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Robotics Transportation Technology Hardware Science

Novel Drive Wheel System Based On Spinning Sphere 104

Posted by timothy
from the spin-do-not-sit dept.
An anonymous reader writes "A Bradley University student has built a mobile robot that uses a hemispherical omnidirectional gimbaled, or HOG, drive wheel. It consists of a black rubber hemisphere that rotates like a spinning top, with servos that can tilt it left and right and forwards and backwards. The HOG system delivers an amount of torque directly proportional to the tilt of the hemisphere, allowing the robot to move incredibly fast nearly instantaneously."
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Novel Drive Wheel System Based On Spinning Sphere

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  • by MichaelSmith (789609) on Saturday July 09, 2011 @12:48AM (#36702640) Homepage Journal

    How about making a robot with four legs. The foot on the bottom of each leg would be a wheel like this. Servos which control the attitude of the legs would also control the direction the wheel operates in.

  • My biggest concern is how much control you have over the accuracy and precision. The friction between the power and pavement surfaces is dependent on how much that wheel is worn down. While driving the response you get as the wheel ages will change.
    • by NFN_NLN (633283)

      The friction between the power and pavement surfaces is dependent on how much that wheel is worn down. While driving the response you get as the wheel ages will change.

      Just like a traditional wheel!

      • by Jstlook (1193309)
        Well, yes and no. The difference is in a traditional wheel as you change speed that response doesn't change. In this system, the feedback you get will be dependent on the speed you're going. In a traditional wheel as the response changes (i.e. normal tire wear) there is really no appreciable change in steering or friction.

        The added issue is that your velocity *and* direction are dependent on where the tire contacts the driving surface. That really isn't an issue with a flat surface, but I don't typica
        • by bar-agent (698856)

          The difference is in a traditional wheel as you change speed that response doesn't change. In this system, the feedback you get will be dependent on the speed you're going. In a traditional wheel as the response changes (i.e. normal tire wear) there is really no appreciable change in steering or friction.

          The added issue is that your velocity *and* direction are dependent on where the tire contacts the driving surface. That really isn't an issue with a flat surface, but I don't typically drive on a dried des

          • by Jstlook (1193309)
            It's true, he needed none of that. First off, he used new wheels, which have no appreciable wear. Second, he certainly wasn't precision driving, which is where it would be critical.

            It's a prototype and it's downright awesome, but in terms of useful application, I'm just skeptical. The technology is similar to what you'll find in a Constant Variable Transmission (CVT), which has the added benefit of not having to contact an uneven surface. That means even wear throughout the lifetime of the apparatus,
        • by Renraku (518261) on Saturday July 09, 2011 @03:13AM (#36703014) Homepage

          Actually, I think this would be good for robots as they could adjust their parameters to counteract the bumps and stuff really quickly. Maybe a drive-by-wire system on a car where the computer does all the hard stuff and you just point the car where you want it to go.

          I could really see this being used in high speed robotics applications, imagine a ground-based sentry drone with this screaming down the road.

    • by nukenerd (172703) on Saturday July 09, 2011 @04:59AM (#36703264)
      I don't get all this worry about accuracy and precision. Wheel/tyre wear and surface undulations only matter if you need to position this robot by dead reckoning. Dead reckoning is a bad idea anyway except in machine tool or laboratory applications.

      Get real. This type of drive system would be for applications like vacuuming floors and moving stuff in warehouses. Its positioning would be determined by external feedback, like lines on the floor in a warehouse or ultrasonic echoes from walls. Other factors would be irrelevant to positioning.

      As for the guys worrying about loss of contact and friction (someone raised "omni-wheel" designs, with wheels composed of little wheels arranged around a big wheel) what is the problem? In TFA' photo I see a three wheeler (one HOG wheel and two conventional idlers - though it could be developed to three HOG wheels only). How can a three-wheeler lose tyre contact ?
  • by Animats (122034) on Saturday July 09, 2011 @12:59AM (#36702670) Homepage

    It's a cute idea. It assumes a single point of contact with the ground, and thus requires a flat, hard floor. This is limiting.

