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-   -   Omni Wheels Survey (http://www.chiefdelphi.com/forums/showthread.php?t=28168)

Al Skierkiewicz 26-04-2004 07:10

Re: Omni Wheels Survey
 
Wildstang has used a variety of different designs for omni wheels over the years. We scratch build our own and have modified the design each time we used them. This year we used two driven omni (we call them BUPODfor Biased UniPlanar Omni Directional) and two crab drive modules for four wheel drive. In crab from side to side we had to add some software to help the robot drive straight which we called "Drive Straight". The omni wheels tend to go where they want when they are not driving.

RogerR 26-04-2004 09:11

Re: Omni Wheels Survey
 
Quote:

Originally Posted by George1083
....Mecanum wheels have the rollers at 45* angles which produces the same vectors as a normal holonomic platform with its wheels at 45* angles.

are you sure about this? when a mecanum moves 'forward' or 'backward' (relative to its wheels) the rollers don't spin, so the mecanum unit functions as a normal wheel would. i assumed that since the rollers were at 45*, when the robot "crabbed" left or right, it would exhibit the same charecteristics.

George1902 26-04-2004 13:40

Re: Omni Wheels Survey
 
If the mecanum wheels produced 100% power in the forward or reverse direction, it would be impossible to strafe. We know that this setup can strafe, so the power must be in the direction that the rollers are facing.

Another proof is to watch a video of a holonomic platform with mecanum wheels. Watch what happens when 2 wheels on a diagonal are powered. The robot moves in the direction that the rollers are facing.

Max Lobovsky 26-04-2004 13:58

Re: Omni Wheels Survey
 
George, i know 1083 wants to try to build its own omniwheels next year and i was wondering if you were planning to make them bigger than those 4.72" ones from omniwheel.com. I can't actually think of a valid reason why wheels that small are bad, but very few teams seem to use wheels that small, so there is probably a reason. Maybe a larger wheel gives you the potential for better traction. (yes, i know in theory traction is only dependent on the weight of the robot and the materials contacting each other, but in practice, it isnt that simple) Your grooved omniwheels seemed to have better traction than any others, bought or built.

RogerR 26-04-2004 19:45

Re: Omni Wheels Survey
 
sorry i took so long replying...
Quote:

Originally Posted by George1083
If the mecanum wheels produced 100% power in the forward or reverse direction, it would be impossible to strafe. We know that this setup can strafe, so the power must be in the direction that the rollers are facing....

thats the thing though; the only time that the mecanum wheels are acting like 'traditional' omni wheels are when the bot is moving at any angle between forward/back and side to side. when moving forward/back, they act like treads. when strafing, they act like propeller blades.

<hare-brained idea> on that note (prop. blades) i'd also like to throw out an idea that i got from watching the bots strafe back and forth. what if you were able to change the angle of the rollers? decreasing the angle would move you less distance per each "wheel" rotation, but would give you more pushing force.the angle of the rollers could be changed by a mechanism similar to the ones used to change the blade pitch on prop. aircraft. </hare-brained idea>

George1902 26-04-2004 23:10

Re: Omni Wheels Survey
 
Quote:

Originally Posted by maxlobovsky
George, i know 1083 wants to try to build its own omniwheels next year and i was wondering if you were planning to make them bigger than those 4.72" ones from omniwheel.com.

If we do build our own, they'll prolly be bigger. I think bigger ones are easier to make, although I'm not totally sure about that. 6" would be a good size, I think.
Quote:

Originally Posted by maxlobovsky
I can't actually think of a valid reason why wheels that small are bad, but very few teams seem to use wheels that small, so there is probably a reason.

The main problem we had with the smaller wheels was clearance. I think our robot ended up with < .5" of ground clearance. :yikes:
Quote:

Originally Posted by maxlobovsky
Your grooved omniwheels seemed to have better traction than any others, bought or built.

Thank you very much. =-]
That's probably the best argument for us using them again in the future.

Zotas 27-04-2004 07:51

Re: Omni Wheels Survey
 
Quote:

Originally Posted by Al Skierkiewicz
Wildstang has used a variety of different designs for omni wheels over the years. We scratch build our own and have modified the design each time we used them. This year we used two driven omni (we call them BUPODfor Biased UniPlanar Omni Directional) and two crab drive modules for four wheel drive. In crab from side to side we had to add some software to help the robot drive straight which we called "Drive Straight". The omni wheels tend to go where they want when they are not driving.

I am interested in what you guys (Wildstang) used for the rollers that interacted with the carpet. I took a peek and it looked like you had neoprene disks, except they were not punched. Can you enlighten us?

