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Robotics Hardware

XRL Hexapod Robot Gets a Tail, Learns To Use It 52

New submitter toygeek writes "In an effort to give various robots more control during free-fall and navigation of severe obstacles, researchers have studied how agama lizards use their tails to retain or correct orientation during leaps and jumps. They've applied the research to both hexapod and wheeled robots, and the results are both astounding, and outstanding!"

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XRL Hexapod Robot Gets a Tail, Learns To Use It

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  • It could lead to an anti-gravity robot.

    • by techno-vampire ( 666512 ) on Monday July 30, 2012 @08:56PM (#40824411) Homepage
      Not only that, a cat uses its tail to turn over in mid-air so that even if you drop it with its feet pointing up it will land feet first as long as it has enough falling time to make the turn. I'm not sure, but I think I've heard of them getting turned in as little as 1.5 feet, but ICBW. Still it would be a great improvement over what they've got so far.
      • by Paul Fernhout ( 109597 ) on Monday July 30, 2012 @09:39PM (#40824595) Homepage

        I just watched the related videos, and it is impressive just what an up and down tail can do. But you're right that a tail that can move side-to-side, or that can curl or corkscrew can probably do even more to maintain a desired 3D orientation. No doubt that will be future directions for this work. So, in the real world, it seems like a common situation that you want to maintain the orientation of 90% of the mass of an object, and are willing to sacrifice the 3D orientation of 10% for a short time to do that (until the tail orientation can be reset at no body-orientation cost when the creature is on a surface again). Brilliant. These robot videos really show how amazing nature can be. I really appreciate tails in a way I never had before watching those videos. I especially found of interest video about a predecessor robot to this which includes video footage of the long-tailed lizard used as a prototype: []

      • Re: (Score:2, Insightful)

        by Anonymous Coward

        It depends on how the a cat falls but they can flip in less than a foot if needed.
        I've also seen my cat fall from much higher and not recover in time.

        I regularly test this one out, she's not to happy being held sometimes so we both screw this move up from time to time.

        It's not all tail either, she's using her entire body when she does it.

      • You forgot the toast...

      • Not only that, a cat uses its tail to turn over in mid-air ...

        False. Even a tailess cat lands feet first. Cats use their tails for balance. They turn over in mid-air by twisting their bodies... has nothing to do with their tail.

      • by mcgrew ( 92797 ) *

        That crossed my mind as well -- why study lizards when cats are so adept at landing right side up? If they'd studied cats, they'd know that the stronger the cat's tail, the better an athelete the cat is, so it stands to reason that the better designed the robot's tail, the better the robot will be at its job.

  • by pushing-robot ( 1037830 ) on Monday July 30, 2012 @08:44PM (#40824325)

    UC Berkeley researchers, please: Stop now. No good can come from this, and we all know it.

    We already have enough trouble getting laid, and yet you would put us on the path to anthropomorphic clydesdales?

  • by Lord_of_the_nerf ( 895604 ) on Monday July 30, 2012 @09:31PM (#40824545) the words, 'That tail is so adorable!'
  • by jcoy42 ( 412359 ) on Monday July 30, 2012 @09:42PM (#40824615) Homepage Journal

    They should have just tied a slice of buttered bread to it's back.

    • I got the impression it's not supposed to land on its back, so you'd want to tie the buttered bread to the underside (which is easier albeit perhaps less effective than a plate of spaghetti upside-down).
  • Imagine what this could do for toast.

  • Flywheel (Score:5, Informative)

    by labnet ( 457441 ) on Monday July 30, 2012 @10:41PM (#40824891)

    Wouldn't a flywheel be much more practical?

    -gets caught on stuff
    -can only go half a turn

    -can accelerate until the material limits of the fly wheel
    -can use the stored energy for recovery.
    -can be embedded inside the robot.
    -can act as a gyroscope to provide stability in other axes.

    • Re:Flywheel (Score:4, Informative)

      by billyswong ( 1858858 ) on Monday July 30, 2012 @11:42PM (#40825197)

      Flywheel is less efficient weight-wise. To re-balance a 8kg robot (or even heavier model later) falling upside down, how heavy / how fast must the flywheel be?

      Tail can be further improved by giving it more angles of freedom. We can also let it be able to coil up. Hard to beat tail.

    • Define practical; it doesn't get much simpler than a weight on a servo. In contrast, how much torque can you get from a small compact flywheel and how much is it going to cost? How quickly can you regeneratively brake it with decent energy recovery?

      (You might be interested in this control-moment gyro controlled ballbot [].)

      • Reaction wheels (or flywheels) and control-moment gyros work differently, even though they can both be used to create torque,

        Reaction wheels spin up (or spin down) the wheel to create torque - the axis of the wheel does not change. The tail in this robot is an unusual case of a reaction wheel - it's not actually a wheel, but is uses the same princple.

        CMGs [] use the gyroscopic effect you get from changing the axis of a spinning wheel to create torque. The rotation speed of the wheel is (usually) constant. They

  • by Animats ( 122034 ) on Tuesday July 31, 2012 @01:54AM (#40825695) Homepage

    Worked that out back in 1995. See this the "running on rough terrain video. [] Watch at 1:40.

    The next step, which the U. Penn people don't seem to have taken yet, is to solve this as a two-point boundary value problem. Then, instead of trying to maintain attitude during flight, you try to land at a specific time in a specific place with a specific attitude.

    Doing that is rocket science. Rocket science is about control of underactuated systems, where the control system has fewer actuators than there are degrees of freedom to be controlled. You want to reach a specified point at a specified time at a specified velocity in a specified attitude. All you have available is the ability to thrust in one direction and to change attitude slowly. But this problem is solveable and there are known solutions. Applying that to robots leads to gymnastics.

    The quadrotor people are already doing this kind of thing, but it hasn't been done much for legged machines yet.

  • by rizole ( 666389 ) <{rizole} {at} {}> on Tuesday July 31, 2012 @05:00AM (#40826343)
    I want a tail. A prehensile monkey tail. I'd prefer to grow my own but if robotics get the solution before genetics I'll take a prosthetic one.
  • I'm not a mechanical engineer, but I am a mathematician with a modicum of experience solving two-point boundary value problems, which are what you are up against when you have an energy budget and have fewer thrusters than degrees of freedom. Angular momentum (and the conservation thereof) is a much better approach, I would some Olympic gymnasts if you want to see some fine examples of human wetware doing this in real-time.
  • Since you are dealing with 3D space, you will need *4* points of awareness to keep the center of gravity in balance. You might think that 3 legs and one tail would be best, but then you have to deal with a disbalanced processing problem: triangulation in space, followed by an add-on to balance that. Better to deal with three 2-point axle balancing problems instead. (A:B, C:D, AB:CD).

The party adjourned to a hot tub, yes. Fully clothed, I might add. -- IBM employee, testifying in California State Supreme Court