    The various "omni-wheel" designs, with wheels composed of little wheels arranged around a big wheel, have a similar problem. The size of the little wheels, not the big one, determines the terrain-handling limits of the vehicle.

    1980s robots tried to do everything by wheel odometry. Back then, most of the software was too dumb to plan moves given steering limitations, so omnidirectional drives were popular. Robots got a lot better when people stopped building robots with complex wheels and no suspension, and went to more ordinary wheels with off-road type suspensions.

    • by Interoperable (1651953) on Saturday July 09, 2011 @01:25AM (#36702740)

      Oh /., why must you be so negative? It doesn't have to be useful for every application in robotics to be extremely awesome.

      It only requires one motor rotating at a constant velocity and two actuators; that's hardly a complex wheel. The extreme simplicity should make it useful in a number of applications and hobbyist designs. It will, however, probably leave little rubber smudge marks on your floor.

      • by cgenman (325138)

        I'm guessing this would be perfect for certain small robot applications, where traditional multi-wheel designs bump into production limitations. Also, I wouldn't be surprised to see robot vacuum cleaners sporting these for durability and multi-directionality reasons.

    • by NFN_NLN (633283) on Saturday July 09, 2011 @01:43AM (#36702786)

      It's a cute idea. It assumes a single point of contact with the ground, and thus requires a flat, hard floor. This is limiting.

      You could add as many points of contact as you like as long as they are synchronized. Plus, I hear hill billies can slap chains on them for better traction in the mud.

      • But against a non-hard surface, the surface would deform. At that point you have coriolis problems which would be hard on the drive. It'd still work, but it'd draw more power and wear the wheel down much faster, leaving rubbery marks on the floor.
        • You do realize that this has very similar contact characteristics to motorcycle tires, right? And they still work, both on pavement and dirt.

          • I didn't say it wouldn't work. I said it would work, but soft surfaces would wear the ball out faster than hard surfaces.
    • by Anonymous Coward

      i agree that the floor has to be hard to be really useful. but flat... no. i don't think so.

      you could give every wheel individually a way to check its angle compared to the floor. i mean, sure, this is a small robot build here, but if you gonna make it bigger, some extra AI probably wont be hard to add somewhere.

      • What about the wheels on the vehicles in Snow Crash that where composed of many spokes sticking out that automatically adjusted to fit the terrain ahead? They where called Smart-wheels [wikipedia.org] and they provided good traction at high-speed. I am not sure if this is possible yet, but would this work any better, assuming the spokes could be strong enough to support the vehicle and its rider.

        • assuming the spokes could be strong enough to support the vehicle and its rider.

          Telescoping tubes work a lot better in cartoons than in real life.

          I have seen one robot with a deforming wheel design [galileomobility.com] which transitions from a wheel to a flat tracked drive. Their slogan is "wheels when possible, tracks when necessary.") It was fast, agile [youtube.com], showed up once at one trade show, and hasn't been seen much since. Nice mechanical engineering.

    • by nukenerd (172703)
      I fail to see why a single point of contact with the ground requires a flat hard floor. [Actually, the photo in TFA shows three]. You know, take a vertical line through the centre of this hemisphere and it is bound to intersect with any surface whatever, unless they are parallel.
      • by SmallFurryCreature (593017) on Saturday July 09, 2011 @05:28AM (#36703332) Journal

        Spinning top, you ever played with these toys? What happened to them when they hit a curb like a book or something? Right, they bounce off. Why? Because all of sudden it gains traction with what can be thought of as a wheel.

