DiscoBots Omni Drive over Bump

[lynca]

DiscoBots testing their omni drive robot on Wednesday, it worked well over the bump. These are 8" AndyMark Omni wheels with standard toughbox configuration.

http://lamar.discobots.org/node/8

More wheels will be added to this drivetrain in the future, but this was a good proof of concept.
Suggestions, Comments ? Let us know what you think.

[racer6]

looks good

[PerpetualMotion]

Why omni directional wheels if you can not go in omni directions

[nickd2012]

Originally Posted by PerpetualMotion

Why omni directional wheels if you can not go in omni directions

"More wheels will be added to this drivetrain in the future"

[LostProphet]

i think Omni wheels would work if your going with a front wheels drive.

[Geek 2.0]

Where do you intend to put the other wheels?

[PerpetualMotion]

Unless you have a 4 wheel drive robot with two traction wheels and two omni wheels, I think this is a pointless experiment. Whats the point of having 4 omni wheels if you don't move in omni directions. If you are going to add wheels, then its sounds like you're going to have 6WD, which has a much different dynamic for going over bumps then 4WD, so nothing from this experiment can be translated. If you are going to do some sort of holonomic drive, then you are going to be losing traction and again this experiment becomes useless.

[Geek 2.0]

Originally Posted by PerpetualMotion

Unless you have a 4 wheel drive robot with two traction wheels and two omni wheels, I think this is a pointless experiment. Whats the point of having 4 omni wheels if you don't move in omni directions. If you are going to add wheels, then its sounds like you're going to have 6WD, which has a much different dynamic for going over bumps then 4WD, so nothing from this experiment can be translated. If you are going to do some sort of holonomic drive, then you are going to be losing traction and again this experiment becomes useless.

As far as I understand, you don't LOSE traction with holonomic. However, you DON'T have as much power. In my opinion, this proves that you can make it up with the omnis. With holonomic drive, it'll just be slower.

[JesseK]

Thanks for posting this lynca. This confirms our K'Nex mockup's tendencies to auto-straighten the rear omni's after the front wheels crest the top. There was one instance where it didn't auto-straighten, but it looks like that was because the whole robot bounced a bit.

I'd recommend adding some weight to the setup, either via a small chield (j/k ), weight room weights, or some other means. It'll be a whole different animal to control when there's mass preventing it from climing and/or assisting it down the other side.

[Andrew Schuetze]

Originally Posted by PerpetualMotion

Whats the point of having 4 omni wheels if you don't move in omni directions.

I am not a Discobot mentor however, I conjecture that the point of 4 wheel omni drive is to create as much turning ability from a tank steer drive-train as is possible on carpet. With just omniwheels on the front the robot pivots from the mid-point of the rear axle. You will notice in the video that this robot pivots from the center of the drive-train. Not a sweeping or gate turn but rather a point turn.

I too am interested in where, what type, and why they intend to add more wheels are posted by Andrew L.

Andrew S.

[artdutra04]

Originally Posted by Andrew Schuetze

I am not a Discobot mentor however, I conjecture that the point of 4 wheel omni drive is to create as much turning ability from a tank steer drive-train as is possible on carpet. With just omniwheels on the front the robot pivots from the mid-point of the rear axle. You will notice in the video that this robot pivots from the center of the drive-train. Not a sweeping or gate turn but rather a point turn.

I too am interested in where, what type, and why they intend to add more wheels are posted by Andrew L.

Andrew S.

You can achieve the same zero turn radius spin with two omni and two traction wheels if the omni/traction wheels are at opposite corners of the robot. So if the front left wheel was an omni, the rear left would be traction, the front right would be traction, and the rear right would be omni.

[Green2]

I noticed that the robot seems to fishtail at times. Is that due to operator or does the robot have some issues with launching and going straight at the start of motion?

[DTTrobotics1]

I find this experiment that you carried out to be very interesting.

We've been wondering of any way to actually get over that bump for awhile... I don't recall us testing that out yet...

The omni-wheels should also help with the carpet + rubber tire situation.

[GaryVoshol]

Have you considered adding the bumpers to the bot yet? If those are 8" omnis, it looks to me as if the frame member is 12 or 13 inches off the ground. The bottom of your bumper will be no more than 11". Bottoming out?

And a more general question which should be of interest for all teams - what will keep a ball from rolling more than 3" under the frame in this kind of setup?

[Brian Ha]

I couldn't view the video but from discussion from our team it would be very diffucult to get over bumps because of the vertical incline. Also watch that if you do put on omni wheels you would be pin pretty easyly(however you spell it) I could be wrong and maybe your robot could get over the bump but watch out for easy pinning.