Mecanum drive on Einstein
 

Is this the year? Will we see a straight-up mecanum drive on Einstein?

Re: Mecanum drive on Einstein
 

Heck yes we will!

Re: Mecanum drive on Einstein
 

Yes

Re: Mecanum drive on Einstein
 

No. There will be no mecanum drive robots on Einstein this year.

Re: Mecanum drive on Einstein
 

This is certainly mecanum's best chance yet.

Re: Mecanum drive on Einstein
 

With a back-up robot and eight alliances on Einstein this year, I'd be shocked if at least one of the thirty-two robots doesn't have a mecanum drive.

Re: Mecanum drive on Einstein
 

I'd put it pretty close to 1 as far as probabilities go, especially since the lack of interactions between opposing alliances removes most team's hesitations with the drive...

Re: Mecanum drive on Einstein
 

Oh no. 254's going mecanum....

Re: Mecanum drive on Einstein
 

A constantly shifting CG might be a deterrent for some teams though

Re: Mecanum drive on Einstein
 

It's manageable.

Re: Mecanum drive on Einstein
 

No team has ever used Mecanum drive on Einstein before? That's kind of surprising to me.

Re: Mecanum drive on Einstein
 

While I doubt we will see the alliance captains and first picks with mecanum drives I think alliance captains will have to seriously consider mecanum robots for 2nd and 3rd picks out of necessity due to the smaller, watered down fields and the sheer popularity of mecanum drive this year.

Re: Mecanum drive on Einstein
 

Nope. No robot with a mecanum drive has ever made it to Einstein before. It's usually because of defense, and it you don't do them right, they have alot of issues on open fields. However, for a year like this, if you can get the balance right, you have a pretty good shot of being able to perform at a high level even with mecanum.

Re: Mecanum drive on Einstein
 

Why do you say that?

Re: Mecanum drive on Einstein
 

Agreed. I think some top robots this year will be mecanum.

Re: Mecanum drive on Einstein
 

Einstein is expanded to eight alliances which is 32 teams so chances are pretty good that one will have Mecanums.

Re: Mecanum drive on Einstein
 

Here's hoping since we're using mecanum this year

Re: Mecanum drive on Einstein
 

I think the issues with weight balance and integration (due to extra gearboxes) don't pose well for high ranking "do everything" robots. That's not to say it is impossible but I think many top tier teams will be turned off them for these reasons. Additionally most top tier teams have a preferred driver train that they are comfortable building and have practice driving.


IMO, I couldn't care less how little defense there is or how flat the field is. After thoroughly testing both a mecanum drive and a holonomic omni drive I think they handle terribly compared to a well built tank drive especially at a low speed. Driving sideways is just another nuisance our driver has to think about.

Re: Mecanum drive on Einstein
 

Or another skill for them to utilize. Depends on your driver.

Re: Mecanum drive on Einstein
 

It's a shame that this is likely the year that sacred ground will be touched by that unworthy drive :rolleyes:

Re: Mecanum drive on Einstein
 

Yep.

I might add that most teams who have the ability and disciple required to make it to Einstein would also have the ability to build a swerve drivetrain. It's overgeneralizing, sure, but I think it is mostly true.

Re: Mecanum drive on Einstein
 

I can't stand straight mecanum. On a drop drive that is different yes but straight mecanum is not something I am too happy with but when this game came out I immediately thought mecanum.
Of course then I heard a lot of people who know their bidnizz laugh at mecanum and it became a very hard pitch to my team.
I stand by it though.
As much as I am against mecanum because of its trade offs this year I feel it fits well.

Re: Mecanum drive on Einstein
 

Ability, yes. But is it worth the benefits to spend the extra time designing a swerve module when mecanum could work just as well or suit the time constraints better?

Re: Mecanum drive on Einstein
 

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

Re: Mecanum drive on Einstein
 

I can tell you 2 people that love mecanum drive. Andy Baker and Tony Norman.

Re: Mecanum drive on Einstein
 

One thing for sure: at the end of this season, either mec will be redeemed or it will be completely dead. If it doesn't happen this year, it won't ever happen. This game was nearly built for mec.

I'm actually more interested in whether 254 stands by their long precedent of swerve being unnecessary.