        This ball wheel works as an infinite gear because by tilting it, the controller decides exactly how large a wheel (a ball is an infinite number of circles/wheels, each a bit smaller/larger then its neighbour, stacked on top of each other) contacts the floor. If the ball is spinning direction is parallel to the floor (if the ball doesn't deform) it wouldn't move because there is no forward motion. Tilt it and you are essentially making contact with an ever larger wheel. If the RPM remains the same, the larger the wheel the greater distance must be travelled. That it works is clear and predictable. It makes perfect sense.

        But a bump on the road would suddenly cause a far greater wheel to make contact, greater wheel means greater speed and BAM, you got a difficult to control vehicle.

        This thing doesn't just need a flat surface, it must also avoid any curbs. And what if it hits a crack in the surface, what if its gets grip on its on opposite sides of the spinning ball?

        Doesn't mean this won't have its uses but they will be limited.

        • by nukenerd (172703) on Saturday July 09, 2011 @07:25AM (#36703670)
          Yes, I understand the physics, but I was really countering some guys here who seem to think the wheel contact requires laboratory precision and are worrying about slight wear (needing computer compensation!!) and loss of contact (how???).

          I agree this drive system is never going to be an off-roader. Also, many posters here seem to be floating the idea of it being used for cars - forget it. But as I have said in aother post here, the ideal use for this drive is fork-lift truck type applications, where tight manoevering is required, and, incidentally, the floor is flat.

          But I don't think it will be as sensitive to undulations and kerbs as you and others seem to think. Most "bumps" in the floor/road are actually at quite small angles unless they are actual holes with rims. Also, a spinning top reacts violently (eg shoots across the room) when it hits the wall because its whole mass is spinning, so it has a lot of rotational momentum to be converted into linear momentum. However, this HOG vehicle has only a small proportion of its mass spinning, so contact with a kerb will probably just result in a nasty jolt and some rubber left behind. For warehouse use, just put guards around the wheels (as the prototype has).

          You are worried about cracks?! I think we are at cross purposes about the scale of this thing. I assume that the prototype is a model, but even then I do not know its scale. For real world use (eg the warehouse vehicle) I envisage HOG wheels being hemisperes of about 400mm diameter. You would have to find an extremely run-down warehouse to have cracks in the floor that big!
        • If radar or some other surface-mapping technique was added to detect severe surface irregularities, the drive wheel could be lifted away from the surface at the moment the irregularity was traversed. The drive wheel could be placed in the center of the vehicle and be surrounded by "support wheels" for stability. There could also be two drive wheels, one smooth for tarmac and one studded/spiked for off-road.
      • If the contact strip is of non-zero width, as it must be to avoid infinite shear forces, then you've got a difference in radius (perpendicular to the axis) from one side to the other. This will a) cause torque steer and b) scrubbing.

        Now the rougher the surface, the wider the contract strip will potentially be; you could even have a case where a peak next to a hole could cause it to be touching on opposite sides. It'd bounce all over the place.

    • by Urkki (668283) on Saturday July 09, 2011 @05:23AM (#36703322)

      It's a cute idea. It assumes a single point of contact with the ground, and thus requires a flat, hard floor. This is limiting.

      Fortunately, there's a solution [thepavedearth.com]: one world, one people, one slab of asphalt!

    • by timothyb89 (1259272) on Saturday July 09, 2011 @06:45AM (#36703536) Homepage

      It's a cute idea. It assumes a single point of contact with the ground, and thus requires a flat, hard floor. This is limiting.

      I've worked pretty extensively with mechanum wheels - essentially omniwheels with the smaller wheels at a 45 degree angle to the main wheel. Arranging four of them provides the same degrees of freedom as the example shown with two of these HOG wheels. Mechanum wheels work well and move quite fast, and I've yet to see a surface where they don't work - but they're costly, heavy, and wear quickly, not to mention the pretty enormous power requirements. Because of these limitations, for hobbyist robotics, they're simply not practical.

