Truly omnidirectional omniwheels?

[Alex Cormier]

Hey, i remember seeing your team at FLR. Where did you get the inspiration for your omni wheels?

I <3 OMNI wheels!

[Exotria]

Yeah, casters are what I've been talking about. Although with further thought, I've realized that if you have the rotation limited and the caster needs to move that way because the robot is moving in such a way that it wouldn't spin the other way... might have to do something with springs so that the wheels move to default when off the ground. Of course, ball bearings were my first idea, but then I realized the whole 'robot not moving' thing, so I switched my idea into the (heavily modified)casters plan. Probably not traditional casters, though... might want the axis in the center.

And FLR was awesome. Team 229... can't say as I can recall that one, and you have the 1126 site in your profile. Link me to a pic so I can remember. 1126 was awesome, of course. I remember- you guys CRUSHED the opposition. It was so fun to watch! Your shooter was pretty danged great. We(the Duct Tape Bandits) couldn't say we were spiffed to lose, but we had the six hour bus ride home on the AWESOMEST BUS EVER to make us feel better. Seriously, we had a 42 inch widescreen HDTV, strobe lights, lasers, a fog machine, ceiling mirrors, fiber optics, subwoofers, hardwood flooring, sideways leather seating(with tables and cupholders), those things with the electricity where you touch them and all the electricity is attracted to your hand... it was the greatest bus ever. Most definitely my most fun experience in a while.

Also, the inspiration for the omniwheels came when I was bored enough to try to think of an innovative drivetrain, so I was thinking up a hexagon design, until I realized it wouldn't work with omniwheels because the little wheels wouldn't be facing the proper way, and if you moved them so they faced the right way, they wouldn't be facing the right way for moving other directions. So I decided I'd think of a way to make a better omniwheel that would ACTUALLY be omni, instead of just forward and sideways. This was all at one in the morning, of course... took a nap soon as I got home, woke up at 11, didn't feel like doing homework... all that great stuff. You can think up crazy stuff at one in the morning. Best time for innovation.

...yeah. So, with modded casters(methinks they'd need some reinforcements to hold a hundred pounds of metal moving at high speed- I'm thinking some sort of box protection design with stronger sides for holding the wheel so the axel doesn't break under stress), omniwheels can be made to be MUCH more omnidirectional for weird drive trains like the hex drive train I want to do.

...I need some sort of CAD program for my computer so I can draw this. Or I can use one of my dad's programs. He has Python. Would that work for CAD drawings?

(I'm just posting all this stuff here instead of talking with my team because my team probably wouldn't listen to me-not very popular with people because I have problems censoring myself in conversation and am hyperactive)

All right. More opinions on my(hopefully now clarified) idea?

[Alex Cormier]

well, i am no longer on 1126. i stepped up to college this year and am on 229. Clarkson University robotics. The reason why i asked where ya got the inspiration for those wheels, i that i made ones in 04' that looked similar. heres a picture.

also here is a close up of the wheels.


There is more info on www.gosparx.org too

[Exotria]

Erm... I'm afraid I can't see the resemblance between those omniwheels and my idea. They look like regular(multicolored) omniwheels to me... what's making them different from the normal kind?

[Alex Cormier]

Originally Posted by Exotria

Erm... I'm afraid I can't see the resemblance between those omniwheels and my idea. They look like regular(multicolored) omniwheels to me... what's making them different from the normal kind?

i was stating to the ones made on this years robot of yours.

http://robotphotos.org/v/first/finge..._7564.JPG.html

[Exotria]

Ah, yes. Very similar to our design. Great minds think alike. Unfortunately, I didn't know what an omniwheel was before this year. So I wasn't involved in that aspect... which means I don't get to qualify as a great mind. Curses.

And there are pictures of our robot online? Kickin! Those are some danged good pictures too... although it does give the inherent stalker-ish aspect, considering there's a picture of me in there... ah well.

[Exotria]

...I can't visualize omniwheels working perfectly at a 60 degree angle from the direction they're suppose to roll...