Re: Mecanum drive on Einstein
 

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

Re: Mecanum drive on Einstein
 

What is your reasoning on that?

Re: Mecanum drive on Einstein
 

I guess we differ in opinion there. I think that mecanum will absolutely not work just as well as swerve. It might suit the time constraints better, but concerns of center of gravity, and all four wheel needing to touch the floor at all times makes mecanum very unsuited for this game. I think mecanum does offer plenty of advantages over tank drive this year that are usually made moot by other mecanum drawbacks.

Re: Mecanum drive on Einstein
 

While some teams do very well with mechs. When push comes to shove Mike mechs do neither. The reason why most feel mechs have a chance this year is the lack of contact.

Re: Mecanum drive on Einstein
 

I imagine we will see some teams with mecanum excel and other fall flat. Pretty much the same as every year. Mecanum won't be completely dead after one season though, especially after a game that is such a radical departure from other FIRST games.

Re: Mecanum drive on Einstein
 

Its weird cause I hear arguments every year against mecanum but I never hear arguments that completely level them. Its just they get blown off for being mecanum

Re: Mecanum drive on Einstein
 

Pretty much. I usually ignore mecanum information in general unless it comes from Ether or a team that has used it well.

Re: Mecanum drive on Einstein
 

That is becuase there is no argument to level them. The thing about mecanum drive is that it s more or less treated as a novelty drive by most other teams (In my opinion). While mecanum may be conceptually easy mechanically, to perfect it a team needs a strong programing team to predict the exact vector of the robot one the fly. At the same time they must make it intuitive to drive. Even after the robot is done and programed you need driver training to perfect to use of this new found strafing ability. This is a large comitment for a team. Many teams like the idea of mecanum and try it with out putting the proper time or training in. This may be a reason why mecanum is so controversial. Just like any drive train a team should practice on the off season first.

It certainly has its share of pros. Most of all is the extra axis of moment which if used correctly can be used to avoid being pushed.

Re: Mecanum drive on Einstein
 

In prior years (2011 through 2014) when I was a student on our team, we had a modest reputation as having some really awesome pushing power, especially in 2013 and 2014. We ran a six wheel tank drive, and I can;t recall us ever not being able to push someone out of our way. The difference is that mecanums got pushed way easier. That being said, this year, mecanums will not be pushed around as much, so that drawback isn't present. I am of the opinion that a tank drive robot, when well done, is the ideal drive for almost every situation, and the shifting cg of this years task will make mecanums quite tricky. As much as you could use mecanum, you're probably better off spending time doing a kitbot on steroids type of base, or a custom tank drive.

Re: Mecanum drive on Einstein
 

I think a lot of people react so strongly because of bad experiences with mecanum robots. Maybe they built one that turned out to be way more difficult that they thought, or didn't work, or found that they were totally shut down by defense, or found that they couldn't/weren't using it's strafing effectively, etc.
Also, even if they have never built one, they probably have been allied with one that let them down. 2014 especially had many mecanum bots that could not dish out or take defense. Whether or not it was due to inexperienced drivers/improper implementation/poor tuning is hard to tell, so generally the drivetrain concept gets blamed.
All it takes is one bad experience to sour an idea.
Obviously, the strafing ability is very valuable. That's why we saw the emergence of Butterfly drives, more teams talking about swerves, etc.
Watching 3 Day robots makes me think more and more that your robot's ability to carefully position stacking objects will be the key feature for the game. The ability to strafe gives you one means of improving your control.
I think that this year will be the defining year for mecanums. If they don't excel this year, then they never will.

Re: Mecanum drive on Einstein
 

*I promised myself I'd stay away from the mecanum debate this year, but here goes*

And herein lies the issue with people's perception of mecanum -- there have been many teams that have done mecanum poorly. I think the reasoning for this is that it "looks easy." Teams are told what is possible and try to do it without understanding the programming/controls aspect, the physical parameters, or that any holonomic drive requires driver practice to actually be good at it.