      For many of the smaller projects I've done, traditional drive systems were slow and not nearly as useful as an omnidirectional (3 DOF) system - and without the ability to easily use something like omniwheels or mechanum wheels due to various constraints, HOG wheels would be a godsend. They provide most of the benefits of the traditional omnidirectional drive systems with very few hitches - and you'd be surprised how often the hard and flat surface requirement isn't an issue (or, in many cases, applies to traditional drive systems as well).

    • by mspohr (589790)
      I agree that this implementation requires a flat, hard floor but if you use your imagination just a little bit ... you could use a larger hemisphere and even put knobby tread on it to make an ATV.

      The video even shows one made using two hemispheres for greater maneuverability and traction.

    • by sgt scrub (869860)

      I don't think your dumping on the idea, just pointing out some of its limitations. On that note, I would like to point out another. I would think the weight of the robot would determine the usefulness of this type of drive. If limited to light weight robots, however, it would do fine.

  • Not Novel (Score:4, Informative)

    by mentil (1748130) on Saturday July 09, 2011 @01:01AM (#36702680)

    The video embedded in TFA contains the engineer who created this saying that it was invented about 100 years ago, but nothing came of it and the tech was forgotten. He did rediscover it independently, however.

  • the innovation by the student is great and shows the university has the talent to polish and show to the world.
    • by Anonymous Coward

      the innovation by the student is great and shows the university has the talent to polish and show to the world.

      the "university" did nothing. stop trying to displace this person's achievement and give it to an institution. it's like saying large corporations do most of the innovation. 1. it's not true. 2. legal entities that don't have sentient thought don't do anything in and of themselves.

      • by Joce640k (829181)

        Maybe they put him in a room with lots of motors and remote control electronics so he could fiddle around...

  • iRobot cars? (Score:4, Interesting)

    by MrQuacker (1938262) on Saturday July 09, 2011 @01:40AM (#36702774)

    So, the funky cars they used in the iRobot movie with Will Smith, this re-invention now makes them possible? I am curious to know how well it works on rougher surfaces, like potholes, sand, or gravel.

    • by hitmark (640295)

      In the movie they used a rubber ball and multiple contact "wheels" to spin it in various directions as needed (one pr wanted axis of rotation at least). Quite possible right now but likely need a whole lot more computing power then what this robot has available.

    • by dlb (17444)

      Are referring to the online movie about the Roomba [youtube.com] vacuum cleaning robot?

      Or maybe you mean the theatrical movie called I, Robot [imdb.com]

  • Cute toy (Score:4, Interesting)

    by jklovanc (1603149) on Saturday July 09, 2011 @02:16AM (#36702874)

    It seems interesting but I have a few concerns (some have been stated in other posts but I would like to get them in one place).
    1. Uneven surfaces; With such a small surface contact it is easy to lose traction.
    2. Control. It seems that one can change direction at will but it seems difficult to do it accurately and more difficult to stop the device.
    3. Soft surfaces; if the hemisphere is going at a constant speed would it dig into a sift surface when stopped? Sure you can stop the motor but that means you would have the same acceleration characteristics of a conventional wheel.

    I would have liked to see it on bare concrete doing a slalom and stopping at a designated point.

    • by hitmark (640295)

      issue 2 likely comes from vehicle weight vs engine torque.

    • 4. Whenever it changes direction, both when switching turn direction and particularly when it stops or reverses, it does so by suddenly switching the wheel direction and accelerating the other way. Which means if this was scaled to any significant side, it would be chewing through 'tires' at a ridiculous rate as well as leaving burnt rubber skid marks all over the place. Imagine, if you will, what would happen to your tires if you were in a full size car going 55mph and the only way to slow down was to sudd

  • Another cool drive mechanism coming soon to your local robotics competition, alongside dozens of other ways [google.com] I would never have dreamed to make a robot haul across the competition floor. You definitely won't be seeing on it a car because it's too inefficient, wears quickly and can't handle rough roads.
    • by arth1 (260657)

      It doesn't have to be slick, nor a hemisphere, really. It would work with a spinning tractor wheel too, or a spinning padwheel for boats. Tilt it, lower it, and off you go.
      You can even use a spinning steel cogwheel if you don't care about damaging the surface you drive on.