Thank you,
Jake Mazotas

Raul 27-04-2004 09:54

Re: Omni Wheels Survey
 
Quote:

Originally Posted by Jake Mazotas
I am interested in what you guys (Wildstang) used for the rollers that interacted with the carpet. I took a peek and it looked like you had neoprene disks, except they were not punched. Can you enlighten us?

Thank you,
Jake Mazotas

They were 3/4" diameter Polyurethane rods (75 durometer) bought from McMaster Carr.

tiffany34990 27-04-2004 17:21

Re: Omni Wheels Survey
 
Quote:

Originally Posted by George1083
Tiffany!?

::GASP::

Not only have you guys seen one, but it was at the Florida Regional with you.


sry george meaning that nobody made wheels like us-- design that james came up with and that i got to help make and well yeah get to fix them again :ahh: :)

Ellery 30-04-2004 10:51

Re: Omni Wheels Survey
 
1 Attachment(s)
We (X-CATS 191) used Omni wheels for the first time this year as well... They worked very well and we even made them from scrath recycling old copier parts we pulled out of some dumpster. I'll have to get some closer pictures for ya.

We made an 8 wheel drive system that walked up the platform. It worked well except for the side traction when we were halfway up a step and then we had issues sliding.. Oh well you live and learn...

Ellery

ngreen 30-04-2004 11:37

Re: Omni Wheels Survey
 
Quote:

Originally Posted by Ellery
They worked very well and we even made them from scrath recycling old copier parts we pulled out of some dumpster.

Old copier parts work great for robots. We have pieces of an old one we keep in a box. Lot of good things. We about used a ratchet for our winch that would have came from one and use a couple other pieces to couple a motor to a shaft. If you look beside the van door motor in this picture you can see a piece of an old copier on its right between it and the pillow block. If you could see the top it has a little hole and says oil. We didn't use any though.

SpaceOsc 30-04-2004 13:04

Re: Omni Wheels Survey
 
I think everyones forgetting (or you just werent around) one of the proven bots out there with large omni wheels and they happend to use 6 of them they went in all directions they didnt get pushed around and there was no easy side to push them from they turned marvelously and speed and power to boot

MIM Metal in Motion 343 2002 bot still one of my fav robots of all time check them out and youll see there design ... i wanted to build something like that but i couldnt get the whole building omni wheels thing started any suggestions or things only expirience teaches u when building this nice lil wheels? things i should watch out for when tyring to build and use them?

Cobbimus 03-05-2004 13:22

Re: Omni Wheels Survey
 
Quote:

Originally Posted by SpaceOsc
I think everyones forgetting (or you just werent around) one of the proven bots out there with large omni wheels and they happend to use 6 of them they went in all directions they didnt get pushed around and there was no easy side to push them from they turned marvelously and speed and power to boot

MIM Metal in Motion 343 2002 bot still one of my fav robots of all time check them out and youll see there design ... i wanted to build something like that but i couldnt get the whole building omni wheels thing started any suggestions or things only expirience teaches u when building this nice lil wheels? things i should watch out for when tyring to build and use them?

I was primary operator on team 343 this season and would like to thank you for your comments on "Manuel Overdrive". One thing you might watch out for on your omni wheels is the fact that the small wheels on M.O.'s omni wheels are metal and this year metal was restricted from touching the carpet on the playing field, this may only be a temporary rule or permanent. Thats all the advice I have for now, but I will pass word along to our engineers and they might be of more help to you. Thank You and may gracious professionalism live on! :cool:

SpaceOsc 03-05-2004 13:48

Re: Omni Wheels Survey
 
Quote:

Originally Posted by Cobbimus
I was primary operator on team 343 this season and would like to thank you for your comments on "Manuel Overdrive". One thing you might watch out for on your omni wheels is the fact that the small wheels on M.O.'s omni wheels are metal and this year metal was restricted from touching the carpet on the playing field, this may only be a temporary rule or permanent. Thats all the advice I have for now, but I will pass word along to our engineers and they might be of more help to you. Thank You and may gracious professionalism live on! :cool:

Why where they metal? what did that do?

Gary Dillard 04-05-2004 13:24

Re: Omni Wheels Survey
 
Quote:

Originally Posted by SpaceOsc
I think everyones forgetting (or you just werent around) one of the proven bots out there with large omni wheels and they happend to use 6 of them they went in all directions they didnt get pushed around and there was no easy side to push them from they turned marvelously and speed and power to boot

MIM Metal in Motion 343 2002 bot still one of my fav robots of all time check them out and youll see there design ... i wanted to build something like that but i couldnt get the whole building omni wheels thing started any suggestions or things only expirience teaches u when building this nice lil wheels? things i should watch out for when tyring to build and use them?

That was definitely a sweet robot - we teamed with them to win KSC regionals (with 186 also). Kinda funny that they've switched from omni wheels to Brekoflex drive and we've switched from Brekoflex to omni wheels.


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