Truly omnidirectional omniwheels?

[Clark Gilbert]

Originally Posted by dubious elise

The complete ball drive can be found in this photo with a closeup in this photo. I can't find any threads about it right now and I don't know very much about it, save where to find these images . You may wish to ask some of the Technokats Alums - Clark Gilbert, Austin Butler, Greg McCoy, and Kyle Gilbert come to mind - about this unique system.

The best thread to read right now is probably this one:
http://www.chiefdelphi.com/forums/sh...t+ball+dr ive , especially the summary on the first page from Andy Baker. I'll look for the video I posted a long time ago and re-uploda it.

[sciguy125]

Speaking of ball drive, I may have just figured out a way to reinvent the wheel. Think of a stepper motor. Instead of a traditional cylindrical rotor, use a spherical one. Like a golf ball with magnets instead of dimples. Now, use two stators that are 90 degrees apart from each other such that you can rotate the sphere about the x axis and about the y-axis. Voila, compact ball drive.

Now if you'll excuse me, I need to find a patent lawyer.

[Cuog]

Not likely gonna need a patent for those hemispherical wheels we were working on them this summer: http://www.chiefdelphi.com/forums/sh...ad.php?t=40770 but take a look at what we came up with its a cool design

[Exotria]

I don't think you guys are understanding my point... I know about the other omnidirectional drives(thanks for the links, however, I like information). My point is a way to make other omnidirectional drive trains by using another design of omniwheel. That... was my intended purpose for the topic, to ask whether another kind of omniwheel could be made that was more... well, omni. I know that all the other drives are successful, but those innovation awards are really appealing, and I think that another omnidirectional drive train could be made with my idea. I've already said it a few times- rotating rollers instead of just the wheels. Basically lets you have the miniwheels have their x axis rotate, with a little modification so that it can't rotate into the same direction as the wheel itself. This would allow there to be traction for the wheel going forward, and allow it to go any other direction without traction. That would allow wheels to face 45 degrees away from each other, , or any other degree, but not oppose each other. That would let there be more drive trains with opposing wheels. Which means more creativity.

[Mr. Freeman]

What about an omni wheel but instead of having a bunch of wheels around the main one, you just have a bunch of ball bearings stuck into it.

I'm not sure if something like this exists yet, I don't see why it shouldn't.

I see a problem with this though. If you were able to push an omni wheel in any direction, then it wouldn't be able to provide any traction when you rotated it with a motor. It would just spin in place.

Now, someone mentioned something about "the wheels on the bottom of teacher's desks."
I assume that you meant something like these:
http://www.photoflex.com/photoflex/p...300/caster.jpg
Those are called "casters", just for future reference.


EDIT: I just saw something about limiting the casters' rotation as so that they don't allow the wheel to spin in place. Ignore the second paragraph in this post.

[Qbranch]

Originally Posted by sciguy125

Speaking of ball drive, I may have just figured out a way to reinvent the wheel. Think of a stepper motor. Instead of a traditional cylindrical rotor, use a spherical one. Like a golf ball with magnets instead of dimples. Now, use two stators that are 90 degrees apart from each other such that you can rotate the sphere about the x axis and about the y-axis. Voila, compact ball drive.

Now if you'll excuse me, I need to find a patent lawyer.

I've messed around with this idea in order to replicate something I saw in a music video.

A company called Animusic ( www.animusic.com ) makes this sweet midi driven animations... I've always wanted to re-create a scene out of one of the animations... so I'm going for the 3 slightly humanoid looking robots on the "Starship Groove" animation... anyhow back to the story...

The spherical track motor works exactly like a linear track motor except for the fact that the micro-electromagnets are arranged within a sphere made of a non-ferrous material. For my design, this sphere would fit into a matching hemisphere, very slightly larger than the sphere. This, in effect creates a fully functional low-load-bearing ball and socket joint.

OK thats the overview, now heres the problems with it:

There would have to be a processor dedicated to each joint. The design requires at least 3 (4 if it is going to be stable) pulse width modulation channels. It would never be FIRST legal since the victor's update rates are over 26 times too slow for updates. The PWM period would most likely be something like 500ns or so, because of the high instability of intersecting lines of magnetic flux.

The joint itself would have to be encoded for position somehow, perhaps with a hall cell array or something like that. The updates for the servoed position would have to be done every 500ns to keep up with the pulse train, the high update rate is needed to overcome the problems with the intersecting flux lines.

So in a nutshell, here's how it is:
1. Would have to be based on a DSP running around 100MHz for a clock

2. It will eat TONS of current

3. Has to be run at a very very high voltage if you want to get much speed
or load capacity out of it.

4. Will require one UART for positional data input will need 4 channels
of simultaneous high speed PWM, run through a mux chip of some kind
in order to drive the hundreds of micro-electromagnets inside of the
sphere.

5. Will need a super high speed latch chip in order to retrieve data from all
those hall cells.

6. Driver board will have to have a power transistor or mosfet for every
single electromagnet.

7. All parts within about 6 inches of the thing will have to be non ferrous.

8. And oh yeah, the programming will be extremely hard (servoing in 2
dimensions)

Did I lose anyone?

Granted, this is a design which would work for a positional as well as a speed based spherical track motor. But, like I said, my application required positional. It would work for motion purposes as well, though. I'm putting this on my "Things to do before I die" list.

-Q