      The problem with using it for human transport is that quite a few humans have an aversion to fast acceleration. (These accelerophobes are usually right in front of me at traffic lights.)

  • Looking forward to when this is the last thing that I see before the whirring blades eviscerate me.

    • Well, give Skynet some credit. Spinning blades are just as effective, and loads cheaper, than bullets or lasers.

  • by poodlediagram (1944244) on Saturday July 09, 2011 @03:08AM (#36703002)

    This has already been turned into a personal vehicle some years ago. It won the 1988 Toyota Olympic Ideas competition and ran on perpetually spinning Chinese woks. The best link I can find is

    http://books.google.com/books?id=1M3e82yGmZMC&pg=PA27&lpg=PA27#v=onepage&q&f=false [google.com]

    Perhaps someone can find a better picture or video.

    • by Goboxer (1821502)

      Don't you know that if something is not popular or memorable people just claim to invent it, discovered it, or gave birth to it. This is exacerbated by the media not doing any kind of followup. This will probably be on the front page of the major tech blogs, or possibly my local news, with the "reporter" regurgitating the information they can skim from a single source. So I guess the rest of us have to act surprised when something is "invented" every few years.

      Sorry for ranting. It is a neat device and kudo

      • in the video, the guy actually says, "i thought i invented this but then i found out that this tech is >100 yrs old".

  • It is not a novel idea, he mentions it himself at 1:07: an almost 100 year old idea that everybody has forgotten :-)

    Quite cool idea though. Looking back at those first "automobile like" designs; cars with legs, monowheels etc. it is not surprising - they were good at thinking outside the "4 wheels on a box" box back then. Probably because the "car" idea was not established yet.

  • 1. Why keep the motor running at constant rpm? Sure, those peelouts are fun but they cause tire wear and won't work too well on loose surfaces. And in the video, the wheel bounces off the ground when going from forward to reverse. That depends on the power-to-weight ratio and won't be so much of a problem in production vehicles, though.

    2. The video doesn't show how the system behaves at low speeds (ie with the wheel at an angle approaching 90 degrees). I suspect that at those angles, the direction of the d

  • WTF is a "gimbaledl"?

  • Oh, janitors all over the world are gonna hate this guy. A spinning rubber hemisphere touching the freshly waxed floor all over the place will not only wreak havoc with the floor wax but may eventually damage the tile.
    • by gl4ss (559668)
      just make the thing of wax and they'll wax as they go.the hemisphere would better have a free floating ball at zero point though, otherwise there's a reason why nobody built the speeder drawn in '38.
    • by cboirum (2358822)
      LOL you have no idea! Luckily I made good friends with the janitor who works the hall outside the robotics lab. The new prototype uses a very smooth polyurethane wheel just for this reason. It really decreases the acceleration but doesn't mar up the floor as much. It also makes the effect of small bumps and/or cracks in the ground surface almost non-existent.
      • It's not often that the people a Slashdot post is about actually respond. Cool!

        You know, you could take a little bit of the other commenter's idea and replace the rubber with a hemispherical, compressed cloth, buffing pad. Then impregnate it with wax and away you go. In the end, one commercial implementation of this could be a robotic floor buffer. It could propel itself around the floor in the same way janitors already propel buffers around. The pad is flat but they just lean it a little in one directio
  • by Anonymous Coward

    Voith schneider propeller. Much like the spinning rubber hemisphere in this robot the propeller can spin up to speed with the vehicle stationary and quickly move the vehicle in any direction by rotating a series of underwater hydrofoils:
    http://www.voithturbo.de/de-pua-marine-vspropeller-demprogramm.php

  • I visualized a spinning black hemisphere scuttling about by tilting itself. From the article I learn that it's just a drive wheel.

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