypothesis without citing any expermiental results. Who's post had no scientific value?

  29. Already in use by cjameshuff · · Score: 2, Informative

    As far as I can tell, this is basically an overly complex version of a momentum wheel...basically, a massive, low-speed flywheel. Spin it one way, the surrounding structure spins the opposite direction...stop the momentum wheel, and the entire structure stops spinning. That is, angular momentum for the entire structure is conserved.

    The Hubble telescope uses momentum wheels for very precise aiming without requiring propellant and complex, failure-prone, and mirror-dirtying thrusters. These people are trying too hard...the basic idea is just a massive wheel attached to an electric motor.

  30. Re:doesnt work by God!+Awful+2 · · Score: 2, Insightful

    I like that the rebuttal has no scientific value but is still rated +5 Insightful. Nothing about thermodynamics, just the supposed emotions of toasted bread.
    A joke theory cannot be rebutted by a scientific response. A joke theory can only be refuted by a better joke.

    -a

    --
    /. users can't
  31. Cat Anatomy by chadjg · · Score: 2, Interesting

    I've dissected a cat. It was pretty much a standard short haired cat. I think it must have been a stray alley cat, but not one of the bright ones that was smart enough to run like hell when the cat-snatchers came.

    Anyway, Once you see a cat without it's skin, the reason that cats can take falls becomes apparent. the only really massive structure in a cat is the legs/shoulderblade/pectorals structure. The shoulder blades on our cat were huge and had an endless number of muscle attachments. The shoulder blades are hooked on to the back but the connections are relatively loose and sloppy and the spine is basically like a slinky. The legs on our cat had a 5+ inches of travel. If you get a chance, pick the cat up by holding it with one hand under it's ribcage. Use the other hand to work the front legs up and down to see the massive travel and check out the way all the muscles that insert into the shoulder blade take up the shock. Giving the cat a tracheotomy and watching the lungs inflate and deflate is a lot of fun too.

    The hind quarters of the cat weren't really much, but it was as it was a really skinny alley cat there wasn't much weight for the back legs to handle. The above poster's postulated "enormously fat, bald, tailless" cat would probably shoot it's guts out all over the place on impact, but a normal cat might have a chance. Also a long tail might be handy for balance and steering on the way down, but I don't know.

    Take A&P if you ever get a chance. It's a lot of fun. But try not to get hooked up with idiot lab partners that only enjoyed dissecting the cat's nuts. That freaked me out a bit. Also, don't wear your good shirt to a lab session.

    --
    Why do I have this? I don't smoke.