I won't be arrogant enough to claim we've had the best implementation of mecanum, but we've done it 3 years now (once as an off season prototype), and have gotten pretty decent at it. Here are the things we do to make mecanum work well:

1. Closed loop speed control for each motor.
we attach encoders to the motor shaft directly, rather than the gearbox output. We find this gives us better, cleaner data. We do rigorous tuning of the PID to make sure we get the response we want. This guarantees the wheel is going as fast or slow as we want, rather than applying a voltage to the motors and hoping.
2. Implement a gyro for field oriented drive
the gyro allows us to know our angular position and allows our drivers to do "cool" moves like drive in a straight line while spinning. It also compensates for a wheel temporarily losing contact with the ground by doing whatever it takes to keep the robot oriented the way we want it.
3. Make an effort to keep all the wheels on the ground.
usually this is accomplished by having a frame that's not so rigid, the wheels are constrained to a single plane. Sometimes we'll actually have "shocks" on the wheels to make sure they contact the playing surface.
4. Driver practice
5. More driver practice
6. Even more driver practice


All that being said, we don't just do mecanum because we like it, we make a conscious decision each year based on what the game calls for and what we believe will work.

Re: Mecanum drive on Einstein
 

I have a secret to tell you. #4, 5 and 6 are not exclusive to any one type of drive. And it is very likely the average team that builds mecanum their first year does not build 2 robots, which puts them at a disadvantage to virtually every other 2+ year team that has an old robot with a similar drive.

Re: Mecanum drive on Einstein
 

Have you ever driven a well tuned field oriented mecanum drive? It's by far the easiest thing I have ever driven. It takes almost three seconds to get used to the "new found strafing ability," after which you literally just point and the robot goes where you want it to go. It's very intuitive.

We've also added "bearing buttons" that the driver can press so the robot can orient itself to a specific heading, even while the robot is translating.

People overestimate the difficulty of mecanum since so many teams do it poorly, but I've seen just as many poorly done skid steer/swerve/fun other drives.

Good mecanum drives are rare because mecanum wheels frankly don't make sense for most games, so the higher level teams often choose to pass on mecanum for something that meets their needs better (specifically more traction). This game is not one of those games.

For a good skid steer drive you need a strong programming team. That being said a poorly programmed skid steer drive will give you better performance than a poorly programmed mecanum drive, so it is up to every team to evaluate their resources. Mecanum is not a bad choice for every team.

Stop the h8in

Re: Mecanum drive on Einstein
 

In VEX they work really well and it is just a matter of getting the code to work. And as posted just above you need to drive, drive, drive.

With this game needing agility and not trying to push another robot 50' down field it makes sense to look at them.

I'd suggest that you get with your nearest FTC/VEX team and get them to build you a robot using these: 4" Mecanum Wheels.

If you don't have one of those then get this VEXIQ kit VEXIQ starter kit with controller and one of the Gyro sensors The VEXIQ motors have speed / rotation sensors built in so you can get all the info you need for the programming. You'll need some programming environment, there is C and Python systems.

For between $60 (local FTC/VEX) and $400 (your own VexIQ) you can build a test platform and do all the testing you want. I think you'll find that it's not that hard.

And it will help to slow down the "fear mongering" that goes around. It's really depressing to hear "we don't do mechanum since we know a roboteer on a team that knows another roboteer on a different team and they talked about doing Mecanum in 2001 and couldn't get it to work." Try a little engineering, Ether has done most of the hard work for you on the analysis.

Re: Mecanum drive on Einstein
 

Quick question:

Has anyone tested mecanums running over the noodles? Because that seriousy throws a wrench in the whole four-on-the-ground thing. I'm not saying it can't be done, it just might be an issue.

I know we drove over them with last year's drive (six-wheel tank) and had no problems driving over the noodles, although not undamaged.

Re: Mecanum drive on Einstein
 

Keep in mind that the two biggest reasons to use WCD (high fault tolerance and easy maintainence) have not changed with this game.

Re: Mecanum drive on Einstein
 

We dragged out our demo bot and tested that the second day of build season. With 6" Vexpro Mecanum wheels, running over both the standard noodle and some older more rigid noodles we had in the shop was pretty easy, although it did cause a considerable bump that might disturb an insufficiently stable stack during the noodle-crossing. There was some mild cosmetic damage to the noodle surface in some cases. The test robot was a low COG robot weighing a full 120 lbs plus battery and standard bumpers (and three frisbees).

