pic: simple omni vex bot

[colin340]

loading photo ...

[Greg Perkins]

Nice! however, a true omni drive in this configuration would have each wheel at 120 degrees apart from each other. that is the only way (with three wheels) to achieve true holonomic movement.

[Rohan_DHS]

thats pretty cool

[colin340]

thank you for the feed back but i can Quite picture this do you mean like billfreds kiwi drive

[Andrew Blair]

Originally Posted by Greg Perkins

Nice! however, a true omni drive in this configuration would have each wheel at 120 degrees apart from each other. that is the only way (with three wheels) to achieve true holonomic movement.

Not so sure. You will be able to achieve full holonomic manueverability, though at the cost of some speed in certain directions. It's all about vector addition...

[s_forbes]

Originally Posted by Andrew Blair

Not so sure. You will be able to achieve full holonomic manueverability, though at the cost of some speed in certain directions. It's all about vector addition...

The problem with this onidirectional design is that the two angled wheels are 90 degrees off of the angle they should be. You can still strafe and such, but you can't spin on the spot.

It's still omnidirectional, it's just not as omnidirectional as the other disign.

EDIT: Actually, now that I look at it more, it looks like strafing would be difficult with that design as well as turning on the spot. Oh well, it's still cool! And oh so simple!

[Tytus Gerrish]

fits the budget. I like it

[colin340]

Originally Posted by s_forbes

The problem with this onidirectional design is that the two angled wheels are 90 degrees off of the angle they should be. You can still strafe and such, but you can't spin on the spot.

It's still omnidirectional, it's just not as omnidirectional as the other disign.

EDIT: Actually, now that I look at it more, it looks like strafing would be difficult with that design as well as turning on the spot. Oh well, it's still cool! And oh so simple!

you can strafe by slowing one wheel down but it takes a lot of playing a round

as for turning on the spot it can't, it work it's way around in a circle

[Tom Bottiglieri]

I made a kiwi bot out of Vex a few weeks ago. I wish I had seen this before I bent the metal.


sigh..

www.team195.com/files/kiwi.wmv

[colin340]

Originally Posted by Tom Bottiglieri

I made a kiwi bot out of Vex a few weeks ago. I wish I had seen this before I bent the metal.


sigh..

www.team195.com/files/kiwi.wmv

that is my problem with vex I hate benting things

[Gamer930]

Originally Posted by Tom Bottiglieri

I made a kiwi bot out of Vex a few weeks ago. I wish I had seen this before I bent the metal.


sigh..

www.team195.com/files/kiwi.wmv

I notice you ran it on hard wood floor. How does it run on carpet??? I'm looking to build something like that for a demo first week in July but it is all carpet floors. (I could just get some thin plywood board but just curious)

[Tom Bottiglieri]

Originally Posted by Gamer930

I notice you ran it on hard wood floor. How does it run on carpet??? I'm looking to build something like that for a demo first week in July but it is all carpet floors. (I could just get some thin plywood board but just curious)

It seemed to run fine on carpet. It put a little more load on the motors but nothing too significant.

[pistons9876]

I am curious, did you program it to actually drive "omnidirectionally," or does it have limited mobility?

[Adam Y.]

Originally Posted by Tom Bottiglieri

I made a kiwi bot out of Vex a few weeks ago. I wish I had seen this before I bent the metal.


sigh..

www.team195.com/files/kiwi.wmv

I managed to build a omnibot also without bending any metal using a completely different design that is based of the standard chasis. The only annoying thing is that the while the wheels are sperated 90 degrees they are not the same distance apart. Fortunately, this is only a problem that involves changing the program every so slightly with a fudge factor.

[Ian Mackenzie]

This robot is (in theory) perfectly capable of spinning on the spot, moving in any direction, and generally doing any planar motion you can imagine (although in some directions, such as straight forwards or backwards, you'd go quite fast but wouldn't have much pushing force). In practice, though, roller friction might make some types of motion difficult.

The math to make it work is actually pretty simple - I went over precisely that in my presentation at the FIRST Robotics Conference a few days ago. The presentation ("Omnidirectional Drive Systems") should be up on the FIRST site soon, but I've also uploaded it to CD-Media:

http://www.chiefdelphi.com/media/papers/1836

E-mail me or send me a private message if you'd like more detail on how to apply the theory to this particular robot...

EDIT: Actually, looking at the photo again, it looks like the three wheel planes intersect right at the front (back?) wheel, so no, full omnidirectional motion isn't possible. If the two angled bits were just angled some more and moved out further, though...