My team and I were wondering how effective climbing ramps with mecanum wheels would be. I recall from years past they are not very good at climbing ramps, but I was wondering if you used encoders to set a certain speed if they would climb better. Thanks for the input.
Our team was also throwing around this idea, as it would make the robot easy to maneuver/block balls from getting into your goals and to get to balls.
this is the major deciding point on our robot; Do we want to be able to go over the ramps, or do we want more maneuverability and be forced to fit under the passageway!
Have any teams tested Macanum wheels and their ability to make it over the “Hump”?
-McGurky
You might high center on the hump (this could also affect a 4-wheel tank).
ya my team is buying some, we have pretty much given up trying to get over the ramps, and going with a real low center of gravity with mecanum wheels, we see that it might not be to important to get accross the arena except at the end
I can think of two mecanum drives that could do it. 1322 has been playing with one that is specifically designed to climb ramps for a couple of years now: http://www.chiefdelphi.com/media/photos/32185
2826 has a slightly different method that may be more practical: http://www.chiefdelphi.com/media/photos/34306
I played with some mecanum wheels a few years ago on a small scale and I was surprised with how well they climbed over objects. One of the things I did notice though was that the climbing was very Dependant on the surface on which they were climbing. Since the bumps this year are carpeted I would venture to say that a mecanum wheel-ed robot shouldn’t have too many problems with climbing over the bump with the proper fame setup. (May require some suspension)
I know that I’ve been kicking around the idea with one of the students on my team and we think that a mecanum drive based upon the new C-Base for 2010 should be able to climb the bumps without too many problems with some creative weight placement.
Also, If I remember correctly, 357 used some custom mecanum wheels in 2006 and they were able to climb onto the ramp that year without too many problems…
These are both cool designs, and could be very useful this year. Unfortunately, it looks like the GDC doesn’t want us to be that inventive:
<R11> The FRAME PERIMETER must be comprised of fixed, non-articulated structural elements of the ROBOT. The FRAME PERIMETER must remain a fixed, unchanging polygon throughout the MATCH.
Who said anything about these being in the frame perimeter? Remember, that’s counted starting at 10" above the floor. It’s not that hard to put a frame around the outside of these at that height, is it?
if you’re not articulating the bumpers out of the bumper zone, there’s nothing wrong that I can see.
In any case the first one seems valid since it’s just a raised wheel.
Actually, it isn’t. It’s a full suspension. The omnis in the middle start out in a plane with the mecanums. They also happen to have a pivot point for the front of the frame, which can go up or down, sides independent. (In this picture, down; a few moments before, it would have been up.)
My team were throwing around ideas today. And an idea of a 2 part frame that bends in the middle to get over the humps would work really well.
It would have to use six wheels though. But getting over the humps would be easy. =]
My team was throwing around a similar idea-tank treads (on a smaller scale). I think this would be more effective especially for going over the ramps.
these are good ideas, especially the six wheel one. But how about just a standard four wheel mecanum drive train? I’m wondering if any teams tried this for 2006 or even 2007 and how they worked or if anyone saw how they worked.
It’s not a 45 degree incline, by any means, but we got our mecanum to go up a ramp a couple years back. The first try didn’t work, so we fixed up a few things (hence the clip of a student welding the frame) and then tried again.
The catch is keeping all four wheels in contact at the same time… but here’s proof that a “standard” mecanum can climb at least a shallow incline. http://www.youtube.com/dtengineering?gl=CA&hl=en#p/u/12/gyn9e0cT3-A
Jason
P.S. If you want omni directional drive ability, plus climbing… perhaps some form of crab drive is what you’re looking for?
maybe for omni drive… Our Linkage might make a come back?
That would be awesome for me at least… and I know some people on here liked it back when I posted it. If anyone is interested let me know I’ll give out any details you need
Thanks for the video Jason! Pretty neat stuff. I have to note that the ramp is not carpeted. It seems pretty promising, and if used in combination with a really simple suspension, we may have a winner!
I want everybody to know that I am getting HECK!!! from my team mates for posting our drive system. It was fine before this game.
I hope, at the same time, they are feeling very pleased with the opportunity to put your off-season R&D to good work!
Anyone who tries to copy that drive system will be weeks behind where you guys are right now… and even if they do manage to copy it, I’m sure you’ll be on to version 2 before they even get a test platform built.
<rambling>
But this thread has me thinking that maybe we do want to revist mecanums this year… not with an articulated system like that one, that’s just a bit beyond our build capacity this year, even if we replaced the central clutch with an FP and gearbox to drive the omni wheel… but instead… maybe if the front wheels also ran a belt… that didn’t connect to the rear wheels (or else the pulley just free-wheeled on the rear axle) so that when you get high-centred on the climb the belt does the driving. It would be a combination of mecanum and tank-tread drive…
Hmm… I’ll be interested to see what the students say on Monday. This game does seem well-suited to an omni drive, but the extra degrees of freedom offered in their mobility come at the cost of build time, programming time, and driver practice time.
But if a team hasn’t built a mecanum drive… and wants to give it a try… you’ve gotta do it! I think mecanums are the most beautiful drive system to watch, and just love having seasoned engineers come into our shop and have a Grade 10 show them a wheel that they never knew existed!
</rambling>
Jason
FWIW, I recall a video on the Airtrax website a few years back that showed Mecanum wheels climbing stairs. The key is, as has already been pointed out, ensuring that you don’t high center, and that your rollers have enough friction to make it up (where “enough” depends very much on the dimensions of your wheel base).
LOL All of us gave poor Joe an earful and grounded him from CD!!! J/K!! We still love him, he is our super hero around here!!!