Chief Delphi - Mecanum drive on Einstein

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- General Forum (http://www.chiefdelphi.com/forums/forumdisplay.php?f=16)

- - Mecanum drive on Einstein (http://www.chiefdelphi.com/forums/showthread.php?t=133288)

Taylor

23-01-2015 13:12

Re: Mecanum drive on Einstein

Quote:

Originally Posted by pfreivald (Post 1432746)

Four gear boxes with four wheels and four motors is heavier and more complex than most other drive trains? (And I have no idea what you're on about with clearing obstacles needing a wider wheel base, or frame complexity. Mecanum wheels work fine on a standard frame.)

I believe he was listing pro-mecanum not pro-H-drive.

Tom Bottiglieri

23-01-2015 13:17

Re: Mecanum drive on Einstein

Quote:

Originally Posted by c.shu (Post 1432726)

Why do mecanum when you can just build an H-drive? :rolleyes:

Why build either when you can build something that doesn't move freely in all directions without closed loop control?

Monochron

23-01-2015 13:31

Re: Mecanum drive on Einstein

Quote:

Originally Posted by pfreivald (Post 1432205)

Except when you don't. You can drive it like a tank to get from point A to B, then use the omnidirectional capabilities to strafe/align with whatever objective you're going for.

Crossing the field omnidirectional capabilities don't matter, but when it comes to finer positioning they shine. So most of the time you'll be driving mecanum like a tank, and then using the added capability when and where you need it.

Yes, that was literally the point I was making. IFF you drive that way then you get the full benefits of mecanum. And if you are like many of the drivers who don't drive it that way, then you are wasting your time.

Foster

23-01-2015 14:13

Re: Mecanum drive on Einstein

Quote:

Originally Posted by Ether (Post 1432671)

...or outside the frame.

With that kind of versatility you can just move away from a pushing match, circling around the bully robot.

Inside the frame, outside the frame, just two wheels driving, is there nothing this magical drive train can't do :rolleyes:

xXhunter47Xx

23-01-2015 14:14

Re: Mecanum drive on Einstein

To be honest, the teams that make it to Einstein and want to have omni-directional movement will probably have a swerve drive.
Mecanums lack speed, and while speed isn't as important in this game it is still something to consider, if you want to make quick stacks.

lcoreyl

23-01-2015 14:27

Re: Mecanum drive on Einstein

Quote:

Originally Posted by xXhunter47Xx (Post 1432822)

Mecanums lack speed

Are you saying 2 robots with the same motors/gearboxes/wheel radius/etc, but one mecanum and one traction wheel, then given the same drive command mecanum will be slower?

pfreivald

23-01-2015 14:48

Re: Mecanum drive on Einstein

Quote:

Originally Posted by Tom Bottiglieri (Post 1432779)

Why build either when you can build something that doesn't move freely in all directions without closed loop control?

In our case it's because mecanum is much more resource light than swerve (cost, weight, and time), and we want the fine position control that omnidirectional drives can give.

It's not "the best" option, but it's the best for us at this time.

MechEng83

23-01-2015 15:08

Re: Mecanum drive on Einstein

Quote:

Originally Posted by pfreivald (Post 1432834)

It's not "the best" option, but it's the best for us at this time.

QFT
(Quoted for Truth)

asid61

23-01-2015 15:49

Re: Mecanum drive on Einstein

Quote:

Originally Posted by xXhunter47Xx (Post 1432822)

You need to use the search funtion. A mecanum drive will go as fast as a 6WD in a perfect world. In reality, efficiency will make the speeds different, but a macenum drive is not inherently slower.

Kristian Calhoun

23-01-2015 16:39

Re: Mecanum drive on Einstein

Quote:

Originally Posted by Gregor (Post 1431976)

Quote:

Originally Posted by nuggetsyl (Post 1431965)

I am not sure what's funnier. People still thinking Mech wheels actually are competitive or the fact that SOOOOOOOOOOOOOOOOOO many teams use them.

How much experience and testing do you have with a well tuned mecanum drivetrain?

About three weeks worth.

xXhunter47Xx

23-01-2015 18:35

Re: Mecanum drive on Einstein

Quote:

Originally Posted by asid61 (Post 1432884)

You need to use the search funtion. A mecanum drive will go as fast as a 6WD in a perfect world. In reality, efficiency will make the speeds different, but a macenum drive is not inherently slower.

Right, in a perfect world. That really isn't my point I was trying to make, my point was that swerve is probably going to be more common. This is all speculation anyways.

MrJohnston

23-01-2015 18:47

Re: Mecanum drive on Einstein

Quote:

Originally Posted by xXhunter47Xx (Post 1432991)

Right, in a perfect world. That really isn't my point I was trying to make, my point was that swerve is probably going to be more common. This is all speculation anyways.

I'm not convinced... For various reasons, we're running a tank drive, but I see no reason why a mecanum drive can't be very effective this year... Sure, a swerve system is likely stronger, but does it really give that much of an advantage over mecanum in this game? In terms of maneuverability, I believe the driver is going to be far more important that whether you have mecanum or swerve....But there is another side...

Many different drive systems are going to be competitive -frankly, I think the drive train is going to be less important this year than most, simply because of the complete lack of robot-on-robot defense. It is going to be more about he capabilities of the different manipulators. If you choose mecanum over swerve, you will have more money and weight that you can dedicate to your manipulators... More importantly, perhaps, unless you are experienced with a swerve drive, you will also have a lot more time to perfect and practice with those same systems.

Sure, I do think a good swerve system is likely slightly better than a good mecanum system, but, for most teams, there are going to be too many trade-offs. We're running a tank drive with two omni wheels because we could build a very good one very quickly, leaving us a lot of time to perfect everything else. Were we experienced with mecanum, we would have gone that direction in a heartbeat.

Ether

24-01-2015 14:13

Re: Mecanum drive on Einstein

Quote:

Originally Posted by xXhunter47Xx (Post 1432822)

Mecanums lack speed...

Quote:

Originally Posted by lcoreyl (Post 1432825)

Are you saying 2 robots with the same motors/gearboxes/wheel radius/etc, but one mecanum and one traction wheel, then given the same drive command mecanum will be slower?

@xXhunter47Xx: If you are still following this thread, I'm wondering if you would clarify what you meant.

xXhunter47Xx

24-01-2015 15:06

Re: Mecanum drive on Einstein

Quote:

Originally Posted by Ether (Post 1433298)

@xXhunter47Xx: If you are still following this thread, I'm wondering if you would clarify what you meant.

Sure, what I meant was (I'm probably wrong but this is a place to discuss) if you have to same setup on two different frames, but one has mecanum wheels and one has traction wheels, and both are going to get the same amount of control input, the mecanum is more likely to slip and lose traction.

When it slips and loses traction, the wheels will spin faster than the robot moves.

Again, I may be wrong.

Ether

24-01-2015 15:11

Re: Mecanum drive on Einstein

Quote:

Originally Posted by xXhunter47Xx (Post 1433331)

...the mecanum is more likely to slip and lose traction. When it slips and loses traction, the wheels will spin faster than the robot moves.

Thanks for clarifying.

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