Improved Mecanum Wheels
 

http://www.araa.asn.au/acra/acra2002...eter-Tlale.pdf :rolleyes:

I thought with all the talk of new ideas for FIRST robots and drivetrain and mechaums I would thorw this link out there. I really like the chasis design they have with both Mechnaum wheels and pneumatic wheels on pg.4. There is also useful info on the mechaum wheels themselves. All in All very cool link. Tell me what you engineers and mechanical people think about doing this on a FIRST robot.

Thank you and hope this is informative and interesting.
- Drew

Re: Check it out
 

i quickly read/skimmed the article and there are some interesting points about efficiency of the different mountings of the mecanum wheel rollers. As far as the drive base with 2 sets of wheels the applications for FIRST are limited because of weight. it also seem unnecessary because their only reasoning for the 2 sets of wheels is rough terrain which we won't typically have in FIRST.

Re: Check it out
 

This is definitely cool. I seem to remember it from somewhere but after taking a second look i think I'm going to forward it to the rest of my team. Thanks! :)

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Mr.Needel I see your point however you do need to push sometimes during a match. :) thanks for the input.

-Drew

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please....Mr. Needel is my father :rolleyes:

Re: Check it out
 

There have always been problems with using mecanum for FIRST: firstly the programming and control is tricky, and making the wheel itself is rather anoying. I for one will hopefully be having a mecanum robot this year, so I guess I shouldn't be complaining. I chose to go this path... but anyway, this article is a very interesting one. I appreciate how they push the design of the mecanum wheel to its limit in efficiency. However, I think the most I would ever consider is putting pneumatic locks on the rollers to improve forward efficiency.

Thanks for posting this article.

Re: Improved Mecanum Wheels
 

I <3 mecanums. I just wish my team felt the same way :(

Re: Improved Mecanum Wheels
 

you may be interested in the following discussions of Mecanum wheels, several of which link to the same paper.

http://www.chiefdelphi.com/forums/sh...hlight=mecanum
http://www.chiefdelphi.com/forums/sh...hlight=mecanum
http://www.chiefdelphi.com/forums/sh...hlight=mecanum
http://www.chiefdelphi.com/forums/sh...hlight=mecanum
http://www.chiefdelphi.com/forums/sh...hlight=mecanum
http://www.chiefdelphi.com/forums/sh...hlight=mecanum

Re: Improved Mecanum Wheels
 

I know about mechaums I am talking about the two diffrent wheels design on p.4 of the link. Weather or not people think it is adventageous or worth putting the time and effort to making. Sry I didn't clarify this earlier.

Re: Improved Mecanum Wheels
 

Several teams have, in years passed, built drive trains that have two sets of wheels or treads, with only one being engaged to the ground at a time. They were most typically used in games that were traction-heavy such as 2002.

You can look for examples on, I believe, the following robots:
2002 -- Team 810
2002 -- Team 111
2002 -- Team 467
2003 -- Team 980

Re: Improved Mecanum Wheels
 

You mean 2003. :) http://www.team980.com/movies2003/Te...arShiftMed.mov

Re: Check it out
 

Oh? Why?


-dave

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Dave, don't be mean to people who haven't already read the technical specs for this year's water game. It's not our fault we aren't on the game design committee. :rolleyes:

Re: Improved Mecanum Wheels
 

Also, in 2001, 190 used two sets of different sized wheels (essentially, it was a shift on the fly transmission) and in 2003 190 used two sets of wheels mounted at a 90 degree angle to allow us to crab sideways by dropping the second set.

Re: Improved Mecanum Wheels
 

In both 2002 and 2003 Team 358 used two sets of wheels at 90 degrees to one another to accomplish our crab drive. One set was mounted on an outside frame and the other on an inside frame that was raised and lowered pneumatically.

I remember 190's 2003 drive from the BAE Regional.

Re: Improved Mecanum Wheels
 

190 is a very strong team I enjoy what I have seen of them at nationals and I see that they were signed up for UCF for 2006 :ahh: very cool. 1251 will be loud and ready to go as usual. On a another Dave Lavery and the game desgin commitiee dictate everything ahh we shall soon see.

Re: Check it out
 

Admittedly, a bit tongue-in-cheek. But not entirely. There are multiple layers of real questions embedded in that simple little two-word interrogatory. Not all questions, and not all data, are obvious.

-dave

p.s. if you reacted quickly like some and think that the original question means "hey, don't use Mechanum wheels this year" then you haven't looked deep enough.

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I think what Dave is trying to say is that it might not be the best decision to arbitrarily choose what drive system you want to use, before having any clue what the robot needs to do.

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I agree, but I think we'll stick with our mecanum propellers for this years water game! Seriously though, what are the major disadvantages? My team is looking at these and I figure ill take advantage of other's experiences.

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Not much of a point in using them if the game doesn't require manueverability.

Or if there are obstacles that you need to climb.

They won't necessarily be bad for a given game.

But why build a swerve drive if the kitbot will serve your purposes just as well?

Re: Check it out
 

I can think of two major disadvantages, one mid-level technical issue which can range from trivial to showstopper, and quite a lot of little details.

The disadvantages: some of the mechanical power available from the motors is lost to sideways motion of the rollers, so the robot won't be able to push as hard; and it doesn't work well at all unless all four wheels are solidly in contact with the ground.

The technical issue is the control system and software. That's very easy in concept, but might quickly get more difficult depending on how good your programming and system engineering can be.

Details of wheel size, roller mounting, speed sensors, traction, drivetrain, etc. will probably make doing it more of an art than a science unless you've done it before.

Re: Check it out
 

I for one am willing to try these wheels out. Though there is the obvious disadvantage of having a less efficient system of transferring power to the ground, you are given an almost infinite degree of maneuverability. You can drive forward or backward, arc forward or backward, drive sideways, arc sideways, and strafe at any angle, just like swerve drive. It is like swerve drive, but a lot simpler. I think it is a very good drive train for FIRST teams to try out. The programming is tricky but not impossible for rookies, its really just figuring out the math behind the motion. The fabrication is easy if you figure out the tricks behind making it simple.

The only thing you have to consider is that it limits your driving strategy. With this drive, you are not going to be able to win pushing fights against some robots. Robots with six-wheel drive and a low speed are going to ram you into a corner if you have this drive. The point of this drive is for you to make it, and program it, and get the driver so used to it that it is a breeze to fly around such slow moving robots, not ever touching them. This drive is one that demands a coordinated driver, and a fast gearing, maybe 12 feet per second or more. That way you are a super-agile monster of a robot that does tasks fast and never touches another robot.

But of course, I’m just a proponent for this drive train. It all really depends on your driving style. This is just something I’m interested in seeing on the field.

Re: Improved Mecanum Wheels
 

Only one problem with whizzing around those "slow" six wheelers. If they get between you and your objective(s), one "slow" robot, driven right, can block a mecanum. We actually tested this out, and it was one reason we chose not to use mecanum this year. Our mecanum Kitbot could not get around or through our '03 bot by any means, and '03 is not easy to steer (though we didn't need to to block Kitbot). Also, you need your CG pretty well centered, or your robot will not get the full mecanum effect. Moral of the story: TEST FIRST! It could save you a lot of pushing and other fun stuff at competition.

Re: Check it out
 

So is a holonomic platform.

And it's a lot easier mechanically, particularly now that we have the NBD conversion, and AndyMark for the omnis.

I imagine the programming is along the same lines of difficulty as with mechanum.