2008 and drivetrains

[SandSkrit]

Hey, any pictures or video on that "drifting" robot yet? CAD or hand drawn at least? That's EXACTLY the idea we came up for team this year, too.

[writchie]

What I am looking forward to is the emergence of "car" steering. We are seriously considering setting up just like a sports car... rear wheel drive, front wheel steering. While it doesn't have a "zero" turn radius like tank drive, it should work great for high speed cornering and swerving around other robots heading down the straights.

But we've got a few other tests to run before we commit to that just yet.

Jason

We too are looking seriously at rear wheel drives, independent suspensions, Ackerman steering in the front (and perhaps also the rear), two drive trains and software differential. All this is of course before we apply KISS and also depends on where we settle with our base strategy.

I've seen lots of posts suggesting that perhaps the math hasn't yet been done by some of the teams. Centripetal force is square law and high traction is necessary for high speed cornering.

I AM glad to see a new challenge where just the same old 6WD skid steered pushbot of yesteryear may not necessarily be the optimal drive configuration. However, I am not looking forward to the mechanical carnage we are likely to see on the field from mv**2/2 from 10 sources.

[MrForbes]

KISS might eliminate the suspension, rear steering, and differential....and just leave two motors and one transmission per side in back, and steering in front operated by a window motor.

[Alex.Norton]

m*v^2/2 doesn't sound right... isn't it m*v^2/r. Ya that sounds a little batter...

In either case I love the idea of a nice easy to control skid steer system like a 6wd since it doesn't turn to easy but also doesn't turn too hard. In the past we had a bot that went from unable to turn to uncontrollably easy to turn when we changed from 4wd to casters and I don't like the complexity of the ackerman.

I hate to be a follower after 3 years of omni but I have to say that I don't think the maneuverability of a mechanum or omni is going to help (especially after driving them) and I hate pretty much all forms of normal 4wd so my votes in for 6wd.

[Doug G]

We debated using a steering system for the first few days, but as of recently backed off of it. My gut says that the field will get congested enough that the loss of manueverability will hamper the advantages of a steering system set up.

A few students on our team feel that crab is the optimal choice - but we're too nervous about going down that road without testing in the offseason. This year will definitely be a season with varied drive trains.

[writchie]

Originally Posted by Alex.Norton

m*v^2/2 doesn't sound right... isn't it m*v^2/r. Ya that sounds a little batter...

m*v^2/2 is the Kinetic Energy of the objects (Balls and Robots) that will be flying around the field looking for your robot.

m*v^2/r is the centripetal force required to turn the mass. m*v^2/r will hurt you only if you haven't got it. Then you will find out what m*v^2/2 will do to you.

[MrForbes]

I think the result of yesterday's team discussion about drive systems, is that the 3 we considered (6wd skid steer, 2wd car steering, mecanum) all have enough advantages and disadvantages that none really stands out as the best drive.

So we may end up going with car steering to learn something new, or with 6wd because we know how, or with mecanum because it's so fun to drive.

My guess is that engineering/cost/material considerations will weigh heavily in the decision.

[Jeff Waegelin]

I think the biggest key to drivetrains this year is going to be driver practice. Regardless of what kind of drive system you have, your drivers are going to have to be comfortable with your machine. It may be better to have a simple, reliable design done with time to spare, than to have a complex one that you have to finish at your first event (and therefore get no practice).

[Cartwright]

We're creating a six wheel drive with the center wheel driving off the transmission and the back wheel driven by chain. The front wheels will be free, and both the back and front wheels will be omnis. This is a modification of last year's drive.

[diesel]

I was hoping for a more standard game with a standard drive as this is only our teams second year.

But we are looking at driving two traction wheels in the front, with some form of turning the back wheels.

And I agree this year the drives will want as much experience they can get driving their robots.

[soccer_ghena]

How do you mount the faceplates on a kitframe??

[jimbot]

Our team did car steering last year and found some troubles. For one you deffinatly DON'T want to use servos. When we got to worlds, they constatly cut out and left us with no steering. If you used a rack and pinnion Your robot could be reliable, agile, and fast with a good drive train.

This year we are thinking of using omni, but the 45 degree settings would cause a 30% efficency reduction on them. Any imputs?

[SoJ]

Originally Posted by abeD

I can also remember several teams that have employed some kind of steering, obviously all the crab drives, but 16 baxter bomb squad a couple years ago had a tricycle setup with all 3 wheels driven and 1 steered, worked very well from what I remember.

We're going with something like that again this year. It'll be able to crab and be steered by just the one, so we're hoping that maneuverability's gonna help us out. That and we've got a (somewhat) working '07 bot for our drivers to start in on. Practice is gonna be huge.

[GUI]

Today we put together a quick ackerman prototype on the kit frame (one of our mentors welded together some simple spindles for this purpose). Even without the desired dimensions (long wheelbase, wide apart front wheels) and the geometry being off slightly, it has a pretty tight turning radius. We didn't get a chance to drive it, so we won't know about actual performance until tomorrow.

[Rick-906]

We are seriously considering ackermann steering, it seems to be the best option in terms of efficient turning, plus it has a certain familiarity to it.
depending on how complicated we want to get, we may power all four wheels, but at this stage it seems wisest to use KISS and just power the rear wheels.

i quite like this years game so far, and i think that a good drivetrain will be key in building a competitive robot. it could be a major mistake to build a very simple drivetrain and focus only on the manipulator. but i suppose only real gameplay will tell