Re: Mecanum drive on Einstein
 

Having done mecanum and then octocanum every year since Lunacy (I know, I know, boo, hiss, shall not be named and all that), I have to agree. Our octocanum drive made us an absolute beast on defense in Rebound Rumble, and one of the reasons why is because that even without field-oriented drive, the robot drives exactly like a first-person shooter--we'd use fast mecanum to get where we needed to go and then drop traction wheels to manhandle other robots.

Four encoders plus a gyro and bam, you're off and running--intuitive, simple control that most of your prospective drivers have been using for years without even knowing it. Without the gyro a human driver can compensate pretty easily for various levels of wonkiness, on the fly and without really thinking about it.

You need all four wheels on the ground if you're strafing. If you're not, mecanum drives darn close to a standard tank drive, and should have no problem whatsoever clearing the scoring platform. (We added a 'helper' wheel for ground clearance issues, but that's because of how we designed our chassis.)

My feelings in summary then are this: mecanum is mechanically easy to implement, lightweight, and is incredibly simple to drive, but requires more programming finesse than a drop-center etc etc.

Swerve seems like overkill to me this game.

Re: Mecanum drive on Einstein
 

I have not driven a finely refined mecanum drive how ever I would be open to the opportunity to have it change my mind.

Re: Mecanum drive on Einstein
 

I've generally felt like the biggest drawback with a mecanum drive is that robots with other drive systems can push you around quite easily - if they can catch you. The last few years, it's been fairly easy to shut down a "high scoring" mecanum drive with a defensive bot... However, that disadvantage is gone this year... There is certain amount of attraction to a mecanum system with the fantastic mobility it offers. I do believe that it is the ideal drive system for this year's game.

However, I do not believe that the advantage is so great that teams should spend a lot of extra time building one if they are not already familiar with it. We discussed the issue passionately on kick-off weekend and ultimately chose a tank drive. Why? We have not built a mecanum drive for years and, this year, during our off-season training, we focused on improving our abilities with various tank drive configurations and chose not to build a mecanum. Realizing the potential problems when building a system with which we had little-to-no experience, we decided to build what we knew would do well and that we could build easily. This has given us a lot more time to work on our manipulators... And, for us, we'll have have a better overall robot because of it.... Generally we build a 6-wheel tank system - powered with six CIMs (we like to push folks around). However, this year, we went with a four-wheel tank (less tippy as we go over the scoring platform) with omni wheels in the front - powered by four CIMs. The four CIMs might be overkill for this game, but we were not convinced that two would be adequate if we were to get into a tugging match at the step or if we were trying to carry 6 totes + a container while maintaining balance/stability - especially if we were to have to go onto a scoring platform.

However, teams that have built mecanum systems in the past and can build a good one quickly should do so. There seem to be quite a few teams going in that direction - so, I would be fairly surprised if we don't see on on Einstein.

Re: Mecanum drive on Einstein
 

While I think you are conceptually correct, every year we will see drivers treating mecanum drive like tank drive. They will stop to spin on the field, nearly always approach a game piece head on, generally orient themselves in the direction of travel for simple traversal of the field, etc. Mecanums benefits all lay in the type of driving that tank drive can't do. If you drive it like tank drive then you lose the benefits.

Re: Mecanum drive on Einstein
 

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.

There are a few interesting things that can be done with mecanum that I have yet to see taken advantage of completely.
Yeah weight distribution is a problem but with this years game if you managed to center all the weight those totes provide you would get much better performance out of a mecanum.
Hopefully today I can mess around today with a way to change the turning point on a mecanum to each side and corner of the mecanum. It shouldn't be too hard in concept but I don't program so it could be misery. Ill post some stuffs when I get done.
As for drive practice every course I make the students run on a mecanum I make them do it atleast four times each time with a different orientation. The ideal is eight for diagonals too but time is definitely against me.

Re: Mecanum drive on Einstein
 

Hahahahahahahahahahahahaha.

That was a good one.

Re: Mecanum drive on Einstein
 

The inverse kinematics for what you want to do is not difficult.

Say you want to pivot the bot clockwise around the right front wheel at 90 degrees per second (pi/2 radians per second).