[George1902]

Originally Posted by Exotria

...I can't visualize omniwheels working perfectly at a 60 degree angle from the direction they're suppose to roll...

When the robot is moving in the direction of rotation, the wheel rotates and the rollers are stationary on their axes. When the robot is moving perpendicular to the direction of rotation, the rollers rotate and the wheel is stationary on its axis. Any vector in between these produces rotation on both the rollers' axes and the wheel's axis.

[Exotria]

I don't know about your team, but our motors use an autolocking system so that it's harder for us to be pushed. Thus, whenever a motor isn't receiving instructions, it locks itself up, so if certain motors are moving(say, two matching sides in a hex drivetrain design) while others aren't, the wheels wouldn't be rolling to go along with the miniwheels. Omniwheels wouldn't be very omni in that situation. And that's the point of my idea.

[RogerR]

Originally Posted by Exotria

I don't know about your team, but our motors use an autolocking system so that it's harder for us to be pushed. Thus, whenever a motor isn't receiving instructions, it locks itself up, so if certain motors are moving(say, two matching sides in a hex drivetrain design) while others aren't, the wheels wouldn't be rolling to go along with the miniwheels. Omniwheels wouldn't be very omni in that situation. And that's the point of my idea.

the hex drive train that you're talking about would definitely work with traditional omni wheels. you're right about the wheels not being able to free-wheel when the motor is unpowered, but this is a good thing. you want the rollers to only free-wheel in a direction that has another powered wheel opposing it, so that the powered can control motion in that direction. if the rollers swivel, then the drive will be difficult to control, and will have virtually no traction (how much traction does a desk chair get?).

i'm sorry if this doesn't make sense; omni directional drive trains are difficult to explain without delving into vectors trigonometry.

[Alan Anderson]

Originally Posted by Exotria

I don't know about your team, but our motors use an autolocking system so that it's harder for us to be pushed. Thus, whenever a motor isn't receiving instructions, it locks itself up, so if certain motors are moving(say, two matching sides in a hex drivetrain design) while others aren't, the wheels wouldn't be rolling to go along with the miniwheels. Omniwheels wouldn't be very omni in that situation. And that's the point of my idea.

I guess I still don't understand the point. Are you trying to make an omniwheel that rolls freely in every direction? A standard omniwheel does that. Are you trying to make an omniwheel that rolls freely in every direction even when it's prevented from turning around its main axis? That would work exactly against your reason for locking the drive shaft in the first place.

[Mr. Freeman]

I think he wants an "omni"wheel that will roll freely in every single direction except forward/backward. (Thus, the motors will still drive the wheel along one axis.)

With traditional omniwheels you can push them only sideways if the driveshaft isn't moving. With the wheels he's talking about you could still push the wheel at a 45 degree angle with forward being 0 degrees.

It wouldn't have very much traction though, but I think that's the point.

[Exotria]

Yeah, that's what I'm going for. Of course, a more senior team member is telling me I'm dumb, so most likely it won't ever happen. Of course, I can still dream.

The locking of the motors would still have its intended effect because from almost any angle there would be wheels going forward or close enough forward so that the wheels wouldn't let it roll. Or something akin to that.

And Roger, I'm afraid I can't... really visualize your statement of the problems. Someone needs to invent a machine that visualizes thoughts and sticks them on a screen. To be used for purely scientific purposes.

[chrisinmd]

Originally Posted by Exotria

I don't know about your team, but our motors use an autolocking system so that it's harder for us to be pushed. Thus, whenever a motor isn't receiving instructions, it locks itself up, so if certain motors are moving(say, two matching sides in a hex drivetrain design) while others aren't, the wheels wouldn't be rolling to go along with the miniwheels. Omniwheels wouldn't be very omni in that situation. And that's the point of my idea.

Are you talking about the brake/coast jumpers on the victors? You can set the jumpers on the speed controllers to short the motors with a neutral command (127), this causes them to brake. You can also set them to coast on neutral, which lets the motors free spin. The jumper block is right below the PWM cable port on the victor.