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Omnidirectional treadmill

  1. Nov 8, 2008 #1
    So I've seen some of the omnidirectional treadmills on youtube, and they seem to work fine - but so many moving parts gives me the impression they won't be coming to the loungeroom any time soon.

    So I've been thinking of an alternative design, which no doubt others have considered, I just wanted to see what other musings were on the topic. It seems like it's nearly feasible, though I tried some basic tests and seems friction is far too high for it to work effectively.

    Say you have a spherical thick rubber bladder, reasonably elastic, maybe 10mm or more thick. You set up a short cylindrical base with a flat upper surface (the walking surface), and a kind of toroidal base - so base is hollow in middle, but still rounded on edges to minimise surface friction (final object would look a bit like a lid).

    This base is sealed inside the bladder and filled with lubricant, the idea being the rubber surface can be rotated easily about the base. Use omnidirectional casters to secure the base in place (so bladder can rotate while base remains steady). Then place a drive shaft wheel under the base, pushing it into the hollow region to give it greater traction. Wheel movement will make the entire surface orbit, the wheel orientation can be changed to modify the direction (using some kind of omniwheel design would be suitable as well).

    So does anyone think this kind of design is feasible with materials current science has available? For me it seems no matter how good your lubricant was, the friction would be too high to rotate the surface freely.

    Anyone else have thoughts on good way to create an omnidirectional treadmill, that doesn't have a tonne of moving parts?
     
  2. jcsd
  3. Nov 10, 2008 #2
    Stationary bicycle?
     
  4. Nov 10, 2008 #3

    DaveC426913

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    What is the benefit of an omnidirectional treadmill over a uni?
     
  5. Nov 10, 2008 #4
    so you can track a walker in a video game.
     
  6. Nov 10, 2008 #5

    DaveC426913

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    Doh.
    : Slaps forehead :
    I was thinking exercise / physical training. :blushing:
     
  7. Nov 10, 2008 #6
    what if instead of a treadmill, you just have the person get into a harness type thing (like the ones you put babies in where their feet can still touch the ground) and have them wear omnidirectional roller skates? It'd probably be easier to make, and if you had sensors in the harness that could traingulate and keep track of the skates positions it wouldn't be too much harder to figure out which way the person is walking..

    Or, maybe you could have the person get into a big *** plastic bubble that rests on a bed of spherical rollers... though they could have trouble breathing after a while, especially if they're running :D
     
  8. Nov 11, 2008 #7
    While I think you could get that to work quite well, it might feel somewhat awkard/unnatural. Just thinking the lack of friction on the skates would take some getting used to. Still, having the footwear somehow handle the movement (instead of a mobile base) might be an alternative.

    Funny you should mention that, one company has done pretty much what you have described. It's a giant cage, looks like an omnidirectional hamster wheel.

    Anyway yes an omnidirectional treadmill would be used for virtual reality simulation - they're coming out with some pretty good quality VR headsets these days, but immersion would be taken to another level if you can walk around the environment freely.
     
  9. Nov 11, 2008 #8
    ...but anything is going to feel unnatural and awkward. Walking or running on a treadmill doesn't feel natural. For it to feel remotely natural it would have to involve some sort of computerized system that anticipates your movements and adjusts the resistance where your feet land to how hard your muscles are pushing. And even then it wouldn't feel completely natural because you'll never have to overcome the inertia of your body.

    But for fun, say you've got the movement-anticipation sensing worked out. I would propose a more advanced version of Bigman's first suggestion with the roller skates. You would stand on a flat plate that in its normal state is nearly frictionless somehow. You wear boot that snugly grasp your feet somehow... maybe like ski boots but with thin and flexible normal-shoe soles so that you can feel the pressure of the floor properly.

    Ringed around your feet, at a distance of maybe a meter or so, are 12 piston / strut things kind of like the "linear motors" from a Bose suspension. These are telescoping rods that can move inward or outward fluidly and their movement is controlled by the computer. The ends of the rods attach to the ski boot things on your feet. So this contraption can basically push your feet back and forth in any direction, based upon where the computer senses that you want to step.

    And finally, coating the surface you're standing on and the bottom of the soles of the boots is a magnetorheological fluid, a substance that the computer will be able to control to increase and decrease the amount of friction between each of your feet and the surface so that stepping feels more correct.

    ―​

    But wait, I've got a much better idea. Forget treadmills completely.

    Take an empty building enclosing a space about half the size of a football field. Countersunk into the floor and completely covering it are an array of disks about a half-meter in diameter or so. The computer can control a motor that can rotate each disk in either direction precisely.

    You can walk around the floor of the building freely, but the computer has some sensing mechanism to tell where you are and precisely where your feet are going to fall with each step and when your foot has made contact with the floor. And what it does with that information is, as each step lands but before you've shifted your weight on to it the computer can rotate the disk you're stepping onto by a small amount, just enough to alter the direction of the step you take by two or three degrees.

    So what it's doing is that you might think you're walking in a straight line but the computer is actually steering you in a circle. Wherever you may walk in the virtual world, the computer adjusts your course so that you stay approximately in the middle of the floor.

    Voilá! Not only will it be a more realistic experience because you'll really be shifting your weight and overcoming inertia, but it's entirely possible with current off-the-shelf components. And multiple people could probably use the same floor at the same time, with the computer figuring out how to prevent them from crashing into each other.

    Okay, well, I'm going to move to Dubai, buy a few acres of desert, and build thirty of these for all the fabulously rich dilettantes there to patronize, and become a millionaire. Bye! Have fun with your rickety treadmill contraptions, mwahaha!
     
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