The inverse kinematics for mecanum are:
...so you would need to command the following wheel speeds:

Re: Mecanum drive on Einstein
 

I wouldn't say it takes that much time to make a mecanum drive we had our first in 2010 built in a week. I loved driving that thing, I was shocked it could climb the bumps. Just make sure you put them on in order.:D

Re: Mecanum drive on Einstein
 

Probably a silly question but it's been mulling around my head long enough, I noticed that in order to handle field centric drive we're basically multiplying the input vector [fwd, str, omega] by a transformation matrix to rotate about the origin. What happens if we first apply a transform to go from the rotation point to the origin then apply our rotation transform, and then apply the transform back to the rotation point? Note, I flipped X and Y because I have a habit of specifying coordinates as Y is the FWD axis and X is the STR axis.

Translate from Rotation Point to Origin
[ [ 1 0 -Y]
[ 0 1 -X]
[ 0 0 1] ]

Rotation about Origin
[ [ cos(ø) -sin(ø) 0]
[ sin(ø) cos(ø) 0]
[ 0 0 1] ]

Translate back to Rotation Point
[ [ 1 0 Y]
[ 0 1 X]
[ 0 0 1] ]


Basically, is it valid to treat a drivetrain the same way I treat graphics on a screen?

Re: Mecanum drive on Einstein
 

I'm not sure this answers your question, but...

If the only commands accessible to the driver are field-centric, the aforementioned "pivot around the right front wheel" maneuver would be considerably more difficult: the driver would have to continuously vary the field-centric FWD and STR commands as the bot executes the maneuver and its field-orientation changes

With robot-centric commands, the FWD, STR, and omega commands would be constant.

Re: Mecanum drive on Einstein
 

^ This.

Correct me if I'm wrong, but isn't an absolutely crucial design consideration of running mecanum equal (or as near to as possible) weight distribution on each wheel? Now as you suggested teams could load totes near the center of the robot, but not everyone will want the added difficuly of loading/stacking totes this way.

It's because of this weight distribution problem that while many have cited this year as the year of mecanum, I immediately thought the opposite.


While I agree that many teams may dismiss macanum offhand as some someone suggested earlier on this thread, I'd be more than weary of selecting a mecanum robot that carries totes outside of its frame as an alliance partner.

Re: Mecanum drive on Einstein
 

I'm mostly curious if my logic for treating the input as a vector and transforming it like I would any other vector into a different coordinate space is semi valid. Field Centric/Robot Centric withstanding.

After a bit more thinking on it, I'm not sure it's quite valid because my inputs are in terms of velocity and my rotation point is in terms of position. Basically, units don't match up. I think it just looked like field centric was a simple affline transform because it's actually the derivative of the matrix (which would put it in terms of velocity instead of position).

Re: Mecanum drive on Einstein
 

I have a feeling we will see a 7 wheel mecanum swerve on einstein.

Re: Mecanum drive on Einstein
 

From actual experiments (do not take this as 125 is doing mecanum) it is entirely possible to compensate for a weird CoG using omni directional drives.

Re: Mecanum drive on Einstein
 

Also depressing to think that many teams are not interested in learning more about any drivetrain that can really engage students in some real world applied physics due to the fact that this drivetrain "will not be competitive at world championships"...


Also, the wonderful folks who put together the WPI library have done most of the hard work for you on the programming.

Re: Mecanum drive on Einstein
 

consider a mecanum drive robot with tote lift that holds the totes outside the frame. I will call "forward" the side of the robot where the totes are located. The robot has a CoG centered left/right, and the lift is designed where the added tote weight shifts the CoG forward only (not left/right). Let's say the driver has loaded up a stack of totes and the weight actually shifts such that the back wheels have zero traction (and not pay attention to the rocking/tipping of the robot forward/backward). There is no gyro feedback/control.

desired action: drive forward
actual result: ???

desired action: rotate
actual result: ???

desired action: strafe
actual result: ???

Note: the "???"s above are meant as "what do you think?", not "mecanum sucks so much, you have no idea what will happen in this case"

Re: Mecanum drive on Einstein
 

They do neither what?

Re: Mecanum drive on Einstein
 

Oh engineers. Can't even figure it out when someone turns a clever phrase. He meant they can neither push nor shove.

Re: Mecanum drive on Einstein
 

I definitely got that but I thought he forgot to type something because in my previous post I asked him why he didn't think there wouldn't be a competitive mecanum team this year.

Re: Mecanum drive on Einstein
 

Whether we run with it in competition or not, mecanum has been a fantastic tool for us this year in terms of inspiring students and the community. Yay mec!

Re: Mecanum drive on Einstein
 

I think he was confused as to why someone would state a blatantly obvious fact and act as if it were clever.

Regardless, mecanum drive is horrible. You would need a game which is centered around virtually no alliance contact and great maneuverability around game pieces, tea mates, and obstacles. I can't imagine the gdc EVVVER making a game like that.


Oh wait...they did.

Re: Mecanum drive on Einstein
 

All the mecanum hate makes me sad. While I was on a team, we did mecs every year except Lunacy (obviously). What many people don't do with mecs is create a suspension for them. We never had traction issues with the suspension.

We also didn't have fancy field-oriented controls, but as the driver for 2.5 of the 3 years we did mecs, it didn't seem important. To me, it was still easy to drive once you grasped the concept of how it reacted to the controls.

To all the people saying "mecs suck cause they can't defense!!", isn't there a quote about the best defense being a killer offense or something? I can remember playing Rack 'n' Roll (oh god I'm old!) where another robot tried to keep us from scoring, so we just strafed around them when they thought they had us pinned.

Mecs don't work very well for the strategy of "push everyone out of my way so I can do what I want". You have to be a bit more clever about how you want to move and play the game. I think of different drives like kids in middle/high school. You've got the popular kids (WCD), the jocks (tank), theatre kids (omni, cause they're pretty and harmless), nerds (mecs), and then the couple of insanely smart ones (swerve). Just like surviving school, each type has a different strategy for being competitive in a game.

Anyhow, everyone's entitled to their own opinions on mecs and other drives, but please try to back up blanket opinions with facts ;)

Re: Mecanum drive on Einstein
 

If the back wheels have absolutely no traction, and the center of gravity is directly over the front wheels, then the robot is essentially a mecanum-wheeled Segway. Forward and backward will work as expected. Strafe and turn will act identically, doing a sideways arc with a radius that depends on roller friction -- more friction gives more turn, less friction gives more strafe.

Re: Mecanum drive on Einstein
 

Sketch showing approximate center of rotation for frictionless rollers

We messed around with PWMs to disable motors in a sloppy manner. Long story short when we disabled wheels on one side it moved the turning point to the midpoint between the two unpowered wheels. The implications I pulled away from this is that by adjusting the speeds on the motors we can move the turning point of the robot to anywhere within the frame. That being if you can change your turning point you can if pushed off center can roll out of any pim attempt.

Re: Mecanum drive on Einstein
 

...or outside the frame.

Re: Mecanum drive on Einstein
 

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

Re: Mecanum drive on Einstein
 

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

Re: Mecanum drive on Einstein
 

Weight, gearboxes, wider drivebase for clearing obstacles, maintenance, frame complexity, etc.

Lots of pros and cons for both drivebases.

Re: Mecanum drive on Einstein
 

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.)

Re: Mecanum drive on Einstein
 

Like this.

Re: Mecanum drive on Einstein
 

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

Re: Mecanum drive on Einstein
 

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

Re: Mecanum drive on Einstein
 

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.

Re: Mecanum drive on Einstein
 

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:

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.

Re: Mecanum drive on Einstein
 

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?

Re: Mecanum drive on Einstein
 

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.

Re: Mecanum drive on Einstein
 

QFT
(Quoted for Truth)

Re: Mecanum drive on Einstein
 

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.

Re: Mecanum drive on Einstein
 

About three weeks worth.

Re: Mecanum drive on Einstein
 

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.

Re: Mecanum drive on Einstein
 

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.

Re: Mecanum drive on Einstein
 

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

Re: Mecanum drive on Einstein
 

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.

Re: Mecanum drive on Einstein
 

Thanks for clarifying.

It happened! Team 20 is the one I recognized, but there are probably more.

Re: Mecanum drive on Einstein
 

3339, 20, and 1711 are all bringing them